Grease composition and preparation method thereof

Abstract

The invention provides a grease composition and a preparation method thereof. The grease composition comprises base oil, a thickening agent and a styrene-based block copolymer containing ethylene-alpha-olefin copolymerized repeating units as a first polymer additive, and the grease composition comprises 1.5%-15% by weight of the first polymer additive based on the total weight of the grease composition.

Description

[0001] Related Applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0154833 filed on November 9, 2023, in the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to a grease composition having improved water washout characteristics, long-term lubricity, low-temperature storage performance, and discoloration resistance, and a method for preparing the same. Background Art

[0004] Grease is a semi-solid oil optimized for lubrication of mechanical element systems such as bearings and gears, which are key components in automobiles and industry. Typically, grease consists of base oil, thickener and additives.

[0005] Generally, when grease is used for a long time, some base oil separates from the thickener, which may cause problems in the operation of the parts. Specifically, due to the inflow of external moisture, etc., there is a high possibility that the grease applied to the parts that may be easily exposed to the external environment (such as the door module) will be lost. In addition, the grease lost due to the inflow of external moisture may react with the sealing strip, the side sealing molding, etc. located at the lower part of the door and damage the sealing strip, the side sealing molding, etc., which causes additional problems.

[0006] Even when silicone grease with improved water washout characteristics and low temperature storage performance is used to reduce the above problems, the problem of base oil separation during long-term use may still occur due to poor long-term lubricity. In addition, even glycol base oils with improved water washout characteristics, low temperature storage performance and long-term lubricity are difficult to apply to interior parts due to their unique discoloration.

[0007] Therefore, there is a need to develop a grease composition applied to various parts / environments that has not only improved long-term lubricity and water washout characteristics but also improved low-temperature storage and discoloration resistance. Summary of the invention

[0008] The present disclosure has been made to solve the above-mentioned problems occurring in the prior art while keeping the advantages achieved by the prior art intact.

[0009] One aspect of the present disclosure provides a grease composition and a method for preparing the same, the grease composition having improved long-term lubricity and water washout properties for use in an environment with frequent moisture inflow, and also having improved low-temperature storage performance and discoloration resistance for application to various parts.

[0010] The technical problems to be solved by the present disclosure are not limited to the above-mentioned problems, and any other technical problems not mentioned herein will be clearly understood by those skilled in the art to which the present disclosure belongs from the following description.

[0011] According to one aspect of the present disclosure, a grease composition comprises a base oil, a thickener and a styrene-based block copolymer containing ethylene-α-olefin copolymer repeating units as a first polymer additive, wherein the grease composition comprises 1.5 to 15% by weight of the first polymer additive based on the total weight of the grease composition.

[0012] According to another aspect of the present disclosure, a method for preparing a grease composition includes stirring a mixture (S1) of a base oil, a thickener and a styrene-based block copolymer containing ethylene-α-olefin copolymer repeating units as a first polymer additive at a temperature in the range of 130 to 180° C., wherein the content of the first polymer additive in the mixture is 1.5 to 15% by weight based on the total weight of the mixture. DETAILED DESCRIPTION

[0013] Hereinafter, the grease composition and the preparation method thereof will be described in detail so that those skilled in the art can easily implement them.

[0014] According to one embodiment of the present disclosure, the grease composition may include a base oil, a thickener, and a styrene-based block copolymer including ethylene-α-olefin copolymer repeating units as a first polymer additive.

[0015] The base oil is the most basic component of the grease composition and is included to minimize the change in viscosity of the grease according to temperature. In addition, the thickener is a component that can be dispersed in the base oil to improve the physical properties of the grease, such as heat resistance and water resistance.

[0016] As one of the core components of the present disclosure, the first polymer additive may include a styrene-based block copolymer including ethylene-α-olefin copolymer repeating units.

[0017] The styrene-based block copolymer containing ethylene-α-olefin copolymer repeating units may include at least one selected from the group consisting of: styrene-ethylene-propylene (SEP) copolymers, styrene-ethylene-butylene (SEB) copolymers, styrene-ethylene-butylene-styrene (SEBS) copolymers and styrene-ethylene-propylene-styrene block (SEPS) copolymers, preferably, may include at least one selected from the group consisting of styrene-ethylene-propylene (SEP) copolymers and styrene-ethylene-butylene (SEB) copolymers, and more preferably, may include styrene-ethylene-propylene (SEP) copolymers.

[0018] The grease composition of the present disclosure may include 1.5% to 15% by weight of the first polymer additive based on the total weight of the grease composition. By including the first polymer additive within the above range, the grease composition simultaneously improves long-term lubricity and water flushing properties, thereby preventing damage to parts by inhibiting grease separation caused by the inflow of external moisture and preventing discoloration of parts to prevent aesthetic degradation.

[0019] The long-term lubricity disclosed in the present disclosure refers to the performance of suppressing the separation of the base oil and the thickener. Therefore, when the long-term lubricity is improved, the separation of the base oil and the thickener is suppressed so that the lubricity does not decrease even when the grease is used for a long time. In addition, the water flushing property disclosed in the present disclosure refers to the property that the grease can adhere to the parts without being separated from the parts (even if external water flows in).

[0020] According to one embodiment of the present disclosure, the grease composition may further include as a second polymer additive at least one selected from the group consisting of olefin copolymers (OCP), hydrogenated styrene diblock copolymers (HSD), polyethylene wax (PE wax) and polypropylene wax (PP wax) together with the first polymer additive.

[0021] The grease composition of the present disclosure may include 1.5% to 15% by weight of the second polymer additive based on the total weight of the grease composition. By including the second polymer additive within the above range, the grease composition can simultaneously improve long-term lubricity and water flushing properties, similar to when the first polymer additive is added. In particular, when the first polymer additive and the second polymer additive are added at the same time, the separation resistance (long-term lubricity) and water flushing properties are further improved, so that the grease may not be separated from the parts, and the loss of grease due to the influx of external moisture can be effectively prevented.

[0022] The separation resistance disclosed in the present disclosure refers to a property that grease adheres to a component and does not separate, that is, a property directly related to long-term separation resistance.

[0023] When the first polymer additive and the second polymer additive are added simultaneously, a weight ratio of the first polymer additive to the second polymer additive may be 1:1 to 2:1.

[0024] When the weight ratio of the first polymer additive to the second polymer additive is within the above range, both long-term lubricity and water flushing characteristics can be improved, but when the content of the second polymer additive is excessive compared to the content of the first polymer additive, since the separation resistance (long-term lubricity) is reduced, grease may separate from the components to cause damage to the components.

[0025] The base oil may include at least one selected from the group consisting of petroleum, silicone base oil, aliphatic hydrocarbon oil and aromatic hydrocarbon oil, preferably, may be at least one selected from the group consisting of mineral oil, poly-α-olefin (PAO), alkylbenzene, alkylnaphthalene, polyethylene ether, polyalkylene glycol, polycarbonate, polyol ester, ethylene α-olefin copolymer, polybutene, aromatic ester, hindered ester, dibasic ester, paraffinic petroleum oil and naphthenic petroleum oil, and more preferably, may be at least one selected from the group consisting of alkylbenzene and alkylnaphthalene.

[0026] The thickener may include a lithium-based thickener. The lithium-based thickener may be obtained by reacting lithium hydroxide with a fatty acid compound, and may include a fatty acid lithium soap chain structure containing an aliphatic hydrocarbon group.

[0027] The grease composition of the present disclosure may include 60 to 90% by weight of the base oil and 2 to 35% by weight of the thickener, based on the total weight of the grease composition.

[0028] When the content of the base oil is small, the grease may be over-solidified and the practicality may be reduced. On the other hand, when the content of the base oil is excessive, the long-term lubricity may be reduced and liquefaction may occur at high temperatures. In addition, when the content of the thickener is small, the viscosity of the grease may be reduced and the grease may be easily separated from the parts. On the other hand, when the content of the thickener is excessive, the grease may be over-solidified.

[0029] According to one embodiment of the present disclosure, when necessary, the grease composition may further include at least one selected from the group consisting of: extreme pressure additives, antioxidants, corrosion inhibitors, anti-wear agents, metal passivators and viscosity index improvers as general additives. When general additives are added, the grease composition of the present disclosure may include 1% to 5% by weight of the general additives based on the total weight of the grease composition.

[0030] The extreme pressure additive may be added to improve load resistance and extreme pressure characteristics, and an organic metal-based extreme pressure additive, a sulfur-based extreme pressure additive, a phosphoric acid-based extreme pressure additive, a halogen-based extreme pressure additive, or the like may be used.

[0031] Antioxidants may include amine-based compounds such as phenyl-1-naphthylamine, phenyl-2-naphthylamine, diphenyl-p-phenylenediamine, dipyridylamine, phenothiazine, N-methylphenothiazine, N-ethylphenothiazine, 3,7-dioctylphenothiazine, p-, p-dioctyldiphenylamine, N,N'-diisopropyl-p-phenylenediamine and N,N'-di-sec-butyl-p-phenylenediamine; phenol-based compounds such as 2,6-di(tert-butyl)phenol; and their organometallic compounds.

[0032] Corrosion inhibitors can use ammonium salts of organic sulfonic acids; organic sulfonates or organic carboxylates of alkaline earth metals; hydroxy fatty acids such as oleoyl sarcosine; mercapto fatty acids such as 1-mercapto stearic acid; imidazoles such as thiazoles, 2-(decyldithio)-benzimidazole and benzimidazole; phosphates such as trisnonylphenyl phosphite; thiocarboxylates such as dilauryl thiopropionate, nitrites, etc.

[0033] The anti-wear agent may be phosphate ester, phosphite ester, phosphate amine salt, molybdenum dithiocarbamate, zinc dialkyl dithiophosphate, and the like.

[0034] In addition, metal deactivators and viscosity index improvers may be used as needed.

[0035] The type and content of general additives may be controlled based on the purpose and function of the part where the grease is to be used.

[0036] Next, a method for preparing a grease composition according to another embodiment of the present disclosure will be described in detail.

[0037] According to one embodiment of the present disclosure, a method for preparing a grease composition may include stirring a mixture (S1) of a base oil, a thickener and a styrene-based block copolymer containing ethylene-α-olefin copolymer repeating units as a first polymer additive at a temperature in the range of 130 to 180°C, preferably, may include stirring the mixture at a temperature in the range of 140 to 170°C, and more preferably, may include stirring the mixture at a temperature in the range of 150 to 160°C.

[0038] By stirring the mixture within the above temperature range, the first polymer additive can be uniformly dispersed in the grease, and the long-term lubricity and water washout properties of the grease can be effectively improved.

[0039] The styrene-based block copolymer containing ethylene-α-olefin copolymer repeating units may include at least one selected from the group consisting of: styrene-ethylene-propylene (SEP) copolymers, styrene-ethylene-butylene (SEB) copolymers, styrene-ethylene-butylene-styrene (SEBS) copolymers, and styrene-ethylene-propylene-styrene block (SEPS) copolymers, preferably, may include at least one selected from the group consisting of styrene-ethylene-propylene (SEP) copolymers and styrene-ethylene-butylene (SEB) copolymers, and more preferably, include styrene-ethylene-propylene (SEP) copolymers.

[0040] The mixture may include 1.5 to 15% by weight of the first polymer additive based on the total weight of the mixture. By including the first polymer additive within the above range, the mixture simultaneously improves long-term lubricity and water washout characteristics, thereby preventing damage to parts by inhibiting grease separation caused by the inflow of external moisture, and preventing discoloration of parts to prevent aesthetic deterioration.

[0041] Step S1 may include first mixing a base oil with a thickener (S11) and further mixing a styrene-based block copolymer containing ethylene-α-olefin copolymer repeating units with the mixture obtained in S11 (S12). More specifically, step S1 may include first mixing a base oil with a thickener (S100), then adding Li to the mixture obtained in step S100 for saponification (S110), and further mixing a styrene-based block copolymer containing ethylene-α-olefin copolymer repeating units with the mixture subjected to saponification in S110 (S120).

[0042] In step S110 , the saponification reaction may be performed at a temperature in the range of 60 to 100° C., preferably in the range of 70 to 90° C., and more preferably at 80° C. The saponification reaction may be performed by dissolving the acid component of the thickener in the above temperature range and then adding Li.

[0043] According to one embodiment of the present disclosure, the method for preparing a grease composition may further include cooling the mixture obtained in step S1 to 25° C. after step S1 ( S2 ). A final grease composition product may be prepared by cooling the mixture.

[0044] In one example, the mixture in step S1 may further include at least one selected from the group consisting of olefin copolymer (OCP), hydrogenated styrene diblock copolymer (HSD), polyethylene wax (PE wax) and polypropylene wax (PP wax) as the second polymer additive.

[0045] The mixture of step S1 may contain 1.5% to 15% by weight of the second polymer additive based on the total weight of the mixture. By containing the second polymer additive within the above range, the mixture can simultaneously improve long-term lubricity and water washing characteristics, similar to when the first polymer additive is added. In particular, when the first polymer additive and the second polymer additive are added at the same time, the separation resistance (long-term lubricity) and the water washing characteristics are further improved, thereby preventing the grease from separating from the parts and effectively preventing the loss of grease due to the inflow of external moisture.

[0046] Hereinafter, the present disclosure will be described in more detail by way of examples. However, such examples are only intended to help understand the present disclosure, and the scope of the present disclosure is not limited to such examples in any way.

[0047] Example 1: Preparation of Grease Composition 1

[0048] First, 88% by weight of an alkylbenzene base oil and 8% by weight of a lithium-based thickener are mixed with each other, and then lithium stearate is added to the mixture to perform a saponification reaction at 80° C., and then 2% by weight of a first polymer additive is stirred at 150° C. as a polymer additive, and then 2% by weight of a general additive is further mixed with the mixture, and then the product is cooled to 25° C. through a homogenization process to prepare a grease composition.

[0049] Here, a product named FHL50 (Isu Chemical) was used as an alkylbenzene base oil, a product named Lithium-12-hydroxy-stearat (BAERLOCHER) was used as a lithium-based thickener, a product named Kraton G 1740 (as a styrene-ethylene-propylene (SEP) copolymer) was used as a first polymer additive, a product named Lubrizol 2292B (as a corrosion inhibitor) was used as a general additive, and a product named Lubrizol 1395 was used as an anti-wear agent.

[0050] Example 2: Preparation of Grease Composition 2

[0051] It was prepared in the same manner as in Example 1 except that 87 wt % of the alkylbenzene base oil and 3 wt % of the first polymer additive as the polymer additive were added.

[0052] Example 3: Preparation of Grease Composition 3

[0053] It was prepared in the same manner as in Example 1 except that 85 wt % of the alkylbenzene base oil and 5 wt % of the first polymer additive were added as the polymer additive.

[0054] Example 4: Preparation of Grease Composition 4

[0055] It was prepared in the same manner as in Example 1 except that 80 wt % of the alkylbenzene base oil and 10 wt % of the first polymer additive were added as the polymer additive.

[0056] Example 5: Preparation of Grease Composition 5

[0057] It was prepared in the same manner as Example 1 except that 7 wt % of a lithium-based thickener and, as polymer additives, 1.5 wt % of a first polymer additive and 1.5 wt % of a second polymer additive were added.

[0058] Here, a product named Kraton G 1740 (styrene-ethylene-propylene (SEP) copolymer) was used as the first polymer additive, and a product named Lubrizol 2019 (olefin copolymer (OCP)) was used as the second polymer additive.

[0059] Example 6: Preparation of Grease Composition 6

[0060] It was prepared in the same manner as in Example 5, except that a product named Lubrizol 7306 (as a hydrogenated styrene diblock copolymer (HSD)) was used as the second polymer additive.

[0061] Example 7: Preparation of Grease Composition 7

[0062] It was prepared in the same manner as in Example 5, except that a product named Lionchemtech LC 106 (as polyethylene wax (PE wax)) was used as the second polymer additive.

[0063] Example 8: Preparation of Grease Composition 8

[0064] It was prepared in the same manner as in Example 5, except that a product named Lionchemtech LC 502 (as polypropylene wax (PP wax)) was used as the second polymer additive.

[0065] Comparative Example 1: Preparation of Grease Composition 9

[0066] It was prepared in the same manner as Example 1 except that 10 wt % of a lithium-based thickener was added and no polymer additive was added.

[0067] Comparative Example 2: Preparation of Grease Composition 10

[0068] It was prepared in the same manner as in Example 1 except that a product named Daelim PB2400 (as polybutene (PB)) was used as the first polymer additive.

[0069] Comparative Example 3: Preparation of Grease Composition 11

[0070] It was prepared in the same manner as in Example 1 except that a product named Lubrizol 7306 (as a hydrogenated styrene diblock copolymer (HSD)) was used as the first polymer additive.

[0071] Comparative Example 4: Preparation of Grease Composition 12

[0072] It was prepared in the same manner as in Example 1 except that 89 wt % of the alkylbenzene base oil and 1 wt % of the first polymer additive as the polymer additive were added.

[0073] Comparative Example 5: Preparation of Grease Composition 13

[0074] It was prepared in the same manner as in Example 1, except that 1.5% by weight of the first polymer additive and 1.5% by weight of the second polymer additive were added as the polymer additive.

[0075] Here, a product named Kraton G 1740 (as a styrene-ethylene-propylene (SEP) copolymer) was used as the first polymer additive, and a product named Kraton D 1161 (as a styrene-isoprene-styrene (SIS) copolymer) was used as the second polymer additive.

[0076] Comparative Example 6: Preparation of Grease Composition 14

[0077] It was prepared in the same manner as in Comparative Example 6 except that a product named Kraton G 1652 (as a styrene-ethylene-butylene-styrene (SEBS) copolymer) was used as the second polymer additive.

[0078] Comparative Example 7: Preparation of Grease Composition 15

[0079] It was prepared in the same manner as in Comparative Example 6 except that a product named Kraton D SBS (as a styrene-butylene-styrene (SBS) copolymer) was used as the second polymer additive.

[0080] Comparative Example 8: Preparation of Grease Composition 16

[0081] It was prepared in the same manner as in Comparative Example 6 except that a product named Kuraray LIR as liquefied isoprene rubber (LIR) was used as the second polymer additive.

[0082] Comparative Example 9: Preparation of Grease Composition 17

[0083] It was prepared in the same manner as in Comparative Example 6, except that a product named Lubrizol 2006E (as a copolymer ester) was used as the second polymer additive.

[0084] Experimental Example 1: Evaluation of water washing characteristics

[0085] The water washing property was evaluated at a test temperature of 25° C. For this, as a result of the water washing property evaluation, water resistance having a loss rate of 0.5% by weight or less was evaluated as very good, water resistance having a loss rate of 0.7% by weight or less was evaluated as good, water resistance having a loss rate of more than 0.7% by weight was evaluated as poor, and water resistance having a loss rate of 1.0% by weight or more was evaluated as very poor.

[0086] As a result of the evaluation, Example 1 was found to be good, and Examples 2 to 4 were found to be very good. Thus, it can be seen that when the first polymer additive is used and the content thereof is equal to or greater than 3% by weight, the water washing property is significantly improved.

[0087] In addition, it was also found that the evaluation results of Examples 5 to 8 were very good. Therefore, it can be seen that when at least one selected from the group consisting of an olefin copolymer (OCP), a hydrogenated styrene diblock copolymer (HSD), a polyethylene wax (PE wax) and a polypropylene wax (PP wax) is further included together with the first polymer additive, the water washing property is significantly improved.

[0088] However, Comparative Example 1 in which no polymer additive was added was evaluated to have very poor water washing characteristics, and Comparative Examples 5 to 8 in which styrene-isoprene-styrene (SIS) copolymer and liquefied isoprene rubber (LIR) were used as the second polymer additive were evaluated to have poor water washing characteristics. In addition, Comparative Example 2 in which polybutene (PB) was used as the first polymer additive and Comparative Example 4 in which the first polymer additive was added in a small amount of 1% by weight were evaluated to be poor.

[0089] Experimental Example 2: Long-term lubricity evaluation

[0090] As long-term lubricity, the degree (%) of oil separation when evaluation was performed at 100° C. for 24 hours based on ASTM D6184 (separation of oil from grease) was evaluated. In this regard, as a result of the long-term lubricity evaluation, an oil separation degree of 0.3% or less was evaluated as very good, an oil separation degree of 0.5% or less was evaluated as good, an oil separation degree of more than 0.5% was evaluated as poor, and an oil separation degree of 1.0% or more was evaluated as very poor.

[0091] As a result of the evaluation, it was found that all of Examples 1 to 8 were good. In other words, it can be seen that when the first polymer additive was used, the long-term lubricity was improved.

[0092] However, Comparative Example 1 in which no polymer additive was added and Comparative Examples 5 to 8 using styrene-isoprene-styrene (SIS) copolymer, styrene-ethylene-butylene-styrene (SEBS) copolymer, styrene-butylene-styrene (SBS) copolymer and liquefied isoprene rubber (LIR) as the second polymer additive were evaluated to have very poor long-term lubricity. In addition, Comparative Examples 2 and 3 using polybutene (PB) and hydrogenated styrene diblock copolymer (HSD) as the first polymer additive were found to have poor long-term lubricity, and Comparative Example 9 using copolymer ester as the second polymer additive was evaluated to have very poor long-term lubricity.

[0093] Table 1 below is a table summarizing the results of the water washout characteristics and long-term lubricity evaluations.

[0094] Table 1

[0095]

[0096]

[0097] According to one embodiment of the present disclosure, a grease composition and a method for preparing the same can be provided, which can improve all of long-term lubricity, water washout characteristics, low-temperature storage performance, and discoloration resistance by optimizing the type and content of polymer additives to be applied to various conditions / parts such as environments with frequent moisture inflow.

[0098] Hereinabove, although the present disclosure has been described with reference to exemplary embodiments, the present disclosure is not limited thereto but various modifications and changes may be made by those skilled in the art to which the present disclosure pertains without departing from the spirit and scope of the present disclosure as claimed in the appended claims.

Claims

1. A grease composition comprising: Base oil; Thickeners; and a styrene-based block copolymer containing ethylene-α-olefin copolymer repeating units as a first polymer additive; in, The grease composition includes 1.5 to 15% by weight of the first polymer additive based on the total weight of the grease composition.

2. The grease composition according to claim 1, wherein The styrene-based block copolymer containing the ethylene-α-olefin copolymer repeating unit includes at least one selected from the group consisting of styrene-ethylene-propylene copolymer, styrene-ethylene-butylene copolymer, styrene-ethylene-butylene-styrene copolymer and styrene-ethylene-propylene-styrene block copolymer.

3. The grease composition according to claim 1, further comprising: As the second polymer additive, at least one selected from the group consisting of an olefin copolymer, a hydrogenated styrene diblock copolymer, a polyethylene wax, and a polypropylene wax.

4. The grease composition according to claim 3, wherein The grease composition includes 1.5 to 15% by weight of the second polymer additive based on the total weight of the grease composition.

5. The grease composition according to claim 3, wherein The weight ratio of the first polymer additive to the second polymer additive is 1:1 to 2:

1.

6. The grease composition according to claim 1, wherein The base oil includes at least one selected from the group consisting of petroleum, silicone base oil, aliphatic hydrocarbon oil, and aromatic hydrocarbon oil.

7. The grease composition according to claim 1, wherein The thickener includes a lithium-based thickener.

8. The grease composition according to claim 1, wherein The grease composition comprises 60 to 90% by weight of the base oil based on the total weight of the grease composition, and wherein the grease composition comprises 2 to 35% by weight of the thickener.

9. The grease composition according to claim 1, further comprising: As the general additive, at least one selected from the group consisting of an extreme pressure additive, an antioxidant, a corrosion inhibitor, an antiwear agent, a metal deactivator and a viscosity index improver.

10. The grease composition according to claim 9, wherein The grease composition comprises 1 to 5% by weight of the general additive based on the total weight of the grease composition.

11. A method for preparing a grease composition, the method comprising: stirring a mixture of a base oil, a thickener, and a styrene-based block copolymer containing ethylene-α-olefin copolymer repeating units as a first polymer additive at a temperature in the range of 130 to 180° C.; Wherein, the content of the first polymer additive in the mixture is 1.5 to 15% by weight based on the total weight of the mixture.

12. The method according to claim 11, wherein: The styrene-based block copolymer containing the ethylene-α-olefin copolymer repeating unit includes at least one selected from the group consisting of styrene-ethylene-propylene copolymer, styrene-ethylene-butylene copolymer, styrene-ethylene-butylene-styrene copolymer and styrene-ethylene-propylene-styrene block copolymer.

13. The method according to claim 11, wherein: The stirring comprises: First, the base oil is mixed with the thickener; and The styrene-based block copolymer containing the ethylene-α-olefin copolymerized repeating unit is separately mixed with the mixture obtained in the mixing of the base oil and the thickener.

14. The method according to claim 11, wherein: The stirring comprises: First, the base oil is mixed with the thickener; A saponification reaction is performed by adding Li to a mixture of a base oil and a thickener; and Separately, a styrene-based block copolymer containing the ethylene-α-olefin copolymer repeating unit is mixed with the mixture subjected to the saponification reaction.

15. The method according to claim 14, wherein: The saponification reaction is carried out at a temperature ranging from 60°C to 100°C.

16. The method according to claim 11, further comprising: The mixture was cooled to 25 °C.

17. The method according to claim 11, wherein: The mixture further comprises, as a second polymer additive, at least one selected from the group consisting of an olefin copolymer, a hydrogenated styrene diblock copolymer, a polyethylene wax, and a polypropylene wax.

18. The method according to claim 17, wherein: The mixture includes 1.5 to 15% by weight of the second polymer additive, based on the total weight of the mixture.

Images