A method for preparing antimony polyphosphate by solid-phase low-temperature rapid reaction

Abstract

A method for preparing antimony polyphosphate by solid-phase low-temperature rapid reaction, comprising the following steps: (1) putting the uniformly mixed raw materials and polycondensing agent into a microwave reactor and heating up for solid-phase synthesis reaction; (2) continuously raising the temperature for solid-phase polycondensation reaction to obtain the product; the raw materials mainly consist of antimony trioxide and ammonium polyphosphate; the polycondensing agent is phosphorus pentoxide and / or polyphosphoric acid. The reaction of the present invention has low reaction temperature, short reaction time, fast reaction speed, energy conservation and environmental protection, and low preparation cost; through polycondensation reaction, antimony phosphate molecules form long molecular chain compounds - antimony polyphosphate, solving or greatly reducing the moisture absorption problem of antimony phosphate.

Description

Technical Field

[0001] The present invention relates to a method for preparing antimony polyphosphate, and more particularly to a method for preparing antimony polyphosphate by a solid-phase low-temperature process. Background Art

[0002] The safety of antimony phosphate has passed the SGS certification and complies with multiple environmental protection requirements such as RoHS, REACH, and PAHs. However, the high hygroscopicity of antimony phosphate greatly hinders its application in the flame retardant field. The existing methods for preparing antimony phosphate are mainly solvothermal reaction methods, in which an antimony salt is mixed with a phosphate or phosphoric acid in a solvent (organic solvent or inorganic solvent) and then reacted in an autoclave under solvothermal conditions of 150-180°C for 6-10 h. According to different antimony salts and solvents, various antimony phosphate products with different morphologies are obtained, but the products obtained by these methods are not suitable for use as flame retardants.

[0003] Antimony polyphosphate [〔Sb(PO3)3〕n] is a new type of phosphorus-antimony composite flame retardant synergist, which can replace about 45-60% of antimony trioxide. When combined with halogens, it has good flame retardant effects, a high oxygen index, and forms a new three-dimensional flame retardant system of gas-solid phase co-action of phosphorus-halogen, antimony-halogen, and phosphorus-antimony-halogen during the combustion of flame retardant materials. It greatly improves the deficiencies of pure phosphorus-based flame retardants that mainly rely on single solid-phase flame retardancy and have a large dosage, resulting in an impact on the physical properties of flame retardant materials. It also significantly improves the defects of antimony-halogen-based flame retardants, such as the high proportion of heavy metal antimony, the cost of flame retardant materials, and the large amount of smoke and "smoke toxicity" during the flame retardant process. It achieves high-efficiency flame retardancy while reducing antimony, suppressing smoke, reducing toxicity, and lowering the cost of flame retardant materials.

[0004] There are few methods for preparing antimony polyphosphate. CN 101531356 A discloses a method for preparing antimony polyphosphate. This invention uses antimony trioxide and ammonium dihydrogen phosphate as raw materials, and phosphorus pentoxide or polyphosphoric acid as a polycondensation agent. It undergoes a solid-phase reaction at 220°C for 120 min, and then reacts at 480°C for 240 min to obtain antimony polyphosphate with an average degree of polymerization of 47. The moisture absorption rate of this antimony polyphosphate is ≥1.2% after being exposed for 24 h. If the exposure time is extended, its moisture absorption rate will increase significantly. The degree of polymerization needs to be further improved. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the above-mentioned defects existing in the prior art and provide a method for preparing high-polymer antimony polyphosphate by a solid-phase low-temperature rapid reaction with a low moisture absorption rate of the product.

[0006] The technical solution adopted by the present invention to solve its technical problems is as follows: A method for preparing high-polymer antimony polyphosphate by a solid-phase low-temperature rapid reaction, comprising the following steps:

[0007] (1) Put the uniformly mixed raw materials and polycondensing agent into a microwave reactor, heat up and carry out solid-phase synthesis reaction to obtain a small molecule antimony phosphate (SbPO4) product;

[0008] (2) Continue to raise the temperature and carry out solid-phase polycondensation reaction to complete;

[0009] The raw materials mainly consist of antimony trioxide and ammonium polyphosphate;

[0010] The polycondensing agent is phosphorus pentoxide and / or polyphosphoric acid.

[0011] Ammonium polyphosphate appears as a white powder, has little hygroscopicity in the air, has a relatively high phosphorus content, and is easy to mix with other powder substances. It overcomes the deficiencies of ammonium dihydrogen phosphate used in the prior art, such as low phosphorus content, easy hygroscopicity, etc., which cause an increase in dosage and easy caking during the mixing process with antimony trioxide, resulting in uneven mixing.

[0012] During the solid-phase thermal reaction of antimony trioxide and ammonium polyphosphate in a microwave field, first, low-temperature catalysis is carried out on the thermal decomposition of ammonium polyphosphate to release ammonia (NH3), water vapor (H2O), metaphosphoric acid and pyrophosphoric acid. The latter reacts chemically with antimony trioxide to form antimony phosphate, and then through polycondensation, long-chain and high-molecular-weight ammonium polyphosphate is prepared. Zhou You and others from Beijing Institute of Technology have conducted relatively in-depth research on the action mechanism of transition metal oxides and ammonium polyphosphate. However, due to the relatively complex process, they only elaborated theoretically, and there is no data reporting the reaction equation of the process.

[0013] Using the above technical solution, the reaction temperature is low, the reaction time is short, the reaction speed is fast, it is energy-saving and environmentally friendly, and the preparation cost is low; the product is a high-polymer ammonium polyphosphate [〔Sb(PO3)3〕n] product with white color (whiteness ≥ 90%), moisture absorption rate ≤ 1.0%, and content ≥ 98% and long molecular chains.

[0014] Preferably, the ammonium polyphosphate contains more than 30% phosphorus. The phosphorus content of ammonium polyphosphate sold on the market is generally between 30% and 32%, and it can be used directly.

[0015] By adopting the above technical solution, a better preparation effect is achieved.

[0016] Preferably, in the raw materials, the mass ratio of ammonium polyphosphate to antimony trioxide is 1∶0.3 - 0.6, and more preferably 1∶0.35 - 0.55.

[0017] By adopting the above technical solution, a better preparation effect is achieved.

[0018] Preferably, the mass ratio of the polycondensing agent to antimony trioxide is 0.1 - 0.4∶1, and more preferably 0.2 - 0.3∶1.

[0019] By adopting the above technical solution, a better preparation effect is achieved.

[0020] Preferably, in step (1), the temperature of the solid-phase synthesis reaction is 130 - 180°C; more preferably 150 - 180°C.

[0021] By adopting the above technical solution, a better preparation effect is achieved.

[0022] Preferably, in step (1), the time of the solid-phase synthesis reaction is 40 - 80 minutes; more preferably 40 - 60 minutes.

[0023] By adopting the above technical solution, a better preparation effect is achieved.

[0024] Preferably, in step (1), the solid-phase synthesis reaction is carried out under a slightly negative pressure condition of 0.001 - 0.003 MPa; more preferably 0.001 - 0.002 MPa.

[0025] By adopting the above technical solution, a better preparation effect is achieved.

[0026] Preferably, in step (2), the temperature of the solid-phase polycondensation reaction is 300 - 380°C; more preferably 350 - 380°C.

[0027] By adopting the above technical solution, a better preparation effect is achieved.

[0028] Preferably, in step (2), the time of the solid-phase polycondensation reaction is 90 - 180 minutes; more preferably 150 - 180 min.

[0029] By adopting the above technical solution, a better preparation effect is achieved.

[0030] Preferably, in step (2), the solid-phase polycondensation reaction is carried out under a slightly negative pressure condition of 0.001 - 0.003 MPa; more preferably 0.001 - 0.002 MPa.

[0031] By adopting the above technical solution, a better preparation effect is achieved.

[0032] The slightly negative pressure is beneficial to discharging the ammonia gas and water vapor escaping during the pyrolysis of ammonium polyphosphate, facilitating the reaction in the microwave oven and the formation and polycondensation of antimony phosphate. At the same time, it can also absorb the escaping ammonia gas, eliminating the impact of the escaping ammonia gas on the environment.

[0033] Advantages of the present invention:

[0034] (1) The reaction of the present invention has a low temperature, a short reaction time, a fast reaction speed, is energy-saving and environmentally friendly, and has a low preparation cost;

[0035] (2) By means of a polycondensation reaction, the antimony phosphate molecules form a long molecular chain compound, namely, high-polymer antimony phosphate, solving or greatly alleviating the hygroscopic problem of antimony phosphate.

[0036] (3) The product is high-polymer antimony phosphate [〔Sb(PO3)3〕n] with a long molecular chain, which is white (whiteness ≥ 90%), has a moisture absorption rate ≤ 1.0%, and a content ≥ 98%; the obtained high-polymer antimony phosphate has a large degree of polymerization and a low moisture absorption rate, and is a high-polymer antimony phosphate product applicable to the flame retardancy of various polymer polymers. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is an X-ray diffraction pattern measured after the antimony polyphosphate prepared in Example 1 was exposed to the air for 72 h.

[0038] Figure 2 It is an X-ray diffraction pattern measured after the antimony polyphosphate prepared in Example 2 was exposed to the air for 56 h.

[0039] Figure 3 It is an X-ray diffraction pattern measured after the antimony polyphosphate prepared in Example 3 was exposed to the air for 72 h.

[0040] Figure 4 It is an X-ray diffraction pattern measured after the antimony polyphosphate prepared in Example 4 was exposed to the air for 48 h.

[0041] Figure 5 It is an X-ray diffraction pattern measured after the antimony polyphosphate prepared in Example 5 was exposed to the air for 72 h.

[0042] Figure 6 It is an X-ray diffraction pattern measured after the antimony polyphosphate prepared in the comparative example was exposed to the air for 48 h. DETAILED DESCRIPTION OF THE INVENTION

[0043] The present invention will be further described below in conjunction with the examples and the drawings.

[0044] The raw materials used in the examples of the present invention are all obtained through conventional commercial channels. Example 1

[0045] The method for preparing high-polymer antimony phosphate by solid-phase low-temperature rapid reaction in this example includes the following steps:

[0046] Weigh 80 g of ammonium polyphosphate (APP) (phosphorus content 31%), 35 g of antimony trioxide, and 7.2 g of phosphorus pentoxide according to the mass ratio of ammonium polyphosphate to antimony trioxide of 1:0.438 and the mass ratio of the polycondensing agent (phosphorus pentoxide) to antimony trioxide of 0.206:1. Mix them uniformly at high speed in a high-speed mixer with a crushing function. Then put the uniformly mixed material into a mullite corundum crucible with a cover and place it in a microwave reactor equipped with a microwave output power of 0 - 3 kw (automatically adjustable) and a micro-negative pressure device interface. Set the solid-phase synthesis reaction temperature at 180 °C and the solid-phase synthesis reaction time at 60 min; set the solid-phase polycondensation reaction temperature at 380 °C and the solid-phase polycondensation reaction time at 180 min. When the temperature rises to 100 °C, open the valve of the negative pressure device and the ejector pump, and adjust the vacuum degree to 0.0015 MPa. After the reaction is completed, high-polymer antimony phosphate is obtained.

[0047] After high-speed pulverization, it is loaded into an open ceramic crucible and exposed to the air for 72 h, and then samples are taken for physical and chemical analysis. The analysis results are as follows:

[0048] Moisture absorption rate: 0.62 %;

[0049] Whiteness: ≥91%;

[0050] Degree of polymerization: 61;

[0051] Content of antimony phosphate: 98.13%.

[0052] The analysis results of XRD are shown in Figure 1 , and all the peaks marked with "o" above the peak numbers are the peaks of antimony phosphate. It can be clearly seen from the figure that all the peaks are antimony phosphate, and the bottom of the peaks is relatively flat and basically on the same plane, indicating that the moisture absorption rate of the product is very low. Example 2

[0053] The method for preparing high-polymer antimony phosphate by solid-phase low-temperature rapid reaction in this example includes the following steps:

[0054] Weigh 78 g of ammonium polyphosphate (APP) (phosphorus content 31%), 38 g of antimony trioxide, and 8.2 g of phosphorus pentoxide according to the mass ratio of ammonium polyphosphate to antimony trioxide of 1:0.487 and the mass ratio of the polycondensing agent (phosphorus pentoxide) to antimony trioxide of 0.216:1. Mix them uniformly at high speed in a high-speed mixer with a crushing function. Then put the uniformly mixed material into a mullite corundum crucible with a cover and place it in a microwave reactor equipped with a microwave output power of 0 - 3 kw (automatically adjustable) and a micro-negative pressure device interface. Set the solid-phase synthesis reaction temperature at 160 °C and the solid-phase synthesis reaction time at 60 min; set the solid-phase polycondensation reaction temperature at 380 °C and the solid-phase polycondensation reaction time at 150 min. When the temperature rises to 100 °C, open the valve of the negative pressure device and the ejector pump, and adjust the vacuum degree to 0.0015 MPa. After the reaction is completed, high-polymer antimony phosphate is obtained.

[0055] After being pulverized at high speed, it is loaded into an open ceramic crucible and sampled for physical and chemical analysis after being exposed to the air for 56 h. The analysis results are as follows:

[0056] Moisture absorption rate: 1.23%;

[0057] Whiteness: ≥90%;

[0058] Degree of polymerization: 48;

[0059] Antimony phosphate content: 98.06%.

[0060] The analysis results of XRD are shown in Figure 2 , and the peaks marked with "★" above the peak numbers are all the peaks of antimony phosphate. It can be clearly seen from the figure that all the peaks are antimony phosphate; the bottom of the peaks Figure 1 has a certain fluctuation and is basically not on the same plane, indicating that the moisture absorption rate of the product in Example 2 has a slight increase compared with that in Example 1. Example 3

[0061] The method for preparing high-polymer antimony phosphate by solid-phase low-temperature rapid reaction in this example includes the following steps:

[0062] Weigh 70 g of ammonium polyphosphate (APP) (phosphorus content 32%), 35 g of antimony trioxide, and 7.2 g of phosphorus pentoxide according to the mass ratio of ammonium polyphosphate to antimony trioxide of 1:0.5 and the mass ratio of the polycondensing agent (phosphorus pentoxide) to antimony trioxide of 0.206:1. Mix them evenly at high speed in a high-speed mixer with a crushing function. Then put the evenly mixed materials into a mullite corundum crucible with a cover and place it in a microwave reactor equipped with a microwave output power of 0 - 3 kw (automatically adjustable) and a micro-negative pressure device interface. Set the solid-phase synthesis reaction temperature at 180 °C and the solid-phase synthesis reaction time at 50 min; set the solid-phase polycondensation reaction temperature at 380 °C and the solid-phase polycondensation reaction time at 150 min. When the temperature rises to 100 °C, open the valve of the negative pressure device and the ejector pump, and adjust the vacuum degree to 0.0015 MPa. After the reaction is completed, high-polymer antimony phosphate is obtained.

[0063] After high-speed crushing, it is put into an open ceramic crucible and sampled for physical and chemical analysis after being exposed to the air for 72 h. The analysis results are as follows:

[0064] Moisture absorption rate: 0.87%;

[0065] Whiteness: ≥90%;

[0066] Degree of polymerization: 55;

[0067] Content of antimony phosphate: 98.08%.

[0068] The analysis results of XRD are shown in Figure 3 , and all the peaks marked with "o" above the peak numbers are the peaks of antimony phosphate. It can be clearly seen from the figure that all the peaks are antimony phosphate, and the bottom of the peaks has Figure 1 slight fluctuations, indicating that the moisture absorption rate of the product in this example is slightly higher than that of Example 1. Example 4

[0069] The method for preparing high-polymer antimony phosphate by solid-phase low-temperature rapid reaction in this example includes the following steps:

[0070] Weigh 85 g of ammonium polyphosphate (APP) (phosphorus content: 32%), 35 g of antimony trioxide, and 7.6 g of phosphorus pentoxide according to the mass ratio of ammonium polyphosphate to antimony trioxide of 1:0.412 and the mass ratio of the polycondensing agent (phosphorus pentoxide) to antimony trioxide of 0.217:1. Mix them uniformly at high speed in a high-speed mixer with a crushing function. Then, put the uniformly mixed material into a mullite corundum crucible with a cover and place it in a microwave reactor equipped with a microwave output power of 0 - 3 kw (automatically adjustable) and a micro-negative pressure device interface. Set the solid-phase synthesis reaction temperature at 180 °C and the solid-phase synthesis reaction time at 60 min; set the solid-phase polycondensation reaction temperature at 380 °C and the solid-phase polycondensation reaction time at 180 min. When the temperature rises to 100 °C, open the valves of the negative pressure device and the ejector pump, and adjust the vacuum degree to 0.0015 MPa. After the reaction is completed, high-polymer antimony phosphate is obtained.

[0071] After being pulverized at high speed, it is loaded into an open ceramic crucible and left exposed in the air for 48 h, and then samples are taken for physical and chemical analysis. The analysis results are as follows:

[0072] Moisture absorption rate: 0.58%;

[0073] Whiteness: ≥92%;

[0074] Degree of polymerization: 63;

[0075] Content of antimony phosphate: 98.28%.

[0076] The analysis results of XRD are shown in Figure 4 , and all the peaks marked with "o" above the peak numbers are the peaks of antimony phosphate. It can be clearly seen from the figure that all the peaks are those of antimony phosphate, and the bottoms of the peaks are relatively flat and basically on the same plane, indicating that the moisture absorption rate of the product is very low. Example 5

[0077] The method for preparing high-polymer antimony phosphate by solid-phase low-temperature rapid reaction in this example includes the following steps:

[0078] Weigh 90 g of ammonium polyphosphate (APP) (phosphorus content 32%), 35 g of antimony trioxide, and 8.2 g of phosphorus pentoxide according to the mass ratio of ammonium polyphosphate to antimony trioxide of 1:0.389 and the mass ratio of the polycondensing agent (phosphorus pentoxide) to antimony trioxide of 0.234:1. Mix them uniformly at high speed in a high-speed mixer with a crushing function. Then put the uniformly mixed material into a mullite corundum crucible with a cover and place it in a microwave reactor equipped with a microwave output power of 0 - 3 kw (automatically adjustable) and a micro-negative pressure device interface. Set the solid-phase synthesis reaction temperature at 150 °C and the solid-phase synthesis reaction time at 60 min; set the solid-phase polycondensation reaction temperature at 350 °C and the solid-phase polycondensation reaction time at 180 min. When the temperature rises to 100 °C, open the valve of the negative pressure device and the ejector pump, and adjust the vacuum degree to 0.0015 MPa. After the reaction is completed, high-polymer antimony phosphate is obtained.

[0079] After being pulverized at high speed, it is loaded into an open ceramic crucible and sampled for physical and chemical analysis after being exposed to the air for 72 h. The analysis results are as follows:

[0080] Moisture absorption rate: 0.89%;

[0081] Whiteness: ≥91%;

[0082] Degree of polymerization: 58;

[0083] Antimony phosphate content: 98.19%.

[0084] The analysis results of XRD are shown in Figure 5 , and all the peaks marked with "o" above the peak numbers are the peaks of antimony phosphate. It can be clearly seen from the figure that all the peaks are antimony phosphate, and the bottom of the peaks has Figure 1 slight fluctuations, indicating that the moisture absorption rate of the product is slightly higher than that of Example 4.

[0085] Comparative Example

[0086] The preparation method of this comparative example includes the following steps:

[0087] Weigh 90 g of ammonium dihydrogen phosphate (phosphorus content: 26.9%), 35 g of antimony trioxide, and 7.4 g of phosphorus pentoxide in the ratio of the mass ratio of ammonium dihydrogen phosphate to antimony trioxide being 1:0.389 and the mass ratio of the polycondensing agent (phosphorus pentoxide) to antimony trioxide being 0.211:1. Mix them uniformly at high speed in a high-speed mixer with a crushing function. Then put the uniformly mixed material into a mullite corundum crucible with a cover and place it in a microwave reactor equipped with a microwave output power of 0 - 3 kw (automatically adjustable) and a micro-negative pressure device interface. Set the solid-phase synthesis reaction temperature at 180 °C and the solid-phase synthesis reaction time at 60 min; set the solid-phase polycondensation reaction temperature at 380 °C and the solid-phase polycondensation reaction time at 180 min. When the temperature rises to 100 °C, open the valve of the negative pressure device and the ejector pump, and adjust the vacuum degree to 0.0015 MPa. After the reaction is completed, it is ready.

[0088] After being pulverized at high speed, it is loaded into an open ceramic crucible and left exposed in the air for 48 h, and then samples are taken for physical and chemical analysis. The analysis results are as follows:

[0089] Moisture absorption rate: 38.6%;

[0090] Whiteness: Unable to detect;

[0091] Degree of polymerization: 12;

[0092] Antimony phosphate content: 76.34%.

[0093] The analysis results of XRD are shown in Figure 6 , and the spectral peaks marked with "★" above the spectral peak numbers are all the spectral peaks of antimony phosphate. It can be clearly seen from the figure that some spectral peaks are not the peaks of antimony phosphate, indicating that the content of antimony phosphate is not high; the bottom of the spectral peaks in the figure Figures 1 to 5 has great changes and is completely not on the same plane, indicating that the hygroscopicity of the product is very high.

[0094] By comparing with Examples 1 - 5, it can be found that the degree of polymerization of the comparative example is lower and the moisture absorption rate is much higher. The product obtained from the comparative example is not suitable for use as a flame retardant.

Claims

1. A method for preparing antimony polyphosphate by solid-phase low-temperature rapid reaction, characterized in that, It includes the following steps: (1) Put the uniformly mixed raw materials and polycondensing agent into a microwave reaction furnace, heat up and carry out a solid-phase synthesis reaction; the temperature of the solid-phase synthesis reaction is 130-180 °C, and the time of the solid-phase synthesis reaction is 40-80 minutes; (2) Continue to raise the temperature and carry out a solid-phase polycondensation reaction to complete; the temperature of the solid-phase polycondensation reaction is 300-380 °C, and the time of the solid-phase polycondensation reaction is 90-180 minutes; The raw materials mainly consist of antimony trioxide and ammonium polyphosphate; the ammonium polyphosphate contains more than 30% phosphorus; The polycondensing agent is phosphorus pentoxide and / or polyphosphoric acid.

2. The method for preparing antimony polyphosphate by solid-phase low-temperature rapid reaction according to claim 1, characterized in that, In the raw materials, the mass ratio of ammonium polyphosphate to antimony trioxide is 1:0.3-0.

6.

3. The method for preparing antimony polyphosphate by solid-phase low-temperature rapid reaction according to claim 1 or 2, characterized in that The mass ratio of the polycondensing agent to antimony trioxide is 0.1-0.4:

1.

4. The method for preparing antimony polyphosphate by solid-phase low-temperature rapid reaction according to claim 1 or 2, characterized in that, In step (1), the solid-phase synthesis reaction is carried out under a slightly negative pressure condition of 0.001-0.003 MPa.

5. The method for preparing antimony polyphosphate by solid-phase low-temperature rapid reaction according to claim 1 or 2, characterized in that, In step (2), the solid-phase polycondensation reaction is carried out under a slightly negative pressure condition of 0.001-0.003 MPa.

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