Grease composition

Abstract

To provide a grease composition exhibiting superior water resistance and superior rust prevention against salt water.SOLUTION: A grease composition comprising a base oil, a thickener containing a calcium soap and a lithium soap, a sorbitan fatty acid ester, and a zinc fatty acid.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] The objects to which a grease composition is to be used may be used in environments where they come into contact with water. For this reason, grease compositions focusing on water resistance have been proposed. For example, Patent Document 1 proposes "a grease composition comprising at least one base oil selected from mineral oil-based lubricating base oils and synthetic lubricating base oils, at least one thickener selected from calcium soap-based thickeners, calcium sulfonate complexes, and polyureas, and at least one thickener selected from lithium soap-based thickeners and lithium soap complex thickeners, in a blending mass ratio of 95:5 to 50:50, and having a worked penetration of 220 to 385." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-70461 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, some of the objects to which grease compositions are used are those that are used in environments exposed not only to rainwater but also to seawater (i.e., saltwater) (for example, ships, automobiles, fishing reels, etc.), and therefore there is a demand for grease compositions that have excellent water resistance and rust prevention properties against saltwater.

[0005] The present disclosure has been made in view of the above circumstances, and an object of one embodiment of the present disclosure is to provide a grease composition that has excellent water resistance and rust prevention properties against salt water. [Means for solving the problem]

[0006] The grease composition according to the present disclosure includes the following embodiments.

[0007] <1> A grease composition comprising a base oil, a thickener containing a calcium soap and a lithium soap, a sorbitan fatty acid ester, and a zinc fatty acid. <2> The base oil comprises at least one selected from the group consisting of polyalphaolefins and mineral oils; <1> or <2> The grease composition according to claim 1. <3> The sorbitan fatty acid ester is sorbitan monooleate. <1> or <2> The grease composition according to claim 1. <4> The fatty acid zinc salt contains a compound represented by the following formula (1): <1> ~ <3> 1. The grease composition according to claim 1 . [ka]

[0008] In formula (1), R1 and R2 each independently represent an aliphatic hydrocarbon group having 8 to 18 carbon atoms.

[0009] <5> The worked penetration is 355 or more. <1> ~ <4> 1. The grease composition according to claim 1 . [Effects of the Invention]

[0010] According to one embodiment of the present disclosure, a grease composition having excellent water resistance and rust prevention properties against salt water can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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 implemented with appropriate modifications within the scope of the object of the present disclosure.

[0012] In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the present disclosure, the upper or lower limit of a numerical range described in stages may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in the present disclosure, the upper or lower limit of a numerical range described in stages may be replaced with a value shown in the examples. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. 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. In this disclosure, "ASTM" refers to international standards developed by ASTM International.

[0013] [Grease composition] The grease composition according to the present disclosure contains a base oil, a thickener containing a calcium soap and a lithium soap, a sorbitan fatty acid ester, and a zinc fatty acid, which provides the grease composition with excellent water resistance and rust prevention properties against salt water.

[0014] On the other hand, Patent Document 1 does not focus on the inclusion of a base oil, a thickener containing calcium soap and lithium soap, a sorbitan fatty acid ester, and a zinc fatty acid in the grease composition.

[0015] Furthermore, in environments where grease compositions are used in environments where they are exposed to seawater, they are required to not only have excellent rust prevention properties against saltwater, but also to reduce the environmental impact in the event of a leak. While the use of barium sulfonate as an additive is one way to achieve high rust prevention, it is preferable to refrain from using barium sulfonate because it is an additive that has a high environmental impact. In contrast, the grease composition according to the present disclosure has the advantage of being able to exhibit excellent rust prevention properties against saltwater without using an additive that has a high environmental impact, such as barium sulfonate. Specifically, the grease composition according to the present disclosure contains a sorbitan fatty acid ester and a zinc fatty acid as components that function as rust inhibitors, thereby reducing the environmental impact and improving rust prevention properties compared to conventional compositions.

[0016] <Base oil> The grease composition according to the present disclosure contains a base oil. The base oil is not particularly limited and may be, for example, a mineral oil, a synthetic oil, or a mixture thereof. The base oil may be a single type or a combination of two or more types.

[0017] Examples of synthetic oils include ether-based synthetic oils such as alkyldiphenyl ether, ester-based synthetic oils such as diesters, polyol esters, and complex-type polyol esters, synthetic hydrocarbon oils such as polyalphaolefins, and alkylnaphthalene-based synthetic oils.

[0018] Examples of mineral oils include those obtained by refining lubricating oil fractions of crude oil using 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.

[0019] From the viewpoint of compatibility with the thickener, the base oil preferably contains at least one selected from polyalphaolefins and mineral oils. In one embodiment, the base oil preferably contains both polyalphaolefins and mineral oils.

[0020] The kinematic viscosity of the base oil at 40°C is 3mm 2 / s~100mm 2 / s is preferred, 5mm 2 / s~70mm 2 / s is more preferable, 10 mm 2 / s~50mm 2 In one embodiment, the kinematic viscosity value of the base oil at 40°C is 15 mm / s. 2 / s~40mm 2 / s is preferred. When the base oil is a mixture of two or more base oils, the kinematic viscosity of the mixture is within the above range. The kinematic viscosity of the base oil at 40°C is the value measured in accordance with JIS K 2283:2000 "Kinematic Viscosity Test Method."

[0021] The content of the base oil is not particularly limited, and can be adjusted appropriately within the range of, for example, 65% by mass to 96.5% by mass relative to the total mass of the grease composition.

[0022] <Thickeners containing calcium soap and lithium soap> The grease composition according to the present disclosure contains a thickener including a calcium soap and a lithium soap.

[0023] Examples of calcium soaps include calcium salts of aliphatic carboxylic acids having a hydroxyl group, such as calcium 12-hydroxystearate, and aliphatic calcium salts, such as calcium stearate, and mixtures thereof. Of the calcium soaps, calcium salts of aliphatic carboxylic acids, such as calcium 12-hydroxystearate, are preferred.

[0024] The calcium soap may be of only one type or of two or more types.

[0025] Examples of lithium soaps include lithium salts of aliphatic carboxylic acids having a hydroxyl group, such as lithium 12-hydroxystearate, lithium salts of aliphatic carboxylic acids, such as lithium stearate, and mixtures thereof. As the lithium soap-based thickener, lithium 12-hydroxystearate, a lithium salt of an aliphatic carboxylic acid, is preferred.

[0026] The grease composition may contain only one type of lithium soap, or two or more types.

[0027] From the viewpoint of water resistance, the content ratio of calcium soap to lithium soap is preferably 0.1:1 to 8:1 by mass (calcium soap:lithium soap), more preferably 0.2:1 to 7:1, and even more preferably 0.2:1 to 6.5:1.

[0028] The thickener contained in the grease composition according to the present disclosure may be calcium soap and lithium soap alone, or calcium soap and lithium soap may be used in combination with other thickeners. Examples of other thickeners include urea and lithium complex soap. When other thickeners are used in combination, the content of the other thickeners relative to the total amount of thickeners is preferably 50 mass% or less.

[0029] From the viewpoint of effectively achieving both water resistance and rust prevention properties against salt water, the thickener contained in the grease composition according to the present disclosure is preferably calcium soap and lithium soap only.

[0030] In the grease composition according to the present disclosure, the total content of the thickeners can be adjusted appropriately according to the desired worked penetration, and is preferably 2.5% by mass to 20% by mass, more preferably 4.0% by mass to 15% by mass, and even more preferably 4.5% by mass to 12.5% ​​by mass, relative to the total amount of the grease composition.

[0031] <Sorbitan fatty acid ester> The grease composition according to the present disclosure contains a sorbitan fatty acid ester. The sorbitan fatty acid ester can function as a rust inhibitor. The sorbitan fatty acid ester may be of one type or of two or more types.

[0032] In the present disclosure, the sorbitan fatty acid ester is preferably a compound represented by the following formula (2) or formula (3).

[0033] [ka]

[0034] In the formula, R A and R B each independently represents a linear or branched, saturated or unsaturated hydrocarbon group having 4 to 22 carbon atoms. The hydrocarbon group preferably has 8 to 22 carbon atoms, more preferably 10 to 20 carbon atoms, and particularly preferably 12 to 20 carbon atoms. Examples of the hydrocarbon group include an alkyl group, an alkenyl group, an aromatic group, an alicyclic group, or a combination thereof. Specific examples of the hydrocarbon group include a 2-ethylhexyl group, an octyl group, a decyl group, a dodecyl group, a tridecyl group, an octadecyl group, an oleyl group, a phenyl group, and a cyclohexyl group. R A and R B are each independently preferably an alkyl group or an alkenyl group, more preferably an alkenyl group, and even more preferably an oleyl group.The sorbitan fatty acid ester of the present disclosure is particularly preferably sorbitan monooleate (structure shown below).

[0035] [ka]

[0036] In the grease composition according to the present disclosure, the content of the sorbitan fatty acid ester is preferably 0.5% by mass to 5.0% by mass, more preferably 1.0% by mass to 4.0% by mass, and even more preferably 1.5% by mass to 3.0% by mass, relative to the total amount of the grease composition, from the viewpoint of achieving both water resistance and rust prevention against salt water.

[0037] <Fatty acid zinc> The grease composition according to the present disclosure contains a fatty acid zinc salt. The fatty acid zinc salt can function as a rust inhibitor. The fatty acid zinc salt preferably contains a fatty acid zinc salt represented by the following formula (1) (hereinafter also referred to as specific fatty acid zinc salt):

[0038] [ka]

[0039] In formula (1), R1 and R2 each independently represent an aliphatic hydrocarbon group having 8 to 18 carbon atoms.

[0040] The aliphatic hydrocarbon group having 8 to 18 carbon atoms represented by R1 or R2 is a saturated or unsaturated aliphatic hydrocarbon group having 8 to 18 carbon atoms, and may be any of a straight-chain, branched-chain, and cyclic aliphatic hydrocarbon group. The aliphatic hydrocarbon group having 8 to 18 carbon atoms represented by R1 or R2 is preferably a branched-chain aliphatic hydrocarbon group having 8 to 18 carbon atoms. The branched-chain aliphatic hydrocarbon group may be a saturated group or an unsaturated group, but is preferably a saturated group.

[0041] The aliphatic hydrocarbon group having 8 to 18 carbon atoms represented by R1 or R2 is preferably a saturated branched aliphatic hydrocarbon group having 8 to 18 carbon atoms, and examples thereof include an isostearyl group, a 2-ethylhexyl group, and a neodecyl group.

[0042] One preferred embodiment of the specific fatty acid zinc is a fatty acid zinc in which at least one of R1 and R2 represents an isostearyl group (hereinafter also referred to as specific fatty acid zinc A). When at least one of R1 and R2 is an isostearyl group, only one of R1 and R2 may be an isostearyl group, or both R1 and R2 may be isostearyl groups.

[0043] Another preferred embodiment of the specific fatty acid zinc is a fatty acid zinc in which at least one of R1 and R2 represents a 2-ethylhexyl group (hereinafter also referred to as specific fatty acid zinc B). When at least one of R1 and R2 is a 2-ethylhexyl group, only one of R1 and R2 may be a 2-ethylhexyl group, or both R1 and R2 may be 2-ethylhexyl groups. Specific fatty acid zinc B may also be a fatty acid zinc corresponding to specific fatty acid zinc A (i.e., a fatty acid zinc in which one of R1 and R2 is an isostearyl group and the other is a 2-ethylhexyl group). Specific fatty acid zinc B may also be a fatty acid zinc having a different structure from 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).

[0044] Another preferred embodiment of the specific fatty acid zinc is a fatty acid zinc in which at least one of R1 and R2 represents a neodecyl group (hereinafter also referred to as specific fatty acid zinc C). When at least one of R1 and R2 is a neodecyl group, only one of R1 and R2 may be a neodecyl group, or both R1 and R2 may be neodecyl groups. The specific fatty acid zinc C may be a fatty acid zinc corresponding to the specific fatty acid zinc A (i.e., a fatty acid zinc in which one of R1 and R2 is an isostearyl group and the other is a neodecyl group). The specific fatty acid zinc C may be a fatty acid zinc corresponding to the specific fatty acid zinc B (i.e., a fatty acid zinc in which one of R1 and R2 is a neodecyl group and the other is a 2-ethylhexyl group). 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 neodecyl group and the other is a branched-chain aliphatic hydrocarbon group other than an isostearyl group or a 2-ethylhexyl group).

[0045] When the specific fatty acid zinc salt contains two or more selected from specific fatty acid zinc salt A, specific fatty acid zinc salt B, and specific fatty acid zinc salt C, it is preferable that the specific fatty acid zinc salt corresponds to a mixture of two or more selected from zinc isostearate, zinc 2-ethylhexanoate, and zinc neodecanoate.

[0046] From the viewpoint of water resistance and rust prevention against salt water, the content of fatty acid zinc is preferably 0.5 mass % to 4.0 mass %, more preferably 0.5 mass % to 3.0 mass %, and even more preferably 0.5 mass % to 2.5 mass %, relative to the total mass of the grease composition.

[0047] The grease composition according to the present disclosure may contain, in addition to the sorbitan fatty acid ester and the zinc fatty acid, a compound that functions as a rust inhibitor (e.g., zinc naphthenate, alkylamine fatty acid salt), as long as the effects of the present disclosure can be obtained. From the viewpoints of water resistance and rust prevention against saltwater, it is preferable that the compound that functions as a rust inhibitor is only both the sorbitan fatty acid ester and the zinc fatty acid.

[0048] <Other additives> The grease composition according to the present disclosure may contain other additives. Other additives include, for example, metal-based detergents such as alkaline earth metal sulfonates, alkaline earth metal phenates, alkaline earth metal salicylates, and alkaline earth metal phosphonates; dispersants such as alkenyl succinimides, boronated alkenyl succinimides, benzylamines, and alkylpolyamines; various anti-wear agents such as zinc dialkyldithiophosphates, phosphorus-based, sulfur-based, amine-based, ester-based, and rapeseed oil-based; various viscosity index improvers that are polymers such as polymethacrylates, ethylene propylene copolymers, styrene-isoprene copolymers, hydrogenated styrene-isoprene copolymers, and polyisobutylene; alkylphenols such as 2,6-di-tert-butyl-p-cresol, 4,4'-methylenebis-(2,6-di-t-butylphenol), and the like. ), phenolic compounds such as n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenol)propionate, and aromatic amine compounds such as naphthylamines and dialkyldiphenylamines; extreme pressure agents such as sulfurized olefins, sulfurized oils and fats, methyl trichlorostearate, chlorinated naphthalene, iodinated benzyl, fluoroalkylpolysiloxane, and polytetrafluoroethylene; various rust inhibitors such as carboxylic acids such as stearic acid, dicarboxylic acids, metal soaps, amine salts of carboxylic acids, metal salts of heavy sulfonic acids, partial esters of carboxylic acids of polyhydric alcohols, and phosphate esters; various corrosion inhibitors such as benzotriazole, substituted triazoles, and benzimidazole; and various antifoaming agents such as silicone oil. The other additives may be used singly or in combination of two or more.

[0049] ~Properties of grease composition~ <Worked penetration> The worked penetration of the grease composition according to the present disclosure is preferably 355 or more, more preferably 355-400, and even more preferably 355-385. The worked penetration shall be measured in accordance with JIS K2220:2013.

[0050] ~Water resistance of grease composition~ The water resistance of the grease composition according to the present disclosure is evaluated by a hydrated shell roll test (in accordance with ASTM D1831).

[0051] The grease composition according to the present disclosure preferably exhibits a change in worked penetration in a hydrous shell roll test of less than 50, more preferably 40, and even more preferably 30. The lower limit of the change is, for example, 1 or less.

[0052] The specific measurement conditions applied to the hydrated shell roll test are the measurement conditions described in the examples below.

[0053] ~Rust prevention properties of grease composition against saltwater~ The rust prevention properties of the grease composition according to the present disclosure against salt water are evaluated by a salt spray test (in accordance with JIS K2246:2018), and the specific conditions used are the measurement conditions described in the examples below.

[0054] ~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. The grease composition according to the present disclosure can be prepared, for example, by appropriately mixing a base oil, a thickener containing a calcium soap and a lithium soap, a sorbitan fatty acid ester, and a zinc fatty acid, and, if necessary, other additives.

[0055] ~Target of use of grease composition~ The grease composition according to the present disclosure can be applied to bearings, etc. The grease composition according to the present disclosure has excellent water resistance and rust prevention properties against saltwater, and therefore can be suitably applied to bearings provided in ships, automobiles, fishing reels, etc. [Example]

[0056] The grease composition according to the present disclosure will be specifically described below using examples, but the grease composition according to the present disclosure is not limited to these examples.

[0057] [Examples 1 to 3, Comparative Examples 1 to 8] 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 1. The lithium soap and calcium soap thickeners were obtained by mixing a thickener base material with a base oil and reacting the thickener base material in the base oil, as described in detail below. The grease composition was prepared so as to contain the respective components in predetermined amounts, and then subjected to a milling process to uniformly disperse the thickener in the grease composition to obtain the final composition.

[0058] Details of each component contained in the grease compositions of the Examples and Comparative Examples are as follows:

[0059] <Base oil> Base oil A: Polyalphaolefin (40°C kinematic viscosity: 5.600 mm 2 / s) Base oil B: Polyalphaolefin (40℃ kinematic viscosity: 30.48mm 2 / s) ·Base oil C: Mineral oil (40℃ kinematic viscosity: 35.71mm 2 / s) The kinematic viscosity at 40°C of the mixed base oils used in the examples and comparative examples was 21 mm 2 / s~33mm 2 / s range.

[0060] <Thickener> Lithium soap A A lithium soap synthesized by mixing a thickener base material with a base oil and reacting the thickener base material in the base oil using the following manufacturing procedure.

[0061] ~Manufacturing procedure (lithium soap)~ Each base oil listed in the table was placed in a heat-resistant container, and 12-hydroxystearate was added as a thickener base material and heated. Next, an aqueous solution of lithium hydroxide was added at around 90°C, and lithium soap was produced through a saponification reaction. This was further heated and cooled with the base oil, and then milled to optimize the lithium soap crystals and uniformly mix and disperse them in the base oil.

[0062] Calcium soap A This calcium soap is synthesized by mixing a thickener with a base oil and allowing the thickener to react in the base oil using the following manufacturing procedure.

[0063] ~Manufacturing procedure (calcium soap)~ Each base oil listed in the table was placed in a heat-resistant container, and 12-hydroxystearate was added as a thickener base material and heated. Next, an aqueous calcium hydroxide solution was added at around 90°C, and calcium soap was produced through a saponification reaction. This was further heated and cooled with the base oil, and then milled to optimize the calcium soap crystals and uniformly mix and disperse them in the base oil.

[0064] <Sorbitan fatty acid ester> Sorbitan monooleate (Emersol O-10V, manufactured by Kao Corporation)

[0065] <Fatty acid zinc> Fatty acid zinc salt A (DICNATE 705S-S, manufactured by DIC Corporation, fatty acid zinc salt containing the compound represented by formula (1))

[0066] <Additives> Zinc naphthenate Alkylnaphthalenesulfonate barium salt (NA-SUL BSN, manufactured by KING)

[0067] [Measurement and Evaluation] The following measurements and evaluations were carried out on each of the obtained grease compositions, and the results are shown in Table 1.

[0068] (1) Worked consistency The worked penetration of each grease composition was measured in accordance with JIS K 2220:2013.

[0069] (2) Rust prevention: Salt spray test A salt spray test was carried out on each grease composition to evaluate its rust prevention properties. The test conditions and evaluation criteria were as follows: The test was conducted in accordance with JIS K 2246:2018, with grease applied to the test specimen, and the test was conducted in 5% saltwater at a test tank temperature of 35°C for 100 hours. Grade A was considered a pass, while grades B to E were considered a fail. Grade A indicates no rust. Grades B to E indicate the degree of rust development, with grade E indicating the most rust.

[0070] (3) Water resistance: Hydrated shell roll test Each grease composition was subjected to a hydrous shell roll test in accordance with ASTM D1831. The test was carried out by placing 45 g of the grease composition and 5 g of ion-exchanged water in a test container at a test temperature of 80°C, a rotation speed of 165 rpm (revolutions per minute), and a test time of 2 hours. Evaluation was made based on the change in consistency before and after the test. The change in consistency was calculated by subtracting the worked consistency before the test from the worked consistency after the test. The worked consistency of the grease composition before and after the test was measured by the method shown in (1) above. When the value of the change in consistency was less than 50, the grease composition was judged to have excellent water resistance.

[0071] The results are shown in Table 1.

[0072] [Table 1]

[0073] As shown in Table 1, it can be seen that the grease compositions of Examples 1 to 3 are superior in water resistance and rust prevention against salt water compared to the grease compositions of Comparative Examples 1 to 5.

Claims

1. A grease composition comprising a base oil, a thickener containing a calcium soap and a lithium soap, a sorbitan fatty acid ester, and a zinc fatty acid.

2. 2. The grease composition of claim 1, wherein the base oil comprises at least one selected from the group consisting of polyalphaolefins and mineral oils.

3. 2. The grease composition according to claim 1, wherein the sorbitan fatty acid ester is sorbitan monooleate.

4. 2. The grease composition according to claim 1, wherein the fatty acid zinc salt comprises a compound represented by the following formula (1): 【Chemical 1】 In formula (1), R １ and R ２ each independently represents an aliphatic hydrocarbon group having 8 to 18 carbon atoms.

5. 2. The grease composition according to claim 1, which has a worked penetration of 355 or more.

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