High-performance polyimide film and preparation method thereof

Abstract

The invention discloses a high-performance polyimide film and a preparation method thereof, and belongs to the technical field of polyimide preparation, and the preparation method comprises the following steps: firstly dissolving a diamine monomer in a solvent, adding a dianhydride monomer accounting for 47-52% of the total molar weight of the diamine monomer for reaction, and in the subsequent reaction, adding the dianhydride monomer while stirring for 4-12 times, the addition amount each time is 47-52% mol of the previous addition amount, obtaining a polyamide acid polymer solution after the reaction is completed, and preparing a film to obtain the polyimide film. According to the invention, reaction kinetics is considered from the perspective of monomer molecule collision probability, under the condition that the addition amount of the dianhydride monomer is gradually reduced in equal proportion, the competitive behavior of polymerization units with different reaction activities on the dianhydride monomer is limited by the collision probability, disordered chain extension behavior is inhibited, highly ordered chain extension is induced, and the reaction efficiency is improved. Finally, polyamide acid with high polymerization and narrow molecular weight distribution is formed, and the mechanical property of the polyimide film is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of polyimide preparation, and in particular relates to a high-performance polyimide film and a preparation method thereof. Background Art

[0002] Polyimide film is one of the organic polymer materials with the best comprehensive performance. It has excellent heat resistance, excellent mechanical properties, good chemical stability, moisture and heat resistance, good radiation resistance and dielectric properties. Polyimide film is synthesized from diamine and dianhydride monomers to form polyamic acid, which is then imidized. Its performance is closely related to that of polyamic acid.

[0003] At room temperature, diamine and dianhydride monomers have very good reactivity without the need for a catalyst, but the polymerization process must be carefully controlled to avoid overreaction resulting in uneven molecular weight distribution (i.e., too wide a polymerization dispersion), which results in product defects with uneven physical property distribution after film formation. Currently, in literature or actual operation, synthesis is mostly carried out at low temperature or controlled at a relatively low temperature to suppress overreaction by lowering the temperature, but this method requires high control of conditions and is not easy to operate.

[0004] The synthesis of polyamic acid (PAA) is a linear polymerization reaction. When the dianhydride monomer enters the solution environment rich in diamine monomers, due to the strong nucleophilic reaction between the anhydride group and the amine group, it will quickly form a covalent bond to become a dimer. If there is a dianhydride monomer next to the dimer, there will be a chance to extend the chain to form a trimer, tetramer or pentamer. The chain extension reaction can be regarded as the competition between the oligomer molecular chains for the reaction monomer (dianhydride monomer). The success of the chain extension depends not only on the collision probability between the oligomer and the reaction monomer, but also on the reactivity of the oligomer molecular chain itself. According to the theory of molecular steric hindrance, the larger the molecular chain, the greater the steric hindrance, resulting in lower reactivity. At the beginning of the polymerization reaction, if a mixed solution of oligomer molecules such as dimers, trimers and tetramers is formed, when the subsequent reaction monomer (dianhydride monomer) is added, due to the difference in activity between the oligomers, the chain extension process must be disordered chain extension, so the molecular weight distribution finally formed will have multiple peaks or wide distribution. Therefore, it is of great significance to control the orderly chain extension of oligomers such as pure binaries, pure ternaries and pure tetramers. Summary of the invention

[0005] The purpose of the present invention is to provide a high-performance polyimide film and a preparation method thereof, and to prepare a polyimide precursor with a high degree of polymerization and a narrow molecular weight distribution by adjusting the polyimide film preparation process, thereby improving the comprehensive performance of the polyimide film.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] The present invention provides a method for preparing a high-performance polyimide film, comprising the following steps:

[0008] Step 1, firstly completely dissolve the diamine monomer in a non-protonic polar solvent, and then add the dianhydride monomer, wherein the amount of the dianhydride monomer added is 47-52% of the total molar amount of the diamine monomer;

[0009] Step 2: After the reaction is stirred, add the dianhydride monomer in 4-12 times while stirring, and the amount added each time is 47-52 mol% of the previous amount, and the amount added decreases proportionally;

[0010] Step 3: After the reaction is completed, a polyamic acid polymer solution is obtained, vacuum degassing and coating are performed, and a polyimide film is obtained through high-temperature imidization treatment.

[0011] Furthermore, the diamine monomer is one of 4,4'-diaminodiphenyl ether and p-phenylenediamine.

[0012] Furthermore, the dianhydride monomer is one of pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride.

[0013] Furthermore, the aprotic polar solvent is one of N,N-dimethylacetamide, N,N-dimethylformamide and N-methylpyrrolidone. These solvents have good solubility and can effectively dissolve dianhydride monomers and diamine monomers, thereby promoting the polymerization reaction.

[0014] Furthermore, the solid content of the polyamic acid polymer solution is 29-32%. The solid content of the polyamic acid polymer solution directly affects its viscosity. When the solid content is low, the viscosity of the polymer solution is low, which is conducive to the processing and film formation of the polymer solution; when the solid content is too low, the viscosity is low, and stratification or uneven distribution is likely to occur; when the solid content is too high, the viscosity of the polymer solution is too high, which may cause the polymer solution to be difficult to process or even gel, thereby affecting the preparation and performance of the film.

[0015] Furthermore, each addition of the dianhydride monomer in step 2 is separated by 20-30 minutes. The addition time interval of the dianhydride monomer during the polyamic acid reaction should not be too long. If the interval time is long, the monomer addition rate is lower than the polymerization reaction rate, which will limit the growth of the polymer chain and affect the molecular weight distribution and structure of the polymer.

[0016] Furthermore, the molar ratio of the diamine monomer to the dianhydride monomer in the raw material of the polyamic acid polymerization liquid is 0.9-1.1: 1. When the molar ratio of the diamine monomer to the dianhydride monomer is close to 1: 1, the maximization of the polymer molecular weight and the full progress of the reaction can be ensured.

[0017] Furthermore, the stirring reaction temperature is 20-30°C.

[0018] Furthermore, the molecular weight distribution width index M of the polyamic acid polymer solution is W / Mn=1.0-2.0. The molecular weight distribution width index is usually used to describe the dispersion degree of its molecular weight.

[0019] Furthermore, the weight average molecular weight of the polyamic acid polymer solution is 1.9×10 5 -4.1×10 5 Dalton. The tensile properties of the polyimide film obtained from the polyamic acid polymerization solution are highly dependent on the weight average molecular weight of the polyamic acid. The tensile properties will also be improved as the weight average molecular weight increases.

[0020] The present invention also provides a high-performance polyimide film, which is prepared by the preparation method as described above.

[0021] Beneficial effects of the present invention:

[0022] (1) The preparation method of the high-performance polyimide film proposed in the present invention is based on the chain extension reaction of polyamic acid. The reaction kinetics is considered from the perspective of the collision probability of monomer molecules. By fixing the proportion of the input amount of the reaction monomers, the collision probability of each polymer is simulated to be the same during the growth process, and the chain extension is induced under the condition that the chances of the polymer units tend to be equal. Under the condition that the amount of dianhydride monomer added decreases in proportion, the competitive behavior of the polymer units with different reaction activities for the dianhydride monomer is limited by the collision probability, which inhibits the disordered chain extension behavior and induces highly ordered chain extension. By adding in batches, the monomer feeding speed is reduced, so that the reactants (dianhydride monomers) can be fully mixed and diffused into the reaction system, making the reaction more uniform, and finally forming a PI precursor (polyamic acid) with high polymerization and narrow molecular weight distribution.

[0023] (2) The method provided by the present invention is simple and easy to operate, does not require additional equipment costs, has mild reaction conditions, and is easy to achieve industrial mass production. The mechanical properties of the polyimide film are improved by improving the raw material polymerization process. DETAILED DESCRIPTION

[0024] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in 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.

[0025] Example 1

[0026] Step 1: 592.8 g (2.96 mol) of 4,4'-diaminodiphenyl ether (ODA) was completely dissolved in 2800 g of N,N-dimethylacetamide (DMAC), and 323.1 g (1.48 mol) of pyromellitic dianhydride (PMDA) was added at 30°C, wherein the amount of pyromellitic dianhydride added was 50% of the total molar amount of 4,4'-diaminodiphenyl ether;

[0027] Step 2, after stirring and reacting at 30°C, add pyromellitic anhydride in 10 times while stirring, each addition amount is 50% mol of the previous addition amount, and the addition amount decreases proportionally, and each addition of pyromellitic anhydride is 25 minutes apart;

[0028] Step 3. After the addition is completed, the stirring reaction is continued for 25 minutes to obtain a polyamic acid polymerization liquid with a solid content of 31%. The polyamic acid polymerization liquid is vacuum degassed, and the degassed polyamic acid polymerization liquid is scraped onto a high-temperature resistant boronized glass plate with a scraper, placed in an oven and heated to 80°C for 20 minutes, then heated to 130°C for 20 minutes, and finally heated to 300°C for 20 minutes to complete the high-temperature imidization treatment, take out the glass plate and peel off the polyimide film from the glass plate to obtain a polyimide film.

[0029] The specific addition amount of pyromellitic dianhydride is shown in Table 1.

[0030] Table 1

[0031] Number of times of adding pyromellitic anhydride Addition amount / g 1st time 323.1 2nd 161.55 3rd 80.78 4th 40.39 5th 20.19 6th 10.10 7th 5.05 8th 2.52 9th 1.26 10th 0.63 11th 0.32

[0032] According to the added amount here, the total added amount of pyromellitic anhydride is 645.89 g, and the molar ratio of 4,4'-diaminodiphenyl ether to pyromellitic anhydride is 2.96:2.96=1:1.

[0033] Example 2

[0034] The only difference from Example 1 is that the amount of 323.1 g (1.48 mol) of pyromellitic anhydride (PMDA) added in step 1 is adjusted to 303.45 g (1.3912 mol) of pyromellitic anhydride (PMDA), and the amount of pyromellitic anhydride added is 47% of the total molar amount of 4,4'-diaminodiphenyl ether; in step 2, pyromellitic anhydride is added in 10 times, and the amount added each time is 47% mol of the previous amount. The specific steps are as follows:

[0035] Step 1: 592.8 g (2.96 mol) of 4,4'-diaminodiphenyl ether (ODA) was completely dissolved in 2800 g of N,N-dimethylacetamide (DMAC), and 303.45 g (1.3912 mol) of pyromellitic dianhydride (PMDA) was added at 30°C, wherein the amount of pyromellitic dianhydride added was 47% of the total molar amount of 4,4'-diaminodiphenyl ether;

[0036] Step 2, after stirring and reacting at 30°C, add pyromellitic anhydride in 10 times while stirring, each adding amount is 47% mol of the previous addition amount, and the addition amount is decreased proportionally, and each addition of pyromellitic anhydride is 25 minutes apart;

[0037] Step 3. After the addition is completed, the stirring reaction is continued for 25 minutes to obtain a polyamic acid polymerization liquid with a solid content of 29%. The polyamic acid polymerization liquid is vacuum degassed, and the degassed polyamic acid polymerization liquid is scraped onto a high-temperature resistant boronized glass plate with a scraper, placed in an oven and heated to 80°C for 20 minutes, then heated to 130°C for 20 minutes, and finally heated to 300°C for 20 minutes to complete the high-temperature imidization treatment, the glass plate is taken out and the polyimide film is peeled off from the glass plate to obtain a polyimide film.

[0038] The specific addition amount of pyromellitic dianhydride is shown in Table 2.

[0039] Table 2

[0040] Number of times of adding pyromellitic anhydride Addition amount / g 1st time 303.45 2nd 142.62 3rd 67.03 4th 31.50 5th 14.81 6th 6.96 7th 3.27 8th 1.54 9th 0.72 10th 0.34 11th 0.16

[0041] According to the added amount here, the total added amount of pyromellitic anhydride is 572.4 g, and the molar ratio of 4,4'-diaminodiphenyl ether to pyromellitic anhydride is 2.96:2.62≈1.1:1.

[0042] Example 3

[0043] The only difference from Example 1 is that the amount of 323.1 g (1.48 mol) of pyromellitic anhydride (PMDA) added in step 1 is adjusted to 335.73 g (1.5392 mol) of pyromellitic anhydride (PMDA), and the amount of pyromellitic anhydride added is 52% of the total molar amount of 4,4'-diaminodiphenyl ether; in step 2, pyromellitic anhydride is added in 10 times, and the amount added each time is 52% mol of the previous amount. The specific steps are as follows:

[0044] Step 1: 592.8 g (2.96 mol) of 4,4'-diaminodiphenyl ether (ODA) was completely dissolved in 2800 g of N,N-dimethylacetamide (DMAC), and 335.73 g (1.5392 mol) of pyromellitic anhydride (PMDA) was added at 30°C, wherein the amount of pyromellitic anhydride added was 52% of the total molar amount of 4,4'-diaminodiphenyl ether;

[0045] Step 2, after stirring and reacting at 30°C, add pyromellitic anhydride in 10 times while stirring, each adding amount is 52% mol of the previous addition amount, and the addition amount decreases proportionally, and each addition of pyromellitic anhydride is 25 minutes apart;

[0046] Step 3. After the addition is completed, the stirring reaction is continued for 25 minutes to obtain a polyamic acid polymerization liquid with a solid content of 32%. The polyamic acid polymerization liquid is vacuum degassed, and the degassed polyamic acid polymerization liquid is scraped onto a high-temperature resistant boronized glass plate with a scraper, placed in an oven and heated to 80°C for 20 minutes, then heated to 130°C for 20 minutes, and finally heated to 300°C for 20 minutes to complete the high-temperature imidization treatment, take out the glass plate and peel off the polyimide film from the glass plate to obtain a polyimide film.

[0047] The specific addition amount of pyromellitic dianhydride is shown in Table 3.

[0048] Table 3

[0049] Number of times of adding pyromellitic anhydride Addition amount / g 1st time 335.73 2nd 174.58 3rd 90.78 4th 47.21 5th 24.55 6th 12.77 7th 6.64 8th 3.45 9th 1.79 10th 0.93 11th 0.48

[0050] According to the added amount here, the total added amount of pyromellitic anhydride is 698.91 g, and the molar ratio of 4,4'-diaminodiphenyl ether to pyromellitic anhydride is 2.96:3.20≈0.9:1.

[0051] Example 4

[0052] The difference from Example 1 is that in step 2, pyromellitic dianhydride is added in 7 times, and the amount added each time is 50% mol of the amount added in the previous time. The specific steps are as follows:

[0053] Step 1: 592.8 g (2.96 mol) of 4,4'-diaminodiphenyl ether (ODA) was completely dissolved in 2800 g of N,N-dimethylacetamide (DMAC), and 323.1 g (1.48 mol) of pyromellitic dianhydride (PMDA) was added at 30°C, wherein the amount of pyromellitic dianhydride added was 50% of the total molar amount of 4,4'-diaminodiphenyl ether;

[0054] Step 2, after stirring and reacting at 30°C, add pyromellitic anhydride in 7 times while stirring, each addition amount is 50% mol of the previous addition amount, and the addition amount decreases proportionally, and each addition of pyromellitic anhydride is 25 minutes apart;

[0055] Step 3. After the addition is completed, the stirring reaction is continued for 25 minutes to obtain a polyamic acid polymerization liquid with a solid content of 31%. The polyamic acid polymerization liquid is vacuum degassed, and the degassed polyamic acid polymerization liquid is scraped onto a high-temperature resistant boronized glass plate with a scraper, placed in an oven and heated to 80°C for 20 minutes, then heated to 130°C for 20 minutes, and finally heated to 300°C for 20 minutes to complete the high-temperature imidization treatment, take out the glass plate and peel off the polyimide film from the glass plate to obtain a polyimide film.

[0056] The specific addition amount of pyromellitic dianhydride is shown in Table 4.

[0057] Table 4

[0058] Number of times of adding pyromellitic anhydride Addition amount / g 1st time 323.1 2nd 161.55 3rd 80.78 4th 40.39 5th 20.19 6th 10.10 7th 5.05 8th 2.52

[0059] According to the added amount here, the total added amount of pyromellitic anhydride is 643.68 g, and the molar ratio of 4,4'-diaminodiphenyl ether to pyromellitic anhydride is 2.96:2.95≈1:1.

[0060] Example 5

[0061] The difference from Example 1 is that in step 2, pyromellitic dianhydride is added in 12 times, and the amount added each time is 50% mol of the amount added in the previous time. The specific steps are as follows:

[0062] Step 1: 592.8 g (2.96 mol) of 4,4'-diaminodiphenyl ether (ODA) was completely dissolved in 2800 g of N,N-dimethylacetamide (DMAC), and 323.1 g (1.48 mol) of pyromellitic dianhydride (PMDA) was added at 30°C, wherein the amount of pyromellitic dianhydride added was 50% of the total molar amount of 4,4'-diaminodiphenyl ether;

[0063] Step 2, after stirring and reacting at 30°C, add pyromellitic anhydride in 12 times while stirring, each addition amount is 50% mol of the previous addition amount, and the addition amount decreases proportionally, and each addition of pyromellitic anhydride is 25 minutes apart;

[0064] Step 3. After the addition is completed, the stirring reaction is continued for 25 minutes to obtain a polyamic acid polymerization liquid with a solid content of 31%. The polyamic acid polymerization liquid is vacuum degassed, and the degassed polyamic acid polymerization liquid is scraped onto a high-temperature resistant boronized glass plate with a scraper, placed in an oven and heated to 80°C for 20 minutes, then heated to 130°C for 20 minutes, and finally heated to 300°C for 20 minutes to complete the high-temperature imidization treatment, take out the glass plate and peel off the polyimide film from the glass plate to obtain a polyimide film.

[0065] The specific addition amount of pyromellitic dianhydride is shown in Table 5.

[0066] Table 5

[0067]

[0068]

[0069] According to the added amount here, the total added amount of pyromellitic anhydride is 646.13 g, and the molar ratio of 4,4'-diaminodiphenyl ether to pyromellitic anhydride is 2.96:2.96=1:1.

[0070] Example 6

[0071] The difference from Example 1 is that the addition of 323.1 g (1.48 mol) of pyromellitic anhydride (PMDA) in step 1 is adjusted to 329.27 g (1.5096 mol) of pyromellitic anhydride (PMDA), and the addition amount of pyromellitic anhydride is 51% of the total molar amount of 4,4'-diaminodiphenyl ether; in step 2, pyromellitic anhydride is added in 4 times, and the addition amount each time is 51% mol of the previous addition amount. The specific steps are as follows:

[0072] Step 1: 592.8 g (2.96 mol) of 4,4'-diaminodiphenyl ether (ODA) was completely dissolved in 2800 g of N,N-dimethylacetamide (DMAC), and 329.27 g (1.5096 mol) of pyromellitic anhydride (PMDA) was added at 30°C, wherein the amount of pyromellitic anhydride added was 51% of the total molar amount of 4,4'-diaminodiphenyl ether;

[0073] Step 2, after stirring and reacting at 30°C, add pyromellitic anhydride in 4 times while stirring, each adding amount is 51% mol of the previous addition amount, and the addition amount is decreased proportionally, and each addition of pyromellitic anhydride is 25 minutes apart;

[0074] Step 3. After the addition is completed, the stirring reaction is continued for 25 minutes to obtain a polyamic acid polymerization liquid with a solid content of 31%. The polyamic acid polymerization liquid is vacuum degassed, and the degassed polyamic acid polymerization liquid is scraped onto a high-temperature resistant boronized glass plate with a scraper, placed in an oven and heated to 80°C for 20 minutes, then heated to 130°C for 20 minutes, and finally heated to 300°C for 20 minutes to complete the high-temperature imidization treatment, take out the glass plate and peel off the polyimide film from the glass plate to obtain a polyimide film.

[0075] The specific addition amount of pyromellitic dianhydride is shown in Table 6.

[0076] Table 6

[0077]

[0078]

[0079] According to the added amount here, the total added amount of pyromellitic anhydride is 648.8 g, and the molar ratio of 4,4'-diaminodiphenyl ether to pyromellitic anhydride is 2.96:2.97≈1:1.

[0080] Example 7

[0081] The difference from Example 1 is that the amount of 4,4'-diaminodiphenyl ether (ODA) added in step 1 is increased, and the specific steps are as follows:

[0082] Step 1: 1185.43 g (5.92 mol) of 4,4'-diaminodiphenyl ether (ODA) was completely dissolved in 5600 g of N,N-dimethylacetamide (DMAC), and 645.64 g (2.96 mol) of pyromellitic anhydride (PMDA) was added at 30°C, wherein the amount of pyromellitic anhydride added was 50% of the total molar amount of 4,4'-diaminodiphenyl ether;

[0083] Step 2, after stirring and reacting at 30°C, add pyromellitic anhydride in 10 times while stirring, each addition amount is 50% mol of the previous addition amount, and the addition amount decreases proportionally, and each addition of pyromellitic anhydride is 25 minutes apart;

[0084] Step 3. After the addition is completed, the stirring reaction is continued for 25 minutes to obtain a polyamic acid polymerization liquid with a solid content of 31%. The polyamic acid polymerization liquid is vacuum degassed, and the degassed polyamic acid polymerization liquid is scraped onto a high-temperature resistant boronized glass plate with a scraper, placed in an oven and heated to 80°C for 20 minutes, then heated to 130°C for 20 minutes, and finally heated to 300°C for 20 minutes to complete the high-temperature imidization treatment, take out the glass plate and peel off the polyimide film from the glass plate to obtain a polyimide film.

[0085] The specific addition amount of pyromellitic dianhydride is shown in Table 7.

[0086] Table 7

[0087]

[0088]

[0089] According to the added amount here, the total added amount of pyromellitic anhydride is 1290.92 g, and the molar ratio of 4,4'-diaminodiphenyl ether to pyromellitic anhydride is 5.92:5.92=1:1.

[0090] Example 8

[0091] The difference from Example 1 is that in step 1, 4,4'-diaminodiphenyl ether is replaced by p-phenylenediamine, and pyromellitic acid dianhydride is replaced by 3,3',4,4'-biphenyltetracarboxylic acid dianhydride. The specific steps are as follows.

[0092] Step 1: 324 g (3.0 mol) of p-phenylenediamine (PPD) was completely dissolved in 2800 g of N,N-dimethylacetamide (DMAC), and 441 g (1.50 mol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) was added at 30°C, wherein the amount of 3,3',4,4'-biphenyltetracarboxylic dianhydride added was 50% of the total molar amount of p-phenylenediamine;

[0093] Step 2, after stirring and reacting at 30°C, add 3,3',4,4'-biphenyltetracarboxylic acid dianhydride in 10 times while stirring, each addition amount is 50% mol of the previous addition amount, and the addition amount decreases proportionally, and each addition of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride is 25 minutes apart;

[0094] Step 3. After the addition is completed, the stirring reaction is continued for 25 minutes to obtain a polyamic acid polymerization liquid with a solid content of 30%. The polyamic acid polymerization liquid is vacuum degassed, and the degassed polyamic acid polymerization liquid is scraped onto a high-temperature resistant boronized glass plate with a scraper, placed in an oven and heated to 80°C for 20 minutes, then heated to 130°C for 20 minutes, and finally heated to 300°C for 20 minutes to complete the high-temperature imidization treatment, take out the glass plate and peel off the polyimide film from the glass plate to obtain a polyimide film.

[0095] The specific addition amount of 3,3',4,4'-biphenyltetracarboxylic dianhydride is shown in Table 8.

[0096] Table 8

[0097] 3,3',4,4'-Biphenyltetracarboxylic dianhydride feeding times Addition amount / g 1st time 441 2nd 220.5 3rd 110.25 4th 55.13 5th 27.56 6th 13.78 7th 6.89 8th 3.45 9th 1.72 10th 0.86 11th 0.43

[0098] According to the added amount here, the total added amount of 3,3',4,4'-biphenyltetracarboxylic dianhydride is 881.57 g, and the molar ratio of p-phenylenediamine to 3,3',4,4'-biphenyltetracarboxylic dianhydride is 3.0:3.0=1:1.

[0099] Comparative Example 1

[0100] The difference from Example 1 is that the addition of 323.1 g (1.48 mol) of pyromellitic anhydride (PMDA) in step 1 is adjusted to 129.18 g (0.59 mol) of pyromellitic anhydride (PMDA), and the addition amount of pyromellitic anhydride is 20% of the total molar amount of 4,4'-diaminodiphenyl ether; and in step 2, pyromellitic anhydride is added in 4 times. The specific addition amount of pyromellitic anhydride is shown in Table 9.

[0101] Table 9

[0102] Number of times of adding pyromellitic anhydride Addition amount / g 1st time 129.18 2nd 129.18 3rd 129.18 4th 129.18 5th 129.18

[0103] According to the added amount here, the total added amount of pyromellitic anhydride is 645.9 g, and the molar ratio of 4,4'-diaminodiphenyl ether to pyromellitic anhydride is 2.96:2.96=1:1.

[0104] Comparative Example 2

[0105] The difference from Example 1 is that the addition of 323.1 g (1.48 mol) of pyromellitic anhydride (PMDA) in step 1 is adjusted to 58.89 g (0.27 mol) of pyromellitic anhydride (PMDA), and the addition amount of pyromellitic anhydride is 9% of the total molar amount of 4,4'-diaminodiphenyl ether; and in step 2, pyromellitic anhydride is added in 10 times. The specific addition amount of pyromellitic anhydride is shown in Table 10.

[0106] Table 10

[0107] Number of times of adding pyromellitic anhydride Addition amount / g 1st time 58.89 2nd 58.89 3rd 58.89 4th 58.89 5th 58.89 6th 58.89 7th 58.89 8th 58.89 9th 58.89 10th 58.89 11th 58.89

[0108] According to the added amount here, the total added amount of pyromellitic anhydride is 647.79 g, and the molar ratio of 4,4'-diaminodiphenyl ether to pyromellitic anhydride is 2.96:2.97≈1:1.

[0109] Comparative Example 3

[0110] The difference from Example 3 is that the addition of 335.73 g (1.5392 mol) of pyromellitic anhydride (PMDA) in step 1 is adjusted to 63.25 g (0.29 mol) of pyromellitic anhydride (PMDA), and the addition amount of pyromellitic anhydride is 9.8% of the total molar amount of 4,4'-diaminodiphenyl ether; and the addition of pyromellitic anhydride in step 2 is divided into 10 times. The specific addition amount of pyromellitic anhydride is shown in Table 11.

[0111] Table 11

[0112]

[0113]

[0114] According to the added amount here, the total added amount of pyromellitic anhydride is 695.75 g, and the molar ratio of 4,4'-diaminodiphenyl ether to pyromellitic anhydride is 2.96:3.19≈0.9:1.

[0115] The performance tests were performed on the polyamic acid polymer solutions and polyimide films prepared in Examples 1 to 8 and Comparative Examples 1 to 3. The results are shown in Table 12.

[0116] Table 12

[0117]

[0118] As can be seen from Table 12, the molecular weight distribution of the polymer in the polyamic acid polymer solution prepared in Example 1 is narrow, the polymer high molecular weight polymer accounts for the majority, and the relatively low molecular weight polymer accounts for the minority, forming a very narrow molecular weight distribution, which undoubtedly provides a very good foundation for the uniformity of the physical and chemical properties after subsequent processing into a film. The mechanical properties of the prepared polyimide film are excellent, which also proves the effectiveness of the present implementation method in controlling the chain extension reaction behavior from the perspective of collision probability. Compared with Example 1, Example 2 is adjusted from 50% to 47% in each batch, and the molar ratio of 4,4'-diaminodiphenyl ether and pyromellitic dianhydride is adjusted from 1:1 to 1.1:1. The weight average molecular weight of the polyamic acid polymer solution prepared in Example 2 is lower than that in Example 1. When the proportion of diamine monomer is slightly higher than that of dianhydride monomer, since the activity of diamine monomer is higher than that of dianhydride monomer, in the case of excessive diamine, the reaction rate is accelerated, resulting in a slight decrease in the molecular weight of the polymer chain. When the proportion of each batch is reduced, there is part of disordered chain extension in its actual reaction, and the molecular weight distribution width index increases, resulting in a decrease in the elongation at break of the polyimide film. Compared with Example 1, Example 3 is adjusted from 50% to 52% in each batch, and the molar ratio of 4,4'-diaminodiphenyl ether and pyromellitic dianhydride is adjusted from 1:1 to 0.9:1. The weight average molecular weight of the polyamic acid in Example 3 is higher than that in Example 1. During synthesis, since the dianhydride monomer is easy to deliquesce and reduce the reaction activity, the slight excess of dianhydride monomer in Example 3 can ensure that the dianhydride monomer and diamine monomer participating in the reaction are equivalent, and the molecular weight of the polyamic acid in the polyamic acid polymer solution obtained by the reaction is high, and the fracture strength of the polyimide film reaches 131.7MPa. When the proportion of each batch in Example 3 is reduced compared with Example 1, there is part of disordered chain extension in its actual reaction, as in Example 2, and the molecular weight distribution width index increases, resulting in uneven quality of the polyimide film prepared in Example 3, and the elongation at break is not as good as that in Example 1. In Example 4, the number of additions of pyromellitic anhydride was reduced. Since the amount of pyromellitic anhydride added was slightly lower than that in Example 1, the molecular weight of the polymer was lower than that in Example 1. In Example 5, the number of additions of pyromellitic anhydride was increased. A small amount of dianhydride monomer added in the latter stage of the reaction can promote the forward reaction, increase the molecular weight of polyamic acid, and improve the performance of the polyimide film compared with Example 1. In Example 6, the addition ratio of pyromellitic anhydride was adjusted to 51%, and the number of additions was reduced to ensure that the molar ratio of 4,4'-diaminodiphenyl ether and pyromellitic anhydride was 1:1. According to the molecular weight statistical results, its molecular weight was lower than that in Example 1. The reduction in molecular weight will cause the intermolecular force to be further weakened, and the mechanical properties of the polyimide film obtained subsequently will also be slightly reduced.In Example 7, the dosage of the reaction monomer was increased, and the adaptive scale-up experiment was performed. In Example 8, different monomers were used for synthesis. At this time, the molecular weight and distribution of the prepared polyamic acid were not significantly different from those in Example 1, and the performance of the obtained polyimide film was not much different. This shows that even in the scale-up experiment or when different types of monomers react, under the same feeding ratio and number of times, the synthesized polyamic acid still has a higher molecular weight and a narrower molecular weight distribution, and the polyimide film prepared using the polyamic acid polymerization solution has good mechanical properties.

[0119] Comparative Example 1 divides the total amount of PMDA to be invested into 5 equal parts, and the molecular weight of the obtained polyamic acid is relatively low, indicating that there are more low-molecular-weight polymers. Due to the small number of times and large amounts of dianhydride monomers, the collision reaction rate of diamine monomers and dianhydride monomers is accelerated, resulting in the appearance of many oligomers, and it is difficult to form long-chain molecules. The polyamic acid polymer solution obtained in Comparative Example 2 was tested, and its Mw / Mn value was greater than 3, indicating that even with the same number of additions as in Example 1, it is difficult to ensure the orderly chain extension during the reaction process when adding equally, resulting in a wider molecular weight distribution and a lower molecular weight. Comparative Example 3 is based on Example 3, and when the molar ratio of 4,4'-diaminodiphenyl ether and pyromellitic anhydride is 0.9:1, pyromellitic anhydride is added in 11 equal parts, and its molecular weight statistical results show that compared with Example 3, its molecular weight distribution is wider, and the molecular weight is lower than that of Example 3. From the perspective of the mechanical properties of the polyimide film, the performance of the polyimide film of the embodiment is significantly improved compared with the comparative example.

[0120] The following conclusions can be drawn from the results of the above embodiments: the width of the molecular weight distribution depends on whether the chain extension process is disordered or ordered, and the ordered behavior is achieved by homogenizing the intermolecular reaction rate. According to the embodiments of the present invention, batch-wise and fixed reaction monomer input ratios can successfully guide the ordered chain extension behavior in the polymerization process, thereby ultimately achieving a high molecular weight and narrow distribution polyimide precursor (polyamic acid), so that the polyimide film obtained after high-temperature imidization treatment of the polyamic acid has excellent mechanical properties.

[0121] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0122] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high-performance polyimide film, characterized in that: The following steps are involved: Step 1, firstly completely dissolve the diamine monomer in a non-protonic polar solvent, and then add the dianhydride monomer, wherein the amount of the dianhydride monomer added is 47-52% of the total molar amount of the diamine monomer; Step 2: After the reaction is stirred, add the dianhydride monomer in 4-12 times while stirring, and the amount added each time is 47-52 mol% of the previous amount, and the amount added decreases proportionally; Step 3: After the reaction is completed, a polyamic acid polymer solution is obtained, vacuum degassing and coating are performed, and a polyimide film is obtained by high-temperature imidization treatment; The molar ratio of diamine monomer to dianhydride monomer in the raw material of the polyamic acid polymerization liquid is 0.9-1.1:

1.

2. The method for preparing a high-performance polyimide film according to claim 1, characterized in that: The diamine monomer is one of 4,4'-diaminodiphenyl ether and p-phenylenediamine.

3. The method for preparing a high-performance polyimide film according to claim 1, characterized in that: The dianhydride monomer is one of pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride.

4. The method for preparing a high-performance polyimide film according to claim 1, characterized in that: The aprotic polar solvent is one of N,N-dimethylacetamide, N,N-dimethylformamide and N-methylpyrrolidone.

5. The method for preparing a high-performance polyimide film according to claim 1, characterized in that: The solid content of the polyamic acid polymer solution is 29-32%.

6. The method for preparing a high-performance polyimide film according to claim 1, characterized in that: In step 2, the dianhydride monomer is added each time with an interval of 20-30 minutes.

7. The method for preparing a high-performance polyimide film according to claim 1, characterized in that: The temperature of the stirring reaction is 20-30°C.

8. The method for preparing a high-performance polyimide film according to claim 1, characterized in that: The molecular weight distribution width index M of the polyamic acid polymer solution W / Mn=1.0-2.

0.

9. The method for preparing a high-performance polyimide film according to claim 1, characterized in that: The weight average molecular weight of the polyamic acid polymer solution is 1.9×10 5 -4.1×10 5 Dalton.

10. A high performance polyimide film, characterized in that: The preparation is obtained by the preparation method according to any one of claims 1 to 9.

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