Derivatization liquid chromatography method for determining polyether hydroxyl value

Abstract

The invention provides a method for detecting the hydroxyl value of a polyether material. The method comprises the following steps: (1) constructing a standard quantitative system of a derivatization reagent; (2) fully reacting a to-be-detected polyether material with the excessive derivatization reagent; (3) testing the peak area of the unreacted derivatization reagent by adopting chromatography; (4) comparing with a standard quantitative system of the derivatization reagent, and calculating the content of the unreacted derivatization reagent; and (5) calculating the consumption of the derivatization reagent in the step (2) by using the calculated content of the unreacted derivatization reagent, thereby calculating the hydroxyl value of the polyether material according to the stoichiometric relationship. Wherein the derivatization reagent comprises at least one hydroxyl esterifying agent selected from the following groups: phthalic anhydride, acetic anhydride and benzoyl chloride.

Description

Technical Field

[0001] This application relates to the field of analytical testing technology, specifically to a method for determining the hydroxyl value in polyethers using derivatization liquid chromatography, which features high sensitivity, speed, and broad applicability. Background Technology

[0002] Specialty polyethers, with their high mechanical strength, excellent heat resistance, and outstanding dimensional stability, have shown broad application prospects in high-end electronics, automotive lightweighting, precision instruments, and medical equipment. Due to their good chemical resistance, electrical insulation, and molding and processing properties, these materials are considered an ideal class of high-performance engineering plastics, greatly promoting the development of strategic emerging industries such as high-end manufacturing and intelligent equipment. The widespread application of specialty polyethers helps improve the technological content and reliability of end products, and is of great significance to the technological upgrading and material innovation of related industries.

[0003] In the performance evaluation of specialty polyethers, the hydroxyl value is a key indicator for measuring molecular structure and reprocessing reactivity. Currently, the industry generally adopts the titration method specified in GB / T 12008.3-2009 Plastics Polyether Polyols Part 3: Determination of Hydroxyl Value for analysis, which includes sample acylation, solution transfer, titration and calculation. However, this national standard method has revealed several shortcomings in practical applications: (1) The method is mainly for macro-analysis, with limited sensitivity, making it difficult to meet the high-precision testing requirements for trace and ultra-trace hydroxyl values ​​of specialty polyphenylene ether materials; (2) If coexisting impurities are present in the sample, the titration method cannot effectively distinguish them, easily leading to false positives or analytical interference, affecting the accuracy and reproducibility of the test results; (3) The operation process is cumbersome and requires a lot of manual intervention, with long detection cycles and large operational errors, which is not conducive to the realization of automation and high-throughput detection requirements. These shortcomings urgently require breakthroughs in more advanced analytical testing technologies in the context of high-quality development of the specialty polyphenylene ether industry and innovation in new materials.

[0004] Therefore, there is an urgent need in the field to develop an improved method for detecting the hydroxyl value of polyether materials, which has high sensitivity and can meet the high-precision testing requirements for trace and ultra-trace hydroxyl values ​​of special polyphenylene ether materials. The inventors of this application have discovered that after efficient derivatization of polyether materials, selective and quantitative detection of hydroxyl values ​​can be achieved through high-performance liquid chromatography (HPLC). Compared with traditional titration methods, the method of this application has several significant advantages: (1) The sensitivity of this method is much higher than that of conventional titration, and it can accurately determine the hydroxyl value in low-concentration and complex samples; (2) By using chromatographic separation and characteristic signal detection, it can effectively eliminate impurity interference and ensure the specificity and accuracy of the analytical results; (3) The overall process is highly automated and easy to operate, which greatly improves the detection efficiency and data stability, and meets the needs of large-scale and high-throughput testing. Summary of the Invention

[0005] The first aspect of the present invention provides a method for detecting the hydroxyl value of a polyether material, the method comprising the following steps:

[0006] (1) Construct a standard quantitative system for derivatization reagents.

[0007] (2) React the polyether material to be tested with an excess of derivatizing reagent until fully reacted;

[0008] (3) The peak area of ​​unreacted derivatization reagents was tested by chromatography;

[0009] (4) Calculate the content of unreacted derivatizing reagent by comparing it with the standard quantitative system of the derivatizing reagent;

[0010] (5) The amount of derivatizing reagent consumed in step (2) is obtained by using the calculated content of unreacted derivatizing reagent, and then the hydroxyl value of the polyether material is calculated according to the stoichiometric relationship.

[0011] The derivatizing agent includes at least one hydroxyl esterifying agent selected from the group consisting of phthalic anhydride, acetic anhydride, and benzoyl chloride.

[0012] A second aspect of the invention provides the use of chromatography in detecting the hydroxyl value of a polyether material, wherein the polyether material is fully reacted with an excess of a derivatizing agent, and the peak area of ​​the unreacted derivatizing agent is tested by chromatography; the content of the unreacted derivatizing agent and the amount of derivatizing agent consumed are calculated by comparing with a standard quantitative system of the derivatizing agent, thereby calculating the hydroxyl value of the polyether material according to stoichiometry, wherein the derivatizing agent comprises at least one hydroxyl esterifying agent selected from the group consisting of phthalic anhydride, acetic anhydride, and benzoyl chloride.

[0013] A third aspect of the invention provides the use of a derivatizing reagent in the chromatographic determination of the hydroxyl value of polyether materials, wherein the derivatizing reagent comprises at least one hydroxyl esterifying agent selected from the group consisting of phthalic anhydride, acetic anhydride, and benzoyl chloride. Detailed Implementation

[0014] This invention addresses the shortcomings of existing methods for detecting the hydroxyl value of polyether materials, such as insufficient sensitivity, poor anti-interference ability, and complex operation. It provides a highly sensitive quantitative analysis method for hydroxyl value based on derivatization liquid chromatography, enabling accurate determination of the hydroxyl content in specialty polyethers and other polymeric materials. This method is applicable not only to samples within the conventional hydroxyl value range but also exhibits excellent performance for polyether materials with extremely low hydroxyl content or complex matrices, particularly meeting the high standards required for the research and development of specialty polymeric materials and product quality control.

[0015] Unless otherwise specified in this specification, the components or their preferred components may be combined to form new technical solutions.

[0016] Unless otherwise specified in this specification, all the embodiments and preferred embodiments mentioned can be combined to form new technical solutions.

[0017] Unless otherwise specified in this specification, all the technical features and preferred features mentioned can be combined to form new technical solutions.

[0018] Unless otherwise specified, the term "a" as used in this specification means "at least one".

[0019] Unless otherwise specified, all percentages, parts, etc. in this specification refer to weight.

[0020] The "range" disclosed herein takes the form of a lower limit and an upper limit. It can be one or more lower limits and one or more upper limits, respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower and upper limits define the boundaries of the particular range. All ranges that can be defined in this way are inclusive and composable, meaning that any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is also expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0021] Unless otherwise specified in this specification, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0022] In this specification, unless otherwise specified, the terms "comprising" and "including" as used herein can be open-ended or closed-ended. For example, "comprising" and "including" may mean that other components not listed may also be included, or that only the listed components may be included.

[0023] This application provides a method for detecting the hydroxyl value of polyether materials, the method comprising the following steps:

[0024] (1) Construct a standard quantitative system for derivatization reagents;

[0025] (2) React the polyether material to be tested with an excess of derivatizing reagent until fully reacted;

[0026] (3) The peak area of ​​unreacted derivatization reagents was tested by chromatography;

[0027] (4) Calculate the content of unreacted derivatizing reagent by comparing it with the standard quantitative system of the derivatizing reagent;

[0028] (5) The amount of derivatizing reagent consumed in step (2) is obtained by using the calculated content of unreacted derivatizing reagent, and then the hydroxyl value of the polyether material is calculated according to the stoichiometric relationship.

[0029] The derivatizing agent is at least one hydroxyl esterifying agent selected from the group consisting of phthalic anhydride, acetic anhydride, and benzoyl chloride.

[0030] In this application, the step of constructing a standard quantitative system for derivatization reagents includes accurately preparing a series of standard solutions of derivatization reagents with known concentrations, determining the peak area of ​​each standard solution using chromatography, and establishing a linear regression equation through fitting to obtain a peak area-concentration standard curve, providing a quantitative basis for the subsequent determination of the hydroxyl content of the sample. The methods for preparing the standard solutions of derivatization reagents and constructing the peak area-concentration standard curve are conventional, and those skilled in the art can easily perform the above preparation and construction based on existing technology.

[0031] In this application, the derivatization reaction of the polyether material to be tested includes reacting the polyether material to be tested with a derivatization reagent in an equivalent ratio of 1:2-1:10, preferably 1:2-1:5, more preferably 1:2.5-1:4, with strict control of reaction time and temperature to ensure that the hydroxyl groups in the sample are fully esterified.

[0032] In this application, the peak area of ​​the unreacted derivatizing reagent can be tested by chromatography after the derivatization reaction is completed, by hydrolyzing the unreacted derivatizing reagent and then testing the peak area of ​​the hydrolyzed unreacted derivatizing reagent by chromatography.

[0033] In this application, step (4) includes substituting the peak area of ​​the hydrolyzed derivatized reagent obtained by chromatography into the peak area-concentration standard curve of the standard quantitative system of the derivatized reagent to calculate the content of unreacted derivatized reagent.

[0034] In this application, step (5) includes calculating the hydroxyl value of the polyether material according to the following formula:

[0035] mg KOH / g=(m0*x0-m1*x)*56.1*2 / (m*1000)

[0036] In the formula:

[0037] x0 — concentration of the derivatizing reagent, in mmol / kg;

[0038] x — The concentration of unreacted derivatizing reagent calculated from the standard curve, in mmol / kg;

[0039] m0 — Mass of derivatizing reagent added, in grams;

[0040] m1—Mass of the reaction solution after the derivatization reaction, in grams;

[0041] m — the mass of the polyether material to be tested, in grams.

[0042] In this application, the chromatographic method includes, but is not limited to, gas chromatography and liquid chromatography. Preferably, the chromatographic method is high-performance liquid chromatography (HPLC). HPLC has incomparable advantages over titration. Titration can only determine the total amount of acidic substances in the sample and is easily affected by impurities and coexisting reactive substances in the sample, affecting the specificity of the results. At the same time, titration is suitable for constant or high concentration ranges, and the error is significant for trace analysis; while HPLC can not only separate target components in complex mixed systems at high resolution, but also has a lower detection limit, making it particularly suitable for the detection of samples with low hydroxyl values. In addition, HPLC has a high degree of automation, eliminating the uncertainty of human endpoint determination in titration, improving the reproducibility and objectivity of the results, and enabling high-throughput rapid detection. By reasonably setting chromatographic conditions and standard calibration, the sample repeatability and accuracy (RSD) of chromatographic detection are better than 2%, which is much higher than that of titration. In addition, chromatographic methods consume less sample, requiring only trace amounts to complete accurate analysis, further reducing experimental costs and environmental burden.

[0043] In this application, the derivatizing agent refers to a hydroxyl esterifying agent that reacts with the hydroxyl groups in the polyether material to form a stable ester, including but not limited to phthalic anhydride, acetic anhydride, and benzoyl chloride. Preferably, the derivatizing agent is phthalic anhydride. Phthalic anhydride is used as the esterifying agent because its physicochemical properties are most suitable for the HPLC analysis system used in this invention, which helps to ensure the stability and reliability of the hydroxyl value determination results.

[0044] In this application, the hydroxyl content of the polyether material is less than 500 mg KOH / g, preferably less than 200 mg KOH / g, more preferably less than 100 mg KOH / g, and even more preferably less than 50 mg KOH / g. Compared with titration, the method of this application is particularly suitable for the detection of polyether samples with low hydroxyl values. The method of this invention has a detection limit as low as 20 mg KOH / g, and its repeatability and determination range are superior to the national standard method, meeting the needs of high-tech fields such as special polyether materials for precise and sensitive analysis.

[0045] In one example, step (1) includes selecting phthalic acid as a quantitative standard, accurately preparing a series of phthalic acid standard solutions of known concentrations, determining the peak area of ​​each standard solution by HPLC, and establishing a linear regression equation by fitting.

[0046] Step (2) involves esterifying the polyether material to be tested with excess phthalic anhydride. The stoichiometric ratio of the polyether material to the phthalic anhydride is 1:2-1:10, preferably 1:2-1:5, and more preferably 1:2.5-1:4. The reaction time and temperature are strictly controlled to ensure that the hydroxyl groups in the sample are fully esterified with the phthalic anhydride. There are no particular restrictions on the reaction time and temperature, as long as the reaction objective is met. Preferably, the reaction temperature is 90-150℃, more preferably 100-120℃; and the reaction time is 10-60 minutes, more preferably 20-40 minutes.

[0047] After the esterification reaction is completed, a certain amount of water is added to convert the excess phthalic anhydride into free phthalic acid. The peak area of ​​the free phthalic acid is measured by HPLC. The measured peak area of ​​the free phthalic acid is substituted into the peak area-concentration standard curve of the standard quantitative system in step (1) to calculate the content of unreacted phthalic anhydride.

[0048] The actual amount of phthalic anhydride consumed in the esterification reaction is calculated by the difference between the initial amount of phthalic anhydride added and the amount of unreacted anhydride. Based on the stoichiometric relationship between phthalic anhydride and hydroxyl groups, the hydroxyl content in the sample can be accurately calculated, enabling precise quantitative determination of the hydroxyl value of polyethers.

[0049] The method of this invention has the following significant advantages: First, it is significantly superior to traditional titration methods in terms of sensitivity, capable of detecting hydroxyl values ​​as low as 20 mg KOH / g, making it suitable for the analysis of trace and ultra-trace components. Second, combining the specificity of derivatization and the advantages of chromatographic separation greatly enhances the method's anti-interference ability and the specificity and accuracy of the determination results; it is also applicable to samples with complex matrices and impurities, effectively reducing false positives or errors. Third, the overall experimental procedure is highly automated and easy to operate, compatible with multiple coupled detection methods such as chromatography-UV or mass spectrometry, significantly improving experimental efficiency and data stability, and easily applicable to high-throughput detection scenarios. Verification by examples shows that the relative standard deviation (RSD) of the method is less than 2%, indicating its excellent repeatability and reliability.

[0050] The derivatized HPLC hydroxyl value detection method described in this invention can systematically solve the problems of accuracy, sensitivity and efficiency in detecting hydroxyl content in polymer materials such as polyethers. It provides strong technical support for the performance evaluation and quality improvement of special polyethers in high-end electronics, automobiles, medical and new materials fields, and has good prospects for industrial application and important engineering promotion value.

[0051] This application also provides the use of chromatography in detecting the hydroxyl value of polyether materials, wherein the polyether material is fully reacted with an excess of derivatizing reagent, and the peak area of ​​the unreacted derivatizing reagent is tested by chromatography; the content of the unreacted derivatizing reagent and the amount of derivatizing reagent consumed are calculated by comparing with a standard quantitative system of the derivatizing reagent, thereby calculating the hydroxyl value of the polyether material according to stoichiometry, wherein the derivatizing reagent is at least one hydroxyl esterifying agent selected from the group consisting of phthalic anhydride, acetic anhydride, and benzoyl chloride.

[0052] This application also provides the use of a derivatizing reagent in the chromatographic determination of the hydroxyl value of polyether materials, wherein the derivatizing reagent is at least one hydroxyl esterifying agent selected from the group consisting of phthalic anhydride, acetic anhydride, and benzoyl chloride.

[0053] The method of this invention not only improves the sensitivity and accuracy of quantitative detection of hydroxyl values ​​in low-concentration and complex sample systems, but is also simple to operate, efficient, consumes little sample, and is environmentally friendly, making it highly valuable for widespread application.

[0054] Example

[0055] The present invention will now be described in further detail with reference to embodiments. However, it should be understood that these embodiments are provided for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless specific conditions are specified, are generally determined according to national standards. If no corresponding national standard exists, then common international standards, conventional conditions, or conditions recommended by the manufacturer are followed. Unless otherwise stated, all parts are parts by weight, and all percentages are weight percentages.

[0056] Raw material sources and preparation

[0057] Main reagents for the experiment

[0058]

[0059]

[0060] Instrument Name model factory Analytical balance MX204 / A Mettler Toledo Technologies (China) Co., Ltd. Oil bath HB eco Aika (Guangzhou) Instrument Equipment Co., Ltd. digestion tube 100mL Guangzhou Gedana Instruments Co., Ltd. High Performance Liquid Chromatography 1260InfinityⅡ Agilent Technologies High-temperature digestion apparatus DS-360-25H Guangzhou Gedana Instruments Co., Ltd. Iodine flask 100mL Chongqing Xinweier Glass Co., Ltd. potentiometric titrator OMNIS Mystery Generation MassMutual China Ltd.

[0061] Example 1:

[0062] Weigh 1.0 g (accurate to 0.0001 g) of phthalic anhydride into a brown bottle, add 100 g of pyridine and shake vigorously until the phthalic anhydride dissolves to prepare a 1% phthalic anhydride-pyridine solution, the concentration of which is recorded as x0, and let stand.

[0063] Weigh 0.30 g of polyphenylene ether standard 1 into a dry digestion tube, and record this as m. Add 20 mL of the prepared phthalic anhydride pyridine solution to the digestion tube, subtract the mass of the conical flask, and weigh the resulting product, recording this as m0. Connect a condenser to the conical flask and reflux at 120°C for 30 min. After cooling to room temperature, weigh the resulting product, subtract the mass of the conical flask, and record this as m1.

[0064] Weigh 0.50 g of potassium hydrogen phthalate into a 50 mL volumetric flask, dilute to volume with purified water, and sonicate to dissolve, preparing a 1% potassium hydrogen phthalate stock solution with a molar concentration of 49 mmol / kg. Take 0.35, 0.50, 0.90, 1.10, and 1.30 g of the above potassium hydrogen phthalate stock solution into 50 mL volumetric flasks, dilute to volume with purified water, and sonicate for 30 min to prepare stock standard solutions with molar concentrations of 0.334, 0.502, 0.896, 1.095, and 1.303 mmol / kg, respectively.

[0065] The prepared standard sample was analyzed by HPLC under the following conditions:

[0066] Chromatographic column: C18 (4.6*250mm*5μm); mobile phase: 0.05% phosphate (sodium dihydrogen phosphate, disodium hydrogen phosphate) aqueous solution (A) and acetonitrile (B), the gradient elution program of the mobile phase is shown in Table 1; flow rate: 1.0mL / min; detection wavelength: 210nm; column temperature: 30℃; injection volume: 5.0μL.

[0067] Table 1 Liquid Chromatography Conditions

[0068]

[0069] Figure 1 The liquid chromatogram is shown for a phthalic acid standard with a concentration of 0.334 mmol / kg. The peak areas of the target components were recorded (Table 2), and a linear regression equation was established by fitting the data to plot the peak area-concentration standard curve (Table 3).

[0070] Table 2

[0071]

[0072] Table 3 Linear Equations

[0073]

[0074] Where X represents the peak area of ​​phthalic acid, and Y represents the concentration of phthalic acid (in mmol / kg).

[0075] Weigh 1.0 g of the derivatized sample solution into a 50 mL volumetric flask, dilute to volume with purified water, sonicate for 30 min, filter, and perform liquid chromatography analysis to obtain the characteristic peak area S of phthalic acid. Substitute the peak area of ​​phthalic acid into the peak area-concentration standard curve in Table 3 to obtain the phthalic acid content x in the reaction solution.

[0076] Substitute the measured data into the following formula to calculate the hydroxyl content in polyphenylene ether.

[0077] mg KOH / g=(m0*x0-m1*x)*56.1*2 / (m*1000)

[0078] In the formula:

[0079] x0 — Concentration of phthalic anhydride, the derivatizing reagent, in mmol / kg;

[0080] x—The concentration of residual phthalic anhydride in the reaction solution is calculated from the standard curve, in mmol / kg;

[0081] m0 — Mass of derivatizing reagent added, in grams;

[0082] m1—Mass of the reaction solution after derivatization in the conical flask, in grams;

[0083] m — the mass of the polyether material to be tested, in grams.

[0084] Next, weigh 0.30g of polyphenylene ether standard sample 2, 0.30g of polyphenylene ether standard sample 3, 0.30g of polyphenylene ether standard sample 4, and 0.30g of polyphenylene ether standard sample 5 respectively, and test polyphenylene ether standards with different hydroxyl values ​​according to the same steps as above. The results are shown in the table below:

[0085] Table 4. Hydroxyl value test results

[0086]

[0087] The relative errors of the detection results were all <2%, indicating that the hydroxyl detection method of the present invention has high accuracy.

[0088] Example 2

[0089] Following the steps described in Example 1, acetic anhydride was used as the derivatization reagent, and the residual acetic acid was quantitatively analyzed by liquid chromatography to analyze polyphenylene ether standards with different hydroxyl values. The results are as follows:

[0090] Table 5

[0091]

[0092] As shown in Table 5, acetic anhydride, as a derivatization reagent, exhibits relatively small errors in detecting polyphenylene ether standards with a hydroxyl content of 500 mg KOH / g. However, the accuracy decreases significantly when detecting polyphenylene ether standards with lower hydroxyl content. The hydrolysis products of acetic anhydride have short retention times in liquid chromatography and poor UV absorption signals, making it impossible to obtain a reliable linear regression equation, thus resulting in larger errors in the calculation results.

[0093] Example 3

[0094] Following the method and steps described in Example 1, different derivatization conditions were used to analyze a polyphenylene ether standard with a hydroxyl value of 499.2 mg KOH / g. The results are as follows:

[0095] Table 6

[0096]

[0097] As can be seen from Table 6, the derivatization reaction conditions affect the degree of reaction completion. Under the reaction conditions of 80℃, more than 80% of the reaction was completed in 30 minutes, and under the reaction conditions of 120℃, more than 95% of the reaction was completed in 10 minutes. Therefore, the preferred derivatization reaction condition is 120℃, which completes the derivatization reaction 100% within 30 minutes.

[0098] Comparative Example 1: Chemical Titration Method for Determining Hydroxyl Value

[0099] Prepare a 1% phthalic anhydride pyridine solution using the same method and steps as in Example 1. Weigh 0.30 g of polyphenylene ether standard sample 1 (denoted as m) into a dry digestion tube, taking care not to get the sample on the ground glass joint of the digestion tube during sampling. Accurately transfer 20 mL of phthalic anhydride pyridine solution into the digestion tube using a pipette, again avoiding contact with the ground glass joint of the digestion tube to prevent errors. Add a few boiling stones, place the digestion tube on the digestion apparatus, and connect a spindle-shaped fractionating column to the digestion tube. Reflux at 120°C for 60 min. Remove the digestion tube and cool to room temperature. Add 2 mL of water from the top of the spindle-shaped fractionating column using a disposable dropper. Return the digestion tube to the digestion apparatus and continue heating at 120°C for 10 min. After digestion, remove the digestion tube and place it on a sample rack to cool to room temperature. Rinse the fractionating column with 5 mL of ethanol. Two blank samples must be prepared as controls.

[0100] The solution was transferred three times with a 20% toluene-ethanol solution to a disposable cup. The cups were placed on the titration stage of an automatic titrator, and the solution was titrated to pH 10 using a potentiometric titrator. The volume of sodium hydroxide-ethanol standard solution consumed was recorded as v. A blank control group was also prepared, and the volume of sodium hydroxide-ethanol standard solution consumed was recorded as v0.

[0101] Calculate using the following formula:

[0102] mg KOH / g = (v0 - v) * c * 56.1 / m

[0103] In the formula:

[0104] v0—The volume of sodium hydroxide-ethanol standard solution consumed in the blank titration, in mL;

[0105] v—The volume of sodium hydroxide-ethanol standard solution consumed in the titration of the sample, in mL;

[0106] c—Concentration of sodium hydroxide-ethanol standard solution, in mol / L;

[0107] m — Sample mass, in grams.

[0108] Next, weigh 0.30g of polyphenylene ether standard sample 2, 0.30g of polyphenylene ether standard sample 4, and 0.30g of polyphenylene ether standard sample 5 respectively, and titrate the polyphenylene ether standard samples with different hydroxyl values ​​according to the same steps as above. The results are shown in the table below:

[0109] Table 7

[0110]

[0111] As shown in Table 7, the method for detecting the hydroxyl content of polyphenylene ether provided in this application has a smaller error compared with the titration method when detecting polyphenylene ether standards with a hydroxyl content of 500 mg KOH / g. The advantage is even more pronounced when detecting polyphenylene ether standards with lower hydroxyl content. For polyphenylene ether standards with low hydroxyl content, the precision of the titration method decreases significantly. In the analysis of low hydroxyl content, the chromatographic method is significantly superior to the titration method.

Claims

1. A method for detecting the hydroxyl value of a polyether material, the method comprising the following steps: (1) Construct a standard quantitative system for derivatization reagents. (2) React the polyether material to be tested with an excess of derivatizing reagent until fully reacted; (3) The peak area of ​​unreacted derivatization reagents was tested by chromatography; (4) Calculate the content of unreacted derivatizing reagent by comparing it with the standard quantitative system of the derivatizing reagent; (5) The amount of derivatizing reagent consumed in step (2) is obtained by using the calculated content of unreacted derivatizing reagent, and then the hydroxyl value of the polyether material is calculated according to the stoichiometric relationship. The derivatizing agent includes at least one hydroxyl esterifying agent selected from the group consisting of phthalic anhydride, acetic anhydride, and benzoyl chloride, preferably, the derivatizing agent being phthalic anhydride.

2. The method as described in claim 1, characterized in that, Step (1) includes accurately preparing a series of derivatization reagent standard solutions with known concentrations, determining the peak area of ​​each standard solution by chromatography, and establishing a linear regression equation by fitting to obtain a peak area-concentration standard curve.

3. The method as described in claim 1 or 2, characterized in that, Step (3) includes hydrolyzing the unreacted derivatizing reagent after the reaction is completed, and using chromatography to test the peak area of ​​the hydrolyzed unreacted derivatizing reagent.

4. The method as described in claim 1 or 2, characterized in that, The reaction temperature of step (2) is 90-150℃, preferably 100-120℃; and / or the reaction time of step (2) is 10-60 minutes, preferably 20-40 minutes; and / or the equivalent ratio of the polyether material to be tested to the derivatizing reagent is 1:2.5-1:

4.

5. The method as described in claim 2, characterized in that, Step (4) involves substituting the peak area of ​​the hydrolyzed derivatized reagent obtained by chromatography into the peak area-concentration standard curve of the standard quantitative system of the derivatized reagent to calculate the content of unreacted derivatized reagent.

6. The method as described in claim 1 or 2, characterized in that, Step (5) includes calculating the hydroxyl value of the polyether material according to the following formula: mg KOH / g=(m0*x0-m1*x)*56.1*2 / (m*1000) In the formula: x0 — concentration of the derivatizing reagent, in mmol / kg; x — The concentration of unreacted derivatizing reagent calculated from the standard curve, in mmol / kg; m0 — Mass of derivatizing reagent added, in grams; m1—Mass of the reaction solution after the derivatization reaction, in grams; m — the mass of the polyether material to be tested, in grams.

7. The method as described in claim 1 or 2, characterized in that, The chromatographic method used is high performance liquid chromatography.

8. The method as described in claim 1 or 2, characterized in that, The hydroxyl content of the polyether material is less than 500 mg KOH / g, preferably less than 200 mg KOH / g, more preferably less than 100 mg KOH / g, and even more preferably less than 50 mg KOH / g.

9. The use of chromatography in the determination of the hydroxyl value of polyether materials, wherein the polyether material is fully reacted with an excess of derivatizing reagent, and the peak area of ​​the unreacted derivatizing reagent is tested by chromatography; by comparing with a standard quantitative system of the derivatizing reagent, the content of the unreacted derivatizing reagent and the amount of derivatizing reagent consumed are calculated, thereby calculating the hydroxyl value of the polyether material according to stoichiometry, wherein the derivatizing reagent is at least one hydroxyl esterifying agent selected from the group consisting of phthalic anhydride, acetic anhydride, and benzoyl chloride.

10. Use of a derivatizing reagent in the chromatographic determination of the hydroxyl value of polyether materials, wherein the derivatizing reagent is at least one hydroxyl esterifying agent selected from the group consisting of phthalic anhydride, acetic anhydride, and benzoyl chloride.

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