A method for synthesizing bisphenol A-bis(diphenyl phosphate)

Abstract

The invention discloses a method for synthesizing bisphenol A-bis(diphenyl phosphate), which belongs to the technical field of organic synthesis. The invention uses phosphorus oxychloride, phenol and methanol as raw materials to first obtain methyl diphenyl phosphate; the obtained methyl diphenyl phosphate reacts with bisphenol A to obtain bisphenol A bis(diphenyl phosphate); the synthetic route of the invention avoids the recovery of excessive phosphorus oxychloride and high reaction temperature in the existing process, and hydrogen chloride can be recovered at one time, avoiding the recovery of hydrogen chloride twice in the existing process; the whole process is simple to operate, the material is easy to obtain, the cost is low, the yield is high, and it is suitable for industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic synthesis, and particularly relates to a method for synthesizing bisphenol A-bis(diphenyl phosphate). Background Art

[0002] In the development process of phosphate flame retardants as halogen-free flame retardants, triphenyl phosphate (TPP) and the like are products of the first-generation mainstream phosphate ester series, mainly used for modified PPO plastics, PC, ABS alloys, etc. used for packaging in office automation machines. However, due to the volatility of TPP, it can cause metal contamination in plastics with higher forming temperatures such as engineering plastics, which may deteriorate the working environment. Therefore, in order to meet the market requirements for the hydrolysis resistance of flame retardants, the second-generation phosphate ester-based flame retardant - tetraphenyl (bisphenol A) diphosphate (BDP) came into being;

[0003] Bisphenol A bis(diphenylphosphate) (abbreviated as BDP) is an important type of phosphorus-based flame retardant. It has a large molecular weight, high thermal stability, low volatility, high flame retardancy efficiency, and a phosphorus content as high as 9%, with a long-lasting flame retardant effect. Its plasticizing property, flame retardancy, and thermal stability are all superior to ordinary phosphate esters such as TPP. BDP is a representative of the new generation of flame retardants that have emerged internationally. As an additive flame retardant for polymers, with its unique chemical composition and mechanical properties, it shows good stability and extraordinary flame retardant performance in polymer materials, and has received extensive attention and widespread application. It is suitable for the production of flame-retardant PC / ABS alloys, flame-retardant HIPS / PPO alloys, and flame-retardant PC. BDP is also widely used in high-molecular materials such as flame-retardant PVC, cellulose resins, synthetic rubbers, phenolic resins, epoxy resins, polyester fibers, polystyrene, polycarbonates, polyurethane foam products, and epoxy resins, etc., and has a broad application field.

[0004] At present, the research on BDP abroad is mainly patent reports. Among them, AkzoNobel, Albemarle, Great Lakes, and Food Machinery and Chemical Corporation (FMC) in the United States have applied for several patents on BDP in the United States, the United Kingdom, and the World Intellectual Property Organization respectively. The content includes two aspects: the production method of BDP and the improvement of production technology. The patents mainly discuss the effects of raw material ratio, catalyst selection, reaction time, and reaction temperature on the product yield; the deterioration of product performance by impurities such as triphenyl phosphate and isopropenylphenyl diphenyl phosphate, and product purification. In the patent content applied by Albemarle in the United States, BDP is a liquid at room temperature and will not crystallize after a period of time. The product mainly contains tetraphenyl (bisphenol A) diphosphate, its dimer, and a small amount of trimer. It is detected by high performance liquid chromatography (HPLC) that the area of BDP monomer is 78-87% and about 85-90% of the normalized area %, where the normalized area is based on the total HPLC area % of tetraphenyl (bisphenol A) diphosphate and its dimer; the two-step method is adopted in the preparation method of BDP in the patent. The first step includes preparing an intermediate by adding bisphenol A to phosphorus oxychloride in excess for a period of time. The reaction temperature ranges from 85 to 106 °C to ensure the rapid progress of the reaction. The reaction time can be 3 to 6 h, usually 4 to 5 h. The ratio of phosphorus oxychloride to bisphenol A is between 3.5 and 4.5:1, and magnesium chloride is preferably used as the catalyst. The amount used in the first step is usually 0.01 to 4.0% (by weight) of the amount of bisphenol A added; the second step is a capping reaction with phenol. The temperature when adding phenol in the second step reaction is controlled at 130 to 160 °C, and then the temperature is controlled at 130 to 180 °C until the reaction ends. The ratio of bisphenol A to phenol is preferably 1:3.9 to 4.0. If the catalyst is the same as the one used in the first step, the initially provided catalyst continues to be retained in the reactants and is sufficient for the second step. If different, based on the bisphenol A added to the reactants, about 0.8% (by weight) of the catalyst, mainly metal halide salts such as aluminum chloride and calcium chloride, is added.

[0005] Based on the patents and research progress at home and abroad, there are mainly three synthesis methods of BDP at present:

[0006] Route 1: Phosphorus oxychloride and bisphenol A react under the action of magnesium chloride catalyst to obtain bisphenol A tetrachloro diphosphate. After recovering the excess amount of phosphorus oxychloride, it is then subjected to a capping reaction with phenol to obtain the target product.

[0007] Route 2: Phosphorus oxychloride and phenol react to obtain diphenyl phosphoryl chloride, and then react with bisphenol A to obtain the target product.

[0008] Route 3: Phosphorus oxychloride and bisphenol A react under the action of a catalyst to obtain bisphenol A tetrachlorobisphosphate, which is then capped with sodium phenolate to obtain the target product.

[0009] Route 1 is a reaction between a difunctional group and a trifunctional group, which inevitably generates oligomers, mainly dimers and a small amount of trimers. The disadvantage of this route is that phosphorus oxychloride is excessive and must be recovered after the reaction is completed. The hydrogen chloride produced in each step must be recovered twice. This route requires a large number of corrosion-resistant equipment. In addition, if phosphorus oxychloride is not completely recovered, the next step reaction cannot avoid the production of triphenyl phosphate (TPP) impurities. Route 2 is a reaction between a difunctional compound and a monofunctional group, and the intermediate obtained has active groups and poor chemical stability. Sodium phenolate used in route 3 is expensive in the market and is easily affected by moisture. In production, when the damp sodium phenolate reacts with the intermediate containing active chlorine, it cannot be avoided that it is partially hydrolyzed to produce impurities, which also increases the production cost and produces sodium chloride solid waste. This synthetic route refers to route 2, uses different hydroxyl compounds to synthesize triester compounds, and finally undergoes ester exchange with bisphenol A to obtain the target compound. This route overcomes the cumbersome process of recovering hydrogen chloride twice in route one and recovering excess phosphorus oxychloride, and also avoids the problem of sodium chloride solid waste produced in route three. At the same time, it solves the defect of poor chemical stability of the intermediates in the above route, providing a valuable reference for industrial production and process improvement. Summary of the invention

[0010] In order to solve the above problems, the present invention discloses a method for preparing bisphenol A-bis(diphenyl phosphate), wherein phosphorus oxychloride is firstly reacted with phenol and then with methanol in the first step, and hydrogen chloride is completely recovered in one step in the first step, thereby optimizing the process of recovering hydrogen chloride, and the intermediate obtained in the first step is used to carry out ester exchange with bisphenol A in the second step; in the process, the intermediate generated in the first step is relatively stable to protic solvents, thereby changing the sensitivity of the chlorine-containing intermediate in the currently reported process route to protic solvents and water, and reducing the high-temperature energy consumption of the currently reported industrial route.

[0011] To achieve the above object, the technical solution of the present invention is as follows:

[0012] A method for preparing bisphenol A-bis(diphenyl phosphate), the synthetic process route is:

[0013] .

[0014] The specific steps include:

[0015] S01: Continuously add phenol to a mixed solution of phosphorus oxychloride and a catalyst at -10 to 20 °C, and react for 3 to 6 hours at a temperature below 90 °C; add methanol and continue the reaction to produce methyl diphenyl phosphate, and react for 2 to 3 hours at a temperature below 80 to 120 °C; the catalyst is triethylamine or 4-dimethylaminopyridine;

[0016] S02: React the methyl diphenyl phosphate obtained in S01 with bisphenol A under the condition of a catalyst for 3 to 8 hours to obtain bisphenol A-bis-(diphenyl phosphate); the catalyst is one of an acidic catalyst, a basic catalyst, and a metal catalyst.

[0017] Furthermore, in step S01, the molar ratio of phosphorus oxychloride, phenol, and methanol is 1: 1.9 to 2.1: 1.0 to 1.2.

[0018] Furthermore, in step S01, the dosage of the catalyst is 0.1 to 5% of the mass of phosphorus trichloride; the volume ratio of the solvent to phosphorus oxychloride is 3 to 6: 1;

[0019] Furthermore, in step S01, the solvent is an aromatic hydrocarbon solvent, and preferably the solvent is one or more of toluene, xylene, chlorobenzene, and mesitylene.

[0020] Furthermore, in step S01, after adding phenol, slowly raise the temperature to 60 to 90 °C.

[0021] Furthermore, in step S02, the molar ratio of methyl diphenyl phosphate to bisphenol A is 2: 0.9 to 1.2.

[0022] Furthermore, in step S02, the acidic catalyst includes acidic resin NKC-9, Amberlyst15, and sulfuric acid; the metal catalyst includes zinc salts of organic acids, organic titanates, and acetylacetone + calcium chloride; the basic catalyst includes sodium methoxide, sodium ethoxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, and 4-dimethylaminopyridine.

[0023] Furthermore, in step S02, the dosage of the acidic catalyst is 5 to 10% of the mass of methyl diphenyl phosphate, the dosage of the metal catalyst is 0.1 to 10% of the mass of methyl diphenyl phosphate, and the dosage of the basic catalyst is 0.1 to 10% of the mass of methyl diphenyl phosphate.

[0024] When using an acidic catalyst, the acidic catalyst first protonates the phosphorus-oxygen double bond to make phosphorus more positively charged, and then undergoes an electrophilic reaction with bisphenol A; when using a basic catalyst, since the hydroxyl group of bisphenol A is slightly acidic, the hydroxyl group of bisphenol A forms an oxygen anion with the base, and the oxygen anion undergoes a nucleophilic reaction with phosphorus; when using a metal catalyst, the oxygen of the phosphorus-oxygen double bond forms a complex with the metal ion to activate the phosphorus-oxygen double bond, and then bisphenol A attacks the phosphorus atom to carry out the reaction.

[0025] Further, in step S02, the solvent is an aprotic solvent. Preferably, the solvent is one or more of dioxane, toluene, xylene, chlorobenzene, and mesitylene.

[0026] Further, in step S02, the reaction temperature is 50°C to 120°C, and the reaction time is 3 to 8 hours. Preferably, in step S02, under the action of a catalyst, the reaction temperature of methyl diphenyl phosphate and bisphenol A is 70 to 90°C, and the reaction time is 5 to 6 hours.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] In the first step of the present invention, phosphorus oxychloride first reacts with phenol and then with methanol, and hydrogen chloride is completely recovered at one time in the first step, optimizing the process of hydrogen chloride. In the second step, transesterification is carried out with bisphenol A. The intermediate generated in this process is relatively stable to protic solvents, changing the sensitivity of the chlorine-containing intermediate in the existing reported process route to protic solvents and water, and reducing the high-temperature energy consumption of the existing industrial route in the existing report.

[0029] The present invention overcomes the cumbersome process of recovering hydrogen chloride and the excessive phosphorus oxychloride in the prior art, also avoids the problem of sodium chloride solid waste reported in the prior art, and at the same time solves the defect of poor chemical stability of the intermediate in the prior art, providing a valuable reference for industrial production and process improvement.

[0030] The present invention uses a catalyst with high yield, low reaction temperature, and less three wastes. Description of the Drawings

[0031] Figure 1 is the 1 HNMR spectrum of the synthesis of methyl diphenyl phosphate in Example 1 of the present invention;

[0032] Figure 2 is the liquid phase spectrum of the synthesis of methyl diphenyl phosphate in Example 1 of the present invention;

[0033] Figure 3 is the liquid phase spectrum of the flame retardant BDP in Example 1 of the present invention;

[0034] Figure 4 is the liquid phase spectrum of the flame retardant BDP in Example 2 of the present invention;

[0035] Figure 5 is the liquid phase spectrum of the flame retardant BDP in Example 3 of the present invention;

[0036] Figure 6 is the liquid phase spectrum of the flame retardant BDP in Example 4 of the present invention. Detailed Embodiments

[0037] The present invention will be further illustrated below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0038] Example 1

[0039] Under nitrogen conditions, 278 mL of toluene and 153 g of phosphorus oxychloride were added into a 2000 mL reaction flask, 2 mL of triethylamine was added, 178.5 g of phenol was added at 0 - 10°C, and the reaction was kept warm for 2 hours. Then the temperature was raised to 80 - 90°C and kept warm for 3 hours; after adding 35.2 g of methanol, the temperature was raised to 90°C and kept warm for 3 hours; then dry nitrogen was introduced into the reaction flask for bubbling for 1 hour; toluene was recovered under reduced pressure, and 238 g of crude methyl diphenyl phosphate with a purity of 98% and a yield of 90% was obtained; see Figure 1 HNMR spectrum of methyl diphenyl phosphate 1 see Figure 2 Liquid phase spectrum of methyl diphenyl phosphate.

[0040] Under nitrogen conditions, 231.5 g (876.17 mmol) of methyl diphenyl phosphate, 500 mL of toluene, 18 g of Amberlyst15 and 90 g (394.28 mmol) of bisphenol A were added into a 1000 mL flask, and the reaction was carried out at 90 - 100°C under slightly negative pressure for 5 - 6 hours. Then the catalyst was recovered by filtration, the temperature was lowered to 20 - 25°C, 200 mL of methylcyclopentane was added, and the reaction solution was washed with an appropriate amount of water 2 - 3 times. The organic phase was concentrated under reduced pressure to obtain 273 g of the product with a yield of 90%. Liquid phase detection: see Figure 3.

[0041] Example 2

[0042] Under nitrogen conditions, 655 mL of xylene and 180 g of phosphorus oxychloride were added into a 2000 mL reaction flask, 2.5 g of DMAP was added, 232 g of phenol was added at 0 - 10°C. After addition, the reaction was kept warm for 2 hours, then the temperature was raised to 80 - 90°C and kept warm for 3 hours; then 45.1 g of methanol was added, and then the temperature was raised to 80 - 90°C and kept warm for 3 hours. Then dry nitrogen was introduced into the reaction flask for bubbling for 1 hour, and xylene was recovered under reduced pressure to obtain 288 g of methyl diphenyl phosphate product with a yield of 93% and a purity of 97.8%;

[0043] Under nitrogen atmosphere, 116 g (439.03 mmol) of methyl diphenyl phosphate, 300 mL of toluene, 1.0 g of sodium methoxide and 45.1 g (197.57 mmol) of bisphenol A were added into a 1000 mL flask. The mixture was heated to 90 - 100 °C and reacted under slightly negative pressure for 3 - 3.5 hours. Then it was cooled to 20 - 25 °C, 450 mL of methylcyclopentane was added, and the reaction solution was washed with an appropriate amount of water for 2 - 3 times. The organic phase was concentrated under reduced pressure to obtain 141 g of crude product, with a yield of 93%. Liquid phase detection: see Spectrum 4.

[0044] Example 3

[0045] 200 g (1300 mmol) of phosphorus oxychloride, 245.5 g (2610 mmol) of phenol, 41.8 g (1300 mmol) of methanol and 546 mL of toluene were charged according to Example 1 to synthesize methyl diphenyl phosphate, obtaining 306 g of methyl diphenyl phosphate, with a yield of 89% and a purity of 98.5%.

[0046] Under nitrogen atmosphere, 200 g (756.95 mmol) of methyl diphenyl phosphate, 450 mL of toluene, 3 g of tetramethylammonium hydroxide and 103 g (451.18 mmol) of bisphenol A were added into a 1000 mL flask. The mixture was heated to 90 - 100 °C and reacted under slightly negative pressure for 4 - 4.5 hours. Then it was cooled to 20 - 25 °C, 450 mL of methylcyclopentane was added, and the reaction solution was washed with an appropriate amount of water for 2 - 3 times. The organic phase was concentrated under reduced pressure to obtain 242 g of crude product, with a yield of 89%. Liquid phase detection: see Spectrum 5.

[0047] Example 4

[0048] 305 g of methyl diphenyl phosphate with a purity of 98.1% was synthesized according to Example 3.

[0049] Under nitrogen atmosphere, 210 g (794.8 mmol) of methyl diphenyl phosphate, 460 mL of dioxane, 6 g of tetrabutyl titanate and 91 g (398.61 mmol) of bisphenol A were added into a 1000 mL flask. The mixture was heated to 90 - 100 °C and reacted under slightly negative pressure for 4 - 4.5 hours. Then it was cooled to 20 - 25 °C, 450 mL of methylcyclopentane was added, and the reaction solution was washed with an appropriate amount of water for 2 - 3 times. The organic phase was concentrated under reduced pressure to obtain 236 g of crude product, with a yield of 86.6%. Liquid phase detection: see Spectrum 6.

[0050] It should be noted that the above content only illustrates the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. For those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements all fall within the protection scope of the claims of the present invention.

Claims

1. A method for synthesizing bisphenol A bis(diphenyl phosphate), characterized in that, It includes the following steps: S01: At -10 to 120 °C, add phosphorus oxychloride and a catalyst into a solvent, then add phenol, and then add methanol, and react to generate methyl diphenyl phosphate; the catalyst is triethylamine or 4-dimethylaminopyridine; ； S02: React the methyl diphenyl phosphate obtained in S01 with bisphenol A under the condition of a catalyst to obtain bisphenol A-bis-(diphenyl phosphate); the catalyst is one of an acidic catalyst and a metal catalyst, the acidic catalyst is Amberlyst15, and the metal catalyst is tetrabutyl titanate; the dosage of the acidic catalyst is 5 to 10% of the mass of methyl diphenyl phosphate, and the dosage of the metal catalyst is 0.1 to 10% of the mass of methyl diphenyl phosphate; ； ； In step S01, after adding phenol, heat up to 60 - 90 °C and react for 3 to 6 hours; after adding methanol, heat up to 80 - 120 °C and react for 2 to 3 hours.

2. The synthesis method of bisphenol A bis(diphenyl phosphate) according to claim 1, characterized in that, In step S01, the molar ratio of phosphorus oxychloride, phenol, and methanol is 1:1.9 - 2.1:1.0 - 1.

2.

3. A method for synthesizing bisphenol A bis(diphenyl phosphate) according to claim 1, characterized in that, In step S01, the dosage of the catalyst is 0.1 to 5% of the mass of phosphorus oxychloride; the volume ratio of the solvent to phosphorus oxychloride is 3 - 6:

1.

4. A method for synthesizing bisphenol A bis(diphenyl phosphate) according to claim 1, characterized in that, In step S01, the solvent is one or more of dioxane, toluene, xylene, chlorobenzene, and mesitylene.

5. A method for synthesizing bisphenol A bis(diphenyl phosphate) according to claim 1, characterized in that, In step S02, the molar ratio of methyl diphenyl phosphate to bisphenol A is 2:0.9 - 1.

2.

6. A method for synthesizing bisphenol A bis(diphenyl phosphate) according to claim 1, characterized in that, In step S02, a solvent is also added, and the solvent is one or more of dioxane, toluene, xylene, chlorobenzene, and mesitylene.

7. A method for synthesizing bisphenol A bis(diphenyl phosphate) according to claim 1, characterized in that, In step S02, the reaction temperature is 50 °C to 120 °C, and the reaction time is 3 to 8 hours.

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