Synthetic method of antioxidant 618

Abstract

The invention discloses a synthesis process of an antioxidant 618. According to the synthesis process, the antioxidant 618 is synthesized by utilizing a two-step one-pot method, a corresponding catalyst and a solvent are added into a reaction kettle with pentaerythritol, phosphorus oxychloride is slowly and dropwise added into the reaction kettle, and a reaction is performed under the condition of micro-negative pressure to generate an intermediate dichloropentaerythritol phosphite. And after the first-step reaction is completed, adding a corresponding acid-binding agent and stearyl alcohol into the system to carry out a second-step reaction, and then carrying out a series of post-treatments to obtain the antioxidant 618. Compared with the traditional synthesis process, the synthesis process has the advantages that the strongly basic anion resin is used as the catalyst and can be repeatedly used, in addition, the strongly basic anion resin is also used as the catalyst and can be repeatedly used, and in addition, the synthesis process has the advantages of mild reaction conditions, simple reaction steps, low cost, high yield, good product quality and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic synthesis, and in particular relates to a synthesis process of an antioxidant 618. Background Art

[0002] Phosphite antioxidants are a type of auxiliary antioxidant widely used in polymer materials. They have excellent properties such as no pollution, low toxicity, low volatility and high thermal stability.

[0003] Antioxidant 618, chemical name: distearyl pentaerythritol diphosphite, trade name AP-618. It was developed by BorgWarner in the United States in the 1970s. It is an environmentally friendly and non-toxic phosphite antioxidant. It is mainly used as an auxiliary antioxidant for various synthetic resins such as polyethylene, polypropylene, polyvinyl chloride, ABS resin and polyester. It has an outstanding effect on preventing oxidation and improving color; it has high thermal stability, weather resistance and hydrolysis stability, so it has good processing stability. This product is very suitable for polymer materials that require high-temperature processing due to its pentaerythritol structure and high molecular weight characteristics. Due to the diphosphite structure, the alkyl trivalent phosphorus content is high, making the antioxidant effect more prominent and efficient. The product does not contain alkylphenol in structure, which complies with new market regulations and development trends. It has been approved by relevant food and health agencies in many countries and can be used for food packaging materials.

[0004] There are currently three synthetic processes for producing antioxidant 618 on the market: (1) The two-step method for synthesizing antioxidant 618 using pentaerythritol, triphenyl phosphite and octadecanol as raw materials, but the production cost of this synthetic process is too high, and the product also contains phenol, a byproduct that is easily oxidized and yellowed, which limits its application in food and pharmaceutical packaging. (2) The synthetic process using pentaerythritol, triethyl phosphite and octadecanol as raw materials to synthesize antioxidant 618 solves the problem of byproduct phenol causing product yellowing compared to (1), and the generated byproduct ethanol can also be sold. It is a green and environmentally friendly synthetic process, but the vacuum degree required for this process is very high and difficult to achieve in industry. (3) The two-step one-pot method for synthesizing antioxidant 618 using pentaerythritol, phosphorus trichloride and octadecanol as raw materials. For example, Chinese patent application 202310011583.7 discloses a synthetic process for antioxidant 618. Although the reaction conditions of this process are mild and the product yield is high, the quality of the product synthesized by this synthetic process is low.

[0005] Micro-negative pressure reaction is a reaction that can reduce the pressure in a closed reaction container. It is generally suitable for reactions that generate gas. Compared with traditional reactions that generate gas, it has the following advantages: shortening the reaction time, increasing the reaction rate, and increasing the reaction yield. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention proposes a synthesis process of antioxidant 618 (distearyl pentaerythritol diphosphite), which uses a strong alkaline anion resin as a catalyst, can be reused multiple times, has mild reaction conditions, high product yield and good product quality, and is easy to industrialize.

[0007] The present invention proposes a synthesis process of antioxidant 618, and the specific experimental steps of the process are as follows: A synthesis process of antioxidant 618 comprises the following steps: I. under the condition of catalyst, phosphorus trichloride solution is added dropwise to pentaerythritol solution to carry out reaction; In some embodiments, the step I further includes using a slight negative pressure to discharge the hydrogen chloride gas generated during the reaction.

[0008] II. After the reaction in step I is completed, an acid binding agent and octadecyl alcohol are added to the system to continue the reaction. After the reaction is completed, an antioxidant 618 is obtained through a post-treatment step.

[0009] The reaction formula is as follows: ; The mass concentration of the pentaerythritol solution in step I is 0.1-1.0 g / mL; the concentration of the phosphorus trichloride solution is 0.01-1.0 mol / mL; wherein the solvent for dissolving pentaerythritol and phosphorus trichloride is selected from any one of toluene, benzene, DMSO, and DMF.

[0010] The catalyst is any one of strongly basic anionic resin, triethylamine, tetrabutylammonium bromide, dimethylformamide and 1,3-pentanediamine.

[0011] The model of the strong base anion resin is any one of Purolite A510 DL Plus strong base anion resin, Dow A strong base anion resin, LANXESS Mono Plus M500 strong base anion resin, and Rohm and Haas 4200 CL strong base anion resin.

[0012] The amount of the catalyst is 2.0%-4.0% of the mass of pentaerythritol, wherein the optimal amount is 3.0-3.5% of the mass of pentaerythritol.

[0013] The molar ratio of pentaerythritol to phosphorus trichloride is 1:2.0-3.0, wherein the optimal molar ratio is 1:2.1-2.5.

[0014] The temperature for adding phosphorus trichloride dropwise in the above step I is 10-25° C., and after the addition of phosphorus trichloride is complete, the reaction temperature is 40-50° C., and the reaction time is 4-5 h.

[0015] During the reaction, the hydrogen chloride gas generated by the reaction is removed by using a slight negative pressure. The vacuum degree of the reaction is 500-700 mbar, wherein the optimal vacuum degree is 600-650 mbar.

[0016] After the reaction in step I is completed, the post-treatment of the strong basic anion resin is also included. The post-treatment method of the strong basic anion resin is to pass it through a column with a 4-10% sodium hydroxide solution. After the treatment is completed, the column bed and the alkali remaining in the resin pores are washed with deionized water until the pH of the outlet liquid is ≤10, and then the water washing is stopped. At least a certain liquid surface layer is retained on the resin bed to prevent the column from drying out.

[0017] The molar amount of the acid-binding agent ammonia used in the aforementioned step II is 2.0-2.5 times the molar amount of pentaerythritol.

[0018] The order of adding materials must be to first add the acid-binding agent liquid ammonia to the system, and then add octadecyl alcohol when the system is alkaline (PH=8-9).

[0019] The molar amount of octadecyl alcohol in the aforementioned step II is 2.0-2.2 times the molar amount of pentaerythritol.

[0020] The reaction temperature in the aforementioned step II is 70-90° C., and the reaction time is 1-2 h.

[0021] The synthesis process of the antioxidant 618 provided by the present invention has the following advantages compared with the existing antioxidant 618: 1. The present invention does not use a nitrogen blowing method to remove the hydrogen chloride gas continuously generated in step I, but places the reaction under a slightly negative pressure condition to remove the hydrogen chloride gas generated during the reaction, which not only shortens the reaction time, but also improves the reaction yield and saves the reaction cost.

[0022] 2. The catalyst used in the present invention is a strongly basic anionic resin, which can be reused many times, thus saving reaction costs.

[0023] 3. The acid-binding agent used in the present invention is ammonia gas, and the generated by-product is ammonium chloride, which can not only be sold but also reduce the cost of post-processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The phosphorus spectrum of distearyl pentaerythritol diphosphite synthesized by the catalyst of Example 1 is Purolite A510 DL Plus strong basic anion resin ( 31 P)Fig.

[0025] Figure 2 In Example 3, octadecyl alcohol is first added, and then ammonia is introduced, and the phosphorus spectrum of the product is obtained by post-treatment ( 31 P)Fig. DETAILED DESCRIPTION

[0026] In order to express the technical solution provided by the present invention in more detail, the present invention is further described below in conjunction with examples. However, the specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0027] Example 1 Effect of catalyst on reaction: Weigh 0.1 mol of pentaerythritol (13.6 g) in a 500 mL container equipped with an electric stirrer, a thermometer, a condenser and an ammonia inlet tube, measure 50 mL of toluene as a solvent, then add 0.48 g of catalyst, and slowly drop 0.21 mol of phosphorus trichloride solution (18.3 mL of phosphorus trichloride is diluted with 18 mL of toluene) at 10 °C. After the phosphorus trichloride solution is added, heat it to 45 °C and react under a negative pressure of 650 mbar. After reacting for 4 h, take a sample and measure the content by gas chromatography. (The catalyst is triethylamine, dimethylformamide (DMF), tetrabutylammonium bromide, 1,3-pentanediamine (DMAP), and a strong basic anion resin, wherein the strong basic anion resin is selected from Amberlite A510 DL Plus, Dow A, Lanxess Mono Plus M500, Rohm and Haas 4200 CL, and the weak basic anion resin is selected from Amberlite A21 and D301 macroporous type).

[0028] After the first step of the reaction was completed, 0.2 mol (4.48 L) of ammonia was introduced into the system until the pH was 8-9, and then 0.205 mol of octadecyl alcohol (55.45 g) was added and reacted at 70 °C and 650 mbar negative pressure for 1 h.

[0029] After the second step reaction was completed, the ammonium chloride generated by the reaction was filtered out while hot, and activated carbon was added and stirred for 15 min before filtering to remove the toluene solvent. The obtained product results are shown in Table 1.

[0030] For the above reaction steps, adjusting different catalysts has the following beneficial effects: Table 1: Effect of catalyst on reaction:

[0031] As can be seen from Table 1, the first step catalyst is a strong basic anion resin, and the yield and purity of the antioxidant 618 generated by the reaction are the highest. Therefore, the best catalyst of the present invention is a strong basic anion resin.

[0032] For the implementation case using Purolite A510 DL Plus strong alkaline anion resin, the post-treatment method of Purolite A510 DLPlus anion resin is to use a 4% sodium hydroxide solution to pass it through the column. After the treatment, use deionized water to wash away the alkali remaining in the column bed and the resin pores until the pH of the outlet liquid is 8.5, stop washing, and at least retain a certain liquid surface layer on the resin bed to prevent dry column. The recovered Purolite A510 DL Plus anion resin is subjected to the steps of the above embodiment 1 again. After 12 survivals, a product is obtained. The physical and chemical properties of the obtained product are as follows: Table 2:

[0033] It can be seen from Table 2 that as the number of cycles of the strong base anion resin increases, its activity will gradually decrease. Therefore, after the strong base anion resin has been cycled 5 times, it is reactivated.

[0034] Example 2 Effect of vacuum degree on reaction: Weigh 0.1 mol of pentaerythritol (13.6 g) in a four-necked flask equipped with an electric stirrer, a thermometer, a condenser and a 500 mL ammonia inlet tube, measure 50 mL of toluene as a solvent, then add 0.48 g of a strong alkaline anion resin as a catalyst (Lanxess Mono Plus M500), and slowly drop 0.21 mol of phosphorus trichloride (18.3 mL of phosphorus trichloride was diluted with 18 mL of toluene) at 10 °C. After the phosphorus trichloride was added, the temperature was raised to 45 °C and the reaction was carried out under negative pressures of 400 mbar, 650 mbar, and 800 mbar. After the reaction for 4 h, the sample was taken and the content was determined by gas chromatography.

[0035] After the first step of the reaction was completed, the strong alkaline anion resin in the reaction was filtered out, and then 0.2 mol of liquid ammonia (4.48 L of ammonia gas) was introduced into the system, followed by 0.205 mol of octadecyl alcohol (55.45 g), and the reaction was carried out at 70°C and under negative pressures of 400 mbar, 650 mbar, and 800 mbar for 1 h.

[0036] After the reaction was completed, the ammonium chloride generated by the reaction was filtered out while hot, and activated carbon was added and stirred for 15 min before filtering to remove the toluene solvent. The obtained product results are shown in Table 3.

[0037] Table 3: Effect of vacuum degree on reaction

[0038] As shown in Table 3, the vacuum degree of the reaction is 650 mbar. The yield and purity of the target product antioxidant 618 are the highest, so the optimal vacuum degree of the present invention is 650 mbar.

[0039] Example 4 Step 2 Effect of the order of adding materials on the reaction: First add octadecyl alcohol and then pass liquid ammonia: Weigh 0.1 mol of pentaerythritol (13.6 g) in a 500 mL three-necked flask, measure 50 mL of toluene as solvent, then add 0.48 g of strong basic anion resin (Rohm and Haas 4200 CL), and slowly drop 0.21 mol of phosphorus trichloride (18.3 mL of phosphorus trichloride is diluted with 18 mL of toluene) at 10 °C. After the phosphorus trichloride is added, heat to 45 °C and react under a negative pressure of 650 mbar. After reacting for 4 h, take a sample and measure the content by gas chromatography.

[0040] After the first step of the reaction was completed, the strongly basic anion resin in the reaction was filtered out, and then 0.205 mol of octadecyl alcohol (55.45 g) was added thereto, followed by 0.2 mol of ammonia gas (4.48 L), and then the reaction was carried out at 70 °C and 650 mbar negative pressure for 1 h.

[0041] After the reaction is completed, the ammonium chloride generated by the reaction is filtered out while hot, and activated carbon is added, stirred for 15 min, and then filtered to remove the toluene solvent to obtain the product. 31 See P figure Figure 2 ,Depend on 31 It can be seen from Figure P that no product was generated.

[0042] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for synthesizing antioxidant 618, characterized in that: The following steps are involved: I. under the condition of catalyst, phosphorus trichloride solution is added dropwise to pentaerythritol solution to carry out reaction; II. After the reaction in step I is completed, an acid binding agent and octadecyl alcohol are added to the system to continue the reaction. After the reaction is completed, an antioxidant 618 is obtained through a post-treatment step.

2. The synthesis method according to claim 1, characterized in that The mass concentration of the pentaerythritol solution in step I is 0.1-1.0 g / mL; the concentration of the phosphorus trichloride solution is 0.01-1.0 mol / mL; wherein the solvent for dissolving pentaerythritol and phosphorus trichloride is selected from any one of toluene, benzene, DMSO, and DMF.

3. The synthesis method according to claim 1, characterized in that The catalyst is any one of strongly basic anionic resin, triethylamine, tetrabutylammonium bromide, dimethylformamide and 1,3-pentanediamine.

4. The synthesis method according to claim 1, characterized in that The model of the strong base anion resin is any one of Purolite A510DL Plus strong base anion resin, Dow A strong base anion resin, LANXESS Mono Plus M500 strong base anion resin, and Rohm and Haas 4200 CL strong base anion resin.

5. The synthesis method according to claim 1, characterized in that The amount of the catalyst is 2.0%-4.0% of the mass of pentaerythritol, wherein the optimal amount is 3.0-3.5% of the mass of pentaerythritol.

6. The synthesis method according to claim 1, characterized in that In step I, the temperature for dropping the phosphorus trichloride solution is 10-25° C., and after the phosphorus trichloride is added dropwise, the reaction temperature is 40-50° C., and the reaction time is 4-5 h.

7. The synthesis method according to claim 1, characterized in that During the reaction of step I, the hydrogen chloride gas generated by the reaction is removed by slight negative pressure during the reaction, and the vacuum degree of the reaction is 400-800 mbar, wherein the optimal vacuum degree is 600-650 mbar.

8. The synthesis method according to claim 1, characterized in that The acid-binding agent is ammonia or triethylamine, wherein the molar amount of the acid-binding agent is 2.0-2.5 times the molar amount of pentaerythritol.

9. The synthesis method according to claim 1, characterized in that The molar amount of octadecyl alcohol is 2.0-2.2 times the molar amount of pentaerythritol.

10. The synthesis method according to claim 1, characterized in that The reaction temperature of step II is 70-90°C and the reaction time is 1-2h.

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