Polyamide acid salt solution with high solid content and low viscosity and preparation method thereof

Abstract

The invention relates to the field of high-performance resin-based materials, in particular to a high-solid-content low-viscosity polyamide acid salt solution and a preparation method thereof. The method comprises the following steps: (1) carrying out polymerization reaction on a dianhydride monomer and a diamine monomer to obtain a polyamide acid solution; (2) the polyamic acid solution and organic alkali are subjected to a contact reaction, a polyamic acid salt original solution is obtained, and the organic alkali is selected from one or more of pyridine compounds and aniline compounds; (3) carrying out precipitation treatment on the polyamic acid salt raw solution to obtain polyamic acid salt powder; and (4) dissolving the polyamic acid salt powder to obtain a polyamic acid salt solution. According to the method disclosed by the invention, the polyamide acid salt solution with high solid content can be prepared, and the polyamide acid salt solution has relatively low apparent viscosity under the condition of high solid content, so that the polyamide acid salt solution has excellent processability and a wide application range.

Description

Technical Field

[0001] The present invention relates to the field of high-performance resin-based materials, and particularly to a polyamic acid salt solution with a high solid content and low viscosity and a preparation method thereof. Background Art

[0002] As a high-performance polymer material, polyimide is endowed with excellent properties due to the unique imide ring structure in its molecular main chain. With the urgent demand for high-performance materials in modern aerospace and military industries, the development and research of polyimide have gradually accelerated. With a series of excellent characteristics such as high thermal oxidative stability, unique electrical properties, excellent mechanical properties, good radiation resistance and solvent resistance, polyimide has been widely used in many fields such as aerospace, microelectronics, liquid crystal technology, flame retardant materials and separation membranes.

[0003] The two-step method is the most commonly used polyimide synthesis technology at present. In this method, dianhydride and diamine monomers are first dissolved in aprotic polar solvents such as N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide at low temperature, and polyimide precursors are prepared through a polycondensation reaction. Subsequently, these precursors are converted into polyimide through thermal imidization or chemical imidization reactions.

[0004] Generally, precursors include polyamic acid and polyamic acid salts (usually complexes formed by triethylamine and polyamic acid). When the solid content of the polyamic acid solution is relatively high (>10wt%), its structural characteristics make it show a very high apparent viscosity in these aprotic solvents, and even gel and almost completely lose fluidity. Therefore, it is difficult to obtain a polyamic acid solution with a high solid content and low viscosity through conventional methods, which severely limits the processing of the polyamic acid solution and the ability to control the physical structure of polyimide materials.

[0005] The polyamic acid triethylamine salt, which has been widely studied at present, has better storage stability than polyamic acid, but it has a higher apparent viscosity than polyamic acid, which limits the application of the polyamic acid salt solution in related fields such as spinning solutions and films. Summary of the Invention

[0006] The object of the present invention is to overcome the problems existing in the above-mentioned prior art, and provide a polyamic acid salt solution with a high solid content and low viscosity and a preparation method thereof. This method is simple to operate and can prepare a polyamic acid salt solution with a high solid content while having a low surface viscosity.

[0007] To achieve the above object, on the one hand, the present invention provides a preparation method of a polyamic acid salt solution, which includes:

[0008] (1) Polymerize a dianhydride monomer and a diamine monomer to obtain a polyamic acid solution;

[0009] (2) The polyamic acid solution is subjected to a contact reaction with an organic base to obtain a crude polyamic acid salt solution, wherein the organic base is selected from one or more of pyridine compounds and aniline compounds;

[0010] (3) The crude polyamic acid salt solution is subjected to a precipitation treatment to obtain polyamic acid salt powder;

[0011] (4) The polyamic acid salt powder is dissolved to obtain a polyamic acid salt solution.

[0012] A second aspect of the present invention provides a polyamic acid salt solution prepared by the above method.

[0013] A third aspect of the present invention provides a polyimide film prepared from the above polyamic acid salt solution.

[0014] In the present invention, an organic base with a specific structure is added to the polyamic acid solution to reduce the surface viscosity of the solution. Further, after the obtained crude polyamic acid salt solution is subjected to a precipitation treatment to obtain polyamic acid salt powder and then redissolved, the surface viscosity of the solution is further greatly reduced, and finally a polyamic acid salt solution with a high solid content and an extremely low apparent viscosity is prepared.

[0015] The preparation method of the present invention is simple in operation, mild in conditions, obvious in effect, and easy to industrialize. The obtained polyamic acid salt solution has an extremely low apparent viscosity while maintaining a high solid content, so that it has better processing performance and a wider application range. In addition, the polyimide film prepared from the polyamic acid salt solution as a polyimide precursor solution has mechanical properties equivalent to those of the polyimide film directly prepared from the polyamic acid solution. Detailed Embodiments

[0016] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0017] One aspect of the present invention provides a method for preparing a polyamic acid salt solution, the method comprising:

[0018] (1) A dianhydride monomer and a diamine monomer are subjected to a polymerization reaction to obtain a polyamic acid solution;

[0019] (2) Contact the polyamic acid solution with an organic base to obtain a crude polyamic acid salt solution, wherein the organic base is selected from one or more of pyridine compounds and aniline compounds;

[0020] (3) Perform precipitation treatment on the crude polyamic acid salt solution to obtain polyamic acid salt powder;

[0021] (4) Dissolve the polyamic acid salt powder to obtain a polyamic acid salt solution.

[0022] According to the present invention, in order to obtain a polyamic acid solution with better performance, the dosages of the dianhydride monomer and the diamine monomer can be adjusted. Preferably, relative to 1 mmol of the dianhydride monomer, the dosage of the diamine monomer is 0.95 - 1.05 mmol, preferably 0.98 - 1.02 mmol. For example, it can be values such as 0.98 mmol, 0.99 mmol, 1 mmol, and 1.02 mmol and the ranges between any of these values.

[0023] According to the present invention, in order to enable the monomers to come into more sufficient contact and achieve better reaction effects, the solvent used in the polymerization reaction can be selected. Preferably, the solvent for the polymerization reaction is selected from one or more of aprotic polar solvents, preferably one or more of N,N - dimethylformamide, N,N - dimethylacetamide, N - methylpyrrolidone, N - vinylpyrrolidone, and dimethyl sulfoxide.

[0024] According to the present invention, in order for the polymerization reaction to proceed better and reduce the generation of impurities and by - products, the conditions of the polymerization reaction can be adjusted. Preferably, the conditions of the polymerization reaction include: the temperature is - 10°C to 50°C, and the time is 2 - 12 h; more preferably, the conditions of the polymerization reaction include: the temperature is - 5°C to 20°C (for example, it can be values such as - 5°C, 0°C, 5°C, 10°C, and 20°C and the ranges between any of these values), and the time is 4 - 8 h (for example, it can be values such as 4 h, 5 h, 6 h, and 8 h and the ranges between any of these values).

[0025] According to the present invention, in order to keep the polyamic acid solution in good properties and facilitate the subsequent steps, the solid content of the polyamic acid solution can be adjusted. Preferably, the solid content of the polyamic acid solution is 6 - 18 wt%, preferably 8 - 15 wt%. For example, it can be values such as 8 wt%, 10 wt%, 12 wt%, and 15 wt% and the ranges between any of these values.

[0026] According to the present invention, the dianhydride monomer and the diamine monomer can be selected within a relatively wide range. In order to achieve better effects, preferably, the dianhydride monomer is selected from one or more of; wherein, A and B are each independently selected from a benzene ring, cyclobutane, cyclohexane, and one or more of; R 1 is selected from a linking bond, an oxy group, one or more of; R 2 , R 3 , R 4 and R 5 are each independently selected from C1-C6 alkylene groups, one or more of;

[0027] More preferably, the dianhydride monomer is selected from one or more of the compounds represented by the following formula:

[0028]

[0029] Preferably, the diamine monomer is selected from

[0030] one or more of; wherein, each R 7 is each independently selected from one or more of H, an amino group, a hydroxyl group, a carboxyl group, a trifluoromethyl group, a halogen, and a C1-C6 alkyl group, and at least one R 7 is an amino group; each R 8 is each independently selected from one or more of H, an amino group, a hydroxyl group, a carboxyl group, a trifluoromethyl group, a halogen, and a C1-C6 alkyl group, and at least one R 8 is an amino group; R 6 is selected from a linking bond, an oxy group, a C1-C6 alkylene group, one or more of; R 9 , R 10 , R 11 , R 12 and R 13 are each independently selected from one or more of;

[0031] More preferably, the diamine monomer is selected from one or more of the compounds represented by the following formula:

[0032]

[0033]

[0034] According to the present invention, in order to reduce the generation of impurities and by-products, preferably, the polymerization reaction is carried out in an inert gas atmosphere, wherein the inert gas can be, for example, nitrogen and / or argon.

[0035] According to the present invention, by contacting a polyamic acid solution with an organic base having a specific structure, a corresponding polyamic acid salt stock solution can be obtained, which effectively reduces the apparent viscosity of the solution while improving the stability and enhancing the processing performance. In order to obtain a better polyamic acid salt stock solution, the organic base and its dosage can be selected. Preferably, the organic base is selected from one or more of pyridine, quinoline, isoquinoline, 4-methylpyridine, 2,6-dimethylpyridine, 2,4,6-trimethylpyridine, N,N-diethylaniline, and N,N-dimethylaniline, and preferably one or more of pyridine, quinoline, and 4-methylpyridine.

[0036] Preferably, relative to 1 mmol of the dianhydride monomer, the dosage of the organic base is 1-6 mmol, preferably 2-4 mmol, and can be, for example, values such as 2 mmol, 2.5 mmol, 3 mmol, 3.6 mmol, and 4 mmol and the ranges between any of these values.

[0037] According to the present invention, in order to achieve a better reaction effect in the contact reaction, preferably, the time of the contact reaction is 1-8 h, preferably 2-6 h, and can be, for example, values such as 2 h, 4 h, 5 h, and 6 h and the ranges between any of these values.

[0038] According to the present invention, by subjecting the polyamic acid salt stock solution to a precipitation treatment, the corresponding polyamic acid salt powder can be obtained. Preferably, the precipitation treatment includes: contacting a precipitant with the polyamic acid salt stock solution to obtain the polyamic acid salt powder.

[0039] According to the present invention, in order to achieve a better precipitation effect and obtain a polyamic acid salt powder with more excellent properties, the precipitant and its dosage can be selected. Preferably, the precipitant is selected from one or more of C1-C10 alkyl alcohols, water, and acetone, and preferably one or more of methanol, ethanol, isopropanol, n-butanol, water, and acetone.

[0040] Preferably, relative to 1 mL of the polyamic acid salt stock solution, the dosage of the precipitant is 2-8 mL, preferably 3-5 mL, and can be, for example, values such as 3 mL, 3.5 mL, 4 mL, and 5 mL and the ranges between any of these values.

[0041] According to the present invention, in the above precipitation treatment, the specific manner of contacting the precipitant with the polyamic acid salt stock solution can be selected within a relatively wide range. For example, titration treatment or direct stirring can be used, and titration treatment is more preferred.

[0042] According to the present invention, after the precipitation treatment is completed, post-treatment can be carried out to obtain polyamide acid salt powder. The post-treatment method can be selected within a wide range. Preferably, the post-treatment method includes separation (for example, achieved by operations such as filtration) and drying (the drying time and temperature can be selected within a wide range, generally 40 - 60 °C, 4 - 10 h).

[0043] According to the present invention, after the polyamide acid salt original solution is treated by precipitation to obtain polyamide acid salt powder, and then redissolved, the apparent viscosity of the redissolved solution can be significantly reduced again, and the reduction amplitude is much higher than that in step (2). The microscopic molecular process during this period can prepare a polyamide acid salt solution with a high solid content while keeping its apparent viscosity in a very low range, thereby improving its processing performance and application range. Among them, the solvent for the second redissolution can be selected within a wide range. Preferably, the solvent for dissolving the polyamide acid salt powder is selected from one or more of aprotic polar solvents, preferably one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, N-vinylpyrrolidone, and dimethyl sulfoxide.

[0044] According to the present invention, by using the method of the present invention, a polyamide acid salt solution with a high solid content can be prepared. In practical applications, the solid content of the polyamide acid salt solution can be selected within a wide range according to actual needs. To fully exert its advantages of high solid content and low viscosity, preferably, the solid content of the polyamide acid salt solution is 5 - 60 wt%, preferably 20 - 45 wt%, for example, it can be values such as 20 wt%, 25 wt%, 30 wt%, 40 wt%, and 45 wt% and the ranges between any of these values.

[0045] According to the present invention, traditional polyimide precursor solutions are generally difficult to prepare solutions with a high solid content, and their apparent viscosities are relatively high, which is not conducive to processing them into polyimide films, and the properties of the obtained polyimide films also need to be improved. However, the method of the present invention can achieve the preparation of a polyamide acid salt solution with a high solid content and keep its apparent viscosity low, effectively solving the above problems. The apparent viscosity increases exponentially with the increase of the solid content. The apparent viscosity of the polyamide acid salt solution of the present invention can be selected within a wide range. Preferably, the apparent viscosity of the polyamide acid salt solution is 10 - 3000000 cP, preferably 100 - 500000 cP, for example, it can be values such as 300 cP, 1000 cP, 6210 cP, 22460 cP, 100900 cP, and 489000 cP and the ranges between any of these values.

[0046] The second aspect of the present invention provides a polyamide acid salt solution prepared by the above method.

[0047] The third aspect of the present invention provides a polyimide film prepared from the above polyamic acid salt solution.

[0048] In the present invention, an organic base with a specific structure is added to the polyamic acid solution to reduce the surface viscosity of the solution. Further, the obtained polyamic acid salt stock solution is subjected to precipitation treatment to obtain polyamic acid salt powder, and then redissolved to further significantly reduce the surface viscosity of the solution, and finally a polyamic acid salt solution with a high solid content and an extremely low apparent viscosity is prepared.

[0049] The preparation method of the present invention is simple in operation, mild in conditions, obvious in effect, and easy to industrialize. The obtained polyamic acid salt solution has an extremely low apparent viscosity while maintaining a high solid content, so that it has more excellent processing performance and a wider application range. In addition, the polyimide film prepared from the polyamic acid salt solution as a polyimide precursor solution has mechanical properties comparable to those of the polyimide film directly prepared from the polyamic acid solution.

[0050] The present invention will be described in detail below through examples.

[0051] In the following examples, the devices used are all conventional devices in the art, the operations adopted are all conventional operations in the art, and the raw materials, reagents, etc. used can be obtained through commercial purchase. Among them, 4,4'-diaminodiphenyl ether, pyromellitic dianhydride, 4,4'-oxybisphthalic anhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride are all purchased from Changzhou Yangguang Pharmaceutical Co., Ltd.

[0052] Example 1

[0053] (1) Under a nitrogen atmosphere, 4,4'-diaminodiphenyl ether (ODA) was added to N,N-dimethylacetamide (DMAc), stirred at room temperature for 1 h until dissolved, and then pyromellitic dianhydride (PMDA) was added, and the reaction was carried out at 0 °C for 6 h to obtain a polyamic acid solution with a solid content of 10 wt%. Among them, the molar ratio of 4,4'-diaminodiphenyl ether to pyromellitic dianhydride was 1:1.

[0054] (2) Pyridine was added to the polyamic acid solution, and the contact reaction was carried out for 2 h to obtain a polyamic acid salt stock solution. Among them, the dosage of pyridine was 2 mmol relative to 1 mmol of pyromellitic dianhydride.

[0055] (3) Ethanol was titrated into the polyamic acid salt stock solution, and powder was precipitated and separated by filtration, and then dried at 40 °C for 10 h to obtain polyamic acid salt (PAAs) powder. Among them, the dosage of ethanol was 3 mL relative to 1 mL of the polyamic acid salt stock solution.

[0056] (4) Add the polyamic acid salt powder to N,N-dimethylacetamide for dissolution to prepare a 25 wt% polyamic acid salt solution.

[0057] Example 2

[0058] (1) Under a nitrogen atmosphere, add 4,4'-diaminodiphenyl ether (ODA) to N,N-dimethylacetamide (DMAc), stir at room temperature for 1 h until dissolved, then add 4,4'-oxydiphthalic anhydride (ODPA), and react at -5 °C for 4 h to obtain a polyamic acid solution with a solid content of 10 wt%. Among them, the molar ratio of 4,4'-diaminodiphenyl ether to 4,4'-oxydiphthalic anhydride is 1:0.98.

[0059] (2) Add pyridine to the polyamic acid solution and carry out a contact reaction for 6 h to obtain a polyamic acid salt stock solution. Among them, the dosage of pyridine is 4 mmol relative to 1 mmol of 4,4'-oxydiphthalic anhydride.

[0060] (3) Add ethanol to the polyamic acid salt stock solution and stir, precipitate and separate the powder, and dry at 50 °C for 8 h to obtain the polyamic acid salt powder. Among them, the dosage of ethanol is 5 mL relative to 1 mL of the polyamic acid salt stock solution.

[0061] (4) Add the polyamic acid salt powder to N,N-dimethylformamide for dissolution to prepare a 25 wt% polyamic acid salt solution.

[0062] Example 3

[0063] (1) Under a nitrogen atmosphere, add 4,4'-diaminodiphenyl ether (ODA) to N,N-dimethylacetamide (DMAc), stir at room temperature for 1 h until dissolved, then add 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), and react at 10 °C for 8 h to obtain a polyamic acid solution with a solid content of 10 wt%. Among them, the molar ratio of 4,4'-diaminodiphenyl ether to 3,3',4,4'-benzophenone tetracarboxylic dianhydride is 1:1.

[0064] (2) Add pyridine to the polyamic acid solution and carry out a contact reaction for 3 h to obtain a polyamic acid salt stock solution. Among them, the dosage of pyridine is 3 mmol relative to 1 mmol of 3,3',4,4'-benzophenone tetracarboxylic dianhydride.

[0065] (3) Titrate ethanol into the first polyamic acid salt solution, precipitate and separate the powder, and dry at 45 °C for 6 h to obtain the polyamic acid salt powder. Among them, the dosage of ethanol is 4 mL relative to 1 mL of the polyamic acid salt stock solution.

[0066] (4) Add the polyamic acid salt powder to dimethyl sulfoxide for dissolution to prepare a 25 wt% polyamic acid salt solution.

[0067] Example 4

[0068] (1) Under a nitrogen atmosphere, add 4,4'-diaminodiphenyl ether (ODA) to N,N-dimethylacetamide (DMAc), stir at room temperature for 1 h until dissolved, then add 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and react at 0 °C for 5 h to obtain a polyamic acid solution with a solid content of 10 wt%. Among them, the molar ratio of 4,4'-diaminodiphenyl ether to 3,3',4,4'-biphenyltetracarboxylic dianhydride is 1:1.

[0069] (2) Add pyridine to the polyamic acid solution and carry out a contact reaction for 4 h to obtain a crude polyamic acid salt solution. Among them, relative to 1 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride, the dosage of pyridine is 2 mmol.

[0070] (3) Titrate ethanol into the crude polyamic acid salt solution, precipitate out the powder, filter and separate it, and dry it at 60 °C for 4 h to obtain the polyamic acid salt powder. Among them, relative to 1 mL of the crude polyamic acid salt solution, the dosage of ethanol is 4 mL.

[0071] (4) Add the polyamic acid salt powder to N,N-dimethylacetamide for dissolution to prepare a 20 wt% polyamic acid salt solution.

[0072] Example 5

[0073] According to the method of Example 4, the difference is that in step (4), the polyamic acid salt powder is added to N,N-dimethylacetamide for dissolution to prepare a 25 wt% polyamic acid salt solution.

[0074] Example 6

[0075] According to the method of Example 4, the difference is that in step (4), the polyamic acid salt powder is added to N,N-dimethylacetamide for dissolution to prepare a 30 wt% polyamic acid salt solution.

[0076] Example 7

[0077] According to the method of Example 4, the difference is that in step (4), the polyamic acid salt powder is added to N,N-dimethylacetamide for dissolution to prepare a 35 wt% polyamic acid salt solution.

[0078] Example 8

[0079] According to the method of Example 4, the difference is that in step (4), the polyamic acid salt powder is added to N,N-dimethylacetamide and dissolved to prepare a 40 wt% polyamic acid salt solution.

[0080] Example 9

[0081] According to the method of Example 4, the difference is that in step (2), relative to 1 mmol of 3,3’,4,4’-biphenyltetracarboxylic dianhydride, the amount of pyridine used is 1 mmol. Finally, a 20 wt% polyamic acid salt solution is prepared.

[0082] Example 10

[0083] According to the method of Example 4, the difference is that in step (2), relative to 1 mmol of 3,3’,4,4’-biphenyltetracarboxylic dianhydride, the amount of pyridine used is 6 mmol. Finally, a 20 wt% polyamic acid salt solution is prepared.

[0084] Example 11

[0085] According to the method of Example 4, the difference is that in step (2), pyridine is replaced by quinoline. Finally, a 20 wt% polyamic acid salt solution is prepared.

[0086] Example 12

[0087] According to the method of Example 4, the difference is that in step (2), pyridine is replaced by 4-methylpyridine. Finally, a 20 wt% polyamic acid salt solution is prepared.

[0088] Comparative Example 1

[0089] According to the method of step (1) in Example 1, a polyamic acid solution (ODA / PMDA) with a solid content of 10 wt% is prepared.

[0090] Comparative Example 2

[0091] According to the method of step (1) in Example 2, a polyamic acid solution (ODA / ODPA) with a solid content of 10 wt% is prepared.

[0092] Comparative Example 3

[0093] According to the method of step (1) in Example 3, a polyamic acid solution (ODA / BTDA) with a solid content of 10 wt% is prepared.

[0094] Comparative Example 4

[0095] According to the method of step (1) in Example 4, a polyamic acid solution (ODA / BPDA) with a solid content of 10 wt% is prepared.

[0096] Comparative Example 5

[0097] According to the method of Example 4, except that in step (2), pyridine is replaced with triethylamine. Finally, a 10 wt% polyamic acid salt solution is prepared.

[0098] Comparative Example 6

[0099] According to the methods of steps (1) and (2) in Example 4, a polyamic acid salt stock solution (solid content: 10 wt%) is prepared.

[0100] Test Example 1

[0101] The solutions obtained in Examples 1-12 and Comparative Examples 1-6 were subjected to an apparent viscosity test. The specific test method was as follows: using a Brookfiled DV2T type rotational viscometer to test the solution at room temperature, with a cone plate rotor having a diameter of 50 mm. The results are shown in Table 1.

[0102] Table 1

[0103]

[0104]

[0105] As can be seen from Table 1, Examples 1-12 adopting the technical solution of the present invention can achieve a relatively high solid content (up to 40 wt% in Example 8), and have an extremely low apparent viscosity while having a high solid content. While Comparative Examples 1-6 not adopting the technical solution of the present invention show a very high apparent viscosity at a relatively low solid content. The performances of Examples 1-12 of the present invention are far superior to those of Comparative Examples 1-6.

[0106] Test Example 2

[0107] The solutions obtained in Examples 1-12 and Comparative Examples 1-6 were defoamed and then coated on a glass plate substrate, and placed in a vacuum oven for stepwise heat treatment (heated at 80 °C for 1 h, 140 °C for 1 h, 220 °C for 0.5 h, and finally heated at 300 °C for 0.5 h) to obtain corresponding polyimide films. The obtained polyimide films were subjected to mechanical property tests. The film tensile strength, film elongation at break, and film Young's modulus of the samples were determined with reference to "GB / T 1040.1-2018 Plastics - Determination of tensile properties - Part 1: General principles".

[0108] The test results are shown in Table 2.

[0109] Table 2

[0110] Serial number Tensile strength of film / (MPa) Elongation at break of film / (%) Young's modulus of film / (MPa) Example 1 120 20 2507 Example 2 126 12 2974 Example 3 136 16 3133 Example 4 133 13 2710 Example 5 143 12 2931 Example 6 143 15 2847 Example 7 142 12 2673 Example 8 146 12 2856 Example 9 141 13 2820 Example 10 126 10 2229 Example 11 130 11 1440 Example 12 129 16 2229 Comparative example 1 121 32 2066 Comparative example 2 121 20 2297 Comparative example 3 137 10 2526 Comparative example 4 141 16 2333 Comparative example 5 145 11 2879 Comparative example 6 140 11 2856

[0111] As can be seen from Table 2, the polyimide films prepared in Examples 1-12 using the technical solution of the present invention have mechanical properties comparable to those of the polyimide films (Comparative Examples 1-4) directly prepared from polyamic acid solutions.

[0112] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for preparing a polyamic acid salt solution, characterized in that: The method includes: (1) polymerizing a dianhydride monomer and a diamine monomer to obtain a polyamic acid solution; (2) contacting the polyamic acid solution with an organic base to obtain a polyamic acid salt original solution, wherein the organic base is selected from one or more of a pyridine compound and an aniline compound; (3) performing a precipitation treatment on the polyamic acid salt original solution to obtain a polyamic acid salt powder; (4) dissolving the polyamic acid salt powder to obtain a polyamic acid salt solution.

2. The method according to claim 1, wherein: The organic base is selected from one or more of pyridine, quinoline, isoquinoline, 4-methylpyridine, 2,6-lutidine, 2,4,6-trimethylpyridine, N,N-diethylaniline and N,N-dimethylaniline, preferably one or more of pyridine, quinoline and 4-methylpyridine; and / or, relative to 1 mmol of the dianhydride monomer, the amount of the organic base is 1-6 mmol, preferably 2-4 mmol; And / or, the contact reaction time is 1-8 hours, preferably 2-6 hours.

3. The method according to claim 1 or 2, wherein: The solid content of the polyamic acid salt solution is 5-60wt%, preferably 20-45wt%; And / or, the apparent viscosity of the polyamic acid salt solution is 10-3000000 cP, preferably 100-500000 cP.

4. The method according to any one of claims 1 to 3, wherein: Relative to 1 mmol of the dianhydride monomer, the amount of the diamine monomer is 0.95-1.05 mmol, preferably 0.98-1.02 mmol; and / or, the solvent for the polymerization reaction is selected from one or more aprotic polar solvents, preferably one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, N-vinylpyrrolidone and dimethyl sulfoxide; And / or, the polymerization reaction conditions include: temperature of -10°C to 50°C, time of 2-12h; more preferably, the polymerization reaction conditions include: temperature of -5°C to 20°C, time of 4-8h; And / or, the solid content of the polyamic acid solution is 6-18wt%, preferably 8-15wt%.

5. The method according to any one of claims 1 to 4, wherein: The dianhydride monomer is selected from wherein A and B are each independently selected from benzene ring, cyclobutane, cyclohexane and One or more of R 1 Selected from a linker, an oxy group, One or more of R 2 , R 3 , R 4 and R 5 Each independently selected from C1-C6 alkylene, One or more of; Preferably, the dianhydride monomer is selected from one or more compounds represented by the following formula:

6. The method according to any one of claims 1 to 5, wherein: The diamine monomer is selected from One or more of; wherein each R 7 Each is independently selected from one or more of H, amino, hydroxyl, carboxyl, trifluoromethyl, halogen and C1-C6 alkyl, and at least one R 7 is an amino group; each R 8 Each is independently selected from one or more of H, amino, hydroxyl, carboxyl, trifluoromethyl, halogen and C1-C6 alkyl, and at least one R 8 R is amino group; 6 Select from the connection key, Suboxy, C1-C6 alkylene, One or more of R 9 , R 10 , R 11 , R 12 and R 13 Each independently selected from One or more of; Preferably, the diamine monomer is selected from one or more compounds represented by the following formula:

7. The method according to any one of claims 1 to 6, wherein: The precipitation treatment comprises: contacting a precipitant with the polyamic acid salt original solution to obtain a polyamic acid salt powder; Preferably, the precipitant is selected from one or more of C1-C10 alkyl alcohols, water and acetone, preferably one or more of methanol, ethanol, isopropanol, n-butanol, water and acetone; Preferably, relative to 1 mL of the first polyamic acid salt solution, the amount of the precipitant is 2-8 mL, preferably 3-5 mL.

8. The method according to any one of claims 1 to 7, wherein: The solvent for dissolving the polyamic acid salt powder is selected from one or more aprotic polar solvents, preferably one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, N-vinylpyrrolidone and dimethyl sulfoxide.

9. The polyamic acid salt solution prepared by the method according to any one of claims 1 to 8.

10. A polyimide film prepared from the polyamic acid salt solution according to claim 9.

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