Polyamide-imide polymer as well as preparation method and application thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to a polyamide-imide polymer as well as a preparation method and application thereof. The polyamideimide film is prepared from a polyamideimide polymer with a structure as shown in a formula I. The polyamideimide polymer takes 2, 2 '-bis (trifluoromethyl) diaminobiphenyl as a diamine monomer, takes 5, 5'-(1, 4-phenylene) bis [hexahydro-4, 7-methanol isobenzofuran-1, 3-diketone] as an anhydride monomer, and takes 2, 2 '-bis (trifluoromethyl) diaminobiphenyl as a diamine monomer and 5, 5'-(1, 4-phenylene) bis [hexahydro-4, 7-methanol isobenzofuran-1, 3-diketone] as an anhydride monomer. The preparation method comprises the following steps: copolymerizing the polyamideimide with terephthaloyl chloride in different proportions and 2, 2 '-bis (trifluoromethyl) diaminobiphenyl to prepare a polyamideimide polymer, and further preparing the polyamideimide film. The PAI thin film prepared by the method has relatively high visible light transmittance, relatively low thermal expansion coefficient and mechanical property, has good solubility in most organic solvents, is convenient to process and has a wide application prospect in the photoelectric field.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a polyamide-imide polymer, a preparation method and application thereof. Background Art

[0002] In recent years, in the field of modern optical electronics, the requirements for polymer optical films have been increasing. Compared with the fragility and heavy weight of traditional inorganic glass substrates, colorless and transparent polyimide (CPI) films as substrate materials have good heat resistance and dimensional stability under high temperature conditions, as well as good optical and mechanical properties. They are widely used in the manufacture of optoelectronic devices such as touch screens, flexible displays, and flexible printed circuit boards. The excellent performance of polyimide is mostly due to the strong charge transfer (CT) effect between dianhydride and diamine monomers, which also makes polyimide strongly absorb visible light, making the color appear yellow to dark brown. Traditional polyimide films have greatly affected their use in the optoelectronic field due to color reasons. Therefore, improving the optical properties of polyimide films has become a hot issue now. In addition, in electronic devices, polymer substrates will experience significant thermal expansion / contraction at high temperatures, which will lead to serious problems such as misalignment of tiny components and adhesion failure. Therefore, it is also particularly important to improve the dimensional stability of polymers.

[0003] At present, the most direct way to improve dimensional stability is to reduce the thermal expansion coefficient, but it is difficult to obtain both excellent optical transmittance and low thermal expansion coefficient at the same time, that is, improving the thermal stability of the polymer often reduces the optical properties of the film. Therefore, obtaining a colorless and transparent polyimide film with a low thermal expansion coefficient and certain mechanical properties is still a research hotspot for those skilled in the art.

[0004] In summary, in the high-tech fields of microelectronics and optical electronics, it is an urgent need to improve traditional polyimide films, increase optical transmittance, reduce thermal expansion coefficient, and study and prepare colorless and transparent polyimide film products that are resistant to high temperature and high strength. Summary of the invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a polyamide-imide polymer, a preparation method and application thereof. The polyamide-imide film made from the polyamide-imide polymer provided by the present invention has good optical transmittance while maintaining a low thermal expansion coefficient and excellent mechanical properties.

[0006] The present invention provides a polyamide-imide polymer having a structure shown in Formula I;

[0007]

[0008] In formula I, x and y are both integers, 25≤x≤500, 50≤y≤750.

[0009] The present invention also provides a method for preparing a polyamide-imide polymer, comprising the following steps:

[0010] A) under a protective gas atmosphere, mixing 2,2'-bis(trifluoromethyl)diaminobenzenediamine monomer, a non-protonic polar solvent and 5,5'-(1,4-phenylene)bis[hexahydro-4,7-methanolisobenzofuran-1,3-dione] anhydride monomer to obtain a first mixed solution;

[0011] B) mixing the first mixed solution and terephthaloyl chloride in an ice water bath, and reacting at room temperature;

[0012] C) mixing the system after the reaction in step B), a dehydration catalyst and an imidization agent to carry out a chemical imidization reaction;

[0013] D) mixing the system after the reaction in step C) with a precipitant to precipitate, thereby obtaining a polyamide-imide polymer having a structure shown in formula I;

[0014]

[0015] In formula I, x and y are both integers, 25≤x≤500, 50≤y≤750.

[0016] Preferably, the molar ratio of 2,2'-bis(trifluoromethyl)diaminobenzidine monomer, 5,5'-(1,4-phenylene)bis[hexahydro-4,7-methanolisobenzofuran-1,3-dione] anhydride monomer and terephthaloyl chloride is 1:0.1 to 1:0 to 0.9; and the molar amount of terephthaloyl chloride is not 0.

[0017] Preferably, the aprotic polar solvent includes N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, m-cresol or dimethyl sulfoxide;

[0018] The protective gas is nitrogen.

[0019] Preferably, in step B), the reaction time is 10 to 14 hours.

[0020] Preferably, the dehydration catalyst includes at least one of acetic anhydride, propionic anhydride, benzoic anhydride and trifluoroacetic anhydride; the imidization agent includes at least one of pyridine, picoline, quinoline and isoquinoline;

[0021] The molar ratio of the dehydration catalyst, the imidization agent and the 5,5'-(1,4-phenylene)bis[hexahydro-4,7-methanolisobenzofuran-1,3-dione] anhydride monomer is 3-9:3-9:0.5-1.5.

[0022] Preferably, in step C), the temperature of the chemical imidization reaction is room temperature and the time is 10 to 14 hours.

[0023] Preferably, in step D), the precipitant comprises at least one of methanol, ethanol, isopropanol and water.

[0024] The present invention also provides a polyamide-imide film, which is prepared from the polyamide-imide polymer described above or the polyamide-imide polymer prepared by the preparation method described above.

[0025] The present invention also provides a method for preparing a polyamide-imide film, comprising the following steps:

[0026] The casting solution is evenly coated on the substrate, and after removing the solvent, the film is removed and dried to obtain a polyamide-imide film;

[0027] The casting solution is obtained by mixing a polyamide-imide polymer and a non-protonic polar solvent;

[0028] The polyamide-imide polymer is the polyamide-imide polymer described above or the polyamide-imide polymer prepared by the preparation method described above.

[0029] Preferably, the aprotic polar solvent includes N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, m-cresol or dimethyl sulfoxide;

[0030] The solid content of the casting solution is 5% to 20%;

[0031] The method for removing the solvent is to remove the solvent by heating;

[0032] The method of heating up comprises:

[0033] First raise the temperature to 50-80℃ and keep it for 6-8h, then raise the temperature to 100-120℃ and keep it for 1-2h, then raise the temperature to 150-170℃ and keep it for 1-2h, then raise the temperature to 200-220℃ and keep it for 1-2h, and finally raise the temperature to 250-270℃ and keep it for 1-2h.

[0034] The present invention uses a polyamideimide polymer having a structure shown in Formula I to prepare a polyamideimide film, wherein the polyamideimide polymer uses 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB) as a diamine monomer and 5,5'-(1,4-phenylene)bis[hexahydro-4,7-methanolisobenzofuran-1,3-dione] (BzDA) as an anhydride monomer, and is copolymerized with terephthaloyl chloride (TPC) and TFMB in different proportions to prepare a polyamideimide polymer (PAI), and then a polyamideimide film is prepared. The PAI film prepared by the present invention has a high visible light transmittance, with a transmittance of more than 85% at 400nm, and has excellent dimensional stability (the CTE value can be as low as 23ppm K -1 ) and mechanical properties, and has good solubility in most organic solvents, is easy to process, and has broad application prospects in the optoelectronic field. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is the H-NMR spectrum of the polyamide-imide polymer of Example 1 of the present invention;

[0036] Figure 2 The thermogravimetric curves of the polyamide-imide polymers of Examples 1 to 3 of the present invention;

[0037] Figure 3 is a dynamic thermomechanical analysis curve of the polyamide-imide polymer of Example 1 of the present invention;

[0038] Figure 4 This is a graph showing the optical transmittance performance in the visible light region of the polyamide-imide polymers of Examples 1 to 3 of the present invention. DETAILED DESCRIPTION

[0039] The technical solution of the present invention will be clearly and completely described below in conjunction with 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.

[0040] The present invention provides a polyamide-imide polymer having a structure shown in Formula I;

[0041]

[0042] In formula I, x and y are both integers, 25≤x≤500, 50≤y≤750.

[0043] In some embodiments of the present invention, the range of x is 25≤x≤250, 50≤x≤500 or 75≤x≤750.

[0044] In certain embodiments of the present invention, y is in the range of 75≤y≤750, 50≤y≤500 or 25≤y≤250.

[0045] In certain embodiments of the present invention, the weight average molecular weight of the polyamideimide polymer is 10,000-1,000,000; specifically, 50,000-575,000, such as 50,000-500,000, 55,000-550,000 or 57,500-575,000.

[0046] The present invention also provides a method for preparing the polyamide-imide polymer described above, comprising the following steps:

[0047] A) under a protective gas atmosphere, mixing 2,2'-bis(trifluoromethyl)diaminobenzenediamine monomer, a non-protonic polar solvent and 5,5'-(1,4-phenylene)bis[hexahydro-4,7-methanolisobenzofuran-1,3-dione] anhydride monomer to obtain a first mixed solution;

[0048] B) mixing the first mixed solution and terephthaloyl chloride in an ice water bath, and reacting at room temperature;

[0049] C) mixing the system after the reaction in step B), a dehydration catalyst and an imidization agent to carry out a chemical imidization reaction;

[0050] D) mixing the system after the reaction in step C) with a precipitant for precipitation to obtain a polyamide-imide polymer.

[0051] In step A):

[0052] Under a protective gas atmosphere, 2,2'-bis(trifluoromethyl)diaminobenzenediamine monomer, a non-protonic polar solvent and 5,5'-(1,4-phenylene)bis[hexahydro-4,7-methanolisobenzofuran-1,3-dione] anhydride monomer are mixed to obtain a first mixed solution.

[0053] Specifically, they include:

[0054] Under a protective gas atmosphere, 2,2'-bis(trifluoromethyl)diaminobenzenediamine monomer and 5,5'-(1,4-phenylene)bis[hexahydro-4,7-methanolisobenzofuran-1,3-dione] anhydride monomer are sequentially dissolved in a non-protonic polar solvent to obtain a first mixed solution.

[0055] In some embodiments of the present invention, the protective gas is nitrogen.

[0056] In certain embodiments of the present invention, the molar ratio of 2,2'-bis(trifluoromethyl)diaminobenzidine monomer to 5,5'-(1,4-phenylene)bis[hexahydro-4,7-methanolisobenzofuran-1,3-dione] anhydride monomer is 1:0.1-1, such as 1:0.25, 1:0.5 or 1:0.75.

[0057] In certain embodiments of the present invention, the aprotic polar solvent includes N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, m-cresol or dimethyl sulfoxide. The total amount of the 2,2'-bis(trifluoromethyl)diaminobenzenediamine monomer and the 5,5'-(1,4-phenylene)bis[hexahydro-4,7-methanolisobenzofuran-1,3-dione] anhydride monomer and the aprotic polar solvent are used in a ratio of 2 to 4 mmol: 3 to 5 mL, such as 2.5 mmol: 4 mL, 3 mmol: 4 mL or 3.5 mmol: 4 mL.

[0058] In certain embodiments of the present invention, the dissolving is performed at room temperature. The dissolving is performed under stirring.

[0059] In step B):

[0060] The first mixed solution and terephthaloyl chloride were mixed in an ice-water bath and reacted at room temperature.

[0061] Specifically, they include:

[0062] Terephthaloyl chloride was dissolved in the first mixed solution in an ice-water bath, and the reaction was carried out at room temperature.

[0063] In certain embodiments of the present invention, the molar ratio of 2,2'-bis(trifluoromethyl)diaminobenzidine monomer, 5,5'-(1,4-phenylene)bis[hexahydro-4,7-methanolisobenzofuran-1,3-dione] anhydride monomer and terephthaloyl chloride is 1:0.1 to 1:0 to 0.9, such as 1:0.25:0.75, 1:0.5:0.5 or 1:0.75:0.25; and the molar amount of terephthaloyl chloride is not 0.

[0064] In certain embodiments of the present invention, the dissolving is performed under stirring conditions.

[0065] In certain embodiments of the present invention, the reaction time is 10 to 14 hours, such as 12 hours. The reaction is carried out under stirring.

[0066] In step C):

[0067] The system after the reaction in step B), the dehydration catalyst and the imidization agent are mixed to carry out a chemical imidization reaction.

[0068] In certain embodiments of the present invention, the dehydration catalyst includes at least one of acetic anhydride, propionic anhydride, benzoic anhydride and trifluoroacetic anhydride; and the imidization agent includes at least one of pyridine, picoline, quinoline and isoquinoline.

[0069] The molar ratio of the dehydration catalyst, the imidization agent and the 5,5'-(1,4-phenylene)bis[hexahydro-4,7-methanolisobenzofuran-1,3-dione] anhydride monomer is 3-9:3-9:0.5-1.5; for example, 3:9:0.5, 6:6:1 or 9:3:1.5.

[0070] The chemical imidization reaction is carried out at room temperature for 10 to 14 hours, such as 12 hours. The chemical imidization reaction is carried out under stirring.

[0071] In step D):

[0072] The system after the reaction in step C) is mixed with a precipitant for precipitation to obtain a polyamide-imide polymer.

[0073] Specifically, they include:

[0074] The system after the reaction in step C) is slowly poured into a precipitant to perform precipitation, thereby obtaining a polyamide-imide polymer.

[0075] In certain embodiments of the present invention, the slow pouring rate is 0.005-0.02 mL / s, such as 0.01 mL / s.

[0076] In certain embodiments of the present invention, the precipitant comprises at least one of methanol, ethanol, isopropanol and water.

[0077] After precipitation, a white flocculent precipitate was obtained.

[0078] In certain embodiments of the present invention, after the precipitation, the method further comprises:

[0079] The precipitate was washed, filtered and dried.

[0080] The washing may be repeated stirring washing, specifically, repeated stirring washing three times.

[0081] The drying is vacuum drying, the temperature may be 120° C., and the time may be 8 to 12 hours.

[0082] The present invention also provides a polyamide-imide film, which is prepared from the polyamide-imide polymer described above or the polyamide-imide polymer prepared by the preparation method described above.

[0083] The present invention also provides a method for preparing the polyamide-imide film as described above, comprising the following steps:

[0084] The casting solution is evenly coated on the substrate, and after removing the solvent, the film is removed and dried to obtain a polyamide-imide film;

[0085] The casting solution is obtained by mixing a polyamide-imide polymer and a non-protonic polar solvent.

[0086] In certain embodiments of the present invention, the aprotic polar solvent includes N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, m-cresol or dimethyl sulfoxide.

[0087] In some embodiments of the present invention, the solid content of the casting solution is 5% to 20%, such as 5%.

[0088] The substrate may be a clean glass plate.

[0089] The present invention has no particular limitation on the coating method, and preferably adopts a casting method.

[0090] The method for removing the solvent may be to remove the solvent by heating it in a vacuum oven.

[0091] In certain embodiments of the present invention, the method of increasing the temperature comprises:

[0092] First raise the temperature to 50-80℃ and keep it for 6-8h, then raise the temperature to 100-120℃ and keep it for 1-2h, then raise the temperature to 150-170℃ and keep it for 1-2h, then raise the temperature to 200-220℃ and keep it for 1-2h, and finally raise the temperature to 250-270℃ and keep it for 1-2h.

[0093] After removing the solvent, the method further comprises: cooling to room temperature.

[0094] Before stripping and drying, the method further includes: immersing the substrate in water.

[0095] The obtained polyamide-imide film is a colorless and transparent polyamide-imide film.

[0096] The present invention has no particular limitation on the sources of the raw materials used above, and they can be generally commercially available.

[0097] Beneficial effects:

[0098] (1) The polyamide-imide film prepared by the present invention uses a fluorine-containing diamine monomer. The introduction of the fluorine-containing group increases the molecular chain spacing, reduces the intermolecular force, increases the free volume of the polymer, and the fluorine atom can destroy the regularity of the molecular chain and increase the flexibility of the molecular chain, thereby greatly improving the solubility of the polyamide-imide, and can be dissolved in N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, meta-cresol or dimethyl sulfoxide, thereby improving the processing performance of the product. In addition, the fluorine atom has a strong electronegativity and can inhibit the formation of a charge transfer complex (CTC), thereby improving the optical transmittance of the film and reducing the yellowness value of the film. The visible light transmittance is about 85% to 90%.

[0099] (2) The polyamide-imide film prepared by the present invention adopts anhydride monomers with alicyclic structures. The introduction of alicyclic structures can destroy the conjugated structure on the original aromatic polyimide chain segments, reduce the intermolecular forces, thereby inhibiting the formation of CTC, improving the optical transmittance of the film, and at the same time increasing the molecular chain spacing, which is also helpful to improve the solubility of polyamide-imide.

[0100] (3) The polyamide-imide film prepared by the present invention uses terephthaloyl chloride as a comonomer. Since the main chain formed by the polymerization of terephthaloyl chloride and diamine monomers is a rigid straight chain linear structure and contains an amide structure, the polyamide-imide film has high heat resistance, a glass transition temperature of 350 to 370°C, and a low thermal expansion coefficient, with a CTE value as low as 23ppm K. -1 Therefore, the soluble colorless, transparent, low thermal expansion coefficient polyamide-imide film prepared by the present invention has excellent comprehensive properties and has good application prospects in high-tech fields such as microelectronics and optical electronics.

[0101] In order to further illustrate the present invention, a polyamide-imide polymer, a preparation method and application thereof provided by the present invention are described in detail below in conjunction with embodiments, but it should not be construed as limiting the scope of protection of the present invention.

[0102] Comparative Example 1

[0103] The polyamide-imide polymer has the structure shown in formula (1);

[0104]

[0105] In formula (1), n ​​is an integer, 50≤n≤500; the weight average molecular weight of the polyamideimide polymer represented by formula (1) is 30,000 to 300,000.

[0106] 1) Preparation of polyamide-imide polymer having the structure shown in formula (1):

[0107] 1-1) Under a nitrogen atmosphere, 2,2'-bis(trifluoromethyl)diaminobenzidine monomer (0.6405 g, 2 mmol) and 5,5'-(1,4-phenylene)bis[hexahydro-4,7-methanolisobenzofuran-1,3-dione] anhydride monomer (0.8129 g, 2 mmol) were sequentially dissolved in 4 mL of N,N-dimethylacetamide under stirring at room temperature to obtain a first mixed solution;

[0108] 1-2) mixing the first mixed solution, acetic anhydride (1.2251 g, 12 mmol) and pyridine (0.9492 g, 12 mmol), and performing a chemical imidization reaction at room temperature for 12 h; the chemical imidization reaction is performed under stirring;

[0109] 1-3) The system after the reaction in step 1-2) was slowly poured into ethanol (300 mL) at a rate of 0.01 mL / s to precipitate to obtain a white flocculent precipitate, which was repeatedly stirred and washed three times, filtered, and vacuum dried at 120° C. for 10 h to obtain a polyamide-imide polymer having a structure shown in formula (1).

[0110] 2) Preparation of polyamide-imide film:

[0111] The polyamide-imide polymer of the structure shown in formula (1) is uniformly dissolved in N,N-dimethylacetamide to prepare a casting solution with a solid content of 5%. The casting solution is uniformly coated on a clean glass plate by a casting method, and the solvent is removed in a vacuum oven according to the following program: 80°C / 6h, 100°C / 1h, 150°C / 1h, 200°C / 1h, 250°C / 1h. After cooling to room temperature, the glass plate is immersed in water, the film is removed and dried to obtain a polyamide-imide film with a thickness of 30μm.

[0112] Example 1

[0113] The polyamideimide polymer has the structure shown in Formula I;

[0114] Wherein, x and y are both integers, 25≤x≤250, 75≤y≤750; and the weight average molecular weight of the polyamideimide polymer is 50,000 to 500,000.

[0115] 1) Preparation of the polyamide-imide polymer:

[0116] 1-1) Under a nitrogen atmosphere, 2,2'-bis(trifluoromethyl)diaminobenzidine monomer (0.6405 g, 2 mmol) and 5,5'-(1,4-phenylene)bis[hexahydro-4,7-methanolisobenzofuran-1,3-dione] anhydride monomer (0.2032 g, 0.5 mmol) were sequentially dissolved in 4 mL of N,N-dimethylacetamide under stirring at room temperature to obtain a first mixed solution;

[0117] 1-2) dissolving terephthaloyl chloride (0.3045 g, 1.5 mmol) in the first mixed solution in an ice-water bath, and stirring the reaction at room temperature for 12 h;

[0118] 1-3) mixing the system after the reaction in step 1-2), acetic anhydride (0.3063 g, 3 mmol) and pyridine (0.7119 g, 9 mmol), and performing a chemical imidization reaction at room temperature for 12 h; the chemical imidization reaction is performed under stirring;

[0119] 1-4) The system after the reaction in step 1-3) is poured into ethanol (300 mL) at a rate of 0.01 mL / s to precipitate to obtain a white flocculent precipitate, which is repeatedly stirred and washed three times, filtered, and vacuum dried at 120° C. for 10 h to obtain a polyamide-imide polymer having a structure shown in formula (2).

[0120] Figure 1 This is the H-NMR spectrum of the polyamide-imide polymer of Example 1 of the present invention.

[0121] Figure 2 The thermogravimetric curves of the polyamide-imide polymers of Examples 1 to 3 of the present invention are shown in FIG. Figure 2 It can be seen that as the content of terephthaloyl chloride decreases, the thermal decomposition temperature of the polyamide-imide polymer becomes lower and lower.

[0122] Figure 3 The dynamic thermomechanical analysis curve of the polyamide-imide polymer of Example 1 of the present invention is shown in FIG. Figure 3 It can be seen that the glass transition temperature of the polyamide-imide polymer prepared in the present invention is relatively high, which can reach 367°C.

[0123] Figure 4 The optical transmittance performance diagram of the polyamide-imide polymers in the visible light region of Examples 1 to 3 of the present invention is shown in FIG. Figure 4 It can be seen that with the increase of the content of 5,5'-(1,4-phenylene)bis[hexahydro-4,7-methanolisobenzofuran-1,3-dione] anhydride monomer, the transmittance of the polyamide-imide polymer at 400 nm becomes higher and higher.

[0124] 2) Preparation of polyamide-imide film:

[0125] The polyamide-imide polymer of the structure shown in formula (2) is uniformly dissolved in N, N-dimethylacetamide to prepare a casting solution with a solid content of 5%. The casting solution is uniformly coated on a clean glass plate by a casting method, and the solvent is removed in a vacuum oven according to the following program: 80°C / 6h, 100°C / 1h, 150°C / 1h, 200°C / 1h, 250°C / 1h. After cooling to room temperature, the glass plate is immersed in water, the film is removed and dried to obtain a polyamide-imide film with a thickness of 30μm.

[0126] Example 2

[0127] The polyamideimide polymer has the structure shown in Formula I;

[0128] Wherein, x and y are both integers, 50≤x≤500, 50≤y≤500; and the weight average molecular weight of the polyamideimide polymer is 55,000 to 550,000.

[0129] 1) Preparation of the polyamide-imide polymer:

[0130] 1-1) Under a nitrogen atmosphere, 2,2'-bis(trifluoromethyl)diaminobenzidine monomer (0.6405 g, 2 mmol) and 5,5'-(1,4-phenylene)bis[hexahydro-4,7-methanolisobenzofuran-1,3-dione] anhydride monomer (0.4064 g, 1 mmol) were sequentially dissolved in 4 mL of N,N-dimethylacetamide under stirring at room temperature to obtain a first mixed solution;

[0131] 1-2) dissolving terephthaloyl chloride (0.2030 g, 1 mmol) in the first mixed solution in an ice-water bath, and stirring the reaction at room temperature for 12 h;

[0132] 1-3) mixing the system after the reaction in step 1-2), acetic anhydride (0.6126 g, 6 mmol) and pyridine (0.4746 g, 6 mmol), and performing a chemical imidization reaction at room temperature for 12 h; the chemical imidization reaction is performed under stirring;

[0133] 1-4) The system after the reaction in step 1-3) is poured into ethanol (300 mL) at a rate of 0.01 mL / s to precipitate to obtain a white flocculent precipitate, which is repeatedly stirred and washed three times, filtered, and vacuum dried at 120° C. for 10 h to obtain a polyamide-imide polymer having a structure shown in formula (3).

[0134] 2) Preparation of polyamide-imide film:

[0135] The polyamide-imide polymer of the structure shown in formula (3) was uniformly dissolved in N, N-dimethylacetamide to prepare a casting solution with a solid content of 5%. The casting solution was uniformly coated on a clean glass plate by a casting method, and the solvent was removed in a vacuum oven according to the following program: 80°C / 6h, 100°C / 1h, 150°C / 1h, 200°C / 1h, 250°C / 1h. After cooling to room temperature, the glass plate was immersed in water, the film was removed and dried to obtain a polyamide-imide film with a thickness of 30μm.

[0136] Example 3

[0137] The polyamideimide polymer has the structure shown in Formula I;

[0138] Wherein, x and y are both integers, 75≤x≤750, 25≤y≤250; and the weight average molecular weight of the polyamideimide polymer is 57500-575000.

[0139] 1) Preparation of the polyamide-imide polymer:

[0140] 1-1) Under a nitrogen atmosphere, 2,2'-bis(trifluoromethyl)diaminobenzidine monomer (0.6405 g, 2 mmol) and 5,5'-(1,4-phenylene)bis[hexahydro-4,7-methanolisobenzofuran-1,3-dione] anhydride monomer (0.6096 g, 1.5 mmol) were sequentially dissolved in 4 mL of N,N-dimethylacetamide under stirring at room temperature to obtain a first mixed solution;

[0141] 1-2) dissolving terephthaloyl chloride (0.1015 g, 0.5 mmol) in the first mixed solution in an ice-water bath, and stirring the reaction at room temperature for 12 h;

[0142] 1-3) mixing the system after the reaction in step 1-2), acetic anhydride (0.9189 g, 9 mmol) and pyridine (0.2373 g, 3 mmol), and performing a chemical imidization reaction at room temperature for 12 h; the chemical imidization reaction is performed under stirring;

[0143] 1-4) The system after the reaction in step 1-3) is poured into ethanol (300 mL) at a rate of 0.01 mL / s to precipitate to obtain a white flocculent precipitate, which is repeatedly stirred and washed three times, filtered, and vacuum dried at 120° C. for 10 h to obtain a polyamide-imide polymer having a structure shown in formula (4).

[0144] 2) Preparation of polyamide-imide film:

[0145] The polyamide-imide polymer of the structure shown in formula (4) was uniformly dissolved in N, N-dimethylacetamide to prepare a casting solution with a solid content of 5%. The casting solution was uniformly coated on a clean glass plate by a casting method, and the solvent was removed in a vacuum oven according to the following program: 80°C / 6h, 100°C / 1h, 150°C / 1h, 200°C / 1h, 250°C / 1h. After cooling to room temperature, the glass plate was immersed in water, the film was removed and dried to obtain a polyamide-imide film with a thickness of 30μm.

[0146] Comparative Example 2

[0147] The polyamide-imide polymer has the structure shown in formula (2);

[0148]

[0149] In formula (2), n is an integer, 50≤n≤500; the weight average molecular weight of the polyamideimide polymer is 25000 to 250000.

[0150] 1) Preparation of the polyamide-imide polymer:

[0151] 1-1) Under a nitrogen atmosphere, 2,2'-bis(trifluoromethyl)diaminobenzidine monomer (0.6405 g, 2 mmol) was dissolved in 4 mL of N,N-dimethylacetamide under stirring at room temperature to obtain a first mixed solution;

[0152] 1-2) dissolving terephthaloyl chloride (0.4060 g, 2 mmol) in the first mixed solution in an ice-water bath, and stirring the reaction at room temperature for 12 h;

[0153] 1-3) mixing the system after the reaction in step 1-2), acetic anhydride (1.2252 g, 12 mmol) and pyridine (0.9492 g, 12 mmol), and performing a chemical imidization reaction at room temperature for 12 h; the chemical imidization reaction is performed under stirring;

[0154] 1-4) The system after the reaction in step 1-3) was poured into ethanol (300 mL) at a rate of 0.01 mL / s to precipitate to obtain a white flocculent precipitate, which was repeatedly stirred and washed three times, filtered, and vacuum dried at 120° C. for 10 h to obtain a polyamide-imide polymer having a structure shown in formula (5).

[0155] 2) Preparation of polyamide-imide film:

[0156] The polyamide-imide polymer of the structure shown in formula (5) was uniformly dissolved in N, N-dimethylacetamide to prepare a casting solution with a solid content of 5%. The casting solution was uniformly coated on a clean glass plate by a casting method, and the solvent was removed in a vacuum oven according to the following program: 80°C / 6h, 100°C / 1h, 150°C / 1h, 200°C / 1h, 250°C / 1h. After cooling to room temperature, the glass plate was immersed in water, the film was removed and dried to obtain a polyamide-imide film with a thickness of 30μm.

[0157] The optical properties, heat resistance and mechanical properties of the polyamide-imide films obtained in Comparative Examples 1 to 2 and Examples 1 to 3 were tested. The results are shown in Table 1.

[0158] Table 1 Performance test results of polyamide-imide films obtained in Comparative Examples 1-2 and Examples 1-3

[0159]

[0160] As can be seen from Table 1, the colorless and transparent polyamide-imide film prepared by the present invention has good heat resistance and optical properties; specifically, the glass transition temperature Tg of the film is between 350 and 370°C, the transmittance at 400nm is above 85%, the cut-off wavelength λcut-off is below 355nm, and the yellowness value is maintained between 1.7 and 1.85, and the thermal expansion coefficient CTE value can reach a minimum of 23ppm K -1 .

[0161] Compared with Comparative Example 1, the heat resistance, glass transition temperature, dimensional stability and mechanical properties of the colorless and transparent polyamide-imide film prepared in Examples 1 to 3 are significantly improved, proving that after the introduction of terephthaloyl chloride monomer, the rigidity of the polyamide-imide film prepared by the present invention gradually increases with the increase of terephthaloyl chloride content, the mechanical properties are also improved, and the thermal expansion coefficient of the film is greatly reduced, and the CTE value is significantly reduced. In addition, it can be seen from Comparative Example 2 and Examples 1 to 3 that the optical properties of the film prepared by polymerization using 5,5'-(1,4-phenylene)bis[hexahydro-4,7-methanolisobenzofuran-1,3-dione] alicyclic structure anhydride monomer are significantly improved, proving that the introduction of alicyclic structure can destroy the conjugated structure on the original aromatic polyimide segment, reduce the intermolecular force, thereby inhibiting the formation of CTC and improving the optical transmittance of the film.

[0162] The solubility test was performed on the polyamide-imide films obtained in Comparative Examples 1-2 and Examples 1-3. The results are shown in Table 2.

[0163] Table 2 Solubility test results of polyamide-imide films obtained in Comparative Examples 1-2 and Examples 1-3

[0164] m-Cresol DMAc NMP DMF <![CDATA[CHCl3]]> Comparative Example 1 + + + + - Example 1 + + + + - Example 2 + + + + - Example 3 + + + + - Comparative Example 2 + + + + -

[0165] It can be seen from Table 2 that the colorless and transparent polyamide-imide film prepared in the present invention has good solubility, can be dissolved in most aprotic polar organic solvents, and has good processability.

[0166] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A polyamide-imide polymer having a structure as shown in Formula I; In formula I, x and y are both integers, 25≤x≤500, 50≤y≤750.

2. A method for preparing a polyamide-imide polymer, comprising the following steps: A) under a protective gas atmosphere, mixing 2,2'-bis(trifluoromethyl)diaminobenzenediamine monomer, a non-protonic polar solvent and 5,5'-(1,4-phenylene)bis[hexahydro-4,7-methanolisobenzofuran-1,3-dione] anhydride monomer to obtain a first mixed solution; B) mixing the first mixed solution and terephthaloyl chloride in an ice water bath, and reacting at room temperature; C) mixing the system after the reaction in step B), a dehydration catalyst and an imidization agent to carry out a chemical imidization reaction; D) mixing the system after the reaction in step C) with a precipitant to precipitate, thereby obtaining a polyamide-imide polymer having a structure shown in formula I; In formula I, x and y are both integers, 25≤x≤500, 50≤y≤750.

3. The preparation method according to claim 2, characterized in that: The molar ratio of 2,2'-bis(trifluoromethyl)diaminobenzidine monomer, 5,5'-(1,4-phenylene)bis[hexahydro-4,7-methanolisobenzofuran-1,3-dione] anhydride monomer and terephthaloyl chloride is 1:0.1 to 1:0 to 0.9; and the molar amount of terephthaloyl chloride is not 0.

4. The preparation method according to claim 2, characterized in that: The aprotic polar solvent includes N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, m-cresol or dimethyl sulfoxide; The protective gas is nitrogen.

5. The preparation method according to claim 2, characterized in that: In step B), the reaction time is 10 to 14 hours.

6. The preparation method according to claim 2, characterized in that: The dehydration catalyst includes at least one of acetic anhydride, propionic anhydride, benzoic anhydride and trifluoroacetic anhydride; the imidization agent includes at least one of pyridine, picoline, quinoline and isoquinoline; The molar ratio of the dehydration catalyst, the imidization agent and the 5,5'-(1,4-phenylene)bis[hexahydro-4,7-methanolisobenzofuran-1,3-dione] anhydride monomer is 3-9:3-9:0.5-1.

5.

7. The preparation method according to claim 2, characterized in that: In step C), the temperature of the chemical imidization reaction is room temperature and the time is 10 to 14 hours.

8. The preparation method according to claim 2, characterized in that: In step D), the precipitant comprises at least one of methanol, ethanol, isopropanol and water.

9. A polyamideimide film, wherein the polyamideimide film is prepared from the polyamideimide polymer according to claim 1 or the polyamideimide polymer prepared by the preparation method according to any one of claims 2 to 8.

10. A method for preparing a polyamide-imide film, comprising the following steps: The casting solution is evenly coated on the substrate, and after removing the solvent, the film is removed and dried to obtain a polyamide-imide film; The casting solution is obtained by mixing a polyamide-imide polymer and a non-protonic polar solvent; The polyamideimide polymer is the polyamideimide polymer according to claim 1 or the polyamideimide polymer prepared by the preparation method according to any one of claims 2 to 8.

11. The preparation method according to claim 10, characterized in that: The aprotic polar solvent includes N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, m-cresol or dimethyl sulfoxide; The solid content of the casting solution is 5% to 20%; The method for removing the solvent is to remove the solvent by heating; The method of heating up comprises: First raise the temperature to 50-80℃ and keep it for 6-8h, then raise the temperature to 100-120℃ and keep it for 1-2h, then raise the temperature to 150-170℃ and keep it for 1-2h, then raise the temperature to 200-220℃ and keep it for 1-2h, and finally raise the temperature to 250-270℃ and keep it for 1-2h.

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