A method for improving the purity of a heat-sensitive dye odb-2

Abstract

The application belongs to the technical field of fine chemical industry, and particularly relates to a method for improving the purity of a heat-sensitive dye ODB-2. The segmented controlled nitrogen pressurization ODB-2 crystallization technology provided by the application realizes efficient improvement of the purity of ODB-2 products through five steps of feeding, temperature rising, pressurization, crystal precipitation and crystal growth, can efficiently remove impurities generated in the crude ODB-2 due to sulfonation, ring-opening reaction and the like, overcomes technical bottlenecks such as difficult separation of complex impurities, low purity, and a large amount of organic solvent stirring and washing in the existing ODB-2 preparation process, and the purity of the obtained ODB-2 product reaches 99.8%. The method is simple to operate, reduces production cost, provides a new way for industrialized preparation of high-purity heat-sensitive dye ODB-2, and has remarkable economic benefits.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fine chemical industry, and particularly relates to a method for improving the purity of a heat-sensitive dye ODB-2. BACKGROUND

[0002] 2-phenylamino-3-methyl-6-dibutylaminofluoran (ODB-2) is an important heat-sensitive dye, which is widely used in the field of heat-sensitive recording materials, especially in the production of heat-sensitive paper. It has the advantages of high sensitivity, good color intensity, excellent thermal stability, strong light resistance and heat resistance, high environmental protection and safety, good solubility and processability, etc. In the application aspect, the heat-sensitive dye ODB-2 is mainly used in the fields of commercial bill printing, electronic scale label, automatic vending machine receipt, medical record paper, etc.

[0003] At present, the industrial synthesis method of ODB-2 dye is to obtain the target product through three steps of condensation catalyzed by concentrated sulfuric acid, water washing and solidification, and base catalysis ring closure. The synthesis process faces the problems of multiple reaction sites and multiple side reactions, and is often accompanied by multiple side reactions such as sulfonation, ring opening, decomposition and multi-site condensation, which shows the problems of poor product quality caused by many impurities, high color grade and poor thermal stability. Therefore, it is extremely important to improve the purity of the heat-sensitive dye ODB-2.

[0004] .

[0005] The existing ODB-2 crude product purification mainly adopts a large amount of organic solvent stirring washing or elution method (EP2289896, CN1854201A, CN101190920A, WO2000012513, CN108191883A, CN101323619A, CN105838105A), so that the solvent consumption of the product purification process is large, and the production efficiency is low. At the same time, the purification effect of this kind of method for the complex and difficult-to-handle impurities generated in the synthesis process of ODB-2 and the compounds with similar properties (such as solubility) to the main product is poor, and it is difficult to obtain high-purity ODB-2 product, and the product has weak competitive advantage. Therefore, how to efficiently improve the purity of ODB-2 product is the technical challenge faced by the current synthesis of heat-sensitive dye ODB-2. SUMMARY

[0006] In order to solve the problems of the prior art, the application provides a method for improving the purity of a heat-sensitive dye ODB-2.

[0007] In order to achieve the above purpose, the application adopts the following technical scheme:

[0008] A method for improving the purity of a heat-sensitive dye ODB-2, comprising the following steps:

[0009] (1) Feeding: Put ODB-2 crude and solvent into the high-pressure reactor, and replace the vacuum with nitrogen, wherein the solvent is one of methanol, ethanol and isopropanol;

[0010] (2) Heating: Start stirring and heat the system to 70-100°C;

[0011] (3) Pressurization: Open the nitrogen pressurization pipeline, increase the pressure in the reactor to 0.8-10.2 MPa, and stir for 1-2 hours;

[0012] (4) Crystal precipitation: Control the cooling rate to be 0.1°C / min-1°C / min, and after the system is cooled to 40-45°C, release the pressure to normal pressure, and stir for 2 hours at constant temperature;

[0013] (5) Crystal growth: Open the nitrogen pressurization pipeline again, increase the pressure in the reactor to 0.8-10.2 MPa, and under stirring, control the cooling rate to be 0.1°C / min-0.5°C / min, and cool the reactor to 5-10°C, and after stirring for 1 hour at the final temperature, release the pressure in the reactor to normal pressure, and filter and dry to obtain ODB-2 pure product.

[0014] Preferably, the mass of the solvent in step (1) is 1-2 times the mass of the ODB-2 crude. The nitrogen replacement in step (1) is at least three times.

[0015] Preferably, the heating rate in step (2) is 1°C / min-5°C / min.

[0016] Preferably, the pressure in step (3) is 0.8-10.2 MPa; and the stirring rate is 150-250 rpm.

[0017] Preferably, in step (4), the stirring rate is 60-120 rpm.

[0018] Preferably, in step (5), stirring is continued during the cooling process, and the stirring rate is controlled to be 100-150 rpm.

[0019] The present application has the following advantages:

[0020] One or more technical solutions provided by the present application have the following advantages compared with the prior art:

[0021] The application develops a segmented controlled nitrogen pressurization ODB-2 crystallization technology, and realizes efficient improvement of the purity of ODB-2 products through five steps of feeding, temperature rising, pressurization, crystal precipitation and crystal growth, can efficiently remove impurities in the ODB-2 crude product caused by sulfonation, ring-opening reaction and the like, overcomes the technical bottlenecks of the existing ODB-2 preparation process, such as difficult separation of complex impurities, low purity, large amount of organic solvent stirring and washing and the like, and the obtained ODB-2 product has a purity of 99.8%. The method is simple in operation, reduces the production cost, provides a new way for industrialized preparation of high-purity heat-sensitive dye ODB-2, and has remarkable economic benefits.

[0022] The method of the application is suitable for purification of ODB-2 crude products with a purity of 90% or more, and can be used for treating ODB-2 crude products synthesized by various methods. When the crude product is prepared, a synthesis method with lower cost and easier operation can be selected, and the simple purification method of the application is combined to realize production of high-purity ODB-2. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The HPLC spectrum of the heat-sensitive dye ODB-2 pure product purified by the method of the application in Example 4. DETAILED DESCRIPTION

[0024] The application provides the following specific examples to further describe the technical solutions of the application, but the protection scope of the application is not limited to these examples. Any changes or equivalent replacements without departing from the concept of the application are included in the protection scope of the application.

[0025] The crude product of the ODB-2 dye used in the method examples is prepared by a traditional method, and the process is as follows:

[0026] Cool 100% concentrated sulfuric acid (650 g) to 4°C, add 4-dibutyl ketone acid (173.7 g) in batches within 1 h and stir until it is fully dissolved. Then, add 2-methyl-4-methoxy diphenylamine (100 g) in batches within 5 h while controlling the temperature at 4°C, and after the addition, react at room temperature for 11 h. After the reaction is completed, drop the obtained reaction solution into 2800 mL of deionized water within 3 h while controlling the temperature at 15°C, stir for 0.5 h after the dropping is completed, and then filter, and the filter cake is washed twice with 100 g of deionized water (2 min each time). Then, the obtained filter cake is added into 1000 mL of toluene, and after being fully dispersed by stirring, the pH of the system is adjusted to 8 with a 5% sodium hydroxide solution, and the system is slowly heated to 90°C. After the system is clarified, it is allowed to stand and separate into layers. At 90°C, 10% sodium hydroxide solution is added to the toluene phase to make the pH of the system 13, and then the system is gradually heated to reflux. After 2 h of reaction, the system is allowed to stand and separate into layers. The toluene phase is washed with 85°C deionized water (250 mL), and the lower aqueous phase is separated again. The toluene is recovered by distillation under reduced pressure, and then 200 mL of hot water is added to distill the toluene. After the system is cooled to 25°C, it is filtered, and then 300 mL of water is used to wash twice to obtain the crude ODB-2 (purity 96%).

[0027] Example 1:

[0028] A method for improving the purity of the heat-sensitive dye ODB-2, comprising the following steps:

[0029] (a) Feeding: At room temperature, ODB-2 crude product (1000 g) and ethanol (1000 g) are added to a high-pressure reaction kettle, and the system is vacuumed and replaced with nitrogen three times.

[0030] (b) Heating: The stirring is started, and the system is heated to 100°C at a heating rate of 5°C / min.

[0031] (c) Pressurization: The nitrogen pressurization pipeline is opened, and the pressure in the reaction kettle is increased to 7±0.2 MPa while stirring at a speed of 150 r / min for 1 h.

[0032] (d) Crystal precipitation: After the system is cooled to 40-45°C at a cooling rate of 1°C / min, the pressure is released to normal pressure, and the system is stirred at a constant temperature of 60 r / min for 2 h.

[0033] (e) Crystal growth: The nitrogen pressurization pipeline is opened again, and the pressure in the reaction kettle is slowly increased to 7±0.2 MPa. The stirring speed (100 r / min) and the cooling rate (0.1°C / min) are controlled to slowly reduce the temperature of the reaction kettle to 5-10°C. After 1 h of stirring at the final temperature, the reaction kettle is released to normal pressure, and then filtered and dried to obtain the ODB-2 product (white solid 965 g, yield 96.5%, purity 99.811%).

[0034] Example 2:

[0035] A method for improving the purity of heat-sensitive dye ODB-2, comprising the following steps:

[0036] (a) Feeding: At room temperature, add ODB-2 crude product (1000 g) and methanol (1000 g) into a high-pressure reaction kettle, vacuumize and replace with nitrogen three times.

[0037] (b) Heating: Start stirring, control the heating rate at 3.5°C / min to raise the system to 70°C.

[0038] (c) Pressurization: Open the nitrogen pressurization pipeline, raise the pressure in the reaction kettle to 10±0.2 MPa and stir at 250 rpm for 1.5 h.

[0039] (d) Crystal precipitation: Control the cooling rate at 1°C / min to lower the system to 40-45°C, then depressurize to normal pressure, and stir at 120 rpm for 2 h at constant temperature.

[0040] (e) Crystal growth: Reopen the nitrogen pressurization pipeline, slowly raise the pressure in the reaction kettle to 10±0.2 MPa, control the stirring speed (150 rpm) and the cooling rate (0.5°C / min) to slowly lower the temperature of the reaction kettle to 5-10°C. After stirring for 1 h at this final temperature, the reaction kettle is depressurized to normal pressure, filtered and dried to obtain ODB-2 product (white solid 965 g, yield 97%, purity 99.809%).

[0041] Example 3:

[0042] A method for improving the purity of heat-sensitive dye ODB-2, comprising the following steps:

[0043] (a) Feeding: At room temperature, add ODB-2 crude product (1000 g) and isopropanol (1500 g) into a high-pressure reaction kettle, vacuumize and replace with nitrogen three times.

[0044] (b) Heating: Start stirring, control the heating rate at 2.2°C / min to raise the system to 90°C.

[0045] (c) Pressurization: Open the nitrogen pressurization pipeline, raise the pressure in the reaction kettle to 1±0.2 MPa and stir at 180 rpm for 2 h.

[0046] (d) Crystal precipitation: Control the cooling rate at 0.4°C / min to lower the system to 40-45°C, then depressurize to normal pressure, and stir at 100 rpm for 2 h at constant temperature.

[0047] (e) Crystal growth: nitrogen pressure line was opened again, and the pressure in the reactor was slowly increased to 1 ± 0.2 MPa. The stirring speed (120 rpm) and the cooling rate (0.25 °C / min) were controlled to slowly decrease the temperature of the reactor to 5-10 °C. After stirring for 1 h at this final temperature, the reactor was vented to atmospheric pressure, and the product ODB-2 (white solid 968 g, yield 96.8%, purity 99.817%) was obtained by filtration and drying.

[0048] Example 4:

[0049] A method for improving the purity of heat-sensitive dye ODB-2, comprising the following steps:

[0050] (a) Feeding: at room temperature, ODB-2 crude product (1000 g) and ethanol (2000 g) were added to a high-pressure reactor, vacuumed and replaced with nitrogen three times.

[0051] (b) Heating: stirring was started, and the system was heated to 85 °C at a rate of 1 °C / min.

[0052] (c) Pressurization: nitrogen pressure line was opened, and the pressure in the reactor was increased to 4 ± 0.2 MPa and stirred at 210 rpm for 2 h.

[0053] (d) Crystal precipitation: after controlling the cooling rate to 0.1 °C / min to decrease the system temperature to 40-45 °C, the pressure was released to atmospheric pressure, and the temperature was kept constant at 65 rpm for 2 h.

[0054] (e) Crystal growth: nitrogen pressure line was opened again, and the pressure in the reactor was slowly increased to 4 ± 0.2 MPa. The stirring speed (50 rpm) and the cooling rate (0.35 °C / min) were controlled to slowly decrease the temperature of the reactor to 5-10 °C. After stirring for 1 h at this final temperature, the reactor was vented to atmospheric pressure, and the product ODB-2 (white solid 968 g, yield 97.2%, purity 99.824%) was obtained by filtration and drying.

[0055] The HPLC spectrum of the purified heat-sensitive dye ODB-2 is shown in Figure 1 The retention time of 7.451 min in the figure is the heat-sensitive dye ODB-2.

[0056] Comparative Example 1

[0057] A method for improving the purity of heat-sensitive dye ODB-2, compared with Example 4, step (3) was not purged with nitrogen, and the pressure in the reactor was 0.131 MPa after heating to 85 °C. The yield of ODB-2 pure product was 97.5%, and the purity was 96.81%.

[0058] Comparative Example 2

[0059] A method for improving the purity of heat-sensitive dye ODB-2, the pressure of step (3) is 0.7 MPa compared with Example 4. The yield of ODB-2 pure product is 97.1%, and the purity is 97.46%.

Claims

1. A method for improving the purity of the thermosensitive dye ODB-2, characterized in that, Includes the following steps: (1) Feeding: Add crude ODB-2 and solvent to the high-pressure reactor, evacuate and replace with nitrogen. The solvent is one of methanol, ethanol and isopropanol. (2) Heating: Turn on the stirring and raise the temperature of the system to 70-100°C; (3) Pressurization: Turn on the nitrogen pressurization pipeline to raise the pressure in the reactor to 0.8-10.2 MPa and stir for 1-2 hours; (4) Crystal precipitation: Control the cooling rate to 0.1°C / min-1°C / min, and after the system is cooled to 40-45°C, release the pressure to atmospheric pressure and stir at a constant temperature for 2 hours; (5) Crystal growth: Reopen the nitrogen pressurization pipeline and raise the pressure in the reactor to 0.8-10.2 MPa. Under stirring, control the cooling rate to 0.1°C / min-0.5°C / min and lower the reactor temperature to 5-10°C. Stir at this final temperature for 1 hour and then release the reactor to atmospheric pressure. Filter and dry to obtain pure ODB-2.

2. The method for improving the purity of the thermosensitive dye ODB-2 according to claim 1, characterized in that, The mass of the solvent in step (1) is 1-2 times the mass of the crude ODB-2.

3. The method for improving the purity of the thermosensitive dye ODB-2 according to claim 1, characterized in that, In step (2), the heating rate is 1°C / min-5°C / min.

4. The method for improving the purity of the thermosensitive dye ODB-2 according to claim 1, characterized in that, The pressure in step (3) is 2.8-5.2 MPa; the stirring rate is 150-250 rpm.

5. The method for improving the purity of the thermosensitive dye ODB-2 according to claim 1, characterized in that, In step (4), the stirring rate is 60-120 rpm.

6. The method for improving the purity of the thermosensitive dye ODB-2 according to claim 1, characterized in that, In step (5), the stirring rate is 100-150 rpm.

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