Polyamide acid solution, method for preparing the same, and raw material composition for preparing the same

Abstract

The present invention relates to a polyamic acid solution and a method for preparing the same, and a raw material composition for preparing the same. The present invention is capable of preparing a polyamic acid solution having high solid content and low kinetic viscosity, which is easy to process and has high stability, by using a specific additive in a simple manner. A method for preparing a polyamic acid solution, which comprises a step of adding a combination of pectin and dimethyl adipate as an additive during the reaction of an aromatic dianhydride and a diamine.

Description

Technical Field

[0001] This invention belongs to the field of polyamic acid synthesis, and relates to polyamic acid solutions, their preparation methods, and raw material compositions for preparing polyamic acid solutions. Background Technology

[0002] Polyimide is a heterocyclic polymer (R-CO-NH-CO-R') containing imide groups in its molecular structure. It possesses excellent mechanical properties, resistance to high and low temperatures, and dimensional stability. Products are typically available in films, fibers, resins, foams, and composite materials, and are now widely used in electronics, electrical engineering, machinery, aerospace, communications, and flexible displays. Polyimide is usually prepared using a two-step process: aromatic dianhydride and diamine are polymerized in an aprotic polar solvent to obtain a polyamic acid solution, which is then subjected to heat treatment or chemical imidization to obtain polyimide. Therefore, the characteristics of the polyamic acid precursor determine the quality of the final product.

[0003] When preparing coatings and films using methods such as spraying, casting, and spinning, the solid content and kinetic viscosity of polyamic acid slurry are crucial factors affecting processability. Polyamic acid molecules readily form numerous hydrogen bonds within and between molecular chains, and the ionization of carboxylic acid groups enhances the polyelectrolyte effect. This results in slurries with high solid content typically exhibiting very high kinetic viscosity, sometimes even gelling, which is detrimental to subsequent processing applications. Reducing the solid content can decrease the slurry's kinetic viscosity to some extent, but this increases solvent consumption, affecting product quality and reducing production efficiency. To address the poor flowability of slurries with high solid content, CN101558102A discloses a method for controlling the water content of the reaction system; CN106589371A proposes adding tetracarboxylic acid to the dianhydride and diamine reaction system to control polyamic acid viscosity, but this method requires operation under a nitrogen atmosphere, increasing reaction complexity; CN104292459A discloses a method for adjusting viscosity by adding polysiloxane-based thickeners, but this method suffers from problems such as requiring multiple additions, solvent replenishment, and long waiting times for addition.

[0004] Furthermore, polyamic acid undergoes spontaneous degradation during storage, leading to a decrease in its intrinsic viscosity. The root cause of this degradation is the nucleophilic addition of the carboxylic acid hydroxyl groups to the amide carbonyl groups within the polyamic acid, resulting in a depolymerization reaction. The presence of moisture in the system causes the hydrolysis of the anhydride end groups formed during molecular chain depolymerization, creating two carboxylic acid groups. This irreversible reaction alters the properties of the polyamic acid, resulting in a short shelf life and poor batch stability. Current methods to extend the shelf life of polyamic acid include dry preparation, ultra-low temperature storage, adding molecular sieves to absorb water, binding the hydrogen atoms of the carboxylic acid groups (including adding organic bases and carboxyl esterification), and molecular chain end capping. However, these methods are cumbersome, involve highly toxic reagents, and have high processing costs. Therefore, synthesizing polyamic acid slurries with high solids content, low kinetic viscosity, ease of subsequent material processing, good storage, and high stability through simple preparation methods is a pressing problem to be solved.

[0005] CN103788651A discloses a method for preparing a polyamic acid solution with low apparent viscosity, wherein 5% to 40% (by weight of the polyamic acid) of trimethylchlorosilane is added to the polyamic acid solution, and the mixture is stirred at room temperature for 1 to 5 hours to obtain a polyamic acid solution with an apparent viscosity of 0.2 to 1.5 kPa. However, in this method, the content of trimethylchlorosilane as an additive is large, which may affect subsequent material processing and necessitate the removal of the additive.

[0006] CN106589368A discloses a method for preparing a polyamic acid composition with controllable viscosity, wherein the viscosity is controlled by adding tetracarboxylic acid in controlled proportions and adding tetracarboxylic dianhydride in batches. However, this method requires operation under a nitrogen atmosphere, increasing the difficulty of experimental operation, and the method does not optimize the stability of polyamic acid during storage.

[0007] CN115678010A discloses a method for obtaining polyamic acid through the polycondensation reaction of dianhydrides containing flexible chain structures and diamines containing nitrogen-containing heteroaromatic rings. In this method, the diamine containing the nitrogen-containing heteroaromatic ring is added to a solvent, followed by the addition of the dianhydride containing the flexible chain structure in three batches. This method not only requires the use of specific dianhydrides and diamines but also necessitates batch feeding, increasing the number of operational steps. Furthermore, this method does not investigate the viscosity and storage stability of the polyamic acid solution. Summary of the Invention

[0008] As mentioned above, the prior art has not provided a simple method for preparing polyamic acid solutions with controllable viscosity and high stability.

[0009] The technical problem to be solved by the present invention is to provide a method for preparing a polyamic acid solution with high solid content and low kinetic viscosity, which is easy to process, easy to store and highly stable, using simple means.

[0010] The inventors discovered that by introducing specific additives to synthesize polyamic acid solutions, the above-mentioned technical problems can be solved, thus completing the present invention.

[0011] Specifically, the present invention provides a method for preparing a polyamic acid solution, which includes the step of adding a combination of pectin and dimethyl adipate as an auxiliary agent during the reaction of aromatic dianhydride and diamine.

[0012] In the above technical solution, preferably, the method includes the following steps:

[0013] (I) The solvent, auxiliaries, and one of the diamine and aromatic dianhydrides are added to the reaction vessel for dissolution; and

[0014] (II) Add the diamine and another of the aromatic dianhydrides to the solution obtained in step (I) to react and obtain a polyamic acid solution.

[0015] The adjuvant is a combination of pectin and dimethyl adipate.

[0016] In the above technical solution, preferably, the mass ratio of pectin to dimethyl adipate in the auxiliary agent is 1:0.05-0.2.

[0017] In the above technical solution, preferably, a diamine is added in step (I) and an aromatic dianhydride is added in step (II).

[0018] In the above technical solution, preferably, the solvent is an aprotic polar solvent.

[0019] In the above technical solution, preferably, the aprotic polar solvent is at least one selected from the group consisting of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide and hexamethylphosphoric triamine.

[0020] In the above technical solution, preferably, the diamine is at least one selected from the group consisting of p-phenylenediamine, 4,4'-diaminodiphenyl ether, hydroquinone diether diamine, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenylmethane, ethylenediamine, 1,6-hexanediamine and bisphenol A diether diamine.

[0021] In the above technical solution, preferably, the aromatic dianhydride is at least one selected from the group consisting of pyromellitic dianhydride, biphenyl dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, triphenyl diether dianhydride, diphenyl ether dianhydride, diphenyl sulfide dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, hydroquinone diether dianhydride, hexafluoro dianhydride, resorcinol diether dianhydride, and bisphenol A diether dianhydride.

[0022] In the above technical solution, preferably, the molar ratio of the diamine to the aromatic dianhydride is 1:0.98 to 1.02.

[0023] In the above technical solution, preferably, the amount of pectin added is 0.05 to 2% by mass relative to 100% by mass of the aprotic polar solvent.

[0024] In addition, the present invention also provides a polyamic acid solution, which is obtained by the preparation method of the present invention described above.

[0025] In the above technical solution, preferably, the kinetic viscosity of the polyamic acid solution is below 15,000 centipoise, more preferably below 10,000 centipoise.

[0026] In the above technical solution, preferably, the solid content of the polyamic acid solution is 10 wt% or more.

[0027] In the above technical solution, preferably, the intrinsic viscosity of the polyamic acid solution is 1.60 dL / g or higher.

[0028] Furthermore, the present invention also provides a raw material composition for preparing a polyamic acid solution, comprising at least a solvent, an auxiliary agent, and one of a diamine and an aromatic dianhydride, wherein the auxiliary agent is a combination of pectin and dimethyl adipate.

[0029] In the above technical solution, preferably, the raw material composition is used to prepare a polyamic acid solution using the preparation method of the present invention.

[0030] The effects of the invention

[0031] According to the method for preparing polyamic acid solution of the present invention, a polyamic acid solution with high solid content and low kinetic viscosity, which is easy to process in subsequent materials, easy to store, and has high stability can be prepared. Attached Figure Description

[0032] Figure 1 This is a graph showing the change in intrinsic viscosity of the polyamic acid solution obtained in Example 3 when stored at 10°C. Detailed Implementation

[0033] This invention relates to a method for preparing a polyamic acid solution, which includes the step of adding a combination of pectin and dimethyl adipate as an adjuvant during the reaction of aromatic dianhydride and diamine.

[0034] Specifically, the preparation method of the present invention may include the following steps:

[0035] (I) The solvent, auxiliaries, and one of the diamine and aromatic dianhydrides are added to the reaction vessel for dissolution; and

[0036] (II) Add the other of the aromatic dianhydride and diamine to the solution obtained in step (I) and react to obtain a polyamic acid solution.

[0037] The adjuvant is a combination of pectin and dimethyl adipate.

[0038] The preparation method of the present invention can produce a polyamic acid solution with controllable viscosity and high stability by using specific additives.

[0039] In this invention, aprotic polar solvents are preferably used as solvents. N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, and hexamethylphosphoric triamine are preferred as aprotic polar solvents.

[0040] In this invention, aromatic or aliphatic diamines are preferably used as diamines, particularly p-phenylenediamine, 4,4'-diaminodiphenyl ether, hydroquinone diether diamine, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenylmethane, ethylenediamine, 1,6-hexanediamine, and bisphenol A diether diamine, and more preferably p-phenylenediamine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenylmethane, ethylenediamine, and 1,6-hexanediamine.

[0041] In this invention, the aromatic dianhydrides preferably used are pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, triphenyl diether dianhydride, diphenyl ether dianhydride, diphenyl sulfide dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, hydroquinone diether dianhydride, hexafluoro dianhydride, resorcinol diether dianhydride, and bisphenol A diether dianhydride. More preferably, pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, diphenyl sulfide dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, hexafluoro dianhydride, and bisphenol A diether dianhydride are used.

[0042] Regarding the molar ratio of diamine and aromatic dianhydride, the molar ratio of diamine to aromatic dianhydride can be 1:0.97 to 1.03, preferably 1:0.98 to 1.02, more preferably 1:0.99 to 1.01, and most preferably 1:0.995 to 1.01.

[0043] Furthermore, regarding the total amount of diamine and aromatic dianhydride used, relative to a 100% mass reaction system, the total weight of diamine and aromatic dianhydride can be 3% to 50%, preferably 5% to 40%, and more preferably 10% to 30%.

[0044] In this invention, an auxiliary agent is added to the reaction system for the polymerization of diamine and aromatic dianhydride. This auxiliary agent is a combination of pectin and dimethyl adipate.

[0045] Pectin is primarily an acidic heteropolysaccharide composed of D-galacturonic acid linked by α-1,4-glycosidic bonds. It is commonly used as a food additive in food, health products, and some cosmetics, and has the structure shown in formula (1). The inventors discovered that adding pectin can reduce the kinetic viscosity of polyamic acid solutions. This is because the high-molecular-weight acids in pectin can increase free hydrogen ions, weaken the intermolecular and intramolecular hydrogen bonding of polyamic acid, and simultaneously shield the polyelectrolyte effect of polyamic acid, thus significantly reducing the kinetic viscosity of the system. Furthermore, combining pectin with dimethyl adipate can improve the stability of polyamic acid solutions. This is because dimethyl adipate can undergo hydrolysis in the presence of pectin, increasing pectin solubility while generating carboxylic acid groups, products of the polyamic acid depolymerization reaction, thereby reducing the reaction rate of the reverse reaction and extending shelf life. It should be noted that since pectin and dimethyl adipate can be removed by dissolution, they do not affect the subsequent material properties.

[0046]

[0047] Regarding the amount of additives, relative to 100% by mass of the aprotic polar solvent used in the reaction system, the amount of pectin added is 0.01–5% by mass, preferably 0.03–3% by mass, more preferably 0.05–2% by mass, and most preferably 0.1–1% by mass. The amount of dimethyl adipate added is preferably less than that of pectin. The mass ratio of pectin to dimethyl adipate can be 1:0.01–0.5, preferably 1:0.03–0.4, more preferably 1:0.05–0.3, and most preferably 1:0.07–0.2.

[0048] In the preparation method of the present invention, in step (I), an aprotic polar solvent, an auxiliary agent, and one of the diamine and aromatic dianhydride are added to a reaction vessel for dissolution. In step (II), the other of the diamine and aromatic dianhydride is added to the solution obtained in step (I) for reaction to obtain a polyamic acid solution. There is no particular limitation on the order of addition of the diamine and aromatic dianhydride. Those skilled in the art are familiar with methods such as the forward addition method (adding the diamine first and then the aromatic dianhydride), the reverse addition method (adding the aromatic dianhydride first and then the diamine), and the simultaneous addition method. The forward addition method is preferred, that is, the diamine is added in step (I) and the aromatic dianhydride is added in step (II).

[0049] In step (II), when adding diamine and aromatic dianhydride components that were not added in step (I), they can be added all at once or in batches. When adding in batches, they can be added in three or more batches.

[0050] There is no particular limitation on the system temperature, as long as it is a temperature that allows the diamine and aromatic dianhydride to dissolve and the polymerization reaction to proceed. The temperatures in steps (I) and (II) can be the same or different. The system temperature in steps (I) and (II) can be -20 to 50°C, preferably -18 to 45°C, more preferably -15 to 50°C, and most preferably -5 to 30°C.

[0051] There is no particular limitation on the reaction time in step (II), which can be 0.5 to 20 hours, preferably 1 to 15 hours, more preferably 1 to 10 hours, and most preferably 2 to 5 hours.

[0052] According to the method for preparing polyamic acid solution of the present invention, a polyamic acid solution with high solid content and low kinetic viscosity, which is easy to process in subsequent materials, easy to store, and has high stability can be prepared.

[0053] The solid content of the prepared polyamic acid solution can be 10 wt% or more, preferably 10 wt% or more, more preferably 15 wt% or more, and there is no particular upper limit, for example, 40 wt% or less.

[0054] The intrinsic viscosity of the prepared polyamic acid solution can be 1.50 dL / g or higher, preferably 1.60 dL / g or higher, and more preferably 1.80 dL / g or higher.

[0055] The prepared polyamic acid solution has a kinetic viscosity of less than 15,000 centipoise, preferably less than 10,000 centipoise, and more preferably less than 8,000 centipoise.

[0056] Example

[0057] The present invention is illustrated below by way of examples and comparative examples, but the present invention is not limited to these examples. Of course, various modifications can be made within the scope of the present invention.

[0058] [Determination Method]

[0059] The measurement methods used in the examples are as follows.

[0060] (1) Solid content

[0061] The solid content is calculated using the following formula.

[0062] Solid content (%) = Solid mass (g) / Total mass (g) × 100

[0063] (2) Intrinsic viscosity

[0064] A 0.5% solution was diluted with dimethylformamide and measured using an IV6600 Ubbelohde viscometer from Hangzhou Zhuoxiang Technology Co., Ltd., with the viscosity tube selected to have an inner diameter of 0.58 mm. The solution was poured through filter paper into the viscosity tube at 25°C, and the viscosity was automatically obtained by clicking "Start".

[0065] (3) Kinetic viscosity

[0066] The measurements were performed using an Anton Paar Visco QC 300 kinematic viscometer. The measurement conditions were as follows: running time 30 s, rotation speed 20 rpm, rotor #4, and room temperature.

[0067] (4) Storage stability

[0068] The polyamic acid solution obtained in Example 3 was stored at 10°C, and its intrinsic viscosity was tested and plotted at 10, 25, 50, 150, 300, 600 and 900 hours after storage.

[0069] [Additives]

[0070] The specific additives used in the examples are as follows.

[0071] Pectin: Wokai, Specification: Galacturonic acid (≥74% on a dry basis), 100g packaging, CAS: 9000-69-5; Dimethyl adipate: Shanghai Testing, CP, ≥99%, 100ml packaging, CAS: 627-93-0

[0072] [Example 1]

[0073] 73.09 g of N,N-dimethylformamide and 0.0877 g of additives (0.0731 g of pectin and 0.0146 g of dimethyl adipate) were added to a three-necked flask and stirred at -5°C to dissolve. Then, 2.7122 g (25.08 mmol) of p-phenylenediamine was added and stirred to dissolve. Finally, 5.5250 g (25.33 mmol) of pyromellitic dianhydride was added and stirred at 10°C for 4 hours to obtain a polyamic acid solution with a solid content of 10 wt%, an intrinsic viscosity of 1.78 dL / g, and a kinetic viscosity of 3600 centipoise.

[0074] [Example 2]

[0075] 49.57 g of N-methylpyrrolidone and 1.22 g (20.31 mmol) of ethylenediamine were added to a three-necked flask, followed by 0.2677 g of additives (0.2479 g of pectin and 0.0198 g of dimethyl adipate). After stirring to dissolve, 4.43 g (20.31 mmol) of pyromellitic dianhydride was added. The mixture was stirred at 0 °C for 5 hours to obtain a polyamic acid solution with a solid content of 10 wt%, an intrinsic viscosity of 1.85 dL / g, and a kinetic viscosity of 4752 centipoise.

[0076] [Example 3]

[0077] 7.8998 g (26.85 mmol) of biphenyltetracarboxylic dianhydride and 0.4620 g of additives (0.5227 g of pectin and 0.0627 g of dimethyl adipate) were added to a three-necked flask, followed by the addition of 2.8895 g (26.72 mmol) of p-phenylenediamine. After stirring to dissolve, 52.27 g of N,N-dimethylacetamide was added, and the mixture was stirred at 5 °C for 2 hours to obtain a polyamic acid solution with a solid content of 17 wt%, an intrinsic viscosity of 2.18 dL / g, and a kinetic viscosity of 6503 centipoise.

[0078] Storage stability was evaluated using this polyamic acid solution, and the results are shown below. Figure 1 . Figure 1 The intrinsic viscosity shows a gradual decrease, indicating excellent storage stability.

[0079] [Example 4]

[0080] 62.47 g of dimethyl sulfoxide was added to a three-necked flask containing 0.6529 g of auxiliaries (0.5935 g of pectin and 0.05935 g of dimethyl adipate). Then, 5.9094 g (27.32 mmol) of 4,4'-diaminodiphenyl sulfide was added, and the mixture was stirred until dissolved. After that, 8.5185 g (27.46 mmol) of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride was added, and the mixture was stirred at -15 °C for 3 hours to obtain a polyamic acid solution with a solid content of 19 wt%, an intrinsic viscosity of 2.25 dL / g, and a kinetic viscosity of 6790 centipoise.

[0081] [Example 5]

[0082] 69.41 g of hexamethylphosphoric triamine and 0.3888 g of auxiliaries (0.3471 g of pectin and 0.0417 g of dimethyl adipate) were added to a three-necked flask, followed by the addition of 10.6861 g (36.32 mmol) of biphenyltetracarboxylic dianhydride. After stirring and dissolving, 7.1871 g (36.25 mmol) of 4,4'-diaminodiphenylmethane was added. The mixture was stirred at 25 °C for 8 hours to obtain a polyamic acid solution with a solid content of 20 wt%, an intrinsic viscosity of 2.06 dL / g, and a kinetic viscosity of 5700 centipoise.

[0083] [Example 6]

[0084] 57.36 g of N,N-dimethylacetamide and 0.5885 g of additives (0.5162 g of pectin and 0.0723 g of dimethyl adipate) were added to a three-necked flask, followed by 8.0529 g (37.23 mmol) of 4,4'-diaminodiphenyl sulfide. After stirring to dissolve, 16.5479 g (37.27 mmol) of hexafluorodianhydride was added. The mixture was stirred at 35 °C for 10 hours to obtain a polyamic acid solution with a solid content of 22 wt%, an intrinsic viscosity of 2.37 dL / g, and a kinetic viscosity of 6980 centipoise.

[0085] [Example 7]

[0086] 48.35 g of hexamethylphosphoric triamine and 0.4439 g of auxiliaries (0.411 g of pectin and 0.0329 g of dimethyl adipate) were added to a three-necked flask, followed by 6.9122 g (59.48 mmol) of 1,6-hexanediamine. After stirring and dissolving, 13.013 g (59.66 mmol) of pyromellitic dianhydride was added. The mixture was stirred at 0 °C for 7 hours to obtain a polyamic acid solution with a solid content of 29 wt%, an intrinsic viscosity of 2.41 dL / g, and a kinetic viscosity of 7300 centipoise.

[0087] [Example 8]

[0088] 90.47 g of N-methylpyrrolidone, 0.1086 g of auxiliaries (0.0905 g of pectin and 0.0181 g of dimethyl adipate) and 9.3004 g (50.21 mmol) of 4,4'-diaminodiphenyl ether were added to a three-necked flask. After stirring and dissolving, 25.9514 g (49.86 mmol) of bisphenol A diether dianhydride was added, and the mixture was stirred at 20 °C for 7 hours to obtain a polyamic acid solution with a solid content of 28 wt%, an intrinsic viscosity of 2.04 dL / g, and a kinetic viscosity of 5810 centipoise.

[0089] [Example 9]

[0090] 85.14 g of dimethyl sulfoxide and 0.3893 g of additives (0.3507 g of pectin and 0.0386 g of dimethyl adipate) were added to a three-necked flask, followed by the addition of 7.6077 g (70.35 mmol) of p-phenylenediamine. After stirring and dissolving, 20.6778 g (70.28 mmol) of biphenyltetracarboxylic dianhydride was added. The mixture was stirred at 5 °C for 4 hours to obtain a polyamic acid solution with a solid content of 25 wt%, an intrinsic viscosity of 2.42 dL / g, and a kinetic viscosity of 7210 centipoise.

[0091] [Example 10]

[0092] 58.15 g of N-methylpyrrolidone and 0.2007 g of auxiliaries (0.1745 g of pectin and 0.0262 g of dimethyl adipate) were added to a three-necked flask, followed by the addition of 2.425 g (40.35 mmol) of ethylenediamine. After stirring and dissolving, 10.4607 g (40.51 mmol) of diphenyl sulfide dianhydride was added. The mixture was stirred at 40 °C for 9 hours to obtain a polyamic acid solution with a solid content of 18 wt%, an intrinsic viscosity of 1.64 dL / g, and a kinetic viscosity of 1940 centipoise.

[0093] [Comparative Example 1]

[0094] This comparative example uses the conditions of Example 4, except that no additives are added. The resulting polyamic acid solution has a solid content of 23 wt%, an intrinsic viscosity of 2.07 dL / g, and a kinetic viscosity of 25390 centipoise.

[0095] [Comparative Example 2]

[0096] This comparative example uses the conditions of Example 8, except that no additives are added. The resulting polyamic acid solution has a solid content of 39 wt%, an intrinsic viscosity of 1.64 dL / g, and a kinetic viscosity of 19060 centipoise.

[0097] [Comparative Example 3]

[0098] This comparative example uses the conditions of Example 9, except that no additives are added. The resulting polyamic acid solution has a solid content of 33 wt%, an intrinsic viscosity of 2.19 dL / g, and a kinetic viscosity of 35,700 centipoise.

[0099] [Comparative Example 4]

[0100] This comparative example uses the conditions of Example 9, except that no additives are added but 0.3893g of polydimethylsiloxane is added. The resulting polyamic acid solution has a solid content of 25wt%, an intrinsic viscosity of 1.83dL / g, and a kinetic viscosity of 20400 centipoise.

[0101] The results of Examples 1-10 show that the polyamic acid solution obtained by polymerization using a combination of pectin and dimethyl adipate as an auxiliary agent has both high solids content and low kinetic viscosity, is easy to process in subsequent materials, is easy to store, and has high stability. Comparisons between Example 4 and Comparative Example 1, Example 8 and Comparative Example 2, and Example 9 and Comparative Examples 3 and 4 show that although the solids content decreases when using the combination of pectin and dimethyl adipate, the intrinsic viscosity increases, especially the kinetic viscosity, which decreases significantly, far exceeding the decrease in solids content.

[0102] Industrial applicability

[0103] According to the method for preparing polyamic acid solution of the present invention, a polyamic acid solution with high solid content and low kinetic viscosity, which is easy to process, easy to store and highly stable can be prepared. As a precursor for the production of polyimide, it has industrial applicability in the fields of electronics, electrical engineering, machinery, aerospace, communications, and flexible displays.

Claims

1. A method for preparing a polyamic acid solution, comprising the step of adding a combination of pectin and dimethyl adipate as an auxiliary agent during the reaction of an aromatic dianhydride and a diamine. The total weight of diamine and aromatic dianhydride is 3%–50% relative to a 100% mass reaction system. In the aforementioned adjuvant, the mass ratio of pectin to dimethyl adipate is 1:0.03–0.

4. The reaction uses a solvent, and the amount of pectin added is 0.05 to 2% by mass relative to 100% by mass of the solvent.

2. The method for preparing the polyamic acid solution according to claim 1, wherein, The method includes the following steps: (I) The solvent, auxiliaries, and one of the diamine and aromatic dianhydrides are added to the reaction vessel for dissolution; and (II) Add the diamine and another of the aromatic dianhydrides to the solution obtained in step (I) to react and obtain a polyamic acid solution. The adjuvant is a combination of pectin and dimethyl adipate.

3. The method for preparing the polyamic acid solution as described in claim 2, wherein, In step (I), a diamine is added, and in step (II), an aromatic dianhydride is added.

4. The method for preparing the polyamic acid solution as described in claim 2, wherein, The solvent is an aprotic polar solvent.

5. The method for preparing the polyamic acid solution as described in claim 4, wherein, The aprotic polar solvent is at least one selected from the group consisting of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, and hexamethylphosphoric triamine.

6. The method for preparing the polyamic acid solution as described in claim 1 or 2, wherein, The diamine is selected from at least one group consisting of p-phenylenediamine, 4,4'-diaminodiphenyl ether, hydroquinone diether diamine, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenylmethane, ethylenediamine, 1,6-hexanediamine, and bisphenol A diether diamine.

7. The method for preparing the polyamic acid solution according to claim 1 or 2, wherein, The aromatic dianhydride is at least one selected from the group consisting of pyromellitic dianhydride, biphenyl dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, triphenyl diether dianhydride, diphenyl ether dianhydride, diphenyl sulfide dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, hydroquinone diether dianhydride, hexafluoro dianhydride, resorcinol diether dianhydride, and bisphenol A diether dianhydride.

8. The method for preparing the polyamic acid solution as described in claim 1 or 2, wherein, The molar ratio of the diamine to the aromatic dianhydride is 1:0.98 to 1.

02.

9. A polyamic acid solution obtained by any one of claims 1 to 8.

10. The polyamic acid solution of claim 9, wherein, The kinetic viscosity of the polyamic acid solution is below 15,000 centipoise.

11. The polyamic acid solution of claim 10, wherein, The kinetic viscosity of the polyamic acid solution is below 10,000 centipoise.

12. The polyamic acid solution according to any one of claims 9 to 11, wherein, The solid content of the polyamic acid solution is above 10 wt%.

13. The polyamic acid solution according to any one of claims 9 to 11, wherein, The intrinsic viscosity of this polyamic acid solution is above 1.60 dL / g.

14. A raw material composition for preparing a polyamic acid solution, comprising at least a solvent, an additive, and one of a diamine and an aromatic dianhydride. The adjuvant is a combination of pectin and dimethyl adipate, with a mass ratio of pectin to dimethyl adipate of 1:0.03-0.

4. The amount of pectin added is 0.05 to 2% by mass relative to 100% by mass of the solvent.

15. The raw material composition according to claim 14, used to prepare a polyamic acid solution using the preparation method according to any one of claims 2 to 8.

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