Lubricant composition

Abstract

To provide a lubricant composition which is excellent in sludge resistance and demulsibility even under a high temperature environment.SOLUTION: A lubricant composition comprises a base oil, a detergent-dispersant including a calcium-based detergent-dispersant, and an ethylene oxide-propylene oxide copolymer, wherein a total content of the detergent-dispersant including the calcium-based detergent-dispersant is 0.07 to 1.5 mass% based on the total amount of the lubricant composition.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] As industrial hydraulic equipment such as construction machinery, injection molding machines, and presses become faster, higher pressure, and smaller, the mechanical elements of these industrial hydraulic equipment are being operated under increasingly severe conditions. Under these circumstances, the lubricating oils used in these machines, especially hydraulic oils, are required to have sufficient lubricity and thermal oxidation stability so that the performance of the machines is not impaired even when used for long periods under high pressure, high temperature, high speed, and high load. In particular, if sludge is generated in the hydraulic circuit, it can adhere to various control valves and filters, causing malfunctions. Therefore, it is strongly required that hydraulic oils do not generate sludge. In addition, hydraulic oils are generally required to have water separation properties because there is a risk of water contamination during use.

[0003] Anti-wear hydraulic fluids containing zinc dialkyldithiophosphate (hereinafter also referred to as "ZnDTP") have traditionally been used, but ZnDTP has the problem of easily causing sludge due to thermal oxidative degradation and hydrolysis. In light of this, zinc-free hydraulic fluids that do not contain ZnDTP have been proposed in recent years (see Patent Document 1). In addition to not using ZnDTP, other methods of suppressing sludge generation include blending additives such as ashless dispersants and metal-based detergents into hydraulic fluids. However, these additives are known to have a negative effect on water separability. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-7186 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0005] The present disclosure has been made in view of the above circumstances, and a problem that one embodiment of the present disclosure aims to solve is to provide a lubricating oil composition that has excellent sludge resistance and demulsibility even when exposed to a high-temperature environment. [Means for solving the problem]

[0006] The present disclosure includes the following aspects.

[0007] <1> A lubricating oil composition comprising a base oil, a detergent-dispersant including a calcium-based detergent-dispersant, and an ethylene oxide-propylene oxide copolymer, wherein the total content of the detergent-dispersant including the calcium-based detergent-dispersant is 0.07% by mass to 1.5% by mass, based on the total amount of the lubricating oil composition. <2> The content of the ethylene oxide-propylene oxide copolymer is 0.01% by mass to 0.1% by mass, based on the total amount of the lubricating oil composition. <1> The lubricating oil composition according to claim 1. <3> The calcium-based detergent-dispersant is an overbased calcium salicylate. <1> or <2> The lubricating oil composition according to claim 1. <4> Does not contain zinc dialkylthiophosphate <1> ~ <3> 10. The lubricating oil composition for hydraulic oil according to claim 9, wherein the lubricating oil composition is a lubricating oil for hydraulic oil. <5> A lubricating oil composition for hydraulic fluids, <1> ~ <4> 1. The lubricating oil composition according to claim 1 . [Effects of the Invention]

[0008] According to one embodiment of the present disclosure, it is possible to provide a lubricating oil composition that has excellent sludge resistance and demulsibility even when exposed to a high-temperature environment. DETAILED DESCRIPTION OF THE INVENTION

[0009] The lubricating oil composition according to the present disclosure will be described in detail below. The following description may be based on representative embodiments, but the lubricating oil composition according to the present disclosure is not limited to such embodiments.

[0010] 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 numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples. In the present disclosure, when a plurality of substances corresponding to each component are present in the composition, the amount of each component in the composition means the total amount of the corresponding substances present in the composition, unless otherwise specified. In the present disclosure, "mass %" and "weight %" are synonymous. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In this disclosure, "JIS" is used as an abbreviation for Japanese Industrial Standards.

[0011] <Lubricating oil composition> The lubricating oil composition according to the present disclosure contains a base oil, a detergent-dispersant containing a calcium-based detergent, and an ethylene oxide-propylene oxide copolymer (hereinafter also referred to as "EO-PO copolymer"), and the total content of the detergent-dispersant containing the calcium-based detergent-dispersant is 0.07 to 1.5 mass% based on the total amount of the lubricating oil composition. The lubricating oil composition according to the present disclosure has excellent sludge resistance and demulsibility properties even when exposed to high-temperature environments.

[0012] (base oil) The lubricating oil compositions according to the present disclosure contain a base oil. The base oil is not particularly limited and may be, for example, a base oil that is used in a lubricating oil composition, such as a mineral base oil or a synthetic base oil. The base oil may be a base oil that is usually used in hydraulic oils.

[0013] 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 made of one type of mineral oil, a mixed base oil made of two or more types of mineral oils, a base oil made of one type of synthetic hydrocarbon oil, a mixed base oil made of two or more types of synthetic hydrocarbon oils, or a mixed base oil made of one or more types of mineral oil and one or more types of synthetic hydrocarbon oil.

[0014] The kinematic viscosity of the base oil at 40°C is preferably 15mm 2 / s~110mm 2 / s, and more preferably 20 mm 2 / s~90mm 2 / s, and more preferably 28 mm 2 / s~75mm 2 / s.

[0015] The 40°C kinematic viscosity of the base oil is measured in accordance with the "Kinematic Viscosity Test Method" described in JIS K 2283:2000.

[0016] In the present disclosure, the kinematic viscosity of a base oil refers to the kinematic viscosity of the mixed base oil after mixing when two or more different base oil components are mixed.

[0017] By having the base oil have a kinematic viscosity at 40°C within the above range, it is easy to ensure load-bearing capacity and to suppress the effects on wear resistance under load. Furthermore, when the lubricating oil composition is used as a hydraulic oil, it is easy to suppress a decrease in pump volumetric efficiency, and even when used in high-pressure hydraulic equipment of 10 MPa or more, it is easy to maintain an oil film and maintain the mechanical efficiency of the hydraulic equipment within an appropriate range.

[0018] The base oil preferably has a %CP of 55 to 92, a %CN of 8 to 40, and a %CA of 10 or less, as measured by ASTM D3238 "ndM Ring Analysis Method," and more preferably has a %CP of 60 to 90%, a CN of 10 to 35, and a %CA of 7 or less.

[0019] By ensuring that the %CP, %CN, and %CA of the base oil are within the above ranges, the thermal oxidation stability is improved, which helps to suppress sludge formation, and by ensuring that the %CP and %CN of the base oil are within the above ranges, the solubility of various additives contained in the lubricating oil composition is ensured.

[0020] The viscosity index of the base oil is preferably at least 95, more preferably at least 98. When the viscosity index of the base oil is within the above range, the degree of refinement of the base oil is increased, the thermal oxidation stability is increased, and sludge generation is easily suppressed.

[0021] 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. When the aniline point of the base oil is within the above range, the degree of refinement of the base oil is increased, the thermal oxidation stability is increased, sludge generation is easily suppressed, the solubility of additives is easily ensured, and compatibility with sealing materials is easily ensured.

[0022] Examples of mineral base oils include solvent refined mineral oils, hydrorefined mineral oils, and hydrocracked mineral oils. Among these, hydrorefined mineral oils and hydrocracked mineral oils are preferred. The methods for producing hydrorefined mineral oils and hydrocracked mineral oils are not particularly limited, but the following methods are preferred.

[0023] A preferred method for producing hydrorefined mineral oil is to vacuum distill the residual oil obtained by atmospheric distillation, then solvent extract the fraction obtained as a lubricating oil fraction, and then subject it to hydrorefining and solvent dewaxing, followed by a second hydrorefining.

[0024] A preferred method for producing hydrocracked mineral oil is to first treat the residual oil obtained by atmospheric distillation of crude oil in a vacuum distillation unit, and then subject the resulting vacuum gas oil to hydrotreating and hydrocracking, and then remove the light components and fuel components in a vacuum stripper to obtain a residue, which is then vacuum distilled, and the resulting lubricating oil fraction is subjected to hydrodewaxing or wax isomerization and stabilization treatment.Among these, a more preferred method is to increase the viscosity index of the lubricating oil fraction by wax isomerization.

[0025] Furthermore, a method for producing a base oil obtained by subjecting a raw material such as slack wax obtained by solvent dewaxing to hydrocracking and hydroisomerization is also a preferred production method.

[0026] Examples of synthetic base oils include base oils obtained by hydrocracking and hydroisomerization of raw materials such as wax obtained by Fischer-Tropsch synthesis, poly-α-olefin base oils, aromatic synthetic oils such as alkylbenzenes and alkylnaphthalenes, ester oils, alkylated phenyl ether oils, etc. Suitable methods for producing poly-α-olefin base oils include synthesizing α-olefins having 6 to 18 carbon atoms by oligomerization of ethylene or thermal cracking of wax, polymerizing 2 to 9 units of this α-olefin, and then hydrogenating the resulting α-olefins.

[0027] Suitable examples of ester oils include diesters produced from monohydric alcohols and dicarboxylic acids, polyol esters produced from polyols and monocarboxylic acids, and complex esters produced from polyols, monocarboxylic acids, and polycarboxylic acids. Examples of diesters include esters of dibasic acids such as adipic acid, azelaic acid, sebacic acid, and dodecanedioic acid. The dibasic acid is preferably an aliphatic dibasic acid having 4 to 36 carbon atoms. The alcohol residue constituting the ester moiety is preferably a monohydric alcohol residue having 4 to 26 carbon atoms. Specific examples of polyols used in polyol esters or complex esters include hindered alcohols without a β-hydrogen atom, such as trimethylolpropane, pentaerythritol, and neopentyl glycol. Suitable monocarboxylic acids for use in polyol esters and complex esters include linear saturated fatty acids such as coconut fatty acid and stearic acid, linear unsaturated fatty acids such as oleic acid, and branched fatty acids such as isostearic acid, while suitable polycarboxylic acids include linear 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.

[0028] When using as the base oil a hydroisomerized base oil or aromatic hydrocarbon oil obtained from raw materials such as slack wax obtained by solvent dewaxing or wax obtained by Fischer-Tropsch synthesis, it is more preferable to use a mixture of solvent refined mineral oil, hydrorefined mineral oil, hydrocracked mineral oil, etc. in order to adjust the %CP and %CN within an appropriate range.

[0029] The content of the base oil is preferably 90% by mass to 99.8% by mass, more preferably 92% by mass to 99.7% by mass, and particularly preferably 95% by mass to 99.5% by mass, based on the total amount of the lubricating composition.

[0030] (detergent dispersant) The lubricating oil compositions according to the present disclosure contain detergent-dispersants, including calcium-based detergent-dispersants. The calcium-based detergent-dispersant may be any compound that contains calcium and functions as a detergent-dispersant. Examples include overbased calcium salicylate, overbased calcium sulfonate, and overbased calcium phenate. From the viewpoint of achieving both good sludge resistance and good demulsification properties, overbased calcium salicylate is preferred. The inorganic salt used to impart basicity to the overbased calcium salicylate is preferably calcium carbonate.

[0031] The base number of the overbased calcium salicylate is preferably 100 mgKOH / g to 400 mgKOH / g, and more preferably 150 mgKOH / g to 350 mgKOH / g.

[0032] The calcium content of the overbased calcium salicylate is preferably 3% to 20% by mass, more preferably 5% to 15% by mass, calculated as elemental calcium. When the base number or calcium content of the overbased calcium salicylate is within the above range, the sludge resistance and demulsification properties are further improved.

[0033] The content of the calcium-based detergent-dispersant is preferably 0.01 to 1.5 mass %, more preferably 0.02 to 0.5 mass %, and even more preferably 0.02 to 0.1 mass %, calculated as elemental calcium relative to the total mass of the lubricating oil composition.

[0034] The amount of calcium element shall be measured according to JPI-5S-38 "Lubricating oil - Test method for added elements - Inductively coupled plasma atomic emission spectrometry."

[0035] In the lubricating oil composition according to the present disclosure, the detergent-dispersant may contain only a calcium-based detergent-dispersant, or from the viewpoint of further improving sludge resistance, may contain a calcium-based detergent-dispersant and other detergent-dispersants. In other words, in the lubricating oil composition according to the present disclosure, the calcium-based detergent-dispersant has the effect of improving sludge resistance and demulsification properties, and the other detergent-dispersant has the effect of improving sludge resistance.

[0036] Other detergent-dispersants include, for example, ashless dispersants and magnesium-based detergent-dispersants.

[0037] From the viewpoint of further enhancing sludge resistance, the detergent-dispersant preferably contains a calcium-based detergent-dispersant and an ashless dispersant.

[0038] The ashless dispersant may be used alone or in combination of two or more.

[0039] Any ashless dispersant used in lubricating oil compositions can be used as the ashless dispersant, including, for example, a nitrogen-containing compound having at least one linear or branched alkyl group or linear or branched alkenyl group in the molecule, or a derivative thereof.

[0040] Examples of the nitrogen-containing compound include succinimide, benzylamine, polyamine, Mannich base, etc. Examples of derivatives of the nitrogen-containing compound include derivatives obtained by reacting the nitrogen-containing compound with boron compounds such as boric acid and borates, phosphorus compounds such as (thio)phosphoric acid and (thio)phosphates, organic acids, hydroxy(poly)oxyalkylene carbonates, etc.

[0041] The ashless dispersant preferably contains a succinimide-based dispersant from the viewpoint of further enhancing sludge resistance. The succinimide-based dispersant may be a boron-free succinimide-based dispersant or a boron-containing succinimide-based dispersant obtained by boron-modifying succinimide.

[0042] The succinimide dispersant preferably has a weight average molecular weight (polystyrene equivalent) of 3,000 to 8,000, more preferably 3,000 to 6,000. The weight average molecular weight is a value measured by gel permeation chromatography and calculated as polystyrene.

[0043] Examples of succinimide dispersants include compounds represented by the following formula (A) (monotype) and compounds represented by the following formula (B) (bistype). From the viewpoint of further improving thermal oxidation stability, it is preferable to use the bistype.

[0044] [ka]

[0045] [ka]

[0046] In formula (A) and formula (B), R 1 and R 3 are each independently an alkyl or alkenyl group having a weight average molecular weight of 800 to 2,500 (polystyrene equivalent), and R 2 are each independently an alkylene group having 2 to 5 carbon atoms, and n is an integer of 1 to 10.

[0047] In one embodiment, the succinimide dispersant is preferably an alkenyl succinimide, such as polybutenyl succinimide, polybutenyl bissuccinimide, or boron-modified compounds thereof.

[0048] In the lubricating oil composition according to the present disclosure, when the detergent-dispersant comprises a calcium-based detergent-dispersant and an ashless dispersant, the content of the ashless dispersant is preferably 0.05 to 1.0 mass %, more preferably 0.1 to 0.5 mass %, relative to the total mass of the lubricating oil composition.

[0049] In the lubricating oil composition according to the present disclosure, when the detergent-dispersant contains a calcium-based detergent-dispersant and an ashless dispersant, from the viewpoint of achieving both sludge resistance and demulsification properties, the amount of the calcium-based detergent-dispersant (A1) is preferably at least 1 / 10, and more preferably at least 1 / 5, of the amount of the ashless dispersant (A2) by mass.

[0050] In the lubricating oil composition according to the present disclosure, the total content of detergent-dispersants is 0.07 to 1.5 mass%, preferably 0.07 to 1.0 mass%, and more preferably 0.08 to 0.5 mass%, based on the total amount of the lubricating oil composition. With the detergent-dispersant content in the above range, the lubricating oil composition according to the present disclosure has excellent sludge resistance and demulsification properties. Furthermore, a low total detergent-dispersant content in the above range is also economical.

[0051] (ethylene oxide-propylene oxide copolymer) The lubricating oil composition according to the present disclosure contains an ethylene oxide-propylene oxide copolymer (EO-PO copolymer), which functions as a demulsifier and exhibits superior demulsification properties when combined with a calcium-based detergent-dispersant.

[0052] The weight average molecular weight (Mw) of the EO-PO copolymer is preferably from 1,000 to 10,000, more preferably from 2,000 to 8,000. The weight average molecular weight is a value measured by gel permeation chromatography and converted into polystyrene.

[0053] The molar ratio of the ethylene oxide block to the propylene oxide block in the EO-PO copolymer is preferably 1:20 to 1:1, more preferably 1:10 to 1:2.

[0054] In the lubricating oil composition according to the present disclosure, the content of the EO-PO copolymer is preferably 0.01 to 0.1 mass %, more preferably 0.01 to 0.05 mass %, from the viewpoints of sludge resistance and demulsification properties.

[0055] The lubricating oil composition according to the present disclosure may contain demulsifiers other than the EO-PO copolymer as long as the object of the present disclosure is not impaired, but it is preferred that the EO-PO copolymer be the only demulsifier contained. Examples of the other demulsifier include anionic surfactants, cationic surfactants, nonionic surfactants, etc. When the lubricating oil composition according to the present disclosure contains the other demulsifier, the content of the other demulsifier is preferably 1 mass % or less, based on the total amount of the lubricating oil composition.

[0056] (Zinc dialkyldithiophosphate) The lubricating oil composition according to the present disclosure may contain zinc dialkyldithiophosphate (ZnDTP) as long as the sludge resistance is not impaired, but it is preferred that it does not contain zinc dialkyldithiophosphate (ZnDTP).

[0057] In the present disclosure, the lubricating oil composition not containing ZnDTP means that the ZnDTP content is less than 0.01 mass% based on the total amount of the lubricating oil composition, and may be 0 mass%. When the lubricating oil composition according to the present disclosure contains ZnDTP, the ZnDTP content is preferably 0.01 mass% to 0.3 mass% based on the total amount of the lubricating oil composition.

[0058] An example of ZnDTP is a compound represented by the following formula (1).

[0059] [ka]

[0060] In formula (1), R 1 , R 2 , R 3 and R 4 each independently represents an alkyl group having 2 to 18 carbon atoms.

[0061] (Other additives) The lubricating oil composition according to the present disclosure may contain various known additives as needed, such as antioxidants, antiwear agents, extreme pressure agents, rust inhibitors, metal deactivators, pour point depressants, viscosity index improvers, friction modifiers, demulsifiers, and antifoaming agents (such as silicone-based antifoaming agents).

[0062] Examples of the antioxidant 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; 4,4'-bis(2,6-di-t-butylphenol), 4,4'-methylenebis(2,6-di-t-butylphenol), 4,4'-ethylenebis(2,6-di-t-butylphenol), 4,4'-butylenebis(2,6-di-t-butylphenol); and 6,6 Examples of antioxidants include bisphenol-based antioxidants such as 4,4'-methylenebis(2-di-t-butyl-4-methylphenol), sulfur-containing phenol-based antioxidants such as 4,4'thiobis-(2,6-di-t-butyl-phenol) and 4,4'thiobis-(2-methyl-6-t-butyl-phenol), amine-based antioxidants such as alkylated diphenylamine and alkylated phenyl-α-naphthylamine, and phosphorus-based antioxidants such as alkyl phosphites and aryl phosphites.

[0063] Examples of anti-wear agents and extreme pressure agents include sulfur-based extreme pressure agents or sulfur-phosphorus-based extreme pressure agents such as sulfurized olefins, polysulfides, sulfurized fats and oils, thiophosphoric acids, and dithiophosphoric acid derivatives; phosphorus-based anti-wear agents and phosphorus-based extreme pressure agents such as phosphate esters, acidic phosphate esters, and amine salts thereof; and organometallic extreme pressure agents such as ZnDTC.

[0064] Examples of rust inhibitors that can be used include metal soaps such as sulfonate metal salts and naphthenate metal salts, alkylsuccinic acid derivatives, alkenylsuccinic acid derivatives, lanolin compounds, surfactants such as sorbitan monooleate and pentaerythritol monooleate, waxes and oxidized waxes, petrolatum, N-oleylsarcosine, rosin amine, alkylated amine compounds such as dodecylamine and octadecylamine, fatty acids such as oleic acid and stearic acid, and phosphorus compounds such as phosphites. Alkylsuccinic acid derivatives, alkenylsuccinic acid derivatives, surfactants, and alkylated amine compounds are preferred, with alkylsuccinic acid derivatives and alkenylsuccinic acid derivatives being more preferred.

[0065] Examples of metal deactivators that can be used include benzotriazole and its derivatives, indazole and its derivatives, benzimidazole and its derivatives, indole and its derivatives, and thiadiazole and its derivatives, with benzotriazole and its derivatives and thiadiazole and its derivatives being preferred.

[0066] Examples of pour point depressants include polyalkyl methacrylate, polybutene, polyalkylthrene, polyvinyl acetate, polyalkyl acrylate, and the like.

[0067] Examples of viscosity index improvers include poly(meth)acrylates (hereinafter sometimes referred to as PMA) and olefin copolymers. Examples of poly(meth)acrylates include those with a weight-average molecular weight of 30,000 to 200,000, and include non-dispersant PMA, which does not have a polar group as a monomer, and dispersant PMA, which uses a monomer with a polar group. Examples of olefin copolymers include those with a weight-average molecular weight of 5,000 to 100,000, and any olefin copolymer may be used, such as a copolymer of ethylene and a monomer other than ethylene.

[0068] Examples of friction modifiers include half ester and / or full ester compounds of polyhydric alcohols, fatty acids, amide compounds, amine compounds, alcohol compounds, phosphate compounds, acidic phosphate amine salts, etc. Specific examples include monooleyl glyceryl ester, oleic acid, oleic acid amine salts, oleic acid amide, oleylamine, stearylamide, stearylamine, acidic phosphate oleylamine salts, etc.

[0069] Examples of the antifoaming agent include silicone-based antifoaming agents such as dimethyl silicone, alkyl-modified silicone, phenyl-modified silicone, and fluorine-modified silicone, and polyacrylate-based antifoaming agents.

[0070] (Physical properties of lubricating oil composition) The lubricating oil composition according to the present disclosure has a kinematic viscosity at 40°C of 9.00 mm 2 / s~110mm 2 / s is preferred, 18mm 2 / s~100mm 2 / s is more preferable, 25mm 2 / s~75mm 2 / s or less is more preferable, and 30 mm 2 / s~60mm 2 / s is particularly preferred.

[0071] The 40°C kinematic viscosity is measured in accordance with the "Kinematic Viscosity Test Method" described in JIS K 2283:2000.

[0072] The viscosity index of the lubricating oil composition according to the present disclosure is not particularly limited, but is preferably at least 100. Having a viscosity index within the above range tends to improve fluidity at low temperatures and oil film retention at high temperatures.

[0073] The viscosity index is measured in accordance with the "Kinematic Viscosity Test Method" described in JIS K 2283:2000.

[0074] (Application) The uses of the lubricating oil composition according to the present disclosure are not particularly limited, and the lubricating oil composition according to the present disclosure can be suitably used, for example, as a hydraulic oil, gear oil, turbine oil, or machine tool oil, and is particularly suitable for use as a hydraulic oil.

[0075] The lubricating oil composition for hydraulic fluids according to the present disclosure is applicable to various industrial hydraulic fluids, and is particularly suitable as a hydraulic fluid for use in hydraulic systems, for example, in hydraulic equipment such as construction machinery, injection molding machines, and presses.

[0076] (Method of producing lubricating oil composition) The method for producing the lubricating oil composition is not particularly limited, and may be any method that involves appropriately mixing a base oil, a detergent-dispersant containing a calcium-based detergent-dispersant, an ethylene oxide-propylene oxide copolymer (antiemulsifier), and, if necessary, other additives. The order in which the components are mixed when producing the lubricating oil composition is not particularly limited, and the components may be mixed sequentially with the base oil. [Example]

[0077] The lubricating oil composition according to the present disclosure will be explained in more detail below using examples, but the lubricating oil composition according to the present disclosure is not limited by these examples in any way.

[0078] 1. Preparation of Lubricating Oil Composition Lubricating oil compositions were prepared for Examples 1 to 12 and Comparative Examples 1 to 13 by mixing the components shown in Tables 1 and 2 in the blending ratios shown in Tables 1 and 2. Note that blank spaces in the composition columns shown in Tables 1 and 2 indicate that the corresponding component was not blended.

[0079] 2. Measurement and evaluation of lubricating oil composition (1) Sludge resistance The "thermal oxidation stability test" shown below was carried out to evaluate the sludge resistance of the lubricating oil compositions. In the thermal oxidation stability test, samples with a sludge amount of 10 mg / 40 ml or less were evaluated as having excellent sludge resistance.

[0080] <Thermal oxidation stability test> 40 ml of the sample was placed in a glass container with an inner diameter of 2.5 cm, and the steel and copper catalysts shown below were immersed in it. The container was then left in a thermostatic chamber equipped with a rotating plate at 160°C for 168 hours. After leaving the container, the sludge formed was filtered out from the sample using a 0.8 μm Millipore filter, and the amount of sludge (mg / 40 ml) was measured. Catalyst material / size: Steel = SPCC-SB, Copper = C1100P, both sizes 1.0mm x 20mm x 50mm

[0081] (2) Demulsifying property The "anti-emulsification test" was carried out in accordance with JIS K 2520:2000 "Test method for water separation property 5. Test method for anti-emulsification property" to evaluate the anti-emulsification property. The evaluation was carried out by recording the volumes (ml) of the oil layer, the water layer and the emulsified layer, and measuring the time (separation time) until the emulsified layer became 3 ml or less. Samples with a separation time of 25 minutes or less were evaluated as having excellent demulsification properties.

[0082] The results are shown in Tables 1 and 2.

[0083] [Table 1]

[0084] [Table 2]

[0085] In Tables 1 and 2, "balance" indicates that the total amount was 100% by mass.

[0086] Details of each component in Tables 1 and 2 are described below.

[0087] (base oil) Mix the base oil 1 and base oil 2 shown below to obtain a mixture with a kinematic viscosity of 46mm at 40°C. 2 A mixed base oil adjusted to achieve / s. Base oil 1: Hydrogenated synthetic mineral oil, kinematic viscosity at 40°C: 34.82mm 2 / s, API base oil classification: Group III ·Base oil 2; Hydrogenated synthetic mineral oil, 40℃ kinematic viscosity: 47.21mm 2 / s, API base oil classification: Group III

[0088] (detergent dispersant) = Calcium-based detergent dispersant = Overbased calcium salicylate; base number by perchloric acid method: 221 mg KOH / g, calcium content: 8.2 mass% = Ashless Dispersant = Succinimide dispersant 1 (boron-free): Polybutenyl succinimide, N content: 1.8% by mass, Mw of polybutenyl group: 1300 Succinimide dispersant 2 (boron-free); Polybutenyl succinimide, N content: 1.1%, Mw of polybutenyl group: 950

[0089] (EO-PO copolymer (demulsifier)) Mw: 6400, molar ratio of ethylene oxide block to propylene oxide block is 1:4.

[0090] (others) Pour point depressant: Polyalkyl methacrylate Antifoaming agent: dimethyl silicone Other additives: Amine antioxidants, benzotriazole derivatives, dithiophosphate derivatives, dithiocarbamate derivatives

[0091] As shown in Tables 1 and 2, the lubricating oil compositions of the Examples have excellent sludge resistance and demulsification properties even when exposed to high-temperature environments, compared to the lubricating oil compositions of the Comparative Examples.

Claims

1. The invention comprises a base oil, a detergent-dispersant containing a calcium-based detergent-dispersant, and an ethylene oxide-propylene oxide copolymer, A lubricating oil composition, wherein the total content of detergent-dispersants including the calcium-based detergent-dispersant is 0.07 mass % to 1.5 mass % based on the total amount of the lubricating oil composition.

2. 2. The lubricating oil composition according to claim 1, wherein the content of the ethylene oxide-propylene oxide copolymer is 0.01 to 0.1 mass % based on the total amount of the lubricating oil composition.

3. 2. The lubricating oil composition of claim 1, wherein the calcium-based detergent-dispersant is an overbased calcium salicylate.

4. 10. The lubricating oil composition of claim 1, which is free of zinc dialkylthiophosphate.

5. The lubricating oil composition according to any one of claims 1 to 4, which is a lubricating oil composition for hydraulic oil applications.

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