Method for preparing polyimide by reducing imidization temperature of polyamide acid
By mixing ZIF catalysts with polyamic acid solution and performing a stepwise heating process, the problems of high energy consumption and poor dielectric properties of traditional high-temperature imidization were solved, and polyimide materials with excellent performance at low temperatures were prepared, thus broadening their application range.
Patent Information
- Application Number
- CN202511864431.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-11
- Publication Date
- 2026-01-27
AI Technical Summary
Traditional high-temperature imidization processes for polyamic acid suffer from high energy consumption, high cost, high internal stress, and unsatisfactory dielectric properties, making it difficult to meet the requirements of high-frequency and high-speed information transmission.
Zeolite imidazole ester framework materials (ZIFs) were used as catalysts and mixed with polyamic acid solution. Imidification reaction was achieved at low temperature through stepwise heating. The Lewis acid sites of ZIFs were used to lower the reaction energy barrier to prepare polyimide.
Imidization was completed at temperatures below 220°C to prepare polyimide materials with low dielectric constant, low loss, high thermal stability, and high light transmittance, thereby reducing energy consumption and improving material performance.
Smart Images
Figure CN121405940A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of polyimide material preparation technology, specifically a method for preparing polyimide by lowering the imidization temperature of polyamic acid. Background Technology
[0002] As microelectronic devices develop towards higher performance, miniaturization, and multifunctionality, the requirements for microelectronic packaging materials are becoming increasingly stringent. Materials need to possess high thermal stability, excellent dielectric properties, environmental stability, and low synthesis cost to meet the needs of high-speed signal transmission, efficient heat dissipation, and long-term reliability.
[0003] Polyimide (PI) is an aromatic heterocyclic polymer compound containing imide groups in its molecular backbone. The alternating arrangement of rigid aromatic rings and flexible heterocyclic imide bonds in the molecular chain forms a typical example of a high-temperature resistant polymer. PI can withstand long-term temperatures up to 250-300℃, and some varieties can withstand temperatures exceeding 500℃ for short periods. It also possesses high mechanical strength, low dielectric constant, chemical resistance, and radiation resistance, making it a promising high-performance packaging material for the microelectronics field, with excellent application prospects in aerospace, microelectronics, and precision instruments.
[0004] The synthesis mechanism of polyimide involves the condensation reaction of a diamine and a diacid at room temperature to produce polyamic acid. The resulting polyamic acid is then subjected to an imidization reaction at high temperature to convert it into polyimide. However, traditional polyimide preparation via high-temperature imidization of polyamic acid (typically >300℃) suffers from problems such as high energy consumption, high cost, high internal stress, and numerous defects.
[0005] In recent years, significant progress has been made in low-temperature imidization technology. For example, researchers have successfully lowered the imidization temperature to 200-250℃ and achieved imidization degrees exceeding 95%-99% by designing nitrogen-containing diamine monomers (such as PyFNH2) or introducing nitrogen heterocyclic compounds such as quinoline as catalysts. These catalysts can accelerate the imide ring-closing kinetics, reduce the reaction activation energy, and effectively remove residual solvents and small-molecule byproducts at low temperatures. This allows the resulting polyimide films to maintain high thermal stability (T5%>500℃) and mechanical properties while significantly improving light transmittance and flexibility. However, the dielectric and mechanical properties of polyimides obtained by currently developed low-temperature imidization methods are still not ideal and cannot meet the requirements of high-frequency, high-speed information transmission.
[0006] Metal-organic frameworks (MOFs) are a class of crystalline porous materials formed by the self-assembly of metal ions or metal clusters with organic ligands through coordination bonds. Their structure combines the rigidity of inorganic materials with the designability of organic materials, allowing for the selection of different metal centers (such as Zn). 2+ Co2+ Zr 4+ MOFs (Metal-Oxide-Film) can achieve precise control over pore size, surface chemistry, and function through the use of multifunctional organic ligands (such as imidazoles and carboxylic acids). MOFs possess extremely high specific surface areas (up to several thousand m²). 2 MOFs (Multifunctional Materials) exhibit great potential in gas adsorption and separation, catalysis, drug delivery, and energy storage due to their high porosity and density. In recent years, the structural performance regulation of MOFs has become a research hotspot. By designing ligand structures and metal nodes, they can be further endowed with magnetic, chiral, and fluorescent properties, providing new ideas for the development of multifunctional composite materials.
[0007] Zeolite imidazolium ester frameworks (ZIFs) are an important subclass of MOFs, composed of transition metal ions (such as Zn). 2+ Co 2 + ZIFs combine with imidazoles or imidazole derivatives to form a tetrahedral framework structure. ZIFs possess both the high stability of zeolite materials and the high porosity and organic functionality of MOFs, exhibiting a regular pore structure and a large specific surface area (typically 1000-10000 m²). 2 ZIFs (zFs) exhibit excellent thermal and chemical stability. Studies have shown that ZIFs possess good adsorption properties due to their Lewis acid sites and nanoporous structure, which can significantly reduce the energy barrier of chemical reactions, demonstrating great potential in the field of catalysis. Furthermore, due to their uniform pore structure, incorporating ZIFs into polymer matrices can significantly improve the dielectric properties and thermal stability of the polymer matrix. However, there are no reports on their use in lowering the imidization temperature of polyamic acids. Summary of the Invention
[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing polyimide by reducing the imidization temperature of polyamic acid. The resulting polyimide has the characteristics of low dielectric constant, low loss, high thermal stability and high light transmittance.
[0009] The technical solution for achieving the objective of this invention is as follows: A method for preparing polyimide by lowering the imidization temperature of polyamic acid includes the following steps: (1) Aromatic diamine monomer and aromatic dianhydride monomer are polymerized in an organic solvent to obtain a polyamic acid solution; (2) The zeolite imidazole ester framework material (ZIFs) is mixed with the polyamic acid solution to obtain a polyamic acid solution / ZIFs composite. (3) The polyamic acid solution / ZIFs composite is coated on the substrate and the solvent is evaporated to obtain the polyamic acid / ZIFs composite. (4) The obtained polyamic acid / ZIFs composite was subjected to a step heating treatment and imidized at 220-300℃ to obtain a polyimide material.
[0010] Further, the molar ratio of the diamine monomer to the dianhydride monomer in step (1) is 1:(1.02-1.03); The organic solvent is N,N'-dimethylacetamide or a mixed solvent containing N,N'-dimethylacetamide.
[0011] Further, the ZIFs in step (2) are ZIF-67 or ZIF-8, preferably ZIF-67, and the amount of ZIFs added is 1-10% of the mass of polyamic acid.
[0012] Further, the step-by-step heating process in step (4) includes: heating from room temperature to 80°C and holding for 10 min, then heating to 120°C and holding for 10 min, then heating to 150°C and holding for 10 min, then heating to 180°C and holding for 10 min, and finally heating to 220-300°C and holding for 60 min; the polyamic acid imidization reaction can be carried out at 220°C.
[0013] The polyimide film prepared by the method of the present invention has a thermal weight loss of 5% at a temperature not lower than 469°C, a relative permittivity not higher than 2.69, a dielectric loss not higher than 0.00486, and a transmittance of not less than 95% at a wavelength of 546 nm.
[0014] The beneficial effects of this invention are as follows: By using ZIFs as a catalyst, the imidization reaction energy barrier is lowered through Lewis acid sites, reducing the imidization temperature of polyamic acid to 220°C, while simultaneously improving the dielectric, thermal, and optical properties of polyimide. This method is energy-efficient and simple, suitable for the imidization of polyamic acid to prepare polyimide in high-tech fields such as image display devices, optoelectronics, microelectronics, and aerospace. This imidization technology solves many limitations caused by the high-temperature requirement of traditional polyamic acid imidization for polyimide preparation, thus broadening the application range of polyimide. Attached Figure Description
[0015] Figure 1 The image shows the DSC curve of the polyimide film obtained in Example 1.
[0016] Figure 2 This is the differential curve of the DSC curve obtained in Example 1.
[0017] Figure 3 The thermogravimetric analysis curve of the polyimide film obtained in Example 1 is shown.
[0018] Figure 4 The dielectric property curve of the polyimide film obtained in Example 1 is shown.
[0019] Figure 5 The dielectric loss curve of the polyimide film obtained in Example 1 is shown.
[0020] Figure 6 The transmittance spectrum of the polyimide film obtained in Example 1 is shown. Detailed Implementation
[0021] The present application will be further described below with reference to the embodiments and accompanying drawings, but the present application is not limited thereto.
[0022] All materials used in the examples are commercially available. Example
[0023] A method for preparing polyimide by lowering the imidization temperature of polyamic acid includes the following steps: (1) Polymerization reaction: Dissolve 0.4g (2mmol) of 4,4'-diaminodiphenyl ether in 10ml of N,N'-dimethylacetamide, and add 0.6g (2.04mmol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride in 6 portions every 5min while stirring at 70℃, so that the two monomers undergo a condensation reaction to generate polyamic acid. After the reaction is completed, a polyamic acid solution is obtained.
[0024] (2) ZIFs mixing: 0.03g ZIF-67 was dispersed in 5ml N,N'-dimethylacetamide and ultrasonically dispersed in an ultrasonic instrument for 30min to obtain an N,N'-dimethylacetamide / ZIF-67 blend system. The blend system was added to a polyamic acid solution and mixed evenly to obtain a polyamic acid solution / ZIF-67 complex.
[0025] (3) Film formation: The obtained polyamic acid solution / ZIF-67 composite was uniformly coated onto a glass slide using a 1000µm film spreader. The glass slide was then placed in a vacuum drying oven to remove the solvent and moisture, thus forming a polyamic acid / ZIF-67 composite film.
[0026] 4) Imidification: After removing the glass slide coated with polyamic acid / ZIF-67 composite film from the vacuum drying oven, immediately place it into a forced-air drying oven and gradually increase the temperature: room temperature → 80℃ → 120℃ → 150℃ → 180℃ → 220℃, holding each temperature for 10 minutes, and holding at 220℃ for 60 minutes to induce an imidization reaction in the polyamic acid, converting it into polyimide, thus obtaining a polyimide film.
[0027] Reference Figure 1-6 The relevant performance test results of the polyimide film obtained in Example 1 are as follows: The DSC curve obtained from the differential scanning calorimetry (DSC) experiment, such as... Figure 1As shown, there is no exothermic peak, indicating that complete imidization has been achieved; Figure 2 The differential curve of the obtained DSC curve shows that the glass transition temperature of the sample is 241.8℃.
[0028] The initial thermogravimetric temperature (temperature at which 5% of the weight loss occurs) of the obtained sample was 469.1℃. Figure 3 As shown.
[0029] The relative permittivity is 2.69, such as Figure 4 As shown; the dielectric loss is 0.00486, as Figure 5 As shown.
[0030] The transmittance of the obtained sample at wavelengths of 465 nm, 546 nm, and 590 nm were 76.5%, 95.0%, and 96.9%, respectively. Figure 6 As shown in the figure. The results show that adding ZIF-67 to polyamic acid can achieve imidization at 220 degrees Celsius, and the resulting polyimide has good thermal properties, thermal stability, and low dielectric constant and low dielectric loss.
[0031] Example 2 (Changing ZIFs type): The steps are the same as in Example 1, but ZIF-67 is replaced with an equal amount of ZIF-8. The resulting polyimide film has similar properties, with an imidization temperature of 220°C, a dielectric constant of 2.71, and a loss of 0.00492.
[0032] Comparative example (without ZIFs): The steps are the same as in Example 1, but without the addition of ZIFs. Imidination requires a temperature above 300°C, and the resulting film has a dielectric constant >3.0 and a loss of approximately 0.004.
[0033] The above embodiments demonstrate that the method of this application, by adding ZIF to prepare polyimide, does not affect its original superior properties, significantly reduces the imidization temperature, and improves the overall performance of the polyimide. The scope of protection of this application is not limited to the embodiments; any equivalent substitutions based on the concept of this application fall within the scope of this application.
Claims
1. A method for preparing polyimide by lowering the imidization temperature of polyamic acid, characterized in that, Includes the following steps: (1) Aromatic diamine monomer and aromatic dianhydride monomer are polymerized in an organic solvent to obtain a polyamic acid solution; (2) The zeolite imidazole ester backbone material ZIFs is mixed with the polyamic acid solution to obtain a polyamic acid solution / ZIFs composite. (3) The polyamic acid solution / ZIFs composite is coated on the substrate and the solvent is evaporated to obtain the polyamic acid / ZIFs composite. (4) The polyamic acid / ZIFs composite is subjected to a stepwise heating treatment and an imidization reaction is carried out at 220-300℃ to obtain a polyimide material.
2. The method according to claim 1, characterized in that, The molar ratio of the diamine monomer to the dianhydride monomer in step (1) is 1:(1.02-1.03).
3. The method according to claim 1, characterized in that, The organic solvent in step (1) is N,N'-dimethylacetamide or a mixed solvent containing N,N'-dimethylacetamide.
4. The method according to claim 1, characterized in that, The zeolite imidazole ester framework in step (2) is a zeolite imidazole ester metal-organic framework material.
5. The method according to claim 1, characterized in that, The amount of ZIFs added in step (2) is 1-10% of the mass of polyamic acid.
6. The method according to claim 1, characterized in that, The step-by-step heating process in step (4) includes: heating from room temperature to 80°C and holding for 10 minutes, then heating to 120°C and holding for 10 minutes, then heating to 150°C and holding for 10 minutes, then heating to 180°C and holding for 10 minutes, and finally heating to 220-300°C and holding for 60 minutes.
7. The method according to claim 1, characterized in that, The imidization reaction in step (4) is carried out at 220°C.
8. A polyimide film, characterized in that, The polyimide film prepared by the method described in any one of claims 1-7 has a thermal weight loss of 5% at a temperature not lower than 469°C, a relative permittivity not higher than 2.69, a dielectric loss not higher than 0.00486, and a transmittance of not less than 95% at a wavelength of 546 nm.