Polyamic acid resin solution containing fluorenyl structure, film and preparation method thereof

Abstract

The invention belongs to the technical field of polyimide films, and particularly relates to a fluorenyl structure-containing polyamide acid resin solution, a fluorenyl structure-containing polyamide acid resin film and a preparation method thereof. The polyimide resin is formed by polymerizing dianhydride and diamine which are equal in mole in a strong-polarity aprotic organic solvent, and the dianhydride is formed by mixing 9, 9-bis (3, 4-dicarboxyphenyl) fluorene dianhydride and other dianhydride according to the mole ratio of 1: (3-9); the diamine is formed by mixing diamine containing maleamic acid side groups and other diamines in a molar ratio of 1: (8-9); the polyimide film prepared from the polyimide film has high elasticity modulus, excellent tensile strength and temperature resistance while ensuring transparency, can be applied to high-tech fields such as space telescopes, flexible solar cells, transparent glass protective films and liquid crystal alignment films, and has good potential market and application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of polyimide films, and in particular relates to a polyamic acid resin solution and film containing a fluorene group structure and a preparation method thereof. Background Art

[0002] With the rapid development of flexible display technology, its importance in the field of flat panel displays has become increasingly prominent. Traditional inorganic transparent glass substrates are difficult to meet the requirements of flexible electronic devices for lightweight and deformable substrates due to defects such as heavy weight, high brittleness, and difficulty in bending. Although transparent flexible polymer materials such as polyethylene terephthalate (PET) have a certain degree of flexibility, their heat resistance is insufficient (usually below 300°C) and they cannot adapt to high-temperature processing technology, which seriously limits their application in flexible display substrates. Therefore, the development of new flexible substrate materials with excellent heat resistance, high transparency, good mechanical properties and processing adaptability has become a technical problem that the industry urgently needs to solve.

[0003] Colorless and transparent polyimide (CPI) films have good optical properties, mechanical properties and thermal stability, and can meet the stringent requirements of high-end applications such as flexible organic light-emitting diodes (OLEDs) and integrated intelligent systems for material optical properties, bending resistance and high-temperature processing compatibility. However, the preparation process of existing polyimide films is complex and costly, and some products have problems such as insufficient transparency or poor mechanical properties, which limits their application. Therefore, the development of a colorless and transparent polyimide resin and film preparation method with simple process, controllable cost and excellent performance is of great significance to promote the industrialization of flexible display technology. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a polyamic acid resin solution containing a fluorene-based structure. The polyimide film prepared by the solution has high elastic modulus, excellent tensile strength and temperature resistance while ensuring transparency. It can be applied to high-tech fields such as space telescopes, flexible solar cells, transparent glass protective films, liquid crystal orientation films, etc., and has good potential market and application prospects.

[0005] Another object of the present invention is to provide a polyimide film and a method for preparing the same.

[0006] The technical solution adopted by the present invention is as follows:

[0007] The polyamic acid resin solution containing a fluorene group structure is polymerized by equimolar amounts of dianhydride and diamine in a highly polar aprotic organic solvent, wherein the dianhydride is a mixture of 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride and other dianhydrides in a molar ratio of 1:(3-9); the diamine is a mixture of a diamine containing a maleamic acid side group and other diamines in a molar ratio of 1:(8-9);

[0008] The method for preparing the diamine containing maleamic acid side groups comprises the following steps:

[0009] (1) dissolving bisphenol AF and 2,4-dinitrochlorobenzene in N,N-dimethylformamide, then adding anhydrous potassium carbonate and toluene, heating and refluxing to react, and after the reaction is completed, filtering and vacuum distilling are performed in sequence to obtain a rotary evaporation liquid, adding ethanol to the rotary evaporation liquid, and performing crystallization, washing and drying to obtain 2,2-bis[4-(2,4-dinitrophenoxy)phenyl]hexafluoropropane;

[0010] (2) adding a palladium-carbon catalyst to 2,2-bis[4-(2,4-dinitrophenoxy)phenyl]hexafluoropropane, introducing hydrogen gas to carry out a hydrogenation reduction reaction, and obtaining 2,2-bis[4-(2,4-diaminophenoxy)phenyl]hexafluoropropane;

[0011] (3) Dissolving 2,2-bis[4-(2,4-diaminophenoxy)phenyl]hexafluoropropane and maleic anhydride in a strongly polar aprotic organic solvent, stirring and reacting, thereby preparing a diamine containing a maleamic acid side group.

[0012] The other dianhydride is selected from at least one of 2,2-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride (CAS: 1107-00-2), 3,3',4,4'-tetracarboxylic diphenyl ether dianhydride (CAS: 1823-59-2) or 3,3',4,4'-tetracarboxylic biphenyl dianhydride (CAS: 2420-87-3);

[0013] Its structural formula is shown in formula 1)-3) respectively:

[0014]

[0015]

[0016] The other diamine is selected from one or more of 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (CAS: 69563-88-8), 2,2-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane (CAS: 94525-07-2), 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (CAS: 83558-87-6) or N,N'-[2,2'-bis(trifluoromethyl)]-[1,1'-biphenyl]-4,4'-diacyl]bis[4-aminobenzene] (CAS: 1449757-11-2);

[0017] Its structural formulas are shown in formulas 4)-7) respectively:

[0018]

[0019]

[0020] The highly polar aprotic organic solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone and dimethyl sulfoxide.

[0021] In the step (1), the molar ratio of bisphenol AF to 2,4-dinitrochlorobenzene is 1:(2-3); the mass volume ratio of the total amount of bisphenol AF and 2,4-dinitrochlorobenzene to N,N-dimethylformamide is 1:(1-2) g / mL; the molar ratio of bisphenol AF to anhydrous potassium carbonate is 1:(1-2); and the volume ratio of N,N-dimethylformamide to toluene is 2:(1-2).

[0022] In the step (1), the reaction temperature is 120-130° C. and the reaction time is 8-12 hours.

[0023] In the step (2), the palladium content in the palladium-carbon catalyst is 5 wt.%; the mass ratio of 2,2-bis[4-(2,4-dinitrophenoxy)phenyl]hexafluoropropane to the palladium-carbon catalyst is 1:(0.1-0.2); the pressure of hydrogen is 0.4-0.6 MPa, and the reaction is continued until the hydrogen pressure remains unchanged, and the pressure is maintained for 1-3 hours.

[0024] In the step (3), the molar ratio of 2,2-bis[4-(2,4-diaminophenoxy)phenyl]hexafluoropropane to maleic anhydride is 1:(2-2.5); the mass volume ratio of the total amount of 2,2-bis[4-(2,4-diaminophenoxy)phenyl]hexafluoropropane and maleic anhydride to the strongly polar aprotic organic solvent is 1:(20-25) g / mL; the stirring reaction temperature is 0-5°C, and the reaction time is 8-10h.

[0025] The polyimide film is prepared by using the above-mentioned polyamic acid resin solution containing fluorene structure.

[0026] The method for preparing the polyimide film comprises the following steps:

[0027] Adding dianhydride and diamine into a highly polar aprotic organic solvent, stirring and reacting until a homogeneous and transparent phase is obtained to obtain a polyamic acid resin solution containing a fluorene group structure;

[0028] The polyimide film is obtained by sequentially coating, removing solvent, curing and stripping the polyamic acid resin solution containing fluorene groups. The maximum temperature for removing solvent and curing is 250°C.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The polyamic acid resin solution containing a fluorene group structure of the present invention is based on the synergistic effect of a specific ratio of 9,9-bis(3,4-dicarboxyphenyl)fluorene anhydride and a diamine containing a maleamic acid side group. The film prepared by using the polyamic acid resin solution has high elastic modulus, excellent tensile strength and heat resistance while ensuring transparency. The film is suitable for flexible OLED substrates, space telescopes, flexible solar cells, transparent glass protective films, liquid crystal alignment films and other fields, and has important application value.

[0031] (2) The preparation method of the present invention has a simple operation process and can be manufactured in a common polyimide resin and film reaction and molding equipment, which reduces equipment investment and process complexity. The source of reaction raw materials is convenient, which is conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 FTIR image of the polyimide film prepared in Example 1;

[0033] Figure 2 The thermogravimetric curves of the polyimide films prepared in the examples and comparative examples are shown. DETAILED DESCRIPTION

[0034] The present invention is further described below with reference to the embodiments, but they do not limit the implementation of the present invention.

[0035] The raw materials used in the examples and comparative examples are conventional commercially available raw materials unless otherwise specified, and the process methods used in the examples and comparative examples are conventional methods in the art unless otherwise specified.

[0036] Example 1

[0037] The method for preparing the diamine containing maleamic acid side groups comprises the following steps:

[0038] (1) 33.6 g (0.1 mol) of bisphenol AF and 40.5 g (0.2 mol) of 2,4-dinitrochlorobenzene were dissolved in 100 mL of N,N-dimethylformamide, and then 13.8 g (0.1 mol) of anhydrous potassium carbonate and 50 mL of toluene were added, and the temperature was raised to reflux for reaction, and the reaction temperature was 130° C. and the reaction time was 8 h. After the reaction was completed, the mother liquor obtained by suction filtration was subjected to reduced pressure distillation until no more dripping liquid appeared in the reflux device to obtain a rotary evaporation liquid, ethanol was added to the rotary evaporation liquid and stirred rapidly until a large amount of light yellow crystals were precipitated, and the crystals were washed and dried to obtain 2,2-bis[4-(2,4-dinitrophenoxy)phenyl]hexafluoropropane;

[0039] (2) 32 g of 2,2-bis[4-(2,4-dinitrophenoxy)phenyl]hexafluoropropane and 4.8 g of 5 wt.% palladium-carbon catalyst were added to a reaction kettle, and hydrogen gas at a pressure of 0.5 MPa was introduced to carry out a hydrogenation reduction reaction, and the reaction was continued until the hydrogen pressure no longer changed, and the pressure was maintained for 3 h to stop the reaction, and the liquid was filtered while hot, and then poured into pure water to obtain 2,2-bis[4-(2,4-diaminophenoxy)phenyl]hexafluoropropane;

[0040] (3) 0.686 g (0.0012 mol) of 2,2-bis[4-(2,4-diaminophenoxy)phenyl]hexafluoropropane and 0.235 g (0.0024 mol) of maleic anhydride were dissolved in a jacketed bottle containing 20 mL of N,N-dimethylformamide, and stirred at 3° C. under a nitrogen atmosphere for 8 h to obtain a diamine containing a maleamic acid side group.

[0041] The method for preparing the polyimide film comprises the following steps:

[0042] 7.063 g (0.0108 mol) of 2,2-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane was added to a 250 mL jacketed bottle, and then 33.12 g of N,N-dimethylformamide was added to the jacketed bottle. After stirring in a nitrogen atmosphere and an ice water bath at 3°C ​​until completely dissolved, 3.35 g (0.0108 mol) of 3,3',4,4'-tetracarboxylic diphenyl was added. Ether dianhydride, stirred for 0.5h, added 0.55g (0.0012mol) of 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, stirred for 6h, added 0.72g (0.0012mol) of diamine containing maleamic acid side groups, stirred and reacted at 3°C ​​for 24h until the phase became homogeneous and transparent, to obtain a polyamic acid resin solution containing a fluorene structure; the viscosity thereof at 25°C was measured to be 1750mPa·s.

[0043] The polyamic acid resin solution containing the fluorene-based structure prepared above was allowed to stand for 48 hours, and after the bubbles therein were eliminated, it was coated on a clean and smooth glass plate with a 250μm scraper to obtain a film with a thickness of 20μm, and then baked at 80°C for 4 hours in nitrogen to remove the solvent, and then at a pressure of -0.095±0.005MPa, the temperature was increased to 150°C at a rate of 5°C / min, and the temperature was kept warm for 1 hour, and then the temperature was increased to 250°C at a rate of 5°C / min, and the temperature was kept warm for 1 hour. After natural cooling, the glass plate was immersed in hot water at 90±10°C for demolding to obtain a polyimide film.

[0044] The polyimide film was tested using a Fourier transform infrared spectrometer. The measured FTIR graph is shown in the figure below. Figure 1 As shown by Figure 1 It can be seen that the peak near 3368.9cm-1 is the stretching vibration peak of NH, the peak near 1780.7cm-1 corresponds to C=O on the anhydride ring, and the peak near 1716.4cm-1 corresponds to C=O of the imide group in the polyimide chain. The existence of these two peaks indicates the existence of the imide group in the polyimide structure, which is the characteristic absorption peak of polyimide. The peaks near 839.5cm-1 and 740cm-1 are related to the out-of-plane bending vibration of CH on the benzene ring, confirming the existence of the benzene ring structure. The characteristic peaks contained in the infrared image verify the successful synthesis of the polyimide film.

[0045] Example 2

[0046] The method for preparing the diamine containing maleamic acid side groups comprises the following steps:

[0047] (1) 33.6 g (0.1 mol) of bisphenol AF and 46.59 g (0.23 mol) of 2,4-dinitrochlorobenzene were dissolved in 100 mL of N,N-dimethylformamide, and then 13.8 g (0.1 mol) of anhydrous potassium carbonate and 80 mL of toluene were added, and the temperature was raised to reflux for reaction, and the reaction temperature was 125° C. and the reaction time was 10 h. After the reaction was completed, the mother liquor obtained by suction filtration was subjected to reduced pressure distillation until no more dripping liquid appeared in the reflux device to obtain a rotary evaporation liquid, ethanol was added to the rotary evaporation liquid and stirred rapidly until a large amount of light yellow crystals were precipitated, and the crystals were washed and dried to obtain 2,2-bis[4-(2,4-dinitrophenoxy)phenyl]hexafluoropropane;

[0048] (2) 32 g of 2,2-bis[4-(2,4-dinitrophenoxy)phenyl]hexafluoropropane and 5.44 g of 5 wt.% palladium-carbon catalyst were added to a reaction kettle, and hydrogen gas at a pressure of 0.6 MPa was introduced to carry out a hydrogenation reduction reaction, and the reaction was carried out until the hydrogen pressure no longer changed, and the pressure was maintained for 2 h to stop the reaction, and the liquid was filtered while hot, and then poured into pure water to obtain 2,2-bis[4-(2,4-diaminophenoxy)phenyl]hexafluoropropane;

[0049] (3) 0.686 g (0.0012 mol) of 2,2-bis[4-(2,4-diaminophenoxy)phenyl]hexafluoropropane and 0.235 g (0.0024 mol) of maleic anhydride were dissolved in a jacketed bottle containing 20 mL of N,N-dimethylacetamide, and stirred at 3°C ​​for 8 h under a nitrogen atmosphere to obtain a diamine containing a maleamic acid side group.

[0050] The method for preparing the polyimide film comprises the following steps:

[0051] 6.03 g (0.0108 mol) of N,N'-[2,2'-bis(trifluoromethyl)]-[1,1'-biphenyl]-4,4'-diacyl]bis[4-aminobenzene] was added to a 250 mL jacketed bottle, and then 33.12 g of N,N-dimethylacetamide was added to the jacketed bottle. After stirring in a nitrogen atmosphere and an ice water bath at 3°C ​​until completely dissolved, 3 g (0.009 mol) of 3,3',4,4'- Tetracarboxy diphenyl ether dianhydride was stirred for 0.5 h, 1.375 g (0.003 mol) of 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride was added, and the mixture was stirred for 6 h. 0.72 g (0.0012 mol) of a diamine containing a maleamic acid side group was added, and the mixture was stirred at 2° C. for 24 h until the mixture became homogeneous and transparent, thereby obtaining a polyamic acid resin solution containing a fluorene group structure. The viscosity of the solution at 25° C. was measured to be 52500 mPa·s.

[0052] The polyamic acid resin solution containing the fluorene-based structure prepared above was allowed to stand for 48 hours, and after the bubbles therein were eliminated, it was coated on a clean and smooth glass plate with a 250μm scraper to obtain a film with a thickness of 20μm, and then baked at 80°C for 4 hours in nitrogen to remove the solvent, and then at a pressure of -0.095±0.005MPa, the temperature was increased to 150°C at a rate of 5°C / min, and the temperature was kept warm for 1 hour, and then the temperature was increased to 250°C at a rate of 5°C / min, and the temperature was kept warm for 1 hour. After natural cooling, the glass plate was immersed in hot water at 90±10°C for demolding to obtain a polyimide film.

[0053] Example 3

[0054] The method for preparing the diamine containing maleamic acid side groups comprises the following steps:

[0055] (1) 33.6 g (0.1 mol) of bisphenol AF and 52.7 g (0.26 mol) of 2,4-dinitrochlorobenzene were dissolved in 100 mL of N,N-dimethylformamide, and then 13.8 g (0.1 mol) of anhydrous potassium carbonate and 70 mL of toluene were added, and the temperature was raised to reflux for reaction, and the reaction temperature was 120° C. and the reaction time was 8 h. After the reaction was completed, the mother liquor obtained by suction filtration was subjected to reduced pressure distillation until no more dripping liquid appeared in the reflux device to obtain a rotary evaporation liquid, ethanol was added to the rotary evaporation liquid and stirred rapidly until a large amount of light yellow crystals were precipitated, and the crystals were washed and dried to obtain 2,2-bis[4-(2,4-dinitrophenoxy)phenyl]hexafluoropropane;

[0056] (2) 32 g of 2,2-bis[4-(2,4-dinitrophenoxy)phenyl]hexafluoropropane and 6.08 g of 5 wt.% palladium-carbon catalyst were added to a reaction kettle, and hydrogen gas at a pressure of 0.4 MPa was introduced to carry out a hydrogenation reduction reaction, and the reaction was continued until the hydrogen pressure no longer changed, and the pressure was maintained for 3 h to stop the reaction, and the liquid was filtered while hot, and then poured into pure water to obtain 2,2-bis[4-(2,4-diaminophenoxy)phenyl]hexafluoropropane;

[0057] (3) 0.686 g (0.0012 mol) of 2,2-bis[4-(2,4-diaminophenoxy)phenyl]hexafluoropropane and 0.235 g (0.0024 mol) of maleic anhydride were dissolved in a jacketed bottle containing 20 mL of N-methyl-2-pyrrolidone, and stirred at 3° C. under a nitrogen atmosphere for 8 h to obtain a diamine containing a maleamic acid side group.

[0058] The method for preparing the polyimide film comprises the following steps:

[0059] 7.063 g (0.0108 mol) of 2,2-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane was added to a 250 mL jacketed bottle, and then 33.12 g of N,N-dimethylformamide was added to the jacketed bottle. After stirring in a 3°C ice water bath under a nitrogen atmosphere until completely dissolved, 2.648 g (0.009 mol) of 3,3',4,4'-tetracarboxylic acid was added. Phthalic anhydride, stirred for 0.5h, 1.375g (0.003mol) of 9,9-bis(3,4-dicarboxyphenyl)fluorene anhydride was added, stirred for 6h, 0.72g (0.0012mol) of a diamine containing a maleamic acid side group was added, and the reaction was stirred at 3°C ​​for 24h until the phase became homogeneous and transparent to obtain a polyamic acid resin solution containing a fluorene group structure; the viscosity thereof at 25°C was measured to be 6758mPa·s.

[0060] The polyamic acid resin solution containing the fluorene-based structure prepared above was allowed to stand for 48 hours, and after the bubbles therein were eliminated, it was coated on a clean and smooth glass plate with a 250μm scraper to obtain a film with a thickness of 20μm, and then baked at 80°C for 4 hours in nitrogen to remove the solvent, and then at a pressure of -0.095±0.005MPa, the temperature was increased to 150°C at a rate of 5°C / min, and the temperature was kept warm for 1 hour, and then the temperature was increased to 250°C at a rate of 5°C / min, and the temperature was kept warm for 1 hour. After natural cooling, the glass plate was immersed in hot water at 90±10°C for demolding to obtain a polyimide film.

[0061] Comparative Example 1

[0062] The method for preparing the polyimide film comprises the following steps:

[0063] 7.848 g (0.012 mol) of 2,2-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane was added to a 250 mL jacketed bottle, and then 37.5 g of N-methyl-2-pyrrolidone was added to the jacketed bottle. After stirring in a 3°C ice water bath under a nitrogen atmosphere until completely dissolved, 3.35 g (0.0108 mol) of 3,3',4,4'-tetracarboxylic diphenyl ether dianhydride was added to the system in batches, with an interval of 0.5 h between each batch, and then 0.55 g (0.0012 mol) of 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride was added, and the reaction was stirred for 12 hours. The molar ratio of the dianhydride monomer to the diamine monomer was controlled to be 1:1, and the molar ratio of 3,3',4,4'-tetracarboxy diphenyl ether dianhydride to 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride was controlled to be 9:1. Subsequently, 0.31 g of pyridine and 1.20 g of acetic anhydride were added, and the reaction was continued with stirring for 4 hours to obtain a polyimide resin solution with a mass fraction of 25%.

[0064] The polyimide resin solution prepared as above was allowed to stand for 48 hours, and after the bubbles therein were eliminated, it was coated on a clean and smooth glass plate with a 250μm scraper to obtain a film with a thickness of 20μm, and then baked at 80°C for 4 hours in nitrogen to remove the solvent, and then at a pressure of -0.095±0.005MPa, the temperature was increased to 150°C at a rate of 5°C / min, and the temperature was kept constant for 1 hour, and then the temperature was increased to 250°C at a rate of 5°C / min, and the temperature was kept constant for 1 hour. After natural cooling, the glass plate was immersed in hot water at 90±10°C for demolding to obtain a polyimide film.

[0065] Comparative Example 2

[0066] The preparation method of the diamine containing maleamic acid side groups has the same steps as Example 1.

[0067] The method for preparing the polyimide film comprises the following steps:

[0068] 7.063 g (0.0108 mol) of 2,2-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane was added to a 250 mL jacketed bottle, 33.12 g of N,N-dimethylformamide was added to the jacketed bottle, and the mixture was stirred in a nitrogen atmosphere and an ice-water bath at 3°C ​​until it was completely dissolved, 3.35 g (0.0108 mol) of 3,3',4,4'-tetracarboxyl diphenyl ether dianhydride was added, and the mixture was stirred for 0.5 h, 0.533 g (0.0012 mol) of 2,2-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride was added, and the mixture was stirred for 6 h, and 0.72 g (0.0012 mol) of a diamine containing a maleamic acid side group was added, and the mixture was stirred at 3°C ​​for 24 h until the mixture was homogeneous and transparent to obtain a polyamic acid resin solution; the viscosity of the solution at 25°C was measured to be 1018 mPa·s.

[0069] The polyamic acid resin solution prepared above was allowed to stand for 48 hours, and after the bubbles therein were eliminated, it was coated on a clean and smooth glass plate with a 250μm scraper to obtain a film with a thickness of 20μm, and then baked at 80°C for 4 hours in nitrogen to remove the solvent, and then at a pressure of -0.095±0.005MPa, the temperature was increased to 150°C at a rate of 5°C / min, and the temperature was kept warm for 1 hour, and then the temperature was increased to 250°C at a rate of 5°C / min, and the temperature was kept warm for 1 hour. After natural cooling, the glass plate was immersed in hot water at 90±10°C for demolding to obtain a polyimide film.

[0070] The polyimide films prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to performance tests, and the test methods were as follows:

[0071] Elastic modulus (MPa): Tested in accordance with GB / T 1040.3-2006;

[0072] Elongation at break (%): Tested in accordance with GB / T 1040.3-2006;

[0073] Tensile strength (MPa): Tested in accordance with GB / T 1040.3-2006;

[0074] Tensile breaking stress (MPa): Tested in accordance with GB / T 1040.3-2006;

[0075] Tensile yield stress (MPa): Tested in accordance with GB / T 1040.3-2006

[0076] Maximum visible light transmittance (%): Tested in accordance with GB / T 2410-2008;

[0077] Yellowness value: Tested in accordance with GB / T 2410-2008;

[0078] The test results are shown in Table 1:

[0079] Table 1 Polyimide film performance test results

[0080]

[0081] It can be seen from the data in Table 1 that the mechanical properties of the polyimide films prepared in Examples 1-3 are better than those in the comparative example.

[0082] The high temperature resistance of the polyimide films prepared in Examples 1-3 and Comparative Examples 1-2 was tested using a thermogravimetric analyzer TGA55. The test results are as follows: Figure 2 As shown by Figure 2 It can be seen that at the thermal weight loss temperature of 1%, the polyimide film in Example 1-3 to which 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride and a diamine containing maleic anhydride side groups are added has a higher temperature than the polyimide film in Comparative Example 1-2 to which these two raw materials are not added at the same time, indicating that the film containing 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride and a diamine containing maleic anhydride side groups has better thermal stability.

Claims

1. A polyamic acid resin solution containing a fluorene structure, characterized in that: It is prepared by polymerizing equimolar dianhydrides and diamines in a highly polar aprotic organic solvent, wherein the dianhydride is a mixture of 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride and other dianhydrides in a molar ratio of 1:(3-9); the diamine is a mixture of a diamine containing a maleamic acid side group and other diamines in a molar ratio of 1:(8-9); The method for preparing the diamine containing maleamic acid side groups comprises the following steps: (1) dissolving bisphenol AF and 2,4-dinitrochlorobenzene in N,N-dimethylformamide, then adding anhydrous potassium carbonate and toluene, heating and refluxing to react, and after the reaction is completed, filtering and vacuum distilling are performed in sequence to obtain a rotary evaporation liquid, adding ethanol to the rotary evaporation liquid, and performing crystallization, washing and drying to obtain 2,2-bis[4-(2,4-dinitrophenoxy)phenyl]hexafluoropropane; (2) adding a palladium-carbon catalyst to 2,2-bis[4-(2,4-dinitrophenoxy)phenyl]hexafluoropropane, introducing hydrogen gas to carry out a hydrogenation reduction reaction, and obtaining 2,2-bis[4-(2,4-diaminophenoxy)phenyl]hexafluoropropane; (3) Dissolving 2,2-bis[4-(2,4-diaminophenoxy)phenyl]hexafluoropropane and maleic anhydride in a strongly polar aprotic organic solvent, stirring and reacting, thereby preparing a diamine containing a maleamic acid side group.

2. The polyamic acid resin solution containing a fluorene structure according to claim 1, characterized in that: The other dianhydride is selected from one or more of 2,2-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride, 3,3',4,4'-tetracarboxylic diphenyl ether dianhydride or 3,3',4,4'-tetracarboxylic biphenyl dianhydride; Its structural formula is shown in formula 1)-3) respectively:

3. The polyamic acid resin solution containing a fluorene group structure according to claim 1, characterized in that: The other diamine is selected from one or more of 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane or N,N'-[2,2'-bis(trifluoromethyl)]-[1,1'-biphenyl]-4,4'-diacyl]bis[4-aminobenzene]; Its structural formulas are shown in formulas 4)-7) respectively:

4. The polyamic acid resin solution containing a fluorene structure according to claim 1, characterized in that: The highly polar aprotic organic solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone and dimethyl sulfoxide.

5. The polyamic acid resin solution containing a fluorene structure according to claim 1, characterized in that: In the step (1), the molar ratio of bisphenol AF to 2,4-dinitrochlorobenzene is 1:(2-3); the mass volume ratio of the total amount of bisphenol AF and 2,4-dinitrochlorobenzene to N,N-dimethylformamide is 1:(1-2) g / mL; the molar ratio of bisphenol AF to anhydrous potassium carbonate is 1:(1-2); and the volume ratio of N,N-dimethylformamide to toluene is 2:(1-2).

6. The polyamic acid resin solution containing a fluorene group structure according to claim 1, characterized in that: In the step (1), the reaction temperature is 120-130° C. and the reaction time is 8-12 hours.

7. The polyamic acid resin solution containing a fluorene group structure according to claim 1, characterized in that: In the step (2), the palladium content in the palladium-carbon catalyst is 5 wt.%; the mass ratio of 2,2-bis[4-(2,4-dinitrophenoxy)phenyl]hexafluoropropane to the palladium-carbon catalyst is 1:(0.1-0.2); the pressure of hydrogen is 0.4-0.6 MPa, and the reaction is continued until the hydrogen pressure remains unchanged, and the pressure is maintained for 1-3 hours.

8. The polyamic acid resin solution containing a fluorene group structure according to claim 1, characterized in that: In the step (3), the molar ratio of 2,2-bis[4-(2,4-diaminophenoxy)phenyl]hexafluoropropane to maleic anhydride is 1:(2-2.5); the mass volume ratio of the total amount of 2,2-bis[4-(2,4-diaminophenoxy)phenyl]hexafluoropropane and maleic anhydride to the strongly polar aprotic organic solvent is 1:(20-25) g / mL; the stirring reaction temperature is 0-5°C, and the reaction time is 8-10h.

9. A polyimide film, characterized in that: The polyamic acid resin solution containing a fluorene group structure is prepared by using any one of claims 1 to 8.

10. A method for preparing a polyimide film according to claim 9, characterized in that: The following steps are involved: Adding dianhydride and diamine into a highly polar aprotic organic solvent, stirring and reacting until a homogeneous and transparent phase is obtained to obtain a polyamic acid resin solution containing a fluorene group structure; The polyimide film is obtained by sequentially coating, removing solvent, curing and stripping the polyamic acid resin solution containing fluorene groups. The maximum temperature for removing solvent and curing is 250°C.

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