Amino acid-based protic green ionic liquid, its preparation method and application as water-based lubricating liquid additive

Abstract

The application provides an amino acid base proton type green ionic liquid, a preparation method thereof and application thereof as a water base lubricating liquid additive, and belongs to the technical field of lubricating additives. The ionic liquid provided by the application takes a basic amino acid as an organic cation and takes an alkyl amido acid as an organic anion. The cationic amino acid molecular structure contains a free basic group, and the carboxyl group in the alkyl amido acid molecular structure has certain acidity. The amino acid type proton type ionic liquid can be synthesized through a simple proton exchange reaction, preparation is simple, and there is no complex purification step. The alkyl amido acid organic anion has active nitrogen elements, can be effectively adsorbed to a metal friction pair, forms a firm physical adsorption film, provides good friction reduction and anti-wear performance, and has good extreme pressure performance. In addition, the adsorption film can effectively isolate the metal surface from the lubricating liquid, and greatly improves the corrosion resistance of the metal.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lubricating additives, in particular to an amino acid-based protonic green ionic liquid, a preparation method thereof and application thereof as a water-based lubricant additive. BACKGROUND

[0002] The use of lubricants can effectively reduce friction and control wear. At present, the most widely used in the market is mineral-based lubricants, which account for more than 90% of the world's lubricating market. However, mineral-based lubricants have two obvious disadvantages. On the one hand, petroleum resources are gradually depleted, and on the other hand, the biodegradability of mineral-based lubricants is poor, and the leakage and disposal of waste lubricating oil during use will inevitably cause serious environmental pollution. In order to cope with the dual challenges of depletion of petroleum resources and environmental pollution, it is particularly important to find alternatives to mineral-based lubricants.

[0003] Among the currently developed green tribological solutions, water-based lubrication technology has attracted widespread attention due to its excellent cooling, non-flammability, low pollution, high thermal conductivity, high specific heat capacity, safe operating environment and good cleaning effect. However, compared with the existing traditional oil-based lubrication, the water-based lubrication system still has the problems of insufficient lubricity, poor corrosion resistance and low viscosity, which seriously restricts the development of the water-based lubrication system. SUMMARY

[0004] Therefore, the present application aims to provide an amino acid-based protonic green ionic liquid, a preparation method thereof and application thereof as a water-based lubricant additive. The amino acid-based protonic green ionic liquid provided by the present application has good tribological properties and corrosion resistance when used as a water-based lubricant additive.

[0005] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0006] The present application provides an amino acid-based protonic green ionic liquid, the general structure of which is A + B - , wherein A + represents an organic cation, and B - represents an organic anion.

[0007] The organic cation is a basic amino acid cation, and the anion is an alkyl amido acid anion.

[0008] Preferably, the basic amino acid includes one or both of lysine and arginine.

[0009] Preferably, the alkyl amido acid anion has a structure as shown in formula I:

[0010]

[0011] R1 is hydrogen or methyl in the formula I;

[0012] R is hydrogen, methyl, one or more of them;

[0013] n is any integer from 2 to 11.

[0014] Preferably, the alkyl amido acid comprises one or more of lauroyl glutamic acid anion, lauroyl sarcosine anion, lauroyl glycine anion, lauroyl aspartic acid anion, lauroyl alanine anion, octanoyl glutamic acid anion, octanoyl sarcosine anion, octanoyl glycine anion, octanoyl aspartic acid anion and octanoyl alanine anion.

[0015] The present application provides a preparation method of the amino acid-based protic green ionic liquid as described above, comprising the following steps:

[0016] Mixing the basic amino acid and the alkyl amido acid compound with the aqueous solvent to perform a proton exchange reaction to obtain an amino acid-based protic green ionic liquid aqueous solution; the aqueous solvent is a mixture of water and ethanol;

[0017] Removing the aqueous solvent of the amino acid-based protic green ionic liquid aqueous solution to obtain the amino acid-based protic green ionic liquid.

[0018] Preferably, the basic amino acid and the alkyl amido acid compound are mixed according to an equimolar ratio of active functional groups;

[0019] In the amino acid-based protic green ionic liquid aqueous solution, the mass content of the amino acid-based protic green ionic liquid is 1-50%.

[0020] Preferably, the volume ratio of water and ethanol is 30:70-70:30;

[0021] The temperature of the proton exchange reaction is 30-100℃, and the time is 1-36h.

[0022] The present application provides an application of the amino acid-based protic green ionic liquid as described above as a water-based lubricating liquid additive.

[0023] The present application provides a lubricant comprising a base lubricating liquid and the amino acid-based protic green ionic liquid as described above.

[0024] Preferably, the base lubricating liquid is one of water, water-glycol, water-polyethylene glycol, water-glycerol, water-diethylene glycol, water-triethylene glycol, water-propylene glycol, polyethylene glycol, glycerol, diethylene glycol and triethylene glycol;

[0025] The mass percentage of the amino acid base protic green ionic liquid in the lubricant is 0.1-10%.

[0026] The present application provides an amino acid base protic green ionic liquid, the general structure is A + B - , wherein A + represents an organic cation, B - represents an organic anion. The present application provides an amino acid base protic ionic liquid, which uses basic amino acid as the organic cation and alkyl amido acid as the organic anion. The cationic amino acid molecular structure contains free basic groups, such as amino (lysine) and guanidino (arginine), which have certain basicity, while the carboxyl in the alkyl amido acid molecular structure has certain acidity. The two can be synthesized into an amino acid base protic ionic liquid through a simple proton exchange (acid-base neutralization) reaction, which is simple to prepare and does not require complex purification steps. The alkyl amido acid organic anion has active nitrogen elements, which can be effectively adsorbed onto a metal friction pair to form a firm physical adsorption film, providing good friction reduction and wear resistance, as well as good extreme pressure performance. In addition, the adsorption film can effectively isolate the metal surface from the lubricating liquid, greatly improving the corrosion resistance of the metal. At the same time, the unique inner salt structure of the amino acid and the hydrogen bond interaction between the oxygen and nitrogen atoms and the base lubricating liquid can greatly increase its solubility in the base lubricating liquid.

[0027] The amino acid base protic green ionic liquid provided by the present application has degradable amino acid base structures for the anion and the cation, is safe and non-toxic, has good biocompatibility and biodegradability, is an environmentally friendly ionic liquid, and will not pollute the environment. The ionic liquid does not contain phosphorus elements and sulfur elements, and is a green lubricating additive.

[0028] The present application provides a preparation method of the above-mentioned amino acid base protic green ionic liquid, which can be obtained through only one simple neutralization reaction, and the preparation method is extremely simple, does not require complex steps such as ion exchange, separation, and purification, is easy to scale up, and has good solubility in water. DETAILED DESCRIPTION

[0029] The present application provides an amino acid base protic green ionic liquid, the general structure is A + B - , wherein A + represents an organic cation, B - represents an organic anion.

[0030] The organic cation is a basic amino acid cation, and the anion is an alkyl amido acid anion.

[0031] In the present application, the basic amino acid preferably includes one or both of lysine and arginine.

[0032] In the present application, the alkyl amido acid anion preferably has the structure shown in Formula I:

[0033]

[0034] In Formula I, R1 is hydrogen or methyl;

[0035] R is hydrogen, methyl, one or several of them;

[0036] n is any integer from 2 to 11, preferably from 3 to 10, more preferably from 4 to 8, and further preferably from 5 to 6.

[0037] In the present application, the alkyl amido acid preferably includes one or several of lauroyl glutamic acid anion, lauroyl sarcosine anion, lauroyl glycine anion, lauroyl aspartic acid anion, lauroyl alanine anion, octanoyl glutamic acid anion, octanoyl sarcosine anion, octanoyl glycine anion, octanoyl aspartic acid anion, and octanoyl alanine anion.

[0038] The amino acid-based protic green ionic liquid provided by the present application uses a basic amino acid (lysine and arginine) as a cation and an alkyl amido acid as an organic anion, and can significantly improve the friction reduction, wear resistance and corrosion resistance of water as a water-based lubricating additive. The active nitrogen element in the molecular structure of the ionic liquid of the present application can undergo a tribochemical reaction with the friction pair to generate a friction film, which not only improves the friction reduction and wear resistance of the water-based lubricating liquid, but also greatly improves its extreme pressure performance. The cation and anion of the ionic liquid provided by the present application are both amino acid compounds, which are safe, non-toxic and biodegradable, and are an environmentally friendly ionic liquid. The ionic liquid provided by the present application does not contain phosphorus and sulfur elements, and is a green lubricating additive.

[0039] The present application provides a preparation method of the above-mentioned amino acid-based protic green ionic liquid, which comprises the following steps:

[0040] Mixing the basic amino acid and the alkyl amido acid compound with the aqueous solvent to perform a proton exchange reaction to obtain an amino acid-based protic green ionic liquid aqueous solution; the aqueous solvent is a mixture of water and ethanol;

[0041] Removing the aqueous solvent of the amino acid-based protic green ionic liquid aqueous solution to obtain an amino acid-based protic green ionic liquid.

[0042] The application mixes basic amino acid and alkyl amido acid compound with water phase solvent, carries out proton exchange reaction, and obtains amino acid base proton type green ionic liquid water phase solution.

[0043] In the application, the basic amino acid preferably includes lysine and / or arginine. In the application, the alkyl amido acid compound preferably includes one or more of lauroyl glutamic acid, lauroyl sarcosine, lauroyl glycine, lauroyl aspartic acid, lauroyl alanine, octanoyl glutamic acid, octanoyl sarcosine, octanoyl glycine, octanoyl aspartic acid and octanoyl alanine.

[0044] In the application, the basic amino acid and alkyl amido acid compound are preferably mixed in an equimolar ratio of active functional groups.

[0045] In the application, the water phase solvent is a mixture of water and ethanol; in the application, the volume ratio of water and ethanol is preferably 30:70-70:30, more preferably 40:60-60:40, and further preferably 50:50.

[0046] The application does not have special requirements for the mixing method, and a mixing method known to those skilled in the art can be used.

[0047] In the application, the proton exchange reaction is preferably carried out under heating, and the temperature of the proton exchange reaction is preferably 30-100℃, more preferably 50-80℃; the time is preferably 1-36h, more preferably 5-25h, and further preferably 10-20h. In the application, the proton exchange reaction is preferably carried out under stirring.

[0048] In the application, the mass content of the amino acid base proton type green ionic liquid in the amino acid base proton type green ionic liquid water phase solution is preferably 1-50%, more preferably 5-30%, and further preferably 10-20%.

[0049] After obtaining the amino acid base proton type green ionic liquid water phase solution, the application removes the water phase solvent of the amino acid base proton type green ionic liquid water phase solution to obtain an amino acid base proton type green ionic liquid. In the application, the removal of the water phase solvent is preferably rotary evaporation. The application does not have special requirements for the rotary evaporation method, and a method known to those skilled in the art can be used.

[0050] After the rotary evaporation, the application preferably dries the obtained rotary evaporation product. In the application, the drying is preferably vacuum drying, and the drying time is preferably ≥12h.

[0051] The application provides the use of the above-mentioned amino acid base proton type green ionic liquid as a water-based lubricating liquid additive.

[0052] The present application provides a lubricant comprising a base lubricating liquid and the amino acid-based protic green ionic liquid described above.

[0053] In the present application, the base lubricating liquid is one of water, water-ethylene glycol, water-polyethylene glycol, water-glycerol, water-diethylene glycol, water-triethylene glycol, water-propylene glycol, polyethylene glycol, glycerol, diethylene glycol and triethylene glycol. In the present application, the volume percentage of water in the water-ethylene glycol, water-polyethylene glycol, water-glycerol, water-diethylene glycol, water-triethylene glycol and water-propylene glycol systems is preferably 30-70%, more preferably 40-60%.

[0054] In the present application, the mass percentage of the amino acid-based protic green ionic liquid in the lubricant is preferably 0.1-10%, more preferably 0.5-8%, and further preferably 1-5%.

[0055] The amino acid-based protic green ionic liquid provided by the present application, the preparation method thereof and the application thereof as a water-based lubricant additive will be described in detail below in conjunction with examples, but they should not be understood as limiting the scope of protection of the present application.

[0056] Example 1

[0057] Preparation of lysine-lauric glutamic acid ionic liquid: 3.294 g (0.01 mol) of lauric glutamic acid and 2.844 g (0.02 mol) of lysine were added to a 250 mL round-bottom flask, dissolved in 70 mL of water-ethanol (1:1), stirred at 80°C for 4 hours, the water and anhydrous ethanol in the solution were removed by rotary evaporation, and finally dried in a vacuum drying oven at room temperature for more than 12 h to obtain the ionic liquid.

[0058] The SRV-IV oscillating friction and wear tester produced by the German Optimol Oil Company was used to evaluate the lubricating performance of the invented ionic liquid as a water lubricant additive. Water was selected as the control sample, and solutions with different concentrations of 0.5wt%, 1wt%, 2wt% and 3wt% were selected as the comparative experiments. The test conditions selected in the tribology experiment were: load 100 N, temperature 25°C, frequency 25 Hz, amplitude 1 mm, and experimental time 30 min; the test ball was Φ10 mm AISI 52100 steel ball; in the steel / steel friction pair, the lower sample was Φ24 mm, 7.9 mm thick AISI 52100 steel block with a hardness of 700-750 HV; the wear volume of the lower sample was measured by the MicroXAM-800 non-contact three-dimensional surface profiler. The average friction coefficient and average wear volume of the ionic liquid with different concentrations in the base lubricating liquid are shown in Table 1.

[0059] Table 1 Average friction coefficient and average wear volume of different concentrations of ionic liquid in water

[0060]

[0061] Example 2

[0062] Preparation of arginine-lauric acid ionic liquid: 3.294 g (0.01 mol) lauric acid and 3.484 g (0.02 mol) arginine were added into a 250 mL round bottom flask, dissolved in 70 mL water-ethanol (1 : 1), stirred at 80 °C for 6 hours, the water and anhydrous ethanol in the solution were removed by rotary evaporation, and finally dried in a vacuum drying oven at room temperature for more than 12 h to obtain the ionic liquid.

[0063] Different concentrations of ionic liquid were added in water and dissolved uniformly, the friction behavior of the obtained ionic liquid in the base lubricating liquid was evaluated according to the method in Example 1, the test conditions were the same as in Example 1, and the test results are shown in Table 2:

[0064] Table 2 Average friction coefficient and average wear volume of ionic liquid obtained in Example 2 in water

[0065]

[0066] Example 3

[0067] Preparation of lysine-lauric acid ionic liquid: 2.714 g (0.01 mol) lauric acid and 1.422 g (0.01 mol) lysine were added into a 250 mL round bottom flask, dissolved in 70 mL water-ethanol (1 : 1), stirred at 80 °C for 5 hours, the water and anhydrous ethanol in the solution were removed by rotary evaporation, and finally dried in a vacuum drying oven at room temperature for more than 12 h to obtain the ionic liquid.

[0068] Different concentrations of ionic liquid were added in water and dissolved uniformly, the friction behavior of the obtained ionic liquid in the base lubricating liquid was evaluated according to the method in Example 1, the test conditions were the same as in Example 1, and the test results are shown in Table 3:

[0069] Table 3 Average friction coefficient and average wear volume of ionic liquid obtained in Example 3 in water

[0070]

[0071] Example 4

[0072] Preparation of Arginine-Lauric Arginate Ionic Liquid: 2.714 g (0.01 mol) lauric arginate and 1.742 g (0.01 mol) arginine were added into a 250 mL round bottom flask, dissolved in 70 mL water-ethanol (1 : 1), stirred at 80 °C for 4 hours, the water and anhydrous ethanol in the solution were removed by rotary evaporation, and finally dried in a vacuum drying oven at room temperature for more than 12 h to obtain the ionic liquid.

[0073] Different concentrations of ionic liquid were added in water and dissolved uniformly, the friction behavior of the obtained ionic liquid in the base lubricating liquid was evaluated according to the method in Example 1, the test conditions were the same as in Example 1, and the test results are shown in Table 4:

[0074] Table 4 Average friction coefficient and average wear volume of ionic liquid obtained in Example 4 in water

[0075]

[0076]

[0077] Example 5

[0078] Preparation of Lysine-Octanoyl Glutamate Ionic Liquid: 2.953 g (0.01 mol) octanoyl glutamate and 2.844 g (0.02 mol) lysine were added into a 250 mL round bottom flask, dissolved in 70 mL water-ethanol (1 : 1), stirred at 70 °C for 6 hours, the water and anhydrous ethanol in the solution were removed by rotary evaporation, and finally dried in a vacuum drying oven at room temperature for more than 12 h to obtain the ionic liquid.

[0079] Different concentrations of ionic liquid were added in water and dissolved uniformly, the friction behavior of the obtained ionic liquid in the base lubricating liquid was evaluated according to the method in Example 1, the test conditions were the same as in Example 1, and the test results are shown in Table 5:

[0080] Table 5 Average friction coefficient and average wear volume of ionic liquid obtained in Example 5 in water

[0081]

[0082] Example 6

[0083] Preparation of Arginine-Lauric Arginate Ionic Liquid: 2.714 g (0.01 mol) lauric arginate and 1.742 g (0.01 mol) arginine were added into a 250 mL round bottom flask, dissolved in 70 mL water-ethanol (1 : 1), stirred at 80 °C for 4 hours, the water and anhydrous ethanol in the solution were removed by rotary evaporation, and finally dried in a vacuum drying oven at room temperature for more than 12 h to obtain the ionic liquid.

[0084] Different concentrations of the ionic liquid were added to water and dissolved uniformly, and the friction behavior of the obtained ionic liquid in the base lubricating liquid was evaluated according to the method in Example 1, and the test conditions were the same as in Example 1, and the test results are shown in Table 6:

[0085] Table 6 Average friction coefficient and average wear volume of the ionic liquid obtained in Example 6 in water

[0086]

[0087] Example 1 Corrosion resistance test

[0088] The ionic liquid prepared in Examples 1-6 was configured into a 1% aqueous solution, and a corrosion resistance test was performed according to the standard of GB6144-85, with water as the control group. The same specification cast iron pieces were immersed in water, 1% Example 1 aqueous solution, 1% Example 2 aqueous solution, 1% Example 3 aqueous solution, 1% Example 4 aqueous solution, 1% Example 5 aqueous solution, and 1% Example 6 aqueous solution at 55±2℃, respectively, and after 24h, they were taken out, ultrasonically cleaned in acetone, and dried with high-speed gas. The surface of the cast iron pieces was observed under an optical microscope, and the corrosion conditions of the cast iron pieces in the above different aqueous solutions were analyzed. The corrosion grade was obtained, and the results are shown in Table 7.

[0089] Table 7 Corrosion resistance test results of the ionic liquid obtained in Examples 1-6

[0090] Sample Corrosion Rating Water D Example 1 A Example 2 A Example 3 A Example 4 A Example 5 A Example 6 A

[0091] In Table 7, A represents no rust, shiny as new; B represents no rust but slightly lose luster; C represents light rust and slight loss of luster; and D represents heavy rust or severe loss of luster.

[0092] According to the experimental results in Table 7, it can be seen that the ionic liquid provided by the application has good corrosion resistance when used as an additive for water-based lubricating liquid.

[0093] According to the above examples, it can be seen that the amino acid-based protic ionic liquid disclosed in the application can greatly improve the tribological performance of water lubricating liquid. In water, it not only has a low friction coefficient and excellent anti-wear performance, but also has excellent corrosion resistance. In addition, the anion and cation required for the synthesis of the ionic liquid are both natural amino acid compounds, do not contain phosphorus and sulfur elements, are green and pollution-free, safe and non-toxic, biodegradable, and low in cost. The active nitrogen element in the molecular structure can undergo a tribochemical reaction with the friction pair to generate a friction film, which not only improves the friction-reducing and anti-wear performance of the water-based lubricating liquid, but also greatly improves its extreme pressure performance. The synthesis process of the amino acid-based protic ionic liquid is simple, and it has a broad prospect as a water-based lubricating additive.

[0094] The above merely describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the protection scope of the present application.

Claims

1. Application of amino acid-based protic green ionic liquid as additive of water-based lubricant; The amino acid-based protic green ionic liquid has a general structure of A + B - , wherein A + represents an organic cation, and B - represents an organic anion. the organic cation is a basic amino acid cation, and the anion is an alkyl amido acid anion; the basic amino acid is selected from one or both of lysine and arginine; the alkyl amido acid is selected from one or more of lauroyl glutamic acid anion, octanoyl glutamic acid anion and octanoyl sarcosine anion.

2. Use according to claim 1, characterized in that, The preparation method of the amino acid-based protic green ionic liquid comprises the following steps: Mixing the basic amino acid and the alkyl amido acid compound with the aqueous phase solvent to carry out a proton exchange reaction to obtain an amino acid-based protic green ionic liquid aqueous solution; the aqueous phase solvent is a mixture of water and ethanol; Removing the aqueous phase solvent of the amino acid-based protic green ionic liquid aqueous solution to obtain the amino acid-based protic green ionic liquid.

3. Use according to claim 2, characterized in that, In the preparation method of the amino acid-based protic green ionic liquid, the basic amino acid and the alkyl amido acid compound are mixed in an equimolar ratio according to the active functional groups; In the amino acid-based protic green ionic liquid aqueous solution, the mass content of the amino acid-based protic green ionic liquid is 1-50%.

4. Use according to claim 2, wherein the process for the preparation of an amino acid based protic green ionic liquid is characterized in that, The volume ratio of water to ethanol is 30:70-70:30; The temperature of the proton exchange reaction is 30-100℃, and the time is 1-36h.

5. A lubricant comprising a base lubricant and an amino acid-based protic green ionic liquid; the amino acid-based protic green ionic liquid is the amino acid-based protic green ionic liquid in claim 1.

6. The lubricant of claim 5, wherein, The base lubricant is one of water, water-glycol, water-polyethylene glycol, water-glycerol, water-diethylene glycol, water-triethylene glycol, water-propylene glycol, polyethylene glycol, glycerol, diethylene glycol and triethylene glycol; The mass percentage content of the amino acid-based protic green ionic liquid in the lubricant is 0.1-10%.

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