Ionic liquid used as a water-based lubricating additive and preparation method thereof

Abstract

The present invention provides an ionic liquid used as a water-based lubricating additive and a preparation method thereof. The water-based lubricating additive is an organic salt, and its general formula can be expressed as A + B ‑ , where A + represents an organic cation, B ‑ Represents an organic anion. Compared with traditional ionic liquids, the water-based lubricating additive of the present invention has a simple and easy preparation process, does not require complex steps such as ion exchange, separation, and purification, and has a low preparation cost. In addition, the raw materials required for ionic liquid synthesis are widely available. The product has high chemical stability, thermal stability, extreme pressure resistance, and excellent friction reduction and anti-wear properties. It can withstand a load of 400N and has a certain anti-corrosion ability during use, which can significantly improve the overall performance of water-based lubricants.

Description

Technical Field

[0001] The present invention belongs to the technical field of ionic liquid lubricants, and in particular relates to an ionic liquid used as a water-based lubricating additive and a preparation method thereof. Background Art

[0002] In various industrial sectors, including metallurgy, chemicals, building materials, and aerospace, many machines and parts fail due to friction and wear, resulting in a waste of materials, energy, and manpower. Therefore, lubricants have emerged to reduce friction. However, due to the environmental pollution and resource waste caused by the widespread use of oil-based lubricants, water-based lubricants have attracted attention.

[0003] Water-based lubricating additives have a certain solubility in water, good hydrolytic stability, excellent anti-wear and lubricity, and are used in small amounts, have good anti-corrosion properties, and cause little environmental pollution, showing broad prospects for development and application. Ionic liquids (ILs), as molten salts composed entirely of anions and cations at room temperature, have the characteristics of low volatility, non-flammability, good viscosity-temperature properties, and a low melting point, making them a class of lubricants or lubricating additives with excellent friction-reducing and anti-wear properties. However, highly polar ionic liquids in water-based systems have certain corrosion problems on the surfaces of metal workpieces under harsh working conditions. This corrosion is mainly caused by the hydrolysis reaction of ionic liquids in water systems to generate corrosion products that are detrimental to the metal substrate. Therefore, based on the high designability of the molecular structure of ionic liquids, it is of great significance to prepare a series of water-based lubricating additives that not only have low corrosion but also excellent tribological properties.

[0004] Ionic liquids have high polarity and film-forming properties, and can form a corrosion-inhibiting film on the metal surface to inhibit the erosion of corrosive ions. Zheng et al. studied the anti-corrosion and lubrication properties of three environmentally friendly proton ionic liquids (PILs) in a water-ethylene glycol system. The proton ionic liquids initially adsorb on the metal surface, causing the friction reaction to further occur and forming a carbon film during the friction process. Therefore, the excellent lubrication ability of the proton ionic liquid in the water-ethylene glycol system depends on the tightly packed adsorption layer and carbon film (Tribology International, 165, (2022), 107283). Through research, it was found that ionic liquids as water-based lubricant additives can simultaneously have both anti-corrosion and lubrication effects, and their anti-corrosion and lubrication properties are significantly better than traditional ionic liquids. Therefore, it is very necessary to develop a water-based ionic liquid lubricant additive with low corrosiveness. Summary of the Invention

[0005] The present invention aims to provide an ionic liquid compound used as a water-based lubricant additive and a preparation method thereof. The ionic liquid has a simple preparation process and has good corrosion resistance, load-bearing and anti-friction properties, making it an excellent water-based lubricant additive.

[0006] In order to achieve the above technical purpose, the inventors have conducted a lot of experimental research and unremitting exploration, and finally obtained the following technical solution: an ionic liquid compound, which is an organic salt and can be expressed as A + B - , where A + represents an organic cation, and B- represents an organic anion;

[0007] The organic cation is selected from any one of the following:

[0008]

[0009] The organic anion is selected from any one of the following:

[0010]

[0011] In several preferred embodiments of the present invention, when A + for When B-

[0012] In addition, the present invention also provides a method for preparing the above-mentioned ionic liquid compound, which comprises the following steps: mixing compound A providing the organic cation and compound B providing the organic anion, adding a reaction solvent, stirring at room temperature, subjecting the obtained reaction solution to rotary evaporation, and then drying it in a vacuum drying oven at 60-80°C for 12-24 hours to obtain the target product.

[0013] It should be noted that the organic anions are mainly provided by rigid naphthalene rings (such as 1,8-dihydroxynaphthalene-3,6-disulfonic acid, 2,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,8-naphthalenesulfonam, and naphthalenetetracarboxylic acid), while the organic cations are mainly provided by triethanolamine, choline, tetraethylammonium hydroxide, tetraethylphosphonium bromide, tetrabutylammonium hydroxide, tetrabutylphosphonium hydroxide, and methyltributylammonium bromide.

[0014] The preparation principle of this ionic liquid compound is as follows: the molecular structure of compound A, which provides the organic cation, contains hydroxyl groups, which have a certain weak alkalinity, while the compound B, which provides the organic anion, contains easily ionized hydrogen ions, which make it show a certain weak acidity. Therefore, there is a certain interaction between the hydroxyl groups and hydrogen protons in the structures of compounds A and B, thereby synthesizing a proton-type ionic liquid.

[0015] Further preferably, in the method for preparing the ionic liquid compound as described above, the molar ratio of the organic cation in the compound A to the organic anion in the compound B during mixing is 1:(1-1.5).

[0016] Further preferably, in the method for preparing the ionic liquid compound as described above, the reaction solvent is selected from the following: dichloromethane, N,N-dimethylformamide, and distilled water.

[0017] In order to verify the lubricating properties of the above-mentioned ionic liquid compound, the inventors selected pure water as a control sample and added different concentrations for comparative experiments. The experimental results show that the ionic liquid has a very small and stable friction coefficient and excellent anti-friction and anti-wear properties and extreme pressure properties as a water-based lubricating additive. In addition, the corrosion test results show that this series of water-based lubricating additives also has good corrosion resistance. Therefore, the present invention also provides the use of the above-mentioned ionic liquid compound as a water-based lubricating additive for metal friction pairs. Further preferably, the metal friction pair is a steel-steel friction pair. Even more preferably, the concentration of the ionic liquid compound used as a water-based lubricating additive for metal friction pairs is 0.5wt%-4wt%.

[0018] Compared with the prior art, the water-based lubricating additive and the preparation method thereof provided by the present invention have the following advantages and significant improvements:

[0019] (1) Compared with traditional ionic liquids, the preparation process of this water-based lubricating additive is simple and easy to operate. It does not require complex steps such as ion exchange, separation, and purification. The preparation cost is low, and the raw materials required for the synthesis of ionic liquids are widely available.

[0020] (2) The water-based lubricant additive has good water solubility, high chemical stability, thermal stability, extreme pressure and excellent anti-friction and anti-wear properties. It can withstand a load of 400N and has a certain anti-corrosion ability during use, which can significantly improve the comprehensive performance of water-based lubricants. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The carbon and hydrogen nuclear magnetic resonance spectra of the ionic liquid NLSA-TEOA are shown in FIG.

[0022] Figure 2 For the ionic liquid NLSA-P 2222 C-NMR and H-NMR spectra;

[0023] Figure 3 For the ionic liquid NLSA-N 1444 C-NMR and H-NMR spectra;

[0024] Figure 4 The carbon and hydrogen nuclear magnetic resonance spectra of the ionic liquid NLSA-CHOH are shown in FIG.

[0025] Figure 5 For the ionic liquid NLSA-N 2222 C-NMR and H-NMR spectra;

[0026] Figure 6 is a graph showing the change of friction coefficient of different ionic liquids over time;

[0027] Figure 7 Comparison of wear volume of different ionic liquids;

[0028] Figure 8 Comparison of corrosion current density of different ionic liquids;

[0029] Figure 9 It is a source of organic anion and cation compounds. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0031] Example 1: Preparation of ionic liquid

[0032] Preparation of triethanolamine and 1,8-naphthalenesulfonate ionic liquid: 0.74594 g (0.005 mol) of triethanolamine and 1.02615 g (0.005 mol) of 1,8-naphthalenesulfonate were added to a 100 mL round-bottom flask, and an appropriate amount of dichloromethane was added and stirred at room temperature for 24 h. The resulting reaction solution was rotary evaporated and then dried in a vacuum drying oven at 60 ° C for 12 h to obtain an ionic liquid (denoted as NLSA-TEOA). The carbon and hydrogen nuclear magnetic resonance spectra are shown in FIG. Figure 1 Then add it into water at a concentration of 4% and dissolve it evenly.

[0033] Preparation of ionic liquid of tetraethylphosphonium bromide and 1,8-naphthalenesulfonam sodium salt: 1.02615g (0.005mol) 1,8-naphthalenesulfonam and 0.2701g (0.005mol) sodium methoxide were added to a 100mL round-bottom flask, and then an appropriate amount of anhydrous tetrahydrofuran was added and stirred at room temperature for 24h. The resulting reaction solution was subjected to rotary evaporation and then dried in a vacuum drying oven at 60°C for 12h to obtain 1,8-naphthalenesulfonam sodium salt. 1.13615g (0.005mol) tetraethylphosphonium bromide and 1.13615g (0.005mol) of the obtained 1,8-naphthalenesulfonam sodium salt were added to a 100mL round-bottom flask, and then an appropriate amount of distilled water was added and stirred at room temperature for 24h. The resulting reaction solution was subjected to rotary evaporation and then dried in a vacuum drying oven at 60°C for 12h to obtain the ionic liquid (denoted as NLSA-P 2222 ), C-NMR and H-NMR spectra such as Figure 2 Then add it into water at a concentration of 4% and dissolve it evenly.

[0034] Preparation of ionic liquid of methyltributylamine bromide and 1,8-naphthalenesulfonate sodium salt: 1.02615g (0.005mol) 1,8-naphthalenesulfonate and 0.2701g (0.005mol) sodium methoxide were added to a 100mL round-bottom flask, and then an appropriate amount of anhydrous tetrahydrofuran was added and stirred at room temperature for 24h. The resulting reaction solution was subjected to rotary evaporation and then dried in a vacuum drying oven at 60°C for 12h to obtain 1,8-naphthalenesulfonate sodium salt. 1.8686g (0.005mol) methyltributylamine bromide and 1.13615g (0.005mol) of the obtained 1,8-naphthalenesulfonate sodium salt were added to a 100mL round-bottom flask, and then an appropriate amount of distilled water was added and stirred at room temperature for 24h. The resulting reaction solution was subjected to rotary evaporation and then dried in a vacuum drying oven at 60°C for 12h to obtain the ionic liquid (denoted as NLSA-N 1444 ), C-NMR and H-NMR spectra such as Figure 3 Then add it into water at a concentration of 4% and dissolve it evenly.

[0035] Preparation of choline and 1,8-naphthalenesulfonam ionic liquid: 1.3463g (0.005mol) of choline and 1.02615g (0.005mol) of 1,8-naphthalenesulfonam were added to a 100mL round-bottom flask, and then an appropriate amount of dichloromethane was added and stirred at room temperature for 24h. The resulting reaction solution was rotary evaporated and then dried in a vacuum drying oven at 60℃ for 12h to obtain an ionic liquid (denoted as NLSA-CHOH). The carbon and hydrogen nuclear magnetic resonance spectra are as follows: Figure 4 Then add it into water at a concentration of 4% and dissolve it evenly.

[0036] Preparation of tetraethylammonium hydroxide and 1,8-naphthalenesulfonamide ionic liquid: 29452g (0.005mol) of tetraethylammonium hydroxide and 1.02615g (0.005mol) of 1,8-naphthalenesulfonamide were added to a 100mL round-bottom flask, and then an appropriate amount of dichloromethane was added and stirred at room temperature for 24h. The obtained reaction solution was subjected to rotary evaporation and then dried in a vacuum drying oven at 60℃ for 12h to obtain the ionic liquid (denoted as NLSA-N 2222 ), C-NMR and H-NMR spectra such as Figure 5 Then add it into water at a concentration of 4% and dissolve it evenly.

[0037] Example 2: Testing of friction reduction and anti-wear properties

[0038] The lubricating performance of the ionic liquid of the present invention as a water-based lubricating additive was evaluated using the SRV5 micro-vibration friction and wear tester produced by the German Optimol Grease Company. Friction test conditions: load 400N, frequency 25Hz, amplitude 1mm, experimental time 30min, temperature 25°C, the upper test ball is a GCr15 steel ball with a diameter of 10mm, and the lower sample is a 01HB steel block with a diameter of 24mm and a thickness of 7.9mm, and a hardness of 750-850HV. The three ionic liquids prepared in Example 1 were added to pure water at a concentration of 4% and dissolved evenly to evaluate their lubricating performance as water-based lubricating additives (pure water was used as a control). The wear volume of the lower sample was measured by a BRUKER-NPFLEX three-dimensional optical profilometer. The obtained average friction coefficient and wear volume are shown in Table 1. Figure 6 and Figure 7 shown.

[0039] Table 1

[0040]

[0041]

[0042] Combined with Table 1 and Figure 6 、 Figure 7 It can be seen that compared with pure water, the average friction coefficient and wear volume of the ionic liquid prepared by the present invention are significantly reduced, and the friction process is very stable without a sudden increase in the friction coefficient, thus avoiding irreversible wear caused by the high friction coefficient. This shows that the ionic liquid synthesized by the present invention has excellent friction reduction and anti-wear effects.

[0043] Example 3: Corrosion resistance test

[0044] Corrosion test conditions: Tafel tests were performed at 298K ± 2K, with platinum electrode, saturated calomel electrode and Q235 steel as counter electrode, reference electrode and working electrode, respectively (diameter: 3 mm; area: 0.07 cm 2 The electrolyte consisted of a 0.5% ionic liquid water-based lubricant additive. Before the experiment began, the working electrode was immersed in the electrolyte solution for 30 minutes to establish the equilibrium open-circuit potential (OCP). Polarization curves were measured at a voltage of ±250 mV from the OCP and a scan rate of 0.000333 V / s. All tests were repeated at least three times.

[0045] Table 2

[0046]

[0047] Combined with Table 2 and Figure 8 It can be seen that compared with pure water, the ionic liquid synthesized in the present invention has a lower corrosion current density and a larger polarization resistance, and can form a protective film on the metal surface to hinder the erosion of the corrosive medium on the metal surface, thereby showing good corrosion resistance.

Claims

1. An ionic liquid compound, characterized in that The general formula of the ionic liquid compound is A + B - , where A + represents an organic cation, B - represents an organic anion; A + for B - for 2. A method for preparing the ionic liquid compound according to claim 1, characterized in that: The method comprises the following steps: mixing a compound A providing the organic cation and a compound B providing the organic anion, adding a reaction solvent, stirring at room temperature, subjecting the obtained reaction solution to rotary evaporation, and then drying it in a vacuum drying oven at 60-80°C for 12-24 hours to obtain a target product.

3. The method for preparing the ionic liquid compound according to claim 2, wherein: When mixed, the molar ratio of the organic cation in the compound A to the organic anion in the compound B is 1:(1-1.5).

4. The method for preparing the ionic liquid compound according to claim 2, wherein: The reaction solvent is selected from the following: dichloromethane, N,N-dimethylformamide, and distilled water.

5. Use of the ionic liquid compound according to claim 1 as a water-based lubricating additive for metal friction pairs.

6. The use according to claim 5, characterized in that The metal friction pair is a steel-steel friction pair.

7. The use according to claim 5, characterized in that The ionic liquid compound is used as a water-based lubricating additive for metal friction pairs at a concentration of 0.5 wt % to 4 wt %.

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