Process for the preparation of high purity n,n'-bis-(4-amino-2-chlorophenyl)-terephthalamide and its use

Abstract

The application discloses a preparation method of high-purity N,N'-bis(4-amino-2-chlorophenyl) terephthalamide with purity above 99.5% and application thereof. The high-purity N,N'-bis(4-amino-2-chlorophenyl) terephthalamide is prepared from 2-chloro-4-nitrophenylamine and terephthaloyl chloride as starting materials, and the preparation comprises the following steps: firstly, condensation reaction is carried out to obtain N,N'-bis(4-nitro-2-chlorophenyl) terephthalamide; and then, catalytic hydrogenation reaction is carried out to obtain N,N'-bis(4-amino-2-chlorophenyl) terephthalamide. The condensation reaction is carried out in a toluene solvent at a temperature of 90-100 DEG C; and the catalytic hydrogenation reaction is carried out in a tetrahydrofuran or N,N-dimethylformamide or n-butanol solvent at a temperature of 60-70 DEG C. The prepared N,N'-bis(4-amino-2-chlorophenyl) terephthalamide has purity above 99.5%, and can be applied to preparation of a liquid crystal alignment agent. The liquid crystal alignment agent prepared from the N,N'-bis(4-amino-2-chlorophenyl) terephthalamide has a high and stable pre-tilt angle, a high voltage holding ratio, a low residual direct current voltage, a low ion concentration and good rubbing resistance, and can be used in a high-generation TFT liquid crystal production line.

Description

Technical Field

[0001] This invention belongs to the field of liquid crystal alignment agent technology, specifically relating to a method for preparing high-purity N,N'-bis(4-amino-2-chlorophenyl)terephthalamide and its application. Background Technology

[0002] In recent years, liquid crystal display technology has developed rapidly, surpassing any other display technology. With the establishment of high-generation TFT (Thin Film Transistor) liquid crystal production lines, the requirements for various characteristics of liquid crystal alignment films have also increased.

[0003] N,N'-bis(4-amino-2-chlorophenyl)terephthalamide is a chlorinated aromatic diamine monomer. Chinese patent document CN105646267A discloses a method for preparing this aromatic diamine monomer. It uses 2-chloro-4-nitroaniline and terephthaloyl chloride as starting materials. First, in the presence of tetrahydrofuran solvent and pyridine or triethylamine, a condensation reaction is carried out at a temperature of 25-35°C to obtain yellow N,N'-bis(4-nitro-2-chlorophenyl)terephthalamide. Then, in the presence of ethanol solvent and palladium on carbon catalyst, a catalytic hydrogenation reaction is carried out at a temperature of 80-100°C to obtain the crude product. Finally, column chromatography is used to separate the crude product into pale green N,N'-bis(4-amino-2-chlorophenyl)terephthalamide.

[0004] The shortcomings of this method are: (1) Column chromatography is not suitable for large-scale industrial production; (2) Using column chromatography means that the crude product has low purity and impurities are difficult to remove by conventional purification methods. In particular, the product obtained by column chromatography in this literature is light green and the purity is still low (pure product should be white). Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned problems and provide a method for preparing high-purity N,N'-bis(4-amino-2-chlorophenyl)terephthalamide with a purity of over 99.5% suitable for large-scale industrial production, as well as its application.

[0006] The technical solution for achieving the objective of this invention is: a method for preparing high-purity N,N'-bis(4-amino-2-chlorophenyl) terephthalamide, which uses 2-chloro-4-nitroaniline and terephthaloyl chloride as starting materials, first undergoes a condensation reaction to obtain N,N'-bis(4-nitro-2-chlorophenyl) terephthalamide, and then undergoes a catalytic hydrogenation reaction to obtain N,N'-bis(4-amino-2-chlorophenyl) terephthalamide; characterized in that: the condensation reaction is carried out in toluene solvent at a temperature of 90-100°C; the catalytic hydrogenation reaction is carried out in tetrahydrofuran, N,N-dimethylformamide, or n-butanol solvent at a temperature of 60-70°C.

[0007] The molar ratio of 2-chloro-4-nitroaniline to terephthaloyl chloride is 2.2:1 to 1.8:1.

[0008] After the condensation reaction is completed, the process further includes pulping with acetone and N,N-dimethylformamide in sequence.

[0009] The catalyst used in the catalytic hydrogenation reaction is wet platinum carbon with a water content of 50 wt%; the amount of the catalyst is 1% to 5% of the weight of the above-mentioned N,N'-bis(4-nitro-2-chlorophenyl)terephthalamide.

[0010] Following the catalytic hydrogenation reaction, recrystallization is also performed using methanol, ethyl acetate, or toluene.

[0011] The application of the above-mentioned high-purity N,N'-bis(4-amino-2-chlorophenyl) terephthalamide in the preparation of liquid crystal alignment agents is specifically described as follows: N,N'-bis(4-amino-2-chlorophenyl) terephthalamide and dianhydride monomer are polycondensed in an organic solvent to obtain polyamic acid; and a diluent and a leveling agent are added to the polyamic acid to obtain the liquid crystal alignment agent.

[0012] The dianhydride monomer is one or more of the following: pyromellitic dianhydride (PMDA), cyclobutanetetracarboxylic dianhydride (CBDA), 1,3-dimethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride (DMCBDA), 1,2,3,4-butanetetracarboxylic dianhydride (BDA), 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA), and 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthous succinic dianhydride.

[0013] The organic solvent is N-methylpyrrolidone and / or 1,4-butyrolactone.

[0014] The diluent is N-methylpyrrolidone and / or 1,4-butyrolactone.

[0015] The leveling agent is one, two, or three of the following: ethylene glycol butyl ether acetate, propylene glycol methyl ether propionate, and ethylene glycol monobutyl ether.

[0016] The positive effects of this invention are:

[0017] (1) The condensation reaction of the present invention is carried out at high temperature in toluene solvent. On the one hand, there is no need to use acid-binding agent, and on the other hand, compared with the prior art, it can effectively improve the reaction yield and product purity.

[0018] (2) The catalytic hydrogenation reaction of the present invention is carried out in tetrahydrofuran, N,N-dimethylformamide or n-butanol solvent, and wet platinum carbon is used as catalyst. This can effectively suppress the production of dechlorination by-products, thereby effectively improving the purity of the product (above 99.5%).

[0019] (3) The N,N'-bis-(4-amino-2-chlorophenyl)-terephthalamide prepared by this invention has a purity of over 99.5% and can be used in the preparation of liquid crystal alignment agents. The liquid phase alignment agent prepared from it has a high and stable pretilt angle (3). 0 (Above), higher voltage retention rate, lower residual DC voltage, lower ion concentration, and better abrasion resistance, making it suitable for use in high-generation TFT LCD production lines. Attached Figure Description

[0020] Figure 1 The image shows the DSC spectrum of N,N'-bis(4-amino-2-chlorophenyl)terephthalamide prepared in Example 1.

[0021] Figure 2 The image shows the LC-MS spectrum of N,N'-bis(4-amino-2-chlorophenyl)terephthalamide prepared in Example 1. Detailed Implementation

[0022] (Example 1)

[0023] The preparation method of N,N'-bis(4-amino-2-chlorophenyl)terephthalamide in this embodiment includes the following steps:

[0024] ① Add 30g of 2-chloro-4-nitroaniline (0.17mol) and 240mL of toluene to a 500mL three-necked flask, stir to dissolve, heat to 110-120℃ and reflux to remove water for 1h, then cool to 60-70℃ and add 18g of terephthaloyl chloride (0.09mol). After the addition is complete, heat to 90-100℃ to carry out the condensation reaction. Monitor the reaction of terephthaloyl chloride by HPLC until it is complete.

[0025] After the reaction was completed, the mixture was cooled to room temperature and filtered. The filter cake was first pulped with 120 mL of acetone at 50–60 °C and then hot filtered. The filter cake was then pulped with 120 mL of N,N-dimethylformamide at 70–80 °C and then hot filtered to obtain the nitro compound.

[0026] ② The nitro compound obtained in step ① and 1g of wet platinum carbon (containing 50wt% water) were added to the hydrogenation reactor, followed by the addition of 240mL of tetrahydrofuran. After introducing hydrogen gas, the temperature was raised to 60-70℃, and the reaction was monitored by HPLC until it was complete.

[0027] After the reaction was completed, the catalyst was removed by filtration, the filtrate was concentrated under reduced pressure, and methanol was added dropwise at a controlled temperature of 0-10℃ for recrystallization. After filtration and drying, 30.7 g of white solid N,N'-bis(4-amino-2-chlorophenyl)terephthalamide was obtained, with a yield of 83.5%, a melting point of 271.3-273.8℃, and an HPLC purity of 99.5%.

[0028] The ion content of N,N'-bis(4-amino-2-chlorophenyl)terephthalamide prepared in this embodiment is as follows: potassium 1.05 ppm; sodium 0.67 ppm; calcium 1.13 ppm; iron N / A; copper N / A.

[0029] The DCS spectrum of N,N'-bis(4-amino-2-chlorophenyl)terephthalamide prepared in this embodiment is shown in the figure. Figure 1 LC-MS spectra are shown below. Figure 2 .

[0030] (Example 2)

[0031] The preparation method of N,N'-bis(4-amino-2-chlorophenyl)terephthalamide in this embodiment includes the following steps:

[0032] ① Add 20g of 2-chloro-4-nitroaniline (0.12mol) and 160mL of toluene to a 250mL three-necked flask, stir to dissolve, heat to 110-120℃ and reflux to remove water for 1h, then cool to 60-70℃ and add 12g of terephthaloyl chloride (0.06mol). After the addition is complete, heat to 90-100℃ to carry out the condensation reaction. Monitor the reaction of terephthaloyl chloride by HPLC until it is complete.

[0033] After the reaction was completed, the mixture was cooled to room temperature and filtered. The filter cake was first pulped with 80 mL of acetone at 50–60 °C and then hot filtered. The filter cake was then pulped with 80 mL of N,N-dimethylformamide at 70–80 °C and then hot filtered to obtain the nitro compound.

[0034] ② The nitro compound obtained in step ① and 0.67 g of wet platinum carbon (containing 50 wt% water) were added to the hydrogenation reactor, followed by the addition of 160 mL of N,N-dimethylformamide. After introducing hydrogen gas, the temperature was raised to 60-70 °C, and the reaction was monitored by HPLC until it was complete.

[0035] After the reaction was completed, the catalyst was removed by filtration, the filtrate was concentrated under reduced pressure, and ethyl acetate was added dropwise at a controlled temperature of 0-10℃ for recrystallization. After filtration and drying, 21.0 g of white solid N,N'-bis(4-amino-2-chlorophenyl)terephthalamide was obtained, with a yield of 85.5%, a melting point of 271.2-273.5℃, and an HPLC purity of 99.7%.

[0036] The ion content of N,N'-bis(4-amino-2-chlorophenyl)terephthalamide prepared in this embodiment is as follows: potassium 0.98 ppm; sodium 0.51 ppm; calcium 1.11 ppm; iron N / A; copper N / A.

[0037] (Example 3)

[0038] The preparation method of N,N'-bis(4-amino-2-chlorophenyl)terephthalamide in this embodiment includes the following steps:

[0039] ① Add 40g of 2-chloro-4-nitroaniline (0.23mol) and 320mL of toluene to a 500mL three-necked flask, stir to dissolve, heat to 110-120℃ and reflux to remove water for 1h, then cool to 60-70℃ and add 24g of terephthaloyl chloride (0.12mol). After the addition is complete, heat to 90-100℃ to carry out the condensation reaction. Monitor the reaction of terephthaloyl chloride by HPLC until it is complete.

[0040] After the reaction was completed, the mixture was cooled to room temperature and filtered. The filter cake was first pulped with 160 mL of acetone at 50–60 °C and then hot filtered. The filter cake was then pulped with 160 mL of N,N-dimethylformamide at 70–80 °C and then hot filtered to obtain the nitro compound.

[0041] ② The nitro compound obtained in step ① and 1.34 g of wet platinum carbon (containing 50 wt% water) were added to the hydrogenation reactor, followed by the addition of 320 mL of n-butanol. After purging with hydrogen gas, the temperature was raised to 60–70 °C, and the reaction was monitored by HPLC until complete.

[0042] After the reaction was completed, the catalyst was removed by filtration, the filtrate was concentrated under reduced pressure, and toluene was added dropwise at a controlled temperature of 0-10℃ for recrystallization. After filtration and drying, 42.4 g of white solid N,N'-bis(4-amino-2-chlorophenyl)terephthalamide was obtained, with a yield of 86.4%, a melting point of 271.3-273.7℃, and an HPLC purity of 99.6%.

[0043] The ion content of N,N'-bis(4-amino-2-chlorophenyl)terephthalamide prepared in this embodiment is as follows: potassium 0.68 ppm; sodium 0.47 ppm; calcium 1.04 ppm; iron N / A; copper N / A.

[0044] (Application Example 1)

[0045] This application example demonstrates the preparation of a liquid crystal alignment agent using N,N'-bis(4-amino-2-chlorophenyl)terephthalamide obtained in Example 1. The specific method is as follows:

[0046] In a 2000 mL three-necked round-bottom flask equipped with a mechanical stirrer, thermometer, and nitrogen protection device, 41.52 g of N,N'-bis(4-amino-2-chlorophenyl)terephthalamide (0.1 mol) was dissolved in 351 g of N-methylpyrrolidone. After stirring evenly, 9.81 g of cyclobutanetetracarboxylic dianhydride (0.05 mol) and 10.58 g of pyromellitic dianhydride (0.0485 mol) were added in batches. The mixture was stirred at room temperature (15–25 °C) for 4 h. Then, 208 g of ethylene glycol monobutyl ether was added to the reaction solution, and then 412 g of N-methylpyrrolidone was used to dilute the solution to a solid content of 6 wt%. Finally, the solution was filtered through a 0.1 μm fine filter to obtain a liquid crystal photoaligning agent solution with a viscosity of 48 cp (25 °C).

[0047] The liquid crystal alignment agent solution prepared above was spin-coated onto an ITO glass substrate at a speed of 3500 rpm using a spin coater. Then, it was baked at 100°C for 2 min and cured at 230°C for 30 min to obtain a polyimide liquid crystal alignment film with a thickness of 1000 angstroms. Its hardness was tested to be 4H.

[0048] After rubbing the polyimide liquid crystal alignment film with a lint-free cloth, it was assembled and injected with liquid crystal (FC-02, Merck) to obtain a liquid crystal test box.

[0049] Testing revealed that its orientation was uniform and defect-free, with a liquid crystal pretilt angle of 3.2°. 0 The pretilt angle after heating at 120℃ for 1 hour is 3.2. 0 No changes were found due to heat treatment.

[0050] The voltage retention rate was tested to be 98.5% at 23℃ and 90.1% at 90℃, demonstrating excellent voltage retention.

[0051] A 30Hz / ±3V rectangular wave with a 3V DC current was superimposed on the liquid crystal cell at 23℃. After 60 minutes, the 3V DC power supply was cut off, and the residual voltage inside the liquid crystal cell was measured to be 0.5V, which has a low residual DC voltage.

[0052] The ion concentration inside the liquid crystal cell was measured to be 0.15 PF at 25℃ and 28.69 PF at 60℃.

[0053] (Application Examples 2 to 3)

[0054] The application examples are basically the same as application example 1, except for the types of dianhydride monomers, as shown in Table 1.

[0055] The relevant properties of the liquid crystal alignment agents obtained from each application example are tested, and the results are still shown in Table 1.

[0056] (Compare Application Examples 1 to 2)

[0057] The comparative application examples are basically the same as application example 1, except for the types of diamine monomers and dianhydride monomers, as detailed in Table 1.

[0058] The relevant properties of the liquid crystal alignment agents obtained from each comparative application example were tested, and the results are still shown in Table 1.

[0059] In Table 1, the target product is N,N'-bis(4-amino-2-chlorophenyl)terephthalamide, 4,4'-ODA represents 4,4'-diaminodiphenyl ether, CBDA represents cyclobutanetetracarboxylic dianhydride, PMDA represents pyromellitic dianhydride, and DMCBDA represents 1,3-dimethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride.

[0060] Table 1

[0061] Application Example 1 Application Example 2 Application Example 3 Comparative Application Example 1 Comparative Application Example 2 diamine monomer Target product [0.1 mol] Target product [0.1 mol] Target product [0.1 mol] 4,4'-ODA [0.1 mol] Target product [0.05 mol] + 4,4'-ODA [0.05 mol] Dihydride monomer CBDA【0.05mol】+ PMDA【0.0485mol】 CBDA [0.0985 mol] DMCBDA [0.0995 mol] CBDA [0.0985 mol] CBDA [0.0985 mol] Pretilt angle <![CDATA[3.2 0 ]]> <![CDATA[3.0 0 ]]> <![CDATA[3.1 0 ]]> <![CDATA[2.1 0 ]]> <![CDATA[2.6 0 ]]> Pretilt angle after heating at 120℃ for 1 hour <![CDATA[3.2 0 ]]> <![CDATA[3.0 0 ]]> <![CDATA[3.1 0 ]]> <![CDATA[1.9 0 ]]> <![CDATA[2.6 0 ]]> Voltage holding rate (23℃) 98.5% 99.1% 99.3% 96.8% 98.2% Voltage holding rate (90°C) 90.1% 95.2% 96.8% 86.4% 90.1% Residual DC voltage 0.5V 0.6V 0.6V 1.9V 0.6V Ion concentration (25℃) 0.15PF 0.44PF 0.65PF 500PF 0.99PF Ion concentration (60℃) 28.69PF 56.86PF 62.33PF 1900PF 58.99PF

Claims

1. A method for preparing high-purity N,N'-bis(4-amino-2-chlorophenyl)terephthalamide, which is prepared by using 2-chloro-4-nitroaniline and terephthaloyl chloride as starting materials, first obtaining N,N'-bis(4-nitro-2-chlorophenyl)terephthalamide through condensation reaction, and then obtaining N,N'-bis(4-amino-2-chlorophenyl)terephthalamide through catalytic hydrogenation reaction; characterized in that: The condensation reaction is carried out in toluene solvent at a temperature of 90-100 DEG C; the catalytic hydrogenation reaction is carried out in tetrahydrofuran or N,N-dimethylformamide or n-butanol solvent at a temperature of 60-70 DEG C; the catalyst used in the catalytic hydrogenation reaction is wet platinum carbon with a water content of 50 wt%; the amount of the catalyst is 1-5% of the weight of the N,N'-bis(4-nitro-2-chlorophenyl)terephthalamide. ​ 2. The process for the preparation of high purity N,N'-bis(4-amino-2-chlorophenyl)terephthalamide according to claim 1, characterized in that: The molar ratio of the 2-chloro-4-nitroaniline to terephthaloyl chloride is 2.2:1-1.8:

1.

3. The process for the preparation of high purity N,N'-bis(4-amino-2- chlorophenyl)terephthalamide according to claim 1, characterized by: After the condensation reaction, beating-up is further carried out using acetone and N,N-dimethylformamide in sequence.

4. The process for the preparation of high purity N,N'-bis(4-amino-2-chlorophenyl)terephthalamide according to claim 1, characterized by: After the catalytic hydrogenation reaction, recrystallization is further carried out using methanol or ethyl acetate or toluene. The condensation reaction is carried out in toluene solvent at a temperature of 90-100 DEG C; the catalytic hydrogenation reaction is carried out in tetrahydrofuran or N,N-dimethylformamide or n-butanol solvent at a temperature of 60-70 DEG C; the catalyst used in the catalytic hydrogenation reaction is wet platinum carbon with a water content of 50 wt%; the amount of the catalyst is 1-5% of the weight of the N,N'-bis(4-nitro-2-chlorophenyl)terephthalamide. The molar ratio of the 2-chloro-4-nitroaniline to terephthaloyl chloride is 2.2:1-1.8:

1. After the condensation reaction, beating-up is further carried out using acetone and N,N-dimethylformamide in sequence. After the catalytic hydrogenation reaction, recrystallization is further carried out using methanol or ethyl acetate or toluene.

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