Purification method for removing organic chlorine impurities in light stabilizer 2020

Abstract

The invention discloses a purification method for removing organic chlorine impurities in a light stabilizer 2020, which comprises the following steps: in a nitrogen protection environment, transferring a xylene solution after a synthesis reaction of the light stabilizer 2020, a pre-prepared alkaline ethylene glycol mixed solution and a phase transfer catalyst into a high-pressure reaction kettle; and carrying out a deep dechlorination reaction through programmed temperature control. After the reaction is completed, gradient cooling is conducted, standing is conducted, a lower-layer ethylene glycol phase is separated out, then ethylene glycol washing and water washing are conducted, filtering and molecular distillation are conducted, and a high-purity light stabilizer 2020 product is obtained. By optimizing a reaction medium system and operation parameters, the residual quantity of chlorinated byproducts is remarkably reduced, and meanwhile, the method has the following advantages that emission of volatile organic compounds is effectively reduced by adopting a closed reaction system; the ethylene glycol-alkaline system has a synergistic effect to improve the dechlorination efficiency, and use of a heavy metal catalyst is avoided; the process conditions are mild, the solvent can be recycled, and the production cost is reduced; molecular distillation is adopted to replace a traditional distillation mode, so that the product chromaticity is remarkably reduced, and the light transmittance is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polymer material modification aids, and particularly relates to a purification method for removing organic chlorine impurities in a light stabilizer 2020. BACKGROUND

[0002] Hindered amine light stabilizers have become the mainstream choice in the field of polymer material anti-aging due to their excellent free radical capture ability, extraction resistance and migration resistance. Light stabilizer 2020 is a polymer hindered amine (HALS) with a molecular weight distribution of 2600-3400, and a narrow molecular weight distribution (<1.5), which is significantly better than traditional products (such as light stabilizers 770, 944, etc.), can effectively reduce material surface migration and volatile loss, and prolong the service life of the product.

[0003] Light stabilizer 2020 is synthesized with cyanuric chloride as the core skeleton, and a high molecular chain structure is constructed through multi-step substitution, polycondensation and end-capping reaction. However, due to the high reactivity of cyanuric chloride and the poor stability of the intermediate, the residual chlorine element (especially the intermediate 1 in the end-capping agent) in the process becomes a key bottleneck restricting the quality of the product.

[0004]

[0005] The presence of organic chlorine in light stabilizer 2020 can have a significant negative impact on its performance, safety and application scenarios. For example, organic chlorine can react with the piperidine ring of hindered amine (HALS), reducing its free radical capture activity, and easily releasing Cl⁻ or generating HCl under light or heat conditions, catalyzing the oxidative degradation of polyolefin, engineering plastic and other materials. In the processing steps such as injection molding and extrusion (temperature > 200℃), organic chlorine decomposes to generate HCl, dioxin and other toxic gases, causing equipment corrosion, product yellowing and reduced melt flow. In certain special application scenarios, such as food packaging and medical supplies, the safety requirements are extremely high, and the presence of organic chlorine may pose a health and safety risk. Even a small amount of organic chlorine residue may not meet the relevant industry standards, limiting the application of light stabilizer 2020 in these high-end fields.

[0006] Therefore, in actual production and application process, it is crucial to strictly control the content of organic chlorine in raw materials, optimize the production process to reduce the residual organic chlorine, in order to ensure the performance of light stabilizer 2020 and broaden its application range. SUMMARY

[0007] To address the above issues, the present invention discloses a purification method for removing organochlorine impurities from light stabilizer 2020. Specifically, a xylene solution of light stabilizer 2020, which has been successfully reacted in the workshop, is reacted with an alkaline ethylene glycol solution at high temperature, followed by post-treatment to obtain pure light stabilizer 2020. This method has minimal environmental pollution, low cost, simple operation, and high product yield, making it suitable for industrial production.

[0008] To achieve the above object, the technical solution of the present invention is as follows: A purification method for removing organic chlorine impurities in light stabilizer 2020 comprises the following steps: S1. Under nitrogen protection, the xylene solution after the synthesis reaction of light stabilizer 2020 was transferred to a high-pressure reactor together with a pre-prepared alkaline ethylene glycol mixed solution and a phase transfer catalyst, and a deep dechlorination reaction was performed by programmed temperature control; S2. After the reaction is complete, the temperature is gradually lowered and the lower ethylene glycol phase is allowed to stand and fall off; S3. After washing with ethylene glycol and water, the product is filtered and molecularly distilled to obtain a high-purity light stabilizer 2020 product.

[0009] As an improvement of the present invention, the effective solid mass content of the crude light stabilizer 2020 in the xylene solution of step S1 is 35-45%; the chlorine element in the crude light stabilizer 2020 is greater than 3000 ppm; the alkali mass concentration in the alkaline ethylene glycol mixed solution is 3%-10%; the mass ratio of the ethylene glycol phase to the xylene phase is 1:2-10, and the amount of the phase transfer catalyst used is 0.5%-2% of the mass of the crude light stabilizer 2020.

[0010] As an improvement of the present invention, the alkali in the alkaline ethylene glycol in step S1 is any one of sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, and calcium hydroxide.

[0011] As an improvement of the present invention, the phase transfer catalyst in step S1 is any one of polyethylene glycol, polyethylene glycol dimethyl ether, tetrabutylammonium bromide, and benzyltriethylammonium chloride.

[0012] As an improvement of the present invention, the specific steps of the program temperature control in step S1 are: S11. In the first stage, the temperature is raised to 120-140°C at a rate of 1-10°C / min and maintained for 1-2 hours to allow the system to be fully mixed and activated. S12. In the second stage, the temperature is raised to 160-200°C at a rate of 0.5-5°C / min and the reaction is kept constant for 4-8 hours to complete the main dechlorination process.

[0013] As an improvement of the present invention, the specific steps of the gradient cooling method in step S2 are: cooling at 1-10°C / min to 40-80°C to complete the cooling process.

[0014] As an improvement of the present invention, the molecular distillation conditions of step S3 are: vacuum degree of 5~20Pa, distillation temperature of 60~200°C, feed rate of 10~50mL / min, and scraping speed of 100~600rpm / min.

[0015] The beneficial effects of the present invention are: The present invention provides a purification method for removing organochlorine impurities from light stabilizer 2020. This method involves reacting a xylene solution of light stabilizer 2020 (previously produced in a workshop) with an alkaline ethylene glycol solution at high temperature, followed by post-treatment to obtain pure light stabilizer 2020. Direct dechlorination using the synthetic solution eliminates the need for intermediate product separation, shortens the production cycle, and reduces energy consumption.

[0016] This technical solution innovatively constructs a heterogeneous dechlorination system, in which ethylene glycol and xylene form an azeotropic system, enhancing the mass transfer efficiency while avoiding the possibility of light stabilizer 2020 decomposition at high temperatures, thereby increasing the dechlorination efficiency to over 95%. After the reaction, ethylene glycol and xylene can be recovered and recycled by vacuum distillation. The overall process is green and economical, and meets the clean production standards of fine chemicals.

[0017] Through molecular distillation technology, efficient solvent removal is achieved, which significantly reduces the product color and improves the transmittance. At the same time, the residual xylene content in the system is strictly controlled below 300ppm, effectively expanding the applicability of this product in high-end application fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a GPC comparison chart of the product prepared in Example 1 after dechlorination and before dechlorination. DETAILED DESCRIPTION

[0019] The present invention will be further explained below in conjunction with specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0020] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0021] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0022] Example 1 S1. Under nitrogen protection, transfer 1000g of the xylene solution after the synthesis reaction of Light Stabilizer 2020 (the effective content of the crude light stabilizer 2020 is 400g, and the chlorine content is 5010ppm) together with 200g of a pre-prepared alkaline ethylene glycol mixed solution (10g sodium hydroxide and 190g ethylene glycol) and 4g polyethylene glycol into an autoclave. In the first stage, the temperature was increased to 120℃ at 2℃ / min and kept at this temperature for 1h. In the second stage, the temperature was increased to 180℃ at 1℃ / min and kept at this temperature for 4h.

[0023] S2. After the reaction is complete, cool the autoclave from 180°C to 60°C at a rate of 2°C / min while slowly releasing the pressure to ambient pressure. Transfer the cooled mixture to a separatory funnel and allow it to stand for 30 minutes to separate the lower ethylene glycol phase.

[0024] S3. Add 200g of ethylene glycol and heat to 60°C and stir for 1 hour to separate the lower ethylene glycol phase. Then add 400g of pure water and heat to 60°C and stir for 30min, and wash three times. Then filter and transfer the washed material to a Buchner funnel. Use a microporous filter membrane with a pore size of 0.22μm to remove mechanical impurities during the reaction. Finally, molecular distillation is performed, and the washed organic solvent is added to the feed kettle, a total of 980g (about 1080mL), the vacuum is turned on to 10Pa, and the temperature is raised to 180°C. The cooling water temperature is 25°C, the feed knob is turned on, the feed rate is adjusted to 20mL / min, and the scraping speed is 200rpm / min. Finally, the pure light stabilizer 2020 with a chlorine element of 98ppm is obtained, and the dechlorination rate is 98.04%.

[0025] Example 2 This reaction was essentially the same as Example 1, except that the 200 g pre-prepared alkaline ethylene glycol mixed solution (10 g sodium hydroxide and 190 g ethylene glycol) in step S1 was replaced with 400 g alkaline ethylene glycol mixed solution (20 g sodium hydroxide and 380 g ethylene glycol). The resulting product was pure Light Stabilizer 2020 with a chlorine content of 43 ppm and a dechlorination rate of 99.14%.

[0026] Example 3 The method is basically the same as Example 1, except that: in step S1, 200 g of the pre-prepared alkaline ethylene glycol mixed solution (10 g of sodium hydroxide and 190 g of ethylene glycol) is replaced by 200 g of an alkaline ethylene glycol mixed solution (10 g of potassium carbonate and 190 g of ethylene glycol), and finally a pure light stabilizer 2020 with a chlorine content of 76 ppm is obtained, and the dechlorination rate is 98.48%.

[0027] Example 4 The reaction was essentially the same as in Example 1, except that in step S1, the temperature was programmed to rise to 120°C at a rate of 2°C / min and held for 2 h in the first stage, and then to 160°C at a rate of 1°C / min and held for 5 h in the second stage. The resulting product was pure light stabilizer 2020 containing 118 ppm of chlorine and a dechlorination rate of 97.64%.

[0028] Example 5 The method is basically the same as Example 1, except that 4 g of polyethylene glycol in step S1 is replaced with 4 g of tetrabutylammonium bromide. Finally, a pure light stabilizer 2020 containing 175 ppm of chlorine is obtained, and the dechlorination rate is 96.50%.

[0029] Example 6 The process was essentially the same as in Example 1, except that in step S3, the neutron distillation conditions were changed to 10 Pa, the temperature was raised to 180°C, the feed knob was turned on, the feed rate was adjusted to 10 mL / min, and the scraping speed was adjusted to 350 rpm / min. The resulting product was pure Light Stabilizer 2020 containing 92 ppm of chlorine, a dechlorination rate of 98.16%, and a color of 12 APHA.

[0030] Example 7 This method is essentially the same as Example 1, except that in step S1, the xylene solution after the synthesis reaction of 1000 g of Light Stabilizer 2020 (the crude product of Light Stabilizer 2020 has an effective content of 400 g and a chlorine content of 5010 ppm) is replaced with a xylene solution after the synthesis reaction of 1000 g of Light Stabilizer 2020 (the crude product of Light Stabilizer 2020 has an effective content of 424 g and a chlorine content of 8953 ppm). The resulting pure Light Stabilizer 2020 has a chlorine content of 315 ppm and a dechlorination rate of 96.48%.

[0031] Comparative Example 1 The method is basically the same as Example 1, except that: 4 g of polyethylene glycol is used in step S1 instead of using a phase transfer catalyst, and finally a pure light stabilizer 2020 with a chlorine element content of 778 ppm is obtained, and the dechlorination rate is 84.47%.

[0032] Comparative Example 2 The method is basically the same as Example 1, except that the molecular distillation technology in step S3 is replaced by conventional vacuum distillation technology, and finally a pure light stabilizer 2020 with a chlorine element of 83 ppm, a dechlorination rate of 98.34%, a xylene residue of 9353 ppm, and a chromaticity of 48 APHA is obtained.

[0033] Comparative Example 3 The reaction was basically the same as Example 1, except that 200 g of ethylene glycol solution was added instead of the 200 g pre-prepared alkaline ethylene glycol mixed solution (10 g of sodium hydroxide and 190 g of ethylene glycol) in step S1. Finally, a pure light stabilizer 2020 with a chlorine content of 4896 ppm was obtained, and the dechlorination rate was only 2.27%.

[0034] Experimental testing The samples obtained in Examples 1 to 7 and Comparative Examples 1 to 3 were subjected to liquid phase, colorimetry, light transmittance, chlorine element, and thermogravimetric testing, and the results are shown in the following table:

[0035] It should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. For ordinary technicians in this technical field, without departing from the principles of the present invention, several improvements and modifications can be made on the basis of the above embodiments, and these improvements and modifications all fall within the scope of protection of the claims of the present invention.

Claims

1. A purification method for removing organic chlorine impurities in light stabilizer 2020, characterized in that: The steps include: S1. Under nitrogen protection, the xylene solution after the synthesis reaction of light stabilizer 2020 was transferred to a high-pressure reactor together with a pre-prepared alkaline ethylene glycol mixed solution and a phase transfer catalyst, and a deep dechlorination reaction was performed by programmed temperature control; S2. After the reaction is complete, the temperature is gradually lowered and the lower ethylene glycol phase is allowed to stand and fall off; S3. After washing with ethylene glycol and water, the product is filtered and molecularly distilled to obtain a high-purity light stabilizer 2020 product.

2. The method for removing organic chlorine impurities from light stabilizer 2020 according to claim 1, characterized in that: The effective solid mass content of the crude light stabilizer 2020 in the xylene solution of step S1 is 35-45%; the chlorine element in the crude light stabilizer 2020 is greater than 3000 ppm; the alkali mass concentration in the alkaline ethylene glycol mixed solution is 3%-10%; the mass ratio of the ethylene glycol phase to the xylene phase is 1:2-10, and the amount of the phase transfer catalyst used is 0.5%-2% of the mass of the crude light stabilizer 2020.

3. The method for removing organic chlorine impurities from light stabilizer 2020 according to claim 1, characterized in that: The alkali in the alkaline ethylene glycol in step S1 is any one of sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, and calcium hydroxide.

4. The method for removing organic chlorine impurities from light stabilizer 2020 according to claim 1, characterized in that: The phase transfer catalyst in step S1 is any one of polyethylene glycol, polyethylene glycol dimethyl ether, tetrabutylammonium bromide, and benzyltriethylammonium chloride.

5. The method for removing organic chlorine impurities from light stabilizer 2020 according to claim 1, characterized in that: The specific steps of the program temperature control in step S1 are: S11. In the first stage, the temperature is raised to 120-140°C at a rate of 1-10°C / min and maintained for 1-2 hours to allow the system to be fully mixed and activated. S12. In the second stage, the temperature is raised to 160-200°C at a rate of 0.5-5°C / min and the reaction is kept constant for 4-8 hours to complete the main dechlorination process.

6. The method for removing organic chlorine impurities from light stabilizer 2020 according to claim 1, characterized in that: The specific steps of the gradient cooling method in step S2 are: cooling at a rate of 1-10°C / min to 40-80°C to complete the cooling process.

7. The method for removing organic chlorine impurities from light stabilizer 2020 according to claim 1, characterized in that: The molecular distillation conditions in step S3 are: vacuum degree of 5-20 Pa, distillation temperature of 60-200° C., feed rate of 10-50 mL / min, and scraping speed of 100-600 rpm / min.

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