Method for simply and conveniently preparing photosensitive polyimide raw material

Abstract

The invention belongs to the technical field of preparation of organic compounds, and particularly relates to a method for simply and conveniently preparing a photosensitive polyimide raw material, which comprises the following steps: by taking 2, 3, 5, 6-tetrafluoro-1, 4-phenylenediamine and m-nitrobenzoyl chloride as raw materials, respectively carrying out mixed reaction on the raw materials in the presence of a solvent, adding an eluate after the reaction, filtering to obtain an intermediate, and carrying out catalytic hydrogenation to obtain a final product. The obtained product is high in yield, high in purity, mild in reaction condition, high in catalytic efficiency, environment-friendly, simple and convenient to operate, less in three wastes and wide in application range, and can be repeatedly recycled and reused by using a single reaction solvent.

Description

Technical Field

[0001] This invention relates to a simple method for preparing photosensitive polyimide raw materials, belonging to the field of organic synthesis technology. Background Technology

[0002] Polyimide (PI), as a specialty engineering plastic, possesses excellent heat resistance, mechanical properties, electrical properties, and film-forming properties. Its applications span aerospace, automotive, and electronics industries. In the microelectronics industry, PI is widely used as a photolithography agent. Photosensitive polyimide (PSPI) is a polymer material with both photosensitivity and heat resistance. It can greatly simplify the complex photolithography process used with non-photosensitive polyimides, while simultaneously meeting the special requirements of insulating layers, surface passivation layers, ion implantation masks, and electron beam lithography in multilayer interconnect systems of large-scale and very large-scale integrated circuits. Therefore, it is attracting increasing attention.

[0003] Traditionally, photosensitive polyimides are prepared by adding photosensitizers at the polyamic acid stage or by directly synthesizing diamine or dianhydride monomers with photosensitive groups. Therefore, diamine or dianhydride monomers with photosensitive groups are one of the key raw materials (monomers) for photosensitive polyimide resins. However, the synthesis of dianhydrides and diamines is complex, and the photosensitive groups require special chemical treatment, which greatly increases the difficulty and cost. The current situation is that there are relatively few raw materials for preparing photosensitive polyimides, and the cost is high, which limits the promotion and utilization of photosensitive polyimides and has become the core pain point for the commercial application of photosensitive polyimides (PSPI). Summary of the Invention

[0004] In view of the shortcomings of existing technologies, especially the limited availability and high cost of raw materials for photosensitive polyimide, which restricts the widespread use of photosensitive polyimide, this invention provides a simple method for preparing photosensitive polyimide raw materials.

[0005] This invention uses non-corrosive raw materials, has low equipment requirements, high safety, and uses a single reaction solvent, acetone, for repeated recycling. It can achieve the required purity without secondary purification, is easy to operate, produces less waste, is environmentally friendly, and is suitable for industrial production.

[0006] This invention is achieved through the following technical solution:

[0007] A simple method for preparing photosensitive polyimide raw materials includes the following steps:

[0008] 1) Using 2,3,5,6-tetrafluoro-1,4-phenylenediamine and m-nitrobenzoyl chloride as starting materials, N,N'-(perfluoro-1,4-phenylene)bis(3-nitrobenzoamide) was obtained by condensation reaction in the presence of ethyl acetate. The reaction route is as follows:

[0009]

[0010] 2) N,N'-(perfluoro-1,4-phenylene)bis(3-nitrobenzamide) was dissolved in ethyl acetate, and the final product was obtained under the action of formic acid, a catalyst, and hydrogen gas. The reaction route is as follows:

[0011]

[0012] A simple method for preparing photosensitive polyimide raw materials includes the following steps:

[0013] 1) Mix 2,3,5,6-tetrafluoro-1,4-phenylenediamine with ethyl acetate to form a homogeneous solution, and then add m-nitrobenzoyl chloride dissolved in ethyl acetate dropwise at 0-25℃. After the addition, keep the reaction at 15-30℃ for 3-4 hours. After the reaction, perform post-treatment to obtain the intermediate N,N'-(perfluoro-1,4-phenylene)bis(3-nitrobenzoamide);

[0014] 2) Add N,N'-(perfluoro-1,4-phenylene)bis(3-nitrobenzamide) to ethyl acetate and stir until completely dissolved. Add Pt-Pd-Fe / activated carbon ternary catalyst and formic acid. Transfer the entire mixture to a hydrogenation reactor. Purge with nitrogen to 0.5 MPa and then evacuate. Repeat this process 3-5 times. Heat the reactor to 50-60°C and then purge with hydrogen. The reaction ends when the pressure remains constant. After the reaction is complete, filter out the solid catalyst and add the mother liquor dropwise to the precipitate b. Filter, wash, and dry to obtain the final product.

[0015] According to a preferred embodiment of the present invention, in step 1), the post-treatment involves adding precipitate a to the reaction solution and stirring for 1-2 hours within 0.5-1 hours after the reaction. After the precipitate precipitates, the temperature is lowered to 0-10°C, and stirring is continued for 0.5-1 hours. The mixture is then filtered, washed with pure water, and dried at a temperature of 60-100°C and a vacuum degree of -0.090-0.095 MPa to obtain N,N'-(perfluoro-1,4-phenylene)bis(3-nitrobenzamide).

[0016] According to a preferred embodiment of the present invention, in step 1), the purity of the intermediate N,N'-(perfluoro-1,4-phenylene)bis(3-nitrobenzamide) obtained can reach more than 99%. The intermediate can be used directly, and the single reaction solvent ethyl acetate can be repeatedly recycled without secondary purification. The operation is simple and suitable for industrial production.

[0017] According to a preferred embodiment of the present invention, in step 1), the precipitate a is one of methanol, ethanol, isopropanol, and 1,4-dioxane.

[0018] According to a preferred embodiment of the present invention, in step 1), the mass ratio of the precipitate a to the ethyl acetate is (3-9):1, and the mass of the ethyl acetate is the total mass of acetone used to mix with 2,3,5,6-tetrafluoro-1,4-phenylenediamine and to dissolve m-nitrobenzoyl chloride.

[0019] In a further preferred embodiment, in step 1), the mass ratio of the precipitate a to the ethyl acetate is (3-6):1.

[0020] According to a preferred embodiment of the present invention, in step 1), the precipitate a can be easily separated from the solvent used in solvent recovery, which helps to improve product purity, reduce product loss and improve yield.

[0021] According to a preferred embodiment of the present invention, in step 1), the molar ratio of 2,3,5,6-tetrafluoro-1,4-phenylenediamine to m-nitrobenzoyl chloride is 1:(1.9-2.4).

[0022] More preferably, in step 1), the molar ratio of 2,3,5,6-tetrafluoro-1,4-phenylenediamine to m-nitrobenzoyl chloride is 1:(2.0-2.1).

[0023] According to a preferred embodiment of the present invention, in step 1), the mass ratio of 2,3,5,6-tetrafluoro-1,4-phenylenediamine to ethyl acetate is 1:(2.0-4.0).

[0024] According to a preferred embodiment of the present invention, in step 1), the mass ratio of m-nitrobenzoyl chloride to ethyl acetate is 1:(1.0-2.0).

[0025] According to a preferred embodiment of the present invention, in step 2), the mass ratio of the intermediate to the solvent ethyl acetate is 1:(6.5-10.5).

[0026] According to a preferred embodiment of the present invention, in step 2), the catalyst is a Pt-Pd-Fe / activated carbon composite catalyst, the amount of catalyst is 1-6% of the mass of the intermediate, and the amount of formic acid is 2-7% of the mass of the intermediate.

[0027] In the Pt-Pd-Fe / activated carbon composite catalyst of this invention, the proportion of platinum (Pt) is 1.0-4.0%, the proportion of palladium (Pd) is 1.0-9.0%, and the proportion of iron (Fe) is 0.6-1.8%.

[0028] According to a preferred embodiment of the present invention, in step 2), the amount of precipitate b is 1-8 times the mass of the hydrogenation mother liquor.

[0029] According to a preferred embodiment of the present invention, in step 2), the precipitate b is ice water at 0°C.

[0030] According to a preferred embodiment of the present invention, in step 2), the drop acceleration rate is 1-8 mL / min.

[0031] According to a preferred embodiment of the present invention, in step 2), after hydrogen gas is introduced, the pressure inside the reactor is 0.5-1 MPa. During the reaction, if the pressure is less than 0.5 MPa, hydrogen gas is added to the reactor. During the reaction, the hydrogen gas pressure is less than or equal to 1 MPa. The reaction ends when the pressure remains constant.

[0032] According to a preferred embodiment of the present invention, in step 2), the rinsing and drying process involves first rinsing with cold water at 5°C, then vacuum drying at 50°C, followed by rinsing with deionized water 2-3 times, and finally drying at 80°C.

[0033] Step 1) yields intermediate N,N'-(perfluoro-1,4-phenylene)bis(3-nitrobenzamide) having the structure described in Formula I:

[0034]

[0035] This invention utilizes the same solvent, ethyl acetate, in both the condensation and hydrogenation stages. First, in the condensation stage, ethyl acetate, as an aprotic polar solvent, avoids side reactions such as acyl chloride hydrolysis and alcoholysis, reduces steric hindrance, and promotes nucleophilic substitution. Second, in the hydrogenation stage, ethyl acetate effectively dissolves the intermediate, promotes hydrogen diffusion to the catalyst surface, avoids catalyst poisoning, ensures the synergistic effect of the Pt-Pd-Fe ternary catalyst, and significantly improves the selective reduction of nitro groups. The catalyst used in the hydrogenation stage is a novel composite catalyst, which improves mass transfer efficiency and synergistically suppresses side reactions. Formic acid provides an acidic environment, promoting nitro protonation and suppressing side reactions. This significantly increases the yield and productivity. The operation is simple, and the reaction conditions are mild.

[0036] The beneficial effects of this invention are as follows:

[0037] 1. This invention innovatively uses ethyl acetate as a reaction solvent to dissolve the materials. After the reaction is completed, the precipitate is added to obtain the target product with high yield and high purity. It is safer, more environmentally friendly, and the single reaction solvent can be repeatedly recycled and reused. The operation is simple and suitable for industrial production.

[0038] 2. The preparation method of the present invention is simple, does not require high temperature, and the product yield is high and the purity can reach more than 99%.

[0039] 3. The final product of this invention enriches the raw materials for preparing photosensitive polyimide. The photosensitive polyimide obtained has a perfluorinated structure that gives the material ultra-high thermal stability, while achieving extremely low dielectric properties through the nitro conjugation effect, which is significantly better than traditional polyimide. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to specific embodiments. The following description is merely exemplary and does not limit its scope of protection.

[0041] Unless otherwise specified, all raw materials used in the following examples are commercially available products.

[0042] In the examples, the Pt-Pd-Fe / activated carbon composite catalyst was prepared by the following method:

[0043] The supported activated carbon was pretreated by boiling in 10% hydrochloric acid for 1 hour and washing until neutral, then drying at 110℃. A 0.01 mol / L hydrochloric acid solution was prepared by mixing chloroplatinic acid, palladium chloride, and ferric chloride. The pretreated activated carbon was impregnated in a metal salt solution containing the target loading (2.0% Pt, 5.0% Pd, and 1.0% Fe), the pH was adjusted to 1, and the mixture was stirred for 2 hours. The pH was then adjusted to 7-9 with alkali. Hydrazine hydrate or sodium borohydride (molar ratio of metal element to reducing agent = 1:25) was added, and reduction was carried out at 80℃ for 3 hours. After cooling, the reaction solution was filtered, washed with deionized water until chloride ions were removed, and dried under vacuum at 60℃ to obtain a catalyst with both high activity and selectivity. Due to the synergistic effect of Pt-Pd-Fe, this system significantly suppressed side reactions (<1%) and exhibited a selectivity >99%.

[0044] Example 1

[0045] A simple method for preparing photosensitive polyimide raw materials, comprising the following steps:

[0046] 1) Add 229.78 g (1.238 mol) of m-nitrobenzoyl chloride to a beaker containing 229.78 g of ethyl acetate, stir well to obtain a m-nitrobenzoyl chloride solution;

[0047] 2) Add 110g (0.61mol) of 2,3,5,6-tetrafluoro-1,4-phenylenediamine to a three-necked flask containing 275g of ethyl acetate, stir until completely dissolved, and then cool to 20℃ to obtain a 2,3,5,6-tetrafluoro-1,4-phenylenediamine solution.

[0048] 3) The m-nitrobenzoyl chloride solution was added dropwise to the three-necked flask of step 2) using a peristaltic pump through a latex tube over a period of 0.5 h. After the addition was complete, the temperature was adjusted to 25 °C, and the reaction was continued for 4 h. After the reaction was completed, the reaction solution was added dropwise to 1514.34 g of methanol aqueous solution to precipitate the product. After the addition was completed, the mixture was stirred for 0.5 h, cooled to 10 °C, and stirred for another 0.5 h. The mixture was then filtered, washed with 2000 ml of pure water, and dried under vacuum at 85 °C and -0.095 MPa to obtain the intermediate N,N'-(perfluoro-1,4-phenylene)bis(3-nitrobenzoamide); the yield was 97.1%, and the purity was 98.52%.

[0049] 4) Add intermediate N,N'-(perfluoro-1,4-phenylene)bis(3-nitrobenzamide) to 7.5 times its mass of ethyl acetate and stir until completely dissolved. Add 2% by weight of Pt-Pd-Fe / activated carbon ternary catalyst and 2% by weight of 3% formic acid, and then transfer the entire mixture to a hydrogenation reactor. Purge with nitrogen to 0.5 MPa and then evacuate. Repeat this process 4 times. After heating the reactor to 55°C, introduce hydrogen gas at a pressure of 0.5-1 MPa. If the pressure drops below 0.5 MPa during the reaction, add hydrogen gas to the reactor. The hydrogen gas pressure should not exceed 1 MPa. The reaction ends when the pressure remains constant. After the reaction was completed, the solid catalyst was filtered out, and the mother liquor was added dropwise to 2.5 times the volume of the precipitate in ice water at 0℃ at a dropping rate of 1 ml / min. The mixture was then filtered, rinsed with cold water at 5℃, vacuum dried at 50℃, rinsed twice with deionized water, and dried at 80℃ to obtain the final product with a yield of 98.2% and a purity of 99.71%.

[0050] Example 2

[0051] A simple method for preparing photosensitive polyimide raw materials, comprising the following steps:

[0052] 1) Add 232.04 g (1.251 mol) of m-nitrobenzoyl chloride to a beaker containing 324.86 g of ethyl acetate, stir well to obtain a m-nitrobenzoyl chloride solution;

[0053] 2) Add 110g (0.61mol) of 2,3,5,6-tetrafluoro-1,4-phenylenediamine to a three-necked flask containing 330g of ethyl acetate, stir until completely dissolved, and then cool to 20℃ to obtain a 2,3,5,6-tetrafluoro-1,4-phenylenediamine solution.

[0054] 3) The m-nitrobenzoyl chloride solution was added dropwise to the three-necked flask of step 2) using a peristaltic pump through a latex tube over a period of 0.5 h. After the addition was complete, the temperature was adjusted to 25 °C, and the reaction was continued for 4 h. After the reaction was completed, the reaction solution was added dropwise to 2292.01 g of methanol aqueous solution to precipitate the product. After the addition was completed, the mixture was stirred for 0.5 h, cooled to 10 °C, and stirred for another 0.5 h. The mixture was then filtered, washed with 2500 ml of pure water, and dried under vacuum at 85 °C and -0.095 MPa to obtain the intermediate N,N'-(perfluoro-1,4-phenylene)bis(3-nitrobenzoamide) with a yield of 96.5% and a purity of 98.33%.

[0055] Step 4) is the same as in Example 1, which yields a final product with a yield of 97.3% and a purity of 99.49%.

[0056] Example 3

[0057] A simple method for preparing photosensitive polyimide raw materials, comprising the following steps:

[0058] 1) Add 233.17 g (1.257 mol) of m-nitrobenzoyl chloride to a beaker containing 419.71 g of ethyl acetate, stir well to obtain a m-nitrobenzoyl chloride solution;

[0059] 2) Add 110g (0.61mol) of 2,3,5,6-tetrafluoro-1,4-phenylenediamine to a three-necked flask containing 385g of ethyl acetate, stir until completely dissolved, and then cool to 20℃ to obtain a 2,3,5,6-tetrafluoro-1,4-phenylenediamine solution.

[0060] 3) The m-nitrobenzoyl chloride solution was added dropwise to the three-necked flask of step 2) using a peristaltic pump through a latex tube over a period of 0.5 h. After the addition was complete, the temperature was adjusted to 25 °C, and the reaction was continued for 4 h. After the reaction was completed, the reaction solution was added dropwise to 2736.01 g of methanol aqueous solution to precipitate the product. After the addition was completed, the mixture was stirred for 0.5 h, cooled to 10 °C, and stirred for another 0.5 h. The mixture was then filtered, washed with 3000 ml of pure water, and dried under vacuum at 85 °C and -0.095 MPa to obtain the intermediate N,N'-(perfluoro-1,4-phenylene)bis(3-nitrobenzoamide) with a yield of 96.8% and a purity of 98.45%.

[0061] Step 4) is the same as in Example 1, which yields a final product with a yield of 97.7% and a purity of 99.57%.

[0062] Comparative Example 1

[0063] A simple method for preparing photosensitive polyimide raw materials, comprising the following steps:

[0064] Add 282.98 g (1.525 mol) of m-nitrobenzoyl chloride to a beaker containing 424.47 g of toluene, stir well, and set aside. 110 g (0.61 mol) of 2,3,5,6-tetrafluoro-1,4-phenylenediamine was added to a three-necked flask containing 220 g of toluene and stirred until completely dissolved. After complete dissolution, the temperature was lowered to 25 °C. The prepared mixture was then added dropwise to the three-necked flask using a peristaltic pump through a latex tube over a period of 0.5 h. The temperature during the reaction should not exceed 35 °C. After the addition was complete, the temperature was adjusted to 30 °C, and the reaction continued for 2 h. After the reaction was complete, the reaction solution was added dropwise to 1933.41 g of methanol aqueous solution to precipitate the product. After the addition was complete, the temperature was raised to 60 °C and stirred for 1 h. The temperature was then lowered to 25 °C and stirred for another 0.5 h. The product was filtered, washed with 2000 ml of pure water, and dried under vacuum at 85-90 °C and -0.095 MPa to obtain the intermediate. The yield was 93.2%, and the purity was 94.65%.

[0065] The hydrogenation operation was carried out according to step 4) of Example 1, which yielded a final product with a yield of 94.8% and a purity of 96.39%.

[0066] Comparative Example 2

[0067] The method described in the same way as in Example 1, except that,

[0068] Step 1) N-methylpyrrolidone was used instead of ethyl acetate, and the rest was carried out as in Example 1. The product yield was 94.3% and the purity was 95.4%.

[0069] Comparative Example 3

[0070] The method described in the same way as in Example 1, except that,

[0071] Step 1) involved replacing ethyl acetate with ethylene glycol butyl ether, while proceeding as in Example 1. The product yield was 93.8%, and the purity was 96.1%.

[0072] Comparative Example 4

[0073] The method described in the same way as in Example 1, except that,

[0074] Step 1) involved replacing ethyl acetate with methanol, while proceeding as in Example 1. The product yield was 93.2%, and the purity was 93.5%.

[0075] In summary, comparative examples 2-4 show that replacing ethyl acetate with N-methylpyrrolidone, ethylene glycol butyl ether, and methanol significantly reduces the yield of the product.

[0076] Comparative Example 5

[0077] The method described in the same way as in Example 1, except that,

[0078] The composite catalyst was replaced with Pd / c, and other procedures were carried out as in Example 1. The product yield was 94.2%, and the purity was 94.10%.

[0079] Experimental Example 1

[0080] 1. The amount of ethyl acetate used to dissolve m-nitrobenzoyl chloride in Example 1 was changed to 92.5g, 150.5g, 505.51g, and 574.45g, respectively. Other steps were carried out as in Example 1. After the reaction was completed, the reaction yield and purity were compared. The results are shown in Table 1.

[0081] Table 1

[0082]

[0083]

[0084] As can be seen from the data in Table 1, if the amount of ethyl acetate is too small, the yield is low. As the amount of ethyl acetate increases, the yield gradually increases. However, when the amount of ethyl acetate is too large, the yield begins to decline. Excessive use of ethyl acetate affects the product yield and also causes side reactions that affect the product purity.

[0085] 2. Change the reaction time of the condensation stage in step 3) of Example 1. The reaction times are 5h, 4h, 3.5h, 2h, 1h and 0.5h respectively; the rest are carried out as in Example 1. After the reaction is completed, the reaction yield and purity are compared. The results are shown in Table 2.

[0086] Table 2

[0087] reaction time Yield % purity% 4.5h 97.7 98.35 3.5h 97.8 98.41 3.0h 97.1 98.21 2.5h 96.3 97.85 1.5h 94.9 97.46 0.5h 93.6 97.11

[0088] As can be seen from the data in Table 2, if the reaction time is too short, the reaction will be incomplete, resulting in residual raw materials and low yield and purity. Extending the reaction time will increase the yield, but if the reaction time is too long, the reaction yield will decrease to some extent. This is because a long reaction time may produce side reactions and also lead to a decrease in purity.

[0089] Experimental Example 2

[0090] The final product is used to prepare photosensitive polyimide.

[0091] Preparation process: 2.257g of the product obtained in Example 1 and 1.177g of biphenyl dianhydride (BPDA) were used as monomers. The monomers were added to a mixed solvent of 11.25ml m-cresol and 3.75ml N-methylpyrrolidone, and 0.0024g of DMAP catalyst were added at the same time. The mixture was dissolved at 80°C for 2 hours under nitrogen protection, and the temperature was gradually increased to 200°C at a rate of 30°C / h and maintained for 6 hours to complete the polymerization. After precipitation with 80ml methanol and 20ml water, the reaction solution was purified by Soxhlet extraction (methanol reflux for 12 hours) and vacuum dried at 100°C for 24 hours to obtain the photosensitive polyimide polymer.

[0092] Film formation: The photosensitive polyimide polymer was dissolved in 12wt% NMP solution, filtered through a 0.22μm PTFE filter membrane, and then dried in a stepwise manner (80℃→150℃→200℃, vacuum≤10Pa) to obtain a photosensitive polyimide film. The imidization was ensured to be complete by FT-IR monitoring throughout the process.

[0093] The mechanical properties, stability, dielectric properties, and photolithographic resolution of the photosensitive polyimide film were tested, and the test results are shown in Table 3.

[0094] Table 3

[0095] Test Name Example 1 Example 2 Comparative Example 1 Tensile strength / MPa 218 215 214 <![CDATA[Thermal decomposition temperature / Td5%]]> 520 515 500 <![CDATA[Glass transition temperature / Td5%]]> 355 352 345 Dielectric constant / 1MHz 2.74 2.81 2.85 Dielectric loss / 1MHz 0.002 0.003 0.003 Imidification degree / % 98.3 98.1 97.6 Photolithography resolution / μm 3.0 3.5 3.5

[0096] As shown in Table 3, this product exhibits significant comprehensive advantages in polyimide films. Its perfluorinated structure endows the material with ultra-high thermal stability, while achieving extremely low dielectric properties through the nitro conjugation effect, which is significantly superior to traditional polyimides. The rigid molecular chain design brings excellent mechanical strength, and combined with photosensitive groups, it enables high-resolution photolithography at the 3μm level, meeting the precision processing requirements of 5G high-frequency circuits and flexible displays. Strict imidization control and step drying process further ensure the structural integrity of the film, making it an ideal material for high-end fields such as aerospace and electronic packaging.

Claims

1. A simple method for preparing photosensitive polyimide raw materials, comprising the following steps: 1) Using 2,3,5,6-tetrafluoro-1,4-phenylenediamine and m-nitrobenzoyl chloride as starting materials, N,N'-(perfluoro-1,4-phenylene)bis(3-nitrobenzoamide) was obtained by condensation reaction in the presence of ethyl acetate. The reaction route is as follows: 2) N,N'-(perfluoro-1,4-phenylene)bis(3-nitrobenzamide) was dissolved in ethyl acetate, and the final product was obtained under the action of formic acid, a catalyst, and hydrogen gas. The reaction route is as follows:

2. A simple method for preparing photosensitive polyimide raw materials, comprising the following steps: 1) Mix 2,3,5,6-tetrafluoro-1,4-phenylenediamine with ethyl acetate to form a homogeneous solution, and then add m-nitrobenzoyl chloride dissolved in ethyl acetate dropwise at 0-25℃. After the addition, keep the reaction at 15-30℃ for 3-4 hours. After the reaction, perform post-treatment to obtain the intermediate N,N'-(perfluoro-1,4-phenylene)bis(3-nitrobenzoamide); 2) Add N,N'-(perfluoro-1,4-phenylene)bis(3-nitrobenzamide) to ethyl acetate and stir until completely dissolved. Add Pt-Pd-Fe / activated carbon ternary catalyst and formic acid. Transfer the entire mixture to a hydrogenation reactor. Purge with nitrogen to 0.5 MPa and then evacuate. Repeat this process 3-5 times. Heat the reactor to 50-60°C and then purge with hydrogen. The reaction ends when the pressure remains constant. After the reaction is complete, filter out the solid catalyst and add the mother liquor dropwise to the precipitate b. Filter, wash, and dry to obtain the final product.

3. The preparation method according to claim 2, characterized in that, In step 1), the post-treatment involves adding precipitate a to the reaction solution and stirring for 1-2 hours within 0.5-1 hours after the reaction. After the precipitate precipitates, the temperature is lowered to 0-10℃, and stirring is continued for 0.5-1 hours. The mixture is then filtered, washed with pure water, and dried at a temperature of 60-100℃ and a vacuum degree of -0.090-0.095 MPa to obtain N,N'-(perfluoro-1,4-phenylene)bis(3-nitrobenzamide).

4. The preparation method according to claim 2, characterized in that, In step 1), the precipitate a is one of methanol, ethanol, isopropanol, and 1,4-dioxane. The mass ratio of precipitate a to ethyl acetate is (3-9):

1. The mass of ethyl acetate is the total mass of acetone used to mix with 2,3,5,6-tetrafluoro-1,4-phenylenediamine and to dissolve m-nitrobenzoyl chloride.

5. The preparation method according to claim 2, characterized in that, In step 1), the molar ratio of 2,3,5,6-tetrafluoro-1,4-phenylenediamine to m-nitrobenzoyl chloride is 1:(1.9-2.4).

6. The preparation method according to claim 2, characterized in that, In step 1), the mass ratio of 2,3,5,6-tetrafluoro-1,4-phenylenediamine to ethyl acetate is 1:(2.0-4.0).

7. The preparation method according to claim 2, characterized in that, In step 1), the mass ratio of m-nitrobenzoyl chloride to ethyl acetate is 1:(1.0-2.0), and the mass ratio of the intermediate to the solvent ethyl acetate is 1:(6.5-10.5).

8. The preparation method according to claim 2, characterized in that, In step 2), the catalyst is a Pt-Pd-Fe / activated carbon composite catalyst, the amount of catalyst is 1-6% of the mass of the intermediate, and the amount of formic acid is 2-7% of the mass of the intermediate.

9. The preparation method according to claim 2, characterized in that, In step 2), the amount of precipitate b is 1-8 times the mass of the hydrogenation mother liquor, precipitate b is 0℃ ice water, and the dropping acceleration rate is 1-8 mL / min.

10. The preparation method according to claim 2, characterized in that, In step 2), after hydrogen is introduced, the pressure inside the reactor is 0.5-1 MPa. During the reaction, if the pressure is less than 0.5 MPa, hydrogen is added to the reactor. During the reaction, the hydrogen pressure is less than or equal to 1 MPa. The reaction ends when the pressure remains constant. The rinsing and drying process involves first rinsing with cold water at 5°C, then vacuum drying at 50°C, then rinsing with deionized water 2-3 times, and finally drying at 80°C.

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