A method for efficiently synthesizing resorcinol bis [di(2,6-dimethylphenyl) phosphate]

Abstract

The application discloses a method for efficiently synthesizing resorcinol bis[di(2,6-dimethylphenyl) phosphate], which comprises the following steps: in the presence of a MgCl2 catalyst, a first step reaction is completed by adding phosphorus oxychloride into sodium resorcinol in a reaction solvent; after the reaction, the reaction solution is subjected to solid-liquid separation, and the obtained intermediate solution is directly used in a next step; the intermediate solution is added dropwise into a mixed system of sodium 2,6-dimethylphenol, a MgCl2 catalyst and a reaction solvent, and a second step reaction is performed; after the reaction, the reaction solution is subjected to post-treatment, and resorcinol bis[di(2,6-dimethylphenyl) phosphate] is obtained. The application provides a simple and efficient synthesis method, and sodium resorcinol, phosphorus oxychloride and 2,6-dimethylphenol are used as raw materials; MgCl2 is used as a catalyst in the first step and the second step, and toluene is used as a reaction solvent; and resorcinol bis[di(2,6-dimethylphenyl) phosphate] is synthesized by a high-efficiency and high-yield one-pot method.

Description

Technical Field

[0001] This invention relates to a method for the efficient synthesis of resorcinol bis[bis(2,6-dimethylphenyl)phosphate]. Background Technology

[0002] Flame retardants are functional additives that impart flame-retardant properties to flammable polymers. They are primarily designed for flame retardancy in polymer materials and are widely used in flammable polymers such as plastics, rubber, and fibers. They are designed to meet the flame-retardant requirements of these materials. Plastics, in particular, require robust flame-retardant properties for applications in transportation, construction, electrical equipment, aerospace, and other fields. The use of flame retardants generally requires meeting the following conditions: they should not reduce the physical properties of the polymer material, such as heat resistance, mechanical strength, and electrical properties; their decomposition temperature should not be too high, but they should not decompose at processing temperatures; they should have good durability; good weather resistance; and they should be inexpensive.

[0003] Common flame retardants include inorganic compounds, organophosphorus compounds, organohalogen compounds, and halogen-containing organophosphorus compounds. Among these, organohalogen compounds and halogen-containing organophosphorus compounds exhibit excellent flame-retardant effects. However, these halogen-containing compounds produce hydrogen halides during the pyrolysis of resin molding, which corrodes metal molds, degrades the resin itself, causes discoloration, and worsens working conditions. Another problem is that they produce toxic gases such as hydrogen halides and dioxins that are harmful to human health when exposed to fire or burned.

[0004] Therefore, halogen-free, low-smoke, and low-toxicity flame retardants have become the goal of many. These flame retardants include inorganic flame retardants such as antimony compounds, aluminum hydroxide, magnesium hydroxide, and borates, and organic nitrogen-based flame retardants such as triazine and its derivatives, and melamine. When used alone, their effects are not ideal, and large-scale use can lead to a decline in the physical properties of resins and other materials.

[0005] Phosphate esters are widely used as halogen-free flame retardants with good flame-retardant properties. However, with the development of the synthetic materials industry and the continuous expansion of application fields, the corresponding processing temperatures are getting higher and higher, creating an urgent need for flame retardants with thermal stability and low volatility. Solid flame retardants can meet the requirements of thermal stability and low volatility. In addition, solid powdered flame retardants have significant advantages over liquid flame retardants in terms of packaging, transportation, and addition.

[0006] Resorcinol bis[di(2,6-dimethylphenyl)phosphate] is such a solid phosphate flame retardant. Its molecular formula is C38H40O8P2, molecular weight is 686.667, melting point is 95.6-95.7℃, boiling point is 632.2±43.0℃ (760mmHg), flash point is 348.8±48.5℃, and its trade name is PX-200.

[0007] There are two main synthetic methods for resorcinol bis(2,6-dimethylarylphosphate):

[0008] (1) Patent US4134876 reports the synthesis of resorcinol tetrachlorobisphosphate from phosphorus oxychloride and resorcinol as raw materials, followed by the reaction of resorcinol tetrachlorobisphosphate with 2,6-dimethylphenol to obtain the target product. However, 2,6-dimethylphenol has significant steric hindrance, making it difficult for the chlorine atom on the intermediate to be completely substituted. The reaction temperature in the second step reaches 250-270℃, posing safety hazards in the process. The presence of impurities makes the product difficult to cure, thus losing its advantage as a powdered flame retardant.

[0009] (2) Using phosphorus oxychloride and 2,6-dimethylphenol as raw materials, a bis(2,6-dimethylphenyl)phosphoryl chloride intermediate is generated. Then, the intermediate reacts with resorcinol to generate resorcinol bis(2,6-dimethylaryl phosphate).

[0010] Daihachi Chemical Industry Co., Ltd. disclosed a method for preparing resorcinol bis[di(2,6-dimethylphenyl)phosphate] in patent JP5816175B2. This method consists of two steps: First, 2,6-dimethylphenol reacts with phosphorus oxychloride in the presence of a Lewis acid catalyst, and unreacted phosphorus oxychloride is removed under reduced pressure to obtain a specific diarylphosphoryl chloride; Second, the reaction product obtained in the above step is reacted with resorcinol in the presence of a Lewis acid catalyst to obtain resorcinol bis[di(2,6-dimethylphenyl)phosphate], as shown in the following reaction formula:

[0011]

[0012]

[0013] However, the route disclosed by Daihachi Chemical Industry Co., Ltd. readily generates the byproducts (2,6-dimethylphenyl) dichlorophosphate and (2,6-dimethylphenyl) phosphate in the first step of the reaction. Their structural formulas are as follows:

[0014]

[0015] (2,6-Dimethylphenyl) dichlorophosphate tris(2,6-dimethylphenyl) phosphate

[0016] The above-described route resulted in excessive byproducts in the first reaction step, leading to a more complex product in the second step. This forced researchers to choose between yield and quality, ultimately resorting to selective purification to ensure yield. This resulted in low purity and an excessive amount of byproducts in the final product. Under high-temperature conditions such as molding, these byproducts underwent transesterification with the aromatic diphosphate ester, the main component, further increasing the amount of byproducts and reducing the purity of the main component. Summary of the Invention

[0017] In view of the above-mentioned technical problems existing in the prior art, the purpose of the present invention is to provide a new synthetic method for the industrial production of resorcinol bis[di(2,6-dimethylphenyl)phosphate], which is conducive to providing industrial products of resorcinol bis[di(2,6-dimethylphenyl)phosphate] with high purity and excellent flame retardant properties.

[0018] The technical solution adopted in this invention is as follows:

[0019] A method for the efficient synthesis of resorcinol bis[di(2,6-dimethylphenyl)phosphate] includes: a first-step reaction in which phosphorus oxychloride and sodium resorcinol are reacted in a reaction solvent in the presence of a MgCl2 catalyst; after the reaction, the reaction solution is subjected to solid-liquid separation, and the resulting intermediate solution is directly introduced into the next step; the intermediate solution is added dropwise to a mixture of sodium 2,6-dimethylphenol, MgCl2 catalyst, and reaction solvent to carry out a second-step reaction; the reaction solution is then post-treated to obtain resorcinol bis[di(2,6-dimethylphenyl)phosphate]; the reaction formula is as follows:

[0020]

[0021] This invention provides a highly efficient method for synthesizing resorcinol bis[di(2,6-dimethylphenyl)phosphate], specifically comprising the following steps:

[0022] 1) Add phosphorus oxychloride, MgCl2 catalyst and reaction solvent to the reactor, stir and heat, then add sodium resorcinol while maintaining the temperature and stirring, carry out the first step reaction under normal pressure, and monitor the reaction by HPLC sampling and analysis until the end; after the reaction, the reaction solution is separated into solid and liquid to obtain an intermediate solution;

[0023] 2) Add sodium 2,6-dimethylphenol, MgCl2 catalyst and reaction solvent to the reactor, stir and heat, and then add the intermediate solution obtained in step 1) dropwise while keeping it at the temperature and stirring. Carry out the second step reaction under normal pressure. Monitor the reaction by HPLC sampling and analysis until the end. After the reaction, the solution is post-processed to obtain the target product.

[0024] Furthermore, in the first step reaction, the mass ratio of phosphorus oxychloride to sodium resorcinol is 1.5 to 3:1, preferably 2 to 2.5:1, and the mass ratio of MgCl2 catalyst to sodium resorcinol is 0.01 to 0.05:1, preferably 0.03 to 0.04:1.

[0025] Further, in step 1), the reaction solvent is toluene, and the mass of sodium resorcinol raw material is 40-60% of the mass of the reaction solvent, preferably 50-55%.

[0026] Furthermore, in step 1), when sodium resorcinol is added under normal pressure, the temperature of the mixture in the reactor is 50-75°C, and after the addition is complete, the reaction temperature is maintained at 50-75°C, preferably 60-70°C.

[0027] Furthermore, in step 2), the mass ratio of sodium 2,6-dimethylphenol to sodium hydroquinone in step 1) is 2 to 5:1, preferably 3.5 to 4:1, and the mass of MgCl2 catalyst in step 2) is 0.5 to 3 times the mass of sodium 2,6-dimethylphenol, preferably 1.5 to 2 times.

[0028] Furthermore, in step 2), the reaction solvent is toluene, and the mass of sodium 2,6-dimethylphenol is 0.8 to 1.2 times the mass of the reaction solvent.

[0029] Furthermore, in step 2), when the intermediate solution is added dropwise under normal pressure, the temperature of the mixture in the reactor is 80-95°C, and after the addition is complete, the reaction temperature is maintained at 80-100°C, preferably 90-100°C.

[0030] Furthermore, after the second step of the reaction is completed, the reaction solution is post-processed as follows: the reaction solution is filtered, the filtrate is thoroughly washed with the same solvent as the reaction solvent, and the filtrate and the washing liquid are combined to form a crude reaction solution; diatomaceous earth is added to the crude reaction solution and stirred thoroughly, then filtered again, and then vacuum distilled to completely remove the solvent, thus obtaining the target product.

[0031] This invention involved in-depth research, resulting in a novel one-pot process for synthesizing resorcinol bis[di(2,6-dimethylphenyl)phosphate]. First, phosphorus oxychloride, MgCl2 catalyst, and solvent are added, stirred, and heated to a specific temperature. Then, while maintaining the temperature and stirring, sodium resorcinol is added at a controlled feeding rate to prepare an intermediate solution. Next, sodium 2,6-dimethylphenol, MgCl2 catalyst, and solvent are added, stirred, and heated to a specific temperature. Then, while maintaining the temperature and stirring, the intermediate solution is added dropwise. By using sodium phenolate and setting optimal process conditions, high-yield and high-purity resorcinol bis[di(2,6-dimethylphenyl)phosphate] is obtained, thus completing this invention.

[0032] The beneficial effects achieved by this invention are:

[0033] This invention provides a simple and efficient synthesis method using sodium resorcinol, phosphorus oxychloride, and 2,6-dimethylphenol as raw materials. The first and second steps of the reaction use MgCl2 as a catalyst and toluene as a reaction solvent to synthesize resorcinol bis[2,6-dimethylphenyl]phosphate in a high-efficiency and high-yield "one-pot" process. Attached Figure Description

[0034] Figure 1 The P-type resorcinol bis[di(2,6-dimethylphenyl)phosphate] synthesized in this invention 31 (CDCl3) spectrum;

[0035] Figure 2 The C33-C4 ... 13 (CDCl3) spectrum;

[0036] Figure 3 The image shows the FT-IR spectrum of resorcinol bis[di(2,6-dimethylphenyl)phosphate] synthesized in this invention.

[0037] Figure 4 This is a comparison of the tensile strength test results between the WSFR-1103 group and the PX200 group of this invention;

[0038] Figure 5 This is a comparison of the bending modulus test results between the WSFR-1103 group and the PX200 group of this invention;

[0039] Figure 6 This is a comparison of the oxygen index test results between the WSFR-1103 group and the PX200 group of this invention;

[0040] Figure 7 This is a comparison of the melt index test results between the WSFR-1103 group and the PX200 group of this invention. Detailed Implementation

[0041] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0042] Example 1:

[0043] A stirrer, nitrogen inlet tube, thermometer, distillation tube, and stopcock (for sampling) are installed on a 3000ml glass reactor. A moisture metering receiver and cooling tube are installed at the front end of the distillation tube, and a powder metering feeder (to maintain a nitrogen atmosphere) is set up. This apparatus is used as the reaction device. Phosphorus oxychloride (316.0g) as raw material, toluene (300.0g) as solvent, and MgCl2 (5.0g) as catalyst are added to the above flask. Under normal pressure and at a system temperature of 60°C, sodium resorcinol (154.0g) as raw material is added at a uniform rate, and the addition rate of sodium resorcinol is adjusted in real time to ensure that the reaction solution temperature does not exceed 65°C. After the addition is complete, the system is maintained at a reaction temperature of 65°C for the first step of the reaction until the raw material content is below 1% (HPLC analysis), at which point the first step of the reaction is terminated (the first step of the reaction takes 3-4 hours). The reaction suspension was completely removed from the glass reactor. Then, the reaction suspension from the first step was filtered under a nitrogen atmosphere and kept at a temperature of 60-70°C. The filter cake was thoroughly washed three times with 100g of toluene. The filtrate and the washing liquid were combined to obtain an intermediate solution, which was then introduced into a dropping funnel.

[0044] 573.0 g of 2,6-dimethylphenol, 500 g of toluene, and 10.0 g of MgCl2 as a catalyst were added to the glass reactor. Under normal pressure and at a system temperature of 90°C, the solution in the dropping funnel (the filtrate and eluent from the first step reaction) was added dropwise, with the dropping rate adjusted in real time to ensure the system temperature did not exceed 95°C. After the addition was complete, the system was kept at 100°C for the second step reaction. The second step reaction was terminated when the raw material content was found to be below 1% by HPLC analysis. The mixture was then filtered, and the filter cake was thoroughly washed three times with 100 g of toluene. The filtrate and eluent were combined to obtain the crude reaction solution. Diatomaceous earth (20 g) was added to the crude reaction solution and stirred for 10 minutes. The mixture was filtered again, and then subjected to vacuum distillation to completely remove the solvent, thereby producing resorcinol bis[di(2,6-dimethylphenyl)phosphate] as the target compound, with a yield of 95%. Purity was determined using P... 31 The NMR spectroscopy of (CDCl3) determined that it was greater than 99.5%, indicating high purity.

[0045] The above-synthesized resorcinol bis[di(2,6-dimethylphenyl)phosphate] was identified using NMR and IR, and the identification results are shown below.

[0046] The P-type of the synthesized resorcinol bis[di(2,6-dimethylphenyl)phosphate] 31 The (CDCl3) spectrum is as follows Figure 1 The P-type resorcinol bis[di(2,6-dimethylphenyl)phosphate], as the main component 31(CDCl3) chemical shifts are -17.37 ppm and -16.44 ppm, exhibiting a single peak. 13 The (CDCl3) spectrum is as follows Figure 2 C, as the synthetic resorcinol bis[di(2,6-dimethylphenyl)phosphate] 13 The chemical shifts of (CDCl3) are 17.12 ppm, 112.71 ppm, 112.76 ppm, 112.82 ppm, 117.12 ppm, 117.16 ppm, 125.67 ppm, 125.70 ppm, 129.27 ppm, 129.28 ppm, 130.28 ppm, 130.38 ppm, 130.42 ppm, 148.06 ppm, 148.15 ppm, 151.28 ppm, and 151.35 ppm.

[0047] The FT-IR spectrum of the synthesized resorcinol bis[di(2,6-dimethylphenyl)phosphate] is shown below. Figure 3 .

[0048] Examples 2-5 and Comparative Examples 1-3:

[0049] The operating procedures of Examples 2-5 and Comparative Examples 1-3 were the same as those of Example 1, except that the temperatures of the first and second steps of the reaction were adjusted. Additionally, the reaction time data for the second step in Examples 2-5 and Comparative Examples 1-3, recorded by HPLC analysis when the starting material concentration was below 1%, are summarized in Table 1. The corresponding changes in reaction conditions and the final experimental results are listed in Table 1.

[0050] Table 1. Effect of reaction temperature on the yield and purity of the synthesized product

[0051]

[0052] As can be seen from Table 1, the temperature of the first and second steps of the "one-pot reaction" has a significant impact on the product yield and purity. By adapting the conditions, the reaction time can be shortened and a high-yield and high-purity product can be prepared.

[0053] The resorcinol bis[di(2,6-dimethylphenyl)phosphate] sample obtained in Example 1 of this invention was labeled as WSFR-1103, and used as flame retardant raw materials along with commercially available product PX-200 (DaBa Chemical) to prepare flame retardant PC / ABS alloy resin test pieces, and their performance was compared.

[0054] Table 2. Comparison of heat resistance of phosphite compounds (TGA)

[0055]

[0056] According to the PC / ABS alloy resin formulations recorded in Table 2 above, granules were produced at 240℃ using an extruder (manufactured by Nanjing Shengchi Rubber & Plastic Machinery Manufacturing Co., Ltd., model 35). Granules obtained from formulation 1# were designated as Granule A, those from formulation 2# as Granule B, those from formulation 3# as Granule C, and those from formulation 4# as Granule D. Then, using a high-temperature injection molding machine (Ningbo Lianyuan Machinery, UP-100S) at a processing temperature of 240℃, the flame-retardant PC / ABS synthetic resin granules A and D were mixed and molded to obtain PC / ABS synthetic resin samples, which were then tested for various properties.

[0057] Tensile strength test: A universal tensile testing machine (FL4204Z, Fule Instrument Technology Co., Ltd.) was used, according to GB / T1043-2018. Type IA specimens were used, the test speed was 50 mm / min, and the gauge length was 50 mm. The comparison results of the tensile strength tests between the WSFR-1103 group and the PX200 group are shown below. Figure 4 , Figure 4 The "Control group" indicates that no flame retardant has been added. As can be seen from the tensile strength data, the tensile strength of PX200 and WSFR-1103 is basically the same.

[0058] Bending modulus test: A universal tensile testing machine (FL4204Z, Fule Instrument Technology Co., Ltd.) was used, following GB / T9341-2008. The specimen size was 80mm*10mm*4mm, the test speed was 2mm / min, and the span was 64mm. The comparison results of the bending modulus tests between the WSFR-1103 group and the PX200 group are shown below. Figure 5 , Figure 5 The "Control group" refers to the absence of flame retardants. The flexural modulus data shows that WSFR-1103 has a better flexural modulus than DaBa PX-200.

[0059] UL94V Test: Horizontal flammability tester (PX-03-001, Jiangsu Felman Safety Technology Co., Ltd.), according to GB / T2408-2008. Samples were 125mm*13mm in size, with thicknesses of 0.8mm, 1.6mm, and 3.2mm. Test method B, vertical flammability test, was used, with a 50W flame. The distance from the tip of the blowtorch to the midpoint of the bottom edge of the sample was 10mm. If burning droplets were observed, the blowtorch angle was changed to a 45° tilt. The UL94V@1.6mm test results for the WSFR-1103 group and the PX200 group are shown in Table 3.

[0060] Table 3 UL94V@1.6mm Test Results

[0061]

[0062] The data from the UL94V test results show that the flame retardant effect of PX200 is basically the same as that of WSFR-1103. Adding 12% of both to an alloy of PC / ABS=80 / 20 can achieve a flame retardant rating of 1.6mmV-0.

[0063] Oxygen Index: A fully automated oxygen index meter (model 5801A, Suzhou Yangyi Wolchi Testing Technology Co., Ltd.) was used according to GB / T2406-2009. Samples were 80mm*10mm*4mm in size, and the ignition method was Method A—top-side ignition. The measurement criteria were a burning time of 180s or a burning length less than 50mm below the top of the sample. The comparison results of oxygen index tests between the WSFR-1103 group and the PX200 group are shown below. Figure 6 , Figure 6 The "Control group" refers to the group without added flame retardants. As can be seen from the oxygen index data, with the same amount of added flame retardant, the oxygen index of WSFR-1103 is better than that of DaBa PX-200.

[0064] Finally, a melt flow index (MFI) test was conducted (260℃, 2.16kg). The comparison results of the MFI test results between the WSFR-1103 group and the PX200 group are shown below. Figure 7 , Figure 7 The “Control group” refers to the group without added flame retardants. As can be seen from the melt flow index data, due to the intensified decomposition during processing, the melt flow rate of PX200 is significantly higher than that of WSFR-1103.

[0065] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the scope of protection of this invention should not be regarded as limited to the specific forms described in the embodiments.

Claims

1. A method for the efficient synthesis of resorcinol bis[di(2,6-dimethylphenyl)phosphate], characterized in that... Includes the following steps: 1) Add phosphorus oxychloride, MgCl2 catalyst and reaction solvent to the reactor, stir and heat, then add sodium resorcinol while maintaining the temperature and stirring, carry out the first step reaction under normal pressure, and monitor the reaction by HPLC sampling and analysis until the end; after the reaction, the reaction solution is separated into solid and liquid to obtain an intermediate solution; 2) Add sodium 2,6-dimethylphenol, MgCl2 catalyst, and reaction solvent to the reactor, stir and heat, then add the intermediate solution obtained in step 1) dropwise while maintaining the temperature and stirring. Carry out the second step reaction under normal pressure. Monitor the reaction by HPLC sampling and analysis until completion. After the reaction, the solution is post-processed to obtain the target product. The reaction formula is as follows: ； In the first step of the reaction, the mass ratio of phosphorus oxychloride to sodium resorcinol is 1.5~3:1, and the mass ratio of MgCl2 catalyst to sodium resorcinol is 0.01~0.05:

1. In step 1), the reaction temperature in the first step is 65℃; In step 2), the mass ratio of sodium 2,6-dimethylphenol to sodium hydroquinone in step 1) is 2~5:1, and the mass of MgCl2 catalyst in step 2) is 0.5~3 times the mass of sodium 2,6-dimethylphenol. In step 2), the reaction temperature in the second step is 90-100℃; After the second step of the reaction is completed, the reaction solution is post-processed as follows: the reaction solution is filtered, the filtrate is thoroughly washed with the same solvent as the reaction solvent, and the filtrate and the washing liquid are combined to form the crude reaction solution; diatomaceous earth is added to the crude reaction solution and stirred thoroughly, then filtered again, and then vacuum distilled to completely remove the solvent, thus obtaining the target product.

2. The method for efficiently synthesizing resorcinol bis[di(2,6-dimethylphenyl)phosphate] as described in claim 1, characterized in that... Step 1) In the first step of the reaction, the mass ratio of phosphorus oxychloride to sodium resorcinol is 2~2.5:1, and the mass ratio of MgCl2 catalyst to sodium resorcinol is 0.03~0.04:

1.

3. The method for efficiently synthesizing resorcinol bis[di(2,6-dimethylphenyl)phosphate] as described in claim 1, characterized in that... In step 1), the reaction solvent is toluene, and the mass of sodium resorcinol is 40-60% of the mass of the reaction solvent.

4. The method for efficiently synthesizing resorcinol bis[di(2,6-dimethylphenyl)phosphate] as described in claim 3, characterized in that... In step 1), the reaction solvent is toluene, and the mass of sodium resorcinol is 50-55% of the mass of the reaction solvent.

5. The method for efficiently synthesizing resorcinol bis[di(2,6-dimethylphenyl)phosphate] as described in claim 1, characterized in that... In step 2), the mass ratio of sodium 2,6-dimethylphenol to sodium hydroquinone in step 1) is 3.5~4:1, and the mass of MgCl2 catalyst in step 2) is 1.5~2 times the mass of sodium 2,6-dimethylphenol.

6. The method for efficiently synthesizing resorcinol bis[di(2,6-dimethylphenyl)phosphate] as described in claim 1, characterized in that... In step 2), the reaction solvent is toluene, and the mass of sodium 2,6-dimethylphenol is 0.8 to 1.2 times the mass of the reaction solvent.

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