An ionic liquid functionalized polydopamine nano-lubricant additive and a preparation method thereof

Abstract

The present invention provides an ionic liquid functionalized polydopamine nano-lubricant additive and a preparation method thereof, and relates to the field of new material technology. The preparation steps of the additive include: taking polydopamine nanoparticles and dispersing them in water, then adding 1-(3-aminopropyl) imidazole, stirring the reaction continuously for 10-12 hours, separating and purifying the product; dispersing the product of the previous step into a monohydric alcohol, adding iodomethane, stirring continuously for 6-12 hours under 60-80°C, separating and purifying the product; dispersing the product of the previous step into water, then adding an oil phase solvent, dripping an oily fluorine-containing anion salt solution and stirring the reaction for 0.5-1h, separating the oil phase and removing the solvent in the oil phase after the reaction is completed. The additive of the present invention, due to the rich functional groups in the ionic liquid, can provide a large number of adsorption sites when used as a lubricating additive, accelerate the formation of a friction film, and play a positive role in improving the lubrication performance of nanoparticles.

Description

Technical Field

[0001] The invention belongs to the technical field of new materials, and in particular relates to an ionic liquid functionalized polydopamine nano-lubricant additive and a preparation method of the ionic liquid functionalized polydopamine nano-lubricant additive. Background Art

[0002] Lubricant additives are of great significance for improving the tribological properties of base oils, especially the anti-wear and friction-reducing properties. The addition of lubricant additives can effectively make up for the shortcomings of base oils such as insufficient load-bearing capacity and unstable lubrication performance during use. Organic polymer nanoparticles have excellent tribological potential value due to their uniform particle size, wide source of raw materials, and good interfacial adsorption properties. However, there are many challenges in developing organic polymer nanolubricant additives with excellent synthetic oil dispersibility and interfacial activity. As a derivative of adhesion protein, dopamine can form surface-modified polydopamine nanoparticles through self-oxidation polymerization in weakly alkaline aqueous solutions, providing a potential way to overcome the above difficulties.

[0003] Ionic liquids have significant advantages such as high thermal stability, flame retardancy, high ionic conductivity and wide electrochemical window, and have been used directly or indirectly in the field of lubricant additives. Grafting ionic liquids onto the surface of nanoparticles to form composite materials can not only exert the synergistic lubrication effect of the two, but also effectively promote the dispersion of nanoparticles in various solvents. Unfortunately, in the conventional direct grafting method, the inherent polarity and charge of ionic liquids make it easy to cause nanomaterials to precipitate during the modification process, affecting the dispersibility and the grafting efficiency cannot be guaranteed. Designing new grafting strategies has a positive role in exploring the synergistic lubrication effect between ionic liquids and nanoparticles.

[0004] Although polydopamine nanoparticles have excellent tribological potential, their inherent property of poor oil dispersion stability limits their widespread application as lubricant additives. Therefore, improving the oil dispersibility of polydopamine nanoparticles is an effective way to broaden the application of polydopamine nanoparticles in the field of oil-based lubricant additives. Summary of the invention

[0005] To solve at least one of the above problems, the additive of the present invention is modified based on polydopamine, which can provide more adsorption sites when used as a lubricating additive, accelerate the formation of friction film, and play a positive role in improving the lubrication performance of nanoparticles.

[0006] The technical solution of the present invention is as follows: a method for preparing an ionic liquid functionalized polydopamine nano-lubricant additive, comprising the following steps:

[0007] S1, taking polydopamine nanoparticles and dispersing them in water, then adding 1-(3-aminopropyl)imidazole, stirring and reacting for 10 to 12 hours, separating and purifying the product to obtain 1-(3-aminopropyl)imidazole-modified polydopamine nanoparticles, wherein every 100 to 200 mg of polydopamine nanoparticles corresponds to 2 to 4 mL of 1-(3-aminopropyl)imidazole;

[0008] S2, dispersing the polydopamine nanoparticles modified with 1-(3-aminopropyl)imidazole in monohydric alcohol, adding methyl iodide, stirring continuously for 6 to 12 hours at 60 to 80° C., separating and purifying the product to obtain polydopamine nanoparticles modified with 1-(3-aminopropyl)imidazole iodide, wherein every 100 to 200 mg of polydopamine nanoparticles corresponds to 10 to 15 mL of methyl iodide;

[0009] S3. Disperse polydopamine nanoparticles modified with 1-(3-aminopropyl) imidazole iodide salt in water, then add an oil phase solvent, dropwise add an aqueous solution of an oily fluorine-containing anion salt and stir to react for 0.5 to 1 hour. After the reaction is completed, separate the oil phase and remove the solvent in the oil phase to obtain the polydopamine nanoparticles modified with 1-(3-aminopropyl) imidazole iodide salt, wherein the mass ratio of the oily fluorine-containing anion salt to the polydopamine nanoparticles modified with 1-(3-aminopropyl) imidazole iodide salt is 1 to 3:1.

[0010] In S2, since the boiling points of monohydric alcohol and methyl iodide are not too high, and the reaction temperature is relatively high, in order to avoid the volatilization of the solvent during the reaction, a condensation reflux device can be used to carry out the reaction.

[0011] In S3, in order to avoid emulsification of the oil phase solvent and the water phase after mixing, the addition amounts of the oil phase solvent and the water phase should not differ too much. Preferably, the volume ratio of the oil phase solvent to the water phase is 1:0.8-1.2.

[0012] One embodiment of the present invention is that the polydopamine nanoparticles are prepared by the following method:

[0013] Take dopamine hydrochloride, add it into water and dissolve it to obtain a dopamine hydrochloride solution, then take water, ethanol and ammonia water in a volume ratio of 90:40:1.5-3 and mix them evenly to obtain a mixed solution, mix the dopamine hydrochloride solution and the mixed solution, and continue stirring and reacting for 6-24 hours at room temperature and in the dark, and separate and purify the product after the reaction to obtain polydopamine nanoparticles; wherein, for the dopamine hydrochloride solution, every 10 ml of water corresponds to 0.3-0.8 g of dopamine hydrochloride. At the same time, the added volume ratio of the mixed solution to the dopamine hydrochloride solution is 6-14:1.

[0014] Theoretically, the polydopamine nanoparticles in the prior art also have relatively abundant functional groups, and therefore, can also be applied to the present invention. However, the cost of the existing polydopamine nanoparticles is relatively high. In order to reduce the cost, the inventors have proposed a new method for preparing polydopamine nanoparticles.

[0015] In this method, the concentration of polydopamine hydrochloride in water should not be too high: too high concentration will cause polydopamine to precipitate during the reaction, making it difficult to obtain nano-scale polydopamine; but it should not be too low: too low concentration will cause the reaction product to be difficult to separate and obtain formed polydopamine nanoparticles after the reaction. The inventors have found through a large number of experiments that when 10 ml of water contains 0.3 to 0.8 g of dopamine hydrochloride, its final performance is better. Similarly, for the mixed solution, the amount of ammonia water added should not be too high: when it is too high, the particle size of the obtained polydopamine nanoparticles is too small, resulting in difficulties in the subsequent separation and purification process and a low yield; but it should not be too low: too low concentration will result in the obtained polydopamine particles having a large particle size, which does not meet the actual use requirements. After a large number of experiments by the inventors, it was found that the volume ratio of water, ethanol and ammonia water is 90:40:1.5 to 3, and the effect is better. Preferably, the ratio of the three is 90:40:2.5.

[0016] Furthermore, the specific operation of separating and purifying the polydopamine nanoparticles is: centrifuging the reaction product at 10000-12000 r / min for 20-30 min, then washing the solid phase with water, and repeating the above operation several times.

[0017] One embodiment of the present invention is that in S1, the specific operation of separation and purification is: centrifuging the reaction product at 10000-12000 r / min for 20-30 min, then washing the solid phase with ethanol, and repeating the above operation several times. In this process, the inventors found that if the 1-(3-aminopropyl)imidazole-modified polydopamine nanoparticles are washed with water, the 1-(3-aminopropyl)imidazole grafted to the surface of the polydopamine nanoparticles will dissociate, and this situation can be avoided when washing with ethanol. At the same time, another purpose of washing with ethanol is to remove water from the product as much as possible to avoid the influence of moisture in the product on subsequent reactions.

[0018] One embodiment of the present invention is that in S2, the monohydric alcohol is methanol or ethanol. Considering the biological toxicity of both, ethanol is preferred.

[0019] One embodiment of the present invention is that in S2, the specific operation of separation and purification is: centrifuging the reaction product at 8000-9000r / min for 3-5min, then washing the solid phase with ethanol, and repeating the above operation several times. In this step, the product after the reaction will appear in the form of precipitation. Generally speaking, the reaction product can be obtained by filtration, vacuum filtration, centrifugation, or rotary evaporation using the low boiling point of the reaction solvent. However, the nanoparticles obtained by filtration and filtration are not conducive to the purification and collection of samples. Rotary evaporation also faces the same problem. Comprehensive consideration of the use of a short and low-speed centrifugation process can better collect and purify the sample. The centrifugal speed is 8000-9000r / min and the centrifugal time is 3-5min.

[0020] One embodiment of the present invention is that in S3, the oil phase solvent is ethyl acetate, and the oily fluorine-containing anion salt is one of sodium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl imide) and potassium hexafluorophosphate. As for the oily fluorine-containing anion salt, as long as it has a corresponding affinity for the lubricating oil base oil and can form an ionic liquid through ion exchange, it can be applied to the present invention; however, considering the actual difficulty and cost of obtaining, the more common sodium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl imide) and potassium hexafluorophosphate are selected in the present invention.

[0021] In particular, as for the oil phase solvent, generally speaking, any oil phase solvent that is immiscible with water can be applied to the present invention, such as ethyl acetate, n-butanol, etc. However, from the actual production process, the boiling point of n-butanol is relatively high and it is not easy to remove in the subsequent process. Therefore, it is preferred to use an oil phase solvent with a lower boiling point, such as ethyl acetate.

[0022] In particular, in S3, when separating the solvent in the oil phase, since the boiling point of ethyl acetate is relatively low, theoretically, the oil phase solvent can be removed in a variety of ways, such as rotary evaporation, vacuum distillation, natural evaporation, etc. However, from the perspective of the difficulty of collecting the final product, it is preferred to evaporate the oil phase naturally under ventilation conditions, and the final product is less difficult to collect.

[0023] Meanwhile, for oily fluorine-containing anion salts, they can be dissolved in water in advance during use to speed up the reaction.

[0024] Another object of the present invention is to provide an ionic liquid functionalized polydopamine nano-lubricant additive, which is prepared by any of the above-mentioned methods. The additive is added to lubricating oil and can be used for friction reduction and anti-wear of metal / metal friction pairs.

[0025] The beneficial effects of the present invention are:

[0026] The preparation method of the ionic liquid functionalized polydopamine nano-lubricant additive of the present invention benefits from the abundant reaction sites on the surface of polydopamine nanoparticles, utilizes the Michael addition reaction and the Schiff base reaction between the amino group and the catechol group, first modifies the surface of the polydopamine nanoparticles with 1-(3-aminopropyl)imidazole, and then "attacks" the imidazole group with methyl iodide, and gradually obtains the polydopamine nanoparticles modified with 1-(3-aminopropyl)imidazole iodide salt, and this method successfully avoids the formation of flocculation of the nanoparticles due to the charge effect when the ionic liquid is directly grafted onto the surface of the polydopamine nanoparticles. At the same time, through simple anion exchange, the lipophilic anions are exchanged onto the surface of the nanoparticles, and the durable and stable dispersion of the polydopamine nanoparticles in the oil is realized. The abundant functional groups in the ionic liquid can provide more adsorption sites when used as a lubricating additive, accelerate the formation of the friction film, and play a positive role in improving the lubrication performance of the nanoparticles. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is the SEM result of the products of multiple steps in Example 1;

[0028] Figure 2 is the SEM result of polydopamine nanoparticles prepared according to the comparative example of the present invention;

[0029] Figure 3 1 is the XPS result of the polydopamine nanoparticles prepared according to Example 1 of the present invention before and after modification;

[0030] Figure 4 The dispersibility of the polydopamine nanoparticles before and after modification prepared according to Example 1 of the present invention in the polyethylene glycol base oil;

[0031] Figure 5 This is a comparison chart of friction coefficients of ionic liquid functionalized polydopamine nano-lubricant additives used as oil-based lubricant additives according to Examples 1, 2, and 3 of the present invention;

[0032] Figure 6 3D profilometer analysis results of the wear track in the friction test according to Example 1 of the present invention. DETAILED DESCRIPTION

[0033] In order to make the technical solutions and technical advantages of the present invention more clear, the technical solutions in the implementation process of the present invention will be clearly and completely described below in combination with embodiments and drawings.

[0034] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0035] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0036] Example 1

[0037] (1) Preparation of polydopamine nanoparticles: 0.5 g of dopamine hydrochloride powder was added to 10 ml of water, and a dopamine hydrochloride solution was obtained after ultrasonic treatment; water, ethanol and ammonia water in a volume ratio of 90:40:2.5 ml were taken, and stirred at 30° C. for 30 min to obtain a mixed solution; the dopamine hydrochloride solution and the mixed solution were mixed, and stirred for 12 h at 30° C. in the dark; the product after the reaction was centrifuged at a speed of 11500 r / min for 25 min, the solid phase was washed with water, and the centrifugation and washing operations were repeated 4 times to obtain polydopamine nanoparticles;

[0038] (2) 200 mg of polydopamine nanoparticles were dispersed in 40 ml of water and stirred at 30°C to form a stable dispersion. 3 ml of 1-(3-aminopropyl)imidazole was added and stirred for 12 h. The product after the reaction was centrifuged at 11500 r / min for 25 min. The solid phase was washed with ethanol. The centrifugation and washing operations were repeated 3 times to obtain 1-(3-aminopropyl)imidazole-modified polydopamine nanoparticles.

[0039] (3) dispersing the 1-(3-aminopropyl)imidazole-modified polydopamine nanoparticles obtained in step (2) into 40 ml of ethanol, adding 15 ml of iodomethane, stirring at 60° C. for 12 h, centrifuging the reaction product at a speed of 8500 r / min for 4 min, washing the solid phase with ethanol, and repeating the centrifugation and washing operation three times to obtain 1-(3-aminopropyl)imidazole iodide-modified polydopamine nanoparticles;

[0040] (4) The 1-(3-aminopropyl) imidazole iodide-modified polydopamine nanoparticles obtained in step (3) are dispersed in 20 ml of water, followed by adding 20 ml of ethyl acetate, and 5 ml of an aqueous solution containing 400 mg of lithium bis(trifluoromethanesulfonyl)imide is added dropwise during stirring, and stirring is continued for 0.5 h; the oil phase is separated, and the ethyl acetate is removed at 30° C. under ventilation conditions to obtain an ionic liquid functionalized polydopamine nano-lubricant additive.

[0041] Example 2

[0042] (1) adding 0.7 g of dopamine hydrochloride powder to 10 ml of water, stirring to obtain a dopamine hydrochloride solution; taking water, ethanol and ammonia water in a volume ratio of 90:40:3.0 ml, stirring at 30° C. for 20 min to obtain a mixed solution; mixing the dopamine hydrochloride solution and the mixed solution, stirring for 6 h at 30° C. in the dark; centrifuging the reaction product at a speed of 11000 r / min for 30 min, washing the solid phase with water, and repeating the centrifugation and washing operations 4 times to obtain polydopamine nanoparticles;

[0043] (2) 200 mg of polydopamine nanoparticles were dispersed in 40 ml of water and stirred at 30°C to form a stable dispersion. 4 ml of 1-(3-aminopropyl)imidazole was added and stirred for 10 h. The product after the reaction was centrifuged at 11000 r / min for 30 min. The solid phase was washed with ethanol. The centrifugation and washing operations were repeated 3 times to obtain 1-(3-aminopropyl)imidazole-modified polydopamine nanoparticles.

[0044] (3) dispersing the 1-(3-aminopropyl)imidazole-modified polydopamine nanoparticles obtained in step (2) into 40 ml of anhydrous monohydric alcohol, adding 15 ml of iodomethane, stirring at 60° C. for 12 h, centrifuging the reaction product at a speed of 9000 r / min for 3 min, washing the solid phase with ethanol, and repeating the centrifugation and washing operation three times to obtain 1-(3-aminopropyl)imidazole iodide-modified polydopamine nanoparticles;

[0045] (4) Dispersing the 1-(3-aminopropyl) imidazole iodide-modified polydopamine nanoparticles obtained in step (3) into 30 ml of water, then adding 30 ml of ethyl acetate, adding dropwise 5 ml of an aqueous solution containing 300 mg of potassium hexafluorophosphate while stirring, and continuing stirring for 0.5 h; separating the oil phase, removing the ethyl acetate at 30° C. under ventilation conditions to obtain an ionic liquid functionalized polydopamine nano-lubricant additive.

[0046] Example 3

[0047] (1) adding 0.4 g of dopamine hydrochloride powder to 10 ml of water, and obtaining a dopamine hydrochloride solution after ultrasonication or stirring; taking water, ethanol and ammonia water in a volume ratio of 90:40:2.0 ml, stirring at 30° C. for 30 min to obtain a mixed solution; mixing the dopamine hydrochloride solution and the mixed solution, and continuously stirring at 30° C. in the dark for 12 h; centrifuging the reaction product at a speed of 12000 r / min for 20 min, washing the solid phase with water, and repeating the centrifugation and washing operations 4 times to obtain polydopamine nanoparticles;

[0048] (2) 100 mg of polydopamine nanoparticles were dispersed in 30 ml of water and stirred at 35°C to form a stable dispersion. Then, 2 ml of 1-(3-aminopropyl)imidazole was added and stirred for 10 h. The product after the reaction was centrifuged at 12,000 r / min for 20 min. The solid phase was washed with ethanol. The centrifugation and washing operations were repeated 3 times to obtain 1-(3-aminopropyl)imidazole-modified polydopamine nanoparticles.

[0049] (3) dispersing the 1-(3-aminopropyl)imidazole-modified polydopamine nanoparticles obtained in step (2) into 30 ml of anhydrous monohydric alcohol, adding 10 ml of iodomethane, stirring at 80° C. for 6 h, centrifuging the reaction product at a speed of 8500 r / min for 4 min, washing the solid phase with ethanol, and repeating the centrifugation and washing operation 3 times to obtain 1-(3-aminopropyl)imidazole iodide-modified polydopamine nanoparticles;

[0050] (4) Disperse the 1-(3-aminopropyl) imidazole iodide-modified polydopamine nanoparticles obtained in step (3) into 30 ml of water, then add 30 ml of ethyl acetate, add 5 ml of an aqueous solution containing 100 mg of sodium tetrafluoroborate dropwise during stirring, and continue stirring for 1 hour; separate the oil phase, remove the ethyl acetate at 30° C. under ventilation conditions to obtain an ionic liquid functionalized polydopamine nanolubricant additive.

[0051] In order to further illustrate the effect of the present invention, the ionic liquid functionalized polydopamine nano-lubricant additive of the above embodiment is specifically tested below.

[0052] Comparative Example

[0053] (1) Preparation of polydopamine nanoparticles: 0.5 g of dopamine hydrochloride powder was added to 10 ml of water, and a dopamine hydrochloride solution was obtained after ultrasonic treatment; water, ethanol and ammonia water in a volume ratio of 90:40:0.5 ml were taken, and stirred at 30° C. for 30 min to obtain a mixed solution; the dopamine hydrochloride solution and the mixed solution were mixed, and stirred for 12 h at 30° C. in the dark; the product after the reaction was centrifuged at a speed of 11500 r / min for 25 min, the solid phase was washed with water, and the centrifugation and washing operations were repeated 4 times to obtain polydopamine nanoparticles;

[0054] (2) 200 mg of polydopamine nanoparticles were dispersed in 40 ml of water and stirred at 30°C to form a stable dispersion. 3 ml of 1-(3-aminopropyl)imidazole was added and stirred for 12 h. The product after the reaction was centrifuged at 11500 r / min for 25 min. The solid phase was washed with ethanol. The centrifugation and washing operations were repeated 3 times to obtain 1-(3-aminopropyl)imidazole-modified polydopamine nanoparticles.

[0055] (3) dispersing the 1-(3-aminopropyl)imidazole-modified polydopamine nanoparticles obtained in step (2) into 40 ml of ethanol, adding 15 ml of iodomethane, stirring at 60° C. for 12 h, centrifuging the reaction product at a speed of 8500 r / min for 4 min, washing the solid phase with ethanol, and repeating the centrifugation and washing operation three times to obtain 1-(3-aminopropyl)imidazole iodide-modified polydopamine nanoparticles;

[0056] (4) The 1-(3-aminopropyl) imidazole iodide-modified polydopamine nanoparticles obtained in step (3) are dispersed in 20 ml of water, followed by adding 20 ml of ethyl acetate, and 5 ml of an aqueous solution containing 400 mg of lithium bis(trifluoromethanesulfonyl)imide is added dropwise during stirring, and stirring is continued for 0.5 h; the oil phase is separated, and the ethyl acetate is removed at 30° C. under ventilation conditions to obtain an ionic liquid functionalized polydopamine nano-lubricant additive.

[0057] 1. SEM analysis

[0058] Figure 1 The SEM results of the product of Example 1 are given. Figure 1 a in the figure is the SEM result of unmodified polydopamine nanoparticles. Figure 1 b is the SEM result of polydopamine nanoparticles modified with 1-(3-aminopropyl)imidazole. Figure 1 c in the figure is the SEM result of polydopamine nanoparticles modified with 1-(3-aminopropyl)imidazolium iodide. Figure 1 Figure d shows the SEM results of polydopamine nanoparticles modified with oil-soluble 1-(3-aminopropyl) imidazole iodide. From the SEM results, the nanoparticles before and after modification are spherical, and their average particle sizes increase slightly as the reaction proceeds, and are 92.71nm, 93.45nm, 94.09nm and 96.36nm, respectively. Figure 2 , gives the SEM results of polydopamine nanoparticles obtained under comparative conditions, i.e. in an alkaline environment adjusted with 0.5 ml of ammonia water. The particle size distribution is uneven and the average particle size is 299.81 nm. The large particle size is not conducive to its entry into the friction interface. When used as a lubricating additive, it may not achieve a good friction reduction and anti-wear effect.

[0059] 2.XPS analysis

[0060] Figure 3 The XPS results of the product of Example 1 are given. As can be seen from the figure, the unmodified polydopamine nanoparticles mainly detected C, N and O elements. When the imidazole group containing more N elements was grafted onto the surface of the polydopamine nanoparticles, the detected signal of the N element became stronger. The subsequent addition of iodomethane not only detected the I element, but also significantly increased the content of the C element due to the introduction of methyl groups. After anion exchange, the signal of the I element disappeared, and the F and S elements belonging to bistrifluoromethanesulfonimide were detected accordingly. The above results show that the synthesis of the embodiment of the present invention is successful.

[0061] 3. Dispersion stability test

[0062] Whether the lubricating additive can be stably dispersed in the base oil is an important indicator for evaluating its performance. Take the nanoparticles obtained in Example 1 before and after modification, ultrasonically add them to the base oil under the same conditions, with a mass fraction of 1.2wt%, and let them stand for a period of time to compare the dispersion stability of the two. Figure 4 As shown in the figure, the pure polydopamine nanoparticles just after the ultrasound showed obvious coagulation phenomenon, with a large amount of precipitation at the bottom. Due to the effect of gravity, obvious sedimentation appeared on the second day, and the dispersibility was poor. However, the polydopamine nanoparticles modified with ionic liquid formed a clear dispersion in the oil, and after standing for 30 days, there was still no precipitation, showing good dispersion stability.

[0063] 4. Friction reduction and anti-wear performance test

[0064] The products of Examples 1, 2, 3 and the comparative example were uniformly dispersed in the base oil, and then the lubrication performance of the steel / steel friction pair was tested. The friction coefficient comparison results are as follows: Figure 5 As shown in a in the figure, the polydopamine nanoparticles modified by the three oil-soluble ionic liquids have a significant effect on improving the lubrication performance of the base oil, while the modified polydopamine nanoparticles obtained by the comparative example have a poor effect on improving the lubrication performance of the base oil. Figure 5 b shows the friction performance test results of the product of Example 1 in the base oil at different addition concentrations, indicating that at a concentration of 1.2wt%, the additive has the most significant improvement on the lubrication performance of the base oil. Figure 6 From the width and depth of the wear track, it can be seen that after adding the additive to the base oil, the width and depth of the wear track are reduced from 483.2μm and 10.2μm under pure base oil lubrication to 353.5μm and 4.7μm respectively, and its anti-wear performance has been significantly improved.

[0065] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A method for preparing an ionic liquid functionalized polydopamine nano-lubricant additive, characterized in that: The following steps are involved: S1. Take polydopamine nanoparticles and disperse them in water, then add 1-(3-aminopropyl)imidazole, continue stirring and react for 10 to 12 hours, separate and purify the product to obtain 1-(3-aminopropyl)imidazole-modified polydopamine nanoparticles, wherein each 100 to 200 mg of polydopamine nanoparticles corresponds to 2 to 4 mL of 1-(3-aminopropyl)imidazole; the separation and purification operation is: centrifuge the reaction product at 10000 to 12000 r / min for 20 to 30 minutes, then wash the solid phase with ethanol, and repeat the centrifugation and washing operation several times to obtain; S2, dispersing the polydopamine nanoparticles modified with 1-(3-aminopropyl)imidazole in monohydric alcohol, adding methyl iodide, stirring continuously for 6 to 12 hours at 60 to 80° C., separating and purifying the product to obtain polydopamine nanoparticles modified with 1-(3-aminopropyl)imidazole iodide, wherein every 100 to 200 mg of polydopamine nanoparticles corresponds to 10 to 15 mL of methyl iodide; S3, dispersing polydopamine nanoparticles modified with 1-(3-aminopropyl) imidazole iodide salt in water, then adding an oil phase solvent, dropping an oily fluorine-containing anion salt aqueous solution and stirring to react for 0.5 to 1 hour, separating the oil phase and removing the solvent in the oil phase after the reaction, wherein the mass ratio of the oily fluorine-containing anion salt to the polydopamine nanoparticles modified with 1-(3-aminopropyl) imidazole iodide salt is 1 to 3:1; The polydopamine nanoparticles are prepared by the following method: adding dopamine hydrochloride into water and dissolving it to obtain a dopamine hydrochloride solution, then taking water, ethanol and ammonia water in a volume ratio of 90:40:1.5-3 and mixing them evenly to obtain a mixed solution, mixing the dopamine hydrochloride solution and the mixed solution, stirring and reacting for 6-24 hours at room temperature and in the dark, separating and purifying the product after the reaction to obtain the polydopamine nanoparticles; wherein, for the dopamine hydrochloride solution, every 10 ml of water corresponds to 0.3-0.8 g of dopamine hydrochloride; and the added volume ratio of the mixed solution to the dopamine hydrochloride solution is 6-14:

1.

2. The method according to claim 1, characterized in that The specific operation of separating and purifying the polydopamine nanoparticles is: centrifuging the reaction product at 10000-12000 r / min for 20-30 min, then washing the solid phase with water, and repeating the centrifugation and washing operations several times.

3. The method according to claim 1, characterized in that In S2, the monohydric alcohol is methanol or ethanol.

4. The method according to claim 1, characterized in that: In S2, the specific operation of separation and purification is: centrifuging the reaction product at 8000-9000 r / min for 3-5 min, then washing the solid phase with ethanol, and repeating the centrifugation and washing operations several times.

5. The method according to claim 1, characterized in that In S3, the oil phase solvent is ethyl acetate, and the oily fluorine-containing anion salt is one of sodium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide and potassium hexafluorophosphate.

6. An ionic liquid functionalized polydopamine nano-lubricant additive prepared by the method according to any one of claims 1 to 5.

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