Preparation process of high-purity diamine monomer

Abstract

The invention belongs to the technical field of organic synthesis, and particularly discloses a preparation process of a high-purity diamine monomer. The preparation method comprises the following steps: preparing di (4-nitrophenyl) adipate by taking p-nitrophenol and adipyl chloride as raw materials, reducing the di (4-nitrophenyl) adipate into di (4-aminophenyl) adipate by taking iron powder as a catalyst, and sequentially dissolving with an organic solvent, adsorbing with an adsorbent, performing rotary evaporation, soaking and washing, filtering and drying in the subsequent purification process, thereby obtaining the di (4-aminophenyl) adipate. Impurities are gradually removed, so that the purity of the di (4-aminophenyl) adipate can be effectively improved, and the content of metal ions in the di (4-aminophenyl) adipate is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and in particular relates to a preparation process of a high-purity diamine monomer. Background Art

[0002] As a type of high-performance polymer, polyimide has demonstrated excellent application performance in many fields. In particular, in the field of liquid crystal display, polyimide-based liquid crystal alignment agents play a key role, which can guide liquid crystal molecules to be arranged in an orderly manner in a specific direction, thereby ensuring that the liquid crystal display has good display effects, such as high contrast, wide viewing angle and fast response speed.

[0003] Diamine monomer is one of the important raw materials for synthesizing polyimide. Its purity directly affects the synthesis process of polyimide and the performance of the final product. Diamine monomer with low purity may cause chain termination, abnormal crosslinking and other problems in the polymerization reaction, thereby affecting the molecular weight and distribution of polyimide, resulting in the film-forming performance, orientation stability and other properties of the liquid crystal alignment agent. In particular, when metal ions exist in the diamine monomer, it will seriously affect the performance of the polyimide. For example, when metal iron ions and copper ions exist in the diamine monomer, they can act as catalysts or initiators to induce unnecessary side reactions during the polymerization process, such as oxidation and decomposition. These side reactions will not only change the chemical structure of the polyimide, but may also cause the polymer color to darken, affecting the optical properties of the liquid crystal alignment agent.

[0004] At present, although the purification methods of diamine monomers (such as recrystallization, column chromatography, ion exchange resin method, etc.) can remove impurities to a certain extent, they have problems such as complex operation, high cost, and large yield loss. Therefore, how to improve the purity of diamine monomers and effectively reduce the metal ion content is a technical problem that needs to be solved in the preparation of high-performance liquid crystal alignment agent polyimide. Summary of the invention

[0005] The object of the present invention is to provide a preparation process of a high-purity diamine monomer to solve the problems of low purity of the diamine monomer and high content of metal ions in the diamine monomer in the prior art.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A process for preparing a high-purity diamine monomer comprises the following steps:

[0008] Step S1, using p-nitrophenol and adipoyl chloride as raw materials to prepare di(4-nitrophenyl) adipate;

[0009] Step S2, using the di(4-nitrophenyl)adipate obtained in step S1 as a raw material and iron powder as a catalyst to prepare a crude product of di(4-aminophenyl)adipate;

[0010] Step S3, dissolving the crude di(4-aminophenyl)adipate product obtained in step S2 in an organic solvent, filtering once, adsorbing with an adsorbent, rotary evaporation, soaking and washing, filtering twice and drying in sequence to prepare di(4-aminophenyl)adipate;

[0011] The adsorbent is prepared by modifying silica gel with a silane coupling agent.

[0012] Furthermore, the reaction formula of step S1 is as follows:

[0013]

[0014] Furthermore, the reaction formula of step S2 is as follows:

[0015]

[0016] Further, the step S1 is specifically as follows: p-nitrophenol is added to dichloromethane to obtain a reaction solution, the reaction solution is cooled to 0°C under an ice-water bath, adipoyl chloride is first added dropwise to the reaction solution while maintaining stirring, and triethylamine is then added dropwise, stirring is continued after the addition is completed, the ice-water bath is removed, and the mixture is placed at room temperature overnight, and then filtered to obtain a filtrate A, the filtrate A is subjected to rotary evaporation to obtain a rotary evaporation solid, and the rotary evaporation solid is sequentially subjected to soaking, washing, filtering and drying to obtain di(4-nitrophenyl) adipate;

[0017] The step S2 specifically comprises: uniformly mixing the di(4-nitrophenyl)adipate, ammonium chloride and iron powder obtained in step S1, adding ethanol aqueous solution under nitrogen protection, heating to 60-70° C., reacting for 2-3 hours, cooling to room temperature, and filtering to obtain a filter cake, i.e., a crude product of di(4-aminophenyl)adipate;

[0018] The step S3 specifically comprises: adding the crude product of di(4-aminophenyl)adipate obtained in step S2 to an organic solvent, stirring, heating to 60-70° C., filtering once while hot, collecting filtrate B, heating filtrate B, heating to 60-70° C., adding an adsorbent while hot, stirring evenly to obtain a filtrate product, subjecting the filtrate product to rotary evaporation to obtain a solid product, and sequentially soaking and washing the solid product after rotary evaporation, filtering twice and drying to obtain di(4-aminophenyl)adipate.

[0019] Furthermore, in step S1, the mass ratio of p-nitrophenol, adipoyl chloride, triethylamine and dichloromethane is (2.9-3.2):(1.8-2.0):(4.0-4.4):(20.0-40.0).

[0020] Further, in step S2, the mass ratio of bis(4-nitrophenyl) adipate, ammonium chloride, iron powder and aqueous ethanol solution is (3.5 - 4.1):(5.6 - 6.4):(4.8 - 5.5):(20.0 - 40.0).

[0021] Further, the concentration of the aqueous ethanol solution is 40 - 60 wt%.

[0022] Further, in step S3, the mass ratio of the crude bis(4-aminophenyl) adipate product to the organic solvent is 1:(7 - 10);

[0023] The mass ratio of the filtrate B to the adsorbent is 10:(1 - 2).

[0024] Further, both the soaking and washing process in step S1 and the soaking and washing process in step S3 include the following steps:

[0025] Step (1), wash once with high-purity water and then filter;

[0026] Step (2), wash once with ethanol.

[0027] Further, in step S3, the organic solvent is at least one of tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,4-dioxane.

[0028] Further, the preparation method of the adsorbent includes the following steps: uniformly mix silane coupling agent, water and ethanol according to the mass ratio of 1:1:(10 - 20), adjust the pH to 4 - 6, stir for 5 - 20 min, then add silica gel which is 10 - 30 times the mass of the silane coupling agent, heat to 50 - 60 °C, stir for 6 - 10 h, filter, wash and dry to obtain the adsorbent.

[0029] Further, the silane coupling agent is obtained by mixing KH-550 and KH-590 in a mass ratio of (1 - 5):2.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] 1. In the present invention, first, using p-nitrophenol and adipoyl chloride as raw materials, bis(4-nitrophenyl) adipate is prepared, and then using iron powder as a catalyst, bis(4-nitrophenyl) adipate is reduced to bis(4-aminophenyl) adipate. In the subsequent purification process, organic solvent dissolution, adsorbent adsorption, rotary evaporation, soaking and washing, filtration and drying are carried out in sequence to gradually remove impurities, which can effectively improve the purity of bis(4-aminophenyl) adipate and greatly reduce the metal ion content in bis(4-aminophenyl) adipate.

[0032] 2. The adsorbent of the present invention is silica gel modified with silane coupling agent. The amino group and mercapto group in the silane coupling agent can form coordination bonds with metal ions, effectively adsorbing metal ion impurities, thereby significantly reducing the content of metal ions in the diamine monomer and improving the product quality. Description of the Drawings

[0033] The drawings described herein are used to provide a further understanding of the present invention and form a part of this application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0034] Figure 1 is the infrared spectrum of bis(4-aminophenyl) adipate prepared in Example 1 of the present invention;

[0035] Figure 2 is the nuclear magnetic resonance hydrogen spectrum of bis(4-aminophenyl) adipate prepared in Example 1 of the present invention. Detailed Embodiments

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without any creative work shall fall within the protection scope of the present invention.

[0037] Example 1

[0038] This example provides a preparation process for high-purity diamine monomer, including the following steps:

[0039] Step S0: Uniformly mix a silane coupling agent (obtained by mixing KH-550 and KH-590 in a mass ratio of 3:2), water, and ethanol in a mass ratio of 1:1:10, adjust the pH to 4, stir for 5 min, then add silica gel 10 times the mass of the silane coupling agent (i.e., the addition amount of silica gel is 10 times the mass of the silane coupling agent), heat to 50 °C, stir for 6 h, filter, wash, and dry to obtain the adsorbent;

[0040] Step S1: Add 2.9 g of p-nitrophenol to 20.0 g of dichloromethane to obtain a reaction solution. Under an ice-water bath, the reaction solution is cooled to 0 °C. While stirring at a speed of 400 r / min, first add 1.8 g of adipoyl chloride to the reaction solution, then add 4.0 g of triethylamine dropwise. After the dropwise addition is completed, continue to stir for 1 h, remove the ice-water bath, and let it stand overnight at room temperature. After the reaction solution is filtered, filtrate A is obtained. Filtrate A is rotary evaporated to obtain a rotary evaporation solid. The rotary evaporation solid is first washed once with high-purity water, then filtered, washed once with ethanol, filtered again, and dried to obtain bis(4-nitrophenyl) adipate;

[0041] Step S2: Mix 3.5 g of bis(4-nitrophenyl) adipate, 5.6 g of ammonium chloride, and 4.8 g of iron powder obtained in Step S1 evenly. Under nitrogen protection, add 20.0 g of an ethanol aqueous solution (concentration: 60 wt%). Heat the mixture to 60 °C and react for 2 h. Then cool it to room temperature. After filtration, a filter cake, i.e., the crude product of bis(4-aminophenyl) adipate, is obtained.

[0042] Step S3: Add the filter cake obtained in Step S2 to 1,4-dioxane with a mass 7 times that of the filter cake (i.e., the mass ratio of the filter cake to 1,4-dioxane is 1:7). Stir and heat the mixture to 60 °C. Then filter it while it is hot and collect filtrate B. Heat filtrate B to 60 °C and add the adsorbent obtained in Step S0 while it is hot (the mass ratio of filtrate B to the adsorbent is 10:1). Stir evenly to obtain a filtrate product. The filtrate product is subjected to rotary evaporation to obtain a solid product. The solid product after rotary evaporation is first washed once with high-purity water, then filtered, washed once with ethanol, then filtered again, and dried at 45 °C to obtain bis(4-aminophenyl) adipate.

[0043] Example 2

[0044] This example provides a preparation process for a high-purity diamine monomer, including the following steps:

[0045] Step S0: Uniformly mix a silane coupling agent (obtained by mixing KH-550 and KH-590 in a mass ratio of 1:2), water, and ethanol in a mass ratio of 1:1:15. Adjust the pH to 5, stir for 15 min, then add silica gel with a mass 20 times that of the silane coupling agent (i.e., the addition amount of silica gel is 20 times the mass of the silane coupling agent). Heat the mixture to 55 °C and stir for 8 h. Then filter, wash, and dry to obtain an adsorbent.

[0046] Step S1: Add 3.05 g of p-nitrophenol to 30.0 g of dichloromethane to obtain a reaction solution. Under an ice-water bath, cool the reaction solution to 0 °C. While stirring at a speed of 800 r / min, first add 1.95 g of adipoyl chloride dropwise to the reaction solution, and then add 4.22 g of triethylamine dropwise. After the addition is completed, continue stirring for 1.5 h. Remove the ice-water bath and let it stand overnight at room temperature. After filtering the reaction solution, obtain filtrate A. Filtrate A is subjected to rotary evaporation to obtain a rotary evaporation solid. The rotary evaporation solid is first washed once with high-purity water, then filtered, washed once with ethanol, filtered again, and dried to obtain bis(4-nitrophenyl) adipate.

[0047] Step S2: Mix 3.85 g of bis(4-nitrophenyl) adipate, 5.85 g of ammonium chloride and 5.25 g of iron powder obtained in Step S1 evenly. Under nitrogen protection, add 30.0 g of an ethanol aqueous solution (concentration: 50 wt%). Heat the mixture to 65 °C and react for 2.5 h. Then cool it to room temperature. After filtration, a filter cake, i.e., the crude product of bis(4-aminophenyl) adipate, is obtained.

[0048] Step S3: Add the filter cake obtained in Step S2 into 1,4-dioxane which is 9 times the mass of the filter cake (i.e., the mass ratio of the filter cake to 1,4-dioxane is 1:9). Stir the mixture and heat it to 65 °C. Then filter it while it is hot and collect filtrate B. Heat filtrate B to 65 °C and add the adsorbent obtained in Step S0 while it is hot (the mass ratio of filtrate B to the adsorbent is 10:1.5). Stir evenly to obtain a filtrate product. The filtrate product is subjected to rotary evaporation to obtain a solid product. Wash the solid product obtained after rotary evaporation once with high-purity water, filter it, then wash it once with ethanol and filter it again. Dry it at 50 °C to obtain bis(4-aminophenyl) adipate.

[0049] Example 3

[0050] This example provides a preparation process of a high-purity diamine monomer, which includes the following steps:

[0051] Step S0: Mix a silane coupling agent (obtained by mixing KH-550 and KH-590 in a mass ratio of 5:2), water and ethanol evenly according to a mass ratio of 1:1:20. Adjust the pH to 6. After stirring for 20 min, add silica gel which is 30 times the mass of the silane coupling agent (i.e., the addition amount of silica gel is 30 times the mass of the silane coupling agent). Heat the mixture to 60 °C and stir for 10 h. Then filter, wash and dry it to obtain an adsorbent.

[0052] Step S1: Add 3.2 g of p-nitrophenol into 40.0 g of dichloromethane to obtain a reaction solution. Under an ice-water bath, cool the reaction solution to 0 °C. While stirring at a speed of 1000 r / min, first add 2.00 g of adipoyl chloride to the reaction solution, and then add 4.4 g of triethylamine dropwise. After the addition is completed, continue stirring for 2 h. Remove the ice-water bath and let it stand overnight at room temperature. After filtering the reaction solution, obtain filtrate A. Subject filtrate A to rotary evaporation to obtain a rotary evaporation solid. Wash the rotary evaporation solid once with high-purity water, filter it, then wash it once with ethanol, filter it again and dry it to obtain bis(4-nitrophenyl) adipate.

[0053] Step S2: Mix 4.1 g of bis(4-nitrophenyl) adipate, 6.4 g of ammonium chloride and 5.5 g of iron powder obtained in Step S1 evenly. Under nitrogen protection, add 40.0 g of an ethanol aqueous solution (concentration: 40 wt%). Heat the mixture to 70 °C and react for 3 h. Then cool it to room temperature. After filtration, a filter cake, i.e., the crude product of bis(4-aminophenyl) adipate, is obtained.

[0054] Step S3: Add the filter cake obtained in Step S2 into ethylene glycol dimethyl ether with a mass 10 times that of the filter cake (i.e., the mass ratio of the filter cake to ethylene glycol dimethyl ether is 1:10), stir, heat up to 70 °C, and filter while it is hot to collect filtrate B; Heat filtrate B, heat up to 70 °C, and add the adsorbent obtained in Step S0 while it is hot (the mass ratio of filtrate B to the adsorbent is 5:1), stir evenly to obtain a filtrate product, and the filtrate product is subjected to rotary evaporation to obtain a solid product; The solid product after rotary evaporation is first washed once with high-purity water, filtered, then washed once with ethanol, filtered again, and dried at 55 °C to obtain bis(4-aminophenyl) adipate.

[0055] Comparative Example 1

[0056] This comparative example provides a preparation process of a high-purity diamine monomer, including the following steps:

[0057] Step S0: Uniformly mix a silane coupling agent (KH-550), water, and ethanol according to a mass ratio of 1:1:10, adjust the pH to 4, stir for 5 min, then add silica gel with a mass 10 times that of the silane coupling agent (i.e., the addition amount of silica gel is 10 times the mass of the silane coupling agent), heat to 50 °C, stir for 6 h, filter, wash, and dry to obtain an adsorbent;

[0058] Step S1: Add 2.9 g of p-nitrophenol into 20.0 g of dichloromethane to obtain a reaction solution. Under an ice-water bath, the reaction solution is cooled to 0 °C. While stirring at a speed of 400 r / min, first add 1.8 g of adipoyl chloride to the reaction solution, then add 4.0 g of triethylamine. After the addition is completed, continue to stir for 1 h, remove the ice-water bath, and leave it at room temperature overnight. After the reaction solution is filtered, filtrate A is obtained. Filtrate A is subjected to rotary evaporation to obtain a rotary evaporation solid. The rotary evaporation solid is first washed once with high-purity water, filtered, then washed once with ethanol, filtered again, and dried to obtain bis(4-nitrophenyl) adipate;

[0059] Step S2: Mix 3.5 g of bis(4-nitrophenyl) adipate obtained in Step S1, 5.6 g of ammonium chloride, and 4.8 g of iron powder evenly. Under nitrogen protection, add 20.0 g of an ethanol aqueous solution (concentration 60 wt%), heat up to 60 °C, react for 2 h, then cool to room temperature, and after filtration, obtain a filter cake, which is the crude product of bis(4-aminophenyl) adipate;

[0060] Step S3: Add the filter cake obtained in Step S2 into 1,4-dioxane which is 7 times the mass of the filter cake (i.e., the mass ratio of the filter cake to 1,4-dioxane is 1:7), stir, heat up to 60 °C, and filter while it is hot to collect filtrate B; Heat filtrate B, heat up to 60 °C, and add the adsorbent obtained in Step S0 while it is hot (the mass ratio of filtrate B to the adsorbent is 10:1), stir evenly to obtain a filtrate product. The filtrate product is subjected to rotary evaporation to obtain a solid product; The solid product after rotary evaporation is first washed once with high-purity water and then filtered, and then washed once with ethanol and filtered again, and dried at 45 °C to obtain bis(4-aminophenyl) adipate.

[0061] Comparative Example 2

[0062] This comparative example provides a preparation process of a high-purity diamine monomer, including the following steps:

[0063] Step S0: Uniformly mix a silane coupling agent (KH-590), water, and ethanol in a mass ratio of 1:1:10, adjust the pH to 4, stir for 5 min, then add silica gel which is 10 times the mass of the silane coupling agent (i.e., the addition amount of silica gel is 10 times the mass of the silane coupling agent), heat to 50 °C, stir for 6 h, filter, wash, and dry to obtain an adsorbent;

[0064] Step S1: Add 2.9 g of p-nitrophenol to 20.0 g of dichloromethane to obtain a reaction solution. Under an ice-water bath, the reaction solution is cooled to 0 °C. While stirring at a speed of 400 r / min, first add 1.8 g of adipoyl chloride to the reaction solution, and then add 4.0 g of triethylamine dropwise. After the addition is completed, continue to stir for 1 h. Remove the ice-water bath and let it stand overnight at room temperature. After the reaction solution is filtered, filtrate A is obtained. Filtrate A is subjected to rotary evaporation to obtain a rotary evaporation solid. The rotary evaporation solid is first washed once with high-purity water and then filtered, and then washed once with ethanol, filtered again, and dried to obtain bis(4-nitrophenyl) adipate;

[0065] Step S2: Mix 3.5 g of the bis(4-nitrophenyl) adipate obtained in Step S1, 5.6 g of ammonium chloride, and 4.8 g of iron powder evenly. Under nitrogen protection, add 20.0 g of an ethanol aqueous solution (concentration 60 wt%) and heat up to 60 °C. After reacting for 2 h, cool to room temperature, and filter to obtain a filter cake, which is the crude product of bis(4-aminophenyl) adipate;

[0066] Step S3: Add the filter cake obtained in Step S2 into 1,4-dioxane which is 7 times the mass of the filter cake (i.e., the mass ratio of the filter cake to 1,4-dioxane is 1:7), stir, heat up to 60 °C, and filter while it is hot to collect filtrate B; Heat filtrate B, heat up to 60 °C, and add the adsorbent obtained in Step S0 while it is hot (the mass ratio of filtrate B to the adsorbent is 10:1), stir evenly to obtain a filtrate product. The filtrate product is subjected to rotary evaporation to obtain a solid product; The solid product after rotary evaporation is first washed once with high-purity water, then filtered, then washed once with ethanol, then filtered, and dried at 45 °C to obtain bis(4-aminophenyl) adipate.

[0067] Comparative Example 3

[0068] This comparative example provides a preparation process for high-purity diamine monomers, including the following steps:

[0069] Step S0: Uniformly mix a silane coupling agent (obtained by mixing KH-550 and KH-590 in a mass ratio of 3:2), water, and ethanol in a mass ratio of 1:1:10, adjust the pH to 4, stir for 5 min, then add silica gel which is 10 times the mass of the silane coupling agent (i.e., the addition amount of silica gel is 10 times the mass of the silane coupling agent), heat to 50 °C, stir for 6 h, filter, wash, and dry to obtain an adsorbent;

[0070] Step S1: Add 2.9 g of p-nitrophenol into 20.0 g of dichloromethane to obtain a reaction solution. Under an ice-water bath, the reaction solution is cooled to 0 °C. While stirring at a speed of 400 r / min, first add 1.8 g of adipoyl chloride dropwise to the reaction solution, then add 4.0 g of triethylamine dropwise. After the addition is completed, continue to stir for 1 h, remove the ice-water bath, and leave it at room temperature overnight. After the reaction solution is filtered, filtrate A is obtained. Filtrate A is subjected to rotary evaporation to obtain a rotary evaporation solid. The rotary evaporation solid is first washed once with high-purity water, then filtered, then washed once with ethanol, then filtered again, and dried to obtain bis(4-nitrophenyl) adipate;

[0071] Step S2: Mix 3.5 g of the bis(4-nitrophenyl) adipate obtained in Step S1, 5.6 g of ammonium chloride, and 4.8 g of iron powder evenly. Under nitrogen protection, add 20.0 g of an ethanol aqueous solution (concentration 60 wt%) and heat up to 60 °C. After reacting for 2 h, cool to room temperature, and after filtration, obtain a filter cake, which is the crude product of bis(4-aminophenyl) adipate;

[0072] Step S3: Add the filter cake obtained in Step S2 into 1,4-dioxane which is 7 times the mass of the filter cake (i.e., the mass ratio of the filter cake to 1,4-dioxane is 1:7), stir, heat up to 60 °C, and filter while it is hot to collect filtrate B; Heat filtrate B, heat up to 60 °C, and add the adsorbent obtained in Step S0 while it is hot (the mass ratio of filtrate B to the adsorbent is 10:1), stir evenly to obtain a filtrate product, and the filtrate product is subjected to rotary evaporation to obtain bis(4-aminophenyl) adipate.

[0073] Test results

[0074] The metal ion contents (ppb) in the filter cake obtained in Step S2 and the bis(4-aminophenyl) adipate obtained in Step S3 in Examples 1-3 and Comparative Examples 1-3 were detected by ICP-MS, and the specific results are shown in Table 1.

[0075] Table 1

[0076]

[0077]

[0078] Note: In Table 1, the data presentations of Examples 1-3 and Comparative Examples 1-3 both include two groups of key detection data: the data in the left column represent the metal ion contents (ppb) in the filter cake obtained in Step S2, and the data in the right column correspond to the metal ion contents (ppb) in the bis(4-aminophenyl) adipate obtained in Step S3. The two columns of data are used to reflect the metal impurity removal effects at different stages.

[0079] By analyzing and calculating the total metal ion contents in the bis(4-aminophenyl) adipate obtained in Step S3 in Examples 1-3 and Comparative Examples 1-3 in Table 1 and comparing the experimental data, it can be seen that the total metal ion contents in the bis(4-aminophenyl) adipate obtained in Step S3 in Examples 1-3 are significantly lower than those in the bis(4-aminophenyl) adipate obtained in Step S3 in Comparative Examples 1-3. This comparison result fully confirms that in the preparation process of the high-purity diamine monomer provided by the present invention, there are significant technical advantages in metal ion removal, which can effectively improve the product purity and thus improve the product quality.

[0080] Based on the data in Table 1, a comparative analysis of Example 1, Comparative Example 1, and Comparative Example 2 is as follows: In the adsorbent provided in Example 1, the raw material silane coupling agent uses a compounding system of KH-550 and KH-590 with a mass ratio of 3:2. In the adsorbents provided in Comparative Example 1 and Comparative Example 2, the raw material silane coupling agents use single KH-550 and KH-590 respectively. Combining the data in Table 1, the total content of metal ions in bis(4-aminophenyl) adipate obtained in step S3 in Example 1, Comparative Example 1, and Comparative Example 2 is analyzed and calculated. By comparing the experimental data, it can be seen that by constructing a compounding system of silane coupling agents with a specific composition and applying it to the preparation of the adsorbent, the prepared adsorbent can effectively adsorb metal ion impurities, thereby significantly reducing the content of metal ions in the diamine monomer and further improving the product quality.

[0081] Through comparative analysis of the data in Table 1, the differences in the preparation processes and corresponding effects between Example 1 and Comparative Example 3 are as follows: Specifically, Comparative Example 3 omitted the subsequent treatment processes (including soaking and washing, filtration, and drying processes) of step S3 in the preparation process. According to the data shown in Table 1, the total content of metal ions in bis(4-aminophenyl) adipate prepared in step S3 of Example 1 and Comparative Example 3 was calculated. The results showed that the total amount of metal ions in bis(4-aminophenyl) adipate prepared in Example 1 was significantly lower than that in Comparative Example 3. The experimental data indicate that the combination of soaking and washing, filtration, and drying processes implemented after step S3 in Example 1 can reduce the content of metal ions in bis(4-aminophenyl) adipate and improve the purity index, thus verifying the key role of this process step in improving the purity of the product.

[0082] In addition, Figure 1 is the infrared spectrum of bis(4-aminophenyl) adipate prepared in Example 1. From this, it can be seen that N-H has two absorption peaks at 3360.13 cm -1 and 3201.35 cm -1 (symmetric and asymmetric stretching vibrations); the bending vibration of N-H overlaps with the benzene ring skeleton vibration and shows absorption peaks at 1604.09 cm -1 and 1508.89 cm -1 ; the bending vibration absorption of N overlaps with the out-of-plane bending vibration of =C-H on the benzene ring, and the C-N stretching vibration occurs at 1243.78 cm -1 ; and there is a strong absorption peak of C=O at 1742.18 cm -1 , fully indicating the formation of bis(4-aminophenyl) adipate.

[0083] Figure 21H NMR spectrum of bis(4-aminophenyl) adipate prepared in Example 1. The 1H NMR spectrum was interpreted as follows: 1H NMR (500 MHz, Chloroform-d) δ 7.13 - 7.06 (m, 1H), 6.67 - 6.60 (m, 1H), 3.94 (s, 1H), 2.50 (t, J = 8.3 Hz, 1H), 1.70 (d, J = 16.9 Hz, 0H); Figure 2 The total hydrogen integration in it is 5, which is consistent with the number of target products. The peak at 3.94 is the characteristic absorption peak of hydrogen atoms on the -NH2 bond.

[0084] In the description of this specification, the description with reference to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0085] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A preparation process of a high-purity diamine monomer, characterized in that, The following steps are involved: Step S1, using p-nitrophenol and adipoyl chloride as raw materials to prepare di(4-nitrophenyl) adipate; Step S2, using the di(4-nitrophenyl)adipate obtained in step S1 as a raw material and iron powder as a catalyst to prepare a crude product of di(4-aminophenyl)adipate; Step S3, dissolving the crude di(4-aminophenyl)adipate product obtained in step S2 in an organic solvent, filtering once, adsorbing with an adsorbent, rotary evaporation, soaking and washing, filtering twice and drying in sequence to prepare di(4-aminophenyl)adipate; The adsorbent is prepared by modifying silica gel with a silane coupling agent.

2. The preparation process of a high-purity diamine monomer according to claim 1, characterized in that, The step S1 specifically comprises: adding p-nitrophenol to dichloromethane to obtain a reaction solution, cooling the reaction solution to 0° C. under an ice-water bath, and then dripping adipoyl chloride and triethylamine into the reaction solution while maintaining stirring, continuing to stir after the dripping, removing the ice-water bath, and leaving the mixture at room temperature overnight, and then filtering to obtain a filtrate A, rotary evaporating the filtrate A to obtain a rotary evaporation solid, and sequentially soaking, washing, filtering and drying the rotary evaporation solid to obtain di(4-nitrophenyl) adipate; The step S2 specifically comprises: uniformly mixing the di(4-nitrophenyl)adipate, ammonium chloride and iron powder obtained in step S1, adding ethanol aqueous solution under nitrogen protection, heating to 60-70° C., reacting for 2-3 hours, cooling to room temperature, and filtering to obtain a filter cake, i.e., a crude product of di(4-aminophenyl)adipate; The step S3 specifically comprises: adding the crude product of di(4-aminophenyl)adipate obtained in step S2 to an organic solvent, stirring, heating to 60-70° C., filtering once while hot, collecting filtrate B, heating filtrate B, heating to 60-70° C., adding an adsorbent while hot, stirring evenly to obtain a filtrate product, subjecting the filtrate product to rotary evaporation to obtain a solid product, and sequentially soaking and washing the solid product after rotary evaporation, filtering twice and drying to obtain di(4-aminophenyl)adipate.

3. The preparation process of a high-purity diamine monomer according to claim 2, characterized in that, In step S1, the mass ratio of p-nitrophenol, adipoyl chloride, triethylamine and dichloromethane is (2.9-3.2):(1.8-2.0):(4.0-4.4):(20.0-40.0).

4. The preparation process of a high-purity diamine monomer according to claim 2, characterized in that, In step S2, the mass ratio of the di(4-nitrophenyl)adipate, ammonium chloride, iron powder and ethanol aqueous solution is (3.5-4.1):(5.6-6.4):(4.8-5.5):(20.0-40.0).

5. The preparation process of a high-purity diamine monomer according to claim 2, characterized in that, The concentration of the ethanol aqueous solution is 40-60wt%.

6. The preparation process of a high-purity diamine monomer according to claim 2, characterized in that, In step S3, the mass ratio of the crude di(4-aminophenyl)adipate to the organic solvent is 1:(7-10); The mass ratio of the filtrate B to the adsorbent is 10:(1-2).

7. The preparation process of a high-purity diamine monomer according to claim 2, characterized in that, The soaking and washing process in step S1 and the soaking and washing process in step S3 both include the following steps: Step (1), washing once with high-purity water and then filtering; Step (2), rinse once with ethanol.

8. The preparation process of a high-purity diamine monomer according to claim 1, characterized in that, In step S3, the organic solvent is at least one of tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether and 1,4-dioxane.

9. The preparation process of a high-purity diamine monomer according to claim 1, characterized in that, The preparation method of the adsorbent includes the following steps: uniformly mixing a silane coupling agent, water and ethanol according to a mass ratio of 1:1:(10 - 20), adjusting the pH to 4 - 6, stirring for 5 - 20 min, adding silica gel which is 10 - 30 times the mass of the silane coupling agent, heating to 50 - 60 °C, stirring for 6 - 10 h, filtering, washing and drying to obtain the adsorbent.

10. The preparation process of a high-purity diamine monomer according to claim 9, characterized in that, The silane coupling agent is obtained by mixing KH-550 and KH-590 according to a mass ratio of (1 - 5):2.

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