Preparation method of high thermal decomposition temperature tcpp flame retardant

Abstract

The application discloses a preparation method of a high-thermal-decomposition-temperature TCPP flame retardant, and particularly relates to controlling the content of dichlorophosphoric acid in raw material phosphorus oxychloride to be 10-200 ppm, and making the raw material phosphorus oxychloride react with propylene oxide to generate the TCPP flame retardant. The TCPP flame retardant with greatly improved thermal decomposition temperature can be prepared through the method.

Description

Technical Field

[0001] This invention relates to a method for preparing a flame retardant, and more particularly to a method for preparing a high thermal decomposition temperature TCPP flame retardant. Background Technology

[0002] Flame retardants are classified into three main categories: organohalogen flame retardants, organophosphorus flame retardants, and inorganic flame retardants. Organophosphorus flame retardants, due to their advantages such as high efficiency, low toxicity, low smoke, and low corrosiveness, are becoming the main application direction in the future.

[0003] Thermal decomposition temperature is an important reference indicator for evaluating the flame-retardant effect of flame retardants. If the thermal decomposition temperature of a flame retardant is too low, it will decompose and produce harmful gases when the material is exposed to high temperatures, thus accelerating combustion. Therefore, increasing the thermal decomposition temperature of a flame retardant is beneficial for expanding the downstream applications of the material.

[0004] TCPP flame retardant (tris(2-chloropropyl) phosphate), as a representative of low-halogen environmentally friendly flame retardants, boasts high flame retardant efficiency and also possesses plasticizing, moisture-proofing, and antistatic properties. It can be widely used in the flame retardancy of rigid or flexible polyurethane foams, polyvinyl chloride, phenolic resins, acrylic resins, as well as rubber and coatings. Patents CN103408584B, CN102887917B, and CN112209964B have reported a general industrial preparation method for TCPP, namely, the synthesis of TCPP from phosphorus oxychloride and propylene oxide under the action of a Lewis acid catalyst; the synthetic route is relatively mature.

[0005] However, through thermogravimetric analysis of multiple commercially available TCPP products, it was found that the thermal decomposition temperature of commercially available TCPP products is basically between 270-280℃, which cannot meet the application requirements for higher flame retardant performance, thus greatly limiting its application in specific fields. Summary of the Invention

[0006] To address the above technical problems, this invention proposes a method for preparing a TCPP flame retardant with a high thermal decomposition temperature. This method allows for the production of TCPP flame retardants with significantly increased thermal decomposition temperatures, thereby broadening their application areas.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a high thermal decomposition temperature TCPP flame retardant involves controlling the content of dichlorophosphoric acid in the raw material phosphorus oxychloride to be 10-200 ppm and reacting it with propylene oxide to generate the TCPP flame retardant.

[0009] The applicant's research revealed that, due to the reactive nature of phosphorus oxychloride, it generates a certain amount of dichlorophosphoric acid (as shown in Formula I) upon contact with trace amounts of water. In actual industrial production, the manufacturing, packaging, transportation, and storage of phosphorus oxychloride inevitably involve contact with small amounts of moisture; therefore, approximately 0.05 wt% to 0.1 wt% of dichlorophosphoric acid can be detected in commercially available phosphorus oxychloride.

[0010]

[0011] Further in-depth research by the inventors revealed that the content of dichlorophosphoric acid in phosphorus oxychloride affects the thermal decomposition temperature of the TCPP flame retardant. By controlling the content of dichlorophosphoric acid within the range of 10-200 ppm, the thermal decomposition temperature of the TCPP flame retardant can be effectively increased, thereby improving its thermal stability and making it suitable for applications with higher flame retardancy requirements.

[0012] As a method for controlling the dichlorophosphoric acid content in phosphorus oxychloride, distillation is preferred, but not limited to. Alternatively, column chromatography, chemisorption, and other methods can be used to control the dichlorophosphoric acid content in the raw material phosphorus oxychloride. As long as the dichlorophosphoric acid content is controlled within the required range, this invention can be achieved. Therefore, this invention does not limit the method for controlling the dichlorophosphoric acid content in phosphorus oxychloride.

[0013] Specifically, as a feasible distillation method provided by the present invention, it is preferably carried out at a bottom temperature of 50-100°C, a vacuum degree of 15-90 kPaA, and a reflux ratio of (1-5):1.

[0014] In a preferred embodiment of the present invention, the content of dichlorophosphoric acid in the raw material phosphorus oxychloride is 20-100 ppm.

[0015] In a preferred embodiment of the invention, the reaction is carried out in the presence of a Lewis acid catalyst;

[0016] Preferably, the Lewis acid catalyst is selected from aluminum trichloride and / or titanium tetrachloride.

[0017] In a preferred embodiment of the present invention, the amount of the Lewis acid catalyst, in molar terms, is 0.01-0.1 times, preferably 0.02-0.08 times, the molar amount of the raw material phosphorus oxychloride.

[0018] In a preferred embodiment of the present invention, the molar ratio of the raw material phosphorus oxychloride and propylene oxide is 1:(3.01-3.50), preferably 1:(3.01-3.10).

[0019] In a preferred embodiment of the present invention, the reaction temperature is 30-80°C, preferably 40-60°C.

[0020] In a preferred embodiment of the present invention, during the reaction process, propylene oxide is added dropwise to phosphorus oxychloride for mixing and reaction; after the addition is completed, the reaction is kept at a constant temperature until the conversion is complete.

[0021] In a preferred embodiment of the invention, the reaction is carried out in a dry, inert gas atmosphere, preferably in a nitrogen atmosphere, wherein the water content in the nitrogen is ≤3 ppm.

[0022] This invention aims to reduce the generation of hydroxyl radicals at high temperatures by controlling the content of dichlorophosphoric acid in phosphorus oxychloride, thereby increasing the thermal decomposition temperature of TCPP flame retardant. This approach is beneficial for expanding the downstream application areas of the product. Detailed Implementation

[0023] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0024] The analytical and experimental methods used in this invention are as follows:

[0025] TCPP and dichlorophosphoric acid content analysis: Gas chromatography (GC) was used. Instrument: Agilent 7980.

[0026] Table 1. Gas Chromatography Analysis Conditions

[0027]

[0028]

[0029] Test of TCPP thermal decomposition temperature: Thermogravimetric analysis was used and the conditions in Table 2 were applied. Instrument: Diamond Perkin Elmer thermogravimetric analyzer.

[0030] Table 2. Thermogravimetric Analysis Conditions

[0031] Heating rate / °C / min 20

[0032] Unless otherwise specified, all raw materials and reagents used in the embodiments of this invention were obtained through commercially available sources. Specifically, aluminum trichloride (99.9%) was from Aladdin; titanium tetrachloride (99.9%) was from Aladdin; and propylene oxide (99.9%) was from Wanhua Chemical.

[0033]

Example 1

[0034] (1) Prepare the raw materials:

[0035] Phosphorus oxychloride (containing 730 ppm dichlorophosphoric acid) was purified by distillation. The reboiler temperature was controlled at 72℃, the vacuum degree at 31 kPaA, and the reflux ratio at 3:1. The purified phosphorus oxychloride was obtained, and the content of dichlorophosphoric acid was 112 ppm. The purity of the phosphorus oxychloride product was ≥99.5%.

[0036] (2) Preparation of TCPP

[0037] 154.1g of phosphorus oxychloride obtained from the above distillation and 6.67g of aluminum trichloride were added to a four-necked flask and stirred thoroughly until homogeneous. The reaction solution was heated to 50°C, and 177.3g of propylene oxide was slowly added dropwise to the flask. The reaction temperature was controlled at 50°C during the dropwise addition. After the propylene oxide was added, the reaction was continued at the temperature for 3 hours to obtain 338.1g of crude TCPP.

[0038] 33.8 g of deionized water was added to crude TCPP, and the pH of the reaction solution was adjusted to 9 with 5 wt% sodium hydroxide aqueous solution. The mixture was stirred thoroughly at 50 °C for 0.5 h. After filtration, the reaction solution was allowed to stand and separate phases. 338.1 g of deionized water was added to the organic phase, and the mixture was stirred thoroughly at 50 °C for 0.5 h. After standing and separating phases, the organic phase was dehydrated at 100 °C under a vacuum of 3 kPaA for 1 h to obtain pure TCPP. The TCPP content and thermogravimetric analysis results are listed in Table 1.

[0039]

Example 2

[0040] (1) Prepare the raw materials:

[0041] Phosphorus oxychloride (containing 530 ppm dichlorophosphoric acid) was purified by distillation. The reboiler temperature was controlled at 96℃, the vacuum degree at 73 kPaA, and the reflux ratio at 1:1. The purified phosphorus oxychloride was obtained, and the content of dichlorophosphoric acid was 135 ppm. The purity of the phosphorus oxychloride product was ≥99.5%.

[0042] (2) Preparation of TCPP

[0043] 154.1g of phosphorus oxychloride obtained from the above distillation and 1.33g of aluminum trichloride were added to a four-necked flask and stirred thoroughly until homogeneous. The reaction solution was heated to 80°C, and 203.5g of propylene oxide was slowly added dropwise to the flask. The reaction temperature was controlled at 80°C during the dropwise addition. After the propylene oxide was added, the reaction was continued at this temperature for 3 hours to obtain 358.9g of crude TCPP.

[0044] 35.9 g of deionized water was added to crude TCPP, and the pH of the reaction solution was adjusted to 9 with 5 wt% sodium hydroxide aqueous solution. The mixture was stirred thoroughly at 50 °C for 0.5 h. After filtration, the reaction solution was allowed to stand and separate phases. 358.9 g of deionized water was added to the organic phase, and the mixture was stirred thoroughly at 50 °C for 0.5 h. After standing and separating phases, the organic phase was dehydrated at 100 °C under a vacuum of 3 kPaA for 1 h to obtain pure TCPP. The TCPP content and thermogravimetric analysis results are listed in Table 1.

[0045]

Example 3

[0046] (1) Prepare the raw materials:

[0047] Phosphorus oxychloride (containing 982 ppm dichlorophosphoric acid) was purified by distillation. The reboiler temperature was controlled at 56℃, the vacuum degree at 15 kPaA, and the reflux ratio at 4:1. The purified phosphorus oxychloride was obtained, and the content of dichlorophosphoric acid was 68 ppm. The purity of the phosphorus oxychloride product was ≥99.5%.

[0048] (2) Preparation of TCPP

[0049] 154.1g of phosphorus oxychloride obtained from the above distillation and 13.35g of aluminum trichloride were added to a four-necked flask and stirred thoroughly until homogeneous. The reaction solution was heated to 30°C, and 175.0g of propylene oxide was slowly added dropwise to the flask. The reaction temperature was controlled at 30°C during the dropwise addition. After the propylene oxide was added, the reaction was continued at the temperature for 3 hours to obtain 342.4g of crude TCPP.

[0050] 34.2 g of deionized water was added to crude TCPP, and the pH of the reaction solution was adjusted to 9 with 5 wt% sodium hydroxide aqueous solution. The mixture was stirred thoroughly at 50 °C for 0.5 h. After filtration, the reaction solution was allowed to stand and separate phases. 342.4 g of deionized water was added to the organic phase, and the mixture was stirred thoroughly at 50 °C for 0.5 h. After standing and separating phases, the organic phase was dehydrated at 100 °C under a vacuum of 3 kPaA for 1 h to obtain pure TCPP. The TCPP content and thermogravimetric analysis results are listed in Table 1.

[0051]

Example 4

[0052] (1) Prepare the raw materials:

[0053] Phosphorus oxychloride (containing 730 ppm dichlorophosphoric acid) was purified by distillation. The reboiler temperature was controlled at 72℃, the vacuum degree at 31 kPaA, and the reflux ratio at 5:1. The purified phosphorus oxychloride was obtained, and the content of dichlorophosphoric acid was 12 ppm. The purity of the phosphorus oxychloride product was ≥99.5%.

[0054] (2) Preparation of TCPP

[0055] 154.1g of phosphorus oxychloride obtained from the above distillation and 3.80g of titanium tetrachloride were added to a four-necked flask and stirred thoroughly until homogeneous. The reaction solution was heated to 60°C, and 179.1g of propylene oxide was slowly added dropwise to the flask. The reaction temperature was controlled at 60°C during the dropwise addition. After the propylene oxide was added, the reaction was continued at this temperature for 3 hours to obtain 336.9g of crude TCPP.

[0056] 33.7 g of deionized water was added to crude TCPP, and the pH of the reaction solution was adjusted to 9 with 5 wt% sodium hydroxide aqueous solution. The mixture was stirred thoroughly at 50 °C for 0.5 h. After filtration, the reaction solution was allowed to stand and separate phases. 336.9 g of deionized water was added to the organic phase, and the mixture was stirred thoroughly at 50 °C for 0.5 h. After standing and separating phases, the organic phase was dehydrated at 100 °C under a vacuum of 3 kPaA for 1 h to obtain pure TCPP. The TCPP content and thermogravimetric analysis results are listed in Table 1.

[0057]

Example 5

[0058] (1) Prepare the raw materials:

[0059] Phosphorus oxychloride (containing 730 ppm dichlorophosphoric acid) was purified by distillation. The temperature of the distillation column was controlled at 72℃, the vacuum degree was 31 kPaA, and the reflux ratio was 1:1. The purified phosphorus oxychloride was obtained, and the content of dichlorophosphoric acid was 198 ppm. The purity of the phosphorus oxychloride product was ≥99.5%.

[0060] (2) Preparation of TCPP

[0061] 154.1g of phosphorus oxychloride obtained from the above distillation and 10.68g of aluminum trichloride were added to a four-necked flask and stirred thoroughly until homogeneous. The reaction solution was heated to 40°C, and 175.6g of propylene oxide was slowly added dropwise to the flask. The reaction temperature was controlled at 40°C during the dropwise addition. After the propylene oxide was added, the reaction was continued at this temperature for 3 hours to obtain 340.3g of crude TCPP.

[0062] Add 34.0 g of deionized water to crude TCPP, adjust the pH of the reaction solution to 9 with 5 wt% sodium hydroxide aqueous solution, and stir thoroughly at 50 °C for 0.5 h. After filtration, allow the reaction solution to stand and separate phases. Add 340.3 g of deionized water to the organic phase, stir thoroughly at 50 °C for 0.5 h, allow to stand and separate phases, and dehydrate the organic phase at 100 °C under a vacuum of 3 kPaA for 1 h to obtain pure TCPP. The TCPP content and thermogravimetric analysis results are listed in Table 1.

[0063] Comparative Example 1

[0064] TCPP was prepared using essentially the same method as in Example 1, except that the raw material phosphorus oxychloride was not pretreated in any way, i.e., the content of dichlorophosphoric acid in the raw material was kept at 730 ppm.

[0065] Comparative Example 2

[0066] TCPP was prepared using essentially the same method as in Example 1, except that the content of dichlorophosphoric acid in the raw material phosphorus oxychloride was controlled at 252 ppm.

[0067] Comparative Example 3

[0068] TCPP was prepared using essentially the same method as in Example 1, except that the content of dichlorophosphoric acid in the raw material phosphorus oxychloride was controlled at 6 ppm.

[0069] Table 3. Experimental results of Examples 1-5 and Comparative Examples 1-3

[0070]

[0071]

[0072] The experimental results of Examples 1-5 show that controlling the dichlorophosphoric acid content in the raw materials within the range proposed in this invention can yield TCPP flame retardants with significantly increased thermal decomposition temperatures. Furthermore, comparing the experimental results of Example 1 and Comparative Example 3 reveals that when the dichlorophosphoric acid content in phosphorus oxychloride is further reduced to 7 ppm, the thermal decomposition temperature of the TCPP product does not increase significantly, but the energy consumption for raw material processing increases significantly, which is detrimental to industrial economics. Therefore, the dichlorophosphoric acid content is preferably controlled above 10 ppm.

[0073] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a high thermal decomposition temperature TCPP flame retardant, characterized in that, The content of dichlorophosphoric acid in the raw material phosphorus oxychloride is controlled at 10-200 ppm, and it is reacted with propylene oxide to generate TCPP flame retardant.

2. The preparation method of the high thermal decomposition temperature TCPP flame retardant according to claim 1, characterized in that, The content of dichlorophosphoric acid in the raw material phosphorus oxychloride is 20-100 ppm.

3. The method for preparing the high thermal decomposition temperature TCPP flame retardant according to claim 1, characterized in that, The reaction was carried out in the presence of a Lewis acid catalyst.

4. The preparation method of the high thermal decomposition temperature TCPP flame retardant according to claim 3, characterized in that, The Lewis acid catalyst is selected from aluminum trichloride and / or titanium tetrachloride.

5. The method for preparing the high thermal decomposition temperature TCPP flame retardant according to claim 3, characterized in that, The amount of the Lewis acid catalyst used, in molar terms, is 0.01-0.1 times the molar amount of the raw material phosphorus oxychloride.

6. The method for preparing the high thermal decomposition temperature TCPP flame retardant according to claim 5, characterized in that, The amount of the Lewis acid catalyst used, in molar terms, is 0.02-0.08 times the molar amount of the raw material phosphorus oxychloride.

7. The method for preparing the high thermal decomposition temperature TCPP flame retardant according to any one of claims 1-6, characterized in that, The molar ratio of the raw materials phosphorus oxychloride and propylene oxide is 1:(3.01-3.50).

8. The method for preparing the high thermal decomposition temperature TCPP flame retardant according to claim 7, characterized in that, The molar ratio of the raw materials phosphorus oxychloride and propylene oxide is 1:(3.01-3.10).

9. The method for preparing the high thermal decomposition temperature TCPP flame retardant according to any one of claims 1-6, characterized in that, The reaction temperature is 30-80℃.

10. The method for preparing the high thermal decomposition temperature TCPP flame retardant according to claim 9, characterized in that, The reaction temperature is 40-60℃.

11. The method for preparing the high thermal decomposition temperature TCPP flame retardant according to any one of claims 1-6, characterized in that, In the reaction process, propylene oxide is added dropwise to phosphorus oxychloride for mixing and reaction; after the addition is completed, the reaction is kept at a constant temperature until the conversion is complete.

12. The method for preparing the high thermal decomposition temperature TCPP flame retardant according to any one of claims 1-6, characterized in that, The reaction was carried out in a dry, inert gas atmosphere.

13. The method for preparing the high thermal decomposition temperature TCPP flame retardant according to claim 12, characterized in that, The reaction is carried out under a nitrogen atmosphere, and the water content in the nitrogen is ≤3ppm.

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