Environment-friendly cutting lubricating oil and preparation method thereof

Abstract

The present application relates to the field of lubricating oil, and particularly relates to an environment-friendly cutting lubricating oil and a preparation method thereof, which comprises the following components in parts by mass: 50-100 parts of base oil, 1-10 parts of phosphate ester ammonium salt, 6-22 parts of sulfur-based extreme pressure anti-wear agent, and 1-5 parts of nitrogen-doped carbon-coated lanthanum borate.The cutting lubricating oil has good lubricating performance, wear resistance and safety performance, is environment-friendly, can self-repair micro cracks generated during cutting of the base body, and has good compatibility of components.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lubricating oil, in particular to an environmentally friendly cutting lubricating oil and a preparation method thereof. BACKGROUND

[0002] Early researchers tracked the impact of various mechanical process oil on the health of operators and proposed many detailed research reports on the impact of different additives on human or animal physiology and the ecological environment, believing that aromatics, nitrite, and phenols have a serious irritating effect on the skin and are prone to induce cancer; some additives are difficult to biodegrade and can cause serious pollution to water bodies and the atmosphere. The use of obviously toxic and harmful additives in mechanical process oil has been completely banned, and additives or surfactants that have potential hazards to the ecological environment have gradually been limited or eliminated, so that high-efficiency environmentally friendly green mechanical process oil has emerged as the times require.

[0003] As mechanical process oil, cutting lubricating oil not only lubricates and cools workpieces and tools, but also lubricates workpiece support seats, so new requirements are put forward for the lubricity and viscosity of cutting oil. The cutting fluid used in machining centers not only has good lubrication and rust prevention effects on workpieces and tools, but also has good lubrication and rust prevention effects on equipment and tool libraries.

[0004] Patent No. CN102876435A discloses a semi-synthetic metal cutting fluid with trimethylolpropane oleate as base oil and a preparation method thereof. The cutting fluid uses trimethylolpropane oleate, non-ionic surfactant, anionic surfactant, rust inhibitor, cosolvent, extreme pressure agent, defoamer, bactericide, and water as raw materials, has good lubricity and biodegradability, and is low-hazard to the human body and the environment. However, the cutting fluid uses a large amount of surfactant, which is high in cost and still toxic to the environment, and in addition, the use of sodium benzoate in the component can also be toxic to water bodies.

[0005] For example, patent No. CN112662458A discloses a high-temperature alloy cutting oil and a preparation method thereof. The cutting fluid is prepared from base oil (including 150N base oil and 60N base oil), oiliness agent, lubricating extreme pressure agent (a mixture of sulfurized fatty acid ester and sulfurized olefin), rust inhibitor, and stabilizer, and has excellent lubricity, extreme pressure, rust resistance, cooling, and stability. However, most of the raw materials selected for the cutting oil have poor biodegradability, which has a certain burden on the environment after discharge.

[0006] Therefore, it is urgent to develop a cutting lubricating oil with good lubricity, wear resistance, and safety, and friendly to the environment. SUMMARY

[0007] The present application aims to provide an environmentally friendly cutting lubricating oil and a preparation method thereof, which has good lubricating performance, wear resistance and safety performance, is friendly to the environment, can self-repair micro-cracks generated during cutting of the base body, and has good compatibility of components.

[0008] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0009] The present application provides an environmentally friendly cutting lubricating oil, which comprises the following components in parts by mass: 50-100 parts of base oil, 1-10 parts of phosphate ester ammonium salt, 6-22 parts of sulfur-based extreme pressure anti-wear agent, and 1-5 parts of nitrogen-doped carbon-coated lanthanum borate.

[0010] In some embodiments, the base oil is one or more of trimethylolpropane oleate, pentaerythritol oleate, dipentaerythritol ester, isooctyl oleate, isooctyl stearate, neopentyl glycol oleate, and diisooctyl adipate.

[0011] In some embodiments, the sulfur-based extreme pressure anti-wear agent comprises sulfurized lard and sulfurized fatty acid ester in a mass ratio of 1:(1-1.2).

[0012] In some embodiments, the preparation method of the nitrogen-doped carbon-coated lanthanum borate comprises the following steps:

[0013] S1, mix cardanol glycidyl ether and auxiliary carbon source, add to an ethanol solution, then add citric acid, heat to 70-80 DEG C, constant temperature stirring for 3-5 h, reduce pressure concentration, freeze-drying to obtain activated carbon source;

[0014] S2, mix lanthanum nitrate and boric acid, add polyethylene glycol, heat to 170-190 DEG C, constant temperature stirring for 11-13 h, centrifugation, washing, to obtain lanthanum borate particles;

[0015] S3, soak the lanthanum borate particles in step S2 in a sodium hydroxide solution, heat to 55-65 DEG C, ultrasonic treatment for 20-40 min, then filter and dry to obtain activated lanthanum borate particles;

[0016] S4, mix the activated lanthanum borate particles in step S3 with the activated carbon source in step S1, add ethanol, ball mill at a rotation speed of 250-350 rpm for 4-7 h, then heat to 150-250 DEG C at a heating rate of 2-5 DEG C / min, and keep the temperature for 0.5-1.5 h, then fill with inert protective gas, heat to 250-350 DEG C, and keep the temperature for 1-4 h to obtain pre-treated carbon-coated lanthanum borate;

[0017] S5, under the inert protective gas atmosphere, the pretreated carbon-coated lanthanum borate in step S4 is heated to 300-350℃ for 20-40 min, then heated to 450-550℃ for 20-30 min under the ammonia and inert protective gas atmosphere, and then heated to 500-700℃ for 10-30 min, to obtain nitrogen-doped carbon-coated lanthanum borate.

[0018] The applicant found in the research that the borate has good extreme pressure and wear resistance, has good biodegradability, the addition of lanthanum can improve the viscosity and stability of the lubricating oil, and enhance the oil film strength to help reduce friction and wear, and the lanthanum compound can improve the extreme pressure performance of the lubricant, so that it can still maintain good lubricating effect under high load conditions, and reduce the direct contact between metal surfaces. However, although lanthanum borate has many advantages described above, its dispersion performance in the system is poor, which seriously affects the normal use of the cutting lubricating oil.

[0019] The nitrogen-doped carbon-coated lanthanum borate prepared in the application not only solves the dispersion problem, but also has good biodegradability after modification. At the same time, the nitrogen-doped carbon-coated lanthanum borate can also play a role in repairing the micro-cracks of the substrate, and improve the lubricating performance of the cutting lubricating oil and reduce the friction coefficient. The reasons may be as follows: first, the nitrogen-doped carbon-coated lanthanum borate will form pyridine nitrogen-graphite nitrogen and part of C-N bonds in the preparation process, change the electron distribution of the nitrogen-doped carbon-coated lanthanum borate, form an electron-rich region on the surface, reduce the exposure of polar groups (such as -OH, -COOH), and thus improve the dispersion performance of the nitrogen-doped carbon-coated lanthanum borate; second, the active sites of pyridine nitrogen-graphite nitrogen formed in the nitrogen-doped carbon layer can release nitrogen-containing small molecules under the trigger of friction heat, react with lanthanum borate to generate in-situ boron nitride lubricating film and boron nitride to repair the micro-cracks of the substrate surface and reduce the wear of the substrate; third, the outer coating material of the nitrogen-doped carbon-coated lanthanum borate is selected to be more environmentally friendly cashew phenol glycidyl ether and biodegradable natural auxiliary carbon source, which is more friendly to the environment; fourth, the cashew phenol glycidyl ether structure contains a large number of epoxy groups, one part of which can cross-link to form a three-dimensional network structure during carbonization, and the remaining epoxy groups are wrapped in the rigid structure skeleton to prevent decomposition; second, the epoxy groups in the carbonized cashew phenol glycidyl ether will be adsorbed on the metal surface, and the non-polar region on the outside will be arranged vertically with the long alkyl chain of the base oil through van der Waals force to form a molecular brush structure, further reducing the contact area between the two friction surfaces. In addition, in the shearing process, the flexibility of the molecular brush layer can make the top end elastically bend, and the molecular brush layer slips preferentially, further dissipating the mechanical properties and reducing the friction coefficient.

[0020] In some embodiments, the auxiliary carbon source is chitosan or catechin.

[0021] In some embodiments, in step S1, the mass ratio of the cardanol glycidyl ether and the auxiliary carbon source is 1:(0.1-0.5).

[0022] Preferably, in step S1, the mass ratio of the cardanol glycidyl ether and the auxiliary carbon source is 1:0.3.

[0023] The present application can prevent the accumulation of a thick carbon layer caused by excessive cross-linking density of the cardanol glycidyl ether and the auxiliary carbon source, thereby increasing the particle size of the nitrogen-doped carbon-coated lanthanum borate and reducing the specific surface area, so that the cutting lubricating oil cannot be uniformly adsorbed on the surface of the tool and the workpiece to form a discontinuous lubricating film, thereby reducing the lubricating performance, and the risk of wear of the substrate can also be avoided.

[0024] In some embodiments, in step S1, the amount of citric acid is 0.2-0.8% of the total mass of the cardanol glycidyl ether and the auxiliary carbon source.

[0025] In some embodiments, in step S2, the mass ratio of the lanthanum nitrate and the boric acid is 1:(0.2-0.4).

[0026] In some embodiments, in step S2, the mass of the polyethylene glycol is 1.2-1.8% of the total mass of the lanthanum nitrate and the boric acid.

[0027] In some embodiments, in step S4, the mass ratio of the activated lanthanum borate particles and the activated carbon source is 1:(1.5-2.5).

[0028] In some embodiments, in step S5, the volume ratio of the ammonia gas and the inert protective gas is 1:(8-13).

[0029] Another aspect of the present application provides a preparation method of an environmentally friendly cutting lubricating oil, comprising the following steps: mixing base oil, phosphate ester ammonium salt, sulfur-based extreme pressure anti-wear agent and nitrogen-doped carbon-coated lanthanum borate, heating to 70-90 DEG C, and constant temperature stirring for 35-50 min to obtain the environmentally friendly cutting lubricating oil.

[0030] Compared with the prior art, the present application has the following beneficial effects:

[0031] (1) The cutting lubricating oil of the present application is prepared using base oil, phosphate ester ammonium salt, sulfur-based extreme pressure anti-wear agent and nitrogen-doped carbon-coated lanthanum borate as main raw materials, and has good lubricating performance, wear resistance and safety performance, is environmentally friendly, can self-repair micro-cracks generated during cutting of the substrate, and has good compatibility of the components of the cutting lubricating oil.

[0032] (2) The nitrogen-doped carbon-coated lanthanum borate of the present application is suitable for the cutting fluid system of the present application, has good dispersibility in the system, and can also repair the micro-cracks of the substrate, improve the lubricating performance of the cutting lubricating oil, and reduce the friction coefficient. DETAILED DESCRIPTION

[0033] Various exemplary embodiments of the present application will now be described in detail, which should be considered in a descriptive sense only and not for purposes of limitation to the present application. Rather, understand that the present description is made in terms of certain aspects, features, and embodiments of the present application for illustrative purposes only.

[0034] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. Additionally, for the purposes of the present application, ranges of values are understood to be "open-ended" ranges, unless otherwise stated. For example, a range of "between A and B" is understood to include the individual endpoints A and B, as well as any other number or individual endpoint within the range. Similarly, a range of "from about A to about B" is understood to include individual endpoints A and B, as well as any other number or individual endpoint within the range. The use of "about" or "approximately" in connection with a value Kapplies to the "open-ended" range.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. It will be apparent to those skilled in the art that many modifications and variations can be made to the specific embodiments of the present application without departing from the spirit or scope of the application. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. Various embodiments of the application are presented by way of example only and are not intended to limit the scope of the application as expressed by the appended claims. It is intended that the specification and examples be considered as exemplary only, with the true scope of the application being indicated by the following claims.

[0036] In the following preparation examples, examples and comparative examples, polyethylene glycol CAS No. 25322-68-3 was purchased from Jinan Daorong Chemical Co., Ltd.; and ammonium phosphate ester was purchased from Luoyang Taipingyan United Petroleum Chemical Co., Ltd.

[0037] Preparation Example 1

[0038] The preparation method of the nitrogen-doped carbon-coated lanthanum borate comprises the following steps:

[0039] S1, 30 g of cashew phenol glycidyl ether and 9 g of catechin were mixed and added to 500 mL of 50 wt% ethanol solution, 0.23 g of citric acid was added, the temperature was raised to 75°C, constant temperature stirring was carried out for 4 h, vacuum concentration was carried out, and freeze-drying was carried out to obtain an activated carbon source;

[0040] S2, 20 g of lanthanum nitrate and 6 g of boric acid were mixed, 0.4 g of polyethylene glycol was added, heated to 180℃, constant temperature stirring for 12 h, centrifuged, washed, to obtain lanthanum borate particles;

[0041] S3, 20 g of lanthanum borate particles in step S2 were soaked in 300 mL of 5wt% sodium hydroxide solution, heated to 60℃, ultrasonic treatment for 30 min, then filtered, dried, to obtain activated lanthanum borate particles;

[0042] S4, 20 g of activated lanthanum borate particles in step S3 were mixed with 40 g of activated carbon source in step S1, 60 mL of ethanol was added, ball milling at 300 rpm for 5 h, then taken out, heated to 200℃ at a heating rate of 3℃ / min, then argon was filled, heated to 300℃, and kept for 2 h, to obtain pre-treated carbon-coated lanthanum borate;

[0043] S5, the pre-treated carbon-coated lanthanum borate in step S4 was heated to 320℃ under argon atmosphere for 30 min, then heated to 500℃ under ammonia and argon atmosphere for 25 min, and then heated to 600℃ for 20 min, to obtain nitrogen-doped carbon-coated lanthanum borate.

[0044] Preparation Example 2

[0045] The preparation method of nitrogen-doped carbon-coated lanthanum borate is the same as that of Preparation Example 1, except that the mass of catechin used is 17 g.

[0046] Preparation Example 3

[0047] The preparation method of nitrogen-doped carbon-coated lanthanum borate is the same as that of Preparation Example 1, except that catechin is not added.

[0048] Preparation Example 4

[0049] The preparation method of nitrogen-doped carbon-coated lanthanum borate is the same as that of Preparation Example 1, except that in step S4, the mass of activated carbon source used is 55 g.

[0050] Preparation Example 5

[0051] The preparation method of nitrogen-doped carbon-coated lanthanum borate is the same as that of Preparation Example 1, except that in step S4, the mass of activated carbon source used is 25 g.

[0052] Example 1

[0053] An environment-friendly cutting lubricating oil comprises the following components in mass parts: 80 parts of isooctyl stearate, 5 parts of phosphate ester ammonium salt, 14 parts of sulfur-based extreme pressure anti-wear agent, and 3 parts of nitrogen-doped carbon-coated lanthanum borate.

[0054] The sulfur-based extreme pressure anti-wear agent comprises sulfated lard and sulfated fatty acid ester at a mass ratio of 1:1.1, and the nitrogen-doped carbon-coated lanthanum borate is prepared according to Preparation Example 1.

[0055] A preparation method of the environment-friendly cutting lubricating oil comprises the following steps: mixing isooctyl stearate, phosphate ester ammonium salt, sulfur-based extreme pressure anti-wear agent, and nitrogen-doped carbon-coated lanthanum borate, heating to 80℃, and stirring at constant temperature for 43 minutes to obtain the environment-friendly cutting lubricating oil.

[0056] Example 2

[0057] An environment-friendly cutting lubricating oil comprises the following components in mass parts: 50 parts of isooctyl stearate, 1 part of phosphate ester ammonium salt, 6 parts of sulfur-based extreme pressure anti-wear agent, and 1 part of nitrogen-doped carbon-coated lanthanum borate.

[0058] The sulfur-based extreme pressure anti-wear agent comprises sulfated lard and sulfated fatty acid ester at a mass ratio of 1:1, and the nitrogen-doped carbon-coated lanthanum borate is prepared according to Preparation Example 1.

[0059] A preparation method of the environment-friendly cutting lubricating oil comprises the following steps: mixing isooctyl stearate, phosphate ester ammonium salt, sulfur-based extreme pressure anti-wear agent, and nitrogen-doped carbon-coated lanthanum borate, heating to 70℃, and stirring at constant temperature for 35 minutes to obtain the environment-friendly cutting lubricating oil.

[0060] Example 3

[0061] An environment-friendly cutting lubricating oil comprises the following components in mass parts: 100 parts of isooctyl stearate, 10 parts of phosphate ester ammonium salt, 22 parts of sulfur-based extreme pressure anti-wear agent, and 5 parts of nitrogen-doped carbon-coated lanthanum borate.

[0062] The sulfur-based extreme pressure anti-wear agent comprises sulfated lard and sulfated fatty acid ester at a mass ratio of 1:1.2, and the nitrogen-doped carbon-coated lanthanum borate is prepared according to Preparation Example 1.

[0063] A preparation method of the environment-friendly cutting lubricating oil comprises the following steps: mixing isooctyl stearate, phosphate ester ammonium salt, sulfur-based extreme pressure anti-wear agent, and nitrogen-doped carbon-coated lanthanum borate, heating to 90℃, and stirring at constant temperature for 50 minutes to obtain the environment-friendly cutting lubricating oil.

[0064] Example 4

[0065] An environment-friendly cutting lubricating oil and a preparation method thereof are provided, and the specific implementation manner is the same as that in Embodiment 1, except that the nitrogen-doped carbon-coated lanthanum borate is prepared according to Preparation Example 2.

[0066] Example 5

[0067] An environmentally friendly cutting lubricating oil and a preparation method thereof, the specific implementation manner being the same as that of Example 1, except that the nitrogen-doped carbon-coated lanthanum borate is prepared from Preparation Example 3.

[0068] Example 6

[0069] An environmentally friendly cutting lubricating oil and a preparation method thereof, the specific implementation manner being the same as that of Example 1, except that the nitrogen-doped carbon-coated lanthanum borate is prepared from Preparation Example 4.

[0070] Example 7

[0071] An environmentally friendly cutting lubricating oil and a preparation method thereof, the specific implementation manner being the same as that of Example 1, except that the nitrogen-doped carbon-coated lanthanum borate is prepared from Preparation Example 5.

[0072] Comparative Example 1

[0073] An environmentally friendly cutting lubricating oil and a preparation method thereof, the specific implementation manner being the same as that of Example 1, except that equal mass parts of lanthanum borate particles are used instead of the nitrogen-doped carbon-coated lanthanum borate. The lanthanum borate particles are prepared from the S2 step in Preparation Example 1.

[0074] Performance test:

[0075] (1) Storage stability test: 50 mL of the cutting lubricating oil is taken into a 100 mL cylinder with a stopper, and is placed at 70°C for 5 h, then is placed at room temperature for 3 h, and is placed at -12°C for 24 h, and finally is naturally restored to room temperature to observe whether stratification, precipitation, turbidity or the like occurs;

[0076] (2) P d value, P b value and wear scar diameter determination: the test is performed in accordance with the standard of GBT3142-82 “Lubricant Load Capacity Determination Method (Four-ball Method) ”;

[0077] (3) Safety test: 24 male guinea pigs are grouped according to weight, 3 guinea pigs in each group, a total of 8 groups, and the average weight of the guinea pigs in each group is ensured to be approximately the same. The guinea pigs are shaved with a shaving razor on both sides of the dorsal spine, with an area of 3 cm x 3 cm. The left back of the guinea pigs in the experimental group is smeared with vegetable oil, and the right back is smeared with 2 mL of the cutting sample every day. The skin of the back of the guinea pigs is observed for redness, edema and the like within 1-14 days.

[0078] The cutting lubricating oils of the examples and the comparative examples are tested according to the above method, and the results are shown in Table 1.

[0079] Table 1 Test results of the lubricating properties and safety of the cutting lubricating oils of the examples and the comparative examples

[0080] Storage stability P d (N)]]> P b (N)]]> Abrasion diameter (588N / 20min) Safety Example 1 No change 8756 784 0.357 mm Skin normal Example 2 No change 8746 784 0.373 mm Skin normal Example 3 No change 8748 834 0.393 mm Skin normal Example 4 No change 8733 1020 0.443 mm Skin normal Example 5 No change 8529 1069 0.473 mm Skin normal Example 6 Slight precipitate 8721 1118 0.473 mm Skin normal Example 7 Slight turbidity 8727 1069 0.473 mm Skin normal Comparative Example 1 Slight precipitate 8612 981 0.837 mm Skin redness

[0081] According to the experimental data in Table 1, it can be seen that the cutting lubricating oil prepared in Examples 1-3 has good compatibility of components, is stable after long-term storage, and has good anti-wear performance and safety performance; in Example 4, the mass ratio of phenol glycidyl ether and catechin is changed, the crosslinking density of the two is increased, which leads to an increase in the particle size of the nitrogen-doped carbon-coated lanthanum borate, thus affecting the Pb value and the wear scar diameter; in Example 5, catechin is not added as an auxiliary carbon source, and the crosslinking density of the cashew phenol glycidyl ether alone is reduced, the steric hindrance after carbonization is reduced, which leads to a decrease in the dispersibility of the nitrogen-doped carbon-coated lanthanum borate, in addition, the reduction in the content of hydroxyl groups cannot effectively weaken the C-N bond energy, which makes it difficult for nitrogen elements to insert into the hybridization sites of the carbon skeleton, thus affecting the Pb value and the wear scar diameter; in Example 6, the mass ratio of the activated lanthanum borate particles and the activated carbon source is changed, and the increase in the activated carbon source leads to an increase in the thickness of the carbon layer after carbonization, thus increasing the particle size of the nitrogen-doped carbon-coated lanthanum borate, which is not conducive to dispersion, thus affecting the Pb value and the wear scar diameter; in Example 7, the mass ratio of the activated lanthanum borate particles and the activated carbon source is changed, and the reduction in the activated carbon source leads to the phenomenon of partial exposure of the lanthanum borate, which leads to a reduction in the number of pyridine nitrogen-graphite nitrogen active sites generated, thus reducing the performance of the boron nitride lubricating film generated during use, which is not conducive to the self-repairing ability, thus affecting the Pb value and the wear scar diameter; in Comparative Example 1, lanthanum borate particles replace the nitrogen-doped carbon-coated lanthanum borate, which leads to a decrease in dispersibility, thus affecting the Pb value and the wear scar diameter.

[0082] Finally, it should be explained that the above specific embodiments are only used to illustrate the technical solutions of the present application and not to limit it, although the present application has been described in detail with reference to examples, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application, which should be covered in the scope of the claims of the present application.

Claims

1. An environmentally friendly cutting lubricant, characterized by comprising: The composition comprises the following components: 50-100 parts of base oil, 1-10 parts of phosphate ester ammonium salt, 6-22 parts of sulfur-based extreme pressure anti-wear agent, and 1-5 parts of nitrogen-doped carbon-coated lanthanum borate. The preparation method of the nitrogen-doped carbon-coated lanthanum borate comprises the following steps: S1, mixing cashew phenol glycidyl ether and auxiliary carbon source, adding to ethanol solution, adding citric acid, heating to 70-80 DEG C constant temperature stirring 3-5h, reduced pressure concentration, freeze-drying to obtain activated carbon source; S2, mixing lanthanum nitrate and boric acid, adding polyethylene glycol, heating to 170-190 DEG C constant temperature stirring 11-13h, centrifugation, washing, to obtain lanthanum borate particles; S3, soaking the lanthanum borate particles in step S2 in sodium hydroxide solution, heating to 55-65 DEG C ultrasonic treatment 20-40min, then filtering, drying, to obtain activated lanthanum borate particles; S4, mixing the activated lanthanum borate particles in step S3 with the activated carbon source in step S1, adding ethanol, ball milling at a rotation speed of 250-350 rpm for 4-7h, then taking out, heating to 150-250 DEG C at a heating rate of 2-5 DEG C / min, then filling with inert protective gas, heating to 250-350 DEG C, and keeping for 1-4h to obtain pretreated carbon-coated lanthanum borate; S5, heating the pretreated carbon-coated lanthanum borate in step S4 to 300-350 DEG C under inert protective gas atmosphere, keeping for 20-40min, then heating to 450-550 DEG C under ammonia and inert protective gas atmosphere, keeping for 20-30min, and then heating to 500-700 DEG C, keeping for 10-30min to obtain nitrogen-doped carbon-coated lanthanum borate.

2. The environmentally friendly cutting lubricant according to claim 1, wherein The base oil is one or more of trimethylolpropane oleate, pentaerythritol oleate, bis-pentaerythritol ester, isooctyl oleate, isooctyl stearate, neopentyl glycol oleate, and diisooctyl adipate.

3. The environmentally friendly cutting lubricant according to claim 1, wherein The sulfur-based extreme pressure anti-wear agent comprises sulfurized lard oil and sulfurized fatty acid ester in a mass ratio of 1:(1-1.2).

4. The environmentally friendly cutting lubricant according to claim 1, wherein The auxiliary carbon source is chitosan or catechin.

5. The environmentally friendly cutting lubricant according to claim 1, wherein In step S1, the mass ratio of cashew phenol glycidyl ether to auxiliary carbon source is 1:(0.1-0.5).

6. The environmentally friendly cutting lubricant according to claim 1, wherein In step S1, the amount of citric acid is 0.2-0.8% of the total mass of cashew phenol glycidyl ether and auxiliary carbon source.

7. The environmentally friendly cutting lubricant according to claim 1, wherein In step S4, the mass ratio of activated lanthanum borate particles to activated carbon source is 1:(1.5-2.5).

8. The environmentally friendly cutting lubricant according to claim 1, wherein In step S5, the volume ratio of ammonia to inert protective gas is 1:(8-13).

9. A method of preparing the environmentally friendly cutting lubricant according to any one of claims 1 to 8, characterized by, The method comprises the following steps: mixing base oil, phosphate ester ammonium salt, sulfur-based extreme pressure anti-wear agent, and nitrogen-doped carbon-coated lanthanum borate, heating to 70-90 DEG C, and constant temperature stirring for 35-50min to obtain the environmentally friendly cutting lubricating oil.