Method for determining composition of amide salt thickening agent

Abstract

The invention relates to the field of chemical analysis, and discloses a method for determining composition of an amide salt thickening agent. The method comprises the following steps: respectively carrying out TG-DSC and nuclear magnetic resonance hydrogen spectrum measurement on the amide salt thickening agent to respectively obtain a TG-DSC thermal analysis curve and a nuclear magnetic resonance hydrogen spectrum; according to the method, TG-DSC quantitative analysis is adopted, the content of dimethyl terephthalate and octadecylamine in the raw materials of the amide salt thickening agent can be accurately detected through a specific calculation formula, a nuclear magnetic resonance quantitative analysis method is combined, calculation is carried out through the area and molar mass of absorption peaks of all components, and the content of the raw materials of dimethyl terephthalate and octadecylamine in the amide salt thickening agent is calculated. According to the method, the content of metal salts of monoamide, bisamide and N-alkyl terephthalic acid monoamide sodium in the amide salt thickening agent can be accurately detected, and the production process of the amide salt thickening agent can be accurately monitored and guided, so that the method is applied to lubricating grease, and the quality of the lubricating grease is accurately controlled.

Description

Technical Field

[0001] This invention relates to the field of chemical analysis, and specifically to a method for determining the composition of amide salt thickeners. Background Technology

[0002] Amide salt thickeners refer to N-alkyl terephthalic acid monoamide salts prepared from fatty amines, dimethyl terephthalate, and alkali metals. Greases prepared with amide salt thickeners possess excellent high-temperature stability, oxidation stability, mechanical stability, and radiation resistance, and are used for lubrication in specific applications and equipment in aviation, aerospace, nuclear power plants, and other high-temperature environments. In the synthesis of amide salt thickeners, the reaction system mainly consists of: incompletely reacted raw materials, monoamides, diamides, N-alkyl terephthalic acid monoamide salts, and other byproducts. The content of each component in the amide salt thickener has a significant impact on the performance of the grease. To ensure the stability of the grease product, it is necessary to accurately quantify the content of each component in the synthesis of the amide thickener, which also provides a reference for optimizing the ratio of synthesis reactants and controlling the process.

[0003] Currently, the main quantitative analysis methods for similar amide compounds include gas chromatography, high-performance liquid chromatography, and gas chromatography-mass spectrometry. However, due to the significant differences in polarity and solubility of the components involved in the synthesis of amide salt thickeners, as well as their high boiling points (some components have boiling points above 320℃), the above methods cannot accurately quantify each component, thus failing to monitor and guide the production process of amide thickeners.

[0004] Therefore, there is an urgent need to provide a new method for determining the composition of amide salt thickeners. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem that the quantitative analysis of amide salt thickeners in the prior art cannot accurately test the content of each component in the amide salt thickener, and to provide a method for determining the composition of amide salt thickeners.

[0006] To achieve the above objectives, a first aspect of the present invention provides a method for determining the composition of an amide salt thickener, wherein the method includes:

[0007] (1) The amide salt thickener was subjected to TG-DSC and nuclear magnetic resonance hydrogen spectrum measurements, respectively, and the TG-DSC thermal analysis curve and nuclear magnetic resonance hydrogen spectrum were obtained.

[0008] (2) Based on the TG-DSC thermal analysis curve, the complete decomposition temperature of dimethyl terephthalate and octadecylamine in the amide salt thickener and the weight loss percentage corresponding to the complete decomposition temperature of dimethyl terephthalate and octadecylamine in the amide salt thickener were obtained.

[0009] (3) Calculate the mass percentage of dimethyl terephthalate and octadecylamine in the amide salt thickener based on the weight loss percentage corresponding to the complete decomposition temperature of dimethyl terephthalate and octadecylamine in the amide salt thickener;

[0010] (4) Based on the characteristic peak area in the proton NMR spectrum, the molar mass of monoamide and diamide in the amide salt thickener, and the mass percentage of dimethyl terephthalate and octadecylamine, calculate the mass percentage of the metal salts of monoamide, diamide and sodium N-alkyl terephthalate monoamide in the amide salt thickener.

[0011] Through the above technical solution, the present invention achieves the following beneficial effects:

[0012] This invention employs TG-DSC quantitative analysis and, through a specific calculation formula, can accurately detect the content of dimethyl terephthalate and octadecylamine, the raw materials in amide salt thickeners. Combined with nuclear magnetic resonance quantitative analysis, it utilizes the area and molar mass of the absorption peaks of each component for calculation, enabling precise detection of the content of monoamide, diamide, and N-alkyl terephthalate monoamide sodium metal salts in amide salt thickeners. This allows for precise monitoring and guidance of the amide salt thickener production process, thereby enabling its application in lubricating greases and precise control of lubricating lipid content. Attached Figure Description

[0013] Figure 1 These are the TG-DSC thermal analysis curves of the amide salt thickener, dimethyl terephthalate, and octadecylamine in Example 1;

[0014] Figure 2 This is the proton NMR spectrum of the main component of the amide salt thickener in Example 1;

[0015] Figure 3 This is the 1H NMR spectrum of the amide salt thickener in Example 1. Detailed Implementation

[0016] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0017] The first aspect of this invention provides a method for determining the composition of an amide salt thickener, wherein the method includes:

[0018] (1) The amide salt thickener was subjected to TG-DSC and nuclear magnetic resonance hydrogen spectrum measurements, respectively, and the TG-DSC thermal analysis curve and nuclear magnetic resonance hydrogen spectrum were obtained.

[0019] (2) Based on the TG-DSC thermal analysis curve, the complete decomposition temperature of dimethyl terephthalate and octadecylamine in the amide salt thickener and the weight loss percentage corresponding to the complete decomposition temperature of dimethyl terephthalate and octadecylamine in the amide salt thickener were obtained.

[0020] (3) Calculate the mass percentage of dimethyl terephthalate and octadecylamine in the amide salt thickener based on the weight loss percentage corresponding to the complete decomposition temperature of dimethyl terephthalate and octadecylamine in the amide salt thickener;

[0021] (4) Based on the characteristic peak area in the proton NMR spectrum, the molar mass of monoamide and diamide in the amide salt thickener, and the mass percentage of dimethyl terephthalate and octadecylamine, calculate the mass percentage of the metal salts of monoamide, diamide and sodium N-alkyl terephthalate monoamide in the amide salt thickener.

[0022] In this invention, the main component of the amide salt thickener is a metal salt containing sodium monoamide of N-alkyl terephthalate. However, during the production process of the amide salt thickener, a small amount of unreacted raw materials (octadecylamine and dimethyl terephthalate) and byproducts (monamides and diamides) are mixed in the target product. Through quantitative analysis by TG-DSC and specific calculation formulas, the content of raw materials dimethyl terephthalate and octadecylamine in the amide salt thickener can be accurately detected, and the production process of the amide salt thickener can be accurately monitored and guided.

[0023] In this invention, the characteristic peaks of the unreacted raw materials (octadecylamine and dimethyl terephthalate) in the amide salt thickener overlap with the chemical shifts of other components (monoamide, diamide, and metal salt of N-alkyl terephthalate monoamide sodium) in the 1H NMR spectrum, which is not conducive to accurately calculating the content of each component in the amide salt thickener. Therefore, TG-DSC quantitative analysis is used to detect the content of the raw materials dimethyl terephthalate and octadecylamine in the amide salt thickener, and combined with NMR quantitative analysis to detect the content of monoamide, diamide, and metal salt of N-alkyl terephthalate monoamide sodium in the amide salt thickener, the production process of the amide salt thickener can be accurately monitored and guided, thereby realizing its application in lubricating grease and precise control of the amount of lubricating grease.

[0024] In this invention, the metal salt of the N-alkyl terephthalic acid monoamide sodium is sodium octadecyl, and the preparation method of the sodium octadecyl includes: mixing octadecylamine with dimethyl terephthalate, keeping the mixture at a constant temperature of 170-200℃ for 7-9 hours, then saponifying it with a sodium hydroxide solution with a mass percentage concentration of 5-9% for 3-5 hours at 90-110℃, and finally centrifuging and washing with water.

[0025] In this invention, based on the TG-DSC thermal analysis curve, the complete decomposition temperature of dimethyl terephthalate and octadecylamine in amide salt thickeners and the corresponding DSC curve will have corresponding endothermic peak signals. Thus, it is possible to accurately determine that the thickener contains unreacted dimethyl terephthalate and octadecylamine. Then, combined with the TG curve, the weight loss percentage corresponding to the complete decomposition temperature of dimethyl terephthalate and octadecylamine in amide salt thickeners can be obtained.

[0026] According to the present invention, the mass percentage of dimethyl terephthalate and octadecylamine in the amide salt thickener is calculated according to the following formula:

[0027] Ma+b=(100%-Tb)×M Thickening agent formula (1),

[0028]

[0029] Mb = Ma + b - Ma (3)

[0030]

[0031]

[0032] Among them, T a T b These represent the percentage weight loss of dimethyl terephthalate at 220℃ and the percentage weight loss of octadecylamine at 265.5℃, respectively, as shown in the TG-DSC thermal analysis curves; M a+b M represents the total mass of dimethyl terephthalate and octadecylamine; a M represents the mass of dimethyl terephthalate; b The mass of octadecylamine; M 稠化剂 For the mass of the thickener; W a W b These represent the percentage content of dimethyl terephthalate and octadecylamine, respectively.

[0033] According to the present invention, the conditions for the TG-DSC include: the protective gas is selected from at least one of nitrogen, argon and helium; the flow rate of the protective gas is 50-90 mL / min; the heating rate is 5-15 °C / min; and the measurement temperature is increased from room temperature to 700 °C.

[0034] According to the present invention, the room temperature is 25-35°C.

[0035] According to the present invention, the mass of the amide salt thickener is 12-14 mg.

[0036] According to the present invention, the method for testing the proton nuclear magnetic resonance spectrum includes: performing a proton nuclear magnetic resonance spectrum test on a mixture of an amide salt thickener and an organic solvent.

[0037] According to the present invention, the mass percentage content of the metal salts of monoamide, diamide, and sodium N-alkyl terephthalate monoamide in the amide salt thickener satisfies the following formula:

[0038]

[0039]

[0040]

[0041] Wherein, I and M are the integral areas and molar masses of the characteristic peaks of the metal salts of monoamide, diamide, and sodium N-alkyl terephthalate monoamide in amide salt thickeners, respectively; W c W d W e The percentage content of metal salts of monoamide, diamide, and sodium N-alkyl terephthalate monoamide, respectively; W a W b These represent the percentage content of dimethyl terephthalate and octadecylamine, respectively.

[0042] According to the present invention, the volume-to-mass ratio of the organic solvent to the amide salt thickener is (0.05-0.13):1, with units of mL / mg.

[0043] According to the present invention, the organic solvent is deuterated trifluoroacetic acid, and the purity of the deuterated trifluoroacetic acid is ≥99.5 wt%.

[0044] According to the present invention, the mixing temperature is 20-60°C.

[0045] According to the present invention, the ultrasonic conditions include: ultrasonic power of 10-20W, ultrasonic frequency of 20-40kHz, ultrasonic time of 3-7min, and temperature of 40-60℃.

[0046] According to the present invention, the detection conditions for the proton nuclear magnetic resonance spectrum include: pulse sequence with 30-degree excitation angle, delay time ≥6s, blank scan count ≥4, and scan count ≥32.

[0047] According to the present invention, the standard samples monoamide, diamide, and sodium octadecyl were first subjected to 1H NMR spectroscopy to obtain... 1The 1H NMR spectrum was then subjected to baseline correction, phase correction, and chemical shift correction to obtain a standard NMR spectrum. 1 1H NMR spectrum, followed by 1H NMR spectrum analysis of the thickener, according to standard... 1 The chemical shifts of the characteristic peaks corresponding to monoamide, diamide, and sodium octadecyl were obtained from the 1H NMR spectra, and the corresponding characteristic peak areas were obtained by integrating the peak areas based on the chemical shifts.

[0048] The present invention will be described in detail below through embodiments.

[0049] Deuterated trifluoroacetic acid was purchased from Chongqing Southwest Chemical Reagent Co., Ltd., with a purity of 99.5 wt%.

[0050] The mass percentages of dimethyl terephthalate and octadecylamine were determined using a NETZSCH STA 449 TG-DSC thermal analyzer manufactured by NETZSCH GmbH, Germany.

[0051] The mass percentage of the metal salts of monoamide, diamide and sodium N-alkyl terephthalate was determined using an AVANCE 400 nuclear magnetic resonance spectrometer manufactured by BRUKER GmbH, Germany.

[0052] The chemical shifts of the characteristic peaks of the metal salts of monoamide, diamide, and sodium N-alkyl terephthalate monoamide in the proton NMR spectrum were 8.253-8.301 ppm, 7.981-8.022 ppm, and 8.31-8.356 ppm, respectively.

[0053] Unless otherwise specified, all reagents used in the following examples and comparative examples are commercially available.

[0054] Preparation Example

[0055] Octadecylamine and dimethyl terephthalate were mixed at a molar ratio of 1:1 and kept at 185°C for 8 hours. Then, the mixture was saponified at 100°C with a 7% sodium hydroxide solution for 4 hours. Finally, the mixture was centrifuged and washed with water to prepare sodium octadecyl thickener.

[0056] Example 1

[0057] (1) Weigh 12 mg of sodium stearyl thickener (preparation example) into a platinum-rhodium crucible and place it in a TG-DSC thermal analyzer. Under nitrogen protection gas at a rate of 50 mL / min, the temperature is increased from 35 °C to 700 °C at a rate of 5 °C / min to obtain the TG-DSC thermal analysis curve.

[0058] (2) Based on the TG-DSC thermal analysis curve, the complete decomposition temperature of dimethyl terephthalate and octadecylamine in the amide salt thickener and the weight loss percentage corresponding to the complete decomposition temperature of dimethyl terephthalate and octadecylamine in the amide salt thickener were obtained.

[0059] (3) Based on the percentage of weight loss corresponding to the complete decomposition temperature of dimethyl terephthalate and octadecylamine in the amide salt thickener, calculate the mass percentage of dimethyl terephthalate and octadecylamine in the amide salt thickener. The specific data are shown in Table 1.

[0060] (4) Add 5 mg of sodium stearyl thickener (preparation example) to a 5 mm NMR tube, add 0.65 mL of deuterated trifluoroacetic acid reagent, mix at 20 °C, and sonicate at 15 W power, 30 kHz frequency and 50 °C for 3 min to completely dissolve it. Seal and mark for testing.

[0061] (5) The detection conditions for the proton NMR spectrum were set as follows: pulse sequence excitation at a 30-degree angle, delay time = 6s, blank scan count = 4 times, and total scan count = 32 times. 1 H NMR spectrum;

[0062] (6) First, the standard samples monoamide, diamide, and sodium octadecyl were subjected to 1H NMR spectroscopy to obtain... 1 The 1H NMR spectrum was then subjected to baseline correction, phase correction, and chemical shift correction to obtain a standard NMR spectrum. 1 1H NMR spectrum, followed by 1H NMR spectrum analysis of the thickener, according to standard... 1 The chemical shifts of the characteristic peaks corresponding to monoamide, diamide and sodium octadecyl were obtained from the H NMR spectrum. The peak area was obtained by integrating the peak area according to the chemical shift. The mass percentage of monoamide, diamide and sodium octadecyl in the amide salt thickener was calculated according to the above formulas (6)-(8). The specific data are shown in Table 1.

[0063] Figure 1 The figures show the TG-DSC thermal analysis curves of the amide salt thickener, dimethyl terephthalate, and octadecylamine in Example 1. As can be seen from the figure, the thickener contains unreacted raw materials octadecylamine and dimethyl terephthalate. The complete decomposition temperatures of octadecylamine and dimethyl terephthalate were determined to be 265.5℃ and 220℃, respectively, based on the TG-DSC curves of the raw materials.

[0064] Figure 3 The figure shows the 1H NMR spectrum of the amide salt thickener in Example 1. As can be seen from the figure, the chemical shifts of the characteristic peaks of monoamide, diamide and octadecylamine in the 1H NMR spectrum are 8.253-8.301ppm, 7.981-8.022ppm and 8.31-8.356ppm, respectively.

[0065] Example 2

[0066] (1) Weigh 14 mg of sodium stearyl thickener (preparation example) into a platinum-rhodium crucible and place it in a TG-DSC thermal analysis instrument. Under nitrogen protection gas of 90 mL / min, the temperature is increased from 25 to 700℃ at a heating rate of 15℃ / min to obtain the TG-DSC thermal analysis curve.

[0067] (2) Based on the TG-DSC thermal analysis curve, the complete decomposition temperature of dimethyl terephthalate and octadecylamine in the amide salt thickener and the weight loss percentage corresponding to the complete decomposition temperature of dimethyl terephthalate and octadecylamine in the amide salt thickener were obtained.

[0068] (3) Based on the percentage of weight loss corresponding to the complete decomposition temperature of dimethyl terephthalate and octadecylamine in the amide salt thickener, calculate the mass percentage of dimethyl terephthalate and octadecylamine in the amide salt thickener. The specific data are shown in Table 1.

[0069] (4) Add 5 mg of sodium stearyl thickener (preparation example) to a 5 mm NMR tube, add 0.25 mL of deuterated trifluoroacetic acid reagent (purity 99.5%), mix at 60 °C, and then sonicate at 20 W power, 20 kHz frequency and 60 °C for 5 min to completely dissolve it. Seal and mark for testing.

[0070] (5) The detection conditions for the proton NMR spectrum were set as follows: pulse sequence excitation at a 30-degree angle, delay time = 6s, blank scan count = 4 times, and total scan count = 32 times. 1 H NMR spectrum;

[0071] (6) First, the standard samples monoamide, diamide, and sodium octadecyl were subjected to 1H NMR spectroscopy to obtain... 1 The 1H NMR spectrum was then subjected to baseline correction, phase correction, and chemical shift correction to obtain a standard NMR spectrum. 1 1H NMR spectrum, followed by 1H NMR spectrum analysis of the thickener, according to standard... 1 The chemical shifts of the characteristic peaks corresponding to monoamide, diamide and sodium octadecyl were obtained from the H NMR spectrum. The peak area was obtained by integrating the peak area according to the chemical shift. The mass percentage of monoamide, diamide and sodium octadecyl in the amide salt thickener was calculated according to the above formulas (6)-(8). The specific data are shown in Table 1.

[0072] Example 3

[0073] (1) Weigh 13 mg of sodium stearyl thickener (preparation example) into a platinum-rhodium crucible and place it in a TG-DSC thermal analysis instrument. Under nitrogen protection gas at 70 mL / min, the temperature is increased from 30 °C to 700 °C at a heating rate of 10 °C / min to obtain the TG-DSC thermal analysis curve.

[0074] (2) Based on the TG-DSC thermal analysis curve, the complete decomposition temperature of dimethyl terephthalate and octadecylamine in the amide salt thickener and the weight loss percentage corresponding to the complete decomposition temperature of dimethyl terephthalate and octadecylamine in the amide salt thickener were obtained.

[0075] (3) Based on the percentage of weight loss corresponding to the complete decomposition temperature of dimethyl terephthalate and octadecylamine in the amide salt thickener, calculate the mass percentage of dimethyl terephthalate and octadecylamine in the amide salt thickener. The specific data are shown in Table 1.

[0076] (4) Add 5 mg of sodium stearyl thickener (preparation example) to a 5 mm NMR tube, add 0.5 mL of deuterated trifluoroacetic acid reagent (purity 99.5%), mix at 40 °C, and sonicate at 10 W power, 40 kHz frequency and 40 °C for 7 min to completely dissolve it, then seal and mark for testing.

[0077] (5) The detection conditions for the proton NMR spectrum were set as follows: pulse sequence excitation at a 30-degree angle, delay time = 6s, blank scan count = 4 times, and total scan count = 32 times. 1 H NMR spectrum;

[0078] (6) First, the standard samples monoamide, diamide, and sodium octadecyl were subjected to 1H NMR spectroscopy to obtain... 1 The 1H NMR spectrum was then subjected to baseline correction, phase correction, and chemical shift correction to obtain a standard NMR spectrum. 1 1H NMR spectrum, followed by 1H NMR spectrum analysis of the thickener, according to standard... 1 The chemical shifts of the characteristic peaks corresponding to monoamide, diamide and sodium octadecyl were obtained from the HNMR spectrum. The corresponding characteristic peak areas were obtained by integrating the peak areas according to the chemical shifts. The mass percentage content of monoamide, diamide and sodium octadecyl in the amide salt thickener was calculated according to the above formulas (6)-(8). The specific data are shown in Table 1.

[0079] Comparative Example 1

[0080] (1) Add 5 mg of sodium stearyl thickener (preparation example) to a 5 mm NMR tube, add 0.25 mL of deuterated trifluoroacetic acid reagent (purity 99.5%), mix at 20 °C, and sonicate at 15 W power, 30 kHz frequency and 50 °C for 3 min to completely dissolve it, then seal and mark for testing.

[0081] (2) The detection conditions for the proton NMR spectrum were set as follows: pulse sequence excitation at a 30-degree angle, delay time = 6s, blank scan count = 4 times, and total scan count = 32 times. 1 H NMR spectrum;

[0082] (3) The obtained 1 Baseline correction, phase correction, and chemical shift correction were performed on the H NMR spectrum to determine the chemical shifts of the corresponding characteristic peaks of monoamide, diamide, and sodium octadecyl. The corresponding characteristic peak areas were obtained by integrating the peak areas based on the chemical shifts. The mass percentage content of monoamide, diamide, and sodium octadecyl in the amide salt thickener was calculated according to the above formulas (6)-(8). The specific data are shown in Table 1.

[0083] Test Example 1

[0084] Accuracy test:

[0085] The method of Example 1 was repeated three times, and the results are shown in Table 2.

[0086] Table 1

[0087]

[0088] Table 1 (continued)

[0089]

[0090] Table 2

[0091]

[0092] This invention establishes a quantitative analysis method for amide salt thickener components. This method utilizes a combination of nuclear magnetic resonance relative quantitative analysis and thermogravimetric analysis (TG-DSC) to accurately quantify monoamides, diamides, N-alkyl terephthalic acid monoamides, and unreacted raw materials generated during the production process of amide salt thickeners. This analytical method is characterized by its simple operation, small sample volume, good stability, and high accuracy. In the accuracy evaluation, the relative standard deviation of each component content was less than 0.9%, demonstrating very good accuracy.

[0093] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for determining the composition of an amide salt thickener, characterized in that, The method includes: (1) The amide salt thickener was subjected to TG-DSC and nuclear magnetic resonance hydrogen spectrum measurements, respectively, and the TG-DSC thermal analysis curve and nuclear magnetic resonance hydrogen spectrum were obtained. (2) Based on the TG-DSC thermal analysis curve, the complete decomposition temperature of dimethyl terephthalate and octadecylamine in the amide salt thickener and the weight loss percentage corresponding to the complete decomposition temperature of dimethyl terephthalate and octadecylamine in the amide salt thickener were obtained. (3) Calculate the mass percentage of unreacted raw materials in the amide salt thickener based on the weight loss percentage corresponding to the complete decomposition temperature of dimethyl terephthalate and octadecylamine in the amide salt thickener. (4) Based on the characteristic peak area in the proton NMR spectrum, the molar mass of monoamide and diamide in the amide salt thickener, and the mass percentage of dimethyl terephthalate and octadecylamine, calculate the mass percentage of the metal salts of monoamide, diamide and sodium N-alkyl terephthalate in the amide salt thickener.

2. The determination method according to claim 1, wherein, The mass percentage of dimethyl terephthalate and octadecylamine in the amide salt thickener is calculated according to the following formula: Ma+b=(100%-Tb)×M Thickening agent formula (1), Mb = Ma + b - Ma (3) Among them, T a T b These represent the percentage weight loss of dimethyl terephthalate at 220℃ and the percentage weight loss of octadecylamine at 265.5℃, respectively, as shown in the TG-DSC thermal analysis curves; M a+b M represents the total mass of dimethyl terephthalate and octadecylamine; a M represents the mass of dimethyl terephthalate; b The mass of octadecylamine; M 稠化剂 For the mass of the thickener; W a W b These represent the percentage content of dimethyl terephthalate and octadecylamine, respectively.

3. The determination method according to claim 1 or 2, wherein, The conditions for the TG-DSC include: the protective gas is selected from at least one of nitrogen, argon and helium; the flow rate of the protective gas is 50-90 mL / min; the heating rate is 5-15 °C / min; and the measurement temperature is increased from room temperature to 700 °C.

4. The determination method according to any one of claims 1-3, wherein, The method for testing the proton nuclear magnetic resonance spectrum includes: performing a proton nuclear magnetic resonance spectrum test on a mixture of an amide salt thickener and an organic solvent.

5. The method according to any one of claims 1-4, wherein, The mass percentage of the metal salts of monoamide, diamide, and sodium N-alkyl terephthalate monoamide in the amide salt thickener satisfies the following formula: Wherein, I and M are the integral areas and molar masses of the characteristic peaks of the metal salts of monoamide, diamide, and sodium N-alkyl terephthalate monoamide in amide salt thickeners, respectively; W c W d W e The percentage content of metal salts of monoamide, diamide, and sodium N-alkyl terephthalate monoamide, respectively; W a W b These represent the percentage content of dimethyl terephthalate and octadecylamine, respectively.

6. The method according to any one of claims 1-5, wherein, The volume-to-mass ratio of the organic solvent to the amide salt thickener is (0.05-0.13):1, with units of mL / mg.

7. The method according to any one of claims 1-6, wherein, The organic solvent is deuterated trifluoroacetic acid.

8. The method according to any one of claims 1-7, wherein, The mixing temperature is 20-60℃.

9. The method according to any one of claims 1-8, wherein, The conditions for the ultrasound include: ultrasound power of 10-20W, ultrasound frequency of 20-40kHz, ultrasound duration of 3-7min, and temperature of 40-60℃.

10. The method according to any one of claims 1-9, wherein, The detection conditions for the proton nuclear magnetic resonance spectrum include: pulse sequence with 30-degree excitation angle, delay time ≥6s, blank scan count ≥4, and scan count ≥32.

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