CN115404115B

CN115404115B - Nano copper lubricating oil additive and preparation method thereof

Info

Publication number: CN115404115B
Application number: CN202211047345.3A
Authority: CN
Inventors: 张治军; 田路露; 牛利永; 李小红
Original assignee: Henan University
Current assignee: Henan University
Priority date: 2022-08-30
Filing date: 2022-08-30
Publication date: 2023-09-15
Anticipated expiration: 2042-08-30
Also published as: CN115404115A

Abstract

The invention belongs to the technical field of nano material preparation, and particularly relates to a nano copper lubricating oil additive and a preparation method thereof. The preparation method adopts a copper precursor without hetero atoms to prepare the nano copper lubricating oil additive in a lubricating oil medium by utilizing an in-situ surface modification technology. The preparation method realizes the in-situ and one-step preparation of the nano copper lubricating oil additive, has the characteristics of high yield and environmental protection, simplifies the application steps of nano copper, and improves the application universality of the nano copper lubricating oil additive.

Description

Nano copper lubricating oil additive and preparation method thereof

Technical Field

The invention belongs to the technical field of nano material preparation, and particularly relates to a nano copper lubricating oil additive and a preparation method thereof.

Background

In recent years, with the rapid development of advanced manufacturing industry, conventional lubricating materials have approached the limit of their use performance, and high-performance nano lubricating materials with unique properties have become one of research hotspots in the field of mechanical lubrication. Since 90 s of the last century, nano copper has been widely paid attention to by various scientists as a lubricating oil additive which exhibits excellent antifriction, antiwear, extreme pressure and wear self-repairing properties. However, pure nano copper powder cannot be used because of poor dispersibility and stability in lubricating oil. It is often desirable to surface modify the material during the preparation process to improve its dispersion stability.

In general, the preparation and surface modification of the nano copper are completed in a water-organic two-phase or water-phase medium, so as to obtain the oil-soluble nano copper with oleophilic surface. Chinese patent publication No. CN101200667B discloses a method for preparing oil-soluble nano-copper by surface modification, and the invention prepares the oil-soluble nano-copper in a water-organic two-phase system. The surface organic modification of the nano copper in the formation process is completed at the interface of the water phase and the organic phase, the reaction process is transferred from the water phase to the organic phase, the product stays in the organic phase, and the oil-soluble nano copper is obtained by separating the organic phase and carrying out reduced pressure distillation; the method has simple process and is suitable for large-scale production, but because a large amount of organic solvents are used in the reaction process, the danger is high, and a large amount of soluble salts exist in the water phase due to the addition of acid and alkali, the method is unfavorable for energy conservation and environmental protection. Chinese patent publication No. CN110744068B discloses an oil-soluble nano-copper and a preparation method thereof, and the invention prepares the oil-soluble nano-copper by adopting a precursor without hetero atoms in an aqueous phase system. The method has high process yield, high safety and environmental protection, and solves the problems of interface reaction, process safety and the like in the oil-soluble nano copper synthesis process; however, when the oil-soluble nano copper is used as a lubricating oil additive in a compounding way, the polarity difference of the lubricating oil and the oil-soluble nano copper can influence the dispersion state of the lubricating oil and the oil-soluble nano copper in the lubricating oil to generate a partial coagulation phenomenon, so that the functions of lubricating parts are influenced. Therefore, in the practical use process, other additives such as a viscosity index improver, a dispersing agent and the like are additionally added to maintain the stable dispersion of the oil-soluble nano copper in the lubricating oil.

Disclosure of Invention

In order to overcome the problems in the prior art, the invention provides a nano copper lubricating oil additive and a preparation method thereof. The preparation method is convenient and pollution-free, realizes the in-situ and one-step preparation of the nano copper lubricating oil additive, has the characteristics of high yield and environmental protection, simplifies the application steps of nano copper, and improves the application universality of the nano copper lubricating oil additive.

In order to achieve the above purpose, the technical scheme of the invention is as follows:

the preparation method of the nano copper lubricating oil additive comprises the following steps:

1) Stirring lubricating oil and a copper modifier at 25-85 ℃ for 10-60min until uniformly mixed to obtain a composite reaction solvent;

2) Stirring and reacting the copper precursor and the composite reaction solvent for 0.5-5h at 25-85 ℃ to obtain a suspended copper mixed solution;

3) Regulating the pH value of the suspended copper mixed solution in the step 2) to 7-9, and adding a reducing agent at 25-85 ℃ for reduction reaction for 0.5-24 hours to obtain nano copper lubricating oil emulsion;

4) And 3) reducing the temperature of the nano copper lubricating oil emulsion obtained in the step 3) to below 40 ℃ after reduced pressure distillation, adding a small amount of antioxidant, and stirring uniformly to obtain the nano copper lubricating oil additive.

Specifically, the lubricating oil in the step 1) is one of synthetic oil, mineral oil, compound oil and the like; the mass ratio of the copper modifier to the lubricating oil is 1 (0.1-5).

Further preferably, the synthetic oil is one of poly alpha-olefin, dioctyl sebacate, diisooctyl cyclohexane dicarboxylate, etc.; the mineral oil is liquid paraffin; the compound oil consists of base oil, dispersing agent and detergent in the mass ratio of (2-8) to (1-4).

Further, the dispersant in the compound oil is one of mono alkenyl succinimide, di alkenyl succinimide, multi alkenyl succinimide, polyisobutylene succinimide and the like; the detergent is sulfonate detergent, for example, can be one of synthetic calcium sulfonate with high, medium and low base numbers, petroleum calcium sulfonate and the like; the base oil is one of liquid paraffin, poly alpha-olefin, dioctyl sebacate, diisooctyl cyclohexane dicarboxylate, etc.

In the invention, synthetic calcium sulfonate and petroleum calcium sulfonate with high, medium and low base numbers are all from commercial market, and the base number range of the product is: low base number: 20-35mgKOH/g, medium base number: not less than 145mgKOH/g, high base number: more than or equal to 295 mgKOH/g.

Specifically, the copper modifier in the step 1) is one or more of aliphatic carboxylic acid, alkyl primary amine, alkyl secondary amine, alkyl tertiary amine, dialkyl dithiophosphoric acid, N-dialkyl dithiocarbamic acid, naphthenic acid, alkyl phosphoric acid and the like, and the carbon number of the alkyl is 4-18. For example, dioctyl dithiophosphoric acid, diisooctyl dithiophosphoric acid, N-diisobutyl dithiocarbamic acid, di (2-ethyl-hexyl) phosphoric acid (also called P204, which is a widely used industrial extractant), oleic acid, oleylamine, di-N-butylamine, tri-Xin Guiwan-tertiary amine, etc. can be mentioned.

Further, in the step 2), the copper precursor is one or more of copper oxide, cuprous oxide, copper hydroxide, basic copper carbonate and the like; the concentration of the copper precursor in the suspension copper mixed solution is 1-4mol/L.

Specifically, the reducing agent in the step 3) is one or more of hydrazine hydrate, formaldehyde, ethylene glycol, formic acid and the like. In the step 3), one of ammonia water, short carbon chain organic primary amine, secondary amine (C1-4), glacial acetic acid and the like can be adopted to adjust the pH value of the suspended copper mixed solution to 7-9, the mass concentration of the ammonia water is 25-28%, and the content of the short carbon chain organic primary amine, the secondary amine and the glacial acetic acid is 99% or more.

Further preferably, the ratio of the amounts of the copper precursor, the reducing agent and the copper modifier is 1 (0.5-5): 0.3-3.

Specifically, the antioxidant in the step 4) is one of zinc thiophosphoryl phenol, zinc thiophosphoryl butyl octyl, zinc thiophosphoryl dioctyl basic zinc, zinc thiophosphoryl dialkyl, di-tert-butyl-p-cresol, di-tert-butyl-mixed phenol and the like; the mass ratio of the antioxidant to the nano copper lubricating oil additive is (0.01-0.05): 1.. The di-tert-butyl mixed phenol is fully named as 2, 6-di-tert-butyl mixed phenol, has the trade code of T502A in the lubricating oil industry and is a mixed shielding phenol antioxidant.

The invention also provides the nano copper lubricating oil additive prepared by the method.

The invention adopts copper precursor without hetero atom, and directly prepares nano copper lubricating oil additive in lubricating oil medium by in-situ surface modification technology in one step under the condition of no external solvent. The invention is a convenient and pollution-free in-situ preparation method. The invention uses the lubricating oil of the target application system as a reaction medium and a dispersion medium, the prepared nano copper lubricating additive is uniform and stable and is similar to a homogeneous system, and the nano copper lubricating additive is directly added into the lubricating oil when in application, which is the same as or similar to the natural property of the lubricating oil used in the actual working condition, without other adjustment of the application working condition. The method and the research and development of the product have important practical value and significance from the viewpoints of economy, environmental friendliness, application convenience and the like. Compared with the prior art, the invention has the following beneficial effects:

1) The invention has no external solvent, the reaction system only contains a small amount of water generated by the synthesis reaction, and the product is obtained by directly concentrating after the preparation is finished, thus greatly improving the yield of the product;

2) The invention takes lubricating oil as a reaction medium and a disperse phase, and copper nano particles in a target product are uniformly dispersed in the lubricating oil;

3) The properties such as the viscosity of the nano copper lubricating oil additive prepared by the invention can be adjusted through the proportion change among the components of the compound oil, so that the nano copper lubricating oil additive is basically consistent with the inherent properties of the lubricating oil used in the target application lubrication working condition, and the application universality is enlarged;

4) The method has the advantages of no three wastes in the reaction process, no conventional organic solvent as a reaction medium, simple production process, safety and environmental protection, and suitability for large-scale industrial production.

Drawings

FIG. 1 is a transmission electron micrograph of nano-copper contained in the nano-copper lubricant additive prepared in example 1 after washing with acetone; from the graph, the size of the copper nano particles is 5-10nm, the average particle diameter is 8nm, and the monodispersity of the particles is good;

fig. 2 is an optical photograph of the nano copper lubricant additive prepared in example 1 dispersed in an organic solvent, the oil-soluble nano copper additive amount is 1wt% and 2wt%, the solvent is in order from left to right: petroleum ether, xylene; as can be seen from the figure, the nano copper lubricating additive has good dispersion stability in various organic solvents;

FIG. 3 is a four-ball friction wear test result of the nano-copper lubricating oil additive prepared in example 1 applied to finished oil Compton gasoline (10W-40); KPD is Compton gasoline engine oil, DNCu-0.5wt% is Compton gasoline engine oil added with 0.5wt% of the nano copper lubricating oil additive prepared in the embodiment; in the figure, the a test temperature is 120 ℃, where WSD represents the plaque diameter and COF represents the coefficient of friction; the test temperatures of B and C are 75 ℃ and 120 ℃ respectively;

FIG. 4 is an optical photograph showing color change during reduction reaction of nano copper lubricant additive prepared in example 2 and the state of the product before and after distillation;

fig. 5 is a transmission electron micrograph of nano-copper contained in the nano-copper lubricant additive prepared in example 3 after washing with acetone.

Detailed Description

The present invention will be described in further detail with reference to examples, but the scope of the present invention is not limited thereto.

In the following examples, unless otherwise specified, all materials used were commercially available products which were commercially available as they are. For example, detergents such as high base number petroleum calcium sulfonate, medium base number synthetic calcium sulfonate, dispersants such as mono alkenyl succinimide, and antioxidants such as phosphorus disulfide dialkyl zinc salt are purchased from new materials, inc. of New Country Ruifeng; copper modifiers such as N, N-diisobutyldithiocarbamic acid are purchased from He's wall Yuan Hao New Material Co. Diisooctyl dithiophosphoric acid and N, N-diisobutyl dithiocarbamic acid are all synthetic intermediates of the corresponding zinc salts and can be directly purchased.

Example 1

The preparation method of the nano copper lubricating oil additive specifically comprises the following steps:

1) 27g (0.076 mol) of copper modifier dioctyl dithiophosphoric acid and 27g of lubricant dioctyl sebacate are weighed into a 250mL three-port bottle, and stirred for 30min at the constant temperature of 50 ℃ until being uniformly mixed, thus obtaining yellowish green liquid (namely a compound reaction solvent);

2) 7.84g (0.08 mol) copper hydroxide is added into the composite reaction solvent, the stirring reaction is carried out for 60min at 50 ℃, the solution is changed from light yellow green to yellow green turbid liquid (namely, suspension copper mixed liquid, the concentration of copper precursor is about 1.48 mol/L), and the pH value of the turbid liquid is 9 at the moment without adjusting the pH value;

3) Weighing 5.06g of hydrazine hydrate (the mass concentration is 80%,0.08 mol) and slowly adding the hydrazine hydrate into a three-neck flask under stirring, carrying out reduction reaction at 50 ℃ for 2 hours, and then raising the temperature to 80 ℃ for reaction for 1 hour to obtain orange-brown reaction liquid (namely nano copper lubricating oil emulsion);

4) And (3) reducing the pressure and distilling the reaction liquid, cooling to 40 ℃, adding 0.6g of di-tert-butyl mixed phenol antioxidant, and uniformly stirring to obtain the nano copper lubricating oil additive.

The total volume of the reaction system was about 75mL, the yield of the nano-copper lubricating oil additive was 59g (about 62 mL), and the product volume was about 82% of the total volume of the reaction. The particle size of the nano copper is 5-10nm, the transmission electron micrograph is shown in figure 1, the dispersibility of the obtained nano copper lubricating oil additive in an organic solvent is shown in figure 2 (petroleum ether and dimethylbenzene are sequentially added in the organic solvent from left to right, and the addition amount of the oil-soluble nano copper is respectively 1 weight percent and 2 weight percent). As can be seen from fig. 1-2: the obtained oil-soluble nano copper has small and uniform particle size and good dispersion stability.

FIG. 3 shows the four-ball friction and wear test results of the nano-copper lubricating oil additive prepared in example 1 applied to the finished oil Compton motor oil (10W-40). As can be seen from the figure: the addition of the nano copper lubricating oil additive reduces the friction coefficient and the abrasive spot diameter of the Compton gasoline engine oil at different service temperatures, namely improves the lubricating performance of the Compton gasoline engine oil, wherein the 0.5 weight percent of the additive has excellent antifriction and antiwear performances.

Example 2

1) Weighing 12.5g of polyisobutylene succinimide, 12.5g of high-base-number petroleum calcium sulfonate and 25g of dioctyl sebacate in a 250mL three-necked flask, and stirring at a constant temperature of 60 ℃ for 10min to obtain dark reddish brown compound oil; 28.3g (0.08 mol) of diisooctyl dithiophosphoric acid is added into the compound oil and stirred at 60 ℃ for 30min until the mixture is uniformly mixed, thus obtaining a compound reaction solvent;

2) 7.84g (0.08 mol) copper hydroxide is added into the composite reaction solvent, and the mixture is stirred and reacted for 2 hours at 60 ℃ to form dark green near-black suspension (namely suspension copper mixed solution, wherein the concentration of copper precursor is about 1.02 mol/L);

3) Adjusting the pH value to 8 by glacial acetic acid, slowly adding 5.06g of hydrazine hydrate (the mass concentration is 80 percent, and 0.08 mol) into a three-neck flask under stirring, reacting at 60 ℃ for 1h, then heating to 70 ℃ for 1h, and then heating to 80 ℃ for 2h to obtain brown orange reaction liquid (namely nano copper lubricating oil emulsion);

4) And (3) reducing the pressure and distilling the reaction liquid, cooling to 40 ℃, adding 0.85g of di-tert-butyl-p-cresol antioxidant, and uniformly stirring to obtain the nano copper lubricating oil additive. The total volume of the reaction system was about 95mL, the yield of the nano copper lubricating oil additive was 83.4g (about 90 mL), and the product volume was about 94% of the total volume of the reaction.

In this example, the color change during the reduction reaction is shown in FIG. 4, and the color of the dark green near-black suspension of the copper-containing precursor is changed from near-black, brown, yellow, brown orange in sequence after reduction; the dark reddish brown nano copper lubricating oil additive is obtained after distillation, the volume change of the product before and after distillation is smaller, and the higher yield of the product is indicated.

Example 3

1) Weighing 20g of liquid paraffin and 36.7mL (32.8 g) of N, N-diisobutyl dithiocarbamic acid (0.16 mol) in a 250mL three-mouth bottle, and stirring at 25 ℃ for 10min to uniformly mix to obtain a compound reaction solvent;

2) Weighing 8.0g (0.1 mol) of copper oxide, adding the copper oxide into the composite reaction solvent, and stirring the mixture for 3 hours at 25 ℃ to obtain brown green oily turbid liquid (namely suspension copper mixed liquid, wherein the concentration of a copper precursor is about 1.78 mol/L);

3) Maintaining the temperature at 25 ℃, adding ammonia water under stirring to adjust the pH to 8, dripping 11.68g of hydrazine hydrate (the mass concentration is 30 percent, 0.07 mol), stirring for 3 hours, heating to 80 ℃ for reaction for 1 hour, and obtaining dark reddish brown reaction liquid (namely nano copper lubricating oil emulsion);

4) And (3) reducing the pressure, distilling the reaction liquid, cooling to 40 ℃, adding 1.3g of di-tert-butyl mixed phenol antioxidant, and stirring and mixing uniformly to obtain the nano copper lubricating oil additive. The total volume of the reaction system was about 75mL, the yield of the nano-copper lubricating oil additive was 59g (about 60 mL), and the product volume ratio was about 80%.

FIG. 5 shows a transmission electron micrograph of the nano-copper contained in the nano-copper lubricating additive prepared in example 3 after washing with acetone; as can be seen from the figure, the copper nanoparticles have a size of 8 to 20nm, an average particle diameter of 15nm, and good dispersibility.

Example 4

1) 15g of poly alpha-olefin (PAO 6) and 33.5mL (29.8 g) of di (2-ethyl-hexyl) phosphoric acid (0.1 mol) are weighed into a 250mL three-mouth bottle, and stirred for 30min at 40 ℃ to be uniformly mixed, so as to obtain a composite reaction solvent;

2) Weighing 4.0g (0.05 mol) of copper oxide and 7.2g (0.05 mol) of cuprous oxide, adding into a composite reaction solvent, stirring at 40 ℃ for 30min, heating to 60 ℃ and stirring for 30min to obtain a suspended copper mixed solution, wherein the concentration of a copper precursor is about 2.08 mol/L;

3) Keeping the temperature at 60 ℃, adding ethylamine to adjust the pH value of the reaction liquid to 8 under stirring, dripping 12.5g of hydrazine hydrate (the mass concentration is 80 percent, 0.2 mol), and stirring and reacting for 5 hours to obtain dark reddish brown reaction liquid (namely nano copper lubricating oil emulsion);

4) And (3) reducing the pressure, distilling the reaction liquid, cooling to 40 ℃, adding 0.56g of phosphorus-sulfur bisoctylprimary alkyl zinc salt (T203) antioxidant, and stirring and mixing uniformly to obtain the nano copper lubricating oil additive. The total volume of the reaction system is about 75mL, the yield of the nano copper lubricating oil additive is 51g (about 52 mL), and the volume ratio of the product is about 69%.

Example 5

1) 30g of dioctyl sebacate, 35.4g (0.1 mol) of diisooctyl dithiophosphoric acid and 14.1g (0.05 mol) of oleic acid are weighed into a 250mL three-neck flask, and stirred at 50 ℃ for 50min to be uniformly mixed, so as to obtain a composite reaction solvent;

2) Weighing 8.84g (0.04 mol) of basic copper carbonate and 8.46g (0.06 mol) of cuprous oxide, adding into a composite reaction solvent, and stirring at 50 ℃ for 1h to form green viscous liquid (namely suspension copper mixed liquid, wherein the concentration of copper precursor is about 1.25 mol/L);

3) Keeping the temperature at 50 ℃, adding diethylamine under stirring to adjust the pH value of the reaction solution to 9, dropwise adding 18.77g of hydrazine hydrate (the mass concentration is 80 percent, 0.3 mol) under stirring, heating to 80 ℃ after stirring for 1h, and reacting for 5h to obtain reddish brown reaction solution (namely nano copper lubricating oil emulsion);

4) And (3) reducing the pressure and distilling the reaction liquid, cooling to 40 ℃, adding 2.5g of di-tert-butyl mixed phenol antioxidant, and uniformly stirring to obtain the nano copper lubricating oil additive. The total volume of the reaction system is about 147mL, the yield of the nano copper lubricating oil additive is 105g (about 110 mL), and the volume ratio of the product is about 75%.

Example 6

The preparation method of the nano copper lubricating oil additive specifically comprises the following steps: 1) Weighing 10g of dienyl succinimide, 20g of medium-base number synthetic calcium sulfonate and 30g of cyclohexane dicarboxylic acid diisooctyl ester in a 250mL three-necked bottle, and stirring at a constant temperature of 65 ℃ for 1h to obtain brown compound oil; adding 14.1g (0.05 mol) of oleic acid and 13.4g (0.05 mol) of oleylamine into the compound oil, and stirring at 65 ℃ for 30min until the mixture is uniform, thus obtaining a compound reaction solvent;

2) Adding 14.7g (0.15 mol) of copper hydroxide into the composite reaction solvent, and keeping the temperature of 65 ℃ to stir and react for 1h to form green suspension (namely suspension copper mixed solution);

3) After the pH value of the reaction system was adjusted to 8 with ethylamine under stirring, the temperature was raised to 80 ℃. Taking 37.5g of hydrazine hydrate (the mass concentration is 60 percent, 0.45 mol) and slowly adding the hydrazine hydrate into a three-port burner under stirring, and keeping the temperature of 80 ℃ for reaction for 3 hours to obtain dark orange reaction liquid (namely nano copper lubricating oil emulsion);

4) And (3) reducing the pressure, distilling the reaction liquid, cooling to 40 ℃, adding 3.5g of di-tert-butyl-p-cresol antioxidant, and uniformly stirring to obtain the nano copper lubricating oil additive. The total volume of the reaction system is about 145mL, the yield of the nano copper lubricating oil additive is 97g (95 mL), and the volume of the product accounts for 65 percent.

Example 7

1) 10g of dioctyl sebacate, 7.4g (0.02 mol) of tertiary amine with copper modifier three Xin Guiwan groups, 5.4g (0.03 mol) of naphthenic acid and 35.3g (0.1 mol) of diisooctyl dithiophosphoric acid are weighed into a 250mL three-mouth bottle, and stirred at 65 ℃ for 1h until the mixture is uniformly mixed to obtain a compound reaction solvent;

2) Adding 9.8g (0.1 mol) of copper hydroxide into the composite reaction solvent, and keeping the temperature of 65 ℃ to stir and react for 1h to form dark green suspension (namely suspension copper mixed solution);

3) Adjusting the pH value of a reaction system to 9 by adopting ammonia water under the stirring state, slowly adding 6.33g of hydrazine hydrate (the mass concentration is 80 percent and 0.1 mol) into a three-mouth bottle under the stirring, keeping the temperature of 60 ℃ for 2 hours, and then heating to 80 ℃ for 2 hours to obtain brown reaction liquid (namely nano copper lubricating oil emulsion);

4) And (3) reducing the pressure and distilling the reaction liquid, cooling to 40 ℃, adding 1.3g of phosphorus-sulfur dialkyl zinc salt antioxidant, and uniformly stirring to obtain the nano copper lubricating oil additive. The total volume of the reaction system is about 85mL, the yield of the nano copper lubricating oil additive is 64.5g (65 mL), and the volume of the product accounts for 76%.

Claims

1. The preparation method of the nano copper lubricating oil additive is characterized by comprising the following steps of:

1) Stirring and uniformly mixing lubricating oil and a copper modifier at 25-85 ℃ to obtain a composite reaction solvent;

4) Reducing the temperature of the nano copper lubricating oil emulsion obtained in the step 3) to below 40 ℃ after reduced pressure distillation, adding an antioxidant, and uniformly stirring to obtain a nano copper lubricating oil additive;

the lubricating oil in the step 1) is compound oil;

the compound oil consists of base oil, dispersing agent and detergent in the mass ratio of (2-8) to (1-4);

the dispersant in the compound oil is one of mono alkenyl succinimide, bis alkenyl succinimide, poly alkenyl succinimide and polyisobutylene succinimide; the detergent is sulfonate detergent; the base oil is one of dioctyl sebacate and diisooctyl cyclohexane dicarboxylate;

the copper modifier in the step 1) is one or more of aliphatic carboxylic acid, alkyl primary amine, alkyl secondary amine, alkyl tertiary amine, dialkyl dithiophosphoric acid, N-dialkyl dithiocarbamic acid, naphthenic acid and alkyl phosphoric acid, and the carbon number of the alkyl is 4-18;

the copper precursor in the step 2) is one or more of copper oxide, cuprous oxide, copper hydroxide and basic copper carbonate; the concentration of the copper precursor in the suspension copper mixed solution is 1-4mol/L.

2. The method for preparing the nano copper lubricating oil additive according to claim 1, wherein the mass ratio of the copper modifier to the lubricating oil is 1 (0.1-5).

3. The method for preparing nano copper lubricating oil additive according to claim 1, wherein the reducing agent in the step 3) is one or more of hydrazine hydrate, formaldehyde, ethylene glycol and formic acid.

4. The method for preparing nano copper lubricating oil additive according to claim 3, wherein the ratio of the amounts of the copper precursor, the reducing agent and the copper modifier is 1 (0.5-5): 0.3-3.

5. The method for preparing the nano copper lubricating oil additive according to claim 1, wherein the antioxidant in the step 4) is one of zinc thiophosphoryl phenol, zinc thiophosphoryl butyl octyl, zinc thiophosphoryl dioctyl basic zinc, zinc thiophosphoryl dialkyl, di-tert-butyl-p-cresol and di-tert-butyl mixed phenol; the mass ratio of the antioxidant to the nano copper lubricating oil additive is (0.01-0.05): 1.

6. a nano-copper lubricating oil additive prepared by the method of any one of claims 1-5.