Method for detecting purity of phosphonitrilic chloride trimer

Abstract

The invention discloses a method for detecting the purity of phosphonitrilic chloride trimer, which comprises the following specific operation processes: adding N, N-dimethylformamide into a sample to be detected, stirring and dissolving the sample, adding a sodium hydroxide solution, heating to react, cooling to room temperature after the reaction is finished, adding nitric acid to neutralize excessive sodium hydroxide, adding a ferric nitrate solution as a masking agent, and detecting the purity of phosphonitrilic chloride trimer. And titrating the content of free chloride ions by using silver nitrate through a potentiometric titrator so as to calculate the purity of phosphonitrilic chloride trimer.

Description

Technical Field

[0001] The invention belongs to the technical field of compound detection, and particularly relates to a method for detecting the purity of hexachlorocyclotriphosphazene. Background Art

[0002] In recent years, phosphorus and nitrogen-containing flame retardants have attracted attention due to their high flame retardant efficiency, good synergistic effect and halogen-free advantages. Cyclophosphazene derivatives have high thermal stability, rich phosphorus and nitrogen content, good biocompatibility and low toxicity. There are many types, which can meet the needs of most material processing and flame retardancy. It is a hot spot for the development of halogen-free, low-toxic, green and efficient flame retardant materials, and it is also one of the promising development directions in the field of flame retardancy in the future. Hexachlorocyclotriphosphazene is rich in phosphorus and nitrogen elements, and its stable conjugated ring structure gives it certain thermal stability and flame retardant properties. It is an ideal flame retardant intermediate. It is widely used in flame retardant research such as EP, PU and PC / ABS alloys.

[0003] Hexachlorocyclotriphosphazene is the most important intermediate raw material in phosphazene chemistry and the preferred precursor for synthesizing polyphosphazenes. The purity of hexachlorocyclotriphosphazene products has always been the primary concern in synthesizing polyphosphazenes. The accurate determination of the purity of phosphazenes can ensure the smooth progress of the next step of the reaction. Chinese patent CN118641661A uses gas chromatography-mass spectrometry for detection. This method has high equipment requirements, high detection costs, and is aimed at low-content determination. The physical and chemical analysis method for the purity of hexachlorocyclotriphosphazene has always been a blank area. Summary of the invention

[0004] In view of the above problems, the object of the present invention is to provide a method for detecting the purity of hexachlorocyclotriphosphazene.

[0005] The present invention adopts a conventional physical and chemical analysis method, so that the chloride ions in the hexachlorocyclotriphosphazene molecules are digested by wet method, reacted with sodium hydroxide to be freed, and N,N-dimethylformamide is added to play the role of both solvent and catalyst to accelerate the digestion process, and the phosphorus hydroxy acidic group generated by the reaction will be complexed with silver nitrate to produce a complex, resulting in a larger measured value. In order to eliminate the reaction, ferric nitrate is added as a masking agent to react with the phosphorus hydroxy acidic group to form a chelate, and then the silver nitrate is used to titrate the free chloride ion content through a potentiometric titrator, so as to calculate the purity of the hexachlorocyclotriphosphazene.

[0006]

[0007] The specific technical solutions are as follows:

[0008] A method for detecting the purity of hexachlorocyclotriphosphazene comprises the following steps:

[0009] 1) Add N,N-dimethylformamide to the sample, stir to dissolve the sample, add sodium hydroxide solution, heat to react, and cool to room temperature after the reaction is completed;

[0010] 2) After adding nitric acid to the solution of step 1) to neutralize excess sodium hydroxide, a ferric nitrate solution is added as a masking agent, and then the content of free chloride ions is titrated using silver nitrate by a potentiometric titrator to calculate the purity of the hexachlorocyclotriphosphazene.

[0011] Furthermore, in step 1), the ratio of the added volume of N,N-dimethylformamide to the mass of the sample is 200-350:1, the volume unit is mL, and the mass unit is g.

[0012] Furthermore, the concentration of the sodium hydroxide solution in step 1) is 200 g / L, the ratio of the added volume to the sample mass is 100-170:1, the volume unit is mL, and the mass unit is g.

[0013] Furthermore, in step 1), the reaction is heated to boiling reflux, and the reaction time is 30 minutes.

[0014] Furthermore, in step 2), the concentration of the ferric nitrate solution is 0.2 mol / L, the ratio of the added volume to the sample mass is 150-250:1, the volume unit is mL, and the mass unit is g.

[0015] The beneficial effects of the present invention are:

[0016] 1) The present invention provides a new idea for determining the purity of hexachlorocyclotriphosphazene. The method is simple, easy to operate, has high precision, and has high result accuracy. It provides a more convenient and quick determination method for manufacturers to monitor the quality of hexachlorocyclotriphosphazene and for testing agencies to detect the purity of hexachlorocyclotriphosphazene.

[0017] 2) The present invention measures the purity of hexachlorocyclotriphosphazene by a physical and chemical analysis method, which reduces equipment requirements and detection costs compared to detection using instruments.

[0018] 3) N,N-dimethylformamide was used to take into account the role of solvent and catalyst, promote the reaction of hexachlorocyclotriphosphazene with sodium hydroxide, and accelerate the digestion process. In order to avoid the formation of complexes between the phosphorus hydroxy acidic groups generated by the reaction and silver nitrate, resulting in a larger measured value, ferric nitrate was added as a masking agent to react with the phosphorus hydroxy acidic groups to form a chelate; silver nitrate was used to titrate the free chloride ion content using a potentiometric titrator. The detection was convenient and quick, ensuring the repeatability and accuracy of the hexachlorocyclotriphosphazene purity data. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the experimental device used in the examples.

[0020] In the figure: 1. Two-necked flat-bottomed flask; 2. Constant temperature magnetic stirrer; 3. Condenser; 4. Constant pressure funnel; 5. Covered funnel. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with embodiments, but the protection scope of the present invention is not limited thereto.

[0022] The instruments and reagents used in the following examples are as follows:

[0023] Analytical balance (accurate to 0.0001 g);

[0024] Glass apparatus: 250 mL two-necked flat-bottom flask, spherical condenser, 50 mL constant pressure funnel, 50 mL covered funnel;

[0025] Silver nitrate standard titration solution: 0.1 mol / L, prepared and calibrated according to GB / T 063;

[0026] Starch indicator (10g / L): prepared according to GB / T 603;

[0027] Nitric acid solution (1+3): nitric acid: water (volume) = 1:3;

[0028] N,N-dimethylformamide (DMF);

[0029] 200g / L NaOH solution: weigh 100g sodium hydroxide (NaOH) in a beaker, add water to dissolve, and make up to volume in a 500mL volumetric flask;

[0030] 0.2mol / L Fe(NO3)3 solution: weigh 40.4g of ferric nitrate nonahydrate (Fe(NO3)3·9H2O) into a 500mL volumetric flask and add deionized water to make up to volume;

[0031] Phenolphthalein indicator (10g / L): prepared in accordance with GB / T 603.

[0032] Example

[0033] Use Figure 1The device shown in the figure weighs the hexachlorocyclotriphosphazene sample to be tested (accurate to 0.0001g) into a 250mL two-necked flat-bottomed flask 1, puts a magnet, adds 40mL N,N-dimethylformamide (DMF), and places it on a constant temperature magnetic stirrer 2. The two-necked flat-bottomed flask 1 is directly connected to a condenser 3, a constant pressure funnel 4 is added to the side port, and a cover funnel 5 is installed above the condenser 3; after stirring and dissolving the sample, 20mL 200g / L NaOH solution is added to the condenser 3, heated to boiling and reflux for 30min, and cooled to room temperature; 30mL 0.2mol / L Fe(NO3)3 solution is pre-added to the constant pressure funnel 4, deionized water is pre-added to the cover funnel 5, 3 drops of phenolphthalein indicator are added to the condenser 3, nitric acid solution (1+3) is added dropwise until the red color disappears, and 6mL nitric acid solution (1+3) is quickly added. Add the Fe(NO3)3 solution in the constant pressure funnel 4 dropwise into the two-mouth flat-bottom flask 1, heat and stir at 260℃, wait for 15 minutes after the precipitation is formed, and cool to room temperature (the water in the cover funnel 5 needs to be added after back-sucking). Add 3mL of starch indicator into the two-mouth flat-bottom flask 1, and place the solution on the potentiometric titrator for measurement. At the same time, do a blank test (in the blank test, except for the absence of the sample, the type and amount of other reagents added are the same as the test solution), record the volume V0 of the consumed silver nitrate standard titration solution, and calculate the purity of hexachlorocyclotriphosphazene based on the volume of the consumed silver nitrate standard titration solution.

[0034] The calculation formula for the purity ω% of hexachlorocyclotriphosphazene is as follows:

[0035]

[0036] Where:

[0037] c—concentration of silver nitrate standard titration solution, unit: mol / L;

[0038] m—mass of the sample, unit: g;

[0039] V0—the volume of silver nitrate standard titration solution consumed in the blank test, unit: mL;

[0040] V—volume of silver nitrate standard titration solution consumed by the sample, unit: mL;

[0041] M—molar mass of hexachlorocyclotriphosphazene, unit: g / mol.

[0042] Parallelism test data

[0043] Sample 1:

[0044] Table 1 Sample 1 parallelism test and RSD value

[0045]

[0046]

[0047] Sample 2:

[0048] Table 2 Sample parallelism test and RSD value

[0049]

[0050] Sample 3:

[0051] Table 3 Three parallel tests of samples and RSD values

[0052]

[0053] As shown in Tables 1-3, 8 groups of parallel tests were carried out on the three samples, and the RSDs of the 8 groups of data were calculated to be 0.15%, 0.13% and 0.17%, respectively, indicating that the method is stable and has good precision.

Claims

1. A method for detecting the purity of hexachlorocyclotriphosphazene, characterized in that: The steps include: 1) Add N,N-dimethylformamide to the sample, stir to dissolve the sample, add sodium hydroxide solution, heat to react, and cool to room temperature after the reaction is completed; 2) After adding nitric acid to the solution of step 1) to neutralize excess sodium hydroxide, a ferric nitrate solution is added as a masking agent, and then the content of free chloride ions is titrated using silver nitrate by a potentiometric titrator to calculate the purity of the hexachlorocyclotriphosphazene.

2. A method for detecting the purity of hexachlorocyclotriphosphazene as claimed in claim 1, characterized in that: In step 1), the mass ratio of N,N-dimethylformamide to the sample is 200-350:

1.

3. A method for detecting the purity of hexachlorocyclotriphosphazene as claimed in claim 1, characterized in that: The concentration of the sodium hydroxide solution in step 1) is 200 g / L, the ratio of the added volume to the sample mass is 100-170:1, the volume unit is mL, and the mass unit is g.

4. A method for detecting the purity of hexachlorocyclotriphosphazene as claimed in claim 1, characterized in that: In step 1), the reaction is heated to boiling reflux, and the reaction time is 30 minutes.

5. A method for detecting the purity of hexachlorocyclotriphosphazene as claimed in claim 1, characterized in that: In step 2), the concentration of the ferric nitrate solution is 0.2 mol / L, the ratio of the added volume to the sample mass is 150-250:1, the volume unit is mL, and the mass unit is g.

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