Grease composition

Abstract

To provide a grease composition excellent in water resistance.SOLUTION: A grease composition comprises: a lubricant base oil; at least one compound selected from a group consisting of lithium soap and lithium complex soap as a thickener; and fatty acid zinc represented by a following formula (1) as a metal detergent. The fatty acid zinc represented by formula (1) includes fatty acid zinc in which at least one of R1 and R2 is an isostearyl group. In formula (1), each of R1 and R2 independently represents a branched chain aliphatic hydrocarbon group having 8 to 18 carbon atoms.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a grease composition. [Background technology]

[0002] Vehicles such as automobiles, trucks, bicycles, and the like are used in all kinds of environments and may be exposed to, for example, rainwater. If a vehicle is continuously used in such an environment where it comes into contact with water, and a grease composition that is not water resistant is used in the bearings, the grease composition may leak from the bearings.

[0003] Generally, the grease composition used in the wheel bearings of vehicles is a lithium soap or lithium complex soap grease, but such grease is subjected to frictional heat from the brakes or bearings and is constantly exposed to high temperatures during driving. In addition, the grease composition is subjected to shear due to the intense agitation caused by the rotation of the bearing, and if the shear stability is insufficient, it may soften. In extreme cases, long-term use may lead to grease leakage.

[0004] Therefore, in the field of lubricating oils such as grease compositions used under such conditions of exposure to water or heat, further improvement in water resistance or heat resistance is desired, and attempts have been made to improve them through blending techniques of base oils and additives (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2009-46625 A [Patent Document 2] JP 2001-247888 A DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0006] As described above, improved water resistance is required for grease compositions. Zinc naphthenate is sometimes used to improve the water resistance of grease compositions, but since naphthenic acid, which is the raw material, is a by-product extracted by refining crude oil, it is difficult to technically control the performance, including water resistance.

[0007] The present disclosure has been made in consideration of the above-mentioned circumstances, and an object of one embodiment of the present disclosure is to provide a grease composition having excellent water resistance. [Means for solving the problem]

[0008] As a result of intensive research into solving the above problems, the present inventors have found that water resistance can be improved by including a fatty acid zinc salt having a specific structure as a metal detergent in a grease composition. That is, the means for solving the above problems include the following embodiments.

[0009] <1> A grease composition comprising a lubricating base oil, at least one compound selected from the group consisting of lithium soaps and lithium complex soaps as a thickener, and a fatty acid zinc salt represented by the following formula (1) as a metal detergent, wherein the fatty acid zinc salt represented by formula (1) includes a fatty acid zinc salt in which at least one of R1 and R2 is an isostearyl group.

[0010] [ka]

[0011] In formula (1), R1 and R2 each independently represent a branched chain aliphatic hydrocarbon group having 8 to 18 carbon atoms.

[0012] <2> The fatty acid zinc represented by the above formula (1) includes a fatty acid zinc in which at least one of R1 and R2 is a 2-ethylhexyl group. <1> The grease composition according to claim 1. <3> The fatty acid zinc represented by the above formula (1) includes a fatty acid zinc in which at least one of R1 and R2 is a neodecanyl group. <1> or <2> The grease composition according to claim 1. <4> The content of the fatty acid zinc salt represented by the above formula (1) is 0.5% by mass to 3.0% by mass relative to the total mass of the grease composition. <1> ~ <3> 13. The grease composition according to claim 12 . Effect of the Invention

[0013] According to one embodiment of the present disclosure, a grease composition having excellent water resistance is provided. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Specific embodiments of the grease composition according to the present disclosure will be described in detail below. However, the grease composition according to the present disclosure is not limited to the following embodiments and can be modified as appropriate within the scope of the object of the present disclosure.

[0015] In the present disclosure, a numerical range indicated using "~" means a range that includes the numerical values ​​before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described in stages in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In addition, in the numerical ranges described in this specification, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples. In the present disclosure, combinations of two or more preferred embodiments are more preferred embodiments. In the present disclosure, "mass %" and "weight %" are synonymous. In the present disclosure, when there are multiple substances corresponding to each component, the amount of each component means the total amount of the multiple substances, unless otherwise specified. In this disclosure, "JIS" is used as an abbreviation for Japanese Industrial Standards.

[0016] [Grease composition] The grease composition according to the present disclosure contains a lubricating oil base oil, at least one compound selected from the group consisting of lithium soaps and lithium complex soaps as a thickener, and a fatty acid zinc salt represented by the following formula (1) as a metal detergent, wherein the fatty acid zinc salt represented by formula (1) includes a fatty acid zinc salt in which at least one of R1 and 2 is an isostearyl group.

[0017] [ka]

[0018] In formula (1), R1 and R2 each independently represent a branched chain aliphatic hydrocarbon group having 8 to 18 carbon atoms.

[0019] Hereinafter, the fatty acid zinc represented by formula (1) is also referred to as "specific fatty acid zinc", and among the specific fatty acid zinc, the fatty acid zinc in which at least one of R1 and R2 is an isostearyl group is also referred to as "specific fatty acid zinc A". In the following description, at least one compound selected from the group consisting of lithium soaps and lithium complex soaps is also referred to as a "specific thickener" as appropriate.

[0020] The grease composition according to the present disclosure is a grease composition containing a lubricating oil base oil, a specific thickener as a thickener, and a specific fatty acid zinc as a metal detergent, and the specific fatty acid zinc contains specific fatty acid zinc A, thereby improving water resistance. The reason for this is not clear, but is presumed to be as follows.

[0021] The thickener contained in the grease composition according to the present disclosure is at least one compound (specific thickener) selected from the group consisting of lithium soap and lithium complex soap. Therefore, water mixed into the grease composition acts to form micelles with the specific thickener according to the present disclosure, which is one form of metal soap. As a result, the thickener fiber structure in the grease composition collapses, causing softening of the consistency. Softening of the consistency in the grease composition can cause, for example, grease leakage from bearings.

[0022] In contrast, the grease composition according to the present disclosure contains, as a metal detergent, a fatty acid zinc (specific fatty acid zinc) represented by formula (1), and the specific fatty acid zinc includes a fatty acid zinc (specific fatty acid zinc A) in which at least one of R1 and R2 in formula (1) is an isostearyl group. The specific fatty acid zinc, which is a metal detergent, can finely disperse water mixed into the grease composition and form micelles, and it is presumed that by forming micelles preferentially over the thickener, it suppresses the destruction of the thickener fiber structure caused by the mixing of water. Furthermore, it is presumed that the specific fatty acid zinc includes the specific fatty acid zinc A having an isostearyl group with a long alkyl chain length, which contributes to more firmly forming micelles between water and the specific fatty acid zinc A, and more effectively suppressing the softening of the consistency.

[0023] Furthermore, in one embodiment of the grease composition according to the present disclosure, the specific fatty acid zinc preferably includes a fatty acid zinc in which at least one of R1 and R2 in the formula (1) is a 2-ethylhexyl group (hereinafter also referred to as "specific fatty acid zinc B"). In another embodiment, the specific fatty acid zinc preferably includes a fatty acid zinc in which at least one of R1 and R2 in the formula (1) is a neodecanyl group (hereinafter also referred to as "specific fatty acid zinc C"). The specific fatty acid zinc B and the specific fatty acid zinc C may each be a fatty acid zinc corresponding to the specific fatty acid zinc A, or may be a fatty acid zinc having a structure different from that of the specific fatty acid zinc A. It is presumed that the water resistance of the grease composition is more stably improved by the presence of an isostearyl group and a 2-ethylhexyl group and / or a neodecanyl group (preferably the presence of an isostearyl group, a 2-ethylhexyl group, and an odecane group) in the specific fatty acid zinc.

[0024] <Lubricant base oil> The grease composition according to the present disclosure comprises a lubricating base oil. The lubricating base oil is not particularly limited and may be, for example, a mineral oil, a synthetic oil, or a mixture thereof. The lubricating base oil may be used alone or in combination of two or more.

[0025] Examples of mineral oils include those obtained by refining lubricating oil fractions of crude oil through an appropriate combination of refining methods such as solvent refining, hydrorefining, hydrocracking refining, hydrodewaxing, etc. Examples of mineral oils include paraffinic mineral oils that are highly refined by subjecting hydrorefined oils, catalytic isomerized oils, etc. to treatments such as solvent dewaxing or hydrodewaxing.

[0026] Examples of synthetic oils include ether-based synthetic oils such as alkyl diphenyl ethers; ester-based synthetic oils such as diesters, polyol esters, and complex-type polyol esters; synthetic hydrocarbon oils such as polyalphaolefins; and alkyl naphthalene-based synthetic oils.

[0027] The kinematic viscosity of lubricating base oil at 40°C is 1mm2 / s~1000mm 2 / s is preferred, and 1 mm 2 / s~500mm 2 / s. The kinematic viscosity of the base oil is 1mm 2 / s~1000mm 2 / s, the grease composition is particularly suitable for use in wheel bearings.

[0028] In this disclosure, the kinematic viscosity at 40° C. of the lubricating base oil refers to a value measured according to JIS K 2283:2000 “Kinematic Viscosity Testing Method”.

[0029] <Thickener> The grease composition according to the present disclosure contains at least one compound (specific thickener) selected from the group consisting of lithium soaps and lithium complex soaps.

[0030] Lithium soap is a lithium salt of a higher fatty acid. Lithium complex soap is a complex soap that combines a lithium salt of a higher fatty acid and a lithium salt of a dicarboxylic acid.

[0031] From the viewpoint of heat resistance, the lithium soap is preferably a lithium salt of a monocarboxylic acid having 12 to 24 carbon atoms. From the viewpoint of heat resistance, the lithium complex soap is preferably a complex of a lithium salt of a monocarboxylic acid having 12 to 24 carbon atoms and a lithium salt of a dicarboxylic acid having 2 to 12 carbon atoms. Suitable monocarboxylic acids include stearic acid, 12-hydroxystearic acid, and the like. Suitable dicarboxylic acids include succinic acid, malonic acid, adipic acid, pime acid, and the like. Examples include phosphoric acid, azelaic acid, and sebacic acid.

[0032] As the specific thickener, lithium soap is more preferable in terms of availability and ease of handling.

[0033] The content of the specific thickener can be appropriately adjusted according to the desired worked penetration, and is preferably 5% by mass to 20% by mass, and more preferably 5% by mass to 15% by mass, relative to the total mass of the grease composition.

[0034] <Metal cleaning agent> The grease composition according to the present disclosure contains, as a metal detergent, a fatty acid zinc salt (specific fatty acid zinc salt) represented by the following formula (1): The specific fatty acid zinc salt includes a fatty acid zinc salt (specific fatty acid zinc salt A) in which at least one of R1 and R2 is an isostearyl group. The grease composition according to the present disclosure can improve water resistance by containing a specific fatty acid zinc salt, including specific fatty acid zinc salt A. The specific fatty acid zinc salt may be used alone or in combination of two or more kinds.

[0035] [ka]

[0036] In formula (1), R1 and R2 each independently represent a branched chain aliphatic hydrocarbon group having 8 to 18 carbon atoms. The branched chain aliphatic hydrocarbon group represented by R1 or R2 may be a saturated group or an unsaturated group, but is preferably a saturated group. Examples of the branched chain aliphatic hydrocarbon group having 8 to 18 carbon atoms include a 2-ethylhexyl group, a neodecanyl group, and an isostearyl group.

[0037] From the viewpoint of water resistance, the grease composition according to the present disclosure contains a specific fatty acid zinc (specific fatty acid zinc A) in which at least one of R1 and R2 is an isostearyl group. In the specific fatty acid zinc A, only one of R1 and R2 may be an isostearyl group, or both of R1 and R2 may be isostearyl groups.

[0038] The specific fatty acid zinc contained in the grease composition according to the present disclosure may be only specific fatty acid zinc A. In an embodiment in which the specific fatty acid zinc contains only specific fatty acid zinc A, the specific fatty acid zinc A is preferably zinc isostearate (i.e., a fatty acid zinc in which R1 and R2 are isostearyl groups). The specific fatty acid zinc may be a mixture of specific fatty acid zinc A and a fatty acid zinc other than specific fatty acid zinc A.

[0039] From the viewpoint of water resistance, the content of specific fatty acid zinc A in the specific fatty acid zinc is preferably 10% by mass to 100% by mass, more preferably 20% by mass to 85% by mass, and even more preferably 30% by mass to 70% by mass, relative to the total mass of the specific fatty acid zinc.

[0040] From the viewpoint of water resistance, the specific fatty acid zinc preferably contains specific fatty acid zinc A and fatty acid zinc (specific fatty acid zinc B) in which at least one of R1 and R2 is a 2-ethylhexyl group. In the specific fatty acid zinc B, only one of R1 and R2 may be a 2-ethylhexyl group, or both of R1 and R2 may be 2-ethylhexyl groups.

[0041] The specific fatty acid zinc B may be a fatty acid zinc corresponding to the specific fatty acid zinc A (that is, a fatty acid zinc in which one of R1 and R2 is an isostearyl group and the other is a 2-ethylhexyl group). The specific fatty acid zinc B may be a fatty acid zinc having a structure different from that of the specific fatty acid zinc A (i.e., a fatty acid zinc in which one of R1 and R2 is a 2-ethylhexyl group and the other is a branched chain aliphatic hydrocarbon group other than an isostearyl group).

[0042] In the case where the specific fatty acid zinc contains specific fatty acid zinc A and specific fatty acid zinc B, it is preferable that the specific fatty acid zinc is equivalent to a mixture of zinc isostearate and zinc 2-ethylhexanoate. In this case, the content ratio of the fatty acid zinc constituting the specific fatty acid zinc is preferably 1:1 to 2:1, more preferably 1.5:1 to 1.7:1, calculated as zinc isostearate (X) and zinc 2-ethylhexanoate (Y) (X:Y) on a mass basis.

[0043] From the viewpoint of water resistance, the specific fatty acid zinc more preferably includes specific fatty acid zinc A, specific fatty acid zinc B, and fatty acid zinc in which at least one of R1 and R2 is a neodecanyl group (specific fatty acid zinc C). In the specific fatty acid zinc C, only one of R1 and R2 may be a neodecanyl group, or both of R1 and R2 may be neodecanyl groups.

[0044] The specific fatty acid zinc C may be a fatty acid zinc corresponding to the specific fatty acid zinc A (that is, a fatty acid zinc in which one of R1 and R2 is an isostearyl group and the other is a neodecanyl group).

[0045] The specific fatty acid zinc C may be a fatty acid zinc corresponding to the specific fatty acid zinc B (that is, a fatty acid zinc in which one of R1 and R2 is a neodecanyl group and the other is a 2-ethylhexyl group).

[0046] The specific fatty acid zinc C may be a fatty acid zinc having a structure different from that of the specific fatty acid zinc A and the specific fatty acid zinc B (i.e., a fatty acid zinc in which one of R1 and R2 is a neodecanyl group and the other is a branched chain aliphatic hydrocarbon group other than an isostearyl group or a 2-ethylhexyl group).

[0047] In the case where the specific fatty acid zinc contains specific fatty acid zinc A, specific fatty acid zinc B, and specific fatty acid zinc A, it is preferable that the specific fatty acid zinc is equivalent to a mixture of zinc isostearate, zinc 2-ethylhexanoate, and zinc neodecanoate. In this case, the content ratio of the fatty acid zinc constituting the specific fatty acid zinc is preferably 1:1:1 to 2:1:1, more preferably 1.2:1:1 to 1.8:1:1, in terms of the converted ratio (X:Y:Z) of zinc isostearate (X), zinc 2-ethylhexanoate (Y), and zinc neodecanoate (Z) by mass.

[0048] From the viewpoint of water resistance, the total content of the specific fatty acid zinc salts is preferably 0.5 mass % to 3.0 mass %, and more preferably 1.0 mass % to 2.0 mass %, relative to the total mass of the grease composition.

[0049] <Other additives> The grease composition according to the present disclosure may contain other additives as necessary in addition to the above-mentioned base oil, specific thickener, and specific fatty acid zinc as a metal cleaner. As the other additives, additives such as antioxidants, corrosion inhibitors, rust inhibitors, and extreme pressure agents can be appropriately blended. The other additives may be used alone or in combination of two or more.

[0050] Examples of the antioxidant include alkylphenols such as 2,6-di-tert-butyl-p-cresol, bisphenols such as 4,4'-methylenebis-(2,6-di-t-butylphenol), phenolic compounds such as n-octadecyl-3-(4'-hydroxy-3',5'-di-t-butylphenol)propionate, aromatic amine compounds such as naphthylamines and dialkyldiphenylamines, and zinc thiophosphate compounds.

[0051] Corrosion inhibitors include benzotriazole, benzimidazole, and the like.

[0052] Examples of the rust inhibitor include metal sulfonate compounds and sorbitan compounds.

[0053] Examples of the extreme pressure agent include sulfurized olefins, sulfurized fats and oils, sulfurized esters, and polysulfides.

[0054] ~Properties of grease composition~ <Worked Penetration> The worked penetration of the grease composition is preferably 205-310, and more preferably 220-295.

[0055] ~Characteristics of grease composition (water resistance)~ The water resistance of the grease composition according to the present disclosure is evaluated in accordance with the wet roll stability test (ASTM D1831) and water wash resistance (79°C) (JIS K 2220:2013).

[0056] The grease composition according to the present disclosure preferably has a worked penetration change of 150 or less, more preferably 135 or less, and even more preferably 120 or less, in a water-containing roll stability test.

[0057] The grease composition according to the present disclosure preferably has a water wash resistance (79°C) of 20 or less, and more preferably 15 or less.

[0058] The grease composition according to the present disclosure preferably has both a water-containing roll stability test and water rinsing resistance (79° C.) within the above ranges.

[0059] -Method for preparing grease composition- The method for preparing the grease composition according to the present disclosure is not particularly limited, and the grease composition can be prepared by a conventionally known method. For example, the grease composition according to the present disclosure can be prepared by appropriately mixing other additive components as necessary in addition to the lubricating oil base oil, the specific thickener, and the specific fatty acid zinc salt as a metal detergent.

[0060] ~Target of use of grease composition~ The grease composition according to the present disclosure can be applied to bearings, etc. Since the grease composition according to the present disclosure has excellent water resistance, it can be particularly preferably applied to, for example, wheel bearings of vehicles. EXAMPLES

[0061] The grease composition according to the present disclosure will be specifically described below with reference to examples. Note that the grease composition according to the present disclosure is not limited to these examples in any way.

[0062] Details of each component contained in the grease composition are as follows:

[0063] (Metal cleaning agent) Metal cleaning agent is fatty acid zinc and mineral oil (kinematic viscosity at 40℃: 10mm 2 The zinc fatty acid used as the metal detergent was a zinc fatty acid obtained by reacting a fatty acid as a raw material with a zinc salt precursor all at once. In Table 1, the contents (mass%) of zinc isostearate, zinc neodecanoate, and zinc 2-ethylhexanoate indicate the contents (mass%) corresponding to the converted amounts of each of the zinc fatty acid zincs in the mixture. In Comparative Example 1, no metal detergent was used.

[0064] [Table 1]

[0065] Details of the preparation of the fatty acid zinc salt used as the metal detergent are given below.

[0066] -Preparation of metal cleaning agent- In Example 1, a zinc fatty acid zinc salt was obtained by reacting isostearic acid with a zinc salt precursor so that the amount of zinc isostearate in the mineral oil was 51% by mass. That is, the specific fatty acid zinc salt used in Example 1 is a fatty acid zinc salt in which both R1 and R2 in the formula (1) are isostearyl groups.

[0067] In Example 2, 2-ethylhexanoic acid, isostearic acid, and a zinc salt precursor were reacted at once to obtain a zinc fatty acid zinc salt in a mineral oil such that the content of the zinc fatty acid in the mineral oil was 15 mass% calculated as zinc 2-ethylhexanoate and 25 mass% calculated as zinc isostearate. That is, the specific fatty acid zinc salt used in Example 2 is a mixture of a fatty acid zinc salt in which both R1 and R2 in formula (1) are isostearyl groups, a fatty acid zinc salt in which both R1 and R2 are 2-ethylhexyl groups, and a fatty acid zinc salt in which one of R1 and R2 is an isostearyl group and the other is a 2-ethylhexyl group.

[0068] In Example 3, a zinc fatty acid was obtained by reacting 2-ethylhexanoic acid, neodecanoic acid, isostearic acid, and a zinc salt precursor all at once so that the contents in the mineral oil were 5% by mass calculated as zinc 2-ethylhexanoate, 5% by mass calculated as zinc neodecanoate, and 10% by mass calculated as zinc isostearate. That is, the specific fatty acid zinc used in Example 3 is a mixture of fatty acid zinc in which both R1 and R2 in formula (1) are isostearyl groups, fatty acid zinc in which both R1 and R2 are 2-ethylhexyl groups, fatty acid zinc in which both R1 and R2 are neodecanyl groups, fatty acid zinc in which one of R1 and R2 is an isostearyl group and the other is a 2-ethylhexyl group, fatty acid zinc in which one of R1 and R2 is an isostearyl group and the other is a neodecanyl group, and fatty acid zinc in which one of R1 and R2 is a 2-ethylhexyl group and the other is a neodecanyl group.

[0069] For Examples 4 to 8 and Comparative Examples 2 to 4, fatty acid zinc salts were obtained in the same manner as above.

[0070] (Lubricant base oil) Base oil: Solvent refined mineral oil (Kinematic viscosity at 40°C: 175mm 2 / s)

[0071] (Thickener) Thickener (lithium soap, lithium complex soap): The thickener was synthesized by mixing the raw materials for the thickener with the base oil and reacting the raw materials in the base oil using the following manufacturing procedure.

[0072] <Manufacturing procedure (lithium soap)> The base oil and 12-hydroxystearic acid as a thickener raw material were charged into a heat-resistant container, heated to about 90°C with stirring, and then an aqueous lithium hydroxide solution was added and the mixture was allowed to saponify for about 60 minutes.The mixture was then heated to 200°C with stirring to dissolve the lithium fatty acid salt, and then rapidly cooled to prepare the lithium grease.

[0073] <Manufacturing procedure (lithium complex soap)> A heat-resistant container was filled with base oil and 12-hydroxystearic acid as a thickener raw material, and after heating and stirring to about 90°C, lithium hydroxide aqueous solution was added and the mixture was allowed to saponify for about 60 minutes. The lithium hydroxide aqueous solution and azelaic acid were then added and reacted for about 60 minutes to produce a lithium complex soap. The mixture was then heated to 230°C with stirring, semi-melted, and then rapidly cooled to prepare a lithium complex grease.

[0074] (Other additives) Other additives include the following three components (total added amount: 1.03 mass %). 2,6-Di-tert-butyl-4-methylphenol 0.5% by mass Phenolic antioxidant (product name: Irganox L57, manufactured by BASF) ...0.5% by mass Corrosion inhibitor (product name: Chiolite B-1001, manufactured by Chiyoda Chemical Co., Ltd.) ... 0.03% by mass

[0075] [Examples 1 to 8, Comparative Examples 1 to 4] Each of the grease compositions of the Examples and Comparative Examples was prepared by mixing the components constituting the grease composition so as to obtain the composition shown in the composition column of Table 2. After the grease composition was prepared so as to contain a predetermined amount of each component, it was subjected to a milling process to uniformly disperse the thickener in the grease composition to obtain the final composition.

[0076] [Measurement and Evaluation] The following measurements and evaluations were carried out for each of the obtained grease compositions. The results are shown in Table 2.

[0077] (1) Worked Penetration The worked penetration was measured based on JIS K 2220:2013.

[0078] (2) Stability of wet roll A wet roll stability test was carried out based on ASTM D1831, and the results were evaluated according to the following criteria. -Test conditions- The moisture content of the sample was 10% by mass (45 g of grease composition, 5 g of water), the test temperature was 80°C, the test time was 2 hours, and the roll rotation speed was 165 rpm (revolutions per minute). The worked penetration of the grease composition after the test was measured. The difference in the worked penetration calculated by subtracting the worked penetration value before the test measured in (1) above from the worked penetration value of the grease composition after the test was taken as the change in the consistency. -Judgment criteria- A: The change in consistency is 120 or less. B: The change in consistency is greater than 120.

[0079] (3) Washing water resistance (79℃) The water resistance after washing (79°C) was measured according to JIS K 2220:2013. The evaluation was based on the following criteria. -Judgment criteria- A: The sample loss is less than 15. B: The amount of sample loss is greater than 15.

[0080] Regarding the evaluation of water resistance, when the evaluation results of both (2) water-containing roll stability and (3) water washing resistance (79° C.) were rated A, the grease composition was determined to have excellent water resistance.

[0081] [Table 2]

[0082] As shown in Table 2, the grease compositions of Examples 1 to 8, which contained a lubricating oil base oil, a specific thickener, and a specific fatty acid zinc salt including a fatty acid zinc salt in which at least one of R1 and R2 in formula (1) is an isostearyl group as a metal detergent, had excellent water resistance. In contrast, the grease composition of Comparative Example 1, which did not contain a fatty acid zinc salt as a metal detergent, was poor in both water-containing roll stability and water rinsing resistance (79°C), and was therefore poor in water resistance. In addition, the grease compositions of Comparative Examples 2 to 4, which did not contain a fatty acid zinc salt (specific fatty acid zinc salt A) in which at least one of R1 and R2 was an isostearyl group as a metal detergent, had good water resistance when washed with water (79°C), but did not have good water-containing roll stability and were poor in water resistance.

[0083] From the above, it can be seen that the grease composition according to the present disclosure has excellent water resistance.

Claims

1. A lubricating oil base oil; As a thickener, at least one compound selected from the group consisting of lithium soap and lithium complex soap; The metal detergent contains a fatty acid zinc salt represented by the following formula (1), The fatty acid zinc salt represented by the formula (1) is R １ and R ２ At least one of the above is an isostearyl group. Grease composition. 【Chemistry 1】 In formula (1), R １ and R ２ each independently represents a branched chain aliphatic hydrocarbon group having 8 to 18 carbon atoms.

2. The fatty acid zinc salt represented by the formula (1) is R １ and R ２ 2. The grease composition according to claim 1, comprising a fatty acid zinc salt, at least one of which is a 2-ethylhexyl group.

3. The fatty acid zinc salt represented by the formula (1) is R １ and R ２ 3. The grease composition according to claim 1 or claim 2, comprising a fatty acid zinc salt, at least one of which is a neodecanyl group.

4. The grease composition according to any one of claims 1 to 3, wherein the total content of the fatty acid zinc salts represented by the formula (1) is 0.5 mass % to 3.0 mass % relative to the total mass of the grease composition.

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