Lubricating oil composition

Abstract

A lubricating oil composition containing a base oil (A), a surfactant (B), a partial ester of a polyhydric alcohol (C), and water, wherein the content of water is more than 0.1 mass% with respect to the total amount of the lubricating oil composition.

Description

lubricating oil composition

[0001] This application claims priority from Japanese Patent Application No. 2024-147735, filed on August 29, 2024, the contents of which are incorporated herein by reference.

[0002] Lubricating oil compositions are used in spinning machines, looms, knitting machines, and the like to prevent wear of needles and cams.

[0003] For example, Patent Document 1 discloses a lubricating oil composition to be used in manufacturing equipment for products that are sensitive to contamination by chemicals containing lubricating oils, such as spinning machines, looms, or knitting machines.

[0004] Japanese Patent Application Laid-Open No. 2015-218202

[0005] In a production line using a spinning machine, a loom, and a knitting machine, the lubricating oil composition used in the spinning machine, the loom, and the knitting machine may adhere to the knitted fabric produced on the production line. The knitted fabric to which the lubricating oil composition adheres must be cleaned by dry cleaning. If the lubricating oil composition is difficult to clean, the knitted fabric to which the lubricating oil composition adheres must be discarded. Therefore, there is a demand for a lubricating oil composition that can be washed off with water.

[0006] Conventional lubricating oil compositions do not come into contact with water, and therefore their detergency with water has not been investigated.The detergency with water of the lubricating oil composition described in Patent Document 1 has also not been investigated.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a lubricating oil composition that has good water detergency and storage stability.

[0008] The present inventors have conducted extensive research into the water detergency of lubricating oil compositions. The present inventors incorporated water and a surfactant into the lubricating oil composition in order to enhance the compatibility between water and the lubricating oil composition. However, although the inclusion of water and a surfactant in the lubricating oil composition improved the compatibility between the lubricating oil composition and water, the storage stability of the lubricating oil composition decreased. Therefore, the inventors further added a partial ester (C) of a polyhydric alcohol to the lubricating oil composition to control the amount of water added. The inventors discovered that this configuration allows the lubricating oil composition to achieve both water detergency and storage stability, leading to the completion of the present invention. Specifically, the present invention employs the following configuration.

[0009] [1] A lubricating oil composition comprising a base oil (A), a surfactant (B), a partial ester of a polyhydric alcohol (C), and water, wherein the content of the water is greater than 0.1 mass % based on the total amount of the lubricating oil composition. [2] The lubricating oil composition according to [1], further comprising an antiwear agent (D). [3] The lubricating oil composition according to [2], wherein the antiwear agent (D) comprises one or more compounds selected from the group consisting of a phosphoric acid ester, an acidic phosphoric acid ester, and an amine salt of an acidic phosphoric acid ester. [4] The lubricating oil composition according to [2], wherein the antiwear agent (D) comprises a phosphoric acid ester and an acidic phosphoric acid ester or an amine salt of an acidic phosphoric acid ester. [5] The lubricating oil composition according to any one of [1] to [4], wherein the HLB of the surfactant (B) is 10.0 to 16.0. [6] The lubricating oil composition according to any one of [1] to [5], wherein the partial ester of a polyhydric alcohol (C) comprises a sorbitan fatty acid ester. [7] The lubricating oil composition according to any one of [1] to [6], which is used in a spinning machine, a loom, a knitting machine, or a food, drug, or cosmetic manufacturing device.

[0010] According to the present invention, it is possible to provide a lubricating oil composition that has good water detergency and storage stability.

[0011] (Lubricating Oil Composition) The lubricating oil composition of this embodiment contains a base oil (A), a surfactant (B), a partial ester of a polyhydric alcohol (C), and water.

[0012] The kinematic viscosity of the lubricating oil composition of this embodiment at 40°C is 50mm ２ / s or more, and 55 mm ２ / s or more is more preferable, and 60 mm ２ The kinematic viscosity of the lubricating oil composition of this embodiment at 40°C is more preferably 75 mm / s or more. ２ / s or less, and ２ / s or less is more preferable, and 65 mm ２ For example, the kinematic viscosity of the lubricating oil composition of this embodiment at 40°C is 50 mm / s or less. ２ / s or more 75mm ２ / s or less, and ２ / s or more 70mm ２ / s or less is more preferable, and 60 mm ２ / s or more 65mm ２ It is more preferable that the ratio is 1 / s or less.

[0013] When the kinematic viscosity at 40°C of the lubricating oil composition of this embodiment is within the above preferred range, the lubricity is further improved.

[0014] In this specification, the kinematic viscosity at 40°C means the kinematic viscosity at 40°C measured in accordance with JIS K2283:2000.

[0015] <Base oil (A)> The lubricating oil composition of this embodiment contains base oil (A). The kinematic viscosity of base oil (A) at 40°C is 50 mm ２ / s or more, and 55 mm ２ / s or more is more preferable, and 60 mm ２ The kinematic viscosity of the base oil (A) at 40°C is more preferably 75 mm / s or more. ２ / s or less, and ２ / s or less is more preferable, and 65 mm ２ For example, the kinematic viscosity of the base oil (A) at 40°C is 50 mm / s or less. ２ / s or more 75mm ２ / s or less, and ２ / s or more 70mm ２ / s or less is more preferable, and 60 mm ２ / s or more 65mm ２ It is more preferable that the ratio is 1 / s or less.

[0016] When the kinematic viscosity at 40°C of the lubricating oil composition of this embodiment is within the above preferred range, the lubricity is further improved.

[0017] The base oil (A) of the lubricating oil composition of this embodiment may be a mineral oil or a synthetic oil.

[0018] <Mineral Oil> Mineral oil can be a distillate obtained by atmospheric distillation of crude oil. Alternatively, lubricating oil fractions obtained by further vacuum distillation of this distillate and refining it through various refining processes can also be used. Refining processes can include hydrorefining, solvent extraction, solvent dewaxing, hydrodewaxing, sulfuric acid washing, and clay treatment, and can be combined as appropriate. Mineral oil can be obtained by combining these refining processes in an appropriate order. Alternatively, a mixture of refined oils with different properties obtained by subjecting different crude oils or distillate oils to a combination of different refining processes can also be used.

[0019] The mineral oil may be a Group I base oil (hereinafter referred to as "API Group I base oil"), a Group II base oil (hereinafter referred to as "API Group II base oil"), or a Group III base oil (hereinafter referred to as "API Group III base oil") of the API base oil classification, or a mixture thereof. API Group I base oils are mineral base oils having a sulfur content of more than 0.03 mass% and / or a saturated content of less than 90 mass%, and a viscosity index of 80 to less than 120. API Group II base oils are mineral base oils having a sulfur content of 0.03 mass% or less, a saturated content of 90 mass% or more, and a viscosity index of 80 to less than 120. API Group III base oils are mineral base oils having a sulfur content of 0.03 mass% or less, a saturated content of 90 mass% or more, and a viscosity index of 120 or more.

[0020] The base oil (A) of the lubricating oil composition of this embodiment may be a single mineral oil or a mixture of multiple mineral oils, the API classifications of which may be the same or different.

[0021] <Synthetic Oil> Examples of synthetic oils include polyolefins such as poly-α-olefins, ester base oils such as diesters and polyol esters, polyalkylene glycols, alkylbenzenes, and alkylnaphthalenes. Among the above, polyolefins are preferred as synthetic oils from the viewpoints of availability, cost, viscosity characteristics, and oxidation stability, and poly-α-olefins (PAOs) are more preferred. As the base oil (A) of the lubricating oil composition of this embodiment, one synthetic oil may be used alone, or multiple synthetic oils may be mixed and used.

[0022] The base oil (A) of the lubricating oil composition of this embodiment may be either a mineral oil or a synthetic oil, or a mixture of a mineral oil and a synthetic oil.

[0023] The content of the base oil (A) in the lubricating oil composition of this embodiment is preferably 75% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more, based on the total amount of the lubricating oil composition. The content of the base oil (A) in the lubricating oil composition of this embodiment is preferably 98% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less, based on the total amount of the lubricating oil composition. For example, the content of the base oil (A) in the lubricating oil composition of this embodiment is preferably 75% by mass or more and 98% by mass or less, more preferably 80% by mass or more and 95% by mass or less, and even more preferably 85% by mass or more and 90% by mass or less, based on the total amount of the lubricating oil composition.

[0024] <Surfactant (B)> The HLB of the surfactant (B) in the lubricating oil composition of this embodiment is preferably 10.0 or more, more preferably 11.0 or more, and even more preferably 12.0 or more. The HLB of the surfactant (B) is preferably 16.0 or less, more preferably 15.0 or less, and even more preferably 14.0 or less. For example, the HLB of the surfactant (B) is preferably 10.0 or more and 16.0 or less, more preferably 11.0 or more and 15.0 or less, and even more preferably 12.0 or more and 14.0 or less.

[0025] When the HLB of the surfactant (B) is within the above preferred range, the water detergency and storage stability of the lubricating oil composition are further improved.

[0026] The surfactant (B) is preferably a nonionic surfactant, and examples of the nonionic surfactant include alkylene glycol, polyoxyalkylene glycol, polyoxyalkylene alkyl ether, polyoxyalkylene aryl ether, fatty acid ester of polyoxyalkylene adduct of polyhydric alcohol, polyoxyalkylene fatty acid ester, polyoxyalkylene alkylamine, and alkyl alkanolamide.

[0027] The polyoxyalkylene glycol may be a homopolymer or copolymer of alkylene oxide such as ethylene oxide, propylene oxide, butylene oxide, etc. The polyoxyalkylene alkyl ether may be an alkyl ether of the above polyoxyalkylene glycol.

[0028] Among the above surfactants, polyoxyalkylene alkyl ethers are preferred as the surfactant (B).

[0029] The surfactant (B) in the lubricating oil composition of this embodiment may be used alone or in combination of two or more.

[0030] The content of surfactant (B) in this embodiment is preferably 1 mass% or more, more preferably 2 mass% or more, and even more preferably 3 mass% or more, based on the total amount of the lubricating oil composition. The content of surfactant (B) is preferably 15 mass% or less, more preferably 10 mass% or less, and even more preferably 7 mass% or less, based on the total amount of the lubricating oil composition. For example, the content of surfactant (B) is preferably 1 mass% or more and 15 mass% or less, more preferably 2 mass% or more and 10 mass% or less, and even more preferably 3 mass% or more and 7 mass% or less, based on the total amount of the lubricating oil composition.

[0031] When the content of the surfactant (B) is within the above preferred range, the water detergency and storage stability of the lubricating oil composition are further improved.

[0032] <Partial Ester of Polyhydric Alcohol (C)> In this specification, the partial ester of polyhydric alcohol (C) is an ester in which at least one of the hydroxy groups in the polyhydric alcohol is not esterified and remains as a hydroxy group.

[0033] The polyhydric alcohol used as a raw material for the partial ester of polyhydric alcohol (C) preferably has 2 to 10 hydroxy groups in the molecule, more preferably 3 to 6. The polyhydric alcohol used as a raw material for the partial ester of polyhydric alcohol (C) preferably has 2 to 20 carbon atoms, more preferably 3 to 10 carbon atoms. The polyhydric alcohol is preferably at least one polyhydric alcohol selected from the group consisting of glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, and sorbitan, and more preferably sorbitan.

[0034] The carboxylic acid used as the raw material for the partial ester (C) of a polyhydric alcohol preferably has 2 to 30 carbon atoms, more preferably 6 to 24 carbon atoms, and even more preferably 10 to 22 carbon atoms.

[0035] The carboxylic acid may be a saturated or unsaturated carboxylic acid, and may be a linear or branched carboxylic acid. Specific examples include saturated fatty acids such as acetic acid, propionic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, eicosanoic acid, docosanoic acid, tetracosanoic acid, hexacosanoic acid, octacosanoic acid, and triacontanoic acid; and unsaturated fatty acids such as dodecenoic acid, tetradecenoic acid, pentadecenoic acid, hexadecenoic acid (palmitoleic acid, etc.), heptadecenoic acid, octadecenoic acid (oleic acid, etc.), 9,12-octadecadienoic acid (linoleic acid), eicosenoic acid, henicosenoic acid, docosenoic acid, tricosenoic acid, and tetracosenoic acid.

[0036] As the partial ester (C) of polyhydric alcohol, among the above, sorbitan fatty acid esters are preferred, sorbitan stearate and sorbitan oleate are more preferred, and sorbitan oleate is even more preferred.

[0037] The partial ester (C) of polyhydric alcohol may be used alone or in combination of two or more.

[0038] The content of the polyhydric alcohol partial ester (C) in this embodiment is preferably 1 mass% or more, more preferably 2 mass% or more, and even more preferably 3 mass% or more, based on the total amount of the lubricating oil composition. The content of the polyhydric alcohol partial ester (C) is preferably 15 mass% or less, more preferably 10 mass% or less, and even more preferably 7 mass% or less, based on the total amount of the lubricating oil composition. For example, the content of the polyhydric alcohol partial ester (C) is preferably 1 mass% or more and 15 mass% or less, more preferably 2 mass% or more and 10 mass% or less, and even more preferably 3 mass% or more and 7 mass% or less, based on the total amount of the lubricating oil composition.

[0039] When the content of the partial ester (C) of a polyhydric alcohol is within the above-mentioned preferred range, the water detergency and storage stability of the lubricating oil composition are further improved.

[0040] <Water> Examples of water include distilled water, ion-exchanged water, and tap water.

[0041] The water content of this embodiment is greater than 0.1 mass%, preferably greater than 0.2 mass%, and more preferably greater than 0.3 mass%, based on the total amount of the lubricating oil composition. The water content is preferably 5.0 mass% or less, more preferably 3.0 mass% or less, and even more preferably 1.5 mass% or less, based on the total amount of the lubricating oil composition. For example, the water content is greater than 0.1 mass% and 5.0 mass%, preferably 0.2 mass% or more and 3.0 mass% or less, and more preferably 0.3 mass% or more and 1.5 mass% or less, based on the total amount of the lubricating oil composition.

[0042] When the water content is within the above preferred range, the water detergency and storage stability of the lubricating oil composition are further improved.

[0043] <Optional Components> The lubricating oil composition of this embodiment may contain optional components other than the base oil (A), surfactant (B), partial ester of polyhydric alcohol (C), and water described above. Examples of the optional components include an antiwear agent (D), extreme pressure agent, antioxidant, rust inhibitor, corrosion inhibitor, rust inhibitor, and antifoaming agent.

[0044] <<Antiwear Agent (D)>> Examples of the antiwear agent (D) include organic zinc compounds such as zinc dialkyldithiophosphate and zinc dialkyldithiocarbamate; and phosphorus compounds such as phosphate esters, acidic phosphate esters, amine salts of acidic phosphate esters, and phosphites.

[0045] As the phosphorus-based compound, phosphate ester, amine salt of phosphate ester, acidic phosphate ester, amine salt of acidic phosphate ester, chlorinated phosphate ester, phosphite ester and phosphorothionate are preferably used.

[0046] Phosphate esters: Specific examples of phosphate esters include tributyl phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, trioctyl phosphate, trinonyl phosphate, tridecyl phosphate, triundecyl phosphate, tridodecyl phosphate, tritridecyl phosphate, tritetradecyl phosphate, tripentadecyl phosphate, trihexadecyl phosphate, triheptadecyl phosphate, trioctadecyl phosphate, trioleyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, and xylenyl diphenyl phosphate. Tricresyl phosphate and triphenyl phosphate are preferred, and tricresyl phosphate is more preferred.

[0047] Amine Salts of Phosphate Esters Specific examples of amine salts of phosphoric acid esters include the amine salts of the above phosphoric acid esters. Examples of amines include monoamines, polyamines, alkanolamines, etc. Examples of monoamines include primary amines, secondary amines, and tertiary amine monoamines. Specific examples of primary amines include ethylamine, n-propylamine, butylamine, 1-ethylbutylamine, 1,3-diaminopropane, hexylamine, and cyclohexylamine. Specific examples of secondary amines include diethylamine, di-n-propylamine, di-n-butylamine, 4,4'-diaminodiphenylamine, diethylenetriamine, tetraethylenepentamine, and N-(2-aminoethyl)ethanolamine. Specific examples of tertiary amines include dimethylethylamine, diethylmethylamine, triethylamine, and tributylamine.

[0048] Acidic Phosphate Esters Preferred specific examples of acidic phosphate esters include monoalkyl acid esters (wherein the alkyl group may be linear or branched) such as monopropyl acid phosphate, monobutyl acid phosphate, monopentyl acid phosphate, monohexyl acid phosphate, monopeptyl acid phosphate, and monooctyl acid phosphate; mono(alkyl)aryl acid esters (wherein the alkyl group may be linear or branched) such as monophenyl acid phosphate and monocresyl acid phosphate; dialkyl acid esters (wherein the alkyl group may be linear or branched) such as dipropyl acid phosphate, dibutyl acid phosphate, dipentyl acid phosphate, dihexyl acid phosphate, dipeptyl acid phosphate, and dioctyl acid phosphate; and di(alkyl)aryl acid esters (wherein the alkyl group may be linear or branched) such as diphenyl acid phosphate and dicresyl acid phosphate. As the acidic phosphate ester, monoalkyl acid ester phosphate and dialkyl acid ester phosphate are preferred, and monooctyl acid phosphate and dioctyl acid phosphate are more preferred.

[0049] The lubricating oil composition of this embodiment may use one type of antiwear agent alone, or two or more types of antiwear agents may be used in combination. The antiwear agent preferably contains one or more compounds selected from the group consisting of phosphate esters, acidic phosphate esters, and amine salts of acidic phosphate esters. It is more preferable to use a phosphate ester in combination with an acidic phosphate ester or an amine salt of an acidic phosphate ester, and even more preferable to use a phosphate ester in combination with an amine salt of an acidic phosphate ester. The content of the antiwear agent is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, and even more preferably 0.1 mass% or more, based on the total amount of the lubricating oil composition of this embodiment. The content of the antiwear agent is preferably 2.0 mass% or less, more preferably 1.5 mass% or less, and even more preferably 1.0 mass% or less, based on the total amount of the lubricating oil composition of this embodiment. For example, the content of the antiwear agent is preferably 0.01 mass % or more and 2.0 mass % or less, more preferably 0.05 mass % or more and 1.5 mass % or less, and even more preferably 0.1 mass % or more and 1.0 mass % or less, relative to the total amount of the lubricating oil composition of this embodiment.

[0050] When the content of the anti-wear agent is equal to or greater than the above-mentioned preferable lower limit, the abrasion resistance is further improved. When the content of the anti-wear agent is equal to or less than the above-mentioned preferable upper limit, the demulsibility is further improved and the generation of sludge can be further suppressed.

[0051] Examples of extreme pressure agents include sulfur-containing compounds such as molybdenum dialkyldithiocarbamate, dihydrocarbyl polysulfide, sulfurized esters (e.g., sulfurized methyl oleate), thiazole compounds, and thiadiazole compounds. When the lubricating oil composition contains an extreme pressure agent, the content thereof is preferably 0.01 to 3 mass%, and more preferably 0.1 to 1.5 mass%, based on the total amount of the lubricating oil composition. One type of extreme pressure agent may be used alone, or multiple extreme pressure agents may be used in combination.

[0052] Examples of antioxidants include phenolic compounds such as 2,6-di-t-butylphenol and 2,6-di-t-butyl-p-cresol; and amine compounds such as diphenylamine, dialkyldiphenylamine, phenyl-α-naphthylamine, and p-alkylphenyl-α-naphthylamine. When the lubricating oil composition contains an antioxidant, the content thereof is preferably 0.01 to 1.0 mass%, and more preferably 0.1 to 0.8 mass%, based on the total amount of the lubricating oil composition. One type of antioxidant may be used alone, or multiple antioxidants may be used in combination.

[0053] As the corrosion inhibitor, known corrosion inhibitors such as benzotriazole-based compounds, tolyltriazole-based compounds, thiadiazole-based compounds, and imidazole-based compounds can be used. When the lubricating oil composition contains a corrosion inhibitor, the content thereof is preferably 0.01 to 5 mass%, more preferably 0.01 to 0.05 mass%, based on the total amount of the lubricating oil composition. The corrosion inhibitor may be used alone, or multiple corrosion inhibitors may be used in combination.

[0054] Specific examples of the rust inhibitor include salts of fatty acids such as oleic acid, sulfonates such as dinonylnaphthalene sulfonate, amines and derivatives thereof, and the like.

[0055] Examples of the antifoaming agent include silicone-based antifoaming agents.

[0056] [Uses] The lubricating oil composition of this embodiment has good water cleanability and storage stability, and is therefore particularly suitable for use in spinning machines, looms, knitting machines, or food, drug, or cosmetic manufacturing equipment.

[0057] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0058] <Preparation of Lubricating Oil Compositions> Lubricating oil compositions of each example were prepared by mixing the components shown in Tables 1 and 2. In Tables 1 and 2, the abbreviations have the following meanings. The values ​​in brackets [ ] are mass % relative to the total amount of the lubricating oil composition (100 mass %).

[0059] (1) Base oil (A) (A)-1: Mineral oil (API Group I base oil, flash point: 254°C, kinematic viscosity at 40°C: 63.1 m2 / s, sulfur content: 0.40% by mass)

[0060] (2) Surfactants (B) (B)-1: Polyoxyalkylene alkyl ether (HLB: 12.6, manufactured by Sanyo Chemical Industries, Ltd., Naroacty CL-85) (B)-2: Polyoxyalkylene alkyl ether (HLB: 8.9, manufactured by Sanyo Chemical Industries, Ltd., Naroacty CL-40) (B)-3: Polyoxyalkylene alkyl ether (HLB: 12.5, manufactured by Kao Corporation, Emulgen L106)

[0061] (3) Partial ester of polyhydric alcohol (C) (C)-1: Sorbitan oleate

[0062] (4) Antiwear Agents (D) (D)-1: Mixture of monooctyl acid phosphate and dioctyl acid phosphate (ADEKA GROUP FMP-350 manufactured by ADEKA Corporation) (D)-2: Tricresyl phosphate (D)-3: Triphenyl phosphate (D)-4: Monostearyl phosphate (D)-5: Dibutyl phosphate (D)-6: Alkyl (C=11-14, branched) amine (monohexyl and dihexyl) phosphate

[0063] (5) Additives X-1: 2,6-di-t-butyl-p-cresol X-2: Benzotriazole X-3: Nonylphenoxyacetic acid X-4: Sodium sulfonate X-5: Methyl sulfide oleate

[0064] [Evaluation of Detergency] The mass of a cotton ball (6 cm x 8 cm) was measured. 1.5 g of each lubricating oil composition of each example was dropped onto the cotton ball. 500 mL of water was placed in a 1 L beaker and stirred at 400 rpm. The cotton ball onto which each lubricating oil composition of each example had been dropped was placed in the 1 L beaker and stirred for 2 minutes and 30 seconds. The cotton ball was removed from the 1 L beaker and left to stand in a 60°C thermostatic bath for 5 hours to remove moisture from the cotton ball. The weight of the cotton ball removed from the thermostatic bath was measured. The oil removal rate was calculated using the following formula: (Oil removal rate, %) = {(Weight of cotton ball after test) - (Weight of cotton ball before test)} / (Amount of oil dropped onto cotton ball) x 100. The results are shown in Tables 1 and 2. An oil removal rate of less than 95% was considered to have failed to achieve the required performance.

[0065] [Evaluation of storage stability] 100 mL of each lubricating oil composition was placed in a screw bottle and allowed to stand for 4 weeks at various temperatures (0° C., room temperature, 60° C.). After the test, if no cloudiness or precipitate was observed, the composition was rated as "A".

[0066]

[0067]

[0068] As shown in Tables 1 and 2, the lubricating oil compositions of the Examples were better in water detergency and storage stability than the lubricating oil compositions of the Comparative Examples.

[0069] [Falex Test Results] In accordance with ASTM D2670, the lubricating oil compositions of Examples 4 to 6 and the lubricating oil compositions of Comparative Examples 2 to 4 were applied to test specimens, and the wear amounts of the test specimens were measured under the following measurement conditions. The results are shown in Table 3. Break-in: 250 lbs / 290 rpm / 5 min / room temperature Main test: 700 lbs / 290 rpm / 15 min / room temperature

[0070]

[0071] As shown in Table 3, the lubricating oil compositions of Examples 4 to 6 had better wear resistance than the lubricating oil compositions of Comparative Examples 2 to 4.

[0072] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Addition, omission, substitution, and other modifications of the configuration are possible within the scope of the spirit of the present invention. The present invention is not limited by the above description, but is limited only by the scope of the appended claims.

Claims

1. A lubricating oil composition comprising a base oil (A), a surfactant (B), a partial ester of a polyhydric alcohol (C), and water, wherein the content of the water is greater than 0.1 mass% based on the total amount of the lubricating oil composition.

2. The lubricating oil composition according to claim 1, further comprising an antiwear agent (D).

3. The lubricating oil composition according to claim 2, wherein the antiwear agent (D) comprises one or more compounds selected from the group consisting of phosphoric acid esters, acidic phosphoric acid esters, and amine salts of acidic phosphoric acid esters.

4. The lubricating oil composition according to claim 2, wherein the antiwear agent (D) comprises a phosphoric acid ester and an acidic phosphoric acid ester or an amine salt of an acidic phosphoric acid ester.

5. The lubricating oil composition according to claim 1 or 2, wherein the HLB of the surfactant (B) is 10.0 to 16.

0.

6. The lubricating oil composition according to claim 1 or 2, wherein the partial ester (C) of a polyhydric alcohol comprises a sorbitan fatty acid ester.

7. The lubricating oil composition according to claim 1 or 2, which is used in spinning machines, looms, knitting machines, or food, drug, or cosmetic manufacturing equipment.

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