Environment-friendly super-lubricating lubricant and preparation method thereof

Abstract

The invention belongs to the technical field of lubricants, and particularly relates to an environment-friendly super-lubricating lubricant and a preparation method thereof. Natural organic acid is used as a basic lubricant, a metal alkaline compound is added, stable macroscopic liquid super lubrication (the friction coefficient is lower than 0.01) can be realized through reasonable proportion regulation and control, and the lubricant is easy to dissolve in water and facilitates subsequent treatment. The selected natural organic acid has the characteristics of low corrosivity, wide source, health and no toxicity, and completely meets the environmental protection standard of green and pollution-free; the metal alkaline compound has the advantages of being easy to prepare and low in cost.

Description

Technical Field

[0001] The invention belongs to the technical field of lubricants, and in particular relates to an environmentally friendly super-lubricant and a preparation method thereof. Background Art

[0002] Friction is an important physical phenomenon that is ubiquitous in nature, and its research involves multiple disciplines such as physics, materials science, and engineering technology. Although friction has a positive effect on stability and energy conversion in some scenarios, it is often regarded as the main source of efficiency loss in many mechanical systems. How to effectively reduce friction and minimize energy consumption has become one of the core issues that need to be urgently solved in the field of modern science and technology. In this context, superlubrication, as a special low-friction state, has attracted widespread attention. The superlubrication phenomenon refers to the fact that under certain conditions, the friction coefficient approaches or even decreases to a minimum value (less than 0.01). Compared with the traditional friction state, the superlubrication state can significantly reduce the energy loss between the contact surfaces, which not only means a significant improvement in the efficiency of the mechanical system, but also helps to reduce wear and failure, thereby improving the durability of the equipment.

[0003] Macroscopic superlubrication is divided into solid superlubrication and liquid superlubrication. Solid superlubrication can achieve extremely low friction at larger-scale solid contact interfaces, which is achieved through material design, surface engineering (such as nanostructure modification) or special lubrication technology, including many two-dimensional material additives or coatings (graphene, diamond-like film, molybdenum disulfide, etc.). However, solid superlubrication also has certain limitations, especially at the macroscopic interface, where external factors (such as pollution, humidity, temperature changes, and mechanical loads) can easily destroy the superlubrication state. In contrast, liquid superlubrication has greater advantages. It can dynamically adapt to the deformation of the fluid interface, more effectively reduce frictional resistance, and has a wider range of environmental adaptability.

[0004] At present, researchers have reported a variety of liquid superlubricants, including water-based lubricants based on inorganic acids, ionic liquids, aqueous solutions of acids and polyols, and oil-based lubricants. However, most liquid lubricating materials have adverse effects on the environment to a certain extent. Globally, environmental protection and sustainable development are receiving increasing attention, and the environmental problems of traditional lubricants have become a challenge that needs to be solved urgently. Therefore, finding green and renewable lubricating alternatives has become an important direction of current scientific research.

[0005] Nathan et al. (Wear, 2022, 498 - 499, 204328) analyzed the sliding friction and wear of different ceramics under water lubrication conditions, and analyzed their wear mechanisms and lubrication states. The study found that due to the long running - in period, different degrees of wear appeared on the surface, which would reduce the durability of the equipment. Li Jinjin et al. from Tsinghua University (Langmuir, 2018, 34(12): 3578–3587) found that adding boric acid as a lubricant additive to an ethylene glycol aqueous solution could achieve superlubrication of Si3N4 / SiO2, with a friction coefficient as low as 0.004 - 0.006. However, this additive has slight toxicity and may pose a potential danger to users. Maria - Isabel et al. (Tribology International, 2022, 169, 107462) reported the friction behavior of unsaturated fatty acid - based lubricants between different friction pairs and found that ricinoleic acid could achieve superlubrication between steel / diamond - like carbon film (a - C), but the surface coating technology would increase the material cost and the applicable range is relatively limited. Therefore, how to design liquid lubricants that can meet various requirements still faces huge challenges. Summary of the Invention

[0006] The present invention discloses an environmentally friendly superlubricating lubricant and its preparation method. The invention is based on natural organic acids as the base lubricant and adds metal alkaline compounds. Through reasonable ratio regulation, stable macroscopic liquid superlubrication (friction coefficient below 0.01) can be achieved, and this lubricant is easily soluble in water, facilitating subsequent treatment. The selected natural organic acids have the characteristics of low corrosiveness, wide sources, health - harmlessness, and fully meet the environmental protection standards of green and pollution - free; while the metal alkaline compounds have the advantages of easy preparation and low cost.

[0007] To achieve the above object, the technical solution of the present invention is as follows:

[0008] An environmentally friendly superlubricating lubricant, wherein the lubricant is formed by mixing natural organic acids and metal alkaline compounds in a certain proportion and reacting. The natural organic acids refer to at least one of tartaric acid, lactic acid, succinic acid, malic acid, phytic acid, and oxalic acid, all in the form of solutions, and the concentration ratio ranges from 30% to 80%.

[0009] Preferably, the metal alkaline compounds refer to at least one of calcium hydroxide, lithium hydroxide, aluminum hydroxide, magnesium hydroxide, sodium carbonate, and potassium carbonate.

[0010] Preferably, the mass ratio of the metal alkaline compounds to the natural organic acids is between 1:1 and 1:30.

[0011] A preparation method of an environment-friendly super-lubricating lubricant includes the following steps: First, disperse a metal alkaline compound into a natural organic acid according to a certain ratio, and then ultrasonically treat and heat the mixed solution to make it react fully, thus obtaining a light yellow or dark yellow liquid lubricant.

[0012] Preferably, the ultrasonic time range is 60 - 90 minutes, and the ultrasonic frequency range is 10 - 50 KHz.

[0013] Preferably, the heating time range is 60 - 90 minutes, and the heating temperature range is 40 - 80 °C.

[0014] The beneficial effects of the environment-friendly super-lubricating lubricant and its preparation method of the present invention are as follows: The natural organic acid adopted in the present invention widely exists in various plants, and has the characteristics of non-toxic, environment-friendly and wide sources. It is not only safer for users, but also less polluting to the environment, and at the same time, the corrosion of the friction pair material is relatively slight. In addition, the selected metal alkaline compound has the advantages of low cost and easy availability. The innovation of the present invention lies in using the natural organic acid as the base lubricant, and the preparation process is simple and easy to implement, facilitating large-scale production. More importantly, this lubricating material has the characteristics of green environmental protection and easy degradation, can quickly enter the super-lubricating state, effectively shorten the running-in period, and thus greatly reduce the wear of the friction pair during the running-in process. The development of this technology greatly enriches the application system of liquid super-lubricating materials and provides new breakthroughs and ideas for practical applications. To sum up, the present invention has the following advantages: 1. The selected base lubricant is a natural organic compound, which will not cause corrosion to the friction pair material. This liquid lubricant is green environmental protection, easy to degrade, and will not pollute the environment. 2. Different from the traditional lubricant composed of acid and polyol, it has a certain degree of innovation. 3. The composition raw materials are easy to obtain, and the preparation method is simple. Brief Description of the Drawings

[0015] Figure 1 It is a schematic diagram of the lubricant provided by the present invention, where 1 is a natural organic acid and 2 is a metal alkaline compound;

[0016] Figure 2 It is a curve graph showing the change of the friction coefficient of the green lubricant provided by Example 9 with time;

[0017] Figure 3 It is a curve graph showing the change of the friction coefficient of the green lubricant provided by Example 10 with time;

[0018] Figure 4 It is a curve graph showing the change of the friction coefficient of the green lubricant provided by Example 11 with time. Detailed Description of the Embodiments

[0019] The following is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0020] The following embodiments can be understood as separately expressing a part of the local structure or method of the present invention, or can also be understood as the combination of embodiments explaining the connotation of a larger scope of the structure or method of the present invention.

[0021] Embodiment 1

[0022] An environmentally friendly super lubricating lubricant, as Figures 1-4 shown, the lubricant is formed by mixing and reacting natural organic acids and metal basic compounds in a certain proportion. The natural organic acids refer to at least one of tartaric acid, lactic acid, succinic acid, malic acid, phytic acid, and oxalic acid, all of which exist in the form of solutions. The concentration ratio of the natural organic acid relative to the lubricant ranges from 30%.

[0023] Embodiment 2

[0024] An environmentally friendly super lubricating lubricant, as Figures 1-4 shown, the lubricant is formed by mixing and reacting natural organic acids and metal basic compounds in a certain proportion. The natural organic acids refer to at least one of tartaric acid, lactic acid, succinic acid, malic acid, phytic acid, and oxalic acid, all of which exist in the form of solutions. The concentration ratio of the natural organic acid relative to the lubricant ranges from 80%.

[0025] Embodiment 3

[0026] Based on Embodiments 1 and 2, this embodiment discloses various specific embodiments of the metal basic compound:

[0027] The metal basic compound refers to (A1) calcium hydroxide; (A2) lithium hydroxide; (A3) aluminum hydroxide; (A4) magnesium hydroxide; (A5) sodium carbonate; (A6) potassium carbonate; where (A1)-(A6) are the numbers of specific embodiments. It can be understood that according to needs, one of the metal basic compounds can be selected, or several of the above metal basic compounds can be selected and mixed and reacted with the natural organic acid.

[0028] Embodiment 4

[0029] Based on Embodiment 3, this embodiment discloses that the mass ratio of the metal basic compound to the natural organic acid is 1:1.

[0030] Embodiment 5

[0031] Based on Embodiment 3, this embodiment discloses that the mass ratio of the metal basic compound to the natural organic acid is 1:30.

[0032] Example 6

[0033] Based on the above embodiments, this embodiment discloses a preparation method of an environment-friendly super lubricating lubricant, including the following steps: First, disperse the metal alkaline compound into the natural organic acid according to a certain ratio, and then ultrasonically treat and heat the mixed solution to make it react fully, thus obtaining a light yellow or dark yellow liquid lubricant.

[0034] Example 7

[0035] Based on Example 6, this embodiment discloses:

[0036] The ultrasonic time range is 60 minutes, and the ultrasonic frequency range is 10 KHz;

[0037] The heating time range is 60 minutes, and the heating temperature range is 40 °C.

[0038] Example 8

[0039] Based on Example 6, this embodiment discloses:

[0040] The ultrasonic time range is 90 minutes, and the ultrasonic frequency range is 50 KHz;

[0041] The heating time range is 90 minutes, and the heating temperature range is 80 °C.

[0042] Example 9

[0043] Add 1 g of sodium carbonate as an additive to 20 g of 60% oxalic acid solution. The mass ratio of the metal alkaline compound to the natural organic acid in the obtained mixed solution is 1:10. Then, ultrasonically heat and react this solution. The ultrasonic time is 60 minutes, the ultrasonic frequency is 30 kHz, the heating time is 70 minutes, and the heating temperature is set at 60 °C to ensure full reaction, and finally obtain a green liquid lubricant.

[0044] To test the tribological properties of the prepared green liquid lubricant, an experiment was carried out using a ball-on-disk tribometer (TRB, Anton Paar). The reciprocating friction mode was adopted in the experiment. The upper friction pair was a Si3N4 small ball with a diameter of 6 mm, and the lower friction pair was a SiO 2 wafer. Before the experiment, the friction pairs need to be immersed in ethanol and acetone solutions respectively and ultrasonically treated for 15 minutes to remove surface impurities. Then take out the friction pairs and dry them in an oven. The parameters for the experimental test are: load 3 N, frequency 3 Hz, amplitude 2 mm. According to the test results, the curve of the friction coefficient of the prepared green liquid lubricant changing with time between the friction pairs is as Figure 2As shown in the figure. It shows that after a running-in period of 715 seconds, the friction coefficient drops below 0.01, successfully achieving the superlubrication state and finally stabilizing at around 0.007.

[0045] Example 10

[0046] 1 g of lithium hydroxide was added as an additive to 30 g of a 70% succinic acid solution. In the resulting mixed solution, the mass ratio of the metal basic compound to the natural organic acid was 1:30. Subsequently, the solution was subjected to an ultrasonic heating reaction. The ultrasonic time was 70 minutes, the ultrasonic frequency was 40 kHz, the heating time was 80 minutes, and the heating temperature was set at 50 °C to ensure sufficient reaction, and finally a green liquid lubricant was obtained. To test the tribological properties of the prepared green liquid lubricant, an experiment was carried out using a ball-on-disk tribometer (TRB, Anton Paar). The reciprocating friction mode was adopted. The upper friction pair was a Si3N4 ball with a diameter of 6 mm, and the lower friction pair was a SiO 2 wafer. Before the experiment, the friction pairs were immersed in an ethanol and acetone solution and ultrasonically treated for 15 minutes to remove surface impurities. After treatment, the friction pairs were placed in an oven for drying. The test parameters of the experiment were: load 4 N, frequency 2 Hz, amplitude 2 mm. According to the test results, the curve of the friction coefficient between the friction pairs of the prepared green liquid lubricant changing with time is as Figure 3 shown. It shows that after a running-in period of 266 seconds, the friction coefficient drops below 0.01, successfully achieving the superlubrication state and finally stabilizing at around 0.007.

[0047] Example 11

[0048] 0.5 g of potassium carbonate was added as an additive to 5 g of a 50% phytic acid solution. In the resulting mixed solution, the mass ratio of the metal basic compound to the natural organic acid was 1:10. Subsequently, the solution was subjected to an ultrasonic heating reaction. The ultrasonic time was 50 minutes, the ultrasonic frequency was 20 kHz, the heating time was 60 minutes, and the heating temperature was set at 70 °C to ensure sufficient reaction, and finally a green liquid lubricant was obtained. To test the tribological properties of the prepared green liquid lubricant, an experiment was carried out using a ball-on-disk tribometer (TRB, Anton Paar). The reciprocating friction mode was adopted. The upper friction pair was a Si3N4 ball with a diameter of 6 mm, and the lower friction pair was a SiO 2 wafer. Before the experiment, the friction pairs needed to be immersed in an ethanol and acetone solution and ultrasonically treated for 15 minutes to remove surface impurities, and after treatment, they were placed in an oven for drying. The test parameters of the experiment were: load 1 N, frequency 3 Hz, amplitude 2 mm. According to the test results, the curve of the friction coefficient between the friction pairs of the prepared green liquid lubricant changing with time is as Figure 4As shown. The figure shows that after a running-in period of 535 seconds, the friction coefficient drops below 0.01, successfully achieving a superlubricated state and finally stabilizing at around 0.0065.

Claims

1. An environmentally friendly super-lubricant, characterized by: The lubricant is prepared by mixing a natural organic acid and a metal alkaline compound in a certain proportion. The natural organic acid refers to at least one of tartaric acid, lactic acid, succinic acid, malic acid, phytic acid, and oxalic acid, all of which are in the form of a solution with a concentration range of 30 to 80%.

2. An environmentally friendly super lubricant as claimed in claim 1, characterized in that: The metal alkaline compound refers to at least one of calcium hydroxide, lithium hydroxide, aluminum hydroxide, magnesium hydroxide, sodium carbonate and potassium carbonate.

3. An environmentally friendly super lubricant as claimed in claim 2, characterized in that: The mass ratio of the metal alkaline compound to the natural organic acid is between 1:1 and 1:

30.

4. A method for preparing an environmentally friendly super lubricant as claimed in claim 3, comprising the following steps: Firstly, the metal alkaline compound is dispersed in a natural organic acid in a certain proportion, and then the mixed solution is ultrasonicated and heated to make it fully react, so as to obtain a light yellow or dark yellow liquid lubricant.

5. The method for preparing an environmentally friendly super lubricant according to claim 4, characterized in that: The ultrasonic time range is 60 to 90 minutes, and the ultrasonic frequency range is 10 to 50 KHz.

6. The environmentally friendly super lubricant according to claim 4, characterized in that: The heating time ranges from 60 to 90 minutes, and the heating temperature ranges from 40 to 80°C.

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