Lubricating oil composition

Abstract

To provide a lubricant composition that contains fewer rust inhibitors compared to traditional lubricant compositions, while exhibiting superior rust-prevention properties.SOLUTION: A lubricant composition contains a base oil, a zinc dialkyldithiophosphate, and a metal sulfonate containing a zinc sulfonate as a rust inhibitor. The metal sulfonate is either a combination of a zinc sulfonate and a calcium sulfonate, or solely a zinc sulfonate. The content of the metal sulfonate is 0.015 mass% or more and less than 0.300 mass% relative to the total amount of the lubricant composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to lubricating oil compositions. [Background technology]

[0002] One of the basic properties required of lubricating oil compositions is rust prevention. One way to impart rust prevention to lubricating oil compositions is to incorporate rust inhibitors, and various compounds such as alkenyl succinic acid and partial esters of alkenyl succinic acid, calcium sulfonates (also called calcium sulfonates), and aliphatic amines are used as rust inhibitors.

[0003] For example, Patent Document 1 describes a grease composition comprising a base oil, a thickener, a rust inhibitor, and an extreme pressure agent, wherein the rust inhibitor comprises 0.10 to 10.00% by mass of calcium sulfonate, 0.20 to 10.00% by mass of zinc sulfonate, and 0.10 to 10.00% by mass of zinc carboxylate, relative to the total mass of the grease composition, and the extreme pressure agent comprises 2.00 to 14.00% by mass of zinc dialkyldithiophosphate, relative to the total mass of the grease composition.

[0004] Furthermore, lubricating oil compositions used in industrial machinery and equipment such as construction machinery, injection molding machines, and presses (e.g., hydraulic fluids) are required to possess sufficient wear resistance and thermal oxidation stability so as not to impair the performance of the machinery even when used for long periods under high pressure, high temperature, high speed, and high load. In response to this, zinc dialkyldithiophosphate has been conventionally incorporated into these compositions (see, for example, Patent Documents 2 and 3). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-22772 [Patent Document 2] Japanese Patent Publication No. 2014-218625 [Patent Document 3] Japanese Unexamined Patent Publication No. 2016-89043

Disclosure of the Invention

Problem to be Solved by the Invention

[0006] In industrial machinery and equipment, condensed water generated by temperature changes may mix into lubricating oil. The entry of condensed water can cause rust formation. Therefore, among lubricating oil compositions, industrial lubricating oil compositions are required to have higher rust prevention properties.

[0007] As mentioned above, blending various rust inhibitors is a known means for improving rust prevention properties in lubricating oil compositions. However, rust inhibitors are prone to competitive adsorption with anti-wear agents blended in lubricating oil compositions, and blending of rust inhibitors may cause a decrease in wear resistance. Furthermore, when a rust inhibitor is blended together with zinc dialkyldithiophosphate in a lubricating oil composition, the rust prevention performance expected from blending the rust inhibitor may not be obtained.

[0008] The present disclosure has been made in view of such circumstances, and the problem to be solved by an embodiment of the present disclosure is to provide a lubricating oil composition in which the content of a rust inhibitor is reduced compared to conventional lubricating oil compositions and which is excellent in rust prevention properties.

Means for Solving the Problem

[0009] The present disclosure includes the following aspects. <1> A lubricating oil composition comprising a base oil, zinc dialkyldithiophosphate, and a metal sulfonate including zinc sulfonate as a rust inhibitor, wherein the metal sulfonate is zinc sulfonate and calcium sulfonate, or is zinc sulfonate, and the content of the metal sulfonate is 0.015 mass% or more and less than 0.300 mass% relative to the total amount of the lubricating oil composition. <2> The lubricating oil composition according to <1>, wherein the metal sulfonate is zinc sulfonate and calcium sulfonate, and the total content of zinc sulfonate and calcium sulfonate is 0.015 mass% or more and less than 0.300 mass% based on the total amount of the lubricating oil composition. <3> The lubricating oil composition according to <2>, wherein a ratio of the content of calcium sulfonate to the content of zinc sulfonate is 0.1 or more and 10.0 or less on a mass basis. <4> The lubricating oil composition according to <1>, wherein the metal sulfonate is zinc sulfonate, and the content of zinc sulfonate is 0.015 mass% or more and less than 0.200 mass% based on the total amount of the lubricating oil composition. <5> The kinematic viscosity of the base oil at 40°C is 9 mm 2 / s or more and 110 m 2 / s or less, the lubricating oil composition according to any one of <1> to <4>. <6> The lubricating oil composition according to any one of <1> to <5>, which is for hydraulic fluid. Effects of the Invention

[0010] According to an embodiment of the present disclosure, there is provided a lubricating oil composition in which the content of a rust inhibitor is reduced as compared with conventional lubricating oil compositions and which is excellent in rust resistance. Mode for Carrying Out the Invention

[0011] Hereinafter, exemplary embodiments of the present disclosure will be described. These descriptions and examples are intended to exemplify the embodiments, and do not limit the scope of the invention.

[0012] In the present disclosure, a numerical range indicated using "~" means a range including the numerical values described before and after "~" as the lower limit and the upper limit, respectively. In the numerical ranges described stepwise in the present disclosure, an upper limit or a lower limit described in a certain numerical range may be replaced with an upper limit or a lower limit of a numerical range described in another step. Further, in the numerical ranges described in the present disclosure, an upper limit or a lower limit described in a certain numerical range may be replaced with a value shown in the examples.

[0013] Each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition, if multiple types of the substance corresponding to each component are present in the composition, unless otherwise specified, it refers to the total amount of those multiple types of substances present in the composition.

[0014] In this disclosure, "mass%" and "weight%" are synonymous, and "parts by mass" and "parts by weight" are synonymous.

[0015] In this disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

[0016] In this disclosure, "JIS" is used as an abbreviation for Japanese Industrial Standards.

[0017] In this disclosure, ordinal numbers (e.g., "the first" and "the second") are terms used to distinguish between multiple components and do not limit the number of components or their relative importance.

[0018] <Lubricating oil composition> The lubricating oil composition according to this disclosure is a lubricating oil composition containing a base oil, zinc dialkyldithiophosphate, and a metal sulfonate containing zinc sulfonate as a rust inhibitor, wherein the metal sulfonate is either zinc sulfonate and calcium sulfonate, or zinc sulfonate, and the content of the metal sulfonate is 0.015% by mass or more and less than 0.300% by mass, based on the total amount of the lubricating oil composition.

[0019] Hereinafter, the "metal sulfonates containing zinc sulfonate" included in the lubricating oil composition relating to this disclosure in a specific content range as a rust inhibitor will be collectively referred to as "specific rust inhibitors."

[0020] The lubricating oil composition according to this disclosure contains a metal sulfonate (specific rust inhibitor) including zinc sulfonate as a rust inhibitor. Because the specific rust inhibitor is either zinc sulfonate or contains zinc sulfonate and calcium sulfonate, the composition contains a base oil and zinc dialkyldithiophosphate, yet the amount of rust inhibitor is reduced compared to conventional lubricating oil compositions, and it exhibits superior rust prevention properties. Furthermore, the lubricating oil composition according to this disclosure also exhibits superior wear resistance.

[0021] Although the reason why the lubricating oil composition according to this disclosure exhibits such effects is not clear, it is presumed that by combining a lubricating oil composition containing zinc dialkyldithiophosphate with a metal sulfonate containing zinc sulfonate as a rust inhibitor, the compounds are less likely to undergo competitive adsorption, resulting in improved wear resistance and rust prevention.

[0022] On the other hand, Patent Documents 1 to 3 do not focus on including a base oil, zinc dialkyldithiophosphate, and a predetermined amount of a specific rust inhibitor in a lubricating oil composition.

[0023] (Base oil) The lubricating oil composition relating to this disclosure contains a base oil. The base oil is not particularly limited and includes, for example, base oils used in lubricating oil compositions such as mineral oil-based base oils and synthetic base oils. The base oil may also be a base oil commonly used as hydraulic fluid.

[0024] The base oil may be a single type or a combination of two or more types. For example, the base oil may be a base oil consisting of one type of mineral oil, a mixed base oil consisting of two or more types of mineral oil, a base oil consisting of one type of synthetic hydrocarbon oil, a mixed base oil consisting of two or more types of synthetic hydrocarbon oil, or a mixed base oil consisting of one or more types of mineral oil and one or more types of synthetic hydrocarbon oil.

[0025] The kinematic viscosity of the base oil at 40°C is preferably 15 mm². 2 / s or more 110mm 2 / s or less, more preferably 20mm 2 / s or more 90mm2 / s or less, and more preferably 28mm 2 / s or more 75mm 2 It is less than or equal to / s.

[0026] The kinematic viscosity of the base oil at 40°C shall be measured in accordance with the "Kinematic Viscosity Test Method" described in JIS K 2283:2000.

[0027] In this disclosure, the kinematic viscosity of the base oil refers to the kinematic viscosity of the mixed base oil after mixing two or more different base oil components.

[0028] By having the base oil's kinematic viscosity at 40°C within the above range, it becomes easier to ensure load-bearing capacity and to suppress the impact on wear resistance under load. Furthermore, when the lubricating oil composition is used as hydraulic fluid, it is easier to suppress the decrease in the volumetric efficiency of the pump, and even when used in high-pressure hydraulic equipment of 10 MPa or higher, it is easier to maintain the oil film and maintain the mechanical efficiency of the hydraulic equipment within an appropriate range.

[0029] The base oil is preferably such that %CP is 55 to 9, %CN is 8 to 40, and %CA is 10 or less, according to ASTM D3238 "ndM ring analysis method," and more preferably that %CP is 60 to 90%, CN is 10 to 35, and %CA is 7 or less.

[0030] When the base oil's %CP, %CN, and %CA are within the above ranges, thermal oxidation stability is enhanced, making it easier to suppress sludge formation. Furthermore, when the base oil's %CP and %CN are within the above ranges, it becomes easier to ensure the solubility of various additives contained in the lubricating oil composition, including zinc dialkyldithiophosphate.

[0031] The viscosity index of the base oil is preferably 95 or higher, more preferably 98 or higher. Having the viscosity index of the base oil within this range increases the degree of refinement of the base oil, improves thermal oxidation stability, and makes it easier to suppress sludge generation.

[0032] The aniline point of the base oil according to JIS K 2256:2013 "Aniline Point Test Method" is preferably 90°C to 140°C, more preferably 95°C to 130°C. Having the aniline point of the base oil within this range increases the degree of refinement of the base oil, improves thermal oxidation stability, makes it easier to suppress sludge generation, makes it easier to ensure the solubility of additives, and makes it easier to ensure suitability for sealing materials.

[0033] Examples of mineral oil-based base oils include solvent-refined mineral oil, hydrorefined mineral oil, and hydrocracking mineral oil. Of these, hydrorefined mineral oil and hydrocracking mineral oil are preferred. The method for producing hydrorefined mineral oil and hydrocracking mineral oil is not particularly limited, but preferred methods include the following.

[0034] A preferred method for producing hydrorefined mineral oil includes a method in which the residual oil obtained by atmospheric distillation is subjected to vacuum distillation, the fraction obtained as a lubricating oil is solvent-extracted, and then hydrorefined and dehydrogenated, followed by a second hydrorefining.

[0035] A preferred method for producing hydrocracked mineral oil involves first treating the residue oil obtained from atmospheric distillation of crude oil in a vacuum distillation apparatus, then performing hydrotreatment and hydrocracking on the resulting vacuum-distilled light oil, and subsequently removing the light components and fuel components with a vacuum stripper to obtain the residue. This residue is then subjected to vacuum distillation, and the resulting lubricating oil fraction is subjected to hydrodewaxing treatment or wax isomerization treatment and stabilization treatment. Among these, a method of increasing the viscosity index of the lubricating oil fraction by wax isomerization is considered a more preferred method.

[0036] Furthermore, a method for producing base oil obtained by hydrocracking and hydroisomerizing raw materials such as slack wax obtained by solvent dewaxing is also listed as a preferred production method.

[0037] Examples of synthetic base oils include base oils obtained by hydrocracking and hydroisomerization of raw materials such as wax obtained in Fischer-Tropsch synthesis, poly-α-olefin base oils, aromatic synthetic oils such as alkylbenzenes and alkylnaphthalenes, ester oils, and alkylated phenyl ether oils. A preferred method for producing poly-α-olefin base oil is to synthesize α-olefins having 6 to 18 carbon atoms by low polymerization of ethylene or thermal decomposition of wax, polymerize 2 to 9 units of this α-olefin, and then carry out a hydrogenation reaction.

[0038] Suitable examples of ester oils include diesters produced from a monohydric alcohol and a dicarboxylic acid, polyol esters produced from a polyol and a monocarboxylic acid, or complex esters produced from a polyol, a monocarboxylic acid, or a polycarboxylic acid. Examples of diesters include esters of dibasic acids such as adipic acid, azelaic acid, sebacic acid, and dodecanediic acid. Aliphatic dibasic acids having 4 to 36 carbon atoms are preferred as dibasic acids. The alcohol residue constituting the ester portion is preferably a monohydric alcohol residue having 4 to 26 carbon atoms. Furthermore, as polyols used in polyol esters or complex esters, specifically hindered alcohols without β-hydrogens such as trimethylolpropane, pentaerythritol, and neopentyl glycol are preferably used. Furthermore, suitable monocarboxylic acids used in polyol esters and complex esters include straight-chain saturated fatty acids such as coconut fatty acid and stearic acid, straight-chain unsaturated fatty acids such as oleic acid, and branched fatty acids such as isostearic acid. Suitable polycarboxylic acids include straight-chain saturated polycarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. Suitable examples of alkylated phenyl ether oils include alkylated diphenyl ethers and (alkylated) polyphenyl ethers.

[0039] When a hydroisomerized base oil obtained from a raw material such as slack wax obtained by solvent dewaxing or a wax obtained by Fischer-Tropsch synthesis, or an aromatic hydrocarbon oil is used as the base oil, it is more preferable to mix and use solvent-refined mineral oil, hydrorefined mineral oil, hydrocracked mineral oil or the like to adjust %CP and %CN to appropriate ranges.

[0040] The content of the base oil is preferably 90% by mass or more and 99.8% by mass or less, more preferably 92% by mass or more and 99.7% by mass or less, and particularly preferably 95% by mass or more and 99.5% by mass or less, based on the total amount of the lubricating composition.

[0041] (Zinc dialkyldithiophosphate) The lubricating oil composition according to the present disclosure contains zinc dialkyldithiophosphate. Zinc dialkyldithiophosphate may be used alone, or may be used in a combination of two or more kinds thereof.

[0042] Examples of the zinc dialkyldithiophosphate include a compound represented by the following formula (1).

[0043]

Chemical Formula

[0044] In formula (1), R 1 , R 2 , R 3 and R 4 each independently represent an alkyl group having 3 to 18 carbon atoms. R 1 , R 2 , R 3 and R 4 each independently is preferably an alkyl group having 6 to 14 carbon atoms, and more preferably an alkyl group having 6 to 12 carbon atoms.

[0045] R 1 , R 2 , R 3 and R 4The carbon atom bonded to the oxygen atom may be a primary alkyl group, which is a primary carbon atom, or a secondary alkyl group, which is a secondary carbon atom. 1 , R 2 , R 3 and R 4 It may have only a primary alkyl group, or only a secondary alkyl group, or it may have both a primary alkyl group and a secondary alkyl group. From the viewpoint of thermal oxidation stability, R 1 , R 2 , R 3 and R 4 It is preferable that it be a primary alkyl group.

[0046] Examples of primary alkyl groups include methyl, ethyl, propyl, butyl, isobutyl, pentyl, hexyl, heptyl, octyl, ethylhexyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, and heptadecyl groups.

[0047] From the viewpoint of wear resistance and oxidation prevention, the content of zinc dialkyldithiophosphate is preferably 0.01% to 0.5% by mass, more preferably 0.05% to 0.4% by mass, and even more preferably 0.1% to 0.4% by mass, based on the total amount of the lubricating oil composition.

[0048] (Rust inhibitor) =Specific rust inhibitor= The lubricating oil composition according to this disclosure contains a metal sulfonate (specific rust inhibitor) containing zinc sulfonate as a rust inhibitor. The specific rust inhibitor contained in the lubricating oil composition according to this disclosure is either zinc sulfonate and calcium sulfonate, or zinc sulfonate alone. That is, the specific rust inhibitor consists of a first embodiment in which it is a combination of zinc sulfonate and calcium sulfonate, or a second embodiment in which it consists only of zinc sulfonate.

[0049] Furthermore, the content of specific rust inhibitors is set at 0.015% by mass or more and less than 0.300% by mass relative to the total amount of the lubricating oil composition, from the viewpoint of achieving both a reduction in the amount of rust inhibitors and excellent rust prevention properties.

[0050] The first embodiment of the specific rust inhibitor is an embodiment in which zinc sulfonate and calcium sulfonate are used in combination.

[0051] In the first embodiment of the specific rust inhibitor, the combination of zinc sulfonate and calcium sulfonate may be a combination of one type of zinc sulfonate and one type of calcium sulfonate, a combination of one type of zinc sulfonate and two or more types of calcium sulfonate, a combination of two types of zinc sulfonate and one or more types of calcium sulfonate, or a combination of two types of zinc sulfonate and two or more types of calcium sulfonate.

[0052] When the specific rust inhibitor is of the first embodiment, from the viewpoint of achieving both a reduction in the amount of rust inhibitor and rust prevention performance, the total content of zinc sulfonate and calcium sulfonate is preferably 0.015% by mass or more and less than 0.300% by mass, more preferably 0.020% by mass or more and 0.100% by mass or less, and even more preferably 0.024% by mass or more and 0.030% by mass or less, based on the total amount of the lubricating oil composition.

[0053] In the first embodiment of the specific rust inhibitor, the ratio of the calcium sulfonate content to the zinc sulfonate content is preferably 0.1 to 10.0 by mass, more preferably 0.1 to 5.0, and even more preferably 0.1 to 2.0, from the viewpoint of reducing the rust inhibitor content, rust prevention, and wear resistance.

[0054] A second embodiment of the specific rust inhibitor is one in which only zinc sulfonate is used.

[0055] In the second embodiment of the specific rust inhibitor, zinc sulfonate may be of one type only, or two or more types may be used in combination.

[0056] When the specific rust inhibitor is of the second embodiment, from the viewpoint of achieving both a reduction in the amount of rust inhibitor and rust prevention performance, the zinc sulfonate content is preferably 0.015% by mass or more and less than 0.200% by mass, more preferably 0.018% by mass or more and 0.100% by mass or less, and even more preferably 0.018% by mass or more and 0.024% by mass or less, based on the total amount of the lubricating oil composition.

[0057] The zinc sulfonate is not particularly limited as long as it can be used as a rust inhibitor in a lubricating oil composition.

[0058] Specific examples of zinc sulfonates include, for example, the compounds represented by the following formula (2).

[0059] [R 5 -SO3]2Zn ···(2) In formula (2), R 5 This represents an alkyl group, an alkenyl group, an alkylnaphthyl group, a dialkylnaphthyl group, or an alkylphenyl group. R 5 In this context, both alkyl and alkenyl groups are either linear or branched, and have 2 to 22 carbon atoms.

[0060] Examples of compounds represented by formula (2) include zinc salts of dialkylnaphthalenesulfonic acid, zinc salts of alkylbenzenesulfonic acid, and zinc salts of petroleum sulfonic acid, with zinc salts of dinonylnaphthalenesulfonic acid being particularly preferred.

[0061] The calcium sulfonate is not particularly limited as long as it can be used as a rust inhibitor in a lubricating oil composition.

[0062] Specific examples of calcium sulfonates include, for example, the compounds represented by the following formula (3).

[0063] [R 6 -SO3]2Ca...Formula (3) In formula (3), R 6This represents an alkyl group, alkenyl group, alkylnaphthyl group, dialkylnaphthyl group, alkylphenyl group, or high-boiling-point petroleum fraction. R 6 In this context, both alkyl and alkenyl groups are either linear or branched, and have 2 to 22 carbon atoms.

[0064] Examples of compounds represented by formula (3) include, for example, calcium salts of dialkylnaphthalenesulfonic acid, calcium salts of alkylbenzenesulfonic acid, and calcium salts of petroleum sulfonic acid, with calcium salts of dinonylnaphthalenesulfonic acid being particularly preferred.

[0065] The lubricating oil composition relating to this disclosure may contain, in addition to the specified rust inhibitor, other components that function as rust inhibitors, to the extent that the effects relating to this disclosure are achieved.

[0066] (Other additives) The lubricating oil composition according to this disclosure may contain various known additives as needed. Examples of such additives that may be included as needed include antioxidants, anti-wear agents, extreme pressure agents, ashless dispersants, detergent dispersants, metal deactivators, pour point depressants, viscosity index improvers, friction modifiers, anti-emulsifiers, and defoaming agents (silicone-based defoamers, etc.).

[0067] Examples of antioxidants include phenolic antioxidants, amine antioxidants, and phosphorus antioxidants. Specifically, examples of antioxidants include monocyclic phenolic antioxidants such as 2,6-di-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, and 2,6-di-t-butyl-4-ethylphenol, as well as 4,4'-bis(2,6-di-t-butylphenol), 4,4'-methylenebis(2,6-di-t-butylphenol), 4,4'-ethylenebis(2,6-di-t-butylphenol), and 4,4'-butylenebis(2,6-di-t-butylphenol). Examples include bisphenol antioxidants such as 6,6'-methylenebis(2-di-t-butyl-4-methylphenol), sulfur-containing phenol antioxidants such as 4,4'thiobis-(2,6-di-t-butyl-phenol) and 4,4'thiobis-(2-methyl-6-t-butyl-phenol), amine antioxidants such as alkylated diphenylamine and alkylated phenyl-α-naphthylamine, and phosphorus antioxidants such as alkyl phosphites and aryl phosphites.

[0068] Examples of extreme pressure agents include sulfur-based extreme pressure agents such as sulfurized olefins, polysulfides, sulfurized oils and fats, and dithiophosphate derivatives; phosphorus-based extreme pressure agents such as acidic phosphate esters or their amine salts; and organometallic extreme pressure agents such as ZnDTC.

[0069] Examples of anti-wear agents include phosphate esters and phosphite esters. Specifically, examples of phosphate esters and phosphite esters include tricresyl phosphate, trixylenyl phosphate, cresyldiphenyl phosphate, dicresylphenyl phosphate, tripropyl phosphate, tributyl phosphate, tri(2-ethylhexyl) phosphate, diphenyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, and other triaryl phosphates.

[0070] Examples of metallic detergent dispersants include sulfonates, finates, salicylates, etc., in which the metallic component is calcium or magnesium. However, calcium sulfonate used as a rust inhibitor is not included in the definition of metallic detergent dispersants. Specific examples of metallic detergent dispersants include, for example, overbasic calcium salicylate, overbasic calcium finate, and overbasic calcium sulfonate.

[0071] Examples of ashless dispersants include succinimide compounds, specifically polybutenylbissuccinimide and its boron-modified compounds.

[0072] Examples of metal deactivators include benzotriazole and its derivatives, indazole and its derivatives, benzimidazole and its derivatives, indole and its derivatives, thiadiazole and its derivatives, and the like, with benzotriazole and its derivatives and thiadiazole and its derivatives being preferred.

[0073] Examples of pour point depressants include polyalkyl methacrylate, polybutene, polyalkylstyrene, polyvinyl acetate, and polyalkyl acrylate.

[0074] Examples of antiemulsifiers include anionic surfactants, cationic surfactants, and nonionic surfactants, with nonionic surfactants being preferred. Specifically, polyalkylene glycols are preferred. Polyalkylene glycols can be homopolymers obtained by polymerizing ethylene glycol, propylene glycol, and butylene glycol as monomers, or copolymers obtained by polymerizing them in combination. Homopolymers and copolymers may be used individually or in combination, but copolymers are preferred. As polyalkylene glycols, ethylene oxide-propylene oxide copolymers (hereinafter also referred to as "EO-PO copolymers") obtained by polymerizing ethylene glycol and propylene glycol are particularly preferred.

[0075] Examples of viscosity index improvers include polyisobutylene and olefin copolymers.

[0076] Examples of defoaming agents include silicone-based defoaming agents such as dimethyl silicone, alkyl-modified silicone, phenyl-modified silicone, and fluorine-modified silicone, as well as polyacrylate-based defoaming agents.

[0077] (Physical properties of lubricating oil compositions) The kinematic viscosity of the lubricating oil composition relating to this disclosure at 40°C is 9.00 mm. 2 / s or more 110mm 2 Preferably less than / s, and 18mm 2 / s or more 100mm 2 / s or less is more preferably, 25mm 2 / s or more 75mm 2 / s or less is even more preferable, 30mm 2 / s or more 74.8mm 2 / s or less is even more preferable.

[0078] The kinematic viscosity at 40°C shall be measured in accordance with the "Kinematic Viscosity Test Method" described in JIS K 2283:2000.

[0079] The viscosity index of the lubricating oil composition relating to this disclosure is not particularly limited, but is preferably 100 or higher.

[0080] The viscosity index shall be measured in accordance with the "Kinematic Viscosity Test Method" described in JIS K 2283:2000.

[0081] (Application) The lubricating oil composition according to this disclosure is not particularly limited in its applications, and because of its excellent rust-preventive properties, it can be suitably applied, for example, to hydraulic fluids, turbine oils, gear oils, and machine tool oils. The lubricating oil composition according to this disclosure is particularly suitable for use as a hydraulic fluid.

[0082] (Method for manufacturing lubricating compositions) The method for producing the lubricating oil composition is not particularly limited, and may be a mixture of a base oil, zinc dialkyldithiophosphate, and a metal sulfonate as a rust inhibitor, with other additives as needed. The mixing order of each component when producing the lubricating oil composition is not particularly limited, and each component may be mixed sequentially with the base oil. [Examples]

[0083] Examples are described below, but the lubricating oil compositions relating to this disclosure are not limited to these examples.

[0084] <Examples 1-6, Comparative Examples 1-10> 1. Preparation of lubricating oil composition As Examples 1-6 and Comparative Examples 1-10, lubricating oil compositions were prepared by mixing each component shown in Table 1 in the blending ratios (mass%) shown in Table 1. Blank spaces in the composition column of Table 1 indicate that the corresponding component was not included.

[0085] In Table 1, the criterion for determining whether the amount of rust inhibitor has been reduced was whether the rust inhibitor content was less than 0.300% by mass.

[0086] 2. Measurement and evaluation of lubricating oil compositions (1) kinematic viscosity of lubricating oil composition at 40°C The kinematic viscosity of the lubricating compositions of the examples and comparative examples was measured at 40°C in accordance with the "Kinematic Viscosity Test Method" described in JIS K 2283:2000.

[0087] (2) Rust prevention test The lubricating compositions of the examples and comparative examples obtained above were evaluated in a rust prevention test. The evaluation method and evaluation criteria are shown below.

[0088] • Evaluation method The rust prevention performance was evaluated in accordance with the "rust prevention performance test using artificial seawater" specified in JIS K 2510:1998 "Lubricating oils - Test methods for rust prevention performance". The test duration was 24 hours. The rust prevention performance was evaluated by visually observing whether or not rust had formed on the test specimens after the test was completed.

[0089] • Evaluation criteria No rust: No rust occurred. Rust present: Rust was observed.

[0090] (3) Abrasion resistance test (shell four-ball test) The lubricating compositions of the examples and comparative examples obtained above were used in a shell four-ball test to evaluate their wear resistance. The evaluation method and evaluation criteria are shown below.

[0091] • Evaluation method In accordance with JPI-5S-32 "Test Method for Abrasion Resistance of Lubricating Oil (Shell 4-Ball Test)," the abrasion mark diameter was measured at 294N, 1200rpm, 60min, and 75℃ using the test conditions specified in JCMAS P 041.

[0092] • Evaluation criteria The criterion for determining whether a material has excellent wear resistance was whether the diameter of the wear marks was 0.6 mm or less.

[0093] The results are shown in Table 1.

[0094] [Table 1]

[0095] *In Table 1, "remainder" indicates that the components corresponding to the mixed base oil were included so that the total amount becomes 100% by mass. *In Table 1, "mass%" is synonymous with "mass%".

[0096] Details of each component in Table 1 are described below.

[0097] (Base oil) • Base oil 1; Hydrogenated refined mineral oil, kinematic viscosity at 40°C: 32.56 mm² 2 / s, API base oil classification: Group I • Base oil 2; Hydrogenated refined mineral oil, kinematic viscosity at 40°C: 98.47 mm 2 / s, API base oil classification: Group I The base oil is a mixture of base oil 1 and base oil 2, with a kinematic viscosity of 46 mmHg at 40°C. 2 A mixed base oil adjusted to have a coefficient of / s was used.

[0098] (Zinc dialkyldithiophosphate) • Zinc dialkyldithiophosphate 1; R in formula (1) 1 ~R 4 Primary dialkyldithiophosphate zinc, which has a 2-ethylhexyl group.

[0099] (Rust inhibitor) • Zn sulfonate-1; zinc dinonylnaphthalene sulfonate • Ca sulfonate-1; calcium dinonylnaphthalene sulfonate • Barium sulfonate; barium salt of dinonylnaphthalene sulfonic acid Alkenyl succinic acid; Alkenyl succinic acid, Acid value: 195 mg KOH / g The zinc sulfonate 1 contained in Examples 1 and 3, and the combination of zinc sulfonate 1 and calcium sulfonate 1 contained in Examples 2, 4-6, constitute a specific rust inhibitor.

[0100] (Other additives) • Metal-type cleaning agent; perbasic calcium salicylate, base number by perchloric acid method: 221 mg KOH / g, Ca content: 8.9% by mass • Ashless dispersants; succinimide-based dispersants • Antioxidants; phenolic antioxidants • Pour point depressant: Polyalkyl methacrylate • Antiemulsifier; ethylene oxide-propylene oxide copolymer • Silicone-based defoaming agent; dimethyl silicone

[0101] As shown in Table 1, the lubricating oil composition of the example containing the specific rust inhibitor has a lower rust inhibitor content and exhibits superior rust prevention compared to the lubricating oil composition of the comparative example.

Claims

1. This lubricating oil composition contains a base oil, zinc dialkyldithiophosphate, and a metal sulfonate containing zinc sulfonate as a rust inhibitor. The metal sulfonate is the zinc sulfonate and calcium sulfonate, The total content of the zinc sulfonate and calcium sulfonate is 0.018% by mass or more and 0.030% by mass or less, relative to the total amount of the lubricating oil composition. A lubricating oil composition in which the ratio of the calcium sulfonate content to the zinc sulfonate content is 0.1 or more and 2.0 or less by mass.

2. A lubricating oil composition comprising a base oil, zinc dialkyldithiophosphate, and a metal sulfonate containing zinc sulfonate as a rust inhibitor, The metal sulfonate is only the zinc sulfonate, A lubricating oil composition in which the zinc sulfonate content is 0.018% by mass or more and 0.024% by mass or less, based on the total amount of the lubricating oil composition.

3. The kinematic viscosity at 40°C is 9.00 mm. ２ / s or more 110mm ２ The lubricating oil composition according to claim 1, wherein the value is less than or equal to / s.

4. The lubricating oil composition according to claim 2, wherein the kinematic viscosity at 40°C is 9.00 mm² / s or more and 110 mm² / s or less.

5. A lubricating oil composition according to any one of claims 1 to 4, for use as hydraulic fluid.

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