Process for synthesis of flame retardant dithiopyrophosphates by one-pot method with ammonia as acid-binding agent

Abstract

The application discloses a process for synthesizing a flame retardant dithio pyrophosphoric ester by using ammonia as an acid-binding agent in one pot, and uses ammonia and sodium carbonate as the acid-binding agents. In the first step, ammonia is used as the acid-binding agent, which can avoid the problems of low product purity, environmental problems in recycling, high cost and the like caused by the large use of organic alkali, and can also avoid the problem of low yield caused by the use of solid inorganic alkali as the acid-binding agent. In the second step, sodium carbonate is used as the acid-binding agent. The route adopts a green synthesis process of inorganic alkali binding acid in one pot, and the whole route is green, efficient and economical, and has a good industrial application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of flame retardant, and particularly relates to a method for green one-pot synthesis of flame retardant DDPS by using ammonia as an acid-binding agent. BACKGROUND

[0002] Nowadays, polymer materials such as fibers, plastics and rubbers are widely used in industry and people's life, and most of them are flammable in air, and their limiting oxygen index is lower than 21%. In recent years, a considerable part of the fires in various countries is caused by the ignition of polymer materials. Therefore, flame retardants need to be added to improve the flame retardant performance of the materials. Flame retardants are mainly divided into halogen-based, organic phosphorus-based, intumescent and inorganic flame retardants according to the types of flame-retardant elements. Among them, the organic phosphorus-based flame retardant is the most complex and the most fully researched one. The organic phosphorus-based flame retardant has the advantages of low toxicity, low smoke and halogen-free, and meets the development direction of flame retardants, and has a good development prospect.

[0003] Dithiopyrophosphoric acid ester belongs to the organic phosphorus-based halogen-free environmentally friendly flame retardant, and is a classic flame retardant applied to textile fibers. It has the advantages of hydrolysis resistance, acid and alkali stability, good flame retardant performance and the like. The traditional process for synthesizing dithiopyrophosphoric acid ester uses 3.0-6.0 equivalents of acid-binding agents such as triethylamine or pyridine. The addition of a large amount of acid-binding agents will produce a large amount of triethylamine hydrochloride or pyridine hydrochloride wrapped in the product dithiopyrophosphoric acid ester, which affects the purity of the product. Moreover, triethylamine and pyridine are substances with a very strong odor, and pyridine also has a certain toxicity, which has a great impact on the air environment and personnel in the workshop during use and recovery. Therefore, it is necessary to explore a more green and efficient process method for synthesizing dithiopyrophosphoric acid ester.

[0004] The use of ammonia as the acid-binding agent for the first acyl chloride reaction has not been reported in the literature. In the experiment, ammonia gas is used to bind the acid in the first step, which does not need to recover the acid-binding agent compared with the traditional process using organic base, and the by-product ammonium chloride is better separated, and the method is more green and efficient. Compared with the method of adding solid inorganic base to bind the acid, the reaction is more complete and the yield is higher. In the second step, sodium carbonate solution is used as the acid-binding agent instead of triethylamine or pyridine, and the product DDPS can still be obtained efficiently, and the cost is lower and more green and environmentally friendly. In the paper “Synthesis and Application Research of Organic Phosphorus Flame Retardant” by Wang Yang of Dalian University of Technology, a one-pot method for synthesizing DDPS by using triethylamine as the acid-binding agent is proposed. Inspired by the work, a one-pot synthesis process is used in the experiment, and after the first acyl chloride reaction, it is directly put into the second step without any post-treatment, and high yield can be obtained. The process method reported in the application has the advantages of low cost, green environmental protection, high yield and the like, and has a good industrial application prospect. SUMMARY

[0005] The main purpose of the present application is to explore and provide a green and efficient process for synthesizing dithiopyrophosphoric acid ester, which avoids the use of a large amount of triethylamine, pyridine and other organic bases, has lower cost, higher product quality and is more green and environmentally friendly.

[0006] The technical scheme of the present application is as follows:

[0007] An organic phosphorus flame retardant dithiopyrophosphoric acid ester, the chemical structural formula of the compound is:

[0008]

[0009] A one-pot green synthesis process using ammonia and sodium carbonate as an acid binding agent, the method comprising the following steps:

[0010] In the reaction bottle, add neopentyl glycol, then add toluene solvent and heat and stir, slowly add trichlorophosphine several times after the solution is clear, extend the pipe connected with the ammonia gas cylinder below the liquid surface, slowly open the ammonia gas pressure reducing valve, set the ammonia gas flow rate using an ammonia gas micro-flow meter, continuously pass in ammonia gas and stir for a period of time to obtain the intermediate thiophosphoryl chloride. After the first step reaction is completed, set the reaction temperature to the second step reaction temperature, slowly add a certain concentration of sodium carbonate solution, and heat for a period of time, a large amount of white solid is precipitated during the reaction. The DDPS crude product is obtained by suction filtration, the DDPS crude product is first washed with water, then washed with ethanol, filtered and dried to obtain the DDPS product. The reaction formula is as follows:

[0011]

[0012] The molar ratio of neopentyl glycol to trichlorophosphine in the step is 1:0.8-1.2, preferably 1:1.

[0013] The flow rate of ammonia gas in the step is 5-50 mL / min.

[0014] The organic solvent in the step is any one of toluene, benzene, n-heptane and n-hexane.

[0015] The first step reaction temperature in the step is 25-40 DEG C, and the reaction time is 0.5-4 h.

[0016] The molar ratio of the intermediate thiophosphoryl chloride to sodium carbonate in the step is 1:0.5-1.5.

[0017] The second step reaction temperature in the step is 50-70 DEG C, and the reaction time is 6-12 h.

[0018] After the first step reaction is completed, it is directly put into the second step reaction without any post-treatment.

[0019] The mass concentration of ethanol in the ethanol washing is 95% or more.

[0020] The present application has the following advantages:

[0021] 1. The present application discloses a green and efficient method for synthesizing flame retardant dithio pyrophosphates using ammonia as an acid-binding agent. Traditional process methods use a large amount of organic bases such as triethylamine, pyridine, etc. A large amount of organic bases have a great impact on the surrounding environment and personnel during use and recovery, and the cost is relatively high. A large amount of by-products generated affect the purity of dithio pyrophosphate products. In the first step, the acid-binding is carried out by passing in an appropriate amount of dry ammonia, which not only avoids the product quality problems, environmental problems and cost problems caused by the large amount of organic base used, but also solves the problem of insufficient reaction and low reaction yield when using common solid inorganic acid-binding agents. It is a new, green, efficient and economical method.

[0022] 2. The second step of the one-pot synthesis process disclosed in the present application uses sodium carbonate solution as an acid-binding agent, which is an economical and efficient method.

[0023] 3. The one-pot synthesis process adopted in the present application has shorter route time, less three wastes generated, and high yield and high purity of products. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a nuclear magnetic resonance hydrogen spectrum (H NMR) graph of dithio pyrophosphate (DDPS). 1 H NMR).

[0025] Figure 2 It is a nuclear magnetic resonance carbon spectrum (C NMR) graph of dithio pyrophosphate (DDPS). 13 C NMR).

[0026] Figure 3 It is a nuclear magnetic resonance phosphorus spectrum (P NMR) graph of dithio pyrophosphate (DDPS). 31 P NMR). DETAILED DESCRIPTION

[0027] Instruments and reagents:

[0028] Nuclear magnetic resonance spectrum (NMR) was tested by Bruker AVANCE III 400MHz Plus NMR spectrometer, using TMS as internal standard and CDCl3 as solvent. Solvent evaporation was carried out at 60℃ using EYELA SB-1100 rotary evaporator, and other instruments were conventional experimental instruments: SHZ-E circulating water type vacuum pump, DZE-6120 vacuum drying box, EB2005A electronic balance, DFX-5L / 30 low temperature constant temperature reaction bath and 2YZ-4A rotary vane vacuum pump. The reagents used were analytical pure.

[0029] The application will be further described in connection with the following examples without the scope of the application being limited to the scope of the examples.

[0030] Example 1

[0031] A one-pot method for preparing DDPS includes the following experimental steps:

[0032] Take neopentyl glycol 1.041 g (10 mmol) and place it in a 100 mL three-necked flask, add 20 mL of toluene, stir under heating to dissolve it, start to slowly add phosphorus trichloride 1.679 g (10 mmol), stir the reaction at 40°C for 0.5 h, extend the pipe connected to the ammonia gas cylinder below the liquid surface, slowly open the ammonia pressure reducing valve, use the ammonia micro flowmeter to set the ammonia flow rate to 20 mL / min, continue to introduce ammonia under the condition of 40°C for 3 h. After the first step reaction is completed, stop the ammonia introduction, heat to 70°C, take sodium carbonate 1.06 g (10 mmol), add 2.65 g of pure water to prepare a 28% sodium carbonate solution, then slowly add the prepared sodium carbonate solution, after the addition is completed, react at 70°C for 8 h. A large amount of white solid is precipitated during the reaction, after the reaction is completed, filter the solid, then wash the solid with water, ethanol, and dry it to obtain the product DDPS 3.308 g. The yield is 95.6%.

[0033]

[0034] 1 H NMR (400 MHz, CDCl3) δ 4.54 (d, J = 10.3 Hz, 4H), 3.94 (dd, J = 25.2, 11.0 Hz, 4H), 1.32 (s, 6H), 0.91 (s, 6H).

[0035] 13 C NMR (101 MHz, CDCl3) δ 79.06, 79.03, 78.99, 77.32, 77.00, 76.68, 32.15, 32.12, 32.09, 21.81, 19.85.

[0036] 31 P NMR (162 MHz, CDCl3) δ 43.53 (s).

[0037] Example 2

[0038] A one-pot method for preparing DDPS includes the following experimental steps:

[0039] Take neopentyl glycol 52.04 g (0.5 mol) into a 1 L three-necked flask, add 180 mL of toluene, stir under heating to dissolve, then slowly add phosphorus trichloride 83.93 g (0.5 mol), stir at 40°C for 0.5 h, extend the pipe connected to the ammonia gas cylinder below the liquid surface, slowly open the ammonia pressure reducing valve, set the ammonia flow rate to 20 mL / min using the ammonia micro-flow meter, continue to introduce ammonia under the condition of 40°C for 3 h. After the first step reaction is completed, stop the ammonia introduction, heat to 70°C, take sodium carbonate 53.0 g (0.5 mol), add 132.5 g of pure water to prepare a 28% sodium carbonate solution, then slowly add the prepared sodium carbonate solution, after the addition is completed, react at 70°C for 8 h. A large amount of white solid is precipitated during the reaction, after the reaction is completed, the solid is obtained by filtration, then the solid is washed with water, ethanol, and dried to obtain the product DDPS 82.094 g. The yield is 94.9%.

[0040] Example 3

[0041] A one-pot method for preparing DDPS, the base is optimized, including the following experimental steps:

[0042] Take neopentyl glycol 52.04 g (0.5 mol) into a 1 L three-necked flask, add 180 mL of toluene, stir under heating to dissolve, then slowly add phosphorus trichloride 83.93 g (0.5 mol), stir at 40°C for 0.5 h, extend the pipe connected to the ammonia gas cylinder below the liquid surface, slowly open the ammonia pressure reducing valve, set the ammonia flow rate to 20 mL / min using the ammonia micro-flow meter, continue to introduce ammonia under the condition of 40°C for 3 h. After the first step reaction is completed, stop the ammonia introduction, heat to 70°C, take sodium carbonate 53.0 g (0.5 mol), add 132.5 g of pure water to prepare a 28% sodium carbonate solution, then slowly add the prepared sodium carbonate solution, after the addition is completed, react at 70°C for 8 h. A large amount of white solid is precipitated during the reaction, after the reaction is completed, the solid is obtained by filtration, then the solid is washed with water, ethanol, and dried to obtain the product DDPS 82.094 g. The yield is 94.9%.

[0043] Example 4

[0044] A one-pot method for preparing DDPS, the base is optimized, including the following experimental steps:

[0045] Take neopentyl glycol 1.041 g (10 mmol) into a 100 mL three-necked flask, add 20 mL of toluene, stir under heating to dissolve, then add 3.366 g (30 mmol) of potassium tert-butoxide solid, slowly drop 1.679 g (10 mmol) of phosphorus trichloride with a constant pressure funnel, after dropping, keep the reaction at 40°C for 3 h. After the first step reaction is completed, increase the temperature to 70°C, take 1.06 g (10 mmol) of sodium carbonate, add 2.65 g of pure water to prepare a 28% sodium carbonate solution, then slowly drop the prepared sodium carbonate solution, after dropping, react at 70°C for 8 h. A large amount of white solid is precipitated during the reaction, after the reaction is completed, filter the solid, then wash the solid with water, ethanol, and dry to obtain the product DDPS 2.400 g. The yield is 70.6%.

[0046] Example 5

[0047] A one-pot method for preparing DDPS, optimizing the base, including the following experimental steps:

[0048] Take neopentyl glycol 1.041 g (10 mmol) into a 100 mL three-necked flask, add 20 mL of toluene, stir under heating to dissolve, then add 3.366 g (30 mmol) of potassium tert-butoxide solid, slowly drop 1.679 g (10 mmol) of phosphorus trichloride with a constant pressure funnel, after dropping, keep the reaction at 40°C for 3 h. After the first step reaction is completed, increase the temperature to 70°C, take 1.06 g (10 mmol) of sodium carbonate, add 2.65 g of pure water to prepare a 28% sodium carbonate solution, then slowly drop the prepared sodium carbonate solution, after dropping, react at 70°C for 8 h. A large amount of white solid is precipitated during the reaction, after the reaction is completed, filter the solid, then wash the solid with water, ethanol, and dry to obtain the product DDPS 2.400 g. The yield is 70.6%.

[0049] Example 6

[0050] A one-pot method for preparing DDPS, optimizing the solvent, including the following experimental steps:

[0051] Take neopentyl glycol 1.041 g (10 mmol) into a 100 mL three-necked flask, add 20 mL of benzene, stir under heating to dissolve, start to slowly add phosphorus trichloride 1.679 g (10 mmol), 40 ℃ under stirring for 0.5 h, extend the pipe connected to the ammonia gas cylinder below the liquid surface, slowly open the ammonia pressure reducing valve, set the ammonia flow rate to 20 mL / min using the ammonia micro flow meter, continuously introduce ammonia under the condition, 40 ℃ under incubation for 3 h. After the first step reaction is completed, stop the introduction of ammonia, warm up to 70 ℃, take sodium carbonate 1.06 g (10 mmol), add 2.65 g of pure water to prepare a 28% sodium carbonate solution, then slowly add the prepared sodium carbonate solution, after the addition is completed, 70 ℃ for 8 h. A large amount of white solid precipitates during the reaction, after the reaction is completed, filter to obtain a solid, then wash the solid with water, ethanol, and dry to obtain the product DDPS 3.065 g. The yield is 88.6%.

[0052] Example 7

[0053] A one-pot method for preparing DDPS, the solvent is optimized, including the following experimental steps:

[0054] Take neopentyl glycol 1.041 g (10 mmol) into a 100 mL three-necked flask, add 20 mL of benzene, stir under heating to dissolve, start to slowly add phosphorus trichloride 1.679 g (10 mmol), 40 ℃ under stirring for 0.5 h, extend the pipe connected to the ammonia gas cylinder below the liquid surface, slowly open the ammonia pressure reducing valve, set the ammonia flow rate to 20 mL / min using the ammonia micro flow meter, continuously introduce ammonia under the condition, 40 ℃ under incubation for 3 h. After the first step reaction is completed, stop the introduction of ammonia, warm up to 70 ℃, take sodium carbonate 1.06 g (10 mmol), add 2.65 g of pure water to prepare a 28% sodium carbonate solution, then slowly add the prepared sodium carbonate solution, after the addition is completed, 70 ℃ for 8 h. A large amount of white solid precipitates during the reaction, after the reaction is completed, filter to obtain a solid, then wash the solid with water, ethanol, and dry to obtain the product DDPS 3.065 g. The yield is 88.6%.

[0055] Example 8

[0056] A one-pot method for preparing DDPS, the solvent is optimized, including the following experimental steps:

[0057] Take neopentyl glycol 1.041 g (10 mmol) into a 100 mL three-necked flask, add 20 mL of n-hexane, stir under heating to dissolve, start to slowly add phosphorus trichloride 1.679 g (10 mmol), stir at 40℃ for 0.5 h, extend the pipe connected to the ammonia gas cylinder below the liquid surface, slowly open the ammonia pressure reducing valve, set the ammonia flow rate to 20 mL / min using the ammonia micro flow meter, continuously introduce ammonia under the condition, keep at 40℃ for 3 h. After the first step reaction is completed, stop the introduction of ammonia, warm up to 70℃, take sodium carbonate 1.06 g (10 mmol), add 2.65 g of pure water to prepare a 28% sodium carbonate solution, then slowly add the prepared sodium carbonate solution, after the addition is completed, react at 70℃ for 8 h. A large amount of white solid is precipitated during the reaction, after the reaction is completed, filter the solid, then wash the solid with water, ethanol, and dry, to obtain the product DDPS 2.886 g. The yield is 83.4%.

[0058] Example 9

[0059] A one-pot method for preparing DDPS, the solvent is optimized, including the following experimental steps:

[0060] Take neopentyl glycol 1.041 g (10 mmol) into a 100 mL three-necked flask, add 20 mL of n-hexane, stir under heating to dissolve, start to slowly add phosphorus trichloride 1.679 g (10 mmol), stir at 40℃ for 0.5 h, extend the pipe connected to the ammonia gas cylinder below the liquid surface, slowly open the ammonia pressure reducing valve, set the ammonia flow rate to 20 mL / min using the ammonia micro flow meter, continuously introduce ammonia under the condition, keep at 40℃ for 3 h. After the first step reaction is completed, stop the introduction of ammonia, warm up to 70℃, take sodium carbonate 1.06 g (10 mmol), add 2.65 g of pure water to prepare a 28% sodium carbonate solution, then slowly add the prepared sodium carbonate solution, after the addition is completed, react at 70℃ for 8 h. A large amount of white solid is precipitated during the reaction, after the reaction is completed, filter the solid, then wash the solid with water, ethanol, and dry, to obtain the product DDPS 2.886 g. The yield is 83.4%.

[0061] Example 10

[0062] A one-pot method for preparing DDPS, the solvent is optimized, including the following experimental steps:

[0063] Take neopentyl glycol 1.041 g (10 mmol) into a 100 mL three-necked flask, add 20 mL of butyl acetate, stir under heating to dissolve, start to slowly add phosphorus trichloride 1.679 g (10 mmol), stir the reaction at 40℃ for 0.5 h, extend the pipe connected with ammonia gas cylinder below the liquid surface, slowly open the ammonia gas pressure reducing valve, set the ammonia gas flow rate to 20 mL / min using the ammonia gas micro flow meter, continuously introduce ammonia gas under the condition of 40℃ for 3 h. After the first step reaction is completed, stop the introduction of ammonia gas, and warm up to 70℃, take sodium carbonate 1.06 g (10 mmol), add 2.65 g of pure water to prepare a 28% sodium carbonate solution, then slowly add the prepared sodium carbonate solution, after the dropwise addition is completed, react at 70℃ for 8 h. A large amount of white solid is precipitated during the reaction, after the reaction is completed, filter the solid, then wash the solid with water, ethanol, and dry to obtain the product DDPS 1.880 g. The yield is 55.3%.

[0064] The application provides a method for synthesizing flame retardant dithiopyrophosphoric acid ester by using ammonia gas and sodium carbonate as acid binding agents, which avoids product quality problems, environmental problems, cost problems and the like caused by the large use of organic bases. In the first step reaction, ammonia gas is used as an acid binding agent, which is more efficient than the use of solid inorganic bases, and has a higher yield. The one-pot synthesis has a shorter reaction time and generates less waste. The whole route avoids the use of organic bases as acid binding agents, uses ammonia gas and sodium carbonate as acid binding agents, and uses a one-pot synthesis process, and the whole route is green, efficient and economical, and has a good industrial application prospect.

[0065] The above examples are only preferred technical solutions of the application, and should not be regarded as limitations of the application. The examples in the application and the features in the examples can be combined with each other as long as they do not conflict. The protection scope of the application should be based on the technical solutions recited in the claims, including equivalent replacement solutions of the technical features recited in the claims. That is, equivalent replacement improvements within this range are also within the protection scope of the application.

Claims

1. A process for synthesizing flame retardant dithiophosphate in a one-pot method using ammonia as an acid-binding agent, characterized in that, Includes the following steps: (1) Weigh the raw material neopentyl glycol into the reactor, add organic solvent, heat and stir until neopentyl glycol dissolves, then add trichlorophosphorus dropwise. After the addition is complete, ammonia gas is introduced to keep the reaction at a constant temperature. After the reaction is complete, the intermediate thiophosphoric chloride is obtained. The organic solvent is selected from any one of toluene, benzene, n-heptane, and n-hexane. (2) After the intermediate thiophosphoryl chloride is heated again, sodium carbonate solution is added dropwise. After the addition is complete, the reaction is maintained at the temperature. After the reaction is complete, the crude product is obtained by suction filtration. Then, the crude product is washed with water and ethanol, filtered, and dried to obtain the dithiopyrophosphate product. The reaction formula is as follows: 。 2. The process according to claim 1, characterized in that, The molar ratio of neopentyl glycol to trichlorfon is 1:0.8-1.

2.

3. The process according to claim 2, characterized in that, The molar ratio of neopentyl glycol to trichlorfon is 1:

1.

4. The process according to claim 1, characterized in that, The reaction temperature in step (1) is 25℃-40℃, and the reaction time is 0.5 h-4 h.

5. The process according to claim 1, characterized in that, In step (1), the flow rate of ammonia gas is 5-50 mL / min.

6. The process according to claim 1, characterized in that, The molar ratio of intermediate thiophosphoryl chloride to sodium carbonate is 1:0.5-1.

5.

7. The process according to claim 1, characterized in that, The reaction temperature in step (2) is 50℃-70℃, and the reaction time is 6 h-12 h.

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