Alkylphosphonic acid compounds, their production methods and uses

Abstract

The present invention discloses an alkylphosphonic acid-based compound and its preparation and use. The compound's structure includes aluminum alkylphosphonate, aluminum hydrogen alkylphosphonate, aluminum phosphite, and water of crystallization. When the compound is used in combination with aluminum diethylphosphinate as a flame retardant, it effectively solves the problems of foaming and mold contamination during the production of flame-retardant nylon, and the resulting material has good mechanical properties and flame retardancy.

Description

[Technical Field]

[0001] The present invention relates to the technical field of organic synthesis, and more particularly to alkylphosphonic acid compounds and their preparation and use. [Background technology]

[0002] Aluminum phosphite is currently widely used as a flame retardant synergist due to its excellent flame retardant synergy with aluminum diethylphosphinate, low water solubility, and acidity. It exhibits excellent flame retardancy when applied to glass fiber-reinforced engineering plastics, such as nylon and polyester. According to research in Chinese Patent CN104114485A, mixtures of aluminum hydrogen phosphite and aluminum salts are significantly more stable than pure aluminum phosphite. However, both aluminum phosphite and aluminum hydrogen phosphite still have poor thermal stability due to the strongly reducing phosphorus-hydrogen bond in their structures. Furthermore, they are prone to decomposition during high-temperature decomposition, generating highly toxic and flammable phosphine gas in the air, posing a significant safety risk. Furthermore, aluminum phosphite is an inorganic salt and has poor compatibility with polymer matrixes. Therefore, increasing its dosage as a synergistic flame retardant significantly impacts the mechanical properties and processing performance of the matrix, significantly limiting its applications.

[0003] The introduction of alkyl into aluminum alkylphosphonate converts the phosphorus-hydrogen bond in aluminum phosphite into a phosphorus-carbon bond, improving compatibility with resin matrix materials. Furthermore, because aluminum alkylphosphonate does not have a reducing phosphorus-hydrogen bond in its molecular structure, it has higher thermal stability than phosphorous acid and does not generate highly toxic and flammable phosphine gas during the decomposition process.

[0004] Although aluminum phosphite and aluminum alkylphosphonate are flame retardant synergists for aluminum diethylphosphinate, they do not have good flame retardancy by themselves, but they can improve the flame retardancy of diethylphosphinate to some extent. The flame retardant system of aluminum alkylphosphonate and aluminum diethylphosphinate effectively reduces screw corrosion during resin processing, and also improves the whiteness of the flame-retardant polymer matrix.

[0005] However, in actual production processes, when aluminum phosphite or aluminum alkylphosphonate is used in combination with aluminum diethylphosphinate for flame-retardant PA66, PA6, and high-temperature nylon, it is found that foaming is likely to occur during the screw rod insertion and removal process, and mold contamination is likely to occur during the injection molding process. Summary of the Invention

[0006] The present invention overcomes the drawbacks of the prior art and aims to provide an alkylphosphonic acid compound that, when used in combination with aluminum diethylphosphinate as a flame retardant for flame-retardant PA66, PA6, and high-temperature nylon, does not foam during injection molding, is less likely to cause mold contamination, and produces materials with good mechanical properties and flame retardancy.

[0007] Another object of the present invention is to provide a method for preparing said compound.

[0008] Another object of the present invention is to provide the use of said compound as a flame retardant synergist for aluminum diethylphosphinate.

[0009] To achieve the above object, the present invention is achieved by the following technical solutions.

[0010] An alkylphosphonic acid compound, the structural formula of which is represented by formula (I): JPEG2025534125000002.jpg21128(I) (In formula (I), R is methyl or ethyl, x is 2.6 to 2.98, y is 0.01 to 0.39, z is 0.01 to 0.10, and m is 1.0 to 2.0.)

[0011] The present invention provides an alkylphosphonic acid-based compound containing aluminum alkylphosphonate, aluminum hydrogen alkylphosphonate, aluminum phosphite, and water of crystallization, which can effectively solve the problem of foaming during screw extrusion when applied to high-temperature nylon, and can also effectively solve the problem of mold contamination during injection molding when used with flame-retardant PA66, PA6, and high-temperature nylon.

[0012] Preferably, the particle size D50 of the compound is 1 to 100 μm.

[0013] Preferably, the content of sodium sulfate in the compound is 100 to 5000 ppm.

[0014] The method for producing the compound includes the steps of: a step of mixing an alkyl phosphonate and a phosphite, subjecting the mixture to a metathesis reaction with an aqueous aluminum salt solution, and then sequentially carrying out precipitation, filtration, washing, and drying at 105 to 120°C to obtain a compound, wherein the temperature of the metathesis reaction is 60 to 130°C; Includes:

[0015] Specifically, the alkylphosphonate is prepared by any one of the following methods:

[0016] First method: The alkylphosphonic acid diester is hydrolyzed under basic conditions to give an alkylphosphonate.

[0017] Second method: Step S1: Phosphorous acid is reacted with gaseous ethylene in an aqueous solution in the presence of an initiator to obtain alkylphosphonic acid. Step S2: An alkylphosphonic acid is reacted with an equimolar amount of a basic solution to obtain an alkylphosphonate.

[0018] Preferably, the aqueous aluminum salt solution is an aqueous aluminum sulfate solution or an aqueous aluminum chloride solution.

[0019] Preferably, the aluminum salt aqueous solution is added slowly using a high-pressure metering pump, and the addition time is 60 to 180 minutes.

[0020] Preferably, in step S2, the basic solution is an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution.

[0021] Use of said compound as a flame retardant synergist for aluminum diethylphosphinate.

[0022] A composition comprising 1 to 7 parts by weight of the above compound and 12 to 19 parts by weight of aluminum diethylphosphinate.

[0023] Use of said composition as a flame retardant in flame retarding PA66, PA6, and high temperature nylon.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The compound according to the present invention comprises aluminum alkylphosphonate, aluminum hydrogen alkylphosphonate, aluminum phosphite, and water of crystallization. When the compound is used in combination with aluminum diethylphosphinate as a flame retardant for making nylon flame retardant, it can effectively solve the problems of foaming and mold contamination during the manufacturing process, and the mechanical properties and flame retardancy of the manufactured material are good. [Brief explanation of the drawings]

[0026] [Figure 1] This is an effect diagram without foaming phenomenon. [Figure 2] This is an effect diagram showing a slight foaming phenomenon. [Figure 3] This is an effect diagram showing the foaming phenomenon clearly. DETAILED DESCRIPTION OF THE INVENTION

[0027] The present invention will be described in more detail below with reference to specific examples. These examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention. Unless otherwise specified, all experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used are commercially available products. The compounds according to Examples 1 to 4 and Comparative Examples 1 to 3 were produced by the following method, including the following steps S1 to S3.

[0028] Step S1: Solid phosphorous acid, water, and sodium persulfate are placed in an autoclave, followed by nitrogen gas replacement, followed by supplying ethylene to a pressure reducer to maintain a constant pressure of 1.6 MPa, heating to 85°C, maintaining the temperature for 6 hours, continuously replenishing the aqueous sodium persulfate solution during this 6-hour period, then maintaining the temperature at 90°C for another 1 hour, cooling, and venting to obtain an aqueous ethylphosphonic acid solution, prepared from 5 g of sodium persulfate and 20 g of water. Step S2: Phosphorous acid was added to an aqueous solution of ethylphosphonic acid, and the solution was neutralized with a 20% aqueous solution of sodium hydroxide to a pH of 7, to obtain an aqueous solution of sodium ethylphosphonate / sodium phosphite. Step S3: The aqueous solution of sodium ethylphosphonate / sodium phosphite was heated to T1, and the aqueous solution of aluminum sulfate was continuously replenished using a metering pump for 120 minutes to carry out a metathesis reaction. The mixture was then cooled and filtered, and the cake was washed three times with three times the amount of water and dried at a temperature of T2 until it reached a constant weight, thereby obtaining a compound.

[0029] The amounts of raw materials and process parameters for Examples 1 to 4 and Comparative Examples 1 to 3 are shown in Table 1.

[0030] Table 1: Doses of raw materials and process parameters for Examples 1 to 4 and Comparative Examples 1 to 3 JPEG2025534125000003.jpg44167

[0031] Example 5 Step S1: Dimethyl ethylphosphonate and 120 mol % of 20 wt % aqueous sodium hydroxide solution were mixed, and the mixture was kept at 80°C for 3 hours while stirring. After cooling to room temperature, the mixture was neutralized with 10% aqueous sulfuric acid solution to pH=7, thereby obtaining an aqueous sodium ethylphosphonate solution. Step S2: 3.45 mol % of phosphorous acid was added to an aqueous solution of sodium ethylphosphonate, and the solution was neutralized with a 20% aqueous solution of sodium hydroxide to a pH of 7, to obtain an aqueous solution of sodium ethylphosphonate / sodium phosphite. Step S3: The aqueous solution of sodium ethylphosphonate / sodium phosphite was heated to 60°C, and the aqueous aluminum sulfate solution was continuously replenished using a metering pump for 120 minutes to carry out a metathesis reaction. The mixture was then cooled and filtered, and the cake was washed three times with three times the amount of water and dried at 120°C until a constant weight was obtained, thereby obtaining a compound.

[0032] The compounds produced in Examples 1 to 5 above had a particle size D50 of 1 to 100 μm and a sodium sulfate content of 100 to 5000 ppm. The measurement method was as follows.

[0033] (1) Particle size: An appropriate amount of sample was moistened with a small amount of ethanol, water was added, and the mixture was gently stirred with a glass rod, and the particle size was measured using a Malvern laser diffraction particle size distribution analyzer.

[0034] (2) Sodium sulfate content: An appropriate amount of sample was taken, and the content of sulfate groups was measured using an ICP device, and the content of sodium sulfate was calculated.

[0035] The specific results of the particle size D50 and sodium sulfate content of the compounds produced in Examples 1 to 5 are shown in Table 2.

[0036] Table 2 JPEG2025534125000004.jpg30129

[0037] For the compounds produced in the above Examples 1 to 5 and Comparative Examples 1 to 3, 1 H-NMR spectroscopy was performed. The method for measuring the content of water of crystallization was as follows.

[0038] After drying, each compound produced in Examples 1 to 5 and Comparative Examples 1 to 3 was quickly removed from the dryer, placed in a desiccator, cooled to room temperature, and weighed to obtain a mass m1. The compound was then dried at 150°C until a constant weight was reached, removed from the dryer, quickly placed in a desiccator, cooled to room temperature, and weighed to obtain a mass m0. The crystal water content was calculated as follows: Crystal water content = (m1 - m0) * M / (18 * m0), where M is the molecular weight of the compound without crystal water. The measurement results are shown in Table 3.

[0039] Table 3 Measurement results for Examples 1 to 5 and Comparative Examples 1 to 3 JPEG2025534125000005.jpg44147

[0040] As is clear from Table 3, the compound produced by the present invention contains aluminum alkylphosphonate, aluminum hydrogen alkylphosphonate, aluminum phosphite, and water of crystallization. As is clear from Comparative Example 1, when the metathesis reaction temperature and drying temperature are high and phosphorous acid is not added during the metathesis process, the compound produced contains only aluminum alkylphosphonate. As is clear from Comparative Example 2, when the drying temperature is high and phosphorous acid is not added during the metathesis process, the compound produced does not contain aluminum phosphite or water of crystallization. As is clear from Comparative Example 3, when the metathesis reaction temperature is high and phosphorous acid is not added during the metathesis process, the compound produced does not contain aluminum hydrogen alkylphosphonate or aluminum phosphite.

[0041] application Aluminum diethylphosphinate, glass fiber, PA66, PA6, and high-temperature nylon (PA10T) were all commercially available products.

[0042] In Comparative Examples 4 to 7, commercially available aluminum phosphite and the compounds prepared in Comparative Examples 1 to 3 were used as flame retardant synergists, and in Examples 6 to 12, Compounds 1 to 5 prepared in Examples 1 to 5 were used as flame retardant synergists, which were blended with aluminum diethylphosphinate, glass fiber, PA66, and PA6, respectively, and extruded. The dosages of each component in Comparative Examples 4 to 7 and Examples 6 to 12 are shown in Table 4, and the raw materials used in all parallel tests were the same type.

[0043] In Comparative Examples 8 to 11, commercially available aluminum phosphite and the compounds prepared in Comparative Examples 1 to 3 were used as flame retardant synergists, while in Examples 15 to 19, compounds 1 to 5 prepared in Examples 1 to 5 were used as flame retardant synergists, which were blended with aluminum diethylphosphinate, glass fiber, and high-temperature nylon (PA10T) and extruded. The amounts of each component in Comparative Examples 8 to 11 and Examples 13 to 19 are shown in Table 5, and the raw materials used in all parallel tests were the same type.

[0044] Table 4: Amounts (parts by weight) of each component in Comparative Examples 4 to 7 and Examples 6 to 12 JPEG2025534125000006.jpg70169

[0045] Table 5: Amount (parts by weight) of each component in Comparative Examples 8 to 11 and Examples 13 to 19 JPEG2025534125000007.jpg81169

[0046] Performance analysis The mechanical properties of the materials produced in Comparative Examples 4 to 7 and Examples 5 to 19 were measured, and foaming and mold contamination during the injection molding process were observed. Regarding foaming, "none" indicates that the material exhibited no foaming during the injection molding process, resulting in the best results, as shown in Figure 1. "slight foaming" indicates that the material exhibited a few bubbles during the injection molding process, resulting in a small number of holes inside the particles, resulting in a slightly poorer effect, as shown in Figure 2. "obvious foaming" indicates that the material exhibited a large number of bubbles during the injection molding process, resulting in many holes inside the particles, resulting in the worst results, as shown in Figure 3. Regarding mold contamination, "none" indicates that the material exhibited no mold contamination during the injection molding process, resulting in the best results. "slight" indicates that the material exhibited slight mold contamination during the injection molding process, resulting in a slightly poorer effect. "heavy" indicates that the material exhibited a large amount of mold contamination during the injection molding process, resulting in a slightly poorer effect.

[0047] (1) Tensile strength: Using a microcomputer-controlled electronic universal testing machine, the tensile strength of the material was measured at a tensile speed of 50 mm / min in accordance with GB / T1040-1992 "Testing Method for Tensile Properties of Plastics."

[0048] (2) Vertical burning: Measurements were conducted in accordance with the UL94-2006 standard. Five test specimens were prepared for each group, and the self-extinguishing time after the first ignition and the self-extinguishing time after the second ignition, the presence or absence of molten material dripping during the burning process, and the presence or absence of ignition of the cotton were recorded.

[0049] The measurement results are shown in Tables 6 and 7.

[0050] Table 6: Measurement results of Comparative Examples 4 to 7 and Examples 6 to 12 JPEG2025534125000008.jpg40169

[0051] As can be seen from Table 6, when the compound of the present invention was used in combination with aluminum diethylphosphinate to form a flame retardant, no mold contamination or foaming occurred during the injection molding process when used to flame retard PA6 and PA66, and the resulting materials had good mechanical and flame retardant properties. As can be seen from Comparative Example 4, when aluminum phosphite was used in combination with aluminum diethylphosphinate to form a flame retardant, mold contamination occurred during the injection molding process when used to flame retard PA6 and PA66, and the resulting materials only achieved a V-1 flame retardant. As can be seen from Comparative Example 5, when the compound of Comparative Example 1 was used in combination with aluminum diethylphosphinate to form a flame retardant, i.e., the compound contained only aluminum alkylphosphonate, mold contamination occurred during the injection molding process when used to flame retard PA6 and PA66, and the resulting materials only achieved a V-1 flame retardant. As is clear from Comparative Example 6, when the compound of Comparative Example 2 was used in combination with aluminum diethylphosphinate to form a flame retardant, i.e., when the compound did not contain aluminum phosphite and water of crystallization, mold contamination occurred during the injection molding process when used to flame retard PA6 and PA66. As is clear from Comparative Example 7, when the compound of Comparative Example 3 was used in combination with aluminum diethylphosphinate to form a flame retardant, i.e., when the compound did not contain aluminum hydrogen alkylphosphonate and aluminum phosphite, mold contamination occurred during the injection molding process when used to flame retard PA6 and PA66. From the above, it was found that in order to obtain good effects, it is necessary to simultaneously contain aluminum alkylphosphonate, aluminum hydrogen alkylphosphonate, aluminum phosphite, and water of crystallization in the compound, and then use it in combination with aluminum diethylphosphinate to form a flame retardant.

[0052] Table 7 Measurement results of Comparative Examples 8 to 11 and Examples 13 to 19 JPEG2025534125000009.jpg32169

[0053] As can be seen from Table 7, when the compound of the present invention was used in combination with aluminum diethylphosphinate to form a flame retardant for high-temperature nylon, no mold contamination occurred during the injection molding process, and no foaming occurred during the manufacturing process. The mechanical and flame-retardant properties of the resulting material were excellent. As can be seen from Comparative Example 8, when aluminum phosphite was used in combination with aluminum diethylphosphinate to form a flame retardant for high-temperature nylon, significant foaming occurred during the manufacturing process, mold contamination occurred during the injection molding process, and the flame-retardant properties of the resulting material only reached Class V-1. As can be seen from Comparative Example 9, when the compound of Comparative Example 1 was used in combination with aluminum diethylphosphinate to form a flame retardant for high-temperature nylon, i.e., when the compound contained only aluminum alkylphosphonate, foaming occurred during the manufacturing process and mold contamination occurred during the injection molding process. As is clear from Comparative Example 10, when the compound of Comparative Example 2 was used in combination with aluminum diethylphosphinate to form a flame retardant, i.e., when the compound did not contain aluminum phosphite and water of crystallization, mold contamination occurred during the injection molding process when used to flame-retardant high-temperature nylon. As is clear from Comparative Example 11, when the compound of Comparative Example 3 was used in combination with aluminum diethylphosphinate to form a flame retardant, i.e., when the compound did not contain aluminum hydrogen alkylphosphonate and aluminum phosphite, foaming occurred during the manufacturing process and mold contamination occurred during the injection molding process when used to flame-retardant high-temperature nylon. From the above, it was found that in order to achieve the effects of not causing foaming during the manufacturing process, not causing mold contamination during the injection molding process, and having good mechanical properties and flame-retardant properties when used to flame-retardant high-temperature nylon, it is necessary to simultaneously contain aluminum alkylphosphonate, aluminum hydrogen alkylphosphonate, aluminum phosphite, and water of crystallization in the compound and then use it in combination with aluminum diethylphosphinate to form a flame retardant.

[0054] Obviously, the above-described embodiments of the present invention are merely examples for clearly explaining the present invention, and do not limit the embodiments of the present invention. Those skilled in the art can make various other changes and modifications based on the above description. It is not necessary and impossible to comprehensively list all embodiments here. All modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention are intended to be included in the scope of protection of the claims of the present invention.

Claims

1. 1. An alkylphosphonic acid compound, characterized in that the structural formula of said compound is represented by formula (I): (I) (In formula (I), R is ethyl, x is 2.6 to 2.98, y is 0.01 to 0.39, z is 0.01 to 0.10, and m is 1.0 to 2.0.)

2. The compound according to claim 1, wherein the particle size D50 of the compound is 1 to 100 μm.

3. The compound according to claim 1, wherein the content of sodium sulfate in the compound is 100 to 5000 ppm.

4. A method for producing the compound of claim 1, comprising the steps of: The method includes the steps of: mixing an alkyl phosphonate and a phosphite, subjecting the mixture to a metathesis reaction with an aqueous aluminum salt solution, and then sequentially carrying out precipitation, filtration, washing, and drying at 105-120°C to obtain a compound, wherein the temperature of the metathesis reaction is 60-130°C; A manufacturing method characterized by:

5. 5. The method for producing the compound according to claim 4, wherein the aluminum salt solution is an aqueous solution of aluminum sulfate or aluminum chloride.

6. A first method in which an alkylphosphonic acid diester is hydrolyzed under basic conditions to obtain an alkylphosphonate; and a second method comprising: a step S1 of reacting phosphorous acid in an aqueous solution with gaseous ethylene in the presence of an initiator to obtain an alkylphosphonic acid; and a step S2 of reacting the alkylphosphonic acid with an equimolar amount of a basic solution to obtain an alkylphosphonate; 5. The method for producing the compound according to claim 4, wherein the alkylphosphonate is produced by any one of the following methods.

7. 7. The method for producing a compound according to claim 6, wherein in step S2, the basic solution is an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide.

8. Use of the compound according to any one of claims 1 to 3 as a flame retardant synergist for aluminium diethylphosphinate.

9. A composition comprising 1 to 7 parts by weight of a compound according to any one of claims 1 to 3 and 12 to 19 parts by weight of aluminum diethylphosphinate.

10. 10. Use of the composition of claim 9 as a flame retardant in flame retarding PA66, PA6, and high temperature nylon.

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