Dialkyl phosphinate preparation system for flame retardant

Abstract

The dialkyl phosphinate preparation system comprises a reaction assembly and a distillation assembly, the reaction assembly comprises a reaction kettle and a by-product recovery tank, the distillation assembly comprises a distillation kettle, a raw material recovery tank and a product collection tank, a top feed port of the reaction kettle is connected with a raw material pipeline, and the by-product recovery tank is connected with a bottom feed port of the reaction kettle. A bottom discharge port of the reaction kettle is connected with a distillation kettle, rectification devices are respectively arranged at the tops of the reaction kettle and the distillation kettle, a rectification device outlet at the top of the reaction kettle is connected with a byproduct recovery tank and the reaction kettle, a rectification device outlet at the top of the distillation kettle is connected with a raw material recovery tank and a product collection tank, and the distillation kettle is connected with a vacuum assembly. According to the method, synthesis of various methyl ethyl phosphinate products is realized, low-boiling-point substances are continuously evaporated out in the reaction process, the reaction is promoted to proceed forwards while the low-boiling-point substances are recycled, unconverted raw materials and catalysts at the bottom of a kettle can be applied to the next batch of reaction, and the equipment cost and waste pollution are remarkably reduced.

Description

Technical Field

[0001] This utility model relates to the field of flame retardant preparation technology, and in particular to a dialkylphosphinate preparation system for flame retardants. Background Technology

[0002] Currently, most traditional phosphate esters are formed by reacting phosphorus trichloride, phosphorus oxychloride, phosphorus pentoxide, etc., with corresponding compounds containing hydroxyl, amino, or epoxy groups. Common examples include triethyl phosphate (TEP), tributyl phosphate (TDP), triphenyl phosphate (TPP), tri(xylene) phosphate (TXP), tri(α-chloroethyl) phosphate (TCEP), tri(1,3-dichloro-2-propyl) phosphate (TDCPP), and tri(2-chloroisopropyl) phosphate (TCPP). These flame retardants have been widely used in many fields such as home furnishings, building materials, coatings, corrosion protection, and rubber. Dialkylphosphinates are one type of organophosphorus flame retardant. They possess advantages such as long-lasting flame retardant effect, good compatibility with polymer substrates, and weather resistance, and are therefore widely used in polyurethane, epoxy resin, polycarbonate, unsaturated resins, and other polymer materials.

[0003] Dialkylphosphinates, as shown in Formula 1, offer advantages over traditional halogenated flame retardants, including storage stability, environmental friendliness, low toxicity, and high flame retardant efficiency. Low molecular weight dialkylphosphinates typically have low boiling points, making them prone to migration and atomization as flame retardants. Therefore, it is necessary to modify the carbon chain length to increase their boiling point and reduce migration and atomization. There are few methods for synthesizing dialkylphosphinates. Traditional industrial production mainly uses dialkylphosphinates and excess halogenated hydrocarbons or olefins as raw materials. Another method involves reacting dialkylphosphinate acyl halides and epoxy compounds under a catalyst to obtain the dialkylphosphinate flame retardant. The disadvantages of these two methods are the need for large quantities of halogenated reagents, difficulty in recycling, environmental impact, high requirements for reaction equipment, and highly dangerous and complex processes. Therefore, transesterification can be used to adjust the molecular weight and boiling point of dialkylphosphinates, enabling the rapid preparation of dialkylphosphinates with different ester groups to match the performance requirements of flame retardants.

[0004]

[0005] Formula 1

[0006] Further literature search revealed a paper (“Synthesis of Cyclic Phosphinates by Microwave-Assisted Ionic-Liquid-Promoted Alcoholysis” Nikoletta Harsági, Nóra ZsuzsaKiss, László Drahos [J]. Synthesis 2022; 54(17): 3899-3905), which reported a method for preparing a series of alkyl phosphinates in 86%-94% yield by using microwave-assisted ionic liquid catalysis to catalyze the transesterification reaction of corresponding methyl or ethyl phosphinates with alcohols. This method requires high temperatures, uses alcohol equivalents as high as 15 equivalents, and requires microwaves for the reaction, thus it is not suitable for large-scale industrial production. Although this method has certain limitations, it provides a new alternative to using phosphoric acid and chloride phosphates for esterification.

[0007] In summary, there is currently no economically and industrially feasible method for preparing dialkylphosphinates without using halogens as reactants and in high yield. Furthermore, there is no method in which the final product can be easily obtained or isolated, or specifically prepared using particular reaction conditions (such as transesterification). Utility Model Content

[0008] This invention aims to provide a simple and efficient system for preparing dialkylphosphine esters for flame retardant applications. Using readily available low-molecular-weight dialkyl esters as raw materials, it prepares dialkylphosphine esters suitable for flame retardant applications. Compared to traditional halogenated flame retardants, it offers advantages such as storage stability, environmental friendliness, low toxicity, and high flame retardant efficiency. The process conditions of this invention are mild, easily implemented in industrial settings, and the post-processing is simple and convenient, resulting in a product purity of up to 99%.

[0009] To achieve the above-mentioned objectives, the technical solution of this utility model is as follows:

[0010] A system for preparing dialkylphosphinates for flame retardants includes a reaction assembly and a distillation assembly. The reaction assembly includes a reaction vessel and a by-product recovery tank. The distillation assembly includes a distillation vessel, a raw material recovery tank, and a product collection tank. The top inlet of the reaction vessel is connected to a raw material pipeline, and the bottom outlet of the reaction vessel is connected to the distillation vessel. A distillation device is provided at the top of both the reaction vessel and the distillation vessel. The outlet of the distillation device at the top of the reaction vessel is connected to the by-product recovery tank and the reaction vessel. The outlet of the distillation device at the top of the distillation vessel is connected to the raw material recovery tank and the product collection tank. The distillation vessel is connected to a vacuum assembly.

[0011] The distillation apparatus includes a fractionating column and a condenser. The bottom of the fractionating column is connected to the top of the reaction vessel and the distillation vessel, respectively. The top of the fractionating column is connected to the condenser. The condenser outlet of the reaction component is connected to the by-product recovery tank and the reaction vessel. The condenser outlet of the distillation component is connected to the raw material recovery tank and the product collection tank.

[0012] A filter, specifically a bag filter, is installed on the connecting pipe between the reaction vessel and the distillation vessel.

[0013] The reaction vessel and the distillation vessel are respectively equipped with jackets on the outside, with a steam inlet at the upper part of the jacket and a steam outlet at the lower part of the jacket.

[0014] Temperature sensor I is installed at the top of the fractionation column and the condenser respectively; temperature sensor II and pressure sensor are installed inside the reaction vessel and the distillation vessel respectively; flow meter and electric valve I are installed at the feed inlet of the reaction vessel; electric valve II is installed at the steam inlet.

[0015] The condenser of the distillation assembly is connected to the raw material recovery tank and the product collection tank via an electric three-way valve I.

[0016] The condenser of the reactor is connected to the by-product recovery tank and the reactor via an electric three-way valve II.

[0017] The vacuum assembly includes a vacuum pump, and a vacuum buffer tank is installed on the connecting pipe between the vacuum pump and the distillation vessel.

[0018] A delivery pump is installed on the connecting pipe between the reaction vessel and the distillation vessel.

[0019] The beneficial effects of this utility model are:

[0020] 1. The dialkylphosphinate preparation system of this invention uses low molecular weight dialkylphosphinate ethyl ester and C3-C12 monohydric alcohols and / or dihydric alcohols and their derivatives as raw materials. The raw material supply is stable, and it has high universality for alcohol substrates, which has great application value.

[0021] 2. This invention enables the synthesis of various high molecular weight dialkylphosphinate products. During the reaction, low-boiling substances are continuously distilled off, and the recovery of low-boiling substances promotes the forward reaction. The unconverted raw materials and catalysts at the bottom of the reactor can be reused in the next batch of reaction, significantly reducing equipment costs and waste pollution. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the dialkylphosphinate preparation system for flame retardants according to this invention.

[0023] Figure 2 This is a flowchart illustrating the preparation of high molecular weight dialkylphosphinates using the low molecular weight dialkylphosphinate preparation system of this invention.

[0024] The components include: 1. Reactor; 2. By-product recovery tank; 3. Distillation vessel; 4. Raw material recovery tank; 5. Product collection tank; 6. Raw material pipeline; 7. Fractionating column; 8. Condenser; 9. Filter; 10. Jacket; 11. Vacuum pump; 12. Vacuum buffer tank. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited thereto.

[0026] In this utility model, as shown in Figure 2 Using the low molecular weight dialkylphosphonic acid ethyl ester as a raw material, a high molecular weight dialkylphosphonic acid ester was prepared by transesterification with a monohydric alcohol under alkaline catalyst, followed by stirred distillation and purification. The reaction process is as follows:

[0027]

[0028] Low molecular weight dialkyl groups may include any combination of methyl and / or ethyl groups.

[0029] R can include n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-dodecyl, isobutyl, isopentyl, isohexyl, isoheptyl, isooctyl, isonyl, isodecyl, tert-butyl, or neopentyl, etc.

[0030] Alkaline catalysts include, but are not limited to, alkali metal salts and organic bases.

[0031] In some embodiments, a monohydric alcohol reagent is added to a reaction vessel, low molecular weight dialkylphosphine ethyl ester is added to the reaction vessel, and a catalyst is added to the reaction vessel. The molar amount of the monohydric alcohol is 1-2 times that of the low molecular weight dialkylphosphine ethyl ester, and the catalyst is 1%-5% of the mass of the low molecular weight dialkylphosphine ethyl ester. The mixture is stirred evenly at room temperature, purged with nitrogen, and then heated to 100-140°C. The reaction is maintained at this temperature, and the fraction at the top of the column at 78°C is continuously collected. The reaction is carried out for 8-14 hours, and after the theoretically produced ethanol is collected, the temperature is lowered to room temperature.

[0032] In some embodiments, during the vacuum distillation stage, alcohol is distilled off at 3000-3800 Pa, a kettle temperature of 70-100°C, and a column top temperature of 60-90°C. The kettle temperature is then raised to 120-130°C, and the column top temperature is 110-120°C to distill off the foremilk. After the foremilk has been collected, the kettle temperature is raised to 130-140°C, and the column top temperature is 125-130°C to distill off the high molecular weight dialkylphosphinate product.

[0033] Example 1

[0034] like Figure 1As shown, this embodiment provides a dialkylphosphinate preparation system for flame retardants, including a reaction assembly and a distillation assembly. The reaction assembly includes a reaction vessel 1 and a by-product recovery tank 2. The distillation assembly includes a distillation vessel 3, a raw material recovery tank 4, and a product collection tank 5. The top inlet of the reaction vessel 1 is connected to a raw material pipeline 6, and the bottom outlet of the reaction vessel 1 is connected to the distillation vessel 3. A distillation apparatus is respectively installed at the top of the reaction vessel 1 and the distillation vessel 3. The outlet of the distillation apparatus at the top of the reaction vessel 1 is connected to the by-product recovery tank 2 and the reaction vessel 1. The outlet of the distillation apparatus at the top of the distillation vessel 3 is connected to the raw material recovery tank 4 and the product collection tank 5. The distillation vessel 3 is connected to a vacuum assembly. A jacket 10 is provided on the outside of the reaction vessel 1 and the distillation vessel 3. A steam inlet is provided at the upper part of the jacket 10, and a steam outlet is provided at the lower part of the jacket 10. The distillation apparatus includes a fractionating column 7 and a condenser 8. The bottom of the fractionating column 7 is connected to the top of the reaction vessel 1 and the distillation vessel 3, respectively. The top of the fractionating column 7 is connected to the condenser 8. The outlet of the condenser 8 of the reaction component is connected to the by-product recovery tank 2. The outlet of the condenser 8 of the distillation component is connected to the raw material recovery tank 4 and the product collection tank 5.

[0035] In this embodiment, the raw material monohydric alcohol used is isobutanol, the alkaline catalyst is anhydrous sodium carbonate, the byproduct is ethanol, and the pre-distillate is n-butanol.

[0036] This embodiment completes the preparation of high molecular weight dialkylphosphinate through the following steps:

[0037] S1: Add methyl ethyl phosphonate (100g), isobutanol (81.1g) and alkali metal salt catalyst (5g) into reactor 1 through the feed inlet.

[0038] S2: Steam is introduced into the steam inlet of reactor 1 to heat reactor 1 (130°C) and start the reaction. During the reaction, the by-product ethanol is distilled out by a distillation device and sent to the by-product recovery tank 2. The reaction ends when the theoretical amount of ethanol is recovered.

[0039] S3: After the reaction is completed, the reaction solution is transferred to the distillation vessel 3. Steam is introduced into the steam inlet of the distillation vessel 3 to heat the distillation vessel 3 to 80°C. The vacuum assembly evacuates the distillation vessel 3 to a vacuum degree of 3500Pa. The n-butanol fraction with a distillation temperature of 40-60°C is then transported to the raw material recovery tank 4.

[0040] S4: After the distillation of n-butanol is completed, the distillation temperature is increased. When the distillation temperature is below 120°C, the distilled fraction is sent to the raw material recovery tank 4. When the distillation temperature is above 120°C, the distilled fraction is sent to the product collection tank 5 until the distillation is completed.

[0041] In this embodiment, during the preparation of high molecular weight dialkyl hypophosphite, ethanol is separated while the reaction is underway, which promotes the forward reaction. The purification process involves segmented distillation, and all the forefractions can be reused and recovered, resulting in no waste liquid or waste gas generated.

[0042] Example 2

[0043] The difference between this embodiment and embodiment 1 is that a filter 9 is provided on the connecting pipe between the reaction vessel 1 and the distillation vessel 3 in this embodiment. The filter 9 is a bag filter 9; the rest of the structure is the same as in embodiment 1.

[0044] In this embodiment, the bag filter 9 is used to automatically filter the byproduct potassium carbonate during the material transfer process from the reactor 1 to the distillation vessel 3, thereby achieving automated operation of the preparation of dialkylphosphinate.

[0045] Example 3

[0046] Compared with Example 1, the difference in this embodiment is that temperature sensor I is respectively installed at the top of the fractionation column 7 and the condenser 8; temperature sensor II and pressure sensor are respectively installed inside the reaction vessel 1 and the distillation vessel 3; a flow meter and electric valve I are installed at the feed inlet of the reaction vessel 1; and electric valve II is installed at the steam inlet.

[0047] The condenser 8 of the distillation assembly is connected to the raw material recovery tank 4 and the product collection tank 5 via an electric three-way valve I.

[0048] The condenser 8 of the reactor 1 is connected to the by-product recovery tank 2 and the reactor 1 via an electric three-way valve II;

[0049] The vacuum assembly includes a vacuum pump 11, and a vacuum buffer tank 12 is provided on the connecting pipe between the vacuum pump 11 and the distillation vessel 3; the rest of the structure is the same as in Embodiment 1.

[0050] In this embodiment, a delivery pump is installed on the connecting pipe between the reaction vessel 1 and the distillation vessel 3.

[0051] The dialkylphosphonate preparation system in this embodiment is also equipped with an external controller, which is connected to temperature sensor I, temperature sensor II, pressure sensor, flow meter, electric valve I, electric valve II, electric three-way valve I, electric three-way valve II, delivery pump, vacuum pump 11 and vacuum buffer tank 12 respectively.

[0052] In this embodiment, the preparation of high molecular weight dialkylphosphinate is accomplished through the following steps:

[0053] S1: Set parameters in the controller, including: raw material addition amount, reaction temperature, reaction time, distillation temperature, distillation pressure, etc.

[0054] S2: The controller controls the electric valve at the feed inlet of reactor 1 to sequentially add methyl ethyl phosphonate (30kg), n-butanol (29401g) and alkali metal salt catalyst (1500g). The controller monitors the amount of raw materials added in real time according to the parameters of the flow meter at the feed inlet of reactor 1. When the raw materials are added, the controller controls the electric valve I to close.

[0055] S3: After the materials are added, the controller controls the electric valve II at the steam inlet of reactor 1 to open and introduce steam into the jacket 10 of reactor 1 to heat reactor 1. The controller monitors the temperature inside reactor 1 in real time based on the data from the temperature sensor II inside reactor 1. When the temperature is lower or higher than the set temperature, the controller controls the steam flow by controlling the opening and closing degree of the electric valve II at the steam inlet of reactor 1, thereby controlling the temperature of reactor 1.

[0056] S4: After the reaction starts, the controller monitors the distillate temperature in real time through the temperature sensor I at the top of the fractionation column 7 of the reaction assembly. When the distillate temperature is higher than the set temperature, the controller controls the electric three-way valve to connect the condenser 8 to the reactor 1, so that the distillate flows back to the reactor 1. When the distillate temperature is at the set temperature, the controller controls the electric three-way valve I to connect the condenser 8 to the by-product recovery tank 2 to recover the by-product. When the amount of by-product recovered in the by-product recovery tank 2 reaches the set value, the reaction is judged to be complete.

[0057] S5: After the reaction is completed, the control pump delivers the reaction liquid from reactor 1 to filter 9 to filter the solid byproducts in the reaction liquid. The filtrate is then delivered to distillation vessel 3. The control valve II at the steam inlet of distillation vessel 3 is opened to introduce steam into the jacket 10 of distillation vessel 3 to heat distillation vessel 3. The controller monitors the temperature inside distillation vessel 3 in real time based on the data from temperature sensor II inside distillation vessel 3. The temperature inside distillation vessel 3 is controlled by controlling the opening and closing degree of the electric valve II at the steam inlet of reactor 1.

[0058] S6: After distillation begins, the temperature of the distillate is monitored in real time by the temperature sensor I at the top of the fractionation column 7 of the distillation assembly. When the temperature of the distillate is at the set pre-distillate temperature, the condenser 8 is connected to the raw material recovery tank 4 by controlling the electric three-way valve II. When the temperature of the distillate is lower or higher than the set pre-distillate temperature, the distillate is returned to the distillation kettle 3, and the electric three-way valve II is controlled to connect the condenser 8 to the distillation kettle 3 to recover the pre-distillate.

[0059] S7: After the current fraction is distilled, the electric valve controlling the steam inlet of the distillation vessel 3 increases the steam flow. When the fraction temperature is higher than the set product fraction temperature, the electric three-way valve II is used to connect the distillation vessel 3 to the product collection tank 5 to start collecting the product until the product distillation is complete.

[0060] It is understood that this utility model has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of this utility model. Furthermore, under the teachings of this utility model, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of this utility model. Therefore, this utility model is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of this utility model.

Claims

1. A system for the preparation of dialkyl phosphinic acid esters for use as flame retardants, characterized by: The application relates to a reaction and distillation assembly, which comprises a reaction assembly and a distillation assembly, the reaction assembly comprises a reaction kettle (1) and a by-product recovery tank (2), the distillation assembly comprises a distillation kettle (3), a raw material recovery tank (4) and a product collection tank (5), a raw material pipeline (6) is connected to the top feeding port of the reaction kettle (1), the bottom discharging port of the reaction kettle (1) is connected to the distillation kettle (3), the top of the reaction kettle (1) and the top of the distillation kettle (3) are respectively provided with rectification devices, the rectification device outlet at the top of the reaction kettle (1) is connected to the by-product recovery tank (2) and the reaction kettle (1), the rectification device outlet at the top of the distillation kettle (3) is connected to the raw material recovery tank (4) and the product collection tank (5), and the distillation kettle (3) is connected with a vacuum assembly.

2. The system for producing a dialkyl phosphinic acid ester according to claim 1, characterized by: The rectification device comprises a fractionating column (7) and a condenser (8), the bottom of the fractionating column (7) is connected to the top of the reaction kettle (1) and the top of the distillation kettle (3) respectively, the top of the fractionating column (7) is connected to the condenser (8), the condenser (8) outlet of the reaction assembly is connected to the by-product recovery tank (2) and the reaction kettle (1), and the condenser (8) outlet of the distillation assembly is connected to the raw material recovery tank (4) and the product collection tank (5).

3. The system for producing a dialkyl phosphinic acid ester of claim 1, wherein: A filter (9) is arranged on the connecting pipeline of the reaction kettle (1) and the distillation kettle (3), and the filter (9) is a bag filter (9).

4. The system for producing a dialkyl phosphinic acid ester of claim 1, wherein: The reaction kettle (1) and the distillation kettle (3) are respectively provided with jackets (10) outside, a steam inlet is arranged on the upper part of the jacket (10), and a steam outlet is arranged on the lower part of the jacket (10).

5. The system for producing a dialkyl phosphinic acid ester of claim 2, wherein: Temperature sensors I are arranged on the top of the fractionating column (7) and the condenser (8) respectively, temperature sensors II and pressure sensors are arranged in the reaction kettle (1) and the distillation kettle (3) respectively, and a flow meter and an electric valve I are arranged on the feeding port of the reaction kettle (1).

6. The system for producing a dialkyl phosphinic acid ester of claim 4, wherein: The steam inlet is provided with an electric valve II.

7. The system for preparing a dialkyl phosphinic acid ester of claim 1, wherein: The condenser (8) of the reaction kettle (1) is connected to the by-product recovery tank (2) and the reaction kettle (1) through an electric three-way valve I.

8. The system for producing a dialkyl phosphinic acid ester of claim 1, wherein: The condenser (8) of the distillation assembly is connected to the raw material recovery tank (4) and the product collection tank (5) through an electric three-way valve II.

9. The system for producing a dialkyl phosphinic acid ester of claim 1, wherein: The vacuum assembly comprises a vacuum pump (11), and a vacuum buffer tank (12) is arranged on the connecting pipeline of the vacuum pump (11) and the distillation kettle (3).

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