A method for synthesizing polyimide resin

Abstract

This invention belongs to the field of imide resin synthesis technology, and relates to a method for synthesizing polyimide resin, comprising the following steps: mixing a diamine monomer, a dianhydride monomer, and a solvent, and then placing the mixture in a bladeless mixer of a double asymmetric centrifuge, dispersing at 1000-2500 rpm for 10-40 min; subsequently adding an acid anhydride compound, and dispersing at 1000-2500 rpm for 5-20 min to obtain polyimide resin; the total weight of the dianhydride monomer and the diamine monomer accounts for 25wt%-35wt% of the total reaction system. This invention, without adding other special reagents, utilizes a special synthesis apparatus to effectively avoid adverse effects on the mechanical properties and thermal stability of the polyimide resin while ensuring its processing performance. Furthermore, the synthesis method requires a short reaction time, has high synthesis efficiency, and is highly applicable.

Description

Technical Field

[0001] This invention belongs to the field of imide resin synthesis technology, and relates to a method for synthesizing polyimide resin. Background Technology

[0002] Polyimides are high-performance polymers containing imide rings in their main molecular chain. Due to their excellent thermomechanical properties, radiation resistance, low coefficient of thermal expansion, and electrical insulation, they are widely used in aerospace, microelectronics, rail transportation, and nuclear industries. There are various synthesis processes for polyimides, mainly including melt polycondensation, solution polycondensation, interfacial polycondensation, and vapor deposition. The current mainstream and widely used synthesis route is solution polycondensation: in a non-protic polar solvent, a condensation polymerization reaction is carried out at low temperatures, and after 6-8 hours, the diamine and dianhydride monomers are converted into a polyamic acid solution. However, at high solid content, the strong interactions between polymer molecular chains can easily lead to a sharp increase in solution viscosity, and in extreme cases, it can even promote gelation of the solution, resulting in loss of processability.

[0003] Conventional polyimide resins have high viscosity and poor coating performance, often requiring dilution with solvents to reduce viscosity before use. For example, in existing technology (Huang Chaobo, Zhang He'an, Peng Xinwen, et al. Synthesis and performance characterization of high-strength polyimide [J]. Polymer Materials Science and Engineering, 2007, 23(4).), a polyamic acid solution with ultra-high molecular weight polyimide precursor was first synthesized, requiring dilution with solvents to reduce the solid content to 5% for proper coating. This makes the processing more complex and cumbersome, significantly increases costs, and exacerbates environmental pollution.

[0004] When the solid content is further increased, the viscosity of polyimide resin will increase further, and the processability and operability will deteriorate sharply. In order to overcome this problem, the existing technology CN110229333B locks dialdehyde or polyaldehyde compounds with diamine-terminated polyamic acid backbone (imine) through condensation polymerization to form high molecular weight or cross-linked polyamic acid. After imidization, a new polyimide structure is obtained. Although this method can obtain a new type of low viscosity polyimide resin through a specific structure, enrich the structure of existing polyimides and expand the application field of polyimides, it does not fundamentally solve the problem of high viscosity of existing general-purpose polyimide resins.

[0005] The existing technology CN112029099B uses a staged heating and feeding method to obtain a low-viscosity, high-solids-content polyamic acid solution. The polyimide film made from it has excellent thermal stability, good mechanical properties and low coefficient of thermal expansion. However, the high solids content is only 19%. Since the viscosity of the polyimide solution will also increase with the increase of solids content, if the solids content is increased to 20% or even 30%, the method may no longer be applicable or may not achieve the expected results.

[0006] Existing technology CN101117384B prepared an ammonium ester oligomer. Due to the low molecular weight of the polyamic acid precursor, it exhibits excellent controllability, achieving a smooth coating effect and maintaining low viscosity even at high solid content. Furthermore, during the curing stage, the oligomer can further polymerize into larger molecules, improving the mechanical properties of the final polyimide film. However, unfortunately, even though this oligomer increases the molecular chain length through chain extension during the curing stage, the tensile strength of the final polyimide is only 78.896 MPa, and the elongation at break is only 11.185%. The mechanical properties are still significantly different from those of conventional polyimides, failing to meet the requirements of most polyimide applications.

[0007] In addition, viscosity reduction can also be achieved by adding special additives to polyamic acid resin. For example, the prior art CN103788651B adds trimethylchlorosilane to polyamic acid solution. However, due to the presence of halogens and the corrosiveness of trimethylchlorosilane to certain metals and alloys, which may lead to equipment damage and failure, its application is limited. Furthermore, when the amount of trimethylchlorosilane added is large enough, such as 40% as described in the patent, it can achieve a sufficiently good effect. However, at this point, it has a significant impact on the solid content of the original polyamic acid solution, that is, the solid content is greatly reduced after the addition of trimethylchlorosilane. Existing technology CN114181392A achieves partial chemical imidization by adding a certain amount of acetic anhydride and pyridine. The mechanism by which acetic anhydride and pyridine partially chemically imidize polyamic acid is that they act as dehydrating agents to promote the closure of the imide ring. However, imidization and ring closure lead to dehydration, meaning that a certain amount of water will remain in the system after partial imidization. Polyamic acid is unstable in water and is easily hydrolyzed and its chains broken. Therefore, the addition of acetic anhydride and pyridine will severely affect the storage stability of the polyamic acid solution. Existing technology CN112409612A uses a gemini surfactant made from an ammonium carboxylate salt, but the entire reaction is relatively complex and takes a long time, with a total reaction time approaching 30 hours. Existing technology CN111808285A uses a mixed solution of triethylamine and water, a mixed solution of dimethylethanolamine and water, or a mixed solution of dimethylethanolamine and methanol as an active agent. However, this method requires heating and continuous stirring at high temperature for about 6 hours during the reaction. Existing technology CN104292459B, in addition to adding end-capping agents, also adds a certain proportion of adhesion promoters; however, the resulting polyimide film has poor toughness, with an elongation at break of only 10-15%. While the above methods can obtain low-viscosity polyamic acid resins and improve their subsequent processability, they all have various problems, mainly including complex synthesis or preparation processes with poor controllability, poor product performance or storage stability, affecting the product's solid content, and posing a risk of damaging the substrate. Summary of the Invention

[0008] The purpose of this invention is to provide a method for synthesizing polyimide resins with low viscosity at high solid content.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A method for synthesizing a polyimide resin includes the following steps:

[0011] The diamine monomer, dianhydride monomer, and solvent were mixed and placed in a bladeless mixer of a dual asymmetric centrifuge, and dispersed at 1000-2500 rpm for 10-40 min. Then, the acid anhydride compound was added and dispersed at 1000-2500 rpm for 5-20 min to obtain polyimide resin. The total weight of the dianhydride monomer and the diamine monomer accounted for 25wt%-35wt% of the total reaction system.

[0012] The purpose of this invention is to overcome the problems of high viscosity, poor flowability, and difficult processing of high-solids-content polyimide resins, as well as the long reaction time in polyimide resin synthesis, and to provide a rapid synthesis method for high-solids-content, low-viscosity polyimide resins. Furthermore, the polyimide films prepared from the polyimide resin synthesized by this method exhibit excellent mechanical properties and thermal stability.

[0013] This invention employs a special double asymmetric centrifuge bladeless mixer as the reaction device, simplifying the feeding and reaction steps of polyimide synthesis by adding reactants in two steps. Furthermore, high-speed mixing increases the reaction rate, significantly shortening the polyimide resin condensation reaction time. In addition, the heat generated by high-speed mixing and the exothermic reaction limits the forward reaction of the condensation reaction, effectively restricting the disordered growth of molecular chains. By controlling the monomer ratio and reaction time, and combining end-capping with monofunctional anhydrides, the molecular weight of the polyimide resin can be controlled, resulting in a high-solids, low-viscosity polyimide resin.

[0014] In one preferred embodiment, the bladeless mixer of the dual asymmetric centrifuge is a SpeedMixer high-speed mixer.

[0015] High-speed mixers achieve uniform mixing of reactants through high-speed shearing and impact, which is fundamental to rapid reactions. Compared to traditional stirring methods, high-speed mixers significantly increase the contact area and collision frequency between materials, thereby promoting the reaction.

[0016] In one preferred embodiment, the viscosity of the polyimide resin is 3000-20000 mPa·s.

[0017] In one preferred embodiment, the diamine monomer is one or more of 4,4'-diaminodiphenyl ether, p-phenylenediamine, m-phenylenediamine, benzidine, diaminodiphenylmethane, ethylenediamine, propylenediamine, perfluorodiamine, and spirobisfluorenediamine.

[0018] In one preferred embodiment, the dianhydride monomer is one or more of the following: pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, monoether tetracarboxylic dianhydride, hexafluorodianhydride, benzophenone tetracarboxylic dianhydride, tetramethylbiphenyltetracarboxylic dianhydride, naphthalene tetracarboxylic dianhydride, pyridine dianhydride, cyclobutane tetracarboxylic dianhydride, butanetetracarboxylic dianhydride, diphenyl ether tetracarboxylic dianhydride, fluorinated dianhydride, and silicon-containing dianhydride.

[0019] In one preferred embodiment, the anhydride compound may be one or more of maleic anhydride, norbornene anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, and methyltetrahydrophthalic anhydride.

[0020] In one preferred embodiment, the solvent is a strongly polar aprotic solvent.

[0021] In one preferred embodiment, the solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, acetonitrile, hexamethylphosphoric triamine, acetone, pyridine, and quinoline.

[0022] In one preferred embodiment, the solvent is a mixture of dimethylacetamide and N-methylpyrrolidone.

[0023] In one preferred embodiment, the mass ratio of dimethylacetamide to N-methylpyrrolidone in the mixture is 80-90:8-15.

[0024] In one preferred embodiment, the molar ratio of the diamine monomer to the dianhydride monomer is 1.0:(0.95-0.995).

[0025] In one preferred embodiment, the molar ratio of the anhydride compound to the diamine monomer is 0.01-0.1:1.0.

[0026] The following attempts to further explain the present invention:

[0027] This invention successfully reduces the viscosity of high-solids-content polyimide resins using a specialized synthesis apparatus without adding any special reagents. Furthermore, by controlling the monomer ratio and reaction time, it also yields low-viscosity polyimide resins with a precise viscosity range. While ensuring the processing performance of the polyimide resin, it effectively avoids the adverse effects of existing technologies on the mechanical properties and thermal stability of the final polyimide products. Moreover, this synthesis method requires a short reaction time and has high synthesis efficiency. Especially in addressing the problems of incomplete reaction, long reaction time, and easy agglomeration / gelling caused by poor mass transfer in mechanically stirred high-solids-content polyimide resins, this invention has greater applicability; that is, this method can easily and quickly obtain high-quality polyimide resins.

[0028] The two-step method for adding the main reactants simplifies the feeding process and reduces the operational complexity and errors caused by multiple feedings. The two-step feeding method combined with high-speed mixing ensures that all reactants are uniformly mixed in a short time, improving reaction efficiency. Traditional methods require multiple feedings, each followed by stirring and waiting for the reaction to proceed. This invention, however, uses a two-step method to add reactants, simplifying the feeding process and reducing operational complexity and errors. This simplification not only saves time but also improves the accuracy and consistency of the synthesis.

[0029] The mechanical and thermal energy generated by high-speed mixing promotes the collision and bonding between reactant molecules. Compared with static reactions, high-speed mixing significantly shortens the condensation reaction time and improves production efficiency.

[0030] The exothermic reaction limits the forward reaction of the condensation reaction: the heat generated during the reaction raises the temperature of the reaction system, thus affecting the equilibrium state of the reaction. By controlling the stirring speed and stirring time, the disordered growth of molecular chains can be effectively limited, avoiding excessively high resin viscosity and gelation.

[0031] Monomer ratio and reaction time control combined with monofunctional anhydride end-capping: The monomer ratio determines the molecular structure of the polyimide resin, the reaction time affects the extent of the reaction, and monofunctional anhydride end-capping is used to control the molecular weight. These three factors work together to achieve precise control of the molecular weight of the polyimide resin, ensuring its low viscosity and excellent processability.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] 1. Rapid Synthesis: By employing a dual asymmetric centrifuge with a bladeless mixer and single-feed operation, the synthesis time of polyimide resin is significantly shortened, improving production efficiency. Preliminary experimental data indicate that the synthesis method of this invention can reduce reaction time to 1 / 10 to 1 / 8 of traditional methods; the specific reduction depends on the reaction scale and conditions.

[0034] 2. High Solids Content, Low Viscosity: By controlling the reaction conditions and monomer ratio, low viscosity synthesis of high solids content polyimide resin was achieved, solving the problems of high viscosity and poor flowability of high solids content resins in existing technologies. Experimental data shows that when the solids content reaches 30% to 35%, the resin viscosity can still be maintained at a low level (e.g., within the range of 500-20000 cp), which is far lower than the viscosity of resins with the same solids content synthesized by traditional methods.

[0035] 3. Excellent processing performance: Low-viscosity polyimide resin has better flowability, facilitating processing and molding, and reducing processing difficulty. Experimental data shows that compared with traditional high-viscosity resins, the low-viscosity resin synthesized in this invention can reduce the number of coatings and mold filling time under the same processing conditions. Due to the enhanced resin flowability and uniform viscosity, defects such as bubbles and cracks are less likely to occur during processing. This helps to improve the quality and reliability of the final product.

[0036] 4. Excellent Quality: The polyimide resin film synthesized by this method exhibits excellent mechanical properties and thermal stability. Mechanical property tests show that its tensile strength and elongation at break are comparable to resin films synthesized by traditional methods. Furthermore, thermal stability tests demonstrate that the film maintains stable performance at high temperatures, is not easily decomposed or deformed, and meets the application requirements of high-performance materials.

[0037] 5. Wide applicability: This method is particularly suitable for the synthesis of high solids content polyimide resins, solving the problems of insufficient reaction, long reaction time, and easy agglomeration and gelation caused by poor mass transfer in traditional mechanical stirring.

[0038] 6. Low cost: This invention reduces production costs by improving synthesis efficiency and simplifying operation steps. Furthermore, due to the excellent resin properties and good processing performance, scrap and rework rates can be reduced, further lowering production costs.

[0039] 7. Environmental Protection: This invention utilizes environmentally friendly raw materials and processes during synthesis, reducing the emission and waste of harmful substances. Furthermore, the low-viscosity resin is easier to recycle and reuse during processing, contributing to resource conservation and environmental protection.

[0040] In summary, this invention provides an efficient and simple method for synthesizing high-solids-content, low-viscosity polyimide resin, which has significant technical advantages and broad application prospects. Attached Figure Description

[0041] Figure 1 The FTIR spectra of the polyimide films prepared for the examples and comparative examples are shown. Detailed Implementation

[0042] This invention is not limited to the specific embodiments listed below. Those skilled in the art can implement this invention using various other specific embodiments based on the content disclosed herein. Any modifications or alterations to the design structure and concept of this invention fall within the protection scope of this invention. It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other. The reaction temperature is room temperature.

[0043] Example 1

[0044] (1) Add 20.024 g (0.1 mol) of 4,4′-diaminodiphenyl ether (ODA), 20.721 g (0.095 mol) of pyromellitic dianhydride (PMDA), 88 g of dimethylacetamide (DMAc) and 10 g of N-methylpyrrolidone (NMP) solvent to a container, seal the container and place it in a SpeedMixer high-speed mixer. Set the speed to 1500 rpm and continue the reaction for 30 min. Then add 0.981 g (0.01 mol) of maleic anhydride (MA) and continue high-speed mixing for 10 min to obtain a light yellow homogeneous transparent polyamic acid solution with a solid content of 30 wt% and a viscosity of 3610 mPa·s.

[0045] (2) In a clean room, the prepared polyamic acid solution was degassed and then uniformly coated onto the surface of a clean glass plate using an automatic coating machine. Then it was placed in a high-temperature precision constant temperature chamber for thermal imidization. The heating program was as follows: heating from room temperature to 100°C and holding for 1 hour, heating from 100°C to 200°C and holding for 1 hour, heating from 200°C to 300°C and holding for 1 hour, heating from 300°C to 350°C and holding for 0.5 hours, and then cooling to room temperature to obtain a polyimide film.

[0046] (3) The obtained polyimide was characterized by FT-IR, such as... Figure 1 As shown in the figure; and the mechanical properties of the polyimide film were tested according to standard GB / T 1040.3-2006, and detailed data are listed in Table 1.

[0047] Example 2

[0048] (1) Add 20.024 g (0.1 mol) 4,4′-diaminodiphenyl ether (ODA), 21.049 g (0.0965 mol) pyromellitic dianhydride (PMDA), 88 g DMAc and 10 g NMP solvent to a container, seal the container and place it in a high-speed mixer. Set the speed to 1500 rpm and continue the reaction for 30 min. Then add 0.686 g (0.007 mol) maleic anhydride (MA) and continue high-speed mixing for 10 min to obtain a light yellow homogeneous transparent polyamic acid solution with a solid content of 30 wt% and a viscosity of 5160 mPa·s.

[0049] (2) In a clean room, the prepared polyamic acid solution was degassed and then uniformly coated onto the surface of a clean glass plate using an automatic coating machine. Then it was placed in a high-temperature precision constant temperature chamber for thermal imidization. The heating program was as follows: heating from room temperature to 100°C and holding for 1 hour, heating from 100°C to 200°C and holding for 1 hour, heating from 200°C to 300°C and holding for 1 hour, heating from 300°C to 350°C and holding for 0.5 hours, and then cooling to room temperature to obtain a polyimide film.

[0050] (3) The obtained polyimide was characterized by FT-IR, such as... Figure 1 As shown in the figure; and the mechanical properties of the polyimide film were tested according to standard GB / T 1040.3-2006, and detailed data are listed in Table 1.

[0051] Example 3

[0052] (1) 20.024 g (0.1 mol) of 4,4′-diaminodiphenyl ether (ODA), 21.267 g (0.0975 mol) of pyromellitic dianhydride (PMDA), 88 g of DMAc and 10 g of NMP solvent were added to a container, the container was sealed and placed in a high-speed mixer. The speed was set to 1500 rpm and the reaction was continued for 30 min. Then, 0.490 g (0.005 mol) of maleic anhydride (MA) was added and the mixture was mixed at high speed for another 10 min to obtain a light yellow homogeneous transparent polyamic acid solution with a solid content of 30 wt% and a viscosity of 7610 mPa·s.

[0053] (2) In a clean room, the prepared polyamic acid solution was degassed and then uniformly coated onto the surface of a clean glass plate using an automatic coating machine. Then it was placed in a high-temperature precision constant temperature chamber for thermal imidization. The heating program was as follows: heating from room temperature to 100°C and holding for 1 hour, heating from 100°C to 200°C and holding for 1 hour, heating from 200°C to 300°C and holding for 1 hour, heating from 300°C to 350°C and holding for 0.5 hours, and then cooling to room temperature to obtain a polyimide film.

[0054] (3) The obtained polyimide was characterized by FT-IR, such as... Figure 1 As shown in the figure; and the mechanical properties of the polyimide film were tested according to standard GB / T 1040.3-2006, and detailed data are listed in Table 1.

[0055] Example 4

[0056] (1) Add 20.024 g (0.1 mol) 4,4′-diaminodiphenyl ether (ODA), 21.485 g (0.0985 mol) pyromellitic dianhydride (PMDA), 88 g DMAc and 10 g NMP solvent to a container, seal the container and place it in a high-speed mixer. Set the speed to 1500 rpm and continue the reaction for 30 min. Then add 0.294 g (0.003 mol) maleic anhydride (MA) and continue high-speed mixing at 1500 rpm for 10 min to obtain a light yellow homogeneous transparent polyamic acid solution with a solid content of 30 wt% and a viscosity of 12650 mPa·s.

[0057] (2) In a clean room, the prepared polyamic acid solution was degassed and then uniformly coated onto the surface of a clean glass plate using an automatic coating machine. Then it was placed in a high-temperature precision constant temperature chamber for thermal imidization. The heating program was as follows: heating from room temperature to 100°C and holding for 1 hour, heating from 100°C to 200°C and holding for 1 hour, heating from 200°C to 300°C and holding for 1 hour, heating from 300°C to 350°C and holding for 0.5 hours, and then cooling to room temperature to obtain a polyimide film.

[0058] (3) The obtained polyimide was characterized by FT-IR, such as... Figure 1 As shown in the figure; and the mechanical properties of the polyimide film were tested according to standard GB / T 1040.3-2006, and detailed data are listed in Table 1.

[0059] Example 5

[0060] (1) 20.024 g (0.1 mol) of 4,4′-diaminodiphenyl ether (ODA), 21.703 g (0.0995 mol) of pyromellitic dianhydride (PMDA), 88 g of DMAc and 10 g of NMP solvent were added to a container, the container was sealed and placed in a high-speed mixer, the speed was set to 1500 rpm, and the reaction was continued for 30 min. Then 0.098 g (0.001 mol) of maleic anhydride (MA) was added and the mixture was continued to be mixed at 1500 rpm for 10 min to obtain a light yellow homogeneous transparent polyamic acid solution with a solid content of 30 wt% and a viscosity of 19800 mPa·s.

[0061] (2) In a clean room, the prepared polyamic acid solution was degassed and then uniformly coated onto the surface of a clean glass plate using an automatic coating machine. Then it was placed in a high-temperature precision constant temperature chamber for thermal imidization. The heating program was as follows: heating from room temperature to 100°C and holding for 1 hour, heating from 100°C to 200°C and holding for 1 hour, heating from 200°C to 300°C and holding for 1 hour, heating from 300°C to 350°C and holding for 0.5 hours, and then cooling to room temperature to obtain a polyimide film.

[0062] (3) The obtained polyimide was characterized by FT-IR, such as... Figure 1 As shown in the figure; and the mechanical properties of the polyimide film were tested according to standard GB / T 1040.3-2006, and detailed data are listed in Table 1.

[0063] Comparative Example 1

[0064] (1) 20.024 g (0.1 mol) of 4,4'-diaminodiphenyl ether (ODA), 21.812 g (0.1 mol) of pyromellitic dianhydride (PMDA), 88 g of DMAc and 10 g of NMP solvent were added to a container, the container was sealed and placed in a high-speed mixer, the speed was set to 1500 rpm, and the reaction was continued for 30 min. Then, 0.098 g (0.001 mol) of maleic anhydride (MA) was added and the mixture was continued to be mixed at 1500 rpm for 10 min to obtain a light yellow homogeneous transparent polyamic acid solution with a solid content of 30 wt% and a viscosity of 47200 mPa·s.

[0065] (2) In a clean room, the prepared polyamic acid solution was degassed and then uniformly coated onto the surface of a clean glass plate using an automatic coating machine. Then it was placed in a high-temperature precision constant temperature chamber for thermal imidization. The heating program was as follows: heating from room temperature to 100°C and holding for 1 hour, heating from 100°C to 200°C and holding for 1 hour, heating from 200°C to 300°C and holding for 1 hour, heating from 300°C to 350°C and holding for 0.5 hours, and then cooling to room temperature to obtain a polyimide film.

[0066] (3) The obtained polyimide was characterized by FT-IR, such as... Figure 1 As shown in the figure; and the mechanical properties of the polyimide film were tested according to standard GB / T 1040.3-2006, and detailed data are listed in Table 1.

[0067] Comparative Example 2

[0068] (1) Using the conventional polyamic acid synthesis method, 20.024 g (0.1 mol) of 4,4′-diaminodiphenyl ether (ODA) was added to a three-necked flask, followed by the addition of 88 g of DMAc and stirring with a cantilever stirrer until the ODA was completely dissolved. Then, 20.721 g (0.095 mol) of pyromellitic dianhydride (PMDA) was added in three portions over 1 hour, followed by the addition of 10 g of NMP and stirring for 6 hours. Finally, 0.981 g (0.01 mol) of maleic anhydride (MA) was added and the reaction was continued for 2 hours to obtain a light yellow homogeneous transparent polyamic acid solution with a solid content of 30 wt% and a viscosity of 148,800 mPa·s.

[0069] (2) In a clean room, the prepared polyamic acid solution was degassed and then uniformly coated onto the surface of a clean glass plate using an automatic coating machine. Then it was placed in a high-temperature precision constant temperature chamber for thermal imidization. The heating program was as follows: heating from room temperature to 100°C and holding for 1 hour, heating from 100°C to 200°C and holding for 1 hour, heating from 200°C to 300°C and holding for 1 hour, heating from 300°C to 350°C and holding for 0.5 hours, and then cooling to room temperature to obtain a polyimide film.

[0070] (3) The obtained polyimide was characterized by FT-IR, such as... Figure 1 As shown in the figure; and the mechanical properties of the polyimide film were tested according to standard GB / T 1040.3-2006, and detailed data are listed in Table 1.

[0071] Comparative Example 3

[0072] Using a conventional polyamic acid synthesis method, 20.024 g (0.1 mol) of 4,4′-diaminodiphenyl ether (ODA) was added to a three-necked flask, followed by the addition of 88 g of DMAc and stirring until the ODA was completely dissolved. Then, 21.812 g (0.1 mol) of pyromellitic dianhydride (PMDA) was added in three portions over 1 hour, along with 10 g of NMP and stirring continuously. As the reaction proceeded, the viscosity of the reaction solution increased rapidly and gelled, and the reaction was terminated without obtaining a homogeneous polyamic acid solution.

[0073] The viscosity and mechanical property test results of Examples 1-5 and Comparative Examples 1-3 show that the viscosity of the synthesized polyamic acid increases with increasing dianhydride molar ratio and decreasing maleic anhydride molar ratio, while the tensile strength and elongation at break also gradually improve. This indicates that the viscosity and properties of the synthesized polyamic acid can be effectively controlled by adjusting the monomer ratio. Compared with conventional polyamic acid synthesis methods, although the polyamic acid obtained by the bladeless mixer in a double asymmetric centrifuge has a lower viscosity, its performance is not significantly reduced. Considering both viscosity and mechanical properties, Example 4 is superior.

[0074] Table 1. Viscosity of polyamic acid and mechanical properties of its films under different monomer ratios.

[0075]

[0076] Example 6

[0077] (1) Add 20.024 g (0.1 mol) 4,4′-diaminodiphenyl ether (ODA), 21.485 g (0.0985 mol) pyromellitic dianhydride (PMDA), 88 g DMAc and 10 g NMP solvent to a container, seal the container and place it in a high-speed mixer. Set the speed to 1000 rpm and continue the reaction for 30 min. Then add 0.294 g (0.003 mol) maleic anhydride (MA) and continue high-speed mixing at 1000 rpm for 15 min to obtain a light yellow homogeneous transparent polyamic acid solution with a solid content of 30 wt% and a viscosity of 18800 mPa·s.

[0078] (2) In a clean room, the prepared polyamic acid solution was degassed and then uniformly coated onto the surface of a clean glass plate using an automatic coating machine. Then it was placed in a high-temperature precision constant temperature chamber for thermal imidization. The heating program was as follows: heating from room temperature to 100°C and holding for 1 hour, heating from 100°C to 200°C and holding for 1 hour, heating from 200°C to 300°C and holding for 1 hour, heating from 300°C to 350°C and holding for 0.5 hours, and then cooling to room temperature to obtain a polyimide film.

[0079] (3) The obtained polyimide was characterized by FT-IR, such as... Figure 1 As shown in the figure; and the mechanical properties of the polyimide film were tested according to standard GB / T 1040.3-2006, and detailed data are listed in Table 2.

[0080] Example 7

[0081] (1) Add 20.024 g (0.1 mol) 4,4′-diaminodiphenyl ether (ODA), 21.485 g (0.0985 mol) pyromellitic dianhydride (PMDA), 88 g DMAc and 10 g NMP solvent to a container, seal the container and place it in a high-speed mixer. Set the speed to 2000 rpm and continue the reaction for 30 min. Then add 0.294 g (0.003 mol) maleic anhydride (MA) and continue high-speed mixing at 2000 rpm for 15 min to obtain a light yellow homogeneous transparent polyamic acid solution with a solid content of 30 wt% and a viscosity of 10160 mPa·s.

[0082] (2) In a clean room, the prepared polyamic acid solution was degassed and then uniformly coated onto the surface of a clean glass plate using an automatic coating machine. Then it was placed in a high-temperature precision constant temperature chamber for thermal imidization. The heating program was as follows: heating from room temperature to 100°C and holding for 1 hour, heating from 100°C to 200°C and holding for 1 hour, heating from 200°C to 300°C and holding for 1 hour, heating from 300°C to 350°C and holding for 0.5 hours, and then cooling to room temperature to obtain a polyimide film.

[0083] (3) The obtained polyimide was characterized by FT-IR, such as... Figure 1 As shown in the figure; and the mechanical properties of the polyimide film were tested according to standard GB / T 1040.3-2006, and detailed data are listed in Table 2.

[0084] Example 8

[0085] (1) Add 20.024 g (0.1 mol) 4,4′-diaminodiphenyl ether (ODA), 21.485 g (0.0985 mol) pyromellitic dianhydride (PMDA), 88 g DMAc and 10 g NMP solvent to a container, seal the container and place it in a high-speed mixer. Set the speed to 2500 rpm and continue the reaction for 30 min. Then add 0.294 g (0.003 mol) maleic anhydride (MA) and continue high-speed mixing at 2500 rpm for 15 min to obtain a light yellow homogeneous transparent polyamic acid solution with a solid content of 30 wt% and a viscosity of 7880 mPa·s.

[0086] (2) In a clean room, the prepared polyamic acid solution was degassed and then uniformly coated onto the surface of a clean glass plate using an automatic coating machine. Then it was placed in a high-temperature precision constant temperature chamber for thermal imidization. The heating program was as follows: heating from room temperature to 100°C and holding for 1 hour, heating from 100°C to 200°C and holding for 1 hour, heating from 200°C to 300°C and holding for 1 hour, heating from 300°C to 350°C and holding for 0.5 hours, and then cooling to room temperature to obtain a polyimide film.

[0087] (3) The obtained polyimide was characterized by FT-IR, such as... Figure 1 As shown in the figure; and the mechanical properties of the polyimide film were tested according to standard GB / T 1040.3-2006, and detailed data are listed in Table 2.

[0088] Comparative Example 4

[0089] (1) Using the conventional polyamic acid synthesis method, 20.024 g (0.1 mol) of 4,4′-diaminodiphenyl ether (ODA) was added to a three-necked flask, followed by the addition of 88 g of DMAc and stirring with a cantilever stirrer until the ODA was completely dissolved. Then, 21.485 g (0.0985 mol) of pyromellitic dianhydride (PMDA) was added in three portions over 1 hour. After adding 10 g of NMP, the mixture was stirred continuously at 80 rpm for 6 hours. Finally, 0.294 g (0.003 mol) of maleic anhydride (MA) was added and the reaction was continued for 2 hours to obtain a light yellow homogeneous transparent polyamic acid solution with a solid content of 30 wt% and a viscosity of 672500 mPa·s.

[0090] (2) In a clean room, the prepared polyamic acid solution was degassed and then uniformly coated onto the surface of a clean glass plate using an automatic coating machine. Then it was placed in a high-temperature precision constant temperature chamber for thermal imidization. The heating program was as follows: heating from room temperature to 100°C and holding for 1 hour, heating from 100°C to 200°C and holding for 1 hour, heating from 200°C to 300°C and holding for 1 hour, heating from 300°C to 350°C and holding for 0.5 hours, and then cooling to room temperature to obtain a polyimide film.

[0091] (3) The obtained polyimide was characterized by FT-IR, such as... Figure 1 As shown in the figure; and the mechanical properties of the polyimide film were tested according to standard GB / T 1040.3-2006, and detailed data are listed in Table 2.

[0092] Comparative Example 5

[0093] (1) Add 20.024 g (0.1 mol) 4,4′-diaminodiphenyl ether (ODA), 21.485 g (0.0985 mol) pyromellitic dianhydride (PMDA), 88 g DMAc and 10 g NMP solvent to a container, seal the container and place it in a high-speed mixer. Set the speed to 500 rpm and continue the reaction for 30 min. Then add 0.294 g (0.003 mol) maleic anhydride (MA) and continue high-speed mixing at 500 rpm for 15 min to obtain a light yellow homogeneous transparent polyamic acid solution with a solid content of 30 wt% and a viscosity of 22100 mPa·s.

[0094] (2) In a clean room, the prepared polyamic acid solution was degassed and then uniformly coated onto the surface of a clean glass plate using an automatic coating machine. Then it was placed in a high-temperature precision constant temperature chamber for thermal imidization. The heating program was as follows: heating from room temperature to 100°C and holding for 1 hour, heating from 100°C to 200°C and holding for 1 hour, heating from 200°C to 300°C and holding for 1 hour, heating from 300°C to 350°C and holding for 0.5 hours, and then cooling to room temperature to obtain a polyimide film.

[0095] (3) The obtained polyimide was characterized by FT-IR, such as... Figure 1 As shown in the figure; and the mechanical properties of the polyimide film were tested according to standard GB / T 1040.3-2006, and detailed data are listed in Table 2.

[0096] Table 2 shows the viscosity and mechanical properties of Examples 4, 6-8, and Comparative Examples 4-5. With a fixed monomer ratio, different rotation speeds significantly affected the viscosity of the polyimide; that is, the faster the rotation speed, the lower the viscosity. Furthermore, the mechanical properties initially increased and then decreased with increasing rotation speed. Example 7 exhibited the best overall performance, with mechanical properties close to those of films prepared using conventional polyamic acid synthesis methods. Comparative Example 4, using a traditional polyamic acid synthesis method, achieved extremely high viscosity (over 650,000 K), failing to achieve high solids and low viscosity. The comparative examples, while using a high-speed mixer at a relatively low rotation speed, still resulted in relatively high viscosity and poor mechanical properties.

[0097] Table 2. Viscosity of polyamic acid and mechanical properties of its films at different rotation speeds.

[0098]

[0099] Example 9

[0100] (1) Add 20.024 g (0.1 mol) 4,4′-diaminodiphenyl ether (ODA), 21.485 g (0.0985 mol) pyromellitic dianhydride (PMDA), 88 g DMAc and 10 g NMP solvent to a container, seal the container and place it in a high-speed mixer. Set the speed to 2000 rpm and continue the reaction for 10 min. Then add 0.294 g (0.003 mol) maleic anhydride (MA) and continue high-speed mixing at 2000 rpm for 5 min to obtain a light yellow homogeneous transparent polyamic acid solution with a solid content of 30 wt% and a viscosity of 17660 mPa·s.

[0101] (2) In a clean room, the prepared polyamic acid solution was degassed and then uniformly coated onto the surface of a clean glass plate using an automatic coating machine. Then it was placed in a high-temperature precision constant temperature chamber for thermal imidization. The heating program was as follows: heating from room temperature to 100°C and holding for 1 hour, heating from 100°C to 200°C and holding for 1 hour, heating from 200°C to 300°C and holding for 1 hour, heating from 300°C to 350°C and holding for 0.5 hours, and then cooling to room temperature to obtain a polyimide film.

[0102] (3) The obtained polyimide was characterized by FT-IR, such as... Figure 1 As shown in the figure; and the mechanical properties of the polyimide film were tested according to standard GB / T 1040.3-2006, and detailed data are listed in Table 3.

[0103] Example 10

[0104] (1) Add 20.024 g (0.1 mol) 4,4′-diaminodiphenyl ether (ODA), 21.485 g (0.0985 mol) pyromellitic dianhydride (PMDA), 88 g DMAc and 10 g NMP solvent to a container, seal the container and place it in a high-speed mixer. Set the speed to 2000 rpm and continue the reaction for 20 min. Then add 0.294 g (0.003 mol) maleic anhydride (MA) and continue high-speed mixing at 2000 rpm for 10 min to obtain a light yellow homogeneous transparent polyamic acid solution with a solid content of 30 wt% and a viscosity of 15320 mPa·s.

[0105] (2) In a clean room, the prepared polyamic acid solution was degassed and then uniformly coated onto the surface of a clean glass plate using an automatic coating machine. Then it was placed in a high-temperature precision constant temperature chamber for thermal imidization. The heating program was as follows: heating from room temperature to 100°C and holding for 1 hour, heating from 100°C to 200°C and holding for 1 hour, heating from 200°C to 300°C and holding for 1 hour, heating from 300°C to 350°C and holding for 0.5 hours, and then cooling to room temperature to obtain a polyimide film.

[0106] (3) The obtained polyimide was characterized by FT-IR, such as... Figure 1 As shown in the figure; and the mechanical properties of the polyimide film were tested according to standard GB / T 1040.3-2006, and detailed data are listed in Table 3.

[0107] Example 11

[0108] (1) 20.024 g (0.1 mol) of 4,4′-diaminodiphenyl ether (ODA), 21.485 g (0.0985 mol) of pyromellitic dianhydride (PMDA), 88 g of DMAc and 10 g of NMP solvent were added to a container, the container was sealed and placed in a high-speed mixer. The speed was set to 2000 rpm and the reaction was continued for 40 min. Then 0.294 g (0.003 mol) of maleic anhydride (MA) was added and the mixture was continued to be mixed at 2000 rpm for 20 min to obtain a light yellow homogeneous transparent polyamic acid solution with a solid content of 30 wt% and a viscosity of 6370 mPa·s.

[0109] (2) In a clean room, the prepared polyamic acid solution was degassed and then uniformly coated onto the surface of a clean glass plate using an automatic coating machine. Then it was placed in a high-temperature precision constant temperature chamber for thermal imidization. The heating program was as follows: heating from room temperature to 100°C and holding for 1 hour, heating from 100°C to 200°C and holding for 1 hour, heating from 200°C to 300°C and holding for 1 hour, heating from 300°C to 350°C and holding for 0.5 hours, and then cooling to room temperature to obtain a polyimide film.

[0110] (3) The obtained polyimide was characterized by FT-IR, such as... Figure 1 As shown in the figure; and the mechanical properties of the polyimide film were tested according to standard GB / T 1040.3-2006, and detailed data are listed in Table 3.

[0111] Comparative Example 6

[0112] 20.024 g (0.1 mol) of 4,4′-diaminodiphenyl ether (ODA), 21.485 g (0.0985 mol) of pyromellitic dianhydride (PMDA), 88 g of DMAc, and 10 g of NMP solvent were added to a container. The container was sealed and placed in a high-speed mixer. The speed was set to 2000 rpm and the mixture was reacted for 5 min. Then, 0.294 g (0.003 mol) of maleic anhydride (MA) was added and the mixture was mixed at 2000 rpm for another 2.5 min. The reaction was not complete, and some monomers were still involved. A homogeneous and transparent polyamic acid solution could not be obtained.

[0113] Comparative Example 7

[0114] (1) Add 20.024 g (0.1 mol) 4,4′-diaminodiphenyl ether (ODA), 21.485 g (0.0985 mol) pyromellitic dianhydride (PMDA), 88 g DMAc and 10 g NMP solvent to a container, seal the container and place it in a high-speed mixer. Set the speed to 2000 rpm and continue the reaction for 60 min. Then add 0.294 g (0.003 mol) maleic anhydride (MA) and continue high-speed mixing at 2000 rpm for 30 min to obtain a light yellow homogeneous transparent polyamic acid solution with a solid content of 30 wt% and a viscosity of 2530 mPa·s.

[0115] (2) In a clean room, the prepared polyamic acid solution was degassed and then uniformly coated onto the surface of a clean glass plate using an automatic coating machine. Then it was placed in a high-temperature precision constant temperature chamber for thermal imidization. The heating program was as follows: heating from room temperature to 100°C and holding for 1 hour, heating from 100°C to 200°C and holding for 1 hour, heating from 200°C to 300°C and holding for 1 hour, heating from 300°C to 350°C and holding for 0.5 hours, and then cooling to room temperature to obtain a polyimide film.

[0116] (3) The obtained polyimide was characterized by FT-IR, such as... Figure 1 As shown in the figure; and the mechanical properties of the polyimide film were tested according to standard GB / T 1040.3-2006, and detailed data are listed in Table 3.

[0117] Table 2 shows the viscosity and mechanical properties data of Examples 7, 9-11 and Comparative Examples 6-7. When only the reaction time is changed, the viscosity of polyamic acid gradually decreases with the increase of reaction time, and the mechanical properties show a trend of first increasing and then decreasing. In particular, in Comparative Example 7, although low viscosity polyamic acid can be obtained, its mechanical properties deteriorate sharply and cannot maintain the expected level.

[0118] Table 3. Viscosity of polyamic acid and mechanical properties of its films at different reaction times.

[0119]

[0120]

[0121] Example 12

[0122] (1) 20.024 g (0.1 mol) of 4,4′-diaminodiphenyl ether (ODA), 16.112 g (0.05 mol) of 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 10.470 g (0.048 mol) of pyromellitic dianhydride (PMDA), 98 g of DMAc and 11 g of NMP solvent were added to a container, the container was sealed and placed in a high-speed mixer, the speed was set to 2000 rpm, and the reaction was continued for 30 min. Then, 0.392 g (0.004 mol) of maleic anhydride (MA) was added and the mixture was mixed at 2000 rpm for 15 min to obtain a light yellow homogeneous transparent polyamic acid solution with a solid content of 30 wt% and a viscosity of 12560 mPa·s.

[0123] (2) In a clean room, the prepared polyamic acid solution was degassed and then uniformly coated onto the surface of a clean glass plate using an automatic coating machine. Then it was placed in a high-temperature precision constant temperature chamber for thermal imidization. The heating program was as follows: heating from room temperature to 100°C and holding for 1 hour, heating from 100°C to 200°C and holding for 1 hour, heating from 200°C to 300°C and holding for 1 hour, heating from 300°C to 350°C and holding for 0.5 hours, and then cooling to room temperature to obtain a polyimide film.

[0124] (3) The obtained polyimide was characterized by FT-IR, such as... Figure 1 As shown in the figure; and the mechanical properties of the polyimide film were tested according to standard GB / T 1040.3-2006, and detailed data are listed in Table 4.

[0125] Example 13

[0126] (1) 10.012 g (0.05 mol) of 4,4′-diaminodiphenyl ether (ODA), 11.363 g (0.05 mol) of 4,4-diamino-benzoylaniline (DABA), 21.376 g (0.098 mol) of pyromellitic dianhydride (PMDA), 90 g of DMAc and 10 g of NMP solvent were added to a container, the container was sealed and placed in a high-speed mixer, the speed was set to 2000 rpm, and the reaction was continued for 30 min. Then, 0.392 g (0.004 mol) of maleic anhydride (MA) was added and the mixture was mixed at 2000 rpm for 15 min to obtain a light yellow homogeneous transparent polyamic acid solution with a solid content of 30 wt% and a viscosity of 13130 ​​mPa·s.

[0127] (2) In a clean room, the prepared polyamic acid solution was degassed and then uniformly coated onto the surface of a clean glass plate using an automatic coating machine. Then it was placed in a high-temperature precision constant temperature chamber for thermal imidization. The heating program was as follows: heating from room temperature to 100°C and holding for 1 hour, heating from 100°C to 200°C and holding for 1 hour, heating from 200°C to 300°C and holding for 1 hour, heating from 300°C to 350°C and holding for 0.5 hours, and then cooling to room temperature to obtain a polyimide film.

[0128] (3) The obtained polyimide was characterized by FT-IR, such as... Figure 1 As shown in the figure; and the mechanical properties of the polyimide film were tested according to standard GB / T 1040.3-2006, and detailed data are listed in Table 4.

[0129] Example 14

[0130] (1) 10.012 g (0.05 mol) of 4,4′-diaminodiphenyl ether (ODA), 5.407 g (0.05 mol) of 1,4-phenylenediamine (PDA), 14.711 g (0.05 mol) of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (BPDA), 10.470 g (0.048 mol) of pyromellitic dianhydride (PMDA), 86 g of DMAc and 9 g of NMP solvent were added to a container, the container was sealed and placed in a high-speed mixer, the speed was set to 2000 rpm, and the reaction was continued for 30 min. Then, 0.392 g (0.004 mol) of maleic anhydride (MA) was added and the mixture was mixed at 2000 rpm for 15 min to obtain a light yellow homogeneous transparent polyamic acid solution with a solid content of 30 wt% and a viscosity of 11320 mPa·s.

[0131] (2) In a clean room, the prepared polyamic acid solution was degassed and then uniformly coated onto the surface of a clean glass plate using an automatic coating machine. Then it was placed in a high-temperature precision constant temperature chamber for thermal imidization. The heating program was as follows: heating from room temperature to 100°C and holding for 1 hour, heating from 100°C to 200°C and holding for 1 hour, heating from 200°C to 300°C and holding for 1 hour, heating from 300°C to 350°C and holding for 0.5 hours, and then cooling to room temperature to obtain a polyimide film.

[0132] (3) The obtained polyimide was characterized by FT-IR, such as... Figure 1 As shown in the figure; and the mechanical properties of the polyimide film were tested according to standard GB / T 1040.3-2006, and detailed data are listed in Table 4.

[0133] Table 4 lists the viscosity and mechanical properties of polyamic acid synthesized by copolymerization using other monomers, demonstrating that this synthesis method is also applicable to other structures and has a certain degree of versatility. It can also obtain some polyimide films with outstanding mechanical properties, such as the tensile strength of over 180 MPa and the elongation at break of over 80% in Example 14.

[0134] Table 4. Viscosities of polyamic acid films synthesized from other monomers and their mechanical properties.

[0135]

[0136] Figure 1 This illustrates that although the above examples and comparative examples include the same functional groups, the properties of the resulting polyamic acid and its polyimide films are not entirely the same due to different synthesis methods and processes.

[0137] It should be noted that the above embodiments are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of this invention are still within the scope of protection of this invention.

Claims

1. A method for synthesizing a polyimide resin, characterized in that, Includes the following steps: The diamine monomer, dianhydride monomer, and solvent were mixed and placed in a bladeless mixer of a dual asymmetric centrifuge, and dispersed at 1000-2500 rpm for 10-40 min; then the acid anhydride compound was added, and dispersed at 1000-2500 rpm for 5-20 min to obtain a polyamic acid solution. Then, in a clean room, the prepared polyamic acid solution was degassed and evenly coated onto the surface of a clean glass plate using an automatic coating machine; then it was placed in a high-temperature precision constant temperature oven for thermal imidization. Polyimide resin is obtained; The total weight of the dianhydride monomer and the diamine monomer accounts for 25wt%-35wt% of the total reaction system. The bladeless mixer of the dual asymmetric centrifuge is a SpeedMixer high-speed mixer. The diamine monomer is one or more of 4,4'-diaminodiphenyl ether, p-phenylenediamine, m-phenylenediamine, benzidine, diaminodiphenylmethane, ethylenediamine, propylenediamine, perfluorodiamine, and spirobisfluorenediamine; The dianhydride monomer is one or more of the following: pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, monoether tetracarboxylic dianhydride, benzophenone tetracarboxylic dianhydride, tetramethylbiphenyltetracarboxylic dianhydride, naphthalene tetracarboxylic dianhydride, pyridine dianhydride, cyclobutane tetracarboxylic dianhydride, butane tetracarboxylic dianhydride, fluorinated dianhydride, and silicon-containing dianhydride. The anhydride compound is one or more of maleic anhydride, norbornene anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, and methyltetrahydrophthalic anhydride. The molar ratio of the diamine monomer to the dianhydride monomer is 1.0:(0.95-0.995).

2. The synthesis method according to claim 1, characterized in that, The viscosity of the polyamic acid solution is 3000-20000 mPa·s.

3. The synthesis method according to claim 1, characterized in that, The solvent is a strongly polar aprotic solvent.

4. The synthesis method according to claim 1, characterized in that, The solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, acetonitrile, hexamethylphosphoric triamine, acetone, pyridine, and quinoline.

5. The synthesis method according to any one of claims 1-4, characterized in that, The molar ratio of the acid anhydride compound to the diamine monomer is 0.01-0.1:1.0.

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