Method for measuring content of propylene carbonate in polycarbonate polyether polyol

Abstract

The invention discloses a method for measuring the content of propylene carbonate in polycarbonate polyether polyol, which comprises the following steps: step 1, transferring quantitative sodium hydroxide and barium chloride solution into a container containing a to-be-measured sample with the mass of m, stirring and mixing, adding a phenolphthalein indicator, titrating with a hydrochloric acid standard solution until the solution changes color, and recording the use volume V of the hydrochloric acid standard solution; step 2, transferring the same amount of sodium hydroxide and barium chloride solution in the step 1, stirring and mixing, adding a phenolphthalein indicator, titrating with a hydrochloric acid standard solution until the solution changes color, and recording the use volume V0 of the hydrochloric acid standard solution as a blank sample; according to the method, propylene carbonate is converted into carbonate ions through the alkaline hydrolysis reaction of propylene carbonate, and then quantitative precipitation is conducted through barium chloride; and the content of propylene carbonate can be accurately calculated by analyzing the precipitate. The method is a solution which is low in cost, simple and convenient to operate and rapid in analysis, and is particularly suitable for rapid quality monitoring and process optimization of an industrial production line.

Description

Technical Field

[0001] This invention relates to the field of polymer impurity detection technology, specifically to a method for measuring the propylene carbonate content in polycarbonate polyether polyols. Background Technology

[0002] Carbon dioxide (CO2)-based polycarbonate polyether polyols (PCEs) contain both polycarbonate segments and polyether segments formed by the homopolymerization of epoxy compounds, giving them both high Young's modulus and flexibility, making them a suitable raw material for polyurethane materials. Since the polymerization reaction producing PCE consumes CO2, converting the greenhouse gas CO2 into a polymer material is highly beneficial for environmental protection and energy conservation and emission reduction. However, this polymerization reaction often produces propylene carbonate (PC) as a byproduct. Due to PC's high boiling point (240-242℃), it is difficult to completely remove it through vacuum distillation. For example, in the synthesis of polyether polyols containing urethane structures, CN 115785431 A describes vacuum distillation used to remove propylene carbonate after the reaction, but this is only as thorough as possible. Even slight differences in PC content can significantly affect product performance, therefore, testing the PC content in PCE is a necessary step.

[0003] For example, Wang Zhiqiang et al. (Wang Zhiqiang, Cao Tingting, Ma Dongqing, Bu Zhanwei. Determination of propylene carbonate content in polypropylene carbonate [J]. Chemical Research, 2011, 22(5):8-10) used gas chromatography to analyze the propylene carbonate content in polypropylene carbonate. The relative standard deviation was less than 7.5%, and the recovery rate reached 102.3%, which meets the requirements of industrial analysis. This analytical method can not only be used for process analysis of PPC production and quality detection of PPC resin, but also for the determination of PC content in PPC products. The method is simple to operate and has high accuracy.

[0004] Currently, the PC content of polycarbonate polyether polyols (PCE) can only be tested using 1H NMR spectroscopy. However, this method is time-consuming, requires expensive equipment, and is complex to operate, making it difficult to meet the rapid testing needs of enterprises in daily production. Therefore, it is essential to develop a PC content detection method that is accurate, easy to operate, and efficient. Summary of the Invention

[0005] This invention addresses the problem of complex and expensive methods and equipment for determining the propylene carbonate content in polycarbonate polyether polyol synthesis products. It provides a simple, rapid, and low-cost method for testing the PC content, which has good repeatability and accuracy.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for measuring the propylene carbonate content in polycarbonate polyether polyols, comprising the following steps: Step 1: Transfer a quantitative amount of sodium hydroxide and barium chloride solution into a container containing mass m of the sample to be tested. After stirring and mixing, add phenolphthalein indicator and titrate with hydrochloric acid standard solution until the solution changes color. Record the volume V of hydrochloric acid standard solution used. Step 2: Take the same amount of sodium hydroxide and barium chloride solution as in Step 1, stir and mix, add phenolphthalein indicator, titrate with hydrochloric acid standard solution until the solution changes color, and record the volume V0 of hydrochloric acid standard solution used for the blank sample. The propylene carbonate content in the sample to be tested was calculated as follows: Where PC% is the mass content of PC in PCE, %; V is the volume of hydrochloric acid standard solution consumed in titrating the test sample, mL; V0 is the volume of hydrochloric acid standard solution consumed in titrating the blank sample, mL; m is the mass of the PCE sample, g; and w is the hydrochloric acid concentration, mol / L.

[0007] The principle of propylene carbonate content determination in this invention is as follows: Propylene carbonate reacts with sodium hydroxide to produce 1,2-propanediol and sodium carbonate. Excess barium chloride is then added to convert the sodium carbonate into barium carbonate precipitate. Barium carbonate does not preferentially react with hydrochloric acid under alkaline conditions. The remaining sodium hydroxide is then calibrated using a standard hydrochloric acid solution, and the endpoint is indicated by phenolphthalein. The amount of sodium hydroxide consumed by propylene carbonate is calculated based on the amount of hydrochloric acid used, thus yielding the propylene carbonate content in the polymer. The reaction mechanism is as follows: In step 1, the mass of the sample to be tested is accurate to 0.001g.

[0008] Before adding sodium hydroxide and barium chloride solutions in steps 1 and 2, the air inside the container should be replaced with an inert gas.

[0009] In step 1, the mixture is stirred and mixed at 80-95℃ for 15-60 minutes.

[0010] In step 2, the mixture is stirred at 80-95℃ for 15-60 minutes.

[0011] This invention is for the determination of propylene carbonate content in polycarbonate polyether polyols. Therefore, the influence on the polycarbonate polyether polyol sample itself needs to be considered during the measurement process to avoid the polyol in the sample from dissolving and affecting the accuracy of the measurement. The temperature should not be too high during the mixing process, and the mixing time should not be too long.

[0012] The hydrochloric acid standard solution is a 0.1-1.0 mol / L hydrochloric acid solution, more preferably a 0.5015 mol / L hydrochloric acid standard solution.

[0013] The sodium hydroxide solution has a concentration of 0.125 mol / L to 0.5 mol / L; the barium chloride solution has a concentration of 40 g / L to 60 g / L.

[0014] In step 1, the mass ratio of sodium hydroxide solution to barium chloride solution is 5:1 to 5:2.

[0015] In step 1, the mass of sodium hydroxide added should be at least 0.4 times the mass of the sample to be tested. When the PC content of the sample is known to be less than 10%, the mass of sodium hydroxide added should be at least 0.1 times the mass of the sample to be tested.

[0016] The sample to be tested is a polycarbonate polyether polyol produced as a byproduct of industrial production, which must be liquid at room temperature and contain less than 50% propylene carbonate by mass.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention addresses the complexity of determining the content of propylene carbonate impurities in polycarbonate polyether polyol samples by disclosing a simple and convenient titration method. Through optimized experimental conditions and simplified procedures, this method enables the testing of a large number of samples in a short time, significantly improving detection efficiency. The application of this technology not only helps reduce enterprise testing costs but also accelerates product development and quality control processes, possessing broad market application prospects and commercial promotion value. Attached Figure Description

[0018] Figure 1 The NMR spectrum of PCE-1 used in Example 1 is shown. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Modifications or equivalent substitutions made by those skilled in the art based on their understanding of the technical solutions of this invention, without departing from the spirit and scope of the invention, should be covered within the protection scope of this invention.

[0020] All raw materials used in the following specific embodiments were purchased commercially. The polycarbonate polyether polyol (PCE) sample was obtained from Hefei Puli Advanced Materials Technology Co., Ltd.

[0021] Example 1 S1. Preparation of standard solutions and preparation of reaction solutions: Preparation of standard solutions (purchased hydrochloric acid standard solution (0.5015 mol / L)); Preparation of reaction solutions: sodium hydroxide solution concentration is 0.125 mol / L, barium chloride solution concentration is 51 g / L.

[0022] S2. Sample weighing: Place PCE-1 in a 75℃ oven and let it stand for 1 hour. Then pour 2.504g of sample into the conical flask.

[0023] S3. Sample Titration Analysis: Transfer 50 mL of sodium hydroxide solution and 10 mL of barium chloride solution to the conical flask containing the sample. Insert a three-way valve with a nitrogen balloon and perform three nitrogen purgings. Place the conical flask in an 80℃ oil bath and stir for 30 min. After stirring, titrate while hot: Add 6 drops of phenolphthalein indicator and titrate with the standard solution until the solution color changes from red to colorless, which is the endpoint. Record the volume of hydrochloric acid standard solution consumed: 9.10 mL.

[0024] S4. Blank Titration Analysis: Transfer 50 mL of sodium hydroxide solution and 10 mL of barium chloride solution to an Erlenmeyer flask without samples. Insert a three-way valve with a nitrogen balloon and perform three nitrogen purgings. Place the Erlenmeyer flask in an 80°C oil bath and stir for 30 min. After stirring, titrate while hot: Add 6 drops of phenolphthalein indicator and titrate with the standard solution until the solution color changes from red to colorless, which is the endpoint. Record the volume of hydrochloric acid standard solution consumed: 11.40 mL.

[0025] S5. According to the formula, the PC content in sample PCE-1 is calculated to be 2.35%.

[0026] Example 2 S1. Preparation of standard solutions and preparation of reaction solutions: Preparation of standard solutions (purchased hydrochloric acid standard solution (0.5015 mol / L)); Preparation of reaction solutions: sodium hydroxide solution concentration is 0.25 mol / L, barium chloride solution concentration is 51 g / L.

[0027] S2. Sample weighing: PCE-2 does not require heating (PC content is high), pour 1.503 g of sample directly into the conical flask.

[0028] S3. Sample Titration Analysis: Transfer 50 mL of sodium hydroxide solution and 20 mL of barium chloride solution to the conical flask containing the sample. Insert a three-way valve with a nitrogen balloon and perform three nitrogen purgings. Place the conical flask in an 80℃ oil bath and stir for 30 min. After stirring, titrate while hot: Add 6 drops of phenolphthalein indicator and titrate with the standard solution until the solution color changes from red to colorless, which is the endpoint. Record the volume of hydrochloric acid standard solution consumed: 9.10 mL.

[0029] S4. Blank Titration Analysis: Transfer 50 mL of sodium hydroxide solution and 20 mL of barium chloride solution to an Erlenmeyer flask without samples. Insert a three-way valve with a nitrogen balloon and perform three nitrogen purgings. Place the Erlenmeyer flask in an 80°C oil bath and stir for 30 min. After stirring, titrate while hot: Add 6 drops of phenolphthalein indicator and titrate with the standard solution until the solution color changes from red to colorless, which is the endpoint. Record the volume of hydrochloric acid standard solution consumed: 23.30 mL.

[0030] S5. The PC content is calculated to be 24.20% according to the formula.

[0031] Comparative Example 1 S1. Preparation of standard solutions and preparation of reaction solutions: Preparation of standard solutions (purchased hydrochloric acid standard solution (0.5015 mol / L)); Preparation of reaction solutions: sodium hydroxide solution concentration is 0.125 mol / L, barium chloride solution concentration is 51 g / L.

[0032] S2. Sample weighing: Place PCE-1 in a 75℃ oven and let it stand for 1 hour. Then pour 2.500 g of the sample into the conical flask.

[0033] S3. Sample Titration Analysis: Transfer 50 mL of sodium hydroxide solution and 10 mL of barium chloride solution to the conical flask containing the sample. Insert a three-way valve with a nitrogen balloon and perform three nitrogen purgings. Place the conical flask in an 80℃ oil bath and stir for 25 min. After stirring, titrate while hot: Add 6 drops of phenolphthalein indicator and titrate with the standard solution until the solution color changes from red to colorless, which is the endpoint. Record the volume of hydrochloric acid standard solution consumed: 9.70 mL.

[0034] S4. Blank Titration Analysis: Transfer 50 mL of sodium hydroxide solution and 10 mL of barium chloride solution to an Erlenmeyer flask without samples. Insert a three-way valve with a nitrogen balloon and perform three nitrogen purgings. Place the Erlenmeyer flask in an oil bath at 80°C and stir for 25 min. After stirring, titrate while hot: Add 6 drops of phenolphthalein indicator and titrate with the standard solution until the solution color changes from red to colorless, which is the endpoint. Record the volume of hydrochloric acid standard solution consumed: 11.40 mL.

[0035] S5. The PC content is calculated to be 1.74% according to the formula.

[0036] Comparative Example 2 S1. Preparation of standard solutions and preparation of reaction solutions: Preparation of standard solutions (purchased hydrochloric acid standard solution (0.5015 mol / L)); Preparation of reaction solutions: sodium hydroxide solution concentration is 0.125 mol / L, barium chloride solution concentration is 51 g / L.

[0037] S2. Sample weighing: Place PCE-1 in a 75℃ oven and let it stand for 1 hour. Then pour 2.507 g of the sample into the conical flask.

[0038] S3. Sample Titration Analysis: Transfer 50 mL of sodium hydroxide solution and 10 mL of barium chloride solution to the conical flask containing the sample. Insert a three-way valve with a nitrogen balloon and perform three nitrogen purgings. Place the conical flask in an 80℃ oil bath and stir for 60 min. After stirring, titrate while hot: Add 6 drops of phenolphthalein indicator and titrate with the standard solution until the solution color changes from red to colorless, which is the endpoint. Record the volume of hydrochloric acid standard solution consumed: 8.60 mL.

[0039] S4. Blank Titration Analysis: Transfer 50 mL of sodium hydroxide solution and 10 mL of barium chloride solution to an Erlenmeyer flask without samples. Insert a three-way valve with a nitrogen balloon and perform three nitrogen purgings. Place the Erlenmeyer flask in an oil bath at 80°C and stir for 60 min. After stirring, titrate while hot: Add 6 drops of phenolphthalein indicator and titrate with the standard solution until the solution color changes from red to colorless, which is the endpoint. Record the volume of hydrochloric acid standard solution consumed: 11.55 mL.

[0040] S5. The PC content is calculated to be 3.01% according to the formula.

[0041] The PCE-1 sample was titrated repeatedly according to the process in Example 1, with the reaction time and temperature in S3 and S4 varied. Each experiment was repeated three times to improve accuracy. The test results are shown in Table 1. Table 1. PC content (%) obtained from tests at different temperatures and times. As shown in Table 1, the reaction temperature and reaction time both affect the PC content detection method provided by the exemplary embodiment of this disclosure. Higher reaction temperatures lead to PCE decomposition, resulting in higher PC content test results. Therefore, we selected a lower reaction temperature of 80℃. To ensure the accuracy of the test, we investigated the effect of reaction time on the test results at 80℃. The experiment found that the PC content was low after 25 minutes, indicating incomplete reaction. Between 30 and 40 minutes, the test results were stable, indicating complete reaction and no PCE decomposition. After 1 hour of reaction, the test results were high, indicating PCE decomposition. Considering all factors, we selected 80℃ and 30 minutes as the optimal reaction conditions.

[0042] The 1H NMR spectrum of the PCE-1 sample is shown below: The NMR images reveal that 5.0 ppm and 4.2 ppm belong to proton peaks on the methylene and methine groups of the polycarbonate chain; 4.9 ppm, 4.5 ppm, and 4.1 ppm belong to proton peaks on the methylene and methine groups of the five-membered ring carbonate; and 3.5-3.8 ppm belong to proton peaks on the ether chain. The integrated area of ​​a peak at a given ppm is represented by the capital letter A followed by a numerical subscript. A is an abbreviation for Area, for example, A5.0 represents the integrated area of ​​the peak at 5.0 ppm. Based on the product... 1 The integral area of ​​the 1H NMR spectrum and its associated proton peaks, and the calculation method of the mass fraction of propylene carbonate (PC%): The formula for calculating the PC mass percentage is as follows: In the formula: 102 is the sum of the molar mass of CO2 (44 g / mol) and the molar mass of propylene oxide (PO) (58 g / mol); 58 is the molar mass of propylene oxide (PO).

[0043] The formula above calculates PC% to be 2.38%, which is close to the test result in Example 1. This indicates that the method in Example 1 of this invention has high accuracy and does not require large instruments, thus facilitating cost control.

Claims

1. A method for measuring the propylene carbonate content in polycarbonate polyether polyols, characterized in that, Including the following steps: Step 1: Transfer a quantitative amount of sodium hydroxide and barium chloride solution into a container containing mass m of the sample to be tested. After stirring and mixing, add phenolphthalein indicator and titrate with hydrochloric acid standard solution until the solution changes color. Record the volume V of hydrochloric acid standard solution used. Step 2: Take the same amount of sodium hydroxide and barium chloride solution as in Step 1, stir and mix, add phenolphthalein indicator, titrate with hydrochloric acid standard solution until the solution changes color, and record the volume V0 of hydrochloric acid standard solution used for the blank sample. The propylene carbonate content in the sample to be tested was calculated as follows: Where PC% is the mass content of PC in PCE, %; V is the volume of hydrochloric acid standard solution consumed in titrating the test sample, mL; V0 is the volume of hydrochloric acid standard solution consumed in titrating the blank sample, mL; m is the mass of the PCE sample, g; and w is the hydrochloric acid concentration, mol / L.

2. The method for measuring the propylene carbonate content in polycarbonate polyether polyols according to claim 1, characterized in that, In step 1, the mass of the sample to be tested is accurate to 0.001g.

3. The method for measuring the propylene carbonate content in polycarbonate polyether polyols according to claim 1, characterized in that, Before adding sodium hydroxide and barium chloride solutions in steps 1 and 2, the air inside the container should be replaced with an inert gas.

4. The method for measuring the propylene carbonate content in polycarbonate polyether polyols according to claim 1, characterized in that, In step 1, the mixture is stirred and mixed at 80-95℃ for 15-60 minutes.

5. The method for measuring the propylene carbonate content in polycarbonate polyether polyols according to claim 1, characterized in that, In step 2, the mixture is stirred at 80-95℃ for 15-60 minutes.

6. The method for measuring the propylene carbonate content in polycarbonate polyether polyols according to claim 1, characterized in that, The hydrochloric acid standard solution is a 0.1-1 mol / L hydrochloric acid solution.

7. The method for measuring the propylene carbonate content in polycarbonate polyether polyols according to claim 1, characterized in that, The sodium hydroxide solution has a concentration of 0.125 mol / L to 0.5 mol / L; the barium chloride solution has a concentration of 40 g / L to 60 g / L.

8. The method for measuring the propylene carbonate content in polycarbonate polyether polyols according to claim 1, characterized in that, In step 1, the mass ratio of sodium hydroxide solution to barium chloride solution is 5:1 to 5:

2.

9. The method for measuring the propylene carbonate content in polycarbonate polyether polyols according to claim 1, characterized in that, The mass of sodium hydroxide added in step 1 is more than 0.1 times the mass of the sample to be tested.

10. The method for measuring the propylene carbonate content in polycarbonate polyether polyols according to claim 1, characterized in that, The sample to be tested is a polycarbonate polyether polyol containing propylene carbonate as a byproduct in the industrial production process, wherein the mass percentage of propylene carbonate is less than 50%.

Images