A kind of preparation method of aluminum diethylphosphonate

Abstract

The present invention belongs to the technical field of fine chemical production, and specifically relates to a method for preparing aluminum diethylphosphonate. The preparation method provided by the present invention comprises: mixing an alkali metal hypophosphite, a free radical initiator, and water, and then first conducting an ethylation reaction under relatively high temperature and pressure conditions, so that the alkali metal hypophosphite reacts with ethylene to form a transition intermediate; then lowering the temperature and pressure to continue the ethylation reaction to ensure sufficient formation of the transition intermediate; and finally lowering the temperature and pressure again to conduct the ethylation reaction, thereby significantly reducing impurities in the aqueous solution of the alkali metal butylethyl hypophosphite. Thus, the mass percentage of butylethyl aluminum phosphinate in the resulting aluminum diethylphosphonate is ≤1%, and the purity is high.

Description

Technical Field

[0001] The invention belongs to the technical field of fine chemical production, and particularly relates to a method for preparing diethyl aluminum phosphonate. Background Art

[0002] Aluminum diethylphosphinate is a compound with the molecular formula Al(PO2C4H 10 )3, CAS number 225789-38-8, molar mass 390.3g / mol, structural formula shown in Formula 1. The product is a white powdery solid suitable for flame retardant modification of high-temperature nylon (including glass fiber reinforced and non-reinforced). The flame-retardant modified material exhibits good physical and electrical properties. At the same time, aluminum diethylphosphinate can be used in combination with nitrogen-containing flame retardants for the flame retardancy of PA6 and PA66 (including glass fiber reinforced and non-reinforced), and the finished product can achieve UL94V-0 (0.4mm) flame retardancy.

[0003]

[0004] Chinese patent CN1660858A discloses a method for preparing dimethylphosphinate, and an example thereof discloses a method for preparing aluminum diethylphosphinate. The method involves introducing ethylene into an autoclave at a pressure of 0.6 MPa, reacting at a temperature of 110-110°C for 6 hours, and then forming a salt. While the preparation steps are simple, the resulting product contains approximately 2% aluminum butylethylphosphinate and has a high impurity content. This high impurity content can affect the quality of the end product when aluminum diethylphosphinate is used as a flame retardant additive. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing diethyl aluminum phosphonate. The method provided by the present invention can prepare high-purity diethyl aluminum phosphonate, and the preparation method is simple and suitable for industrial production.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing diethyl aluminum phosphonate, comprising the following steps:

[0008] An alkali metal hypophosphite, a free radical initiator and water are mixed and subjected to a first-stage ethylation reaction in an ethylene atmosphere to obtain a first transition state system; the first transition state system is cooled and depressurized before a second-stage ethylation reaction is carried out to obtain a second transition state system; the second transition state system is cooled and depressurized before a third-stage ethylation reaction is carried out to obtain an aqueous solution of an alkali metal diethyl phosphate; the temperature of the first-stage ethylation reaction is ≥120° C., the pressure of the first-stage ethylation reaction is ≥1 MPa, the absolute value of the difference between the temperature of the first-stage ethylation reaction and the second-stage ethylation reaction is ≤20° C., the absolute value of the difference between the temperature of the second-stage ethylation reaction and the third-stage ethylation reaction is ≤20° C., the absolute value of the difference between the pressure of the first-stage ethylation reaction and the second-stage ethylation reaction is ≤0.3 MPa, and the absolute value of the difference between the pressure of the second-stage ethylation reaction and the third-stage ethylation reaction is ≤0.2 MPa;

[0009] The aqueous solution of the diethyl phosphate alkali metal salt and a water-soluble aluminum salt are mixed to carry out a precipitation reaction, and the diethyl aluminum phosphite is obtained by solid-liquid separation; the mass percentage of butyl ethyl phosphinate aluminum in the diethyl aluminum phosphite is ≤1%.

[0010] Preferably, the temperature of the first-stage ethylation reaction is 120-130° C., and the pressure of the first-stage ethylation reaction is 1-1.2 MPa.

[0011] Preferably, the temperature of the second-stage ethylation reaction is 110-120° C., and the pressure of the second-stage ethylation reaction is 0.9-1 MPa.

[0012] Preferably, the temperature of the third stage ethylation reaction is 100-110° C., and the pressure of the third stage ethylation reaction is 0.8-0.9 MPa.

[0013] Preferably, the total heat preservation and pressure holding time of the first stage ethylation reaction, the second stage ethylation reaction and the third stage ethylation reaction is 5 to 10 hours.

[0014] Preferably, the ratio of the heat preservation and pressure holding time of the first stage ethylation reaction, the second stage ethylation reaction and the third stage ethylation reaction is 3:3:(2-3).

[0015] Preferably, the molar ratio of the alkali metal hypophosphite to the ethylene is 1:(2-5);

[0016] The free radical initiator is one or more of ammonium persulfate, sodium persulfate, hydrogen peroxide, performic acid and peracetic acid; the molar ratio of the alkali metal hypophosphite to the free radical initiator is preferably (50-100):1.

[0017] Preferably, the water-soluble aluminum salt is aluminum sulfate;

[0018] The molar ratio of the water-soluble aluminum salt to the diethyl phosphate alkali metal salt is (1.1-1.2):6.

[0019] Preferably, the temperature of the precipitation reaction is 50-100° C., and the pH value of the precipitation reaction is 2-6.

[0020] The invention provides a preparation method of aluminum diethylphosphonate, comprising the following steps: mixing an alkali metal hypophosphite, a free radical initiator and water, performing a first-stage ethylation reaction in an ethylene atmosphere to obtain a first transition state system, cooling and depressurizing the first transition state system and then performing a second-stage ethylation reaction to obtain a second transition state system, cooling and depressurizing the second transition state system and then performing a third-stage ethylation reaction to obtain an aqueous solution of the alkali metal diethylphosphonate; the temperature of the first-stage ethylation reaction is ≥120°C, the pressure of the first-stage ethylation reaction is ≥1MPa, and the first-stage ethylation reaction and the second-stage ethylation reaction are respectively ≥1MPa and ≥1MPa. The absolute value of the temperature difference between the first and second stage ethylation reactions is ≤20°C, the absolute value of the temperature difference between the second and third stage ethylation reactions is ≤20°C, the absolute value of the pressure difference between the first and second stage ethylation reactions is ≤0.3MPa, and the absolute value of the pressure difference between the second and third stage ethylation reactions is ≤0.2MPa; the aqueous solution of the diethyl phosphate alkali metal salt and a water-soluble aluminum salt are mixed to perform a precipitation reaction, and the diethyl aluminum phosphate is obtained by solid-liquid separation; the mass percentage of butylethyl aluminum phosphinate in the diethyl aluminum phosphate is ≤1%. The preparation method provided by the present invention adopts a staged approach to carry out a free radical ethylation reaction. First, the ethylation reaction is carried out under relatively high temperature and pressure conditions, so that an alkali metal hypophosphite reacts with ethylene to generate a transition intermediate. Then, the temperature and pressure are lowered and the ethylation reaction is continued to ensure that the transition intermediate is fully generated. Finally, the temperature and pressure are lowered again to carry out the ethylation reaction, so that the impurity components in the aqueous solution of the butyl ethyl hypophosphite alkali metal salt are greatly reduced. Therefore, the mass percentage of butyl ethyl phosphinate in the finally obtained aluminum diethyl phosphite is ≤1%, and the purity is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Flow chart of the ethylation reaction in the embodiment of the present invention;

[0022] Figure 2 This is a flow chart of the precipitation reaction in an embodiment of the present invention;

[0023] Figure 3 The product prepared in Example 3 of the present invention was tested for purity using nuclear magnetic phosphorus spectrum analysis:

[0024] Figure 4 The product prepared in comparative example 3 of the present invention was tested for purity using nuclear magnetic phosphorus spectrum analysis. DETAILED DESCRIPTION

[0025] The present invention provides a method for preparing diethyl aluminum phosphonate, comprising the following steps:

[0026] An alkali metal hypophosphite, a free radical initiator and water are mixed and subjected to a first-stage ethylation reaction in an ethylene atmosphere to obtain a first transition state system; the first transition state system is cooled and depressurized before a second-stage ethylation reaction is carried out to obtain a second transition state system; the second transition state system is cooled and depressurized before a third-stage ethylation reaction is carried out to obtain an aqueous solution of an alkali metal diethyl phosphate; the temperature of the first-stage ethylation reaction is ≥120° C., the pressure of the first-stage ethylation reaction is ≥1 MPa, the absolute value of the difference between the temperature of the first-stage ethylation reaction and the second-stage ethylation reaction is ≤20° C., the absolute value of the difference between the temperature of the second-stage ethylation reaction and the third-stage ethylation reaction is ≤20° C., the absolute value of the difference between the pressure of the first-stage ethylation reaction and the second-stage ethylation reaction is ≤0.3 MPa, and the absolute value of the difference between the pressure of the second-stage ethylation reaction and the third-stage ethylation reaction is ≤0.2 MPa;

[0027] The aqueous solution of the diethyl phosphate alkali metal salt and a water-soluble aluminum salt are mixed to carry out a precipitation reaction, and the diethyl aluminum phosphite is obtained by solid-liquid separation; the mass percentage of butyl ethyl phosphinate aluminum in the diethyl aluminum phosphite is ≤1%.

[0028] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well known to those skilled in the art.

[0029] The present invention comprises mixing an alkali metal hypophosphite, a free radical initiator and water, performing a first-stage ethylation reaction in an ethylene atmosphere to obtain a first transition state system, cooling and depressurizing the first transition state system, performing a second-stage ethylation reaction to obtain a second transition state system, cooling and depressurizing the second transition state system, performing a third-stage ethylation reaction to obtain an aqueous solution of an alkali metal diethyl phosphate. The temperature of the first-stage ethylation reaction is ≥120°C, the pressure of the first-stage ethylation reaction is ≥1MPa, the absolute value of the temperature difference between the first-stage ethylation reaction and the second-stage ethylation reaction is ≤20°C, the absolute value of the temperature difference between the second-stage ethylation reaction and the third-stage ethylation reaction is ≤20°C, the absolute value of the pressure difference between the first-stage ethylation reaction and the second-stage ethylation reaction is ≤0.3MPa, and the absolute value of the pressure difference between the second-stage ethylation reaction and the third-stage ethylation reaction is ≤0.2MPa.

[0030] In the present invention, the alkali metal hypophosphite is preferably sodium hypophosphite, and more preferably sodium hypophosphite monohydrate.

[0031] In the present invention, the free radical initiator is preferably one or more of ammonium persulfate, sodium persulfate, hydrogen peroxide, performic acid and peracetic acid, and more preferably ammonium persulfate.

[0032] In the present invention, the molar ratio of the alkali metal hypophosphite to the free radical initiator is preferably (5-100):1; more preferably (5-10):1 or (50-100):1, further preferably (5-10):1 or (50-70):1.

[0033] In the present invention, the molar ratio of the alkali metal hypophosphite to the ethylene is 1:(2-5).

[0034] The present invention has no special requirements on the amount of water used, as long as the ethylation reaction is ensured to proceed smoothly.

[0035] In the present invention, the step of mixing the alkali metal hypophosphite, the free radical initiator, and water preferably comprises: dissolving the alkali metal hypophosphite in a portion of the water to obtain an alkali metal hypophosphite aqueous solution; dissolving the free radical initiator in the remaining water to obtain an aqueous solution of the free radical initiator; and heating the alkali metal hypophosphite aqueous solution to the holding temperature for the first-stage ethylation reaction, and then mixing the aqueous solution of the free radical initiator. In the present invention, the mass percentage of the aqueous solution of the free radical initiator is preferably 1 to 5%, more preferably 5%.

[0036] In the present invention, before the ethylation reaction is carried out, the present invention preferably performs gas replacement on the reaction container. In the present invention, the gas replacement is preferably performed by replacing the gas in the reaction container with nitrogen, and then evacuating the reaction container to a complete vacuum state and then introducing ethylene.

[0037] In the present invention, the temperature of the first-stage ethylation reaction is preferably 120-130° C., more preferably 120-125° C.; the pressure of the first-stage ethylation reaction is preferably 1-1.2 MPa.

[0038] In the present invention, the temperature of the second-stage ethylation reaction is preferably 110-120° C., and the pressure of the second-stage ethylation reaction is preferably 0.9-1 MPa.

[0039] In the present invention, the temperature of the third stage ethylation reaction is preferably 100-110° C., and the pressure of the third stage ethylation reaction is preferably 0.8-0.9 MPa.

[0040] In the present invention, the total heat preservation and pressure holding time of the first stage ethylation reaction, the second stage ethylation reaction and the third stage ethylation reaction is preferably 5 to 10 hours, more preferably 8 to 9 hours.

[0041] In the present invention, the ratio of the heat preservation and pressure holding time of the first stage ethylation reaction, the second stage ethylation reaction and the third stage ethylation reaction is preferably 3:3:(2-3), specifically preferably 3:3:2 or 3:3:3.

[0042] As one or more embodiments of the present invention, the heat preservation and pressure holding time of the first stage ethylation reaction is 3 hours; the heat preservation and pressure holding time of the second stage ethylation reaction is 3 hours; and the heat preservation and pressure holding time of the third stage ethylation reaction is 2 hours.

[0043] As one or more embodiments of the present invention, the heat preservation and pressure holding time of the first stage ethylation reaction is 3 hours; the heat preservation and pressure holding time of the second stage ethylation reaction is 3 hours; and the heat preservation and pressure holding time of the third stage ethylation reaction is 3 hours.

[0044] In the present invention, after the third stage ethylation reaction is completed, it is preferred to first introduce nitrogen to replace the gas in the reactor and nitrogen seal it before taking out the aqueous solution of the alkali metal diethyl phosphate.

[0045] After obtaining an aqueous solution of an alkali metal diethyl phosphate, the present invention mixes the aqueous solution of the alkali metal diethyl phosphate with a water-soluble aluminum salt to carry out a precipitation reaction, and separates the solid from the liquid to obtain the aluminum diethyl phosphonate; the mass percentage of butyl ethyl phosphinate aluminum in the aluminum diethyl phosphonate is ≤1%.

[0046] In the present invention, the water-soluble aluminum salt is preferably aluminum sulfate. In the present invention, the aluminum sulfate is preferably aluminum sulfate hydrate, specifically preferably one or more of aluminum sulfate hexahydrate, aluminum sulfate hexadecahydrate and aluminum sulfate octahydrate.

[0047] In the present invention, the molar ratio of the water-soluble aluminum salt to the diethyl phosphate alkali metal salt is preferably (1.1-1.2):6.

[0048] In the present invention, the precipitation reaction is preferably carried out under normal pressure.

[0049] In the present invention, the temperature of the precipitation reaction is preferably 50 to 100°C, more preferably 50 to 80°C, and even more preferably 70 to 75°C.

[0050] In the present invention, the pH value of the precipitation reaction is preferably 2-6.

[0051] In the present invention, there is no special requirement for the holding time of the precipitation reaction, as long as the precipitation reaction is ensured to be complete.

[0052] In the present invention, the solid-liquid separation is preferably performed by filtration. In the present invention, the solid product obtained by the solid-liquid separation is preferably dried to obtain the diethyl aluminum phosphonate.

[0053] The present invention provides diethyl aluminum phosphonate prepared by the preparation method described in the above technical solution, wherein the mass percentage of butyl ethyl aluminum phosphinate in the diethyl aluminum phosphonate is ≤1%.

[0054] The aluminum diethylphosphonate obtained by the present invention is a white solid powder.

[0055] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0056] Example 1

[0057] according to Figure 1 and Figure 2 The reaction process is as follows: 300 kg of sodium hypophosphite monohydrate is dissolved in 600 kg of water and pumped into a 2000 L autoclave. The gas in the reactor is then replaced with nitrogen, evacuated to a complete vacuum, and then ethylene is pressed to 1.0 MPa. The temperature is raised to 125° C. After reaching the reaction temperature, 252 kg of a prepared 5% ammonium persulfate aqueous solution is pumped into the reactor using a high-pressure pump for reaction. The reaction is carried out for 3 hours, and the temperature is then lowered to 120° C., the pressure is 0.9 MPa, and the reaction is carried out for 3 hours. Finally, the temperature is lowered to 110° C., the pressure is 0.8 MPa, and the reaction is carried out for 2 hours to obtain an aqueous solution of alkali metal diethyl phosphate.

[0058] The aqueous solution of sodium diethyl phosphate was transferred to a precipitation kettle and heated to 70°C. 5800 kg of 20 wt% aqueous aluminum sulfate solution was added dropwise within 2 hours. The mixture was reacted for 4 hours, filtered and dried to obtain 1048 kg of white solid powder with a yield of 95.1%.

[0059] Example 2

[0060] 300 kg of sodium hypophosphite monohydrate was dissolved in 900 kg of water and pumped into a 2000 L autoclave. The atmosphere in the reactor was then replaced with nitrogen, evacuated to a complete vacuum, and then ethylene pressure was increased to 1.2 MPa. The temperature was raised to 120°C. Once the reaction temperature was reached, 300 kg of 5% ammonium persulfate was pumped into the reactor using a high-pressure pump for reaction. The reaction was continued for 3 hours. The temperature was then lowered to 110°C, the pressure was 1.0 MPa, and the reaction was continued for 3 hours. Finally, the temperature was lowered to 100°C, the pressure was 0.9 MPa, and the reaction was continued for 3 hours to obtain an aqueous solution of alkali metal diethyl phosphate.

[0061] The aqueous solution of sodium diethyl phosphate was transferred to a precipitation kettle and heated to 75°C. 5800 kg of 20 wt% aqueous aluminum sulfate solution was added dropwise within 1 hour. The mixture was reacted for 4 hours, filtered and dried to obtain 1037 kg of white solid powder with a yield of 94.0%.

[0062] Example 3

[0063] The same as Example 1, except that 200 kg of 5% sodium persulfate was used to initiate the reaction, and the yield was 94.5%.

[0064] Example 4

[0065] The same as Example 1, except that 250 kg of 5 wt% hydrogen peroxide was used to initiate the reaction, and the yield was 96.2%.

[0066] Example 5

[0067] Same as Example 1, except that the precipitation temperature is 65°C, the precipitation time is 5 hours, and the yield is 93.0%

[0068] Comparative Example 1

[0069] 300 kg of sodium hypophosphite monohydrate was dissolved in 600 kg of water and pumped into a 2000 L autoclave. The atmosphere in the reactor was then replaced with nitrogen, evacuated to a complete vacuum, and ethylene pressure was increased to 1.0 MPa. The temperature was raised to 125°C. Once the reaction temperature was reached, 252 kg of 5% ammonium persulfate was pumped into the reactor using a high-pressure pump. The reaction continued for 8 hours to obtain an aqueous solution of alkali metal diethyl phosphate.

[0070] The aqueous solution of sodium diethyl phosphate was transferred to a precipitation kettle and heated to 70°C. 5800 kg of 20 wt% aqueous aluminum sulfate solution was added dropwise within 2 hours. The mixture was reacted for 4 hours, filtered and dried to obtain 1048 kg of white solid powder with a yield of 94.8%.

[0071] Comparative Example 2

[0072] 300 kg of sodium hypophosphite monohydrate was dissolved in 600 kg of water and pumped into a 2000 L autoclave. The atmosphere in the reactor was then replaced with nitrogen, evacuated to a complete vacuum, and ethylene pressure was increased to 1.0 MPa. The temperature was raised to 110°C. Once the reaction temperature was reached, 252 kg of 5% ammonium persulfate was pumped into the reactor using a high-pressure pump. The reaction continued for 8 hours to obtain an aqueous solution of alkali metal diethyl phosphate.

[0073] The aqueous solution of sodium diethyl phosphate was transferred to a precipitation kettle and heated to 70°C. 5800 kg of 20 wt% aluminum sulfate aqueous solution was added dropwise within 2 hours. The mixture was reacted for 4 hours and filtered and dried to obtain 1048 kg of white solid powder with a yield of 94.5%.

[0074] Comparative Example 3

[0075] 300 kg of sodium hypophosphite monohydrate was dissolved in 600 kg of water and pumped into a 2000 L autoclave. The atmosphere in the reactor was then replaced with nitrogen, evacuated to a complete vacuum, and ethylene pressure was increased to 0.9 MPa. The temperature was raised to 110°C. Once the reaction temperature was reached, 252 kg of 5% ammonium persulfate was pumped into the reactor using a high-pressure pump. The reaction continued for 8 hours to obtain an aqueous solution of alkali metal diethyl phosphate.

[0076] The above sodium diethyl phosphate aqueous solution was transferred to a precipitation kettle and heated to 70°C. 5800 kg of 20% aluminum sulfate aqueous solution was added dropwise within 2 hours. The mixture was reacted for 4 hours, filtered and dried to obtain 1037 kg of white solid powder with a yield of 94%.

[0077] Test Example 1

[0078] Index detection

[0079] 1. Inspection methods:

[0080] 1) Purity detection method:

[0081] Nuclear magnetic phosphorus spectroscopy analysis method

[0082] 2. Experimental results:

[0083] 1) The test results of the embodiment and the comparative example are shown in Table 1. Figure 3 and Figure 4 .

[0084] Table 1 Test results

[0085]

[0086]

[0087] In summary, compared with the prior art methods (Comparative Examples 1 to 3), the method provided by the present invention can well control the generation of impurities, with impurities less than 1%, and the purity is greatly improved. At the same time, the mother liquor solution can be well recovered and reused, greatly reducing energy consumption and environmental pollution, achieving green environmental protection and the development trend of composite green chemistry.

[0088] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for preparing aluminum diethylphosphonate, characterized in that: The following steps are involved: An alkali metal hypophosphite, a free radical initiator and water are mixed and subjected to a first-stage ethylation reaction in an ethylene atmosphere to obtain a first transition state system; the first transition state system is cooled and depressurized before being subjected to a second-stage ethylation reaction to obtain a second transition state system; the second transition state system is cooled and depressurized before being subjected to a third-stage ethylation reaction to obtain an aqueous solution of an alkali metal diethyl phosphate; the temperature of the first-stage ethylation reaction is 120-130° C., the pressure of the first-stage ethylation reaction is 1-1.2 MPa, the temperature of the second-stage ethylation reaction is 110-120° C., the pressure of the second-stage ethylation reaction is 0.9-1 MPa, the temperature of the third-stage ethylation reaction is 100-110° C., and the pressure of the third-stage ethylation reaction is 0.8-0.9 MPa; The aqueous solution of the diethyl phosphate alkali metal salt and a water-soluble aluminum salt are mixed to carry out a precipitation reaction, and the diethyl aluminum phosphite is obtained by solid-liquid separation; the mass percentage of butyl ethyl phosphinate aluminum in the diethyl aluminum phosphite is ≤1%.

2. The preparation method according to claim 1, characterized in that The total heat preservation and pressure preservation time of the first-stage ethylation reaction, the second-stage ethylation reaction and the third-stage ethylation reaction is 5 to 10 hours.

3. The preparation method according to claim 2, characterized in that The ratio of the heat preservation and pressure preservation time of the first stage ethylation reaction, the second stage ethylation reaction and the third stage ethylation reaction is 3:3:(2-3).

4. The preparation method according to claim 1, characterized in that The molar ratio of the alkali metal hypophosphite to the ethylene is 1:(2-5); The free radical initiator is one or more of ammonium persulfate, sodium persulfate, hydrogen peroxide, performic acid and peracetic acid; the molar ratio of the alkali metal hypophosphite to the free radical initiator is preferably (50-100):

1.

5. The preparation method according to claim 1, characterized in that The water-soluble aluminum salt is aluminum sulfate; The molar ratio of the water-soluble aluminum salt to the diethyl phosphate alkali metal salt is (1.1-1.2):

6.

6. The preparation method according to claim 1 or 5, characterized in that The temperature of the precipitation reaction is 50-100° C., and the pH value of the precipitation reaction is 2-6.

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