Complex lithium-based lubricating grease and preparation method thereof

Abstract

The invention provides composite lithium-based lubricating grease with excellent oxidation resistance and extreme pressure wear resistance. Based on the total weight of the lubricating grease, the composite lithium-based lubricating grease comprises 1%-10% of an imidazoline derivative, 1%-10% of an anti-wear reagent at extreme pressure, 3%-30% of a composite lithium-based thickening agent and 65%-95% of lubricating base oil, wherein the structure of the imidazoline derivative is shown as a formula (I), in the formula (I), n is an integer between 1 and 10, and each R group is independently selected from C2-C5 alkylene; the R0 group is selected from C15-C20 alkyl, cycloalkyl or alkenyl; and each R'group is independently selected from alkyl groups of C1 to C20, aryl groups of C6 to C10, and aryl groups of C6 to C10 substituted by straight chain or branched chain alkyl groups of C1 to C10.

Description

Technical Field

[0001] The present invention relates to a lubricating grease, in particular to a composite lithium-based lubricating grease with excellent anti-oxidation, extreme pressure and anti-wear properties. Background Art

[0002] Grease is an essential working medium for the normal operation of mechanical equipment and in the manufacturing and processing of materials. With the progress and development of the machinery industry, more stringent requirements have gradually been placed on related grease products. Grease needs to have good antioxidant properties, extreme pressure and anti-wear properties, and a long service life.

[0003] To improve the antioxidant properties of grease, it is often necessary to add different types of antioxidants. Common antioxidant types include phenolic antioxidants, amine antioxidants, and sulfur-phosphorus-zinc salts. CN 109054965 adds alkyldiphenylamines or phenolic ester compounds as antioxidants to a lithium-based composite grease; CN 113999714 adds arylamines and alkylphenol compounds as antioxidants to a lithium-calcium composite grease; and CN 114395438 adds alkyl polybenzyltoluene derivatives, octyl / pentyldiphenylamine, and alkyl para-cresols as antioxidants to a lithium-based composite grease. These greases still have room for further improvement in terms of extreme pressure and anti-wear properties.

[0004] Developing grease with good anti-oxidation, extreme pressure and anti-wear properties is still the research and development direction of technical personnel in this field. Summary of the Invention

[0005] The present invention provides a composite lithium-based lubricating grease with excellent anti-oxidation, extreme pressure and anti-wear properties.

[0006] The composite lithium-based grease of the present invention comprises, based on the total weight of the grease, 1% to 10% of an imidazoline derivative, 1% to 10% of an extreme pressure anti-wear agent, 3% to 30% of a composite lithium-based thickener, and 65% to 95% of a lubricating base oil; wherein the structure of the imidazoline derivative is as shown in formula (I):

[0007]

[0008] In formula (I), n is an integer between 1 and 10, each R group is independently selected from a C2 to C5 alkylene group; R0 group is selected from a C 15 ~C 20 alkyl, cycloalkyl or alkenyl; each R' group is independently selected from C1 to C 20 Alkyl, C6~C 10 Aryl, C1~C 10 C6~C 10 of aromatic groups.

[0009] According to the present invention, the R0 group can be C 15 ~C 20 The alkyl group can also be C 15 ~C 20 The cycloalkyl group can also be C 15 ~C 20 The alkenyl group. 15 ~C 20 The alkenyl group may be a group containing one or more carbon-carbon double bonds within the group and an alkyl group at the end of the group, a group with a carbon-carbon double bond at the end of the group, or a group containing one or more carbon-carbon double bonds within the group and a carbon-carbon double bond at the end of the group.

[0010] According to the present invention, preferably, in formula (I), n is an integer between 1 and 5 (for example, 1, 2, 3, 4 or 5), each R group is independently selected from ethylene or propylene; R0 group is selected from C 16 ~C 18 Each R' group is independently selected from C2 to C8 alkyl, phenyl, C4 to C 10 The phenyl group substituted by a straight or branched alkyl group. 10 The straight chain or branched alkyl substituted phenyl group is preferably replaced by C4 to C 10 The phenyl group substituted with a straight-chain or branched alkyl group may be, for example, p-butylphenyl, p-isooctylphenyl, or p-nonylphenyl.

[0011] According to the present invention, the imidazoline derivative may be one or more of the following compounds:

[0012]

[0013]

[0014] According to the present invention, the preparation method of the imidazoline derivative comprises the following steps:

[0015] (1) reacting CS2 with a compound represented by formula (X);

[0016]

[0017] The R' groups are independently selected from C1 to C 20 Alkyl, C6~C 10 Aryl, C1~C 10 C6~C 10 aromatic groups;

[0018] (2) reacting the reaction product of step (1) with a compound represented by formula (Y), and collecting the product;

[0019]

[0020] wherein n is an integer between 1 and 10, each R group is independently selected from a C2 to C5 alkylene group; R0 group is selected from a C 15 ~C 20 an alkyl, cycloalkyl or alkenyl group.

[0021] According to the present invention, preferably, n is an integer between 1 and 5 (for example, 1, 2, 3, 4 or 5), each R group is independently selected from ethylene or propylene; R0 group is selected from C 16 ~C 18 Each R' group is independently selected from C2 to C8 alkyl, phenyl, C4 to C 10 The phenyl group substituted by a straight or branched alkyl group. 10 The straight chain or branched alkyl substituted phenyl group is preferably replaced by C4 to C 10 The phenyl group substituted with a straight-chain or branched alkyl group may be, for example, p-butylphenyl, p-isooctylphenyl, or p-nonylphenyl.

[0022] According to the present invention, in step (1), the reaction formula between CS2 and the compound represented by formula (X) is as follows.

[0023]

[0024] According to the present invention, in step (2), the reaction formula between the reaction product of step (1) and the compound represented by formula (Y) is as follows.

[0025]

[0026] According to the present invention, in step (1), the molar ratio between CS2 and the compound represented by formula (X) can be 0.8 to 1.3:1, preferably 0.9 to 1.2:1; in step (2), the molar ratio between the compound represented by formula (Y) and CS2 in step (1) can be 1:0.5 to 1.5, preferably 1:0.8 to 1.2.

[0027] According to the present invention, in step (1), the temperature for the reaction between CS2 and the compound represented by formula (X) can be 10 to 50° C., preferably 15 to 25° C.; the reaction time is usually 0.5 to 5 h, preferably 0.5 to 2.5 h; in step (2), the temperature for the reaction between the reaction product of step (1) and the compound represented by formula (Y) can be 60 to 100° C., preferably 70 to 90° C.; the reaction time is usually 0.5 to 3 h, preferably 1 to 2 h.

[0028] According to the present invention, the compound represented by formula (Y) can be prepared by subjecting the compound represented by formula (α) and the compound represented by formula (β) to an amidation dehydration reaction followed by a cyclodehydration reaction;

[0029]

[0030] wherein n is an integer between 1 and 10, each R group is independently selected from a C2 to C5 alkylene group; R0 group is selected from a C 15 ~C 20 an alkyl, cycloalkyl or alkenyl group.

[0031] According to the present invention, preferably, n is an integer between 1 and 5 (for example, 1, 2, 3, 4 or 5), each R group is independently selected from ethylene or propylene; R0 group is selected from C 16 ~C 18 alkyl or alkenyl.

[0032] According to the present invention, the molar ratio between the compound represented by formula (α) and the compound represented by formula (β) can be 1 to 2:1, preferably 1 to 1.5:1; during the reaction of the compound represented by formula (α) and the compound represented by formula (β), the temperature for the amidation dehydration reaction can be 140 to 180°C, preferably 140 to 160°C, and the reaction time is usually 1 to 3 hours, preferably 1 to 2 hours; the temperature for the cyclodehydration reaction can be 180 to 250°C, preferably 220 to 240°C, and the reaction time is usually 2 to 6 hours, preferably 3 to 5 hours.

[0033] According to the present invention, a water-carrying agent may or may not be added during the reaction between the compound represented by formula (α) and the compound represented by formula (β). The water-carrying agent may be an aromatic hydrocarbon solvent, such as xylene.

[0034] According to the present invention, the compound represented by formula (X) can be selected from one or more of di-n-butylamine, diphenylamine, 4-butyldiphenylamine, 4,4'-di-n-butyldiphenylamine, 4-isooctyldiphenylamine and 4,4'-diisooctyldiphenylamine; the compound represented by formula (α) can be selected from one or more of diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine; and the compound represented by formula (β) can be selected from one or more of hexadecanoic acid, octadecanoic acid, oleic acid and linoleic acid.

[0035] According to the present invention, in step (2), the product of the reaction product of step (1) and the compound shown in formula (Y) reacts comprises the imidazoline derivative main product and a small amount of by-products. Since these by-products themselves can be used as additives, these by-products can be separated out in step (2), or these by-products can be retained in the product and directly used as additives. Those skilled in the art can obtain pure imidazoline derivatives by purification or separation methods, such as those that can be enumerated by vacuum distillation, molecular distillation, column chromatography or preparative chromatography.

[0036] According to the present invention, the extreme pressure anti-wear agent can be a sulfur-based extreme pressure anti-wear agent and / or a phosphorus-based extreme pressure anti-wear agent, for example, one or more of sulfided isobutylene (codename T321), di-n-butyl phosphite (codename T304) and tricresyl phosphate (codename T306) can be selected.

[0037] According to the present invention, the composite lithium-based thickener is preferably obtained by saponification reaction of an acid with lithium hydroxide. The acid is a mixed acid of a fatty acid and an auxiliary acid, and the fatty acid is preferably selected from C 12 ~C 20 Fatty acids and / or C 12 ~C 20 The hydroxy fatty acid can be one or more of lauric acid, myristic acid, palmitic acid, oleic acid, stearic acid, and 12-hydroxystearic acid, with 12-hydroxystearic acid and / or stearic acid being more preferred. The auxiliary acid is preferably selected from one or more of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid, with azelaic acid and / or sebacic acid being more preferred. The molar ratio of the fatty acid to the auxiliary acid is preferably 0.1 to 5:1, more preferably 0.5 to 3:1. The composite lithium-based thickener obtained by the saponification reaction can be directly used in subsequent preparation processes. The saponification reaction temperature is preferably 60 to 180°C, more preferably 70 to 160°C. The saponification reaction time is preferably 30 to 300 minutes, more preferably 50 to 240 minutes. Water is preferably added to the saponification reaction. The water can participate in the saponification reaction directly or be mixed with the lithium hydroxide to form a solution before participating in the saponification reaction. The equivalent ratio between the acid and lithium hydroxide may be 1:0.5-2.

[0038] According to the present invention, the lubricating base oil can be selected from one or more of synthetic oil, mineral oil and vegetable oil. The synthetic oil can be one or more of polyalphaolefin oil, ester oil, fluorinated oil and silicone oil; the mineral oil can be one or more of paraffin base oil, intermediate base oil and naphthenic base oil; the vegetable oil can be one or more of castor oil, rapeseed oil, peanut oil and soybean oil. The lubricating base oil preferably has a kinematic viscosity of 2 to 60 mm at 100°C.2 / s lubricating base oil, preferably with a kinematic viscosity of 3 to 30 mm at 100 °C 2 / s lubricating base oil.

[0039] The preparation method of the lithium complex grease of the present invention comprises: refining the lithium complex thickener and a portion of the lubricating base oil at a constant temperature of 180-230°C, adding a portion of the lubricating base oil, cooling, adding the imidazoline derivative and the extreme pressure anti-wear agent, and grinding to form grease. The constant temperature refining time is preferably 1-25 minutes.

[0040] The composite lithium-based lubricating grease of the invention has excellent antioxidant performance and extreme pressure and anti-wear performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is the LC-MS chart of the alkyl-substituted imidazoline product of step (1) in Example 1.

[0042] Figure 2 LC-MS chart of the product of step (3) in Example 1 (i.e., imidazoline derivative). DETAILED DESCRIPTION

[0043] The present invention is further described below by way of examples, but is not intended to limit the present invention. The main raw materials used in the present invention are as follows:

[0044]

[0045]

[0046] Example 1

[0047] (1) 113 g of diethylenetriamine was added to a reaction kettle, and 282 g of oleic acid was added dropwise to the reaction kettle at 90° C. The temperature was raised to 160° C. for amidation dehydration. After 18 ml of water was removed, the temperature was raised to 240° C. for cyclization dehydration. After another 18 mL of water was removed, the reaction was stopped to obtain a hydrocarbon-substituted imidazoline.

[0048]

[0049] The prepared alkyl substituted imidazoline was subjected to high performance liquid chromatography-mass spectrometry analysis using a Waters liquid chromatography-mass spectrometer. Figure 1 . Figure 1 The upper middle graph is the UV absorption peak graph, and the lower graph is the mass spectrum signal graph. Figure 1It can be seen that the mass-to-charge ratio of the molecular ion peak corresponding to the two peaks at 0.33-0.55 min is 350.7 m / z, and these two peaks correspond to the peaks of the hydrocarbon-substituted imidazoline; the mass-to-charge ratio of the molecular ion peak corresponding to the peak at 0.6-0.75 min is 368.7 m / z, which corresponds to the peak of the oleamide by-product that failed to cyclize; the peaks at 4.6 and 4.8 min correspond to the peaks of the by-products of the continued amidation of imidazoline and oleic acid, and the continued amidation of oleamide and oleic acid, respectively.

[0050] (2) 129 g of di-n-butylamine and 76 g of carbon disulfide were reacted in 100 mL of water at a reaction temperature of 20° C. for 2 hours to generate a dithiocarbamic acid intermediate.

[0051]

[0052] (3) adding the hydrocarbon-substituted imidazoline obtained in step (1) to the dithiocarbamic acid intermediate obtained in step (2), reacting at 80° C. for 2 hours, and removing hydrogen sulfide to obtain the imidazoline derivative of the present invention.

[0053]

[0054] The prepared imidazoline derivatives were subjected to HPLC-MS analysis using Waters liquid chromatography-mass spectrometry. Figure 2 . Figure 2 The upper middle graph is the UV absorption peak graph, and the lower graph is the mass spectrum signal graph. Figure 2 It can be seen that the ion peak of 0.8min corresponds to the product of step (1); the ion peak of 1-1.3min corresponds to the imidazoline derivative; the ion peaks between 1.6-1.8min and 7-9min are the residual by-products in step (1).

[0055] In the product of embodiment 1, comprise described imidazoline derivative main product and a small amount of alkyl substituted imidazoline by-product, the by-product that fails cyclization oleamide by-product, alkyl substituted imidazoline continues to carry out amidation reaction with oleic acid, the by-product that fails cyclization oleamide continues to carry out amidation reaction with oleic acid.Because these by-products all can be used as lubricating oil additive, therefore in the present embodiment, there is no need to separate these by-products.Those skilled in the art can obtain pure imidazoline derivative by known purification or separation method.

[0056] Example 2

[0057] (1) 113 g of diethylenetriamine was added to a reaction kettle, and 280 g of linoleic acid was added dropwise to the reaction kettle at 90° C. The temperature was raised to 160° C. for amidation dehydration. After 18 ml of water was removed, the temperature was raised to 240° C. for cyclization dehydration. After another 18 mL of water was removed, the reaction was stopped to obtain a hydrocarbon-substituted imidazoline.

[0058] (2) 129 g of di-n-butylamine and 76 g of carbon disulfide were reacted in 100 mL of water at a reaction temperature of 20° C. for 2 hours to generate a dithiocarbamic acid intermediate.

[0059] (3) adding the hydrocarbon-substituted imidazoline obtained in step (1) to the dithiocarbamic acid intermediate obtained in step (2), reacting at 80° C. for 2 hours, and removing hydrogen sulfide to obtain the imidazoline derivative of the present invention.

[0060] Its structure is shown below.

[0061]

[0062] Example 3

[0063] (1) 113 g of diethylenetriamine was added to a reaction kettle, and 282 g of oleic acid was added dropwise to the reaction kettle at 90° C. The temperature was raised to 160° C. for amidation dehydration. After 18 ml of water was removed, the temperature was raised to 240° C. for cyclization dehydration. After another 18 mL of water was removed, the reaction was stopped to obtain a hydrocarbon-substituted imidazoline.

[0064] (2) 226 g of 4-butyldiphenylamine and 76 g of carbon disulfide were reacted in 100 mL of water at a reaction temperature of 20° C. for 2 hours to generate a dithiocarbamic acid intermediate.

[0065] (3) adding the hydrocarbon-substituted imidazoline obtained in step (1) to the dithiocarbamic acid intermediate obtained in step (2), reacting at 80° C. for 2 hours, and removing hydrogen sulfide to obtain the imidazoline derivative of the present invention.

[0066] Its structure is shown below.

[0067]

[0068] Example 4

[0069] (1) 113 g of diethylenetriamine was added to a reaction kettle, and 282 g of oleic acid was added dropwise to the reaction kettle at 90° C. The temperature was raised to 160° C. for amidation dehydration. After 18 ml of water was removed, the temperature was raised to 240° C. for cyclization dehydration. After another 18 mL of water was removed, the reaction was stopped to obtain a hydrocarbon-substituted imidazoline.

[0070] (2) 283 g of 4,4'-di-n-butyldiphenylamine and 76 g of carbon disulfide were reacted in 100 mL of water at a reaction temperature of 20°C for 2 hours to generate a dithiocarbamic acid intermediate.

[0071] (3) adding the hydrocarbon-substituted imidazoline obtained in step (1) to the dithiocarbamic acid intermediate obtained in step (2), reacting at 80° C. for 2 hours, and removing hydrogen sulfide to obtain the imidazoline derivative of the present invention.

[0072] Its structure is shown below.

[0073]

[0074] Example 5

[0075] (1) 113 g of diethylenetriamine was added to a reaction kettle, and 282 g of oleic acid was added dropwise to the reaction kettle at 90° C. The temperature was raised to 160° C. for amidation dehydration. After 18 ml of water was removed, the temperature was raised to 240° C. for cyclization dehydration. After another 18 mL of water was removed, the reaction was stopped to obtain a hydrocarbon-substituted imidazoline.

[0076] (2) 395 g of 4,4'-diisooctyldiphenylamine and 76 g of carbon disulfide were reacted in 100 mL of water at a reaction temperature of 20°C for 2 hours to generate a dithiocarbamic acid intermediate.

[0077] (3) adding the hydrocarbon-substituted imidazoline obtained in step (1) to the dithiocarbamic acid intermediate obtained in step (2), reacting at 80° C. for 2 hours, and removing hydrogen sulfide to obtain the imidazoline derivative of the present invention.

[0078] Its structure is shown below.

[0079]

[0080] Comparative Example 1

[0081] 113g of diethylenetriamine was placed in a reaction kettle. 282g of oleic acid was added dropwise at 90°C. The temperature was raised to 160°C for amidation dehydration. After 18ml of water was removed, the temperature was raised to 240°C for further cyclodehydration. The reaction was terminated after another 18ml of water was removed to yield a alkyl-substituted imidazoline. Its structure is shown below.

[0082]

[0083] Comparative Example 2

[0084] (1) 113 g of diethylenetriamine was placed in a reaction kettle, and 282 g of oleic acid was added dropwise to the reaction kettle at 90°C. The temperature was raised to 160°C for amidation dehydration. After 18 ml of water was removed, the temperature was raised to 240°C for cyclodehydration. After another 18 mL of water was removed, the reaction was stopped to obtain a hydrocarbon-substituted imidazoline.

[0085] (2) Add dodecenylsuccinic acid to the hydrocarbon-substituted imidazoline obtained in step (1), and react at 130° C. for 2 hours to obtain heptadecenyl imidazoline alkenylsuccinate. The structure of the heptadecenyl imidazoline alkenylsuccinate is shown below.

[0086]

[0087] Example 6

[0088] 250g PAO6 base oil, 48.6g 12-hydroxystearic acid, and 16.4g sebacic acid were added to a fat-making kettle, stirred evenly, heated to 90°C, and a lithium hydroxide aqueous solution (containing 13.6g lithium hydroxide monohydrate and 100g water) was added to carry out saponification reaction for 120min. 85g PAO6 base oil was added, and the temperature was raised to 210°C for high-temperature refining for 5min; 100g PAO6 base oil was added, the temperature was lowered to 110°C, 10g of the imidazoline derivative prepared in Example 1 and 5g of tricresyl phosphate were added, and the mixture was ground three times on a three-roll mill to form fat.

[0089] Example 7

[0090] The grease of Example 7 was prepared under the same conditions as in Example 6, except that the imidazoline derivative prepared in Example 1 was replaced by the imidazoline derivative prepared in Example 2.

[0091] Example 8

[0092] 300 g PAO10 base oil, 38.1 g 12-hydroxystearic acid, and 11.9 g azelaic acid were added to a fat-making kettle, stirred evenly, heated to 90 ° C, and a lithium hydroxide aqueous solution (containing 10.6 g lithium hydroxide monohydrate and 80 g water) was added for saponification reaction for 120 min. 50 g PAO10 base oil was added, and the temperature was raised to 210 ° C for high-temperature refining for 5 min; 100 g PAO10 base oil was added, the temperature was lowered to 110 ° C, 5 g of the imidazoline derivative prepared in Example 3 and 5 g of di-n-butyl phosphite were added, and the mixture was ground three times by a three-roll mill to form fat.

[0093] Example 9

[0094] The grease of Example 9 was prepared under the same conditions as in Example 8, except that the imidazoline derivative prepared in Example 3 was replaced by the imidazoline derivative prepared in Example 4.

[0095] Example 10

[0096] 300 g of 500N base oil, 29.9 g of 12-hydroxystearic acid, and 10.1 g of sebacic acid were added to a fat-making kettle, stirred evenly, heated to 90 ° C, and a lithium hydroxide aqueous solution (containing 8.4 g of lithium hydroxide monohydrate and 60 g of water) was added for saponification reaction for 120 min. 60 g of 500N base oil was added, and the temperature was raised to 210 ° C for high-temperature refining for 5 min; 100 g of 500N base oil was added, the temperature was lowered to 110 ° C, 15 g of the imidazoline derivative obtained in Example 5, 5 g of isobutylene sulfide, and 5 g of di-n-butyl phosphite were added, and the mixture was ground three times by a three-roll mill to form fat.

[0097] Comparative Example 3

[0098] The grease of Comparative Example 3 was prepared under the same conditions as in Example 6, except that the imidazoline derivative prepared in Example 1 was replaced by the imidazoline derivative prepared in Comparative Example 1.

[0099] Comparative Example 4

[0100] The grease of Comparative Example 4 was prepared under the same conditions as in Example 8, except that the imidazoline derivative prepared in Example 3 was replaced by the imidazoline derivative prepared in Comparative Example 2.

[0101] Comparative Example 5

[0102] The grease of Comparative Example 5 was prepared under the same conditions as in Example 6 except that the imidazoline derivative prepared in Example 1 used in Example 6 was not added.

[0103] Comparative Example 6

[0104] The grease of Comparative Example 6 was prepared under the same conditions as in Example 8, except that the imidazoline derivative prepared in Example 3 used in Example 8 was not added.

[0105] The performance of the greases of Examples 6 to 10 and Comparative Examples 3 to 6 was evaluated using the following evaluation methods: GB / T 269 "Determination of cone penetration of lubricating greases and petroleum greases", GB / T 3498 "Determination of dropping point of lubricating greases over a wide temperature range", NB / SH / T 0324 "Determination of oil separation of lubricating greases - cone and mesh method", SH / T 0325 "Determination of oxidation stability of lubricating greases", SH / T 0790 "Determination of oxidation induction period of lubricating greases", SH / T 0202 "Determination of extreme pressure properties of lubricating greases (four-ball tester method)", and SH / T 0204 "Determination of anti-wear properties of lubricating greases (four-ball tester method)". The evaluation results are shown in Table 1.

[0106] Table 1 Grease performance evaluation results

[0107]

Claims

1. A composite lithium-based grease comprising, based on the total weight of the grease, 1% to 10% of an imidazoline derivative, 1% to 10% of an extreme pressure anti-wear agent, 3% to 30% of a composite lithium-based thickener, and 65% to 95% of a lubricating base oil; The structure of the imidazoline derivative is shown in formula (I): In formula (I), n is an integer between 1 and 10, each R group is independently selected from a C2 to C5 alkylene group; R0 group is selected from a C 15 ~C 20 alkyl, cycloalkyl or alkenyl; each R' group is independently selected from C1 to C 20 Alkyl, C6~C 10 Aryl, C1~C 10 C6~C 10 of aromatic groups.

2. The lithium complex grease according to claim 1, characterized in that: In formula (I), n is an integer between 1 and 5, each R group is independently selected from ethylene or propylene; R0 group is selected from C 16 ~C 18 Each R' group is independently selected from C2 to C8 alkyl, phenyl, C4 to C 10 The phenyl group substituted by a straight chain or branched alkyl group (the C4 to C 10 The straight chain or branched alkyl substituted phenyl group is preferably replaced by C4 to C 10 a phenyl group substituted with a straight-chain or branched-chain alkyl group).

3. The lithium complex grease according to claim 1, characterized in that: The imidazoline derivatives are one or more of the following compounds:

4. The lithium complex grease according to claim 1, characterized in that: The preparation method of the imidazoline derivative comprises the following steps: (1) reacting CS2 with a compound represented by formula (X); The R' groups are independently selected from C1 to C 20 Alkyl, C6~C 10 Aryl, C1~C 10 C6~C 10 aryl groups; (2) reacting the reaction product of step (1) with a compound represented by formula (Y), and collecting the product; wherein n is an integer between 1 and 10, each R group is independently selected from a C2 to C5 alkylene group; R0 group is selected from a C 15 ~C 20 an alkyl, cycloalkyl or alkenyl group.

5. The lithium complex grease according to claim 4, characterized in that: n is an integer between 1 and 5, each R group is independently selected from ethylene or propylene; R0 group is selected from C 16 ~C 18 Each R' group is independently selected from C2 to C8 alkyl, phenyl, C4 to C 10 The phenyl group substituted by a straight chain or branched alkyl group (the C4 to C 10 The straight chain or branched alkyl substituted phenyl group is preferably replaced by C4 to C 10 a phenyl group substituted with a straight-chain or branched-chain alkyl group).

6. The lithium complex grease according to claim 4, characterized in that: In step (1), the molar ratio of CS2 to the compound represented by formula (X) is 0.8 to 1.3:1; in step (2), the molar ratio of the compound represented by formula (Y) to CS2 in step (1) is 1:0.5 to 1.

5.

7. The lithium complex grease according to claim 4, characterized in that: In step (1), the temperature for the reaction between CS2 and the compound represented by formula (X) is 10 to 50° C., and the reaction time is 0.5 to 5 h. In step (2), the temperature for the reaction between the reaction product of step (1) and the compound represented by formula (Y) is 60 to 100° C., and the reaction time is 0.5 to 3 h.

8. The lithium complex grease according to claim 4, characterized in that: The compound represented by formula (Y) is prepared by subjecting the compound represented by formula (α) and the compound represented by formula (β) to an amidation dehydration reaction followed by a cyclization dehydration reaction; wherein n is an integer between 1 and 10, each R group is independently selected from a C2 to C5 alkylene group; R0 group is selected from a C 15 ~C 20 an alkyl, cycloalkyl or alkenyl group.

9. The lithium complex grease according to any one of claims 1 to 8, characterized in that: The extreme pressure anti-wear agent is selected from sulfur-based extreme pressure anti-wear agents and / or phosphorus-based extreme pressure anti-wear agents; the composite lithium-based thickener is obtained by saponification reaction between acid and lithium hydroxide; and the lubricating base oil is selected from one or more of synthetic oil, mineral oil and vegetable oil.

10. The lithium complex grease according to claim 9, characterized in that: The extreme pressure anti-wear agent is selected from one or more of sulfided isobutylene, di-n-butyl phosphite and tricresol phosphate; the acid is a mixed acid of fatty acid and auxiliary acid, and the fatty acid is selected from C 12 ~C 20 Fatty acids and / or C 12 ~C 20 The auxiliary acid is selected from one or more of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid and sebacic acid; the synthetic oil is one or more of poly-α-olefin oil, ester oil, fluoro oil and silicone oil; the mineral oil is one or more of paraffin base oil, intermediate base oil and cycloalkyl base oil; the vegetable oil is one or more of castor oil, rapeseed oil, peanut oil and soybean oil.

11. A method for preparing the complex lithium-based grease according to any one of claims 1 to 10, comprising: The composite lithium-based thickener and part of the lubricating base oil are refined at a constant temperature of 180-230° C., part of the lubricating base oil is added, cooled, and the imidazoline derivative and extreme pressure anti-wear agent are added, and ground into grease.

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