Thermoplastic polyimide and preparation method thereof

Abstract

The invention provides thermoplastic polyimide and a preparation method thereof, and relates to the technical field of high polymer materials. According to the method, an imidization process is completed in a solvent by adopting a one-step method, a molecular chain is more stretched in the process, the structural defects of crosslinking, cyclization and the like can be reduced, and the material shows lower Tg and higher Td5% macroscopically due to fine adjustment of the structure; besides, the flexibility of a molecular chain is increased by introducing an ether bond structure, so that the molecular chain has a smoother structure in the polymerization and imidization processes, the structural defects caused by cross-linking cyclization and the like are reduced, meanwhile, a small amount of ODA is used for replacing part of mPDA, the chain rigidity cannot be improved, and the molecular chain is more flexible. And the dissolvability and processability of the original reaction system are not influenced. Through the mode, the thermal decomposition temperature of the material can be improved on the premise of not increasing the rigidity of a molecular chain and keeping the original solubility and processability of the BPADA and mPDA homopolymerized TPI.

Description

Technical Field

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

[0002] Thermoplastic polyimide (TPI) is a high-performance special engineering plastic. Its main chain contains an imide ring (-CO-NR-CO-) structure, combining the high temperature resistance, mechanical strength, and chemical stability of traditional thermosetting polyimide. At the same time, through molecular chain design, it realizes the melt processing characteristics. TPI has become a key material in aerospace, electronics, automotive manufacturing, and medical equipment due to its comprehensive performance. For example, in the aerospace field, TPI is used to manufacture engine fuel pipeline sealing rings, high-temperature bearings, and thermal protection coatings, which can replace metals and reduce weight by more than 30%; in the electronics field, its low dielectric constant and moisture and heat resistance characteristics make it an ideal choice for 5G communication substrates and flexible printed circuit board (FPCB) insulating layers. Directly covering copper foil can solve the dimensional stability problem caused by traditional adhesives; in the automotive industry, TPI is used to manufacture clutch gear rings and liquid hydrogen pump valve components, and its corrosion resistance and wear resistance can extend the service life of components.

[0003] The glass transition temperature (T g ) of TPI can usually reach above 215°C, can withstand high temperatures above 400°C in the short term, and has excellent dimensional stability (shrinkage rate below 0.7%) and creep resistance. The friction coefficient is as low as 0.1 - 0.3, comparable to that of polytetrafluoroethylene (PTFE). Its processing performance is significantly better than that of thermosetting polyimide. It can form complex and precise components through injection molding, extrusion, hot molding, etc. The processing temperature range is 300 - 420°C, and there is no need for secondary vulcanization or crystallization steps, greatly improving production efficiency. Among them, the TPI obtained by copolymerization of bisphenol A type diether dianhydride (BPADA) and m-phenylenediamine (mPDA) has good solubility and processing performance, and is one of the most widely used structures. The high-performance engineering plastic ULTEM™ 1000 produced by SABIC is the above structure. However, compared with traditional PI, its use temperature and thermal stability have both decreased significantly. In summary, balancing the use performance and processing performance of the resin has always been a focus in the research and development of TPI materials.

[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 purpose of the present invention is to provide a thermoplastic polyimide and a preparation method thereof.

[0006] To achieve the above-mentioned invention purpose, the present invention provides a preparation method of a thermoplastic polyimide, including 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 into it and continuously introduced 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 it is fully dissolved under mechanical stirring; after complete dissolution, continue stirring and add bisphenol A dianhydride, control the temperature at 0-10 °C, and stir and react for 4-8 h; add 4,4'-diaminodiphenyl ether to the obtained reaction solution, control the temperature at 0-10 °C, and stir and react for 1-4 h;

[0008] Step 2: Toluene is added to the reaction system, and after reacting at a constant temperature of 135 °C for 2-3 h, it is reacted at a constant temperature of 180 °C for 6-12 h to obtain a thermoplastic polyimide.

[0009] Preferably, the molar ratio of m-phenylenediamine to 4,4'-diaminodiphenyl ether is 99:1-9:1, and the total molar ratio of m-phenylenediamine and 4,4'-diaminodiphenyl ether to 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 dosage is 0.5-3% of the molar amount of BPADA.

[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 as follows:

[0015] 1. The preparation method of the thermoplastic polyimide provided by the present invention realizes the preparation of polyimide through the co-polycondensation of m-phenylenediamine and bisphenol A dianhydride. The imidization process is completed in one step in a solvent. In this process, the molecular chains are more stretched, which can reduce structural defects such as cross-linking and cyclization. This fine adjustment of the structure makes the material macroscopically exhibit a lower T g and a higher T d5%; In addition, the introduction of the ether bond structure increases the flexibility of the molecular chain, enabling the molecular chain to have a more compliant structure during the processes of polymerization and imidization, thereby reducing structural defects caused by crosslinking cyclization, etc. Meanwhile, by replacing a part of mPDA with a small amount of ODA, not only will it not cause an increase in chain rigidity, but it will also not affect the solubility and processability of the original reaction system. Under the combined action of the above two factors, it is possible to reduce the chain defects of the polyimide and increase the thermal decomposition temperature of the material without increasing the molecular chain rigidity and while maintaining the solubility and processing performance of the homopolymer TPI of the original BPADA and mPDA.

[0016] 2. The thermoplastic polyimide provided by the present invention, starting from molecular design, while maintaining the excellent properties of the homopolymer TPI of bisphenol A type diether dianhydride and m-phenylenediamine, reduces the chain defects of the polyimide by adjusting the preparation process, endows the material with better thermal stability, avoids problems such as uneven local viscosity and low thermal decomposition temperature during the processing of the material, and improves the processing performance of the material. Specific Embodiments

[0017] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in detail below with reference to specific embodiments.

[0018] Here, it should also be noted that in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the solution of the present invention are shown in the text, while other details less related to the present invention are omitted.

[0019] In addition, it should also be noted that the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

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

[0021] Step 1: Install a water separator and a condenser on a three-necked flask, introduce an inert gas into it, and continuously introduce it throughout the reaction process; add a solvent, m-phenylenediamine (m-PDA), and a catalyst into the three-necked flask, control the temperature at 0 - 10°C, and stir mechanically to dissolve it fully; after complete dissolution, continue stirring and add bisphenol A type dianhydride (BPADA), control the temperature at 0 - 10°C, and stir and react for 4 - 8 h; add 4,4'-diaminodiphenyl ether (ODA) to the above reaction solution, control the temperature at 0 - 10°C, and stir and react for 1 - 4 h;

[0022] Step 2: Add toluene into the system, react at a constant temperature of 135 °C for 2 - 3 h, and react at a constant temperature of 180 °C for 6 - 12 h;

[0023] Step 3: After the reaction is completed, wait for the system to cool to room temperature; pour the reaction solution into absolute ethanol, wash and dry 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.

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

[0027] In some embodiments, the molar ratio of m-PDA to ODA is 99:1 - 9:1, and the total molar ratio of m-PDA and ODA to the molar ratio of BPADA is 100:101 - 100:105; 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 following further illustrates the thermoplastic polyimide and its preparation method proposed by the present invention in combination with specific embodiments:

[0029] Example 1

[0030] This example prepared a thermoplastic polyimide, and its preparation method included the following steps:

[0031] Step 1: Install a water separator and a condenser on a 1 L three-necked flask, introduce argon into it, and continuously introduce it throughout the reaction process; add 260 g of DMF, 0.09 mol of m-PDA, and isoquinoline with an amount of 0.6% of the molar amount of BPADA into the three-necked flask, control the temperature at 0 °C, and fully dissolve it under mechanical stirring; after complete dissolution, continue stirring and add 0.102 mol of BPADA, control the temperature at 0 °C, and stir and react for 4 h; add 0.01 mol of ODA to the above reaction solution, control the temperature at 0 °C, and stir and react for 4 h;

[0032] Step 2: Add toluene into the system, react at a constant temperature of 135 °C for 2 h, and react at a constant temperature of 180 °C for 12 h;

[0033] Step 3: After the reaction is completed, wait for the system to cool to room temperature; pour the reaction solution into absolute ethanol, wash and dry to obtain thermoplastic polyimide.

[0034] Example 2

[0035] In this example, a thermoplastic polyimide was prepared, and its preparation method included the following steps:

[0036] Step 1: Install a water separator and a condenser on a 1 L three-necked flask, introduce argon into it, and continuously introduce it throughout the reaction process; add 260 g of DMAC, 0.09 mol of m-PDA, and isoquinoline in an amount of 0.8% of the molar amount of BPADA into the three-necked flask, control the temperature at 0 °C, and stir mechanically to dissolve it completely; after complete dissolution, continue stirring and add 0.102 mol of BPADA, control the temperature at 0 °C, and stir and react for 4 h; add 0.01 mol of ODA to the above reaction solution, control the temperature at 0 °C, and stir and react for 4 h;

[0037] Step 2: Add toluene to the system, react at a constant temperature of 135 °C for 3 h, and react at a constant temperature of 180 °C for 12 h;

[0038] Step 3: After the reaction is completed, wait for the system to cool to room temperature; pour the reaction solution into absolute ethanol, wash and dry to obtain the thermoplastic polyimide.

[0039] Example 3

[0040] In this example, a thermoplastic polyimide was prepared, and its preparation method included the following steps:

[0041] Step 1: Install a water separator and a condenser on a 1 L three-necked flask, introduce argon into it, and continuously introduce it throughout the reaction process; add 154 g of NMP, 0.095 mol of m-PDA, and isoquinoline in an amount of 1% of the molar amount of BPADA into the three-necked flask, control the temperature at 0 °C, and stir mechanically to dissolve it completely; after complete dissolution, continue stirring and add 0.102 mol of BPADA, control the temperature at 0 °C, and stir and react for 4 h; add 0.005 mol of ODA to the above reaction solution, control the temperature at 0 °C, and stir and react for 4 h;

[0042] Step 2: Add toluene to the system, react at a constant temperature of 135 °C for 3 h, and react at a constant temperature of 180 °C for 12 h;

[0043] Step 3: After the reaction is completed, wait for the system to cool to room temperature; pour the reaction solution into absolute ethanol, wash and dry to obtain the thermoplastic polyimide.

[0044] Example 4

[0045] In this example, a thermoplastic polyimide was prepared, and its preparation method included the following steps:

[0046] Step 1: Install a water separator and a condenser on a 1 L three-necked flask, introduce argon into it, and continuously introduce it throughout the reaction process; add 571 g of m-Cresol, 0.099 mol of m-PDA, and isoquinoline with a dosage of 2.8% of the molar amount of BPADA into the three-necked flask, control the temperature at 0 °C, and stir mechanically to dissolve it fully; after complete dissolution, continue stirring and add 0.101 mol of BPADA, control the temperature at 0 °C, and stir and react for 4 h; add 0.001 mol of ODA to the above reaction solution, control the temperature at 0 °C, and stir and react for 4 h;

[0047] Step 2: Add toluene to the system, react at a constant temperature of 135 °C for 3 h, and react at a constant temperature of 180 °C for 6 h;

[0048] Step 3: After the reaction is completed, wait for the system to cool to room temperature; pour the reaction solution into absolute ethanol, wash and dry to obtain thermoplastic polyimide.

[0049] Comparative Example 1

[0050] A thermoplastic polyimide was prepared in this comparative example, and its preparation method included the following steps:

[0051] Step 1: Install a water separator and a condenser on a 1 L three-necked flask, introduce argon into it, and continuously introduce it throughout the reaction process; add 256 g of DMF, 0.1 mol of m-PDA, and isoquinoline with a dosage of 0.6% of the molar amount of BPADA into the three-necked flask, control the temperature at 0 °C, and stir mechanically to dissolve it fully; after complete dissolution, continue stirring and add 0.102 mol of BPADA, control the temperature at 0 °C, and stir and react for 4 h;

[0052] Step 2: Add toluene to the system, react at a constant temperature of 135 °C for 3 h, and react at a constant temperature of 180 °C for 12 h;

[0053] Step 3: After the reaction is completed, wait for the system to cool to room temperature; pour the reaction solution into absolute ethanol, wash and dry to obtain thermoplastic polyimide.

[0054] Comparative Example 2

[0055] A thermoplastic polyimide was prepared by a two-step method in this comparative example, and its preparation method included the following steps:

[0056] Step 1: Install a water separator and a condenser on a 1-L three-necked flask, introduce argon into it, and continuously introduce argon throughout the reaction process; add 260 g of DMF, 0.09 mol of m-PDA, and isoquinoline with a dosage of 0.6% of the molar amount of BPADA into the three-necked flask, control the temperature at 0 °C, and stir mechanically to dissolve it fully; after complete dissolution, continue stirring and add 0.102 mol of BPADA, control the temperature at 0 °C, and stir and react for 4 h; add 0.01 mol of ODA to the above reaction solution, control the temperature at 0 °C, and stir and react for 4 h;

[0057] Step 2: Spread the above polyamic acid solution evenly on the surface of a clean and dry glass plate, place it in a forced-air oven, and increase the temperature in a gradient of 80 °C → 120 °C → 160 °C. The heating rate during the gradient heating process is 2 °C / min, keep the temperature for 30 min at each temperature segment, bake at 160 °C for 2 h, then increase the temperature in a gradient to 280 °C and keep the temperature for 5 h, and cool naturally to obtain a polyetherimide material.

[0058] Comparative Example 3

[0059] This comparative example prepared a thermoplastic polyimide, and its preparation method included the following steps:

[0060] Step 1: Install a water separator and a condenser on a 1-L three-necked flask, introduce argon into it, and continuously introduce argon throughout the reaction process; add 288 g of DMF, 0.01 mol of m-PDA, and isoquinoline with a dosage of 0.6% of the molar amount of BPADA into the three-necked flask, control the temperature at 0 °C, and stir mechanically to dissolve it fully; after complete dissolution, continue stirring and add 0.102 mol of BPADA, control the temperature at 0 °C, and stir and react for 4 h; add 0.09 mol of ODA to the above reaction solution, control the temperature at 0 °C, and stir and react for 4 h;

[0061] Step 2: Add toluene to the system, react at a constant temperature of 135 °C for 3 h, and react at a constant temperature of 180 °C for 12 h;

[0062] Step 3: After the reaction is completed, wait for the system to cool to room temperature; pour the reaction solution obtained into absolute ethanol, wash and dry to obtain a thermoplastic polyimide.

[0063] Perform DSC and TGA analyses on the thermoplastic polyimides prepared in Examples 1 to 4 and Comparative Examples 1 to 3. The process conditions during the material preparation process and the thermal performance data of the materials prepared under the corresponding conditions are shown in Table 1. In the table, the amount of substance of isoquinoline is measured based on the amount of substance of BPADA. For example, if the amount of substance of isoquinoline is 0.6% of the amount of substance of BPADA, it is recorded as 0.6%n （BPADA） , and the solid content in the table is the mass ratio of the non-volatile components in the reaction system. By comparing Examples 1 to 4 and Comparative Example 1, it can be found that the addition of ODA can increase the T of the materiald5% temperature, and an increase in its content can effectively increase the T of the material d5% temperature. Generally speaking, the ether bond structure is not a structure with good thermal stability. Therefore, the improvement of the thermal stability of the material by adding ODA is unexpected. By comparing Example 1 and Comparative Example 2, it can be clearly found that the one-step preparation of polyimide can effectively reduce the T of the material g , and increase the T of the material d5% , because the process of preparing polyimide by the one-step method can effectively reduce the defects in the internal chain structure of the material. This fine-tuning of the structure macroscopically shows a lower T of the material g and a 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 performance data of the materials obtained under the corresponding conditions

[0065]

[0066] The above examples are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a thermoplastic polyimide, characterized in that, It includes the following steps: Step 1: A three-necked flask is equipped with a water separator and a condenser, and an inert gas is introduced into it and continuously introduced 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 it is fully dissolved under mechanical stirring; after complete dissolution, continue stirring and add bisphenol A dianhydride, control the temperature at 0-10 °C, and stir and react for 4-8 h; add 4,4'-diaminodiphenyl ether to the obtained reaction solution, control the temperature at 0-10 °C, and stir and react for 1-4 h; Step 2: Toluene is added to the reaction system, and after reacting at a constant temperature of 135 °C for 2-3 h, it is reacted at a constant temperature of 180 °C for 6-12 h to obtain a thermoplastic polyimide.

2. The preparation method according to claim 1, characterized in that, The molar ratio of m-phenylenediamine to 4,4'-diaminodiphenyl ether is 99:1-9:1, and the molar 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.

3. 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.

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

5. 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-cresol.

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

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

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