Ternary homopolymerized polyimide as well as preparation method and application thereof

Abstract

The invention discloses ternary homopolymerized polyimide as well as a preparation method and application thereof, and the preparation method of the ternary homopolymerized polyimide comprises the following steps: (1) condensing pyromellitic dianhydride and paranitroaniline to obtain a first intermediate; (2) catalytically hydrogenating the first intermediate to obtain a second intermediate; and (3) preparing the ternary homopolymerized polyimide from the second intermediate and a flexible dianhydride monomer. According to the ternary homopolymerized polyimide disclosed by the invention, the problem of poor performance caused by non-uniform distribution of hard segments and soft segments on ternary copolymerized polyimide chain segments is solved, and uniform distribution of the hard segments (PMDA and arylamine polymerized chain segments) and soft satin (flexible dianhydride monomers and arylamine polymerized chain segments) in polyimide molecular chain segments is realized; the homogeneity of molecular chain segment solubility and reaction activity is guaranteed, perfect combination of rigidity and toughness of the material is achieved, narrow molecular weight distribution of the material is achieved, the comprehensive performance of the material is effectively improved, and the product quality is fundamentally guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyimide, and particularly relates to a ternary homopolymer polyimide, a preparation method thereof and an application thereof. Background Art

[0002] As a special engineering material, polyimide has been widely used in the fields of aviation, aerospace, microelectronics, nanotechnology, liquid crystal, separation membrane, laser, etc. In the 1960s, countries around the world included the research, development and utilization of polyimide in one of the most promising engineering plastics in the 21st century. Polyimide, due to its outstanding characteristics in performance and synthesis, whether as a structural material or as a functional material, its huge application prospects have been fully recognized. It is called a "problem solver", and it is considered that "there would be no today's microelectronics technology without polyimide".

[0003] According to thermogravimetric analysis, the initial decomposition temperature of fully aromatic polyimide is generally around 500°C. The polyimide synthesized from pyromellitic dianhydride and p-phenylenediamine has a thermal decomposition temperature of up to 600°C, which is one of the polymers with the highest thermal stability so far. According to theoretical calculations, the fiber synthesized from pyromellitic dianhydride and p-phenylenediamine can reach 500 GPa, second only to carbon fiber. However, the polyimide material synthesized from pyromellitic dianhydride and p-phenylenediamine has a large molecular chain rigidity, poor solubility, and great processing difficulty, and the material prepared therefrom has insufficient toughness, which limits its wide application.

[0004] Currently, the conventional solution is to introduce flexible structures such as ether bonds and / or aliphatic chains into this rigid polyimide resin to improve the processability and toughness of the polyimide material.

[0005] However, for polyimides synthesized from three or more monomers, the prior art is to add all monomers simultaneously or successively into the same polymerization reaction system, and finally obtain a copolymer polyimide. Taking pyromellitic dianhydride + p-phenylenediamine + flexible dianhydride monomer as an example, the structure of the obtained ternary copolymer polyimide is as follows: .

[0006] Wherein, m and n are the degrees of polymerization, and their ratio is usually m / n = 1 / 99 to 99 / 1, and Ar is the residue of another dianhydride monomer.

[0007] However, in the molecular chain segments of this ternary copolymer polyimide, the hard segments (the m segments in the formula) and the soft segments (the n segments in the formula) are unevenly distributed, resulting in a large loss of the heat resistance and mechanical properties of the material, which poses a great challenge to its application in high-tech fields such as high application strength and high reliability. Summary of the Invention

[0008] The object of the present invention is to solve the above problems and provide a ternary homopolymer polyimide with no loss in heat resistance and mechanical properties, as well as its preparation method and application.

[0009] The technical solution for achieving the object of the present invention is: a ternary homopolymer polyimide, whose structure is as follows: ; wherein, n is the degree of polymerization, and the numerical range is 100 to 2000, and Ar is the residue of the dianhydride monomer.

[0010] The weight-average molecular weight of the ternary homopolymer polyimide is 100,000 to 800,000.

[0011] The preparation method of the above ternary homopolymer polyimide is characterized by the following steps: ① Pyromellitic dianhydride is condensed with p-nitroaniline to obtain a first intermediate, and the structure of the first intermediate is as follows: ; ② The first intermediate is catalytically hydrogenated to obtain a second intermediate, and the structural formula of the second intermediate is as follows: ; ③ The second intermediate and a flexible dianhydride monomer are used to prepare a ternary homopolymer polyimide; its structure is as follows: ; In the above step ①, the condensation is carried out in the presence of an organic solvent, and the organic solvent is one or two of tetrahydrofuran, 1,4-dioxane, methyl tert-butyl ether, 3-methylfuran, DMF, DMAc, m-cresol, and anisole.

[0012] In the above step ②, the catalytic hydrogenation is carried out in the presence of an organic solvent, and the organic solvent is one or two of tetrahydrofuran, 1,4-dioxane, methyl tert-butyl ether, 3-methylfuran, DMF, DMAc, m-cresol, and anisole; preferably the same organic solvent as in the above step ①.

[0013] In the above step ②, the catalyst used for the catalytic hydrogenation is palladium-carbon, platinum-carbon or active nickel.

[0014] In the above step ②, the reaction temperature of the catalytic hydrogenation is 20 to 80 °C, and the reaction pressure is 0.3 to 3 MPa.

[0015] In step ③ above, the flexible dianhydride monomer is one or more of 2,3,3',4'-diphenylether tetracarboxylic dianhydride (a-ODPA), 3,3',4,4'-diphenylether tetracarboxylic dianhydride (s-ODPA), 2,3,3',4'-benzophenone tetracarboxylic dianhydride (a-BTDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (s-BTDA), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), 2,2',3,3'-biphenyltetracarboxylic dianhydride (i-BPDA), 3,3',4,4'-triphenyl bisether tetracarboxylic dianhydride (HQDPA), bisphenol A type diether dianhydride (BPADA), and hexafluorodiacid dianhydride (6FDA).

[0016] The method in step ③ above is a conventional method for preparing polyimide from dianhydride monomer and diamine monomer in the art.

[0017] The above-mentioned terpolymer polyimide is applied in the manufacture of materials such as aviation, aerospace, space technology, precision machinery, petrochemical industry, and automobiles.

[0018] The application is to obtain a structural material by molding or sintering with other materials, or to obtain a high-performance polyimide fiber material by spinning.

[0019] The positive effects of the present invention are as follows: (1) The terpolymer polyimide of the present invention eliminates the problem of poor performance caused by uneven distribution of hard segments and soft segments on the chain segments of the terpolymer polyimide, realizes the uniform distribution of hard segments (the chain segments polymerized from PMDA and aromatic amine) and soft segments (the chain segments polymerized from flexible dianhydride monomer and aromatic amine) in the polyimide molecular chain segments, ensures the uniformity of the solubility and reactivity of the molecular chain segments, realizes the perfect combination of the rigidity and toughness of the material, is conducive to realizing a relatively narrow molecular weight distribution of the material, effectively improves the comprehensive performance of the material, and fundamentally guarantees the quality of the product.

[0020] (2) The terpolymer polyimide of the present invention has high mechanical strength and thermal stability in the temperature range of 270-300 °C, has good processing performance, is suitable for preparing various structural materials by methods such as molding or sintering with other materials, and can also be used for spinning to prepare high-performance polyimide fibers, which are used in fields such as aviation, aerospace, space technology, precision machinery, petrochemical industry, and automobiles. Specific embodiments

[0021] (Example 1) The preparation method of the terpolymer polyimide in this example has the following steps: ① Add 420 mL of tetrahydrofuran and 55.28 g of p-nitroaniline (0.4 mol) to a 1000 mL reaction flask equipped with a mechanical stirrer, a nitrogen protection system, and a temperature control device. Stir at room temperature until the p-nitroaniline is completely dissolved.

[0022] Under nitrogen protection, while maintaining the internal temperature of the reaction system below 25 °C, add 43.62 g of PMDA (0.2 mol) to the reaction system. After addition, stir at room temperature for 6 h to obtain a tetrahydrofuran solution of the first intermediate, which is directly used in the next step.

[0023] ② Add the tetrahydrofuran solution of the first intermediate obtained in step ① to a 1000 mL hydrogenation autoclave, and add 3 g of 5 wt% platinum-carbon catalyst. Seal the reaction autoclave, first displace with nitrogen 3 times, then displace with hydrogen 3 times, and then carry out a holding pressure reaction at a hydrogen pressure of 1.2 - 1.8 MPa and a temperature of 20 - 30 °C until no more hydrogen is absorbed. Continue to hold the pressure for 30 min, release the hydrogen, displace with nitrogen 3 times, open the autoclave lid, filter the reaction solution, and collect and reuse the catalyst.

[0024] Add 100 mL of toluene to the filtrate, distill the mother liquor under reduced pressure to remove the solvent, add 30 mL of toluene to the remaining distillation product, distill to remove water once, and then add 680 mL of DMF to the remaining distillation product to obtain a DMF solution of the second intermediate, which is directly used in the next step.

[0025] ③ Add the DMF solution of the second intermediate obtained in step ② to a 2 L reaction flask under nitrogen protection, maintain the temperature of the reaction system at 20 - 30 °C, add 62.04 g of a-ODPA (0.2 mol) to the reaction system in batches, and rinse the metering and feeding utensils with 10 mL of DMF. Carry out a holding reaction at 20 - 30 °C for 6 h, then add 160 mL of toluene to the reaction system, raise the temperature to reflux for water separation reaction for 8 - 9 h. After the viscosity of the system increases significantly, then carry out a holding and stirring reaction for 1 - 2 h.

[0026] Distill off most of the toluene in the system, lower the temperature of the system to 60 - 70 °C, then add 320 mL of ethanol dropwise to the system, complete the addition in 2 h. After the addition of ethanol, lower the temperature of the system to 10 - 15 °C in about 2 h, stir for 2 h, filter, and wash with ethanol to obtain the crude product.

[0027] Add the crude product to 660 mL of acetone, raise the temperature to 38 - 42 °C and stir for 4 h, then cool to 20 - 25 °C, filter, wash, and dry under vacuum with a programmed temperature rise. The programmed temperature rise process is: 100 °C / 1 h, 160 °C / 2 h, 220 °C / 3 h, 250 °C / 1 h, and finally cool to obtain 128.01 g of ternary homopolymer polyimide resin powder, with a yield of 95.2%.

[0028] (Comparative Example 1) Add 680 mL of DMF and p-phenylenediamine (43.26 g, 0.4 mol) to a 2 L reaction flask equipped with mechanical stirring, a nitrogen protection system, and a temperature control device, and stir at room temperature until the p-phenylenediamine is completely dissolved.

[0029] Under nitrogen protection, while maintaining the internal temperature of the reaction system below 25 °C, add a mixture of 43.62 g of PMDA (0.2 mol) and 62.04 g of a-ODPA (0.2 mol) to the reaction system in batches, and rinse the metering and feeding utensils with 10 mL of DMF. Keep the reaction at 20 - 30 °C for 6 h, then add 160 mL of toluene to the reaction system, heat to reflux for water separation and reaction for 8 - 9 h. After the viscosity of the system increases significantly, keep stirring and reacting for 1 - 2 h.

[0030] Distill off most of the toluene in the system, cool the system temperature to 60 - 70 °C, then add 320 mL of ethanol dropwise to the system, and finish adding it in 2 h. After adding ethanol, cool the system temperature to 10 - 15 °C in about 2 h, stir for 2 h, filter, and wash with ethanol to obtain the crude product.

[0031] Add the crude product to 660 ml of acetone, heat to 38 - 42 °C and stir for 4 h, then cool to 20 - 25 °C, filter, wash, and dry under vacuum with a programmed temperature rise. The programmed temperature rise process is: 100 °C / 1 h, 160 °C / 2 h, 220 °C / 3 h, 250 °C / 1 h. Finally, cool to obtain 125.24 g of the ternary copolymer polyimide resin powder, and the yield is 93.1%.

[0032] (Examples 2 - 5) The preparation methods of the ternary homopolymer polyimide in each example are basically the same as those in Example 1, and the differences are shown in Table 1.

[0033] Table 1 Example 1 Example 2 Example 3 Example 4 Example 5 The solvents in steps ① and ② Tetrahydrofuran Dioxane Tetrahydrofuran Tetrahydrofuran Tetrahydrofuran The catalyst in step ② 5% platinum on carbon 5% palladium on carbon 5% palladium on carbon 5% palladium on carbon 5% palladium on carbon The water-carrying solvent in step ② Toluene Cyclohexane Toluene Toluene Toluene The solvent in step ③ DMF DMAc DMF DMF DMAc The dianhydride monomer in step ③ 0.2 mol of a-ODPA 0.2 mol of a-BPDA 0.2 mol of a-BTDA 0.2 mol of HQDPA 0.2 mol of BPADA The slurrying solvent in step ③ Acetone Ethanol Acetone Ethanol Acetone

[0034] (Test Example) Test the relevant properties of the polyimide resin powder prepared in each example and comparative example, and the results are shown in Table 2, where: The D50 particle size and D90 particle size are detected by laser particle size analysis.

[0035] The intrinsic viscosity is tested according to the national standard "GB / T 1632.3 - 2010 Plastics - Determination of viscosity of dilute solutions of polymers using capillary viscometers - Part 3: Polyethylene and polypropylene", using NMP as the solvent and selecting an Ubbelohde viscometer with a diameter of Φ0.84 mm.

[0036] The bulk density is tested according to the national standard "GB / T 1636 - 2008 Plastics - Determination of apparent density of materials that can flow out of a specified funnel".

[0037] Table 2 Example 1 Comparative Example 1 Example 2 Example 3 Example 4 Example 5 D50 / μm 22.74 33.26 25.79 26.54 23.53 24.23 D90 / μm 41.63 68.67 49.16 45.28 42.67 47.52 Intrinsic viscosity (dl / g) 1.51 1.47 1.45 1.49 1.52 1.46 Bulk density (g / ml) 0.38 0.33 0.39 0.40 0.41 0.36 Glass transition temperature (℃) 349 326 361 352 345 341 Tensile strength (MPa) 155 119 156 149 163 151 <![CDATA[Izod impact strength (kJ / m 2 )]]> 221 176 217 231 226 219

[0038] (Application Example) Polyimide molded articles were prepared from the polyimide resin powders obtained in each of the examples and comparative examples, respectively, by the following specific method: The polyimide resin powder was added to a QLB / D-500T flat vulcanizing machine, pressurized at 2 MPa and held at 295 °C for 60 minutes, then pressurized at 100 MPa and heated to 380 °C and held for 2 hours), and then demolded to obtain the product.

[0039] The relevant properties of each polyimide molded article were tested, and the results are still shown in Table 2, where: Test method for glass transition temperature: Using a Q800 type dynamic thermomechanical analysis (DMA) instrument from TA Instruments, USA, the temperature range was 100 - 600 °C, the heating rate was 5 °C / min, and the nitrogen atmosphere was used.

[0040] Tensile strength was tested in accordance with the national standard "GB / T 1040.1-2006 Plastics - Determination of tensile properties - Part 1: General principles".

[0041] The unnotched impact strength was tested in accordance with the national standard "GB / T 1043.1-2008 Plastics - Determination of Charpy impact properties - Part 1: Non-instrumented impact test".

[0042] It can be seen from Table 2 that the ternary homopolymer polyimide (Example 1) prepared by the method of the present invention has the advantages of smaller particle size, higher heat resistance and mechanical properties compared with the ternary copolymer polyimide (Comparative Example 1) prepared by the existing method.

Claims

1. A ternary homopolymer polyimide having the following structure: ； in, n is the degree of polymerization, and its numerical value ranges from 100 to 2000, and Ar is the residue of the dianhydride monomer.

2. The method for preparing the ternary homopolymer polyimide according to claim 1, characterized in that The following steps are involved: ① The first intermediate is obtained by condensing pyromellitic anhydride with p-nitroaniline. The structure of the first intermediate is as follows: ； ② The first intermediate is catalytically hydrogenated to obtain a second intermediate, the structural formula of the second intermediate is as follows: ； ③ The second intermediate and the flexible dianhydride monomer are used to prepare a ternary homopolymer polyimide; Its structure is as follows: 。 3. The method for preparing a ternary homopolymer polyimide according to claim 2, characterized in that: In the above step ①, the condensation is carried out in the presence of an organic solvent, and the organic solvent is one or two of tetrahydrofuran, 1,4-dioxane, methyl tert-butyl ether, 3-methylfuran, DMF, DMAc, m-cresol, and anisole.

4. The method for preparing a ternary homopolymer polyimide according to claim 2, characterized in that: In the above step ②, the catalytic hydrogenation is carried out in the presence of an organic solvent, and the organic solvent is one or two of tetrahydrofuran, 1,4-dioxane, methyl tert-butyl ether, 3-methylfuran, DMF, DMAc, m-cresol, and anisole.

5. The method for preparing a ternary homopolymer polyimide according to claim 2, characterized in that: In the above step ②, the catalyst used for the catalytic hydrogenation is palladium carbon, platinum carbon or activated nickel.

6. The method for preparing a ternary homopolymer polyimide according to claim 2, characterized in that: In the above step ②, the reaction temperature of the catalytic hydrogenation is 20-80° C., and the reaction pressure is 0.3-3 MPa.

7. The method for preparing a ternary homopolymer polyimide according to claim 2, characterized in that: In the above step ③, the flexible dianhydride monomer is one or more of 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, 2,3,3',4'-dibenzophenone tetracarboxylic dianhydride, 3,3',4,4'-dibenzophenone tetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-triphenyl bis(ether) tetracarboxylic dianhydride, bisphenol A type diether dianhydride, and hexafluoro dianhydride.

8. Application of the ternary homopolymer polyimide according to claim 1 in aviation, aerospace, space technology, precision machinery, petrochemical industry and automobile material manufacturing.

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