Efficient post-treatment method for obtaining high-purity antioxidant 168

Abstract

The invention belongs to the technical field of fine chemical product purification, and particularly relates to a post-treatment method of an antioxidant 168 crude product, which comprises the following steps: S1, cooling the antioxidant 168 crude product under the action of inert gas atmosphere and stirring to separate out white crystal particles; s2, adding methanol, stirring, washing, carrying out suction filtration, and repeatedly washing a filter cake for 1-2 times; and S3, carrying out vacuum drying to obtain the white powdery high-purity antioxidant 168. According to the method provided by the invention, the high-purity antioxidant 168 product can be obtained; meanwhile, the method provided by the invention is high in universality, and is suitable for treating the crude antioxidant 168 in a solvent synthesis method and a solvent-free synthesis method; besides, according to the method provided by the invention, the crystallization characteristic of the antioxidant 168 is utilized, white crystal particles are separated out by cooling, and agglomerated blocks do not exist, so that impurity coating is greatly reduced, the washing efficiency is improved, recrystallization operation is not needed, the use amount of a washing solvent is reduced, the solvent can be directly recycled for multiple times, the cost is reduced, and the method is suitable for industrial production. And the method has a relatively great application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of purification of fine chemical products, and in particular relates to an efficient post-processing method for obtaining high-purity antioxidant 168. Background Art

[0002] Antioxidant 168, chemical name tris (2,4-di-tert-butylphenyl) phosphite, is a phosphite auxiliary antioxidant with excellent performance. It has very low volatility and toxicity, high thermal stability, good hydrolysis stability, and can effectively decompose the hydroperoxides produced in the processing of polymer materials, thereby playing an antioxidant role. It is often used in combination with hindered phenol main antioxidants to give full play to the synergistic effect. It is widely used in polymer materials such as polyolefins, styrene monomers and copolymers, elastomers, adhesives, rubbers and engineering plastics.

[0003] At present, the method for synthesizing antioxidant 168 mainly uses phosphorus trichloride and 2,4-di-tert-butylphenol as raw materials, xylene, toluene, 2,4-di-tert-butylphenol, etc. as solvents, triethylamine, DMAP, etc. as catalysts, and generates the target product antioxidant 168 at a certain temperature and pressure. At the same time, the post-treatment method of the crude product of antioxidant 168 mainly includes ① anti-solvent crystallization method: in this method, after the reaction is completed, the reaction solvent is not evaporated, and after cooling, a poor solvent with poor solubility of antioxidant 168 is added to crystallize and precipitate antioxidant 168. This method consumes a large amount of solvent, takes a long time, and if the solvent is to be recycled, it is necessary to distill and separate the solvent. CN117801011A adds 3.0 times the volume of methanol by mass of antioxidant 168 to a toluene solution in which antioxidant 168 is dissolved to precipitate antioxidant 168. CN112661787B adds 4.3 times the volume of methanol of the antioxidant 168 to the xylene solution in which the antioxidant 168 is dissolved, then cools down for crystallization, filters, washes with methanol, and dries. ② Recrystallization method: After the reaction is completed, the reaction solvent is first removed by vacuum distillation to obtain a solid material, then isopropanol, ethyl acetate, etc. are added to the solid material and heated and stirred, and finally cooled down for crystallization, filtered, and dried. CN117327115A adds 5.0 times the volume of a mixed solvent to the solid material obtained by removing the reaction solvent. CN117384208A, CN116969990B, CN117659078A, CN110590834B, CN109897062A, CN104370956A, etc. also use this method. In this method, during the process of removing the reaction solvent by vacuum distillation to obtain a solid material, agglomerates are present due to the excessively fast crystallization rate. Therefore, this method usually needs to be purified by recrystallization. For example, in CN109897062A, the crude product of antioxidant 168 is dissolved in a mixed solvent (v / v) of ethyl acetate and methanol in a ratio of 5:1 with a volume of 10 times its weight (w / v), heated to reflux temperature for 20 minutes, cooled to room temperature, crystals precipitated, filtered, and the crystals obtained were repeated to obtain a second recrystallization product, which was dried to obtain a pure product of antioxidant 168.

[0004] In summary, the current post-processing technology of antioxidant 168 has the problems of large amount of solvent, many types of solvents, difficult solvent recycling, complicated processing process and high cost. It is of great significance to find an efficient and convenient post-processing technology of antioxidant 168 that consumes less solvent and does not require recrystallization. Summary of the invention

[0005] In order to solve the above problems, the present invention provides an efficient post-treatment method for obtaining high-purity antioxidant 168, the scheme is as follows: An efficient post-treatment method for obtaining high-purity antioxidant 168 comprises the following steps: S1: The crude product of antioxidant 168 is cooled and precipitated into white crystalline particles under an inert gas atmosphere and stirring, thereby obtaining a granular crude product of antioxidant 168; S2: Add methanol, stir and wash, and filter; S3: vacuum drying to obtain white powdery high-purity antioxidant 168.

[0006] The post-treatment method is applicable to a system in which the antioxidant 168 is synthesized by a solvent method and a system in which the antioxidant 168 is synthesized by a solvent-free method.

[0007] For the system of synthesizing antioxidant 168 by solvent method, S1 is specifically as follows: when the crude product of liquid antioxidant 168 is subjected to reduced pressure distillation to remove the solvent until it becomes viscous, an inert gas at a flow rate of 20-40 mL / min is introduced, and the inert gas atmosphere is maintained while stirring to precipitate white crystalline particles of the viscous crude product of antioxidant 168, and then the solvent is further removed by reduced pressure distillation until no solvent is evaporated to obtain a granular crude product of antioxidant 168.

[0008] For the system of solvent-free synthesis of antioxidant 168, S1 is specifically as follows: an inert gas at a flow rate of 80-100 mL / min is immediately introduced into the liquid crude antioxidant 168 obtained after the reaction is completed. When the crude antioxidant 168 turns slightly white, the inert gas flow rate is reduced to 20-40 mL / min. Under the inert gas atmosphere and stirring, the crude antioxidant 168 becomes viscous and white crystalline particles are gradually precipitated to obtain granular crude antioxidant 168.

[0009] S2 specifically comprises: adding methanol to the crude granular antioxidant 168 product according to a mass ratio of 1:0.15-1.6 between the crude granular antioxidant 168 product and methanol, stirring and washing at 20-80°C for 5-30 min, filtering with suction, and repeatedly washing the filter cake 1-2 times; preferably, the mass ratio of the crude granular antioxidant 168 product to methanol is 1:0.8, stirring and washing at 30°C for 10 min, filtering with suction, and repeatedly washing the filter cake once.

[0010] S3 is specifically: vacuum drying for 3 to 12 hours at 10 to 100 mbar and 30 to 60°C to obtain a white powdery high-purity antioxidant 168; preferably, vacuum drying for 4 to 6 hours at 10 to 20 mbar and 50°C to obtain a white powdery high-purity antioxidant 168.

[0011] The inert gas is at least one of nitrogen, helium or argon.

[0012] The reduced pressure distillation conditions are: system temperature 120-125°C, pressure 200-600 mbar.

[0013] Compared with the existing antioxidant 168 post-treatment method, the present invention has the following advantages: (1) The method provided by the present invention has strong universality and is suitable for treating crude antioxidant 168 produced by solvent synthesis method and solvent-free synthesis method.

[0014] (2) The present invention utilizes the crystallization characteristic that the solubility of antioxidant 168 decreases significantly with decreasing temperature. The viscous crude antioxidant 168 is cooled under an inert gas atmosphere and stirring to precipitate white crystalline particles without the presence of agglomerates. This greatly reduces impurity coating, improves washing efficiency, shortens washing time, eliminates the need for recrystallization operations, reduces the amount of washing solvent used, and the solvent can be directly recycled for multiple times, thereby reducing costs and having great application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 White crystalline particles precipitated from the crude viscous antioxidant 168 of Example 1; FIG2 HPLC chromatogram of antioxidant 168 obtained in Example 1; FIG3 HPLC chromatogram of antioxidant 168 obtained in Example 2; FIG4 is a high performance liquid chromatogram of the antioxidant 168 prepared in Comparative Example 1; Figure 5 HPLC chromatogram of methanol recovered after post-treatment in Comparative Example 1; FIG6 is a high performance liquid chromatogram of the antioxidant 168 prepared in Comparative Example 2; Figure 7 Solid material obtained by directly and completely removing xylene from Comparative Example 2; Figure 8 High performance liquid chromatogram of antioxidant 168 prepared in Comparative Example 3. DETAILED DESCRIPTION

[0016] The embodiments of the present invention will be described in detail below with reference to examples. The following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0017] Example 1 This embodiment provides an efficient post-treatment method for obtaining a high-purity antioxidant 168 (post-treatment of a solvent-free synthesis antioxidant 168), comprising the following steps: Synthesis of antioxidant 168: Phosphorus trichloride (200.0 g) and 2,4-di-tert-butylphenol (886.4 g) were used as raw materials and triethylamine (6.25 g) was used as a catalyst. The 2,4-di-tert-butylphenol was melted into a liquid by heating at 60-90 °C. The catalyst and phosphorus trichloride were added at 55-65 °C and the first stage of heat preservation was carried out. When the solution became slightly turbid, the temperature was raised to 70-80 °C to clarify the reaction system and the second stage of heat preservation was carried out. When the solution became slightly turbid, the temperature was raised to 120-130 °C to clarify the reaction system and the third stage of heat preservation was carried out. When the solution became slightly viscous, the temperature was raised to 185-195 °C to clarify the reaction system and the fourth stage of heat preservation was carried out. The reaction was stopped after the hydrogen chloride was no longer discharged to synthesize antioxidant 168.

[0018] Post-treatment: After the reaction, the oil temperature was 190 °C, the internal temperature was 160 °C, and the product was a light yellow liquid. Remove the heating, introduce nitrogen at 100 mL / min to cool the reaction system. When the temperature dropped to the point where the product turned slightly white, reduce the nitrogen flow rate to 20 mL / min and maintain the nitrogen atmosphere. At the same time, stir rapidly (speed 20-30 r / s). The product gradually became viscous and precipitated as a white crystalline granular antioxidant 168 crude product (such as Figure 1 as shown).

[0019] Add 1 L of methanol, stir and wash at 30 °C for 10 min, and filter. Wash the filter cake again by adding 1 L of methanol, stirring and washing at 30 °C for 30 min, and filter. Vacuum dry for 5 h at 20 mbar and 50 °C. Obtain 895.15 g of white powder product with a yield of 96.61%. Take samples and test the product quality indicators according to HG / T 3712-2010 "Antioxidant 168". Figure 2 As shown, 2.2 min: solvent peak caused by the difference between the sample dissolving solvent and the mobile phase, which is not an impurity and is not included in the content calculation; 2.5 min: 2,4-di-tert-butylphenol; 14.5 min: antioxidant 168; the main content of antioxidant 168 in the product is 99.86%, the phenol content is 0.14%, the acid value is 0.08 mg KOH / g, and the melting point is 184.1~184.8 ℃.

[0020] Since the synthesis method adopted in this embodiment does not use solvents, and the washing solvent is a single type of solvent, the methanol filtrate of the second washing in the post-treatment method adopted in this embodiment can be directly used as the first methanol washing liquid of the next batch. The methanol washing liquid after multiple washings can be recycled as a new washing liquid through a simple distillation, and the distillation pot residue can be used as a raw material to participate in the reaction.

[0021] Example 2 This embodiment provides an efficient post-treatment method for obtaining a high-purity antioxidant 168 (post-treatment of the antioxidant 168 synthesized by a solvent method, first removing the reaction solvent to a viscous state and rapidly stirring), comprising the following steps: Synthesis of antioxidant 168: Antioxidant 168 was synthesized using phosphorus trichloride (200.0 g) and 2,4-di-tert-butylphenol (886.4 g) as raw materials, xylene (500 g) as solvent, triethylamine (6.25 g) as catalyst, at 120-160 °C and 600-990 mbar.

[0022] Post-treatment: After the reaction, the oil temperature was 140 °C, the reaction liquid was 120-125 °C, and the pressure was 200-600 mbar. The solvent was removed until the synthesis system became viscous. Nitrogen was introduced and the nitrogen atmosphere was maintained (20-40 mL / min) while stirring rapidly (20-30 r / s) to gradually precipitate the viscous crude antioxidant 168 as white crystalline particles. Subsequently, the solvent was removed by vacuum distillation until no solvent was distilled out, and about 895 g of crude antioxidant 168 in the form of white granules was obtained.

[0023] Add 1 L of methanol, stir and wash at 30 °C for 10 min, and filter. Wash the filter cake again by adding 1 L of methanol, stirring and washing at 30 °C for 30 min, and filter. Vacuum dry for 5 h at 20 mbar and 50 °C. Obtain 899.22 g of white powder product with a yield of 97.05%. Take samples and test the product quality indicators according to HG / T 3712-2010 "Antioxidant 168". Figure 3 As shown, 2.1 min: solvent peak caused by the difference between the sample dissolving solvent and the mobile phase, which is not an impurity and is not included in the content calculation; 2.4 min: 2,4-di-tert-butylphenol; 14.3 min: antioxidant 168; the main content of antioxidant 168 in the product is 99.80%, the phenol content is 0.20%, the acid value is 0.12 mg KOH / g, and the melting point is 183.3~184.1 ℃.

[0024] The methanol filtrate from the second washing of the post-treatment method adopted in this embodiment can be directly used as the first methanol washing liquid for the next batch. The methanol washing liquid after multiple washings can be recycled as a new washing liquid through a simple distillation, and the distillation pot residue can be used as a raw material to participate in the reaction.

[0025] Comparative Example 1 This comparative example is compared with Example 2. This comparative example provides a post-treatment method of antioxidant 168 (post-treatment of antioxidant 168 synthesized by solvent method, without removing the reaction solvent, using anti-solvent crystallization method), comprising the following steps: Synthesis of antioxidant 168: Using phosphorus trichloride (200.0 g) and 2,4-di-tert-butylphenol (886.4 g) as raw materials, xylene (500 mL) as solvent, and triethylamine (6.25 g) as catalyst, antioxidant 168 was synthesized. The raw material feeding amount and reaction conditions of this comparative example are exactly the same as those of Example 2.

[0026] Post-treatment: After the reaction is completed, cool to room temperature, a small amount of product precipitates, and filter. Add 2 L of methanol to the filtrate, add a trace amount of antioxidant 168 as a seed, let it stand for 6 hours for crystallization, some of the product precipitates, and filter. Add 2 L of methanol to the filtrate, add a trace amount of antioxidant 168 as a seed, let it stand for 6 hours for crystallization, some of the product precipitates, and filter. Repeat the above steps until no product precipitates in the filtrate, consuming a total of 10 L of methanol. The filter cake was vacuum dried at 20 mbar and 50 °C for 5 hours. 876.85 g of white powder product was obtained, with a yield of 94.64%. Sampling was performed and product quality index testing was carried out in accordance with HG / T 3712-2010 "Antioxidant 168". Figure 4 As shown, 2.1 min: solvent peak caused by the difference between the sample dissolving solvent and the mobile phase, which is not an impurity and is not included in the content calculation; 2.4 min: 2,4-di-tert-butylphenol; 14.3 min: antioxidant 168; the main content of antioxidant 168 in the product is 99.85%, the phenol content is 0.15%, the acid value is 0.18 mg KOH / g, and the melting point is 183.5~184.4 ℃.

[0027] In the post-treatment method adopted in this comparative example, since xylene is not removed after the reaction is completed, the added methanol is mixed with xylene. Therefore, if the methanol is separated by a simple distillation as in Example 2, a small amount of xylene will still be contained in the recovered methanol washing liquid. Figure 5 As shown in the figure (2.4 min: 2,4-di-tert-butylphenol; 2.7 min: solvent xylene; 13.6 min: antioxidant 168), a small amount of antioxidant 168 product is dissolved, resulting in product loss and decreased product yield.

[0028] Comparative Example 2 This comparative example is compared with Example 2. This comparative example provides a post-treatment method for antioxidant 168 (post-treatment of antioxidant 168 synthesized by solvent method, first removing the reaction solvent to obtain a solid material, and then adding a large amount of solvent to completely dissolve the solid material), comprising the following steps: Synthesis of antioxidant 168: Using phosphorus trichloride (200.0 g) and 2,4-di-tert-butylphenol (886.4 g) as raw materials, xylene (500 mL) as solvent, and triethylamine (6.25 g) as catalyst, antioxidant 168 was synthesized. The raw material feeding amount and reaction conditions of this comparative example are exactly the same as those of Example 2.

[0029] Post-treatment: After the reaction is completed, first remove the reaction solvent by vacuum distillation to obtain a solid material, then add 24 L of methanol to the solid material and heat and stir at 80 °C for 6 hours to completely dissolve the solid material. Then, cool to room temperature, let stand for 6 hours to crystallize, and the product precipitates and is filtered. The filter cake is vacuum dried at 20 mbar and 50 °C for 5 hours. 881.75 g of white powder product is obtained with a yield of 95.16%. Take samples and test the product quality indicators according to HG / T 3712-2010 "Antioxidant 168". Figure 6 As shown, 2.1 min: solvent peak caused by the difference between the sample dissolving solvent and the mobile phase, which is not an impurity and is not included in the content calculation; 2.5 min: 2,4-di-tert-butylphenol; 14.9 min: antioxidant 168; the main content of antioxidant 168 in the product is 99.88%, phenol content is 0.05%, acid value is 0.07 mg KOH / g, and melting point is 183.9~184.6 ℃.

[0030] The post-treatment method adopted in this comparative example is to directly and completely remove xylene after the reaction to obtain a solid material, which has a strong hardness (such as Figure 7 As shown in the figure, it is necessary to manually break up the lumps, add large amounts of methanol and heat to accelerate the dissolution of the solids.

[0031] Comparative Example 3 This comparative example is compared with Example 2. This comparative example provides a post-treatment method for antioxidant 168 (post-treatment of antioxidant 168 synthesized by solvent method, first removing the reaction solvent to obtain a solid material, and then adding a small amount of solvent to partially dissolve the solid material), comprising the following steps: Synthesis of antioxidant 168: Using phosphorus trichloride (200.0 g) and 2,4-di-tert-butylphenol (886.4 g) as raw materials, xylene (500 mL) as solvent, and triethylamine (6.25 g) as catalyst, antioxidant 168 was synthesized. The raw material feeding amount and reaction conditions of this comparative example are exactly the same as those of Example 2.

[0032] Post-treatment: After the reaction is completed, first remove the reaction solvent by vacuum distillation to obtain a solid material, then add 2 L of methanol to the solid material and heat and stir at 80 °C for 6 h to partially dissolve the solid material. Then, cool to room temperature, let stand for 6 h to crystallize, and the product precipitates and is filtered. The filter cake is vacuum dried at 20 mbar and 50 °C for 5 h. 901.3 g of white powder product is obtained with a yield of 97.27%. Take samples and test the product quality indicators according to HG / T 3712-2010 "Antioxidant 168". Figure 8As shown, 2.1 min: solvent peak caused by the difference between the sample dissolving solvent and the mobile phase, which is not an impurity and is not included in the content calculation; 2.5 min: 2,4-di-tert-butylphenol; 14.9 min: antioxidant 168; the main content of antioxidant 168 in the product is 97.33%, the phenol content is 1.67%, the acid value is 0.32 mg KOH / g, and the melting point is 182.7~183.8℃.

[0033] The post-treatment method adopted in this comparative example is to directly and completely remove xylene after the reaction to obtain a solid material. The solid material has strong hardness and needs to be manually broken into pieces, and a large amount of methanol needs to be added and heated to accelerate the dissolution of the solid.

[0034] Table 1 Summary of experimental parameters and product conditions of the embodiments and comparative examples

[0035] The experimental parameters and product conditions of Examples 1-2 and Comparative Examples 1-3 are summarized in Table 1. It can be seen from the data in the table that the efficient post-treatment method for obtaining high-purity antioxidant 168 provided by the present invention has strong universality and is suitable for treating crude antioxidant 168 products with solvent synthesis methods and solvent-free synthesis methods. The product purity is ≥99.80%, and the amount of washing solvent is small, and the washing time is short. Comparative Example 1 shows that if the conventional anti-solvent crystallization method is adopted, that is, after the reaction is completed, the reaction solvent is not evaporated, and a poor solvent with poor solubility in antioxidant 168 is added after cooling to crystallize antioxidant 168. This method consumes a large amount of solvent and takes a long time, and if the solvent is to be recycled, it is necessary to distill and separate the solvent; in addition, there is a small amount of xylene in the recovered methanol, which dissolves a small amount of antioxidant 168 product, resulting in product loss and a decrease in product yield. Comparative Example 2 shows that if a conventional recrystallization method is used, that is, after the reaction is completed, the reaction solvent is first removed by distillation under reduced pressure to obtain a solid material, then methanol is added to the solid material and heated and stirred to completely dissolve the solid material, and then the temperature is reduced to crystallize. This method requires a large amount of solvent and takes a long time. Comparative Example 3 shows that if after the reaction is completed, the reaction solvent is first removed by distillation under reduced pressure to obtain a solid material, then methanol is added to the solid material and heated and stirred to partially dissolve the solid material, and then the temperature is reduced to crystallize. Since the solid material of this method is coated with impurities, the product purity is low.

[0036] In summary, the post-treatment method of antioxidant 168 provided by the present invention is the most efficient, the product crystallizes quickly, the amount of washing solvent is small, and the washing time is short.

Claims

1. An efficient post-treatment method for obtaining high-purity antioxidant 168, characterized in that: The following steps are involved: S1: The crude product of antioxidant 168 is cooled and precipitated into white crystalline particles under an inert gas atmosphere and stirring, thereby obtaining a granular crude product of antioxidant 168; S2: Add methanol, stir and wash, and filter; S3: vacuum drying to obtain white powdery high-purity antioxidant 168.

2. The efficient post-treatment method for obtaining high-purity antioxidant 168 according to claim 1, characterized in that: It is applicable to the system of synthesizing antioxidant 168 by solvent method and the system of synthesizing antioxidant 168 by solvent-free method.

3. The efficient post-treatment method for obtaining high-purity antioxidant 168 according to claim 2, characterized in that: For the system of synthesizing antioxidant 168 by solvent method, S1 is specifically as follows: when the crude product of liquid antioxidant 168 is subjected to reduced pressure distillation to remove the solvent until it becomes viscous, an inert gas at a flow rate of 20-40 mL / min is introduced, and the inert gas atmosphere is maintained while stirring to precipitate white crystalline particles of the viscous crude product of antioxidant 168, and then the solvent is further removed by reduced pressure distillation until no solvent is evaporated to obtain a granular crude product of antioxidant 168.

4. The efficient post-treatment method for obtaining high-purity antioxidant 168 according to claim 2, characterized in that: For the system of solvent-free synthesis of antioxidant 168, S1 is specifically as follows: an inert gas at a flow rate of 80-100 mL / min is immediately introduced into the liquid crude antioxidant 168 obtained after the reaction is completed. When the crude antioxidant 168 turns slightly white, the inert gas flow rate is reduced to 20-40 mL / min. Under the inert gas atmosphere and stirring, the crude antioxidant 168 becomes viscous and white crystalline particles are gradually precipitated to obtain granular crude antioxidant 168.

5. The efficient post-treatment method for obtaining high-purity antioxidant 168 according to claim 1, characterized in that: S2 specifically comprises: adding methanol to the crude granular antioxidant 168 product according to a mass ratio of 1:0.15-1.6 between the crude granular antioxidant 168 product and methanol, stirring and washing at 20-80°C for 5-30 min, filtering with suction, and repeatedly washing the filter cake 1-2 times; preferably, the mass ratio of the crude granular antioxidant 168 product to methanol is 1:0.8, stirring and washing at 30°C for 10 min, filtering with suction, and repeatedly washing the filter cake once.

6. The efficient post-treatment method for obtaining high-purity antioxidant 168 according to claim 1, characterized in that: S3 is specifically: vacuum drying for 3 to 12 hours at 10 to 100 mbar and 30 to 60°C to obtain a white powdery high-purity antioxidant 168; preferably, vacuum drying for 4 to 6 hours at 10 to 20 mbar and 50°C to obtain a white powdery high-purity antioxidant 168.

7. The efficient post-treatment method for obtaining high-purity antioxidant 168 according to claim 1, characterized in that: The inert gas is at least one of nitrogen, helium or argon.

8. The efficient post-treatment method for obtaining high-purity antioxidant 168 according to claim 3, characterized in that: The reduced pressure distillation conditions are: system temperature 120-125°C, pressure 200-600 mbar.

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