Method for measuring amine value of amino polyether

Abstract

The invention discloses a method for measuring the amine value of amino polyether, which comprises the following steps: (1) preparing a strong acid-proton donor standard solution by using strong acid as a solute and a proton donor reagent as a solvent, and calibrating the strong acid concentration c of the standard solution with the unit of mol / L by using potassium hydrogen phthalate as a calibration substance; (2) quantitatively weighing an amino polyether sample with the accuracy of 0.0001 g, putting the sample into a titration cup, and adding a solvent for dissolving; titrating with a standard solution on a potentiometric titrator, and reading the volume number V of the consumed standard solution according to a titration end point; and calculating according to a formula X = V * c / m to obtain the amine value content in the amino polyether. The method can effectively avoid the influence of a steric effect and a charge effect on a detection result, accurately detects the amine value content of the amino polyether, and is simple to operate, high in repeatability, low in detection cost and high in sensitivity.

Description

Technical Field

[0001] The invention relates to the technical field of chemical analysis, and in particular to a method for determining an amino polyether amine value. Background Art

[0002] The amine value of amino polyether is one of the key indicators of its performance, which directly affects its curing speed, hardness, chemical resistance, etc. In practical applications, the amine value of amino polyether needs to be adjusted according to specific needs. For example, in situations where fast curing is required, products with higher amine values ​​can be selected; while in applications that require higher flexibility, products with lower amine values ​​should be selected. In addition, different catalysts and reaction conditions will also affect the effectiveness of the amine value, so various factors need to be considered comprehensively when selecting and using amino polyether.

[0003] The amine value content of conventional small molecule substances is usually determined by titration with a standard hydrochloric acid solution. However, amino polyethers contain phenyl groups and polymer structures, which have obvious steric and charge effects, greatly reducing the alkalinity of their amine groups. The accuracy of the existing methods for determining their amine values ​​is greatly reduced, especially when the polyether initiator is an aromatic diamine substance. The result of the amine value detection is even only half of the theoretical value. Therefore, it is urgent to develop a method that can accurately determine the amine value of amino polyethers. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a method for determining the amine value of amino polyether.

[0005] The technical solution adopted by the present invention is: A method for determining the amino polyether amine value comprises the following steps: (1) Use a strong acid as the solute and a proton donating agent as the solvent A to prepare a strong acid-proton donating standard solution. Use potassium hydrogen phthalate as the calibration substance to calibrate the strong acid concentration c of the standard solution in mol / L. (2) Quantitatively weigh an amino polyether sample to an accuracy of 0.0001 g, place it in a titration cup, and add solvent B to dissolve the sample; titrate with a standard solution on a potentiometric titrator, and read the volume V of the consumed standard solution according to the titration endpoint; calculate the amine value content in the amino polyether according to the following formula (1); X=V*c / m Formula (1) Where: X—amine value, mmol / g; V—the volume of the standard solution consumed, mL; c—strong acid concentration of standard solution, mol / L; m—mass of sample, g.

[0006] Furthermore, the initiator of the amino polyether is any one of aniline, m-toluenediamine, o-toluenediamine, p-toluenediamine, methylaniline, dimethylaniline, cyclohexylamine, cyclohexyldiamine, o-aminocyclohexanol, m-aminocyclohexanol, and p-aminocyclohexanol.

[0007] Furthermore, the polymerization monomer of the amino polyether is any one of ethylene oxide, propylene oxide and butylene oxide.

[0008] Furthermore, the number average molecular weight of the amino polyether is 100-2000.

[0009] Furthermore, the strong acid is trifluoromethanesulfonic acid, perchloric acid, sulfuric acid or hydrochloric acid.

[0010] Furthermore, the proton donating agent is formic acid, acetic acid, propionic acid or butyric acid.

[0011] Furthermore, the solvent B used in step (2) is the same as the solvent A in step (1).

[0012] Furthermore, when the polyether initiator is an aromatic diamine substance, the titration endpoint is the second mutation point.

[0013] The beneficial effects of the present invention are as follows: the present invention can effectively avoid the influence of steric effect and charge effect on the detection result, accurately detect the amine value content of amino polyether, and has simple operation, high repeatability, low detection cost and high sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is the titration curve diagram of Example 1. DETAILED DESCRIPTION

[0015] The instruments, samples and reagents used in the present invention are described as follows: Automatic potentiometric titrator: Mettler G20S.

[0016] The reagents used were commercially available analytical grade glacial acetic acid, trifluoromethanesulfonic acid, and standard reagent potassium hydrogen phthalate.

[0017] The amino polyether samples used were homemade products of our company (Nanjing Hongbaoli Polyurethane Co., Ltd.).

[0018] The method for determining the amino polyether amine value disclosed in the present invention comprises the following steps: (1) Use a strong acid as the solute and a proton donating agent as the solvent to prepare a strong acid-proton donating standard solution, and potassium hydrogen phthalate as the calibration substance to calibrate the strong acid concentration c of the standard solution in mol / L; (2) Quantitatively weigh an amino polyether sample to an accuracy of 0.0001 g, place it in a titration cup, and add solvent A to dissolve it; titrate it with a standard solution on a potentiometric titrator, and read the volume V of the consumed standard solution according to the titration endpoint; calculate the amine value content in the amino polyether according to the following formula (1); X=V*c / m Formula (1) Where: X—amine value, mmol / g; V—the volume of the standard solution consumed, mL; c—strong acid concentration of standard solution, mol / L; m—mass of sample, g. Example 1

[0019] A standard solution was prepared using hydrochloric acid as the solute and formic acid as the solvent. The reference reagent potassium hydrogen phthalate dried to a constant amount was used as the calibration substance. The hydrochloric acid concentration of the hydrochloric acid-formic acid standard solution was calibrated to be 0.3534 mol / L.

[0020] (2) Weigh the amino polyether sample (data molecular weight is 267, theoretical amine value is 3.7453 mol / g) generated by reacting aniline as the initiator with propylene oxide in a ratio of 1:3, record the mass as m, place it in a titration cup, add 40 ml formic acid, titrate with hydrochloric acid-formic acid standard solution on a potentiometric titrator, and read the result according to the titration end point. The titration end point is the second mutation point. Record the titration end point volume as V. The amine value content in the amino polyether is calculated according to formula (1), and the amine values ​​of 6 amino polyether samples are measured at the same time and are shown in Table 1.

[0021]

[0022] It can be seen from Table 1 that the detection method of the present invention has high accuracy and strong repeatability. Example 2

[0023] (1) A standard solution was prepared using trifluoromethanesulfonic acid as the solute and acetic acid as the solvent. The standard reagent potassium hydrogen phthalate dried to a constant volume was used as the calibration substance. The trifluoromethanesulfonic acid concentration of the trifluoromethanesulfonic acid-acetic acid standard solution was calibrated to 0.2157 mol / L.

[0024] (2) Weigh the amino polyether sample (data molecular weight is 317, theoretical amine value is 6.3091 mol / g) generated by reacting cyclohexanediamine as the initiator with propylene oxide in a ratio of 1:3.5, record the mass as m, place it in a titration cup, add 40 ml acetic acid, titrate with trifluoromethanesulfonic acid-acetic acid standard solution on a potentiometric titrator, and read the result according to the titration end point. The titration end point is the second mutation point. Record the titration end point volume as V. The amine value content in the amino polyether is calculated according to formula (1), and the amine values ​​of 6 amino polyether samples are measured at the same time and are shown in Table 2.

[0025]

[0026] It can be seen from Table 2 that the detection method of the present invention has high accuracy and strong repeatability. Example 3

[0027] (1) Use sulfuric acid as the solute and formic acid as the solvent to prepare a standard solution. Use potassium hydrogen phthalate, a reference reagent dried to a constant volume, as the calibration substance. The sulfuric acid concentration of the sulfuric acid-formic acid standard solution is calibrated to 0.3290 mol / L.

[0028] (2) Weigh the amino polyether sample (data molecular weight is 380, theoretical amine value is 2.6316 mol / g) generated by using methylaniline as the initiator and butylene oxide in a ratio of 1:3.8, record the mass as m, place it in a titration cup, add 40 ml of formic acid, titrate with sulfuric acid-formic acid standard solution on a potentiometric titrator, and read the result according to the titration end point. Record the volume at the titration end point as V. The amine value content in the amino polyether is calculated according to formula (1), and the amine values ​​of 6 amino polyether samples are measured at the same time and are shown in Table 3.

[0029]

[0030] It can be seen from Table 3 that the detection method of the present invention has high accuracy and strong repeatability. Example 4

[0031] (1) Use perchloric acid as the solute and propionic acid as the solvent to prepare a standard solution. Use potassium hydrogen phthalate, a reference reagent dried to a constant volume, as the calibration substance. The perchloric acid concentration of the perchloric acid-propionic acid standard solution is calibrated to be 0.1542 mol / L.

[0032] (2) Weigh aminocyclohexanol as the initiator and react it with ethylene oxide in a ratio of 1:15 to generate an amino polyether sample (data molecular weight is 775, theoretical amine value is 1.2903 mol / g), record the mass as m, place it in a titration cup, add 40 ml of propionic acid, titrate with perchloric acid-propionic acid standard solution on a potentiometric titrator, and read the result according to the titration end point. The titration end point is the second mutation point. Record the titration end point volume as V. The amine value content in the amino polyether is calculated according to formula (1), and the amine values ​​of 6 amino polyether samples are measured at the same time and are shown in Table 4.

[0033]

[0034] It can be seen from Table 4 that the detection method of the present invention has high accuracy and strong repeatability. Example 5

[0035] (1) A standard solution was prepared using trifluoromethanesulfonic acid as the solute and butyric acid as the solvent. The standard reagent potassium hydrogen phthalate dried to a constant volume was used as the calibration substance. The trifluoromethanesulfonic acid concentration of the trifluoromethanesulfonic acid-butyric acid standard solution was calibrated to 0.3068 mol / L.

[0036] (2) Weigh the amino polyether sample (data molecular weight is 1282, theoretical amine value is 1.5601 mol / g) prepared by reacting p-toluenediamine as the initiator with propylene oxide in a ratio of 1:20, record the mass as m, place it in a titration cup, add 40 ml of butyric acid, titrate with trifluoromethanesulfonic acid-butyric acid standard solution on a potentiometric titrator, read the result according to the titration end point, and record the titration end point volume as V. The amine value content in the amino polyether is calculated according to formula (1), and the amine values ​​of 6 amino polyether samples are measured at the same time, as shown in Table 5.

[0037]

[0038] It can be seen from Table 5 that the detection method of the present invention has high accuracy and strong repeatability.

Claims

1. A method for determining the amine value in amino polyether, characterized in that: The following steps are involved: (1) Use a strong acid as the solute and a proton donating agent as the solvent A to prepare a strong acid-proton donating standard solution. Use potassium hydrogen phthalate as the calibration substance to calibrate the strong acid concentration c of the standard solution in mol / L. (2) Quantitatively weigh an amino polyether sample to an accuracy of 0.0001 g, place it in a titration cup, and add solvent B to dissolve the sample; titrate with a standard solution on a potentiometric titrator, and read the volume V of the consumed standard solution according to the titration endpoint; calculate the amine value content in the amino polyether according to the following formula (1); X=V*c / m Formula (1) Where: X—amine value, mmol / g; V—the volume of the standard solution consumed, mL; c—strong acid concentration of standard solution, mol / L; m—mass of sample, g.

2. A method for determining the amine value content in amino polyether according to claim 1, characterized in that: The initiator of the amino polyether is any one of aniline, m-toluenediamine, o-toluenediamine, p-toluenediamine, methylaniline, dimethylaniline, cyclohexylamine, cyclohexyldiamine, o-aminocyclohexanol, m-aminocyclohexanol and p-aminocyclohexanol.

3. A method for determining the amine value content in amino polyether according to claim 2, characterized in that: The polymerization monomer of the amino polyether is any one of ethylene oxide, propylene oxide and butylene oxide.

4. The method for determining the amine value content in amino polyether according to claim 1, characterized in that: The number average molecular weight of the amino polyether is 100-2000.

5. The method for determining the amine value content in amino polyether according to claim 1, characterized in that: Strong acids are trifluoromethanesulfonic acid, perchloric acid, sulfuric acid or hydrochloric acid.

6. The method for determining the amine value content in amino polyether according to claim 1, characterized in that: The proton donating agent is formic acid, acetic acid, propionic acid or butyric acid.

7. The method for determining the amine value content in amino polyether according to claim 1, characterized in that: The solvent B used in step (2) is the same as the solvent A in step (1).

8. The method for determining the amine value content in amino polyether according to claim 1, characterized in that: When the polyether initiator is an aromatic diamine substance, the titration endpoint is the second mutation point.

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