An indicator and method for quickly detecting excess organic amine and isocyanate in polyurea grease

Abstract

The invention discloses an indicator and method for quickly detecting excessive organic amine and isocyanate in polyurea grease. The indicator is obtained by dissolving ninhydrin and p-nitrodiazonium tetrafluoroborate in anhydrous ethanol. When detecting, petroleum ether and the indicator are added to the polyurea grease to be detected and stirred evenly, and heated at 85-95°C, and the color change of the polyurea grease to be detected is continuously observed; if the organic amine in the polyurea grease to be detected is excessive, red or yellow-red appears after the indicator is added, and the color changes significantly with heating; if the isocyanate in the polyurea grease to be detected is excessive, yellow appears after the indicator is added, and changes to red-yellow. The detection method uses two color developers to quickly detect organic amine and isocyanate groups, and adjusts the organic amine to make the isocyanate react completely, so as to solve the problem of poisoning caused by excessive isocyanate in polyurea grease and the problem of uncontrollable grease performance caused by quenching isocyanate.

Description

Technical Field

[0001] The invention relates to an indicator and a method for quickly detecting excess organic amine and isocyanate in polyurea grease, belonging to the technical field of chemical detection. Background Art

[0002] In the current industrial production field, grease is a key material, and its importance in reducing mechanical wear and extending the service life of equipment is self-evident. Grease is essentially a semi-solid substance with a two-phase structure. Its main components include 60-90% base oil (such as synthetic oil, mineral oil, etc.), 5-10% thickener (such as metal soap, polymer, inorganic clay, etc.) and 0-5% additives (such as anti-wear agents, preservatives, antioxidants, etc.). The thickener fixes the base oil in the three-dimensional network structure it forms through physical cross-linking and chemical adsorption, giving the grease unique rheological properties. On this basis, when the grease is sheared, it can release the base oil to the friction interface to produce a lubricating effect, and recover the base oil after the shearing stops, so its performance is affected by many factors.

[0003] Lithium-based greases are well-known for their excellent comprehensive performance and high market share. However, with the rising price of lithium resources, non-soap greases, especially polyurea greases (PUGs), have become a key alternative product that has attracted much attention due to their excellent performance under harsh conditions such as high temperature, high speed and high load. PUGs do not contain metal ions, have excellent oxidation stability, and ensure a long service life. They are one of the materials with the most development potential in the field of greases. However, the production process of polyurea greases faces certain challenges. The purity of the raw materials and the uncertainty in the mixing process greatly affect the reaction efficiency of isocyanates and organic amines, resulting in incomplete reactions or the generation of side reactions. In Chinese patent CN102899125A, water is finally used to neutralize excess isocyanates to prepare polyurea greases. EP0274756 uses a method of reacting primary amines and primary alcohols with diisocyanates to prepare polyurea greases. Although this problem is alleviated to a certain extent, the reaction products of isocyanates and proton hydrogen solvents introduced by these methods are mixed in the grease as thickeners, resulting in complex ingredients and unknown content. This has significantly restricted the development of high-end polyurea greases that pursue higher quality and performance stability. On the other hand, excessive isocyanates in the production process not only pose a threat to the environment, but may also affect the health of operators. Therefore, in response to these challenges in the production of polyurea greases, developing a new technology or method that can accurately control the reaction of raw materials, reduce by-products and improve product quality is of great significance to the development of the industry and environmental protection.

[0004] In view of the above background, the present invention proposes an innovative detection method, which uses two typical color development reactions to quickly and accurately detect the residual amount of organic amines and isocyanates in polyurea grease. The introduction of this method not only simplifies the detection process, improves reaction efficiency and sensitivity, but also can effectively reduce environmental and health risks in the production process, thereby improving the performance stability and environmental performance of the product. By accurately controlling the integrity of the raw material reaction, the present invention is expected to promote the development of high-end polyurea grease and promote the entire grease industry to develop in a higher quality and more environmentally friendly direction.

[0005] In the preliminary application cases, the detection method of the present invention has been successfully applied to multiple production batches of polyurea grease, effectively identifying and adjusting the amount of raw materials, ensuring the performance stability between product batches, and demonstrating its great potential and practical value in actual production. These actual cases further verify the importance and market application prospects of the method of the present invention, marking an important step for the grease industry in improving product quality and environmental protection. Summary of the invention

[0006] The purpose of the present invention is to provide an indicator and a method for quickly detecting excessive organic amine and isocyanate in polyurea grease.

[0007] An indicator for rapidly detecting excess organic amine and isocyanate in polyurea grease is prepared by dissolving ninhydrin and p-nitrobenzenediazonium tetrafluoroborate in anhydrous ethanol, wherein the concentration of ninhydrin is 1-2 mg / mL and the concentration of p-nitrobenzenediazonium tetrafluoroborate is 0.4-1.5 mg / mL.

[0008] The organic amine is a mixture of one or more of octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, oleylamine, cyclohexylamine, p-toluidine, aniline, ethylenediamine, propylenediamine, and hexamethylenediamine. The isocyanate is a diisocyanate, and the diisocyanate is one or more of toluene diisocyanate, methyl diphenyl diisocyanate, diphenylmethane diisocyanate, m-xylylene diisocyanate, and 4, 4-diphenylmethane diisocyanate.

[0009] The method of the present invention using the indicator to detect excess organic amine and isocyanate in polyurea grease comprises the following steps:

[0010] (1) dissolving ninhydrin and p-nitrobenzenediazonium tetrafluoroborate in anhydrous ethanol to obtain an indicator;

[0011] (2) Add petroleum ether and indicator to the polyurea grease to be tested and stir evenly, heat at 85-95°C, and continuously observe the color change of the polyurea grease to be tested; if there is an excess of organic amine in the polyurea grease to be tested, red or yellowish red will appear after the indicator is added, and the color will change significantly with heating, turning into purple or purple-red; if there is an excess of isocyanate in the polyurea grease to be tested, yellow will appear after the indicator is added, and turn to reddish yellow, and the color will only deepen to varying degrees.

[0012] Beneficial effects of the present invention:

[0013] The invention discloses a method for rapidly detecting excess organic amine and isocyanate in polyurea grease, which solves the problem of uncontrollable raw material reaction and difficult treatment of excess raw materials in conventional polyurea grease. Compared with the conventional method of adding excess isocyanate and then quenching to prevent excess reaction raw materials, the detection method uses two color developers to rapidly detect organic amine and isocyanate groups, and adjusts the organic amine to allow the isocyanate to react completely, so as to solve the problem of poisoning caused by excess isocyanate in polyurea grease and the problem of uncontrollable grease performance caused by quenching isocyanate. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is the infrared spectra of octylamine series grease Sample 1 (excessive organic amine) and Sample 2 (excessive isocyanate);

[0015] FIG2 is an optical picture of the color development of Sample 1 and Sample 2 after the indicator is added;

[0016] FIG3 is an infrared spectra of cyclohexylamine series grease Sample 3 (excessive organic amine) and Sample 4 (excessive isocyanate);

[0017] FIG4 is an optical picture of the color development of Sample 3 and Sample 4 after the addition of the indicator. DETAILED DESCRIPTION

[0018] The indicator and method for quickly detecting excess organic amine and isocyanate in polyurea grease of the present invention are described in detail below in conjunction with specific examples.

[0019] Example 1 Preparation of indicator

[0020] Dissolve 0.653 g of ninhydrin (AR) and 0.020 g of p-nitrobenzenediazonium tetrafluoroborate (AR) in anhydrous ethanol and dilute to 500 mL to obtain the indicator.

[0021] Example 2 Detection of Excess Octylamine and TDI

[0022] (1) Raw material preparation:

[0023] 13.49 g of toluene diisocyanate (TDI, 98%) was dissolved in 86.51 g of PAO8 base oil to prepare a TDI / PAO8 dispersion solution with an effective mass fraction of 13.22%.

[0024] Weigh two portions of 10.44 g TDI / PAO8 dispersion solution in a 100 ml beaker. Theoretically, 2.07 g octylamine (99%) is required for complete reaction. Therefore, the octylamine added to the organic amine excess sample and isocyanate excess sample is 2.34 g and 1.85 g, respectively.

[0025] Preparation of the sample with excessive organic amine: 2.34 g of octylamine was dissolved in 37.45 g of PAO 8 base oil to obtain an organic amine / PAO 8 dispersion, and 10.44 g of TDI / PAO8 dispersion solution was added dropwise to the organic amine / PAO 8 dispersion. The temperature of the reaction raw materials must be controlled within 40°C to prevent urea from being generated by excessive temperature. After mixing, the grease sample was stirred and slowly heated to 160°C. After 30 minutes of constant temperature, the heating was stopped and finally stirred to room temperature to obtain a grease sample with excessive organic amine (Sample 1).

[0026] Preparation of isocyanate excess sample: 1.85 g of octylamine was dissolved in 37.45 g of PAO 8 base oil to obtain an organic amine / PAO 8 dispersion, and 10.44 g of TDI / PAO8 dispersion solution was added dropwise to the organic amine / PAO 8 dispersion. The temperature of the reaction raw materials must be controlled within 40°C to prevent urea from being generated by excessive temperature. After mixing, the grease sample was stirred and slowly heated to 160°C. After the temperature was kept constant for 30 minutes, the heating was stopped and finally stirred to room temperature to obtain a grease isocyanate excess sample (Sample 2).

[0027] (2) Indicator detection:

[0028] Weigh 3 g of each of Sample 1 and Sample 2 into a 25×25 weighing bottle, add 1.5 ml of petroleum ether and stir thoroughly to dissolve; add 1 ml of indicator (the indicator prepared in Example 1) dropwise to each and stir thoroughly to mix evenly, place the weighing bottle on a heating table at 90°C to heat, and observe the color change of the sample.

[0029] Figure 1 is the infrared spectra of octylamine series grease Sample 1 (excess organic amine) and Sample 2 (excess isocyanate). As shown in the figure, Sample 2 has a peak at 2268 cm -1An obvious absorption peak of isocyanate group appeared, while Sample 1 did not, indicating that there was an excess of organic amine in Sample 1 and an excess of isocyanate in Sample 2. Figure 2 is an optical picture of the color change of Sample 1 and Sample 2 over time after the addition of the indicator (the left picture of the color change of Sample 1 over time in (a)-(d) and the right picture of the color change of Sample 2 over time). It can be seen that the sample with excess amine appears yellow-red at the beginning, and purple appears at the bottom after heating, and slowly covers the yellow-red color and turns into purple as heating; the color of the sample with excess isocyanate group changes from yellow to red-yellow.

[0030] Example 3 Detection of cyclohexylamine and isocyanate

[0031] (1) Raw material preparation:

[0032] 13.49 g of toluene diisocyanate (TDI, 98%) was dissolved in 86.51 g of PAO8 base oil to prepare a TDI / PAO8 dispersion solution with an effective mass fraction of 13.22%.

[0033] Weigh two portions of 12.41 g TDI / PAO8 dispersion solution in a 100 ml beaker. Theoretically, 1.89 g cyclohexylamine (99%) is required for complete reaction. Therefore, the cyclohexylamine added to the sample with excess organic amine and the sample with excess isocyanate is 2.12 g and 1.64 g, respectively.

[0034] Preparation of the sample with excessive organic amine: 2.12 g of cyclohexylamine was dissolved in 35.73 g of PAO 8 base oil to prepare an organic amine / PAO 8 dispersion, and 12.41 g of TDI / PAO8 dispersion solution was added dropwise to the organic amine / PAO 8 dispersion solution. The temperature of the reaction raw materials must be controlled within 40°C to prevent urea from being generated by excessive temperature. After mixing, the grease sample was stirred and slowly heated to 160°C. After the temperature was kept constant for 30 minutes, the heating was stopped and finally stirred to room temperature to obtain a grease sample with excessive organic amine (Sample 3).

[0035] Preparation of isocyanate excess sample: 1.64 g cyclohexylamine was dissolved in 35.73 g PAO 8 base oil to obtain an organic amine / PAO 8 dispersion, and 12.41 g TDI / PAO8 dispersion solution was added dropwise to the organic amine / PAO 8 dispersion solution. The temperature of the reaction raw materials must be controlled within 40°C to prevent urea from being generated by excessive temperature. After mixing, the grease sample was stirred and slowly heated to 160°C. After the temperature was kept constant for 30 minutes, the heating was stopped and finally stirred to room temperature to obtain a grease isocyanate excess sample (Sample 4).

[0036] (2) Indicator detection:

[0037] Weigh 3 g of each of Sample 3 and Sample 4 into a 25×25 weighing bottle, add 1.5 ml of petroleum ether and stir thoroughly to dissolve; add 1.0 ml of indicator (the indicator prepared in Example 1) dropwise to each and stir thoroughly to mix evenly, place the weighing bottle on a heating table at 90°C to heat, and observe the color change of the sample.

[0038] Figure 3 is the infrared spectra of cyclohexylamine series grease Sample 3 (excessive organic amine) and Sample 4 (excessive isocyanate). As shown in the figure, Sample 3 has a peak at 2268 cm -1 There is an obvious absorption peak of isocyanate group, while Sample 4 does not, indicating that there is an excess of organic amine in Sample 3 and an excess of isocyanate in Sample 4. Figures 4a-d are optical images of the color change of Sample 3 (left) and Sample 4 (right) over time after the addition of the indicator (the left image of (a)-(d) is the optical image of the color change of Sample 3 over time, and the right image is the optical image of the color change of Sample 4 over time). It can be seen that the sample with excess amine turns into a deep yellow-red color at the beginning, and the color changes significantly with heating, turning into purple-red; the color of the sample with excess isocyanate group changes from yellow to red-yellow, and only the color deepens.

[0039] Example 4 Unknown actual sample detection

[0040] Weigh 3±0.1 g of unknown polyurea grease to be tested into a 25×25 ml weighing bottle, add 1.5 ml of petroleum ether and 1.0 ml of indicator (the indicator prepared in Example 1) and stir evenly, place it on a 90°C heating table to heat, and continuously observe the color change of the sample. It is observed that the sample appears yellow-red at the beginning, and purple appears at the bottom after heating, and slowly covers the yellow-red, indicating that the sample is an organic amine excess sample.

Claims

1. An indicator for rapid detection of excess organic amine and isocyanate in polyurea grease, characterized in that: The indicator is prepared by dissolving ninhydrin and p-nitrobenzenediazonium tetrafluoroborate in anhydrous ethanol, wherein the concentration of ninhydrin is 1-2 mg / mL, the concentration of p-nitrobenzenediazonium tetrafluoroborate is 0.4-1.5 mg / mL, and the isocyanate is diisocyanate.

2. The indicator for rapid detection of excess organic amine and isocyanate in polyurea grease according to claim 1, characterized in that: The organic amine is a mixture of one or more of octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, oleylamine, cyclohexylamine, p-toluidine, aniline, ethylenediamine, propylenediamine and hexamethylenediamine.

3. The indicator for rapid detection of excess organic amine and isocyanate in polyurea grease according to claim 1, characterized in that: The diisocyanate is one or more of toluene diisocyanate, methyl diphenyl diisocyanate, diphenylmethane diisocyanate, meta-xylylene diisocyanate, and 4,4-diphenylmethane diisocyanate.

4. The method for detecting excess organic amine and isocyanate in polyurea grease by using an indicator according to claim 1, comprising the following steps: (1) dissolving ninhydrin and p-nitrobenzenediazonium tetrafluoroborate in anhydrous ethanol to obtain an indicator; (2) Add petroleum ether and an indicator to the polyurea grease to be tested and stir evenly. Heat at 85-95°C and continuously observe the color change of the polyurea grease to be tested. If there is an excess of organic amine in the polyurea grease to be tested, red or yellowish red will appear after the indicator is added, and the color will change significantly with heating, turning into purple or purple-red. If there is an excess of isocyanate in the polyurea grease to be tested, yellow will appear after the indicator is added, and the color will turn into reddish yellow, and the color will only deepen to varying degrees.

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