A method for synthesizing bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate
Patent Information
- Application Number
- CN202610992173.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-06
- Publication Date
- 2026-08-21
AI Technical Summary
[0003]上述合成路线因原料易得、工艺成熟，成为工业化首选路线，但在实际应用中存在一些问题：（1）季戊四醇羟基取代选择性失控，单/三取代副产物与目标中间体结构相似难以分离，导致产物纯度偏低，且中间体易与缚酸剂络合，降低反应活性；（2）三氯化磷对微量水敏感，水解产物易生成隐性杂质，堵塞管路且影响产物性能；（3）BHT位阻导致取代不完全，高温反应易引发BHT氧化，产物色泽和纯度难以达标
本发明提供一种双(2,6-二叔丁基-4-甲基苯基)季戊四醇二磷酸酯的合成方法，具有以下特征：
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Abstract
Description
Technical Field
[0001] This invention relates to the field of organic synthesis and preparation, specifically to a method for synthesizing bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphate. Background Technology
[0002] Bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate is a highly efficient, low-toxicity, and migration-resistant organophosphorus flame retardant. Its classic synthetic route is as follows: using pentaerythritol as an alcohol substrate, phosphorus trichloride as a phosphorus source, and 2,6-di-tert-butyl-4-methylphenol (BHT) as a phenol substrate, pentaerythritol is first partially esterified with phosphorus trichloride to generate the bis(chlorophosphate)pentaerythritol intermediate. Then, the chlorine atom of the intermediate undergoes a substitution reaction with the phenolic hydroxyl group of BHT to remove HCl and generate the target product. An acid-binding agent is required to neutralize the by-product HCl throughout the reaction.
[0003] The above synthetic route has become the preferred route for industrialization due to the availability of raw materials and the maturity of the process. However, there are some problems in practical applications: (1) The selective substitution of pentaerythritol hydroxyl group is out of control. The mono / trisubstituted byproducts are similar in structure to the target intermediate and are difficult to separate, resulting in low product purity. In addition, the intermediate is easy to complex with the acid binding agent, which reduces the reaction activity. (2) Phosphorus trichloride is sensitive to trace amounts of water. The hydrolysis product is easy to generate hidden impurities, which can block the pipeline and affect the product performance. (3) The steric hindrance of BHT leads to incomplete substitution. The high temperature reaction can easily trigger the oxidation of BHT, and the color and purity of the product are difficult to meet the standards.
[0004] Therefore, it is essential to invent a method for synthesizing bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphate with high yield, high purity, good industrial batch stability, low impurity content, and environmental friendliness. Summary of the Invention
[0005] To address the aforementioned technical problems, this invention aims to develop a method for synthesizing bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate. This method utilizes precise pretreatment of raw materials, a composite acid-binding agent system formed by triethylamine and pyridine, low-temperature dropwise addition and phase-transfer catalyst synergistic control of intermediate synthesis, substitution reaction with sterically hindered release of 18-crown ether-6 and synergistic antioxidant effect of triphenyl phosphite, combined with precise impurity removal by modified activated alumina and replacement with environmentally friendly solvent methylcyclohexane, to achieve efficient synthesis of the target product.
[0006] This invention discloses a method for synthesizing bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate, comprising the following steps:
[0007] S1 raw material pretreatment: Pentaerythritol was vacuum dried at 105℃ for 2 hours, phosphorus trichloride was dehydrated by distillation, BHT was pulverized to 100 mesh, and dried with molecular sieve in methylcyclohexane as solvent. Synthesis of S2 pentaerythritol bis(chlorophosphate) intermediate: Pentaerythritol and methylcyclohexane pretreated in step S1 were added to a dry reaction vessel, and then dry nitrogen gas was introduced for protection. The mixture was cooled to 0-5℃ and stirred to form a mixture. The dropping rate was controlled, and phosphorus trichloride pretreated in step S1, composite acid binder and tetrabutylammonium bromide were added dropwise to the above mixture. After the addition was completed, the mixture was kept at 0-5℃ for 2-3 hours to obtain the pentaerythritol bis(chlorophosphate) intermediate system. Synthesis and post-treatment purification of the target product S3: The BHT pretreated in step S1 was dissolved in methylcyclohexane and then added dropwise to the pentaerythritol bis(chlorophosphate) intermediate system obtained in step S2. After the addition was complete, 18-crown ether-6 and triphenyl phosphite were added, and the mixture was heated to react for 5 h. After the reaction was completed, the mixture was cooled and washed three times with deionized water. The organic phase was collected, and modified activated alumina was added to the collected organic phase and stirred for 1 h. The filtrate was then collected by filtration. The filtrate was distilled under reduced pressure to obtain a white crystalline crude product. The crude product was then recrystallized from ethanol and dried to obtain the target product, pentaerythritol diphosphate bis(2,6-di-tert-butyl-4-methylphenyl)phosphate.
[0008] Preferably, in step S2, the mass ratio of pentaerythritol to methylcyclohexane is 1:(7~16).
[0009] Preferably, in step S2, the molar ratio of pentaerythritol to phosphorus trichloride is 1:(1.7~2.2).
[0010] Preferably, in step S2, the composite acid binder is composed of triethylamine and pyridine in a molar ratio of 3.1:1.
[0011] Preferably, in step S2, the molar ratio of the composite acid-binding agent to pentaerythritol is 2.1:1.
[0012] Preferably, in step S2, the dropping rate is 0.05~0.1 mL / min.
[0013] Preferably, in step S3, the molar ratio of BHT to pentaerythritol is (2.0~2.5):1.
[0014] Preferably, in step S3, the mass ratio of 18-crown ether-6, triphenyl phosphite, and pentaerythritol is (0.001~0.005):(0.0005~0.001):1.
[0015] Preferably, in step S3, when the temperature is raised to 90~100℃, a composite acid-binding agent needs to be added after the reaction has been going on for 3 hours. The molar ratio of the added composite acid-binding agent to pentaerythritol is 0.8:1.
[0016] Preferably, in step S3, the mass ratio of the modified active alumina to pentaerythritol is (0.15~0.65):1.
[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a method for synthesizing bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate, which has the following characteristics: (1) By using low-temperature dropwise addition and phase transfer catalyst regulation, the purity of the disubstituted intermediate is ≥99.2%, greatly eliminating mono / trisubstituted byproducts, and the final purity of the target product is ≥99.5%.
[0018] (2) By controlling the anhydrous system and using composite acid binders, the hydrolysis of phosphorus trichloride and the complexation of intermediates are eliminated, the residual hidden phosphorus and oxygen impurities are ≤0.01%, the thermal decomposition temperature of the product is stable at 320~325℃, and the flame retardant performance and aging resistance are effectively improved.
[0019] (3) 18-crown ether-6-reducing substitution with a substitution completeness of ≥99.5%.
[0020] (4) No intermediate separation is required, the operation is simple, the batch yield fluctuation is ≤1%, and the total yield is ≥90%; the reduction of wastewater discharge meets the requirements of green and clean production.
[0021] (5) Methylcyclohexane was used to replace toluene, and the solvent residue was ≤80ppm; modified alumina was used for specific phosphorus removal, and the trace phosphorus impurity residue was ≤0.02%. Detailed Implementation
[0022] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.
[0023] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.
[0024] Example 1: A method for synthesizing bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate, comprising the following steps: S1 raw material pretreatment: Pentaerythritol was vacuum dried at 105℃ for 2 hours, phosphorus trichloride was dehydrated by distillation, BHT was pulverized to 100 mesh, and dried with molecular sieve in methylcyclohexane as solvent. Synthesis of S2 pentaerythritol bis(chlorophosphate) intermediate: Pentaerythritol and methylcyclohexane pretreated in step S1 were added to a dry reaction vessel, wherein the mass ratio of pentaerythritol to methylcyclohexane was 1:16. Then, dry nitrogen gas was introduced for protection, and the mixture was cooled to 5°C and stirred to form a mixture. The dropping rate was controlled at 0.1 mL / min. Phosphorus trichloride pretreated in step S1, a composite acid-binding agent, and tetrabutylammonium bromide were added dropwise to the above mixture, wherein the composite acid-binding agent was composed of triethylamine and pyridine in a molar ratio of 3.1:1, and the molar ratio of the composite acid-binding agent to pentaerythritol was 2.1:1; the molar ratio of pentaerythritol to phosphorus trichloride was 1:2.2. After the addition was completed, the mixture was kept at 5°C for 3 h to obtain the pentaerythritol bis(chlorophosphate) intermediate system. Synthesis and post-treatment purification of the target product S3: BHT pretreated in step S1 was dissolved in methylcyclohexane at a molar ratio of 2.5:1 to pentaerythritol. This solution was then added dropwise to the pentaerythritol bis(chlorophosphate) intermediate system obtained in step S2. After the addition was complete, 18-crown ether-6 and triphenyl phosphite were added, with a mass ratio of 0.001:0.0005:1 for 18-crown ether-6, triphenyl phosphite, and pentaerythritol. The reaction was heated to 100℃ and reacted for 5 hours. After 3 hours of reaction, additional compound was added. The acid-binding agent, the added composite acid-binding agent, and the molar ratio of pentaerythritol were 0.8:1. After the reaction was completed, the mixture was cooled and washed three times with deionized water. The organic phase was collected, and modified activated alumina was added to the collected organic phase and stirred for 1 hour. The mass ratio of modified activated alumina to pentaerythritol was 0.65:1. The filtrate was then collected by filtration. The filtrate was distilled under reduced pressure to obtain a white crystalline crude product. The crude product was then recrystallized with ethanol and dried to obtain the target product, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate.
[0025] Example 2: A method for synthesizing bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate, comprising the following steps: S1 raw material pretreatment: Pentaerythritol was vacuum dried at 105℃ for 2 hours, phosphorus trichloride was dehydrated by distillation, BHT was pulverized to 100 mesh, and dried with molecular sieve in methylcyclohexane as solvent. Synthesis of S2 bis(chlorophosphate) pentaerythritol intermediate: Pentaerythritol and methylcyclohexane pretreated in step S1 were added to a dry reaction vessel, wherein the mass ratio of pentaerythritol to methylcyclohexane was 1:14. Then, dry nitrogen gas was introduced for protection, and the mixture was cooled to 4°C and stirred to form a mixture. The dropping rate was controlled at 0.09 mL / min. Phosphorus trichloride pretreated in step S1, a composite acid-binding agent, and tetrabutylammonium bromide were added dropwise to the above mixture, wherein the composite acid-binding agent was composed of triethylamine and pyridine in a molar ratio of 3.1:1, and the molar ratio of the composite acid-binding agent to pentaerythritol was 2.1:1; the molar ratio of pentaerythritol to phosphorus trichloride was 1:2.1. After the addition was completed, the mixture was kept at 4°C for 2.8 h to obtain the bis(chlorophosphate) pentaerythritol intermediate system. Synthesis and post-treatment purification of the target product S3: BHT pretreated in step S1 was dissolved in methylcyclohexane at a molar ratio of 2.4:1 to pentaerythritol. This solution was then added dropwise to the pentaerythritol bis(chlorophosphate) intermediate system obtained in step S2. After the addition was complete, 18-crown ether-6 and triphenyl phosphite were added, with a mass ratio of 0.002:0.0006:1 for 18-crown ether-6, triphenyl phosphite, and pentaerythritol. The reaction was heated to 98℃ and reacted for 5 hours. After 3 hours of reaction, additional compound was added. The acid-binding agent, the added composite acid-binding agent, and the molar ratio of pentaerythritol were 0.8:1. After the reaction was completed, the mixture was cooled and washed three times with deionized water. The organic phase was collected, and modified activated alumina was added to the collected organic phase and stirred for 1 hour. The mass ratio of modified activated alumina to pentaerythritol was 0.55:1. The filtrate was then collected by filtration. The filtrate was distilled under reduced pressure to obtain a white crystalline crude product. The crude product was then recrystallized with ethanol and dried to obtain the target product, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate.
[0026] Example 3: A method for synthesizing bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate, comprising the following steps: S1 raw material pretreatment: Pentaerythritol was vacuum dried at 105℃ for 2 hours, phosphorus trichloride was dehydrated by distillation, BHT was pulverized to 100 mesh, and dried with molecular sieve in methylcyclohexane as solvent. Synthesis of S2 bis(chlorophosphate) pentaerythritol intermediate: Pentaerythritol and methylcyclohexane pretreated in step S1 were added to a dry reaction vessel, wherein the mass ratio of pentaerythritol to methylcyclohexane was 1:12. Then, dry nitrogen gas was introduced for protection, and the mixture was cooled to 3°C and stirred to form a mixture. The dropping rate was controlled at 0.08 mL / min. Phosphorus trichloride pretreated in step S1, a composite acid-binding agent, and tetrabutylammonium bromide were added dropwise to the above mixture, wherein the composite acid-binding agent was composed of triethylamine and pyridine in a molar ratio of 3.1:1, and the molar ratio of the composite acid-binding agent to pentaerythritol was 2.1:1; the molar ratio of pentaerythritol to phosphorus trichloride was 1:2.0. After the addition was completed, the mixture was kept at 3°C for 2.6 h to obtain the bis(chlorophosphate) pentaerythritol intermediate system. Synthesis and post-treatment purification of the target product S3: BHT pretreated in step S1 was dissolved in methylcyclohexane at a molar ratio of 2.3:1 to pentaerythritol. This solution was then added dropwise to the pentaerythritol bis(chlorophosphate) intermediate system obtained in step S2. After the addition was complete, 18-crown ether-6 and triphenyl phosphite were added, with a mass ratio of 0.003:0.0007:1. The mixture was heated to 96℃ and reacted for 5 hours. After 3 hours of reaction, additional compound was added. The acid-binding agent, the added composite acid-binding agent, and the molar ratio of pentaerythritol were 0.8:1. After the reaction was completed, the mixture was cooled and washed three times with deionized water. The organic phase was collected, and modified activated alumina was added to the collected organic phase and stirred for 1 hour. The mass ratio of modified activated alumina to pentaerythritol was 0.45:1. The filtrate was then collected by filtration. The filtrate was distilled under reduced pressure to obtain a white crystalline crude product. The crude product was then recrystallized with ethanol and dried to obtain the target product, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate.
[0027] Example 4: A method for synthesizing bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate, comprising the following steps: S1 raw material pretreatment: Pentaerythritol was vacuum dried at 105℃ for 2 hours, phosphorus trichloride was dehydrated by distillation, BHT was pulverized to 100 mesh, and dried with molecular sieve in methylcyclohexane as solvent. Synthesis of S2 bis(chlorophosphate) pentaerythritol intermediate: Pentaerythritol and methylcyclohexane pretreated in step S1 were added to a dry reaction vessel, wherein the mass ratio of pentaerythritol to methylcyclohexane was 1:10. Then, dry nitrogen gas was introduced for protection, and the mixture was cooled to 2°C and stirred to form a mixture. The dropping rate was controlled at 0.07 mL / min. Phosphorus trichloride pretreated in step S1, a composite acid-binding agent, and tetrabutylammonium bromide were added dropwise to the above mixture, wherein the composite acid-binding agent was composed of triethylamine and pyridine in a molar ratio of 3.1:1, and the molar ratio of the composite acid-binding agent to pentaerythritol was 2.1:1; the molar ratio of pentaerythritol to phosphorus trichloride was 1:1.9. After the addition was completed, the mixture was kept at 2°C for 2.4 h to obtain the bis(chlorophosphate) pentaerythritol intermediate system. Synthesis and post-treatment purification of the target product S3: BHT pretreated in step S1 was dissolved in methylcyclohexane at a molar ratio of 2.2:1 to pentaerythritol. This solution was then added dropwise to the pentaerythritol bis(chlorophosphate) intermediate system obtained in step S2. After the addition was complete, 18-crown ether-6 and triphenyl phosphite were added, with a mass ratio of 0.004:0.0009:1. The mixture was heated to 94℃ and reacted for 5 hours. After 3 hours of reaction, additional compound was added. The acid-binding agent, the added composite acid-binding agent, and the molar ratio of pentaerythritol were 0.8:1. After the reaction was completed, the mixture was cooled and washed three times with deionized water. The organic phase was collected, and modified activated alumina was added to the collected organic phase and stirred for 1 hour. The mass ratio of modified activated alumina to pentaerythritol was 0.35:1. The filtrate was then collected by filtration. The filtrate was distilled under reduced pressure to obtain a white crystalline crude product. The crude product was then recrystallized with ethanol and dried to obtain the target product, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate.
[0028] Example 5: A method for synthesizing bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate, comprising the following steps: S1 raw material pretreatment: Pentaerythritol was vacuum dried at 105℃ for 2 hours, phosphorus trichloride was dehydrated by distillation, BHT was pulverized to 100 mesh, and dried with molecular sieve in methylcyclohexane as solvent. Synthesis of S2 bis(chlorophosphate) pentaerythritol intermediate: Pentaerythritol and methylcyclohexane pretreated in step S1 were added to a dry reaction vessel, wherein the mass ratio of pentaerythritol to methylcyclohexane was 1:9. Then, dry nitrogen gas was introduced for protection, and the mixture was cooled to 1°C and stirred to form a mixture. The dropping rate was controlled at 0.06 mL / min. Phosphorus trichloride pretreated in step S1, a composite acid-binding agent, and tetrabutylammonium bromide were added dropwise to the above mixture, wherein the composite acid-binding agent was composed of triethylamine and pyridine in a molar ratio of 3.1:1, and the molar ratio of the composite acid-binding agent to pentaerythritol was 2.1:1; the molar ratio of pentaerythritol to phosphorus trichloride was 1:1.8. After the addition was completed, the mixture was kept at 1°C for 2.2 h to obtain the bis(chlorophosphate) pentaerythritol intermediate system. Synthesis and post-treatment purification of the target product S3: BHT pretreated in step S1 was dissolved in methylcyclohexane at a molar ratio of 2.1:1 to pentaerythritol. This solution was then added dropwise to the pentaerythritol bis(chlorophosphate) intermediate system obtained in step S2. After the addition was complete, 18-crown ether-6 and triphenyl phosphite were added, with a mass ratio of 0.005:0.001:1 for 18-crown ether-6, triphenyl phosphite, and pentaerythritol. The reaction was heated to 92℃ and carried out for 5 hours. After 3 hours of reaction, a composite binder was added. The acid agent, the added composite acid binder, and the pentaerythritol were added in a molar ratio of 0.8:1. After the reaction was completed, the mixture was cooled and washed three times with deionized water. The organic phase was collected, and modified activated alumina was added to the collected organic phase and stirred for 1 hour. The mass ratio of modified activated alumina to pentaerythritol was 0.25:1. The filtrate was then collected by filtration. The filtrate was distilled under reduced pressure to obtain a white crystalline crude product. The crude product was then recrystallized from ethanol and dried to obtain the target product, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate.
[0029] Example 6: A method for synthesizing bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate, comprising the following steps: S1 raw material pretreatment: Pentaerythritol was vacuum dried at 105℃ for 2 hours, phosphorus trichloride was dehydrated by distillation, BHT was pulverized to 100 mesh, and dried with molecular sieve in methylcyclohexane as solvent. Synthesis of S2 bis(chlorophosphate) pentaerythritol intermediate: Pentaerythritol and methylcyclohexane pretreated in step S1 were added to a dry reaction vessel, wherein the mass ratio of pentaerythritol to methylcyclohexane was 1:7. Then, dry nitrogen gas was introduced for protection, and the mixture was cooled to 0℃ and stirred to form a mixture. The dropping rate was controlled at 0.05 mL / min. Phosphorus trichloride pretreated in step S1, a composite acid-binding agent, and tetrabutylammonium bromide were added dropwise to the above mixture, wherein the composite acid-binding agent was composed of triethylamine and pyridine in a molar ratio of 3.1:1, and the molar ratio of the composite acid-binding agent to pentaerythritol was 2.1:1; the molar ratio of pentaerythritol to phosphorus trichloride was 1:1.7. After the addition was completed, the mixture was kept at 0℃ for 2.0 h to obtain the bis(chlorophosphate) pentaerythritol intermediate system. Synthesis and post-treatment purification of the target product S3: BHT pretreated in step S1 was dissolved in methylcyclohexane at a molar ratio of 2.0:1 to pentaerythritol. This solution was then added dropwise to the pentaerythritol bis(chlorophosphate) intermediate system obtained in step S2. After the addition was complete, 18-crown ether-6 and triphenyl phosphite were added, with a mass ratio of 0.005:0.001:1 for 18-crown ether-6, triphenyl phosphite, and pentaerythritol. The reaction was heated to 90℃ and reacted for 5 hours. After 3 hours of reaction, a composite binder was added. The acid agent, the added composite acid binder, and the pentaerythritol were added in a molar ratio of 0.8:1. After the reaction was completed, the mixture was cooled and washed three times with deionized water. The organic phase was collected, and modified activated alumina was added to the collected organic phase and stirred for 1 hour. The mass ratio of modified activated alumina to pentaerythritol was 0.15:1. The filtrate was then collected by filtration. The filtrate was distilled under reduced pressure to obtain a white crystalline crude product. The crude product was then recrystallized from ethanol and dried to obtain the target product, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate.
[0030] Example 7: The composite acid-binding agent used in steps S2 and S3 was replaced with the single acid-binding agent triethylamine. All other raw materials, steps and experimental parameters were the same as in Example 4.
[0031] Example 8: The solvent used in step S1 was replaced with toluene instead of methylcyclohexane. In subsequent steps, toluene replaced methylcyclohexane. All other raw materials, steps and experimental parameters were the same as in Example 4.
[0032] Example 9: After obtaining the pentaerythritol bis(chlorophosphate) intermediate in step S2, it was washed and dried for use in subsequent steps. The remaining raw materials, steps and experimental parameters were the same as in Example 4.
[0033] The performance of the target product bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphate obtained in Examples 1-9 was tested, and the test results are shown in the table below:
[0034] The data in the table above shows that: (1) In Examples 1-4, the phosphorus trichloride molar ratio was reduced from 1:2.2 to 1:1.9, and the dropping rate was reduced from 0.1 mL / min to 0.07 mL / min. The precise dropping rate at low temperature (2°C) matched the reaction activity of pentaerythritol hydroxyl group. The tetrabutylammonium bromide phase transfer catalyst precisely controlled the di-substitution, eliminating mono / tri-substitution byproducts. At the same time, the BHT molar ratio was reduced from 2.5 to 2.2, reducing excess BHT residue. The amount of 18-crown ether-6 was increased to 0.004, which complexed the tert-butyl group of BHT, reduced steric hindrance, and promoted complete substitution. Therefore, the purity increased from 99.2% to 99.8%, and the substitution completion rate increased from 99.5% to 99.9%. In Examples 5-6, the phosphorus trichloride molar ratio was <1:1.9, and the dropping rate was <0.07 mL / min. Insufficient phosphorus trichloride led to insufficient intermediate formation and insufficient BHT substitution. Therefore, the purity and substitution completion rate decreased slightly.
[0035] (2) In Examples 1-4, the mass ratio of pentaerythritol to methylcyclohexane was reduced from 1:16 to 1:10. The amount of solvent used was moderate, which ensured the dissolution of the reactants and reduced solvent loss. Moreover, the one-pot method did not require the transfer of intermediates, resulting in less material loss and a steady increase in yield to 92.5%. The low-temperature control was precise, the reaction was stable, and the batch fluctuation rate was reduced to 0.8%. In Examples 5-6, the amount of solvent used was further reduced. The excessively high concentration of reactants led to local agglomeration and incomplete reaction, resulting in a slight decrease in yield and a slight increase in fluctuation rate.
[0036] (3) In Examples 1-4, the modified activated alumina dosage was reduced from 0.65:1 to 0.35:1, and the dosage was adapted to the impurity content. It specifically adsorbed phosphorus oxygen impurities generated by the hydrolysis of phosphorus trichloride, and the phosphorus impurity content decreased from 0.018% to 0.012%. The composite acid-binding agent effectively reduced intermediate complexation, the intermediate structure was stable, the phosphoester bond of the product was not easily broken, and the thermal decomposition temperature increased from 321℃ to 324℃. In Examples 5-6, the modified alumina dosage was further reduced, the adsorption capacity was insufficient, the phosphorus impurity content increased slightly, and the thermal decomposition temperature decreased slightly.
[0037] (4) Methylcyclohexane was used in Examples 1 to 6. The solvent was easy to remove and the residue was ≤75ppm. Low phosphorus impurities have no negative impact on plastic performance and the product has high purity. Example 4 has the lowest phosphorus impurities and the highest purity.
[0038] (5) In Example 7, compared with Example 4, the composite acid-binding agent was replaced with a single acid-binding agent, triethylamine. Triethylamine readily forms a coordination complex with the phosphorus atom of the intermediate, reducing the reactivity of the chlorine atom in the intermediate, resulting in an increase in monosubstituted byproducts, a decrease in purity to 98.1%, and a decrease in substitution completeness to 97.2%. The complex is difficult to remove, inducing the decomposition of the intermediate, generating a large amount of phosphorus oxygen impurities, reducing the stability of the phosphoester bond, and lowering the thermal decomposition temperature to 308°C. Insufficient reactivity leads to a decrease in yield to 81.3%.
[0039] (6) Compared with Example 4, Example 8 replaced methylcyclohexane with toluene. The purity, yield and thermal decomposition temperature were similar to those of Example 4, but the solvent residue increased to 510 ppm. This is because the boiling point of toluene is higher than that of methylcyclohexane, and it is difficult to completely remove it by vacuum distillation, resulting in excessive residue; moreover, toluene has slightly poor compatibility with the product.
[0040] (7) Compared with Example 4, Example 9 involved post-processing of the intermediate, which resulted in a decrease in yield to 69.6% and an increase in batch volatility to 1.5%. This is because the intermediate is prone to absorbing moisture when exposed to air, leading to hydrolysis and the generation of impurities. Furthermore, there is significant material loss during the separation process, resulting in a decrease in yield. Stepwise operation is prone to errors in temperature control and feeding, leading to poor batch stability and a volatility exceeding 1%.
[0041] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. A method for synthesizing bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate, characterized in that, Includes the following steps: S1 raw material pretreatment: Pentaerythritol was vacuum dried at 105℃ for 2 hours, phosphorus trichloride was dehydrated by distillation, BHT was pulverized to 100 mesh, and dried with molecular sieve in methylcyclohexane as solvent. Synthesis of S2 pentaerythritol bis(chlorophosphate) intermediate: Pentaerythritol and methylcyclohexane pretreated in step S1 were added to a dry reaction vessel, and then dry nitrogen gas was introduced for protection. The mixture was cooled to 0-5℃ and stirred to form a mixture. The dropping rate was controlled, and phosphorus trichloride pretreated in step S1, composite acid binder and tetrabutylammonium bromide were added dropwise to the above mixture. After the addition was completed, the mixture was kept at 0-5℃ for 2-3 hours to obtain the pentaerythritol bis(chlorophosphate) intermediate system. Synthesis and post-treatment purification of the target product S3: The BHT pretreated in step S1 was dissolved in methylcyclohexane and then added dropwise to the pentaerythritol bis(chlorophosphate) intermediate system obtained in step S2. After the addition was complete, 18-crown ether-6 and triphenyl phosphite were added, and the mixture was heated to react for 5 h. After the reaction was completed, the mixture was cooled and washed three times with deionized water. The organic phase was collected, and modified activated alumina was added to the collected organic phase and stirred for 1 h. The filtrate was then collected by filtration. The filtrate was distilled under reduced pressure to obtain a white crystalline crude product. The crude product was then recrystallized from ethanol and dried to obtain the target product, pentaerythritol diphosphate bis(2,6-di-tert-butyl-4-methylphenyl)phosphate.
2. The method for synthesizing bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphate according to claim 1, characterized in that, In step S2, the mass ratio of pentaerythritol to methylcyclohexane is 1:(7~16).
3. The method for synthesizing bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphate according to claim 1, characterized in that, In step S2, the molar ratio of pentaerythritol to phosphorus trichloride is 1:(1.7~2.2).
4. The method for synthesizing bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphate according to claim 1, characterized in that, In step S2, the composite acid binder is composed of triethylamine and pyridine in a molar ratio of 3.1:
1.
5. The method for synthesizing bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphate according to claim 1, characterized in that, In step S2, the molar ratio of the composite acid binder to pentaerythritol is 2.1:
1.
6. The method for synthesizing bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphate according to claim 1, characterized in that, In step S2, the dropping rate is 0.05~0.1 mL / min.
7. The method for synthesizing bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphate according to claim 1, characterized in that, In step S3, the molar ratio of BHT to pentaerythritol is (2.0~2.5):
1.
8. The method for synthesizing bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphate according to claim 1, characterized in that, In step S3, the mass ratio of 18-crown ether-6, triphenyl phosphite, and pentaerythritol is (0.001~0.005):(0.0005~0.001):
1.
9. The method for synthesizing bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphate according to claim 1, characterized in that, In step S3, when the temperature is raised to 90~100℃, a composite acid-binding agent needs to be added after the reaction has been going on for 3 hours. The molar ratio of the added composite acid-binding agent to pentaerythritol is 0.8:
1.
10. The method for synthesizing bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphate according to claim 1, characterized in that, In step S3, the mass ratio of the modified active alumina to pentaerythritol is (0.15~0.65):1.