Polyamic acid solution, preparation method thereof and raw material composition for preparing polyamic acid solution

Abstract

The invention relates to a polyamic acid solution, a preparation method thereof and a raw material composition for preparing the polyamic acid solution. The polyamide acid solution which has high solid content and low dynamic viscosity, is convenient for subsequent material processing, is easy to store and has high stability can be prepared by using a specific auxiliary agent through a simple means. The invention relates to a preparation method of a polyamide acid solution, which comprises the step of adding a combination of pectin and dimethyl adipate as an auxiliary agent in the reaction process of aromatic dianhydride and diamine.

Description

Technical Field

[0001] The invention belongs to the field of polyamic acid synthesis, and relates to a polyamic acid solution and a preparation method thereof, and a raw material composition for preparing the polyamic acid solution. Background Art

[0002] Polyimide is a heterocyclic polymer (R-CO-NH-CO-R') containing an imide group in its molecular structure. It has excellent mechanical properties, high and low temperature resistance, dimensional stability, etc. The products are usually mainly films, fibers, resins, foams, and composite materials. Now it has been widely used in the fields of electronics, machinery, aerospace, communications, and flexible displays. Polyimide is usually prepared by a "two-step method". Aromatic dianhydrides and diamines are polymerized in a non-protonic polar solvent to obtain a polyamic acid solution, which is then heat treated or chemically imidized to obtain polyimide. Therefore, the characteristics of the polyamic acid precursor determine the quality of the final product.

[0003] When coatings, films and other products are prepared by spraying, casting, spinning and other methods, the solid content and dynamic viscosity of the polyamic acid slurry are important factors affecting processability. A large number of hydrogen bonds are easily formed in and between the polyamic acid molecular chains, and the ionization of the carboxylic acid group enhances the polyelectrolyte effect, so that the slurry with high solid content usually has a very large dynamic viscosity, and even gelation occurs, which is not conducive to subsequent processing applications. Reducing the solid content can reduce the slurry dynamic viscosity to a certain extent, but this method will increase the amount of solvent used, affect product quality and lead to reduced production efficiency. In view of the problem of poor slurry fluidity under high solid content conditions, CN101558102A discloses a method for regulating the water content of the reaction system; CN106589371A proposes a method for controlling the viscosity of polyamic acid by adding tetracarboxylic acid to the dianhydride and diamine reaction system, but this method needs to be operated under N2 atmosphere, which will increase the complexity of the reaction; CN104292459A discloses a method for adjusting by adding polysiloxane adhesion promoters, but there are problems such as the need to add feed multiple times, replenish solvent, and wait for a long time to add feed.

[0004] In addition, polyamic acid will spontaneously degrade during storage, causing its intrinsic viscosity to decrease. The essential reason for this degradation process is that the carboxylic acid hydroxyl group in the polyamic acid and the amide carbonyl group in the molecule undergo a depolymerization reaction through nucleophilic addition, and the moisture present in the system causes the anhydride end group formed by the depolymerization of the molecular chain to hydrolyze to form two carboxylic acid groups. This irreversible reaction causes the properties of the polyamic acid to change, resulting in a short shelf life of the slurry and poor batch stability. At present, the methods for extending 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 group (including adding organic bases, carboxyl esterification), molecular chain end-capping, etc. However, these methods have problems such as cumbersome processes, high reagent toxicity, and high process costs. Therefore, it is a problem to be solved urgently to synthesize a polyamic acid slurry with high solid content and low dynamic viscosity, convenient for subsequent material processing, easy to store and high stability through simple preparation methods.

[0005] CN103788651A discloses a method for preparing a polyamic acid solution with low apparent viscosity, wherein 5% to 40% of trimethylchlorosilane by mass of the polyamic acid is added to the polyamic acid solution, and the solution is stirred at room temperature for 1 to 5 hours to obtain a polyamic acid solution with an apparent viscosity of 0.2 to 15,000 centipoise. However, in this method, the content of trimethylchlorosilane as an auxiliary agent accounts for a large proportion, which may affect subsequent material processing and require the removal of the auxiliary agent.

[0006] CN106589368A discloses a method for preparing a polyamic acid composition with controllable viscosity, wherein tetracarboxylic acid is added by controlling the ratio of the added amount, and tetracarboxylic dianhydride is added in batches to control the viscosity. However, the method needs to be operated under a N2 atmosphere, which increases the difficulty of experimental operation, and the method does not optimize the stability of the polyamic acid during storage.

[0007] CN115678010A discloses a method for obtaining polyamic acid by polycondensation of a dianhydride containing a flexible chain structure and a diamine containing a nitrogen-containing heteroaromatic ring, wherein the diamine containing a nitrogen-containing heteroaromatic ring is added to a solvent, and then the dianhydride containing a flexible chain structure is added three times. This method not only requires the use of specific dianhydride and diamine, but also requires batch addition, which increases the number of operating steps, and the method does not explore the viscosity and storage stability of the polyamic acid solution. Summary of the invention

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

[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 dynamic viscosity by simple means, which is convenient for subsequent material processing, easy to store and highly stable.

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

[0011] Specifically, the present invention provides a method for preparing a polyamic acid solution, which comprises 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 comprises the following steps:

[0013] (I) adding a solvent, an auxiliary agent, and one of a diamine and an aromatic dianhydride into a reaction container to dissolve them; and

[0014] (II) adding the other of the diamine and the aromatic dianhydride to the solution obtained in step (I) to react and obtain a polyamic acid solution,

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

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

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

[0018] In the above technical solution, preferably, the solvent is a non-protonic 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 triamide.

[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 scheme, preferably, the aromatic dianhydride is at least one selected from the group consisting of pyromellitic dianhydride, biphenyl tetracarboxylic dianhydride, 3,3',4,4'-diphenyl ketone 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 1:0.98-1.02.

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

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

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

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

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

[0028] In addition, the present invention also provides a raw material composition for preparing a polyamic acid solution, which comprises 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] Effects of the Invention

[0031] According to the method for preparing a polyamic acid solution of the present invention, a polyamic acid solution having high solid content and low dynamic viscosity, which is convenient for subsequent material processing, easy to store and highly stable can be prepared. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a graph showing changes in intrinsic viscosity when the polyamic acid solution obtained in Example 3 is stored at 10°C. DETAILED DESCRIPTION

[0033] The invention discloses a method for preparing a polyamic acid solution, which comprises the step of adding a combination of pectin and dimethyl adipate as an auxiliary agent during the reaction of aromatic dianhydride and diamine.

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

[0035] (I) adding a solvent, an auxiliary agent, and one of a diamine and an aromatic dianhydride into a reaction container to dissolve them; and

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

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

[0038] The preparation method of the invention can prepare a polyamic acid solution with controllable viscosity and high stability by utilizing specific auxiliary agents.

[0039] In the present invention, an aprotic polar solvent is preferably used as the solvent. As the aprotic polar solvent, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide and hexamethylphosphoric triamide are preferably used.

[0040] In the present invention, as the diamine, it is preferred to use an aromatic or aliphatic diamine, among which 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 are preferred, and p-phenylenediamine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenylmethane, ethylenediamine and 1,6-hexanediamine are more preferred.

[0041] In the present invention, as the aromatic dianhydride, preferably used are pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic 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, and more preferably pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, diphenyl sulfide dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, hexafluoro dianhydride and bisphenol A diether dianhydride.

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

[0043] The total amount of the diamine and the aromatic dianhydride used may be 3% to 50%, preferably 5% to 40%, and more preferably 10% to 30%, based on 100% by mass of the reaction system.

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

[0045] Pectin is mainly a type of acidic heteropolysaccharide composed of D-galacturonic acid connected by α-1,4-glycosidic bonds. It is usually used as a food additive in food, health products and some cosmetics, and has a structure shown in the following formula (1). The inventors found that by adding pectin, the dynamic viscosity of the polyamic acid solution can be reduced. This is because the polymer acids in pectin can increase free hydrogen ions, weaken the hydrogen bonding between polyamic acid molecules and within the molecules, and shield the polyelectrolyte effect of polyamic acid, thereby significantly reducing the dynamic viscosity of the system. In addition, by combining dimethyl adipate with pectin, the stability of the polyamic acid solution can be improved. This is because dimethyl adipate can be hydrolyzed in the presence of pectin, while increasing the solubility of pectin, it produces a carboxylic acid group of the product of the depolymerization reaction of polyamic acid, thereby reducing the reaction rate of the reverse reaction and extending the 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 auxiliary agent added, the amount of pectin added is 0.01 to 5% by mass, preferably 0.03 to 3% by mass, more preferably 0.05 to 2% by mass, and most preferably 0.1 to 1% by mass, relative to 100% by mass of the aprotic polar solvent used in the reaction system. 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 to 0.5, preferably 1:0.03 to 0.4, more preferably 1:0.05 to 0.3, and most preferably 1:0.07 to 0.2.

[0048] In the preparation method of the present invention, in step (I), a non-protonic polar solvent, an auxiliary agent, and one of a diamine and an aromatic dianhydride are added to a reaction vessel to dissolve, and in step (II), the other of the diamine and the aromatic dianhydride is added to the solution obtained in step (I) to react to obtain a polyamic acid solution. There is no particular limitation on the order of adding the diamine and the aromatic dianhydride. Those skilled in the art are familiar with the positive charging method of first adding the diamine and then the aromatic dianhydride, the reverse charging method of first adding the aromatic dianhydride and then the diamine, and the simultaneous charging method. Preferably, the positive charging method is adopted, that is, the diamine is added in step (I) and the aromatic dianhydride is added in step (II).

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

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

[0051] The reaction time in step (II) is not particularly limited and may 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 a polyamic acid solution of the present invention, a polyamic acid solution having high solid content and low dynamic viscosity, which is convenient for subsequent material processing, easy to store and highly stable can be prepared.

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

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

[0055] The dynamic viscosity of the prepared polyamic acid solution is 15000 centipoise or less, preferably 10000 centipoise or less, and more preferably 8000 centipoise or less.

[0056] Example

[0057] The present invention will be specifically described below by way of examples and comparative examples, but the present invention is not limited to these examples and can of course be implemented with various modifications within the scope of the gist of the present invention.

[0058] [Measurement method]

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

[0060] (1) Solid content

[0061] The solid content was calculated by the following formula.

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

[0063] (2) Intrinsic viscosity

[0064] Use dimethylformamide to dilute to 0.5% solution, use Hangzhou Zhuoxiang Technology Co., Ltd. IV6600 Ubbelohde viscometer for measurement, select viscosity tube with inner diameter of 0.58mm. Pour the solution through filter paper to the scale line of viscosity tube at 25℃, click start, and the viscosity can be automatically obtained.

[0065] (3) Dynamic viscosity

[0066] The measurement was 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 No. 4, and temperature was 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 measured at 10, 25, 50, 150, 300, 600 and 900 hours after storage, and a curve was plotted.

[0069] [Additives]

[0070] The auxiliary agents specifically used in the examples are as follows.

[0071] Pectin: Wokai, specification: galacturonic acid (dry basis ≥74%), 100g packaging, CAS: 9000-69-5 Dimethyl adipate: Shanghai test, CP, ≥99%, 100ml packaging, CAS: 627-93-0

[0072] [Example 1]

[0073] 73.09 g of N,N-dimethylformamide and 0.0877 g of auxiliary agents (0.0731 g of pectin and 0.0146 g of dimethyl adipate) were added to a three-necked flask, and 2.7122 g (25.08 mmol) of p-phenylenediamine was added after stirring and dissolving at -5°C. 5.5250 g (25.33 mmol) of pyromellitic dianhydride was added after stirring and dissolving, and the reaction was 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 dynamic 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, and then 0.2677 g of auxiliary agents (0.2479 g of pectin and 0.0198 g of dimethyl adipate) were added. After stirring and dissolving, 4.43 g (20.31 mmol) of pyromellitic dianhydride was added, and the reaction 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 dynamic viscosity of 4752 centipoise.

[0076] [Example 3]

[0077] 7.8998 g (26.85 mmol) of biphenyltetracarboxylic dianhydride and 0.4620 g of auxiliary agents (0.5227 g of pectin and 0.0627 g of dimethyl adipate) were added to a three-necked flask, and then 2.8895 g (26.72 mmol) of p-phenylenediamine was added. After stirring to dissolve, 52.27 g of N, N-dimethylacetamide was added, and the reaction 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 dynamic viscosity of 6503 centipoise.

[0078] The storage stability of the polyamic acid solution was evaluated. The results are shown in Figure 1 . Figure 1 It can be seen that the intrinsic viscosity decreases slowly, indicating excellent storage stability.

[0079] [Example 4]

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

[0081] [Example 5]

[0082] 69.41 g of hexamethylphosphoric triamide and 0.3888 g of auxiliary agents (0.3471 g of pectin and 0.0417 g of dimethyl adipate) were added to a three-necked flask, and then 10.6861 g (36.32 mmol) of biphenyltetracarboxylic dianhydride was added. After stirring and dissolving, 7.1871 g (36.25 mmol) of 4,4'-diaminodiphenylmethane was added. The reaction 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 dynamic viscosity of 5700 centipoise.

[0083] [Example 6]

[0084] 57.36 g of N, N-dimethylacetamide and 0.5885 g of auxiliary agents (0.5162 g of pectin and 0.0723 g of dimethyl adipate) were added to a three-necked flask, and then 8.0529 g (37.23 mmol) of 4,4'-diaminodiphenyl sulfide was added. After stirring and dissolving, 16.5479 g (37.27 mmol) of hexafluorodianhydride was added, and the reaction 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 dynamic viscosity of 6980 centipoise.

[0085] [Example 7]

[0086] 48.35 g of hexamethylphosphoric triamide and 0.4439 g of auxiliary agents (0.411 g of pectin and 0.0329 g of dimethyl adipate) were added to a three-necked flask, and then 6.9122 g (59.48 mmol) of 1,6-hexanediamine was added. After stirring to dissolve, 13.013 g (59.66 mmol) of isophthalic anhydride was added. The reaction 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 dynamic viscosity of 7300 centipoise.

[0087] [Example 8]

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

[0089] [Example 9]

[0090] 85.14 g of dimethyl sulfoxide and 0.3893 g of auxiliary agents (0.3507 g of pectin and 0.0386 g of dimethyl adipate) were added to a three-necked flask, and then 7.6077 g (70.35 mmol) of p-phenylenediamine was added. After stirring to dissolve, 20.6778 g (70.28 mmol) of biphenyltetracarboxylic dianhydride was added, and the reaction 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 dynamic viscosity of 7210 centipoise.

[0091] [Example 10]

[0092] 58.15 g of N-methylpyrrolidone and 0.2007 g of auxiliary agents (0.1745 g of pectin and 0.0262 g of dimethyl adipate) were added to a three-necked flask, and then 2.425 g (40.35 mmol) of ethylenediamine was added. After stirring to dissolve, 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 dynamic viscosity of 1940 centipoise.

[0093] [Comparative Example 1]

[0094] This comparative example adopts the conditions of Example 4, except that no auxiliary agent is added in this comparative example. The obtained polyamic acid solution has a solid content of 23 wt%, an intrinsic viscosity of 2.07 dL / g, and a dynamic viscosity of 25390 centipoise.

[0095] [Comparative Example 2]

[0096] This comparative example adopts the conditions of Example 8, except that no auxiliary agent is added in this comparative example. The obtained polyamic acid solution has a solid content of 39 wt%, an intrinsic viscosity of 1.64 dL / g, and a dynamic viscosity of 19060 centipoise.

[0097] [Comparative Example 3]

[0098] This comparative example adopts the conditions of Example 9, except that no auxiliary agent is added in this comparative example. The obtained polyamic acid solution has a solid content of 33 wt%, an intrinsic viscosity of 2.19 dL / g, and a dynamic viscosity of 35700 centipoise.

[0099] [Comparative Example 4]

[0100] This comparative example adopts the conditions of Example 9, except that no auxiliary agent is added in this comparative example but 0.3893 g of polydimethylsiloxane is added. The obtained polyamic acid solution has a solid content of 25 wt%, an intrinsic viscosity of 1.83 dL / g, and a dynamic viscosity of 20400 centipoise.

[0101] The results of Examples 1 to 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 solid content and low dynamic viscosity, is convenient for subsequent material processing, is easy to store and has high stability. By comparing Example 4 with Comparative Example 1, Example 8 with Comparative Example 2, Example 9 with Comparative Example 3 and Comparative Example 4, it can be seen that when using a combination of pectin and dimethyl adipate, although the solid content is reduced, the intrinsic viscosity increases, especially the reduction in dynamic viscosity is huge, far exceeding the reduction in solid content.

[0102] Industrial Applicability

[0103] According to the preparation method of the polyamic acid solution of the present invention, a polyamic acid solution with high solid content and low dynamic viscosity, convenient for subsequent material processing, easy to preserve and high stability can be prepared. As a precursor for producing polyimide, it has industrial applicability in the fields of electronics, machinery, aerospace, communications, flexible displays, etc.

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.

2. The method for preparing a polyamic acid solution according to claim 1, wherein: The method comprises the following steps: (I) adding a solvent, an auxiliary agent, and one of a diamine and an aromatic dianhydride into a reaction container to dissolve them; and (II) adding the other of the diamine and the aromatic dianhydride to the solution obtained in step (I) to react and obtain a polyamic acid solution, The auxiliary agent is a combination of pectin and dimethyl adipate.

3. The method for preparing a polyamic acid solution according to claim 1, wherein: In the auxiliary agent, the mass ratio of pectin to dimethyl adipate is 1:0.03-0.

4.

4. The method for preparing a polyamic acid solution according to claim 1 or 2, wherein: In the step (I), a diamine is added, and in the step (II), an aromatic dianhydride is added.

5. The method for preparing a polyamic acid solution according to claim 2, wherein: The solvent is an aprotic polar solvent.

6. The method for preparing a polyamic acid solution according to claim 5, 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 triamide.

7. The method for preparing a polyamic acid solution according to claim 1 or 2, wherein: 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.

8. The method for preparing a 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, biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenyl ketone 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.

9. The method for preparing a polyamic acid solution according to claim 1 or 2, wherein: The molar ratio of the diamine to the aromatic dianhydride is 1:0.98-1.

02.

10. The method for preparing a polyamic acid solution according to claim 2, wherein: The added amount of the pectin is 0.05 to 2% by mass relative to 100% by mass of the solvent. 11 . A polyamic acid solution obtained by the preparation method according to claim 1 .

12. The polyamic acid solution according to claim 11, wherein The dynamic viscosity of the polyamic acid solution is 15000 centipoise or less.

13. The polyamic acid solution according to claim 12, wherein The dynamic viscosity of the polyamic acid solution is 10,000 centipoise or less.

14. The polyamic acid solution according to any one of claims 11 to 13, wherein The solid content of the polyamic acid solution is above 10 wt %.

15. The polyamic acid solution according to any one of claims 11 to 13, wherein The intrinsic viscosity of the polyamic acid solution is 1.60 dL / g or more.

16. 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. 17 . The raw material composition according to claim 16 , which is used for preparing a polyamic acid solution by the preparation method according to claim 1 .

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