A thermoplastic polyimide and its preparation method

Abstract

The present invention provides a thermoplastic polyimide and a preparation method thereof, which relates to the technical field of polymer materials. The method adopts a one-step method to complete the imidization process in a solvent. During this process, the molecular chain is more stretched, which can reduce structural defects such as cross-linking and cyclization. This structural fine-tuning makes the material show a lower T on a macroscopic scale. g and higher T d5% Furthermore, the introduction of ether bonds increases molecular chain flexibility, resulting in a more compliant structure during polymerization and imidization, thereby reducing structural defects caused by cross-linking and cyclization. Furthermore, by replacing some mPDA with a small amount of ODA, the chain rigidity is not increased and the solubility and processability of the original reaction system are not affected. This approach allows the thermal decomposition temperature of the material to be increased without increasing molecular chain rigidity, while maintaining the solubility and processability of the original BPADA and mPDA homopolymer TPI.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, in particular to a thermoplastic polyimide and a preparation method thereof. Background Art

[0002] Thermoplastic polyimide (TPI) is a high-performance specialty engineering plastic whose main chain contains an imide ring (-CO-NR-CO-) structure. It combines the high-temperature resistance, mechanical strength, and chemical stability of traditional thermosetting polyimides, while achieving melt processability through molecular chain design. TPI's comprehensive performance has made it a key material in aerospace, electronics, automotive manufacturing, and medical equipment. For example, in aerospace, TPI is used to manufacture engine fuel line sealing rings, high-temperature bearings, and thermal protective coatings, replacing metal and reducing weight by over 30%. In electronics, its low dielectric constant and resistance to moisture and heat make it an ideal choice for 5G communication substrates and flexible printed circuit board (FPCB) insulation layers. Direct coating with copper foil can solve the dimensional stability issues caused by traditional adhesives. In the automotive industry, TPI is used to manufacture clutch rings and liquid hydrogen pump valve components. Its corrosion and wear resistance can extend component life.

[0003] The glass transition temperature (T g ) typically reaches temperatures exceeding 215°C, can withstand temperatures exceeding 400°C for short periods, and exhibits excellent dimensional stability (shrinkage less than 0.7%) and creep resistance. Its coefficient of friction is as low as 0.1-0.3, comparable to polytetrafluoroethylene (PTFE). Its processability significantly outperforms that of thermosetting polyimides, allowing it to be formed into complex precision components through injection molding, extrusion, and hot pressing, within a processing temperature range of 300-420°C. No secondary vulcanization or crystallization steps are required, significantly improving production efficiency. TPI, derived from the homopolymerization of bisphenol A diether dianhydride (BPADA) and m-phenylenediamine (mPDA), offers excellent solubility and processability, making it one of the most widely used structures. SABIC's high-performance engineering plastic ULTEM™ 1000 employs this structure. However, compared to traditional polyimide (PI), its operating temperature and thermal stability are significantly lower. Therefore, balancing the performance and processability of the resin has always been a key focus in TPI material development.

[0004] In view of this, it is necessary to design an improved thermoplastic polyimide and a preparation method thereof to solve the above problems. Summary of the Invention

[0005] The object of the present invention is to provide a thermoplastic polyimide and a preparation method thereof.

[0006] To achieve the above object of the invention, the present invention provides a method for preparing a thermoplastic polyimide, comprising the following steps:

[0007] Step 1: A three-necked flask is equipped with a water separator and a condenser, and an inert gas is introduced therein, and the inert gas is continuously introduced therein throughout the reaction process; a solvent, m-phenylenediamine and a catalyst are added to the three-necked flask, the temperature is controlled at 0-10°C, and the mixture is fully dissolved under mechanical stirring; after complete dissolution, bisphenol A dianhydride is added while continuing to stir, the temperature is controlled at 0-10°C, and the mixture is stirred for reaction for 4-8 hours; 4,4'-diaminodiphenyl ether is added to the resulting reaction solution, the temperature is controlled at 0-10°C, and the mixture is stirred for reaction for 1-4 hours;

[0008] Step 2: Add toluene to the reaction system, react at a constant temperature of 135° C. for 2-3 hours, and then react at a constant temperature of 180° C. for 6-12 hours to obtain thermoplastic polyimide.

[0009] Preferably, the amount ratio of m-phenylenediamine to 4,4'-diaminodiphenyl ether is 99:1-9:1, and the amount ratio of the total amount of m-phenylenediamine and 4,4'-diaminodiphenyl ether to the amount of bisphenol A dianhydride is 100:101-100:105.

[0010] Preferably, the ratio of the sum of the masses of 4,4'-diaminodiphenyl ether, m-phenylenediamine and bisphenol A dianhydride to the mass of the solvent is 10:90-30:70.

[0011] Preferably, the catalyst is isoquinoline, and its amount is 0.5-3% of the amount of BPADA substance.

[0012] Preferably, the solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and m-cresol.

[0013] Preferably, the inert gas is nitrogen or argon.

[0014] The beneficial effects of the present invention are:

[0015] 1. The preparation method of thermoplastic polyimide provided by the present invention is to prepare polyimide by co-condensation of m-phenylenediamine and bisphenol A dianhydride. The imidization process is completed in a solvent by a one-step method. In this process, the molecular chain is more stretched, which can reduce structural defects such as cross-linking and cyclization. This structural fine-tuning makes the material show a lower T on a macro scale. g and higher T d5%Furthermore, the introduction of ether bonds increases molecular chain flexibility, resulting in a more compliant structure during polymerization and imidization, thereby reducing structural defects caused by cross-linking and cyclization. Furthermore, by replacing some mPDA with a small amount of ODA, not only does the chain rigidity not increase, but the solubility and processability of the original reaction system are also not affected. The combined effect of these two factors allows the reduction of polyimide chain defects and the increase of the thermal decomposition temperature of the material to be achieved without increasing molecular chain rigidity and while maintaining the solubility and processability of the original BPADA and mPDA homopolymer TPI.

[0016] 2. The thermoplastic polyimide provided by the present invention, starting from molecular design, maintains the excellent performance of bisphenol A type diether dianhydride and meta-phenylenediamine homopolymer TPI, and by adjusting the preparation process, reduces the chain defects of the polyimide, giving the material better thermal stability, avoiding problems such as local viscosity unevenness and low thermal decomposition temperature during the material processing, and improving the processing performance of the material. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to specific embodiments.

[0018] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the solutions of the present invention are shown in the text, while other details that are not closely related to the present invention are omitted.

[0019] In addition, it should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0020] The present invention provides a method for preparing thermoplastic polyimide, comprising the following steps:

[0021] Step 1: A three-necked flask is equipped with a water separator and a condenser, and an inert gas is introduced into the flask, and the inert gas is continuously introduced throughout the reaction process; a solvent, m-phenylenediamine (m-PDA), and a catalyst are added to the three-necked flask, the temperature is controlled at 0-10°C, and the catalyst is fully dissolved under mechanical stirring; after complete dissolution, bisphenol A dianhydride (BPADA) is added while continuing to stir, the temperature is controlled at 0-10°C, and the reaction is stirred for 4-8 hours; 4,4'-diaminodiphenyl ether (ODA) is added to the above reaction solution, the temperature is controlled at 0-10°C, and the reaction is stirred for 1-4 hours;

[0022] Step 2: Add toluene to the system and react at 135°C for 2-3 hours, then at 180°C for 6-12 hours;

[0023] Step 3: After the reaction is completed, the system is cooled to room temperature; the resulting solution is poured into anhydrous ethanol, washed, and dried to obtain thermoplastic polyimide.

[0024] In some embodiments, the inert gas is nitrogen or argon.

[0025] In some embodiments, the solvent is one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), N-methylpyrrolidone (NMP), and m-cresol (m-Cresol).

[0026] In some embodiments, the catalyst is isoquinoline, and the amount of isoquinoline is 0.5-3% of the amount of BPADA.

[0027] In some embodiments, the molar ratio of m-PDA to ODA is 99:1-9:1, the molar ratio of the total molar amount of m-PDA and ODA to the molar amount of BPADA is 100:101-100:105; and the ratio of the sum of the masses of ODA, m-PDA, and BPADA to the mass of the solvent is 10:90-30:70.

[0028] The thermoplastic polyimide and its preparation method proposed by the present invention are further described below with reference to specific embodiments:

[0029] Example 1

[0030] In this embodiment, a thermoplastic polyimide is prepared, and the preparation method thereof comprises the following steps:

[0031] Step 1: A 1 L three-necked flask was equipped with a water separator and a condenser, and argon was introduced into the flask, and the introduction was continued throughout the reaction. 260 g of DMF, 0.09 mol of m-PDA, and 0.6% of the molar amount of isoquinoline to the three-necked flask were added, the temperature was controlled at 0°C, and the mixture was fully dissolved under mechanical stirring. After complete dissolution, 0.102 mol of BPADA was added with continued stirring, the temperature was controlled at 0°C, and the reaction was stirred for 4 hours. 0.01 mol of ODA was added to the above reaction solution, the temperature was controlled at 0°C, and the reaction was stirred for 4 hours.

[0032] Step 2: Add toluene to the system and react at 135°C for 2 hours and then at 180°C for 12 hours;

[0033] Step 3: After the reaction is completed, the system is cooled to room temperature; the resulting solution is poured into anhydrous ethanol, washed, and dried to obtain thermoplastic polyimide.

[0034] Example 2

[0035] In this embodiment, a thermoplastic polyimide is prepared, and the preparation method thereof comprises the following steps:

[0036] Step 1: A 1 L three-necked flask was equipped with a water separator and a condenser, and argon was introduced into the flask, which was continuously introduced throughout the reaction. 260 g of DMAC, 0.09 mol of m-PDA, and 0.8% of the molar amount of isoquinoline based on BPADA were added to the flask, the temperature was maintained at 0°C, and the mixture was fully dissolved under mechanical stirring. After complete dissolution, 0.102 mol of BPADA was added with continued stirring, the temperature was maintained at 0°C, and the reaction was stirred for 4 hours. 0.01 mol of ODA was added to the above reaction solution, the temperature was maintained at 0°C, and the reaction was stirred for 4 hours.

[0037] Step 2: Add toluene to the system and react at 135°C for 3 hours and then at 180°C for 12 hours;

[0038] Step 3: After the reaction is completed, the system is cooled to room temperature; the resulting solution is poured into anhydrous ethanol, washed, and dried to obtain thermoplastic polyimide.

[0039] Example 3

[0040] In this embodiment, a thermoplastic polyimide is prepared, and the preparation method thereof comprises the following steps:

[0041] Step 1: A 1 L three-necked flask was equipped with a water separator and a condenser, and argon was introduced into the flask, and the introduction was continued throughout the reaction. 154 g of NMP, 0.095 mol of m-PDA, and 1% of the molar amount of isoquinoline by weight of BPADA were added to the flask, the temperature was controlled at 0°C, and the mixture was fully dissolved under mechanical stirring. After complete dissolution, 0.102 mol of BPADA was added with continued stirring, the temperature was controlled at 0°C, and the reaction was stirred for 4 h. 0.005 mol of ODA was added to the above reaction solution, the temperature was controlled at 0°C, and the reaction was stirred for 4 h.

[0042] Step 2: Add toluene to the system and react at 135°C for 3 hours and then at 180°C for 12 hours;

[0043] Step 3: After the reaction is completed, the system is cooled to room temperature; the resulting solution is poured into anhydrous ethanol, washed, and dried to obtain thermoplastic polyimide.

[0044] Example 4

[0045] In this embodiment, a thermoplastic polyimide is prepared, and the preparation method thereof comprises the following steps:

[0046] Step 1: A 1 L three-necked flask was equipped with a water separator and a condenser, and argon was introduced into the flask, and the introduction was continued throughout the reaction. 571 g of m-Cresol, 0.099 mol of m-PDA, and 2.8% of the molar amount of isoquinoline based on BPADA were added to the three-necked flask, the temperature was controlled at 0°C, and the mixture was fully dissolved under mechanical stirring. After complete dissolution, 0.101 mol of BPADA was added with continued stirring, the temperature was controlled at 0°C, and the reaction was stirred for 4 hours. 0.001 mol of ODA was added to the above reaction solution, the temperature was controlled at 0°C, and the reaction was stirred for 4 hours.

[0047] Step 2: Add toluene to the system and react at 135°C for 3 hours and then at 180°C for 6 hours;

[0048] Step 3: After the reaction is completed, the system is cooled to room temperature; the resulting solution is poured into anhydrous ethanol, washed, and dried to obtain thermoplastic polyimide.

[0049] Comparative Example 1

[0050] In this comparative example, a thermoplastic polyimide was prepared, and the preparation method thereof comprised the following steps:

[0051] Step 1: A 1 L three-necked flask was equipped with a water separator and a condenser, and argon was introduced into the flask, which was continuously introduced throughout the reaction. 256 g of DMF, 0.1 mol of m-PDA, and 0.6% of the molar amount of isoquinoline based on BPADA were added to the flask, the temperature was maintained at 0°C, and the mixture was fully dissolved under mechanical stirring. After complete dissolution, 0.102 mol of BPADA was added with continued stirring, the temperature was maintained at 0°C, and the reaction was stirred for 4 h.

[0052] Step 2: Add toluene to the system and react at 135°C for 3 hours and then at 180°C for 12 hours;

[0053] Step 3: After the reaction is completed, the system is cooled to room temperature; the resulting solution is poured into anhydrous ethanol, washed, and dried to obtain thermoplastic polyimide.

[0054] Comparative Example 2

[0055] This comparative example adopts a two-step method to prepare a thermoplastic polyimide, and its preparation method comprises the following steps:

[0056] Step 1: A 1 L three-necked flask was equipped with a water separator and a condenser, and argon was introduced into the flask, and the introduction was continued throughout the reaction. 260 g of DMF, 0.09 mol of m-PDA, and 0.6% of the molar amount of isoquinoline to the three-necked flask were added, the temperature was controlled at 0°C, and the mixture was fully dissolved under mechanical stirring. After complete dissolution, 0.102 mol of BPADA was added with continued stirring, the temperature was controlled at 0°C, and the reaction was stirred for 4 hours. 0.01 mol of ODA was added to the above reaction solution, the temperature was controlled at 0°C, and the reaction was stirred for 4 hours.

[0057] Step 2: Spread the above polyamic acid solution on the surface of a clean and dry glass plate, place it in a blast oven, and increase the temperature gradually from 80°C to 120°C to 160°C. The heating rate of the gradient heating process is 2°C / min. Keep each temperature section for 30 minutes, bake at a constant temperature of 160°C for 2 hours, then gradually increase the temperature to 280°C and keep it at a constant temperature for 5 hours, and cool naturally to obtain a polyetherimide material.

[0058] Comparative Example 3

[0059] In this comparative example, a thermoplastic polyimide was prepared, and the preparation method thereof comprised the following steps:

[0060] Step 1: A 1 L three-necked flask was equipped with a water separator and a condenser, and argon was introduced into the flask, and the introduction was continued throughout the reaction. 288 g of DMF, 0.01 mol of m-PDA, and 0.6% of the molar amount of isoquinoline to the three-necked flask were added, the temperature was controlled at 0°C, and the mixture was fully dissolved under mechanical stirring. After complete dissolution, 0.102 mol of BPADA was added with continued stirring, the temperature was controlled at 0°C, and the reaction was stirred for 4 hours. 0.09 mol of ODA was added to the above reaction solution, the temperature was controlled at 0°C, and the reaction was stirred for 4 hours.

[0061] Step 2: Add toluene to the system and react at 135°C for 3 hours and then at 180°C for 12 hours;

[0062] Step 3: After the reaction is completed, the system is cooled to room temperature; the resulting solution is poured into anhydrous ethanol, washed, and dried to obtain thermoplastic polyimide.

[0063] The thermoplastic polyimides prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were subjected to DSC and TGA analysis. The process conditions of the material preparation process and the thermal properties of the materials prepared under the corresponding conditions are shown in Table 1. In the table, the amount of isoquinoline is measured based on the amount of BPADA. For example, if the amount of isoquinoline is 0.6% of the amount of BPADA, it is recorded as 0.6%. （BPADA） The solid content in the table is the mass percentage of the non-volatile components in the reaction system. By comparing Examples 1 to 4 with Comparative Example 1, it can be found that the addition of ODA can increase the Td5% temperature, and the increase of its content can effectively increase the T d5% Temperature, and generally speaking, the ether bond structure is not a structure with good thermal stability, so the addition of ODA to improve the thermal stability of the material is unexpected; By comparing Example 1 with Comparative Example 2, it can be clearly found that the one-step preparation of polyimide can effectively reduce the T g , and improve the material's T d5% This is because the one-step method for preparing polyimide can effectively reduce the defects in the internal chain structure of the material. This structural fine-tuning shows a lower T g and higher T d5% .

[0064] Table 1 Process conditions for the preparation of materials in Examples 1 to 4 and Comparative Examples 1 to 3 and thermal properties of the materials obtained under the corresponding conditions

[0065]

[0066] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing thermoplastic polyimide, characterized in that: The steps include: Step 1: A three-necked flask is equipped with a water separator and a condenser, and an inert gas is introduced therein, and the inert gas is continuously introduced therein throughout the reaction process; a solvent, m-phenylenediamine and a catalyst are added to the three-necked flask, the temperature is controlled at 0-10°C, and the mixture is fully dissolved under mechanical stirring; after complete dissolution, stirring is continued and bisphenol A dianhydride is added, the temperature is controlled at 0-10°C, and the reaction is stirred for 4-8 hours; 4,4'-diaminodiphenyl ether is added to the resulting reaction solution, the temperature is controlled at 0-10°C, and the reaction is stirred for 1-4 hours; the molar ratio of m-phenylenediamine to 4,4'-diaminodiphenyl ether is 99:1-9:1, and the molar ratio of the total molar amount of m-phenylenediamine and 4,4'-diaminodiphenyl ether to the molar amount of bisphenol A dianhydride is 100:101-100:105; Step 2: Add toluene to the reaction system, react at a constant temperature of 135° C. for 2-3 hours, and then react at a constant temperature of 180° C. for 6-12 hours to obtain thermoplastic polyimide.

2. The preparation method according to claim 1, characterized in that The ratio of the sum of the masses of 4,4'-diaminodiphenyl ether, m-phenylenediamine and bisphenol A dianhydride to the mass of the solvent is 10:90-30:

70.

3. The preparation method according to claim 1, characterized in that The catalyst is isoquinoline, and its usage is 0.5-3% of the amount of BPADA substance.

4. The preparation method according to claim 1, characterized in that The solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and m-methylphenol.

5. The preparation method according to claim 1, characterized in that The inert gas is nitrogen or argon.

6. A thermoplastic polyimide prepared by the preparation method according to any one of claims 1 to 5.

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