Method for testing hydroxyl value of aqueous composition and application thereof

Abstract

The application discloses a hydroxyl value testing method of a water-based composition and application thereof, relates to the field of chemical or physical property testing of materials, and comprises the following steps: mixing the water-based composition with a solvent mixture, stirring until complete dissolution, and obtaining a water-based composition solution; adding boric acid into the water-based composition solution, controlling pH, carrying out constant-temperature water bath reaction, avoiding boiling, obtaining a mixture, testing after cooling, and completing the hydroxyl value testing. The application uses boric acid to replace pyridine and imidazole, avoids the use of harmful reagents, and has no complex derivatization or dangerous by-products; compared with a traditional method, the testing steps are simpler and more convenient. The application not only simplifies operation steps, but also reduces energy consumption and equipment requirements.

Description

Technical Field

[0001] This invention relates to the field of testing the chemical or physical properties of materials, and specifically to a method for testing the hydroxyl value of an aqueous composition and its application. Background Technology

[0002] Polyethers and polyols are important chemical raw materials in the field of chemical synthesis. Hydroxyl value is a crucial indicator in the production and reaction processes of polyethers and polyols. Currently, the national standard GB / T12008.3-2009 specifies a quantitative method using phthalic anhydride acylation and acid-base titration with pyridine or imidazole as an acid-binding agent. However, pyridine or imidazole are toxic and hazardous reagents, posing significant environmental risks and increasing testing risks. While nuclear magnetic resonance (NMR) methods exist for hydroxyl value testing, they require large instruments, have high detection thresholds, and are inconvenient for use as experimental progress markers. Therefore, developing a non-toxic, low-hazard method without complex derivatization or hazardous byproducts, and that does not require large instruments, is crucial.

[0003] Chinese invention patent CN117405823B discloses a method for determining the hydroxyl value of polylactide polyols and its application. It employs a non-aqueous titration method and a solution composed of an amine organic base and an acylation reagent, ensuring that the polylactide polyol does not precipitate during titration, thus improving the accuracy of hydroxyl value determination. However, the use of imidazole catalysts poses certain hazards to human health and the environment. Chinese invention patent CN115901833B discloses a method for determining the hydroxyl value of polyether polyols using phosphorus nuclear magnetic resonance spectroscopy. This method involves derivatization with phosphoryl chloride compounds, the addition of an internal standard, and quantification using the internal standard method based on the different chemical shifts in the NMR spectra of the sample and the internal standard. It features a small relative standard deviation, high precision, simple analytical method, low pollution, and short testing time. However, it requires an NMR instrument, resulting in a high detection threshold and high testing cost. Summary of the Invention

[0004] To develop a non-toxic, low-hazard detection method free from complex derivatization or hazardous byproducts, and without the need for large instruments, the first aspect of this invention provides a method for testing the hydroxyl value of an aqueous composition, comprising the following steps:

[0005] The aqueous composition is mixed with a solvent mixture and stirred until completely dissolved to obtain an aqueous composition solution;

[0006] Boric acid was added to the aqueous composition solution, the pH was controlled, and the reaction was carried out in a constant temperature water bath to avoid boiling. The resulting mixture was cooled and then tested to complete the hydroxyl value test.

[0007] As one implementation method, the cooling test method is as follows: add phenolphthalein indicator to the mixture, titrate with sodium hydroxide standard solution, a light pink endpoint appears, and record the volume V2 consumed;

[0008] Add phenolphthalein indicator to boric acid in an aqueous solution of the composition, titrate with sodium hydroxide standard solution, and a light pink endpoint is obtained. Record the volume V1 consumed.

[0009] Calculate the hydroxyl value using the formula.

[0010] As one implementation method, the formula is: OHV (mg KOH / g) = V1: Volume of NaOH consumed in titration when the composition solution is non-aqueous (mL); V2: Volume of NaOH consumed in titration when the composition solution is aqueous (mL); M NaOH : Molar concentration of sodium hydroxide standard solution (mol / L); W: Mass of aqueous composition (g); 56.1: Equivalent mass of KOH.

[0011] As one implementation method, the reaction time of the constant temperature water bath reaction is 10-20 minutes.

[0012] In one embodiment, the reaction time of the constant temperature water bath reaction is 15 minutes.

[0013] As one implementation method, the reaction temperature of the constant temperature water bath reaction is 30-50℃.

[0014] As one implementation method, the reaction temperature of the constant temperature water bath reaction is 40°C.

[0015] In one embodiment, the pH is 6.5-7.5.

[0016] In one implementation, the pH is 7.

[0017] In one embodiment, the boric acid is a mixture of boric acid and tertiary water, and the molar concentration of the mixture of boric acid and tertiary water is 0.7-1.0M.

[0018] In one embodiment, the molar concentration of the mixture of boric acid and tertiary water is 0.7-0.8 M.

[0019] In one embodiment, the molar concentration of the mixture of boric acid and tertiary water is 0.787 M.

[0020] In one embodiment, the molar concentration of the sodium hydroxide standard solution is 0.3-0.8M.

[0021] In one embodiment, the molar concentration of the sodium hydroxide standard solution is 0.5M.

[0022] In one embodiment, the solvent mixture is a mixture of ethanol and water, wherein the volume ratio of ethanol to water is 1:(1-3).

[0023] In one embodiment, the volume ratio of ethanol to water is 1:1.

[0024] In one embodiment, the mass-to-volume ratio of the aqueous composition to the solvent mixture is (1-1.5g):20mL.

[0025] In one embodiment, the phenolphthalein indicator is prepared by dissolving 0.5g of phenolphthalein in 50mL of anhydrous ethanol.

[0026] A second aspect of the present invention provides an application of a method for testing the hydroxyl value of an aqueous composition, applicable to the testing of the hydroxyl value of polyether compounds or polyol compounds.

[0027] In one embodiment, the polyether compound includes, but is not limited to, at least one of OP-7 emulsifier, propylene glycol block polyether, and polyoxyethylene polyoxypropylene ether block copolymer.

[0028] In one embodiment, the polyol compound includes, but is not limited to, at least one of polyethylene glycol.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The hydroxyl value test method of the aqueous composition of the present invention uses boric acid instead of pyridine and imidazole, which avoids the use of harmful reagents and has no complicated derivatization or dangerous by-products. The test steps are simpler and more convenient than the method of GB / T 12008.3-2009.

[0031] (2) The hydroxyl value test method of the aqueous composition of the present invention adopts the boric acid complexation method. Boric acid coordinates with hydroxyl to form a strong acidic complex acid, which can be titrated with sodium hydroxide. The hydroxyl value is determined by the difference between the coordinated and uncoordinated acid, which provides a new idea for the determination of the hydroxyl value of aqueous compositions.

[0032] (3) The hydroxyl value test method of the aqueous composition of the present invention uses a reaction time of 15 min, a reaction temperature of 40 °C, and a pH of 7, which can improve the stability of the reaction and avoid the decomposition of the complex, thus preventing inaccurate detection.

[0033] (4) The hydroxyl value test method of the aqueous composition of the present invention has mild reaction conditions and can be carried out at 70°C without the need for a high-temperature reflux device. This not only simplifies the operation steps, but also reduces energy consumption and equipment requirements.

[0034] (5) The hydroxyl value test method of the aqueous composition of the present invention shortens the reaction time, and the reaction can be completed in 15 minutes. Compared with the traditional 1h acylation reaction, the analysis efficiency has been significantly improved. Furthermore, the readily available reagent boric acid is used, and the reaction process is safe, environmentally friendly, energy-saving and low-consumption. Detailed Implementation

[0035] Example 1

[0036] A method for testing the hydroxyl value of an aqueous composition, comprising the following steps:

[0037] The aqueous composition is mixed with a solvent mixture and stirred until completely dissolved to obtain an aqueous composition solution;

[0038] Boric acid was added to the aqueous composition solution, ammonia was used to control the pH, and the reaction was carried out in a constant temperature water bath to avoid boiling, resulting in a mixture. After cooling, the mixture was ready for testing.

[0039] Add phenolphthalein indicator to the mixture, titrate with sodium hydroxide standard solution until a light pink endpoint appears, and record the volume V2 consumed;

[0040] Add phenolphthalein indicator to boric acid in an aqueous solution of the composition, titrate with sodium hydroxide standard solution, and a light pink endpoint is obtained. Record the volume V1 consumed.

[0041] Calculate the hydroxyl value using the formula. Perform 6 parallel tests.

[0042] The formula is: OHV (mg KOH / g) = V1: Volume of NaOH consumed in titration when the composition solution is non-aqueous (mL); V2: Volume of NaOH consumed in titration when the composition solution is aqueous (mL); M NaOH : Molar concentration of sodium hydroxide standard solution (mol / L); W: Mass of aqueous composition (g).

[0043] The reaction time for the constant temperature water bath reaction is 15 minutes.

[0044] The reaction temperature of the constant temperature water bath reaction is 40℃.

[0045] The pH value is 7.

[0046] The boric acid is a mixture of boric acid and tertiary water, and the molar concentration of the mixture is 0.787M.

[0047] The molar concentration of the sodium hydroxide standard solution is 0.5M.

[0048] The solvent mixture is a mixture of ethanol and water, with a volume ratio of ethanol to water of 1:1.

[0049] The mass-to-volume ratio of the aqueous composition to the solvent mixture is 1.25 g: 20 mL.

[0050] The phenolphthalein indicator is prepared by dissolving 0.5g of phenolphthalein in 50mL of anhydrous ethanol.

[0051] The aqueous composition is polyethylene glycol, purchased from Haian Petrochemical Plant in Jiangsu Province, with the grade PEG-1000.

[0052] The aqueous composition is OP-7 emulsifier, purchased from McLean.

[0053] The performance test results are shown in Table 1.

[0054] Comparative Example 1

[0055] A method for testing the hydroxyl value of an aqueous composition, the specific implementation of which is the same as in Example 1, except that the reaction time of the constant temperature water bath reaction is 5 min.

[0056] Comparative Example 2

[0057] A method for testing the hydroxyl value of an aqueous composition, the specific implementation of which is the same as in Example 1, except that the reaction time of the constant temperature water bath reaction is 10 min.

[0058] Comparative Example 3

[0059] A method for testing the hydroxyl value of an aqueous composition, the specific implementation method is the same as in Example 1, except that the reaction time of the constant temperature water bath reaction is 20 min.

[0060] Comparative Example 4

[0061] A method for testing the hydroxyl value of an aqueous composition, the specific implementation method is the same as in Example 1, except that the reaction time of the constant temperature water bath reaction is 25 min.

[0062] Comparative Example 5

[0063] A method for testing the hydroxyl value of an aqueous composition, the specific implementation method is the same as in Example 1, except that the reaction time of the constant temperature water bath reaction is 30 min.

[0064] Comparative Example 6

[0065] A method for testing the hydroxyl value of an aqueous composition, the specific implementation method is the same as in Example 1, except that the reaction time of the constant temperature water bath reaction is 45 min.

[0066] Comparative Example 7

[0067] A method for testing the hydroxyl value of an aqueous composition, the specific implementation method is the same as in Example 1, except that the reaction time of the constant temperature water bath reaction is 60 min.

[0068] Comparative Example 8

[0069] A method for testing the hydroxyl value of an aqueous composition, the specific implementation of which is the same as in Example 1, except that the pH is 5.0.

[0070] Comparative Example 9

[0071] A method for testing the hydroxyl value of an aqueous composition, the specific implementation of which is the same as in Example 1, except that the pH is 6.0.

[0072] Comparative Example 10

[0073] A method for testing the hydroxyl value of an aqueous composition, the specific implementation of which is the same as in Example 1, except that the pH is 8.0.

[0074] Comparative Example 11

[0075] A method for testing the hydroxyl value of an aqueous composition, the specific implementation of which is the same as in Example 1, except that the reaction temperature of the constant temperature water bath reaction is 30°C.

[0076] Comparative Example 12

[0077] A method for testing the hydroxyl value of an aqueous composition, the specific implementation of which is the same as in Example 1, except that the reaction temperature of the constant temperature water bath reaction is 50°C.

[0078] Comparative Example 13

[0079] A method for testing the hydroxyl value of an aqueous composition, the specific implementation of which is the same as in Example 1, except that the reaction temperature of the constant temperature water bath reaction is 60°C.

[0080] Comparative Example 14

[0081] A method for testing the hydroxyl value of an aqueous composition, the specific implementation of which is the same as in Example 1, except that the reaction temperature of the constant temperature water bath reaction is 70°C.

[0082] Comparative Example 15

[0083] A method for testing the hydroxyl value of an aqueous composition, the specific implementation of which is the same as in Example 1, except that the reaction temperature of the constant temperature water bath reaction is 80°C.

[0084] Table 1

[0085]

[0086] The results show that the method in Example 1 of this application has good precision and meets the analytical requirements. The data from Example 1 are basically stable, have good repeatability, and are close to the nominal hydroxyl values ​​of the reagents.

[0087] The hydroxyl value test results of Example 1 and Comparative Examples 1-15 are shown in Table 2. The tested aqueous compositions used OP-7 emulsifier, purchased from Maclean's.

[0088] Table 2

[0089]

[0090] When the reaction temperature of the constant temperature water bath is controlled at 40℃, the reaction time is 15min, and the pH is 7.0, the reaction basically reaches equilibrium, and the measured results are closest to the true values. When the temperature is too low or the reaction time is too short, the reaction will be incomplete. When the temperature is too high or the reaction time is too long, the complex may decompose.

[0091] The hydroxyl values ​​of polyethylene glycol, OP-7 emulsifier, and polyether-based waterborne coatings were tested using the standard method of GB / T 12008.3-2009. The hydroxyl value of the polyether-based waterborne coatings was tested using the method in Example 1. The test results are shown in Table 3.

[0092] Table 3

[0093]

[0094] The polyether-based waterborne coating agent is from Zhejiang Zhongke Lide New Materials Co., Ltd., specifically NS-3 waterborne coating agent.

[0095] Compared with the test method of GB / T 12008.3-2009, the results of Example 1 of this application are similar and the error is small.

Claims

1. A method for testing the hydroxyl value of an aqueous composition, characterized in that, Includes the following steps: The aqueous composition is mixed with a solvent mixture and stirred until completely dissolved to obtain an aqueous composition solution; Boric acid is added to the aqueous composition solution. Boric acid coordinates with the hydroxyl groups of the aqueous composition to form a strong complex acid. The pH is controlled, and the reaction is carried out in a constant temperature water bath to avoid boiling. A mixture is obtained, cooled, and then tested to complete the hydroxyl value test. The method for testing after cooling is as follows: add phenolphthalein indicator to the mixture, titrate with sodium hydroxide standard solution, a light pink endpoint appears, and record the volume V2 consumed; Add phenolphthalein indicator to boric acid in an aqueous solution of the composition, titrate with sodium hydroxide standard solution, and a light pink endpoint is obtained. Record the volume V1 consumed. Calculate the hydroxyl value using the formula; The formula is: OHV (mg KOH / g) = V1: Volume of NaOH consumed in titration when the composition solution is non-aqueous (mL); V2: Volume of NaOH consumed in titration when the composition solution is aqueous (mL); M NaOH : Molar concentration of sodium hydroxide standard solution (mol / L); W: Mass of aqueous composition (g).

2. The method for testing the hydroxyl value of the aqueous composition according to claim 1, characterized in that, The reaction time of the constant temperature water bath reaction is 10-20 min.

3. The method for testing the hydroxyl value of the aqueous composition according to claim 1, characterized in that, The reaction temperature of the constant temperature water bath reaction is 30-50℃.

4. The method for testing the hydroxyl value of the aqueous composition according to claim 1, characterized in that, The pH is 6.5-7.

5.

5. The method for testing the hydroxyl value of the aqueous composition according to claim 1, characterized in that, The boric acid is a mixture of boric acid and tertiary water, and the molar concentration of the mixture is 0.7-1.0 M.

6. The method for testing the hydroxyl value of the aqueous composition according to claim 1, characterized in that, The molar concentration of the sodium hydroxide standard solution is 0.3-0.8M.

7. The method for testing the hydroxyl value of the aqueous composition according to claim 1, characterized in that, The solvent mixture is a mixture of ethanol and water, and the volume ratio of ethanol to water is 1:(1-3).

8. The application of a method for testing the hydroxyl value of an aqueous composition according to any one of claims 1-7, characterized in that, It is used for hydroxyl value testing of polyether compounds or polyol compounds.

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