Wide-temperature high-extreme-pressure environment-friendly composite lithium-based lubricating grease composition and preparation method thereof

Abstract

The invention relates to the technical field of complex lithium-based lubricating grease, and discloses a wide-temperature high-extreme-pressure environment-friendly complex lithium-based lubricating grease composition which comprises the following components in percentage by mass: 80-90% of base oil, 10-15% of a thickening agent and 0-5% of an additive, the base oil is a mixture composed of IV-type base oil and polyalkyl cycloalkane, the compatibility between oil soap can be improved by adding the polyalkyl cycloalkane, and the stability of the composite lithium-based grease is improved; the thickening agent is composite lithium soap formed after saponification reaction of higher fatty acid, amino acid and lithium hydroxide, fatty dibasic acid commonly used in the prior art is replaced with the amino acid, and high extreme pressure anti-wear performance can be achieved by adding a very small amount or without adding a solid extreme pressure anti-wear agent or phosphorus, boron and other extreme pressure anti-wear agents; the additive is selected from one or more of a series of materials, and the series of materials comprise but are not limited to an extreme pressure anti-wear agent, an antioxidant and an anti-rust agent.

Description

Technical Field

[0001] The present invention relates to the technical field of composite lithium-based lubricating grease, and in particular to a wide-temperature, high-extreme-pressure, and environmentally friendly composite lithium-based lubricating grease composition and a preparation method thereof. Background Art

[0002] With the development of modern industry, especially the continuous upgrading and replacement of technology and equipment in metallurgy, automobile, mining and other industries, the requirements for high temperature resistance of grease are getting higher and higher. At the same time, due to the vast territory of my country, the equipment used outdoors in the automobile, mining and other industries also has high requirements for low temperature resistance. Some equipment requires a minimum operating temperature of -40℃ or even lower. In order to improve production efficiency and reduce costs, large-scale, automated and heavy-loaded equipment is a development trend in metallurgy, mining, automobile and other industries, which puts higher requirements on the extreme pressure performance of grease. Therefore, it is very necessary to invent a grease with excellent high and low temperature properties that can be used in a wide temperature range and has excellent extreme pressure and anti-wear properties.

[0003] Composite lithium-based grease has good high-temperature performance, and the dropping point is generally greater than 260°C. Through the adjustment of process and formula, high-quality grease with balanced performance can be produced. Composite lithium soap is divided into three categories according to its components. One is the composite lithium of fatty dibasic acid (mainly sebacic acid, azelaic acid, adipic acid, etc.) and dodecyl hydroxystearic acid. The second is the composite lithium of inorganic acid such as boric acid and phosphoric acid with dodecyl hydroxystearic acid. The third is the addition of aromatic acids such as salicylic acid and benzoic acid to the above two. However, the performance of base grease often cannot meet actual needs, so there are a large number of literature and patents discussing the addition of other compounds or various additives to improve the performance of composite lithium-based grease.

[0004] Extreme pressure performance is the key performance of grease used in heavy-load lubrication conditions. The thickener of complex lithium-based grease is generally composed of two or more organic acid salts, and its extreme pressure performance is poor. Complex lithium-based grease used in heavy-load and harsh lubrication conditions generally improves its extreme pressure performance by adding a large amount of extreme pressure anti-wear agents. At present, the main extreme pressure anti-wear agents added are solid extreme pressure anti-wear agents, phosphorus-containing extreme pressure anti-wear agents, and boron-containing extreme pressure anti-wear agents. Patent CN104560264A improves the extreme pressure performance of composite lithium-based grease by adding graphene; Patent CN1364859A improves the extreme pressure performance of composite lithium-based grease by adding molybdenum dioxide and antimony trioxide; Patent CN102250671A improves the high and low temperature performance and extreme pressure anti-wear performance of the grease composition by adding a composite extreme pressure anti-wear agent composed of dialkyl dithiocarbamate, dialkyl zinc dithiophosphate, borate and thiophosphate; Patent CN115960656A improves the antioxidant performance and anti-wear and friction reduction performance of composite lithium-based grease by adding organic boron compounds. Adding extreme pressure anti-wear agents can significantly improve the extreme pressure and anti-wear performance of composite lithium-based grease, however, adding solid additives and additives such as phosphorus and boron extreme pressure anti-wear agents will have a destructive effect on the colloidal structure of the grease, resulting in reduced storage stability, colloidal stability, mechanical stability and other properties of the grease. In addition, the presence of elements such as phosphorus and boron in extreme pressure anti-wear agents will also cause varying degrees of pollution and harm to the environment and human body. Therefore, in order to obtain the type and amount of extreme pressure anti-wear agents with good performance suitable for complex lithium-based grease, it is necessary to conduct long-term and large-scale tests to evaluate the effects of extreme pressure anti-wear agents on the colloidal structure and performance of grease, which greatly hinders the rapid development of complex lithium-based grease. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides an environmentally friendly composite lithium-based grease composition that can achieve a wide temperature range and high extreme pressure. The addition of polyalkyl cycloalkanes can improve the compatibility between oils and soaps and improve the stability of the composite lithium-based grease. Amino acids are used instead of the fatty dibasic acids commonly used in the prior art. A very small amount of solid extreme pressure anti-wear agents, or extreme pressure anti-wear agents such as phosphorus-based and boron-based agents can be added to achieve higher extreme pressure and anti-wear performance, which is more environmentally friendly as a whole.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions: A wide temperature range, high extreme pressure and environmentally friendly composite lithium-based grease composition, the components of the grease composition include the following components by mass percentage: Base oil 80-90%, Thickener 10-15%, Additives 0-5%; The base oil is a mixture of Group IV base oil and polyalkyl cycloalkanes; The thickener is a complex lithium soap formed by saponification reaction of higher fatty acids, amino acids and lithium hydroxide; The additive is selected from one or more of a series of materials, which include but are not limited to extreme pressure anti-wear agents, antioxidants, and rust inhibitors.

[0007] Preferably, the base oil has a kinematic viscosity of 2-20 mm at 100°C. 2 / s, 40℃ kinematic viscosity is 80-140mm 2 / s, viscosity index>180.

[0008] Preferably, the Group IV base oil is a mixture of polyalphaolefin (PAO) and metallocene polyalphaolefin (mPAO).

[0009] Among them, metallocene polyalphaolefin refers to C4-C 20 The product obtained by polymerization of linear alpha olefins under a metallocene catalyst system. The metallocene catalyst system comprises at least one metallocene catalyst, and the metallocene catalyst is an inorganic-organic complex containing at least one cyclopentadienyl or cyclopentadienyl derivative as a ligand and at least one IVB group transition element as a central atom.

[0010] Polyalphaolefins refer to C4-C 20 The product obtained by the polymerization reaction of linear alpha olefins under a non-metallocene catalyst system. The non-metallocene catalyst system comprises at least one non-metallocene catalyst, and the non-metallocene catalyst specifically comprises: a non-metallocene inorganic-organic complex, formed by a ligand without a cyclopentadiene structure and a transition metal or a rare earth metal element, wherein the metal center comprises a transition metal and a rare earth metal element from group IIIB to group VIII, and coordinated with the ligand is a ligand containing heteroatoms such as N, O, S, and P, such as an α-diimine metal organic compound, a β-diimine metal organic compound, a β-diketoimine metal organic compound, an amidine metal organic compound, and a P-containing metal organic compound; a homogeneous Lewis acid catalyst activator, such as AlCl3, AlBr3, TiCl3, SiCl3, BiCl3, FeCl3, BF3 and BF3-ROH; heterogeneous Lewis acid catalyst, composed of the above homogeneous Lewis acid catalyst and inorganic porous material, wherein the inorganic porous material is selected from one or more of mesoporous carbon, carbon nanotubes, activated carbon fibers, acetylene black, carbon black, expanded graphite, and graphene; Ziegler-Natta catalyst, composed of Et3Al and TiCl4; chromium-based catalysts, such as chromium oxide, chromium halide, chromium phosphate, sulfate, nitrate, oxalate, etc.

[0011] Furthermore, the PAO is selected from one or more of PAO6, PAO300, and PAO1000, and the mPAO is selected from one or more of mPAO3.5, mPAO150, and mPAO1000.

[0012] More preferably, the Group IV base oil is a combination of PAO6, mPAO150 and mPAO1000.

[0013] Preferably, the polyalkylcycloalkane is polyalkylcyclopentane. More preferably, the polyalkylcyclopentane is selected from one or more of decylcyclopentane, dodecylcyclopentane and 2-octyldodecylcyclopentane.

[0014] Preferably, the higher fatty acid is a C8-C20 fatty acid or a hydroxy fatty acid. More preferably, the higher fatty acid is selected from one or more of lauric acid, palmitic acid, stearic acid, dodecyl hydroxystearic acid, and eicosyl carboxylic acid. More preferably, the higher fatty acid is dodecyl hydroxystearic acid.

[0015] Preferably, the amino acid is selected from one or more of methionine, alanine, aspartic acid, glutamic acid, lysine, arginine, histidine, threonine, phenylalanine, tryptophan, valine, and glycine. More preferably, the amino acid is selected from one or more of lysine, arginine, and histidine.

[0016] Preferably, the addition amount of the extreme pressure anti-wear agent is 0-3%, and the extreme pressure anti-wear agent is selected from one or more of sulfur extreme pressure anti-wear agents, phosphorus extreme pressure anti-wear agents, and sulfur-phosphorus extreme pressure anti-wear agents. Specifically, the sulfur extreme pressure anti-wear agent can be sulfurized oils and fats, thiofatty acids, thioesters, thioolefins, dialkyl polysulfides, thiadiazole compounds, alkylthiocarbamoyl compounds, thiocarbamate compounds, etc.; the phosphorus extreme pressure anti-wear agent can be phosphates, phosphites, acidic phosphates, acidic phosphites and their amine salts, etc.; the sulfur-phosphorus extreme pressure anti-wear agent can be zinc dialkylthiocarbamate (Zn-DTC), molybdenum dialkylthiocarbamate (Mo-DTC), zinc dialkyl dithiophosphate (Zn-DTP), molybdenum dialkyl dithiophosphate (Mo-DTP), etc.

[0017] Preferably, the antioxidant is added in an amount of 0.1-0.5%; the antioxidant is selected from one or two of phenolic antioxidants, amine antioxidants, and molybdenum antioxidants. Specifically, the phenolic antioxidant may be a monophenolic antioxidant, a diphenolic antioxidant, a hindered phenolic antioxidant, etc.; the amine antioxidant may be diphenylamine, alkyl diphenylamine, phenyl-α-naphthylamine, etc.; the molybdenum antioxidant may be a molybdenum amine complex formed by the reaction of molybdenum trioxide and / or molybdic acid with an amine compound, etc.

[0018] Preferably, the amount of the rust inhibitor added is 0.05-1.5%; the rust inhibitor is selected from any one or more combinations of benzotriazole, alkyltriazole, benzothiazole, benzimidazole, thiadiazole and their corresponding derivatives.

[0019] Furthermore, the present invention also provides a method for preparing the grease composition, comprising the following steps: S1. Add 1 / 3 of the base oil, higher fatty acids and amino acids into the fat-making device, and stir and dissolve them at 80-90°C; S2, adding lithium hydroxide aqueous solution to the above-mentioned fat making device, heating up for saponification reaction, the saponification temperature is 90-110°C, the saponification time is 1-2h, and after the saponification is completed, the temperature is increased for dehydration, and the dehydration temperature is 110-120°C; S3, add 1 / 3 of base oil, continue to heat up to 210-215℃, and keep the temperature constant for 3-7 minutes; S4, stop heating, pour in the remaining 1 / 3 of the base oil to cool, add additives, transfer to a grinding device for grinding after homogenization, and obtain a composite lithium-based grease composition.

[0020] The beneficial effects of the present invention are: The base oil is a combination of Class IV base oil and polyalkyl cycloalkanes with suitable viscosity. The addition of polyalkyl cycloalkanes can improve the compatibility between oils and soaps and the stability of complex lithium-based grease. The thickener adopts a composite lithium soap composed of higher fatty acids and amino acids, and amino acids are used instead of the fatty dibasic acids commonly used in the prior art. After the obtained thickener is added to the base oil, the amino acids can play the extreme pressure and anti-wear role of amine extreme pressure anti-wear agents because they contain amino groups. A very small amount of solid extreme pressure anti-wear agents, or extreme pressure anti-wear agents such as phosphorus and boron can be added without adding any more extreme pressure anti-wear agents to achieve higher extreme pressure and anti-wear performance. Compared with the existing composite lithium-based grease containing extreme pressure anti-wear agents, the composite lithium-based grease of the present invention is more environmentally friendly. DETAILED DESCRIPTION

[0021] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] The raw material components used in the examples and comparative examples of this application are shown in Table 1 below.

[0023] Table 1 Components Name / Model source Type IV base oil PAO6 Chevron Type IV base oil mPAO150 Ipomoea Type IV base oil mPAO1000 Ipomoea Higher fatty acids Dodecyl Hydroxystearic Acid Guangzhou Fufei Chemical Amino Acids L-Lysine Myrelle Amino Acids L-Arginine Myrelle Amino Acids L-Histidine Myrelle Lithium hydroxide monohydrate Lithium hydroxide monohydrate Zhengzhou Yashen Chemical Extreme pressure anti-wear agent T351 Jinzhou Kangtai Extreme pressure anti-wear agent T406A Binzhou Kunhou Antioxidants T534 Jinzhou Shengda University Rust inhibitor T551 Panhua Chemical Rust inhibitor T751 Panhua Chemical The relevant properties of the base oil in each embodiment and comparative example of the present application are shown in Table 2 below.

[0024] Table 2 name type <![CDATA[Kinematic viscosity @ 100 °C / mm²·s -1 > <![CDATA[Kinematic viscosity @ 40 °C / mm²·s -1 > Viscosity Index PAO6 Polyalphaolefin, Group IV base oil 5.84 30.37 138 mPAO150 Metallocene polyalphaolefin, Group IV base oil 148.54 1341.77 225 mPAO1000 Metallocene polyalphaolefin, Group IV base oil 1020.41 10958.65 319 From the properties of each component in Table 2, it can be seen that PAO6, mPAO150, and mPAO1000 are respectively Class IV of the base oil classification in the API (American Petroleum Institute) standard, among which the pour point of PAO6 can be as low as -58°C. A certain amount of PAO6 is selected to be added to the grease formula to improve the low-temperature performance of the grease. The high-viscosity metallocene polyalphaolefin mPAO150 and mPAO1000 also have a high viscosity index. They can be used as tackifiers in the formula to increase the viscosity index of the base oil and adjust the kinematic viscosity of the grease base oil at the same time. The 100°C kinematic viscosity of the obtained base oil is 2-20 mm 2 / s, 40℃ kinematic viscosity is 80-140mm 2 / s, viscosity index not less than 180. Example

[0025] The formula of the complex lithium grease of Examples 1-9 is shown in Table 3.

[0026] Table 3 Component dosage / g Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 PAO6 50.9 51.9 53.9 50.5 48 54.5 54.5 50.9 50.9 mPAO150 9.7 10 10.5 9.7 9.7 0 15.5 9.7 9.7 mPAO1000 9.8 10 10.5 9.8 9.8 15.5 0 9.8 9.8 Polyalkylcycloalkanes 9.5 10 11 9.5 9.5 9.5 9.5 9.5 9.5 Dodecyl Hydroxystearic Acid 10.8 9.8 6.6 10.8 10.8 10.8 10.8 11.2 10 Lysine 4.2 3.7 3.4 4.2 4.2 4.2 4.2 0 0 Arginine 0 0 0 0 0 0 0 3.8 0 Histidine 0 0 0 0 0 0 0 0 5 Lithium hydroxide monohydrate 3 2.5 2 3 3 3 3 3 3 T351 0 0 0 0.3 2.8 0.3 0.3 0 0 T406A 0 0 0 0.1 0.1 0.1 0.1 0 0 T534 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 T551 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 T751 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Preparation method: S1. Add 1 / 3 of the base oil, dodecyl stearic acid and amino acid into the fat making device, and stir and dissolve at 85°C; S2, adding lithium hydroxide aqueous solution to the above-mentioned fat making device, heating to 100°C, saponification reaction for 1.5h, and after the saponification is completed, heating to 110°C for dehydration; S3, add 1 / 3 of the base oil, continue to heat up to 210℃, and keep the temperature constant for 5 minutes; S4, stop heating, pour in the remaining 1 / 3 of the base oil to cool, add additives, transfer to a grinding device for grinding after homogenization, and obtain a composite lithium-based grease composition.

[0027] Comparative Example Comparative Example 1 A composite lithium-based grease, which is different from Example 1 in that the base oil comprises: 60.5 g of PAO6, 10.7 g of mPAO150, 10.8 g of mPAO1000, and 0 g of polyalkyl cyclopentane.

[0028] Comparative Example 2 A composite lithium-based grease, which is different from Example 1 in that sebacic acid is used instead of amino acid.

[0029] Comparative Example 3 A composite lithium-based grease, which is different from Example 1 in that the thickener is a mixed lithium soap formed by physically mixing lithium dodecyl stearate and lithium amino acid. The preparation steps include: according to the preparation method of Example 1, dodecyl stearic acid and amino acid are separated and made into fats separately, and after the preparation is completed, the two fats are stirred and mixed evenly.

[0030] Performance testing The performance of the composite lithium-based grease prepared in Examples 1-9 and Comparative Examples 1-3 was tested respectively. The test results are shown in Table 4.

[0031] Dropping point: GB / T 4929-1985 "Determination of dropping point of grease" is used to determine the dropping point of grease.

[0032] Mechanical shear stability: GB / T 269-1991 "Determination of cone penetration of greases and petroleum greases" was used to measure the unworked cone penetration, 60-times worked cone penetration and 100,000-times worked cone penetration of the grease at 25°C. The difference in cone penetration was obtained by subtracting the 60-times worked cone penetration from the 100,000-times worked cone penetration.

[0033] Anti-friction performance: The average wear spot diameter of the grease sample was measured using ASTM D2266 "Standard Test Method for Anti-wear Properties of Grease (Four-ball Machine Method)"; the four-ball test conditions were: load: 392 N (40 kgf); spindle speed: 1200 r / min; test time: 60 min; test temperature: 75°C. After the test, the wear spot diameter of the lower steel ball was measured, where the smaller the wear spot diameter, the better the anti-wear performance of the sample. The average of the wear spot diameters of the three lower steel balls was taken to evaluate the anti-wear performance of the grease sample.

[0034] Colloid stability: NB / SH / T 0324-2010 "Determination of steel mesh oil separation of grease - cone mesh method" was used to test the steel mesh oil separation percentage (w / w, %) of the grease. The test conditions were: 100°C, 30 h.

[0035] Copper sheet corrosion: GB 7326-1987 "Lubricating grease copper sheet corrosion test method" is used to measure the corrosion of grease to copper sheets.

[0036] Table 4 Test items Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Comparative Example 1 Comparative Example 2 Comparative Example 3 Appearance Light yellow Light yellow Light yellow Light yellow Light yellow Light yellow Light yellow Light yellow Light yellow Light yellow Light yellow Light yellow Dropping point / ℃ 299 300 297 297 295 290 291 300 305 285 299 265 Unworked cone penetration / 0.1mm 252 250 254 258 275 254 258 251 248 278 254 262 60 times shear penetration / 0.1mm 260 254 260 258 278 265 270 254 245 280 266 285 100,000 times shear cone penetration / 0.1mm 277 270 282 292 326 291 300 270 260 340 294 357 Cone penetration difference 17 16 22 34 48 26 30 16 15 60 28 72 Four-ball wear spot diameter / mm 0.458 0.454 0.461 0.450 0.449 0.478 0.479 0.455 0.451 0.475 0.821 1.25 Steel mesh oil separation rate / % 0.63 0.60 0.68 0.71 0.82 0.82 0.87 0.62 0.58 1.12 0.66 2.21 Copper corrosion / grade 1b 1b 1b 1b 1b 1b 1b 1b 1b 1b 1b 1b It can be seen from the test results of Examples 1-9 in Table 4 that the present application prepares a composite lithium-based grease by reacting a composite amino acid and dodecyl stearic acid with lithium hydroxide, and the obtained grease has high mechanical shear stability and colloidal stability, and the difference between its 100,000 shear cone penetration and 60 shear cone penetration can be as low as 15, and the grease composition has a four-ball wear spot diameter of 0.451-0.461 mm without adding an extreme pressure anti-wear agent, and has excellent anti-wear performance.

[0037] Comparing the test results of Examples 1 and 4, it can be seen that Example 4 adds an extreme pressure anti-wear agent compared to Example 1. It can be seen that the addition of the extreme pressure anti-wear agent improves the anti-wear performance of the grease of the present application to a certain extent, but the improvement is limited, and the addition of the extreme pressure anti-wear agent will instead cause the shear stability and colloid stability of the grease of the present application to be reduced to a certain extent.

[0038] Comparing the test results of Examples 1, 4, and 5, it can be seen that the amount of extreme pressure anti-wear agent used in Example 5 is increased compared to Example 1. It can be seen that with the increase in the amount of extreme pressure anti-wear agent, the anti-wear performance of the grease of the present application has not been improved. The values ​​of 100,000 cone penetrations and steel mesh oil separation rate have both increased significantly, indicating that the increase in the amount of extreme pressure anti-wear agent has a significant negative impact on the mechanical shear stability and colloid stability of the grease of the present application.

[0039] By comparing the test results of Examples 1, 6 and 7, it can be seen that different combinations of base oils have a certain influence on the performance of the grease, especially the dropping point, mechanical shear stability and colloidal stability of the grease.

[0040] By comparing the test results of Example 1 and Comparative Example 1, it can be seen that the presence of polyalkyl cyclopentane in the base oil can significantly improve the dropping point, mechanical shear stability and colloidal stability of the grease composition.

[0041] By comparing the test results of Example 1 and Comparative Example 2, it can be seen that when azelaic acid is used to replace the amino acid in the present application, the anti-wear performance of the prepared composite lithium-based grease is significantly reduced without adding an extreme pressure anti-wear agent, and the use requirements cannot be met without adding an extreme pressure anti-wear agent.

[0042] By comparing the test results of Example 1 and Comparative Example 3, it can be seen that the mixed grease obtained by preparing lithium dodecyl stearate and amino acid lithium thickener separately and then mixing them to make grease has poor performance. This is because the lithium dodecyl stearate and amino acid lithium are prepared separately and then mixed, the "lithium bond" force between the two is weak, and the mixed grease has poor stability. In addition, amino acid lithium grease itself is difficult to form grease, and the performance of the grease prepared after mixing with lithium dodecyl stearate grease cannot meet the use requirements.

[0043] The above is a description of the embodiments of the present invention. Through the above description of the disclosed embodiments, professionals and technicians in the field can implement or use the present invention. Various modifications to these embodiments will be apparent to professionals and technicians in the field. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown in this article, but will conform to the widest range consistent with the principles and novelties disclosed herein.

Claims

1. A wide temperature range, high extreme pressure and environmentally friendly composite lithium-based grease composition, characterized in that: The components of the grease composition include the following components by mass percentage: Base oil 80-90%, Thickener 10-15%, Additives 0-5%; The base oil is a mixture of Group IV base oil and polyalkyl cycloalkanes; The thickener is a complex lithium soap formed by saponification reaction of higher fatty acids, amino acids and lithium hydroxide; The additive is selected from one or more of a series of materials, which include but are not limited to extreme pressure anti-wear agents, antioxidants, and rust inhibitors.

2. The grease composition according to claim 1, characterized in that The base oil has a kinematic viscosity of 2-20 mm at 100°C. 2 / s, 40℃ kinematic viscosity is 80-140mm 2 / s, viscosity index>180.

3. The grease composition according to claim 1, characterized in that The Class IV base oil is a mixture of PAO and mPAO; preferably, the PAO is selected from one or more of PAO6, PAO300, and PAO1000, and the mPAO is selected from one or more of mPAO3.5, mPAO150, and mPAO1000; more preferably, the Class IV base oil is a combination of PAO6, mPAO150, and mPAO1000.

4. The grease composition according to claim 1, characterized in that The polyalkyl cycloalkane is a polyalkyl cyclopentane; preferably, the polyalkyl cyclopentane is selected from one or more of decyl cyclopentane, dodecyl cyclopentane and 2-octyldodecyl cyclopentane.

5. The grease composition according to claim 1, characterized in that The higher fatty acid is C8-C 20 Preferably, the higher fatty acid is selected from one or more of lauric acid, palmitic acid, stearic acid, dodecylhydroxystearic acid, and eicosyl carboxylic acid; more preferably, the higher fatty acid is dodecylhydroxystearic acid.

6. The grease composition according to claim 1, characterized in that The amino acid is selected from one or more of methionine, alanine, aspartic acid, glutamic acid, lysine, arginine, histidine, threonine, phenylalanine, tryptophan, valine, and glycine; preferably, the amino acid is selected from one or more of lysine, arginine, and histidine.

7. The grease composition according to claim 1, characterized in that The addition amount of the extreme pressure anti-wear agent is 0-3.0%, and the extreme pressure anti-wear agent is selected from one or more of sulfur-based extreme pressure anti-wear agents, phosphorus-based extreme pressure anti-wear agents, and sulfur-phosphorus-based extreme pressure anti-wear agents.

8. The grease composition according to claim 1, characterized in that The added amount of the antioxidant is 0.1-0.5%; the antioxidant is selected from one or two of phenolic antioxidants, amine antioxidants, and molybdenum antioxidants.

9. The grease composition according to claim 1, characterized in that: The amount of the rust inhibitor added is 0.05-1.5%; the rust inhibitor is selected from any one or more combinations of benzotriazole, alkyltriazole, benzothiazole, benzimidazole, thiadiazole and their corresponding derivatives.

10. The method for preparing the grease composition according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Add 1 / 3 of the base oil, higher fatty acids and amino acids into the fat-making device, and stir and dissolve them at 80-90°C; S2, adding lithium hydroxide aqueous solution to the above-mentioned fat making device, heating up for saponification reaction, the saponification temperature is 90-110°C, the saponification time is 1-2h, and after the saponification is completed, the temperature is increased for dehydration, and the dehydration temperature is 110-120°C; S3, add 1 / 3 of base oil, continue to heat up to 210-215℃, and keep the temperature constant for 3-7 minutes; S4, stop heating, pour in the remaining 1 / 3 of the base oil to cool, add additives, transfer to a grinding device for grinding after homogenization, and obtain a composite lithium-based grease composition.