Lubricating oil composition

Abstract

Provided is a lubricating oil composition which contains a base oil (A) and a compound (B) selected from among a carboxylic acid ester, a carboxylic acid, an alcohol and an ether, and which has a phase transition pressure of 70 MPa or less, as calculated using a prescribed procedure.

Description

lubricating oil composition

[0001] The present invention relates to a lubricating oil composition.

[0002] Lubricating oils are used in a variety of situations, such as for lubricating sliding parts in various devices, for cooling heat-generating equipment such as engines, and for metal processing to improve workability during metal processing. For example, Patent Document 1 describes a lubricating oil composition for plastic processing, such as press working and cold forging, that contains 5 to 99% by mass of a zinc dithiophosphate having a specific structure, 1 to 95% by mass of a metal salt of sulfonic acid, and 0 to 80% by mass of a base oil, with the aim of providing a lubricating oil composition for plastic processing, such as press working and cold forging, that has excellent lubrication properties and can be used even under severe lubrication conditions.

[0003] JP 2013-173957 A

[0004] In this situation, there is a demand for new lubricating oils that can exhibit good performance depending on the individual application.

[0005] The present invention provides a lubricating oil composition comprising a base oil and a compound selected from a carboxylic acid ester, a carboxylic acid, an alcohol, and an ether, and having a phase transition pressure calculated by a predetermined procedure adjusted to a predetermined value or less. That is, the present invention provides the following [1] to

[13] . [1] A lubricating oil composition comprising a base oil (A) and a compound (B) selected from a carboxylic acid ester, a carboxylic acid, an alcohol, and an ether, and having a phase transition pressure of 70 MPa or less, calculated by the following procedures (i) to (iv). Procedure (i): Fill a cylindrical cell having a constant cross-sectional area with the lubricating oil composition at 30°C. Procedure (ii): After procedure (i), a load is applied to the lubricating oil composition in the cell in the vertical direction via a plunger, and the lubricating oil composition is pressed into the cell at a rate of 0.01 mm / s. A correlation graph is obtained between the pressure P in the cell and the plunger insertion length Y, with the pressure P (MPa) calculated from the load / cross-sectional area on the horizontal axis and the plunger insertion length Y (mm) in the vertical direction on the vertical axis. - Operation (iii): In the correlation graph obtained in operation (ii), the gradient [ΔX / ΔY] of the tangent line at the point where the pressure P in the cell becomes n (MPa) (n is an integer of 1 or more) is calculated for each increment of 1 MPa from 0 MPa. - Operation (iv): When the pressure P in the cell changes from n-1 (MPa) to n (MPa), the rate of change in the gradient [ΔX / ΔY] of the tangent line calculated from the following formula (1) exceeds 2% for the first time, and this is taken as the phase transition pressure. Formula (1): Rate of change (%) of the gradient [ΔX / ΔY] of the tangent line = ([ΔX / ΔY] ｎ −[ΔX / ΔY] ｎ－１ ) / 1(MPa)×100 (In the above formula (1), [ΔX / ΔY] ｎ indicates the slope [ΔX / ΔY] of the tangent at the point where the pressure P in the cell is n (MPa) in the correlation graph. [ΔX / ΔY] ｎ－１indicates the slope [ΔX / ΔY] of the tangent line at the point in the correlation graph where the pressure P in the cell is n-1 (MPa). [2] The lubricating oil composition according to the above item [1], wherein component (A) comprises a paraffinic mineral oil (A1). [3] The lubricating oil composition according to the above item [1] or [2], wherein the total content of component (A) and component (B) is 70 to 100 mass% based on the total amount of the lubricating oil composition. [4] The lubricating oil composition according to any one of the above items [1] to [3], wherein the total content of lubricating oil additives other than component (B) is less than 90 parts by mass per 100 parts by mass of the total amount of component (B). [5] The lubricating oil composition according to any one of the above items [1] to [4], wherein the content of the sulfur-based extreme pressure agent is less than 50 parts by mass per 100 parts by mass of the total amount of component (B). [6] The lubricating oil composition according to any one of [1] to [5] above, wherein the carboxylic acid ester is a saturated or unsaturated chain carboxylic acid ester, the carboxylic acid is a saturated or unsaturated chain carboxylic acid, the alcohol is a saturated or unsaturated chain alcohol, and the ether is a saturated or unsaturated chain ether. [7] The lubricating oil composition according to any one of [1] to [5] above, wherein the carboxylic acid ester is a saturated chain carboxylic acid ester, the carboxylic acid is a saturated chain carboxylic acid, the alcohol is a saturated chain alcohol, and the ether is a saturated chain ether. [8] The lubricating oil composition according to any one of [1] to [7] above, wherein component (B) comprises a compound represented by any one of the following general formulas (b-1) to (b-4): (In the above formula, R １ , R ２ and R ３ are each independently an alkyl group having 10 to 40 carbon atoms. ａ , R ｂ and R ｃ are each independently an alkyl group having 1 to 30 carbon atoms. ｂ and R ｃThe total number of carbon atoms in the lubricating oil composition is 10 or more. [9] The lubricating oil composition according to any one of the above [1] to [8], wherein the content of component (B) is 1.0 mass% or more based on the total amount of the lubricating oil composition.

[10] The kinematic viscosity of the lubricating oil composition at 40°C is ２ / s or less.

[11] The lubricating oil composition according to any one of the above [1] to [9], further comprising a pour point depressant.

[12] The lubricating oil composition according to any one of the above [1] to

[11] , which is used in metalworking.

[13] A lubricating oil consisting essentially of a compound (B) selected from a carboxylic acid ester, a carboxylic acid, an alcohol, and an ether, and having a phase transition pressure of 70 MPa or less as calculated by the following procedures (i) to (iv): Procedure (i): Fill a cylindrical cell having a constant cross-sectional area with the lubricating oil composition at 30°C. Step (ii): After step (i), a load is applied to the lubricating oil composition in the cell in the vertical direction via a plunger, and the lubricating oil composition is pressed in at a speed of 0.01 mm / s. The horizontal axis represents the pressure P (MPa) in the cell, calculated from the load / cross-sectional area, and the vertical axis represents the plunger pressing length Y (mm). A correlation graph is obtained between the pressure P in the cell and the plunger pressing length Y. Step (iii): In the correlation graph obtained in step (ii), the slopes [ΔX / ΔY] of the tangent lines at points where the pressure P in the cell becomes n (MPa) (n is an integer of 1 or more) are calculated for each increment of the pressure P in the cell from 0 MPa to 1 MPa. Step (iv): The phase transition pressure is defined as the pressure P in the cell at which the rate of change in the slope [ΔX / ΔY] of the tangent line calculated from the following formula (1) when the pressure P in the cell changes from n-1 (MPa) to n (MPa) exceeds 2% for the first time. Equation (1): Rate of change (%) of tangent slope [ΔX / ΔY] = ([ΔX / ΔY] ｎ −[ΔX / ΔY] ｎ－１ ) / 1(MPa)×100 (In the above formula (1), [ΔX / ΔY] ｎ indicates the slope [ΔX / ΔY] of the tangent at the point where the pressure P in the cell is n (MPa) in the correlation graph. [ΔX / ΔY] ｎ－１indicates the slope [ΔX / ΔY] of the tangent line at the point where the pressure P in the cell is n-1 (MPa) in the correlation graph.)

[14] The lubricating oil according to

[13] above, wherein the content of components other than component (B) is less than 1.0 mass% based on the total amount of the lubricating oil.

[15] The lubricating oil according to

[13] above or

[14] above, which is used for metalworking.

[0006] The lubricating oil composition or lubricating oil according to a preferred embodiment of the present invention can exhibit good performance depending on the particular application, for example, when used as a metalworking oil, it can exhibit good metal workability.

[0007] 1 is a schematic diagram showing an example of the structure of a high-pressure measuring tester for measuring the phase transition pressure of a lubricating oil composition to be measured or a lubricating oil described below. It is a correlation graph between the pressure P in the cell and the plunger depression length Y obtained through operations (i) to (iv) for the sample oil of Example 1, and a graph showing the rate of change of the slope [ΔX / ΔY] of the tangent line with respect to the pressure P in the cell.

[0008] With respect to the numerical ranges described herein, the upper and lower limits can be arbitrarily combined. For example, when a numerical range is described as "preferably 30 to 100, more preferably 40 to 80," the ranges "30 to 80" and "40 to 100" are also included in the numerical ranges described herein. Furthermore, when a numerical range is described as "preferably 30 or more, more preferably 40 or more, and preferably 100 or less, more preferably 80 or less," the ranges "30 to 80" and "40 to 100" are also included in the numerical ranges described herein. Furthermore, as a numerical range described herein, for example, "60 to 100" means a range of "60 or more (60 or more) and 100 or less (100 or less)."

[0009] In this specification, the kinematic viscosity and viscosity index refer to values ​​measured and calculated in accordance with JIS K2283:2000.

[0010] [Configuration of Lubricating Oil Composition] The lubricating oil composition of the present invention comprises a base oil (A) and a compound (B) selected from a carboxylic acid ester, a carboxylic acid, an alcohol, and an ether, and has a phase transition pressure of 70 MPa or less, as calculated by the following procedures (i) to (iv): Procedure (i): Fill a cylindrical cell of constant cross-sectional area with the lubricating oil composition at 30°C. Procedure (ii): After procedure (i), a load is applied vertically to the lubricating oil composition in the cell via a plunger, and the lubricating oil composition is pressed into the cell at a rate of 0.01 mm / s. A correlation graph is obtained between the pressure P (MPa) in the cell, calculated from the load / cross-sectional area, and the plunger's vertical insertion length Y (mm), with the horizontal axis representing the pressure P in the cell and the plunger's insertion length Y. - Operation (iii): In the correlation graph obtained in operation (ii), the gradient [ΔX / ΔY] of the tangent line at the point where the pressure P in the cell becomes n (MPa) (n is an integer of 1 or more) is calculated for each increment of 1 MPa from 0 MPa. - Operation (iv): When the pressure P in the cell changes from n-1 (MPa) to n (MPa), the rate of change in the gradient [ΔX / ΔY] of the tangent line calculated from the following formula (1) exceeds 2% for the first time, and this is taken as the phase transition pressure. Formula (1): Rate of change (%) of the gradient [ΔX / ΔY] of the tangent line = ([ΔX / ΔY] ｎ −[ΔX / ΔY] ｎ－１ ) / 1(MPa)×100 In the above formula (1), [ΔX / ΔY] ｎ indicates the slope [ΔX / ΔY] of the tangent at the point where the pressure P in the cell is n (MPa) in the correlation graph. [ΔX / ΔY] ｎ－１ indicates the slope [ΔX / ΔY] of the tangent line at the point where the pressure P in the cell is n-1 (MPa) in the correlation graph.

[0011] The procedure for calculating the phase transition pressure through steps (i) to (iv) will be described below. FIG. 1 is a schematic diagram showing an example of the structure of a high-pressure measuring tester for measuring the phase transition pressure of a lubricating oil composition to be measured. The measurement targets include not only lubricating oil compositions but also the lubricating oils described below. FIG. 2 is a correlation graph between the pressure P in the cell and the plunger depression length Y, obtained through steps (i) to (iv) for the sample oil of Example 1 described below, and a graph showing the rate of change of the tangent slope [ΔX / ΔY] with respect to the pressure P in the cell.

[0012] The high-pressure measurement tester 1 shown in Figure 1 comprises a pressure vessel outer cylinder 11, a pressure vessel inner cylinder 12 inserted into the outer cylinder 11, a pair of plungers 13 inserted into the space inside the inner cylinder 12, a columnar cell 14 surrounded by the inside side of the inner cylinder 12 held between the pair of plungers 13 and filled with the substance to be measured, and a holder 15 for holding these components. First, in operation (i), the columnar cell 14 of the high-pressure measurement tester 1 of Figure 1 is filled with the lubricating oil composition to be measured at 30°C.

[0013] In operation (ii), a load is applied to the lubricating oil composition in the cell 14 in the vertical direction via the plunger 13. The load can be applied using a compression and tension tester or the like, separate from the high-pressure measurement tester 1. When the cell 14 is pressed vertically at a speed of 0.01 mm / s under a load, correlation information is obtained between the pressure P (MPa) in the cell 14 calculated from the load / cross-sectional area and the vertical plunge length Y (mm) of the plunger 13. Then, a correlation graph is obtained with the pressure P (MPa) in the cell on the horizontal axis and the plunge length Y (mm) of the plunger on the vertical axis. In FIG. 2, the graph indicated by the solid line corresponds to the "correlation graph."

[0014] In operation (iii), the slopes [ΔX / ΔY] of the tangents at points where the intracellular pressure P is n (MPa) (n is an integer of 1 or greater) in the correlation graph obtained in operation (ii) are calculated for each increment of 1 MPa from 0 MPa. In FIG. 2, the correlation graph between the intracellular pressure P and the indentation length Y in the range of intracellular pressure P from 15 to 28 MPa is shown by a solid line. In operation (iii), the slopes [ΔX / ΔY] of the tangents at points plotted in increments of 1 MPa in the range of intracellular pressure P from 15 to 28 MPa in FIG. 2 are calculated.

[0015] In operation (iv), the rate of change of the slope of the tangent line [ΔX / ΔY] calculated from the following formula (1) when the pressure P in the cell changes from n-1 (MPa) to n (MPa) is calculated. The dashed line in FIG. 2 shows the rate of change of the slope of the tangent line [ΔX / ΔY]. For example, the rate of change of the slope of the tangent line [ΔX / ΔY] when the pressure P in the cell changes from 25 (MPa) to 26 (MPa) is calculated by multiplying the slope of the tangent line [ΔX / ΔY] at the point where the pressure P in the cell is 26 MPa by the following formula (1): ２６ and the slope of the tangent line [ΔX / ΔY] at the point where the pressure P in the cell is 25 MPa. ２５ From the value of ([ΔX / ΔY]) ２６ −[ΔX / ΔY] ２５ ) / 1 (MPa) × 100. According to the graph of the rate of change shown by the dashed line in Figure 2, the rate of change exceeds 2% when the pressure P in the cell is between 25 MPa and 26 MPa. Therefore, the phase transition pressure of this sample oil is calculated to be "26 MPa."

[0016] The lubricating oil composition of one embodiment of the present invention can improve lubricity in environments where high surface pressure is applied. Conventional lubricating oil compositions have had the problem that, as the surface pressure increases, the lubrication conditions become more severe, making it impossible to maintain an oil film and resulting in a decrease in lubricity. In contrast, the lubricating oil composition of one embodiment of the present invention is adjusted so that the phase transition pressure calculated by the above steps (i) to (iv) is equal to or less than a predetermined value, and a phase transition occurs at a relatively early stage in an environment accompanied by increased surface pressure, forming a strong oil film and achieving good lubricity.

[0017] In one embodiment of the lubricating oil composition of the present invention, from the viewpoint of facilitating the formation of a strong oil film at an early stage and providing a lubricating oil composition with improved lubricity, the phase transition pressure of the lubricating oil composition is 70 MPa or less, preferably 65 MPa or less, more preferably 63 MPa or less, more preferably 60 MPa or less, even more preferably 57 MPa or less, even more preferably 55 MPa or less, still more preferably 53 MPa or less, and particularly preferably 50 MPa or less, and may further be 45 MPa or less, 40 MPa or less, 35 MPa or less, or 30 MPa or less, or may be 1 MPa or more, 3 MPa or more, 5 MPa or more, 7 MPa or more, 10 MPa or more, 12 MPa or more, or 15 MPa or more.

[0018] The kinematic viscosity at 40°C of the lubricating oil composition of one embodiment of the present invention is 500 mm ２ / s or less, 400mm ２ / s or less, 300mm ２ / s or less, 250mm ２ / s or less, 200mm ２ / s or less, 150mm ２ / s or less, 100mm ２ / s or less, 90mm ２ / s or less, 80mm ２ / s or less, 70mm ２ / s or less, 60mm ２ / s or less, 50mm ２ / s or less, 40mm ２ / s or less, 30mm ２ / s or less, 20mm ２ / s or less, 15mm ２ / s or less, 12mm ２ / s or less, 10mm ２ / s or less, or 9.0 mm ２ / s or less, and from the viewpoint of maintaining a strong oil film and reducing evaporation loss, it is preferable to set the oil flow rate to 2.0 mm ２ / s or more, 2.5mm ２ / s or more, 3.0mm ２ / s or more, 3.5mm ２ / s or more, 4.0mm ２ / s or more, 4.5mm ２ / s or more, 5.0mm ２ / s or more, 5.5mm ２ / s or more, 6.0mm ２ / s or more, or 6.5 mm ２ It is preferable that the ratio is 1 / s or more.

[0019] The phase transition pressure of the lubricating oil composition of one embodiment of the present invention can be adjusted to fall within the above range, for example, by adjusting the types of components (A) and (B) and the ratio of components (A) to (B) depending on the types of components (A) and (B). Specific methods for adjustment are described below.

[0020] The lubricating oil composition of one embodiment of the present invention may contain lubricating oil additives other than component (B) to the extent that the effects of the present invention are not impaired. In the lubricating oil composition of one embodiment of the present invention, from the viewpoint of facilitating the formation of a strong oil film at an early stage in the pressure rise process and providing a lubricating oil composition with improved lubricity, the total content of component (A) and component (B) is preferably 70 to 100 mass%, more preferably 75 to 100 mass%, more preferably 80 to 100 mass%, even more preferably 85 to 100 mass%, even more preferably 90 to 100 mass%, still more preferably 95 to 100 mass%, and particularly preferably 98 to 100 mass%, based on the total amount (100 mass%) of the lubricating oil composition. Details of each component contained in the lubricating oil composition of one embodiment of the present invention will be described below.

[0021] <Component (A): Base Oil> The base oil (A) used in one embodiment of the present invention may be one or more selected from mineral oils and synthetic oils. Examples of mineral oils include atmospheric residues obtained by atmospheric distillation of crude oils such as paraffinic crude oil, intermediate crude oil, and naphthenic crude oil; distillates obtained by vacuum distillation of these atmospheric residues; and refined oils obtained by subjecting the distillates to one or more refining treatments such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining.

[0022] Examples of synthetic oils include poly-α-olefins such as α-olefin homopolymers or α-olefin copolymers (for example, α-olefin copolymers having 8 to 14 carbon atoms, such as ethylene-α-olefin copolymers); isoparaffins; polyalkylene glycols; ester-based oils such as polyol esters, dibasic acid esters, and phosphate esters; ether-based oils such as polyphenyl ethers; alkylbenzenes; alkylnaphthalenes; and synthetic oils (GTL) obtained by isomerizing wax produced from natural gas by the Fischer-Tropsch process or the like (GTL wax (Gas To Liquids WAX)).

[0023] Among these, the base oil (A) used in one embodiment of the present invention preferably contains a paraffinic mineral oil (A1) from the viewpoint of preparing a lubricating oil composition having a phase transition pressure in the above-mentioned range. From the above viewpoint, the content of the paraffinic mineral oil (A1) in the base oil (A) used in one embodiment of the present invention is preferably 60 to 100 mass%, more preferably 70 to 100 mass%, even more preferably 80 to 100 mass%, still more preferably 90 to 100 mass%, and particularly preferably 95 to 100 mass%, based on 100 mass% of the total amount of the base oil (A).

[0024] The kinematic viscosity at 40°C of the base oil (A) used in one embodiment of the present invention is preferably 4.0 mm ２ / s or more, more preferably 4.5 mm ２ / s or more, more preferably 5.0 mm ２ / s or more, more preferably 5.5 mm ２ / s or more, and even more preferably 6.0 mm ２ / s or more, particularly preferably 6.5 mm ２ / s or more, and preferably 100 mm ２ / s or less, more preferably 80 mm ２ / s or less, more preferably 60 mm ２ / s or less, more preferably 50 mm ２ / s or less, more preferably 40 mm ２ / s or less, and even more preferably 30 mm ２ / s or less, particularly preferably 20 mm ２ / s or less, and further, 17 mm２ / s or less, 15mm ２ / s or less, 12mm ２ / s or less, or 10 mm ２ / s or less.

[0025] The viscosity index of the base oil (A) used in one embodiment of the present invention is preferably 10 or more, more preferably 20 or more, more preferably 30 or more, even more preferably 40 or more, still more preferably 50 or more, and particularly preferably 60 or more, and may be 200 or less, 170 or less, 150 or less, 120 or less, 100 or less, 95 or less, 90 or less, or 85 or less. In one embodiment of the present invention, when a mixed oil of two or more base oils is used as the base oil (A), the kinematic viscosity and viscosity index of the mixed oil are preferably within the above ranges. Furthermore, the weighted average value of the kinematic viscosity or viscosity index calculated from the kinematic viscosity or viscosity index of each base oil constituting the mixed oil and its content is preferably within the above range.

[0026] In the lubricating oil composition of one embodiment of the present invention, the content of component (A) based on the total amount (100 mass%) of the lubricating oil composition may be more than 0 mass%, 0.1 mass% or more, 0.5 mass% or more, 1.0 mass% or more, 3.0 mass% or more, 5.0 mass% or more, 10.0 mass% or more, 15.0 mass% or more, 20.0 mass% or more, 25.0 mass% or more, 30.0 mass% or more, 35.0 mass% or more, 40.0 mass% or more, 45.0 mass% or more, 50.0 mass% or more, 55.0 mass% or more, 60.0 mass% or more, 65.0 mass% or more, 70.0 mass% or more, 75.0 mass% or more, 80.0 mass% or more, 85.0 mass% or more, or 90.0 mass% or more. Also, 99.0 mass% or less, 98.5 mass% or less, 98.0 mass% or less, 97.5 mass% or less, 96.0 mass% or less, 95.0 mass% or less, 90.0 mass% or less, 85.0 mass% or less, 80.0 mass% or less, 75.0 mass% or less, 70.0 mass% or less, 65.0 mass% or less, 60.0 mass% or less, 55.0 It may be less than or equal to 50.0 mass%, 45.0 mass% or less, 40.0 mass% or less, 35.0 mass% or less, 30.0 mass% or less, 25.0 mass% or less, 20.0 mass% or less, 15.0 mass% or less, 10.0 mass% or less, 9.0 mass% or less, 8.0 mass% or less, 7.0 mass% or less, or 6.0 mass% or less.

[0027] In the lubricating oil composition of one embodiment of the present invention, the content of component (A) is preferably adjusted depending on the type of component (B) so that the phase transition pressure is within the above-mentioned range. For example, when component (B) contains a carboxylic acid ester or carboxylic acid having a melting point of less than 30°C, the content of component (A) is preferably less than 40.0 mass%, more preferably 35.0 mass% or less, more preferably 30.0 mass% or less, even more preferably 25.0 mass% or less, even more preferably 20.0 mass% or less, still more preferably 15.0 mass% or less, particularly preferably 10.0 mass% or less, and may even be 9.0 mass% or less, 8.0 mass% or less, 7.0 mass% or less, or 6.0 mass% or less, or may be more than 0 mass%, 0.1 mass% or more, 0.5 mass% or more, 1.0 mass% or more, 1.5 mass% or more, 2.0 mass% or more, 2.5 mass% or more, or 3.0 mass% or more, based on the total amount (100 mass%) of the lubricating oil composition.

[0028] When component (B) contains a carboxylic acid ester or carboxylic acid having a melting point of 30°C or higher, the content of component (A) is, based on the total amount (100 mass%) of the lubricating oil composition, preferably less than 80.0 mass%, more preferably 78.0 mass% or less, more preferably 75.0 mass% or less, even more preferably 73.0 mass% or less, even more preferably 70.0 mass% or less, still more preferably 68.0 mass% or less, and particularly preferably 65.0 mass% or less, and may also be more than 0 mass%, 0.1 mass% or more, 0.5 mass% or more, 1.0 mass% or more, 3.0 mass% or more, 5.0 mass% or more, 10.0 mass% or more, 15.0 mass% or more, 20.0 mass% or more, 25.0 mass% or more, 30.0 mass% or more, 35.0 mass% or more, 40.0 mass% or more, 45.0 mass% or more, or 50.0 mass% or more.

[0029] When component (B) contains an alcohol or ether having a melting point of less than 30°C, the content of component (A) is, based on the total amount (100 mass%) of the lubricating oil composition, preferably less than 40.0 mass%, more preferably 35.0 mass% or less, more preferably 30.0 mass% or less, even more preferably 25.0 mass% or less, even more preferably 20.0 mass% or less, still more preferably 15.0 mass% or less, particularly preferably 10.0 mass% or less, and may even be 9.0 mass% or less, 8.0 mass% or less, 7.0 mass% or less, or 6.0 mass% or less, or may be more than 0 mass%, 0.1 mass% or more, 0.5 mass% or more, 1.0 mass% or more, 1.5 mass% or more, 2.0 mass% or more, 2.5 mass% or more, or 3.0 mass% or more.

[0030] When component (B) contains an alcohol or ether having a melting point of 30°C or higher but lower than 50°C, the content of component (A) is, based on the total amount (100 mass%) of the lubricating oil composition, preferably 95.0 mass% or less, more preferably 92.0 mass% or less, more preferably 90.0 mass% or less, even more preferably 87.0 mass% or less, still more preferably 85.0 mass% or less, and particularly preferably 82.0 mass% or less, and may also be more than 0 mass%, 0.1 mass% or more, 0.5 mass% or more, 1.0 mass% or more, 3.0 mass% or more, 5.0 mass% or more, 10.0 mass% or more, 15.0 mass% or more, 20.0 mass% or more, 25.0 mass% or more, 30.0 mass% or more, 35.0 mass% or more, 40.0 mass% or more, 45.0 mass% or more, 50.0 mass% or more, 55.0 mass% or more, or 60.0 mass% or more.

[0031] When component (B) contains an alcohol or ether having a melting point of 50°C or higher, the content of component (A) is, based on the total amount (100 mass%) of the lubricating oil composition, preferably 99.0 mass% or less, more preferably 98.5 mass% or less, more preferably 98.0 mass% or less, even more preferably 97.5 mass% or less, still more preferably 97.0 mass% or less, and particularly preferably 96.5 mass% or less, and may also be 60.0 mass% or more, 65.0 mass% or more, 70.0 mass% or more, 75.0 mass% or more, 80.0 mass% or more, 85.0 mass% or more, or 90.0 mass% or more.

[0032] <Component (B): Compound> The lubricating oil composition of one embodiment of the present invention comprises a compound (B) selected from a carboxylic acid ester, a carboxylic acid, an alcohol, and an ether. From the viewpoint of obtaining a lubricating oil composition having a phase transition pressure within the above-mentioned range, it is preferable that component (B) used in one embodiment of the present invention corresponds to a "phase transition compound" that is liquid under normal pressure (under a pressure of 0.1 MPa) but has a phase transition pressure calculated via the above-mentioned procedures (i) to (iv).

[0033] From the viewpoint of obtaining a lubricating oil composition having a phase transition pressure within the above-mentioned range, the content of the phase transition compound in component (B) used in one embodiment of the present invention is preferably 60 to 100 mass %, more preferably 70 to 100 mass %, even more preferably 80 to 100 mass %, still more preferably 90 to 100 mass %, and particularly preferably 95 to 100 mass %, based on 100 mass % of the total amount of component (B).

[0034] From the viewpoint of obtaining a lubricating oil composition having a phase transition pressure within the above-mentioned range, the carboxylic acid ester used as component (B) in one embodiment of the present invention is preferably a saturated or unsaturated chain carboxylic acid ester, more preferably a saturated chain carboxylic acid ester. From the viewpoint of obtaining a lubricating oil composition having a phase transition pressure within the above-mentioned range, the carboxylic acid used as component (B) in one embodiment of the present invention is preferably a saturated or unsaturated chain carboxylic acid, more preferably a saturated chain carboxylic acid. From the viewpoint of obtaining a lubricating oil composition having a phase transition pressure within the above-mentioned range, the alcohol used as component (B) in one embodiment of the present invention is preferably a saturated or unsaturated chain alcohol, more preferably a saturated chain alcohol. From the viewpoint of obtaining a lubricating oil composition having a phase transition pressure within the above-mentioned range, the ether used as component (B) in one embodiment of the present invention is preferably a saturated or unsaturated chain ether, more preferably a saturated chain ether.

[0035] Furthermore, from the viewpoint of obtaining a lubricating oil composition having a phase transition pressure within the above-mentioned range, component (B) used in one embodiment of the present invention preferably contains a compound having an alkyl group having 10 to 40 carbon atoms. In other words, component (B) used in one embodiment of the present invention more preferably contains a compound represented by any one of the following general formulas (b-1) to (b-4):

[0036] In the formulas (b-1) to (b-3), R １ , R ２ and R ３ are each independently an alkyl group having 10 to 40 carbon atoms. ａ , R ｂ and R ｃare each independently an alkyl group having 1 to 30 carbon atoms. ｂ and R ｃ The total number of carbon atoms is 10 or more.

[0037] R １ , R ２ and R ３ The alkyl group that can be selected as R may be a linear alkyl group or a branched alkyl group, but is preferably a linear alkyl group from the viewpoint of obtaining a lubricating oil composition having a phase transition pressure within the above-mentioned range. １ , R ２ and R ３ The number of carbon atoms in the alkyl group that can be selected as the alkyl group is preferably 10 or more, more preferably 11 or more, even more preferably 12 or more, still more preferably 14 or more, and particularly preferably 16 or more, from the viewpoint of obtaining a lubricating oil composition having a phase transition pressure in the above-mentioned range, and is preferably 40 or less, more preferably 35 or less, even more preferably 30 or less, still more preferably 25 or less, and particularly preferably 20 or less.

[0038] Specific R １ , R ２ and R ３ Examples of the alkyl group include decyl, undecyl, dodecyl (lauryl), tridecyl, tetradecyl (myristyl), pentadecyl, hexadecyl, heptadecyl, octadecyl (stearyl), icosyl, and tetracosyl. Among these, from the viewpoint of obtaining a lubricating oil composition having a phase transition pressure in the above-mentioned range, R １ , R ２ and R ３ are each independently preferably an undecyl group, a dodecyl group (lauryl group), a tridecyl group, a tetradecyl group (myristyl group), a hexadecyl group, a heptadecyl group, or an octadecyl group (stearyl group).

[0039] Also, R ａ , R ｂ and R ｃThe alkyl group that can be selected as R may be a linear alkyl group or a branched alkyl group, but is preferably a linear alkyl group from the viewpoint of obtaining a lubricating oil composition having a phase transition pressure within the above-mentioned range. ａ , R ｂ and R ｃ The number of carbon atoms in the alkyl group that can be selected as above is 1 to 30, more preferably 1 to 25, and even more preferably 1 to 20, from the viewpoint of obtaining a lubricating oil composition having a phase transition pressure in the above-mentioned range.

[0040] In addition, R in the formula (b-1) ａ The number of carbon atoms in the alkyl group that can be selected as above is preferably 1 to 10, more preferably 1 to 6, even more preferably 1 to 4, still more preferably 1 to 2, and particularly preferably 1, from the viewpoint of obtaining a lubricating oil composition having a phase transition pressure in the above-mentioned range.

[0041] In addition, R in the formula (b-4) ｂ and R ｃ The total number of carbon atoms is 10 or more, preferably 11 or more, more preferably 12 or more, even more preferably 14 or more, and still more preferably 16 or more, and is preferably 40 or less, more preferably 35 or less, even more preferably 30 or less, still more preferably 25 or less, and particularly preferably 20 or less.

[0042] Specific R ａ , R ｂ and R ｃ Examples of the aryl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, s-butyl, t-butyl, isobutyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, and decyl groups. ａis preferably a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, or an n-octyl group, more preferably a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, or an n-hexyl group, even more preferably a methyl group, an ethyl group, an n-propyl group, or an n-butyl group, still more preferably a methyl group or an ethyl group, and particularly preferably a methyl group.

[0043] In the lubricating oil composition of one embodiment of the present invention, the content of the compound represented by any one of general formulas (b-1) to (b-4) in component (B) is preferably 60 to 100 mass%, more preferably 70 to 100 mass%, even more preferably 80 to 100 mass%, still more preferably 90 to 100 mass%, and particularly preferably 95 to 100 mass%, relative to the total amount (100 mass%) of component (B) contained in the lubricating oil composition.

[0044] From the viewpoint of obtaining a lubricating oil composition having a phase transition pressure in the above-mentioned range, the melting point of component (B) used in the lubricating oil composition of one embodiment of the present invention is preferably 5°C or higher, more preferably 10°C or higher, even more preferably 15°C or higher, and is preferably 90°C or lower, more preferably 80°C or lower, even more preferably 70°C or lower, and still more preferably 65°C or lower.

[0045] In this specification, the melting point is a value measured using a differential scanning calorimeter (DSC), and specifically, is measured by the following method. [Method for measuring melting point using a differential scanning calorimeter] A sample is held at -10°C for 5 minutes in a nitrogen atmosphere, then heated to 190°C at 10°C / min and held at 190°C for 5 minutes. Next, the temperature is lowered to -10°C at 5°C / min and held at -10°C for 5 minutes. Thereafter, the sample is heated to 190°C at 10°C / min, and the peak observed in the obtained melting endothermic curve is taken as the melting point (Tm).

[0046] In the lubricating oil composition of one embodiment of the present invention, the content of component (B) is, based on the total amount (100 mass%) of the lubricating oil composition, 1.0 mass% or more, 1.5 mass% or more, 2.0 mass% or more, 2.5 mass% or more, 3.0 mass% or more, 4.0 mass% or more, 5.0 mass% or more, 10.0 mass% or more, 15.0 mass% or more, 20.0 mass% or more, 25.0 mass% or more, 30.0 mass% or more, 35.0 mass% or more, 40.0 mass% or more, 45.0 mass% or more, 50.0 mass% or more, 55.0 mass% or more, 60.0 mass% or more, 65.0 mass% or more, 70.0 mass% or more, 75.0 mass% or more, 80.0 mass% or more, 85.0 mass% or more, or 90.0 mass% or more. It may be more than 100% by mass, 99.9% by mass or less, 99.5% by mass or less, 99.0% by mass or less, 98.5% by mass or less, 98.0% by mass or less, 97.0% by mass or less, 96.0% by mass or less, 95.0% by mass or less, 90.0% by mass or less, 85.0% by mass or less, 80.0% by mass or less, 75.0% by mass The following may be 70.0 mass% or less, 65.0 mass% or less, 60.0 mass% or less, 55.0 mass% or less, 50.0 mass% or less, 45.0 mass% or less, 40.0 mass% or less, 35.0 mass% or less, 30.0 mass% or less, 25.0 mass% or less, 20.0 mass% or less, 15.0 mass% or less, or 10.0 mass% or less.

[0047] In the lubricating oil composition of one embodiment of the present invention, the content of component (B) is preferably adjusted depending on the type of component (B) so that the phase transition pressure falls within the above-mentioned range. For example, when component (B) contains a carboxylic acid or a carboxylic acid ester having a melting point of less than 30°C, the content of component (B) is, based on the total amount (100 mass%) of the lubricating oil composition, preferably more than 60.0 mass%, more preferably at least 65.0 mass%, more preferably at least 70.0 mass%, even more preferably at least 75.0 mass%, even more preferably at least 80.0 mass%, still more preferably at least 85.0 mass%, and particularly preferably at least 90.0 mass%. It may also be 92.0 mass% or more, 95.0 mass% or more, or 97.0 mass% or more, or may be less than 100 mass%, 99.9 mass% or less, 99.5 mass% or less, 99.0 mass% or less, 98.5 mass% or less, 98.0 mass% or less, 97.5 mass% or less, or 97.0 mass% or less. The melting point of the carboxylic acid or carboxylic acid ester having a melting point of less than 30°C may be 27°C or lower, 25°C or lower, or 23°C or lower, or may be 5°C or higher, 10°C or higher, 12°C or higher, or 15°C or higher.

[0048] When component (B) contains a carboxylic acid ester or carboxylic acid having a melting point of 30°C or higher, the content of component (B) is, based on the total amount (100 mass%) of the lubricating oil composition, preferably 20.0 mass% or more, more preferably 22.0 mass% or more, more preferably 25.0 mass% or more, even more preferably 27.0 mass% or more, still more preferably 30.0 mass% or more, still more preferably 32.0 mass% or more, and particularly preferably 35.0 mass% or more. The melting point of the carboxylic acid ester or carboxylic acid having a melting point of 30°C or higher may be 32°C or higher, 34°C or higher, or 36°C or higher, or may be 90°C or lower, 80°C or lower, 70°C or lower, 65°C or lower, 60°C or lower, 55°C or lower, 50°C or lower, or 43°C or lower.

[0049] When component (B) contains an alcohol or ether having a melting point of less than 30°C, the content of component (B) is, based on the total amount (100 mass%) of the lubricating oil composition, preferably more than 60.0 mass%, more preferably at least 65.0 mass%, more preferably at least 70.0 mass%, even more preferably at least 75.0 mass%, even more preferably at least 80.0 mass%, still more preferably at least 85.0 mass%, and particularly preferably at least 90.0 mass%. It may also be 92.0 mass% or more, 95.0 mass% or more, or 97.0 mass% or more, or may be less than 100 mass%, 99.9 mass% or less, 99.5 mass% or less, 99.0 mass% or less, 98.5 mass% or less, 98.0 mass% or less, 97.5 mass% or less, or 97.0 mass% or less. The melting point of the alcohol or ether having a melting point of less than 30°C may be 28°C or lower, 26°C or lower, or 25°C or lower, or may be 5°C or higher, 10°C or higher, 12°C or higher, 15°C or higher, 17°C or higher, or 20°C or higher.

[0050] When component (B) contains an alcohol or ether having a melting point of 30°C or higher but lower than 50°C, the content of component (B) is, based on the total amount (100% by mass) of the lubricating oil composition, preferably 5.0% by mass or higher, more preferably 8.0% by mass or higher, more preferably 10.0% by mass or higher, even more preferably 13.0% by mass or higher, still more preferably 15.0% by mass or higher, and particularly preferably 18.0% by mass or higher. It is also preferable that the content of component (B) is less than 100% by mass, 99.9% by mass or higher, based on the total amount (100% by mass) of the lubricating oil composition. %, 99.5% by mass or less, 99.0% by mass or less, 97.0% by mass or less, 95.0% by mass or less, 90.0% by mass or less, 85.0% by mass or less, 80.0% by mass or less, 75.0% by mass or less, 70.0% by mass or less, 65.0% by mass or less, 60.0% by mass or less, 55.0% by mass or less, 50.0% by mass or less, 45.0% by mass or less, 40.0% by mass or less, 35.0% by mass or less, 30.0% by mass or less, or 25.0% by mass or less. The melting point of the alcohol or ether having a melting point of 30°C or more but less than 50°C may be 32°C or more, 34°C or more, or 36°C or more, or may be 47°C or less, 45°C or less, 42°C or less, or 40°C or less.

[0051] When component (B) contains an alcohol or ether having a melting point of 50°C or higher, the content of component (B) is, based on the total amount (100 mass%) of the lubricating oil composition, preferably 1.0 mass% or more, more preferably 1.5 mass% or more, more preferably 2.0 mass% or more, even more preferably 2.2 mass% or more, still more preferably 2.5 mass% or more, and particularly preferably 2.7 mass% or more, and may also be 40.0 mass% or less, 35.0 mass% or less, 30.0 mass% or less, 25.0 mass% or less, 20.0 mass% or less, 15.0 mass% or less, 10.0 mass% or less, 8.0 mass% or less, 6.0 mass% or less, 5.0 mass% or less, or 4.0 mass% or less. The melting point of the alcohol or ether having a melting point of 50°C or higher may be 52°C or higher, 54°C or higher, 56°C or higher, or 58°C or higher, or may be 90°C or lower, 80°C or lower, 70°C or lower, 67°C or lower, 65°C or lower, 62°C or lower, or 60°C or lower.

[0052] <Other Lubricating Oil Additives> The lubricating oil composition of one embodiment of the present invention may further contain other lubricating oil additives other than those described above, as necessary, within the scope that does not impair the effects of the present invention. Such other lubricating oil additives are appropriately selected depending on the use of the lubricating oil composition, and examples thereof include viscosity index improvers, antioxidants, extreme pressure agents, metal detergents, ashless dispersants, metal deactivators, corrosion inhibitors, rust inhibitors, oiliness improvers, and antifoaming agents.

[0053] In the lubricating oil composition of one embodiment of the present invention, the content of lubricating oil additives other than component (B) may be less than 90 parts by mass, less than 80 parts by mass, less than 70 parts by mass, less than 60 parts by mass, less than 50 parts by mass, less than 40 parts by mass, less than 30 parts by mass, less than 20 parts by mass, less than 10 parts by mass, less than 5.0 parts by mass, less than 2.0 parts by mass, less than 1.0 part by mass, less than 0.1 parts by mass, less than 0.01 parts by mass, or less than 0.001 parts by mass, relative to 100 parts by mass of the total amount of component (B) contained in the lubricating oil composition.

[0054] <Pour Point Depressant> The lubricating oil composition of one embodiment of the present invention may contain a pour point depressant from the viewpoint of providing a lubricating oil composition with good low-temperature fluidity. Note that even when the lubricating oil composition of one embodiment of the present invention contains a pour point depressant, it can maintain good lubricity.

[0055] Examples of pour point depressants used in one embodiment of the present invention include ethylene-vinyl acetate copolymers, condensates of chlorinated paraffins and naphthalene, condensates of chlorinated paraffins and phenols, polymethacrylates, polyalkylstyrenes, etc. These pour point depressants may be used alone or in combination of two or more. Among these, it is preferable that the pour point depressant contains one or more selected from ethylene-vinyl acetate copolymers and polymethacrylates. The weight average molecular weight (Mw) of the pour point depressant may be 5,000 or more, 7,000 or more, 10,000 or more, 15,000 or more, 20,000 or more, 25,000 or more, 30,000 or more, 35,000 or more, 40,000 or more, 45,000 or more, 50,000 or more, 55,000 or more, or 60,000 or more, and may be 150,000 or less, 120,000 or less, 100,000 or less, 90,000 or less, or 80,000 or less. The molecular weight distribution (Mw / Mn) of the pour point depressant may be 10 or less, 8.0 or less, 7.0 or less, 6.0 or less, 5.0 or less, 4.0 or less, 3.5 or less, 3.0 or less, or 2.6 or less, or may be 1.01 or more, 1.05 or more, or 1.1 or more.

[0056] In the lubricating oil composition of one embodiment of the present invention, from the viewpoint of providing a lubricating oil composition that has good low-temperature fluidity and can maintain good lubricity, the content of the pour point depressant is preferably 0.001 to 7.0 mass%, more preferably 0.01 to 5.0 mass%, even more preferably 0.1 to 3.0 mass%, and still more preferably 0.3 to 2.0 mass%, based on the total amount (100 mass%) of the lubricating oil composition, and may also be less than 1.7 mass%, less than 1.5 mass%, less than 1.2 mass%, less than 1.0 mass%, less than 0.5 mass%, less than 0.1 mass%, less than 0.01 mass%, less than 0.001 mass%, or less than 0.0001 mass%.

[0057] <Viscosity Index Improver> Examples of viscosity index improvers used in one embodiment of the present invention include polymers such as non-dispersant polymethacrylate, dispersant polymethacrylate, olefin copolymers (e.g., ethylene-propylene copolymers, etc.), dispersant olefin copolymers, and styrene copolymers (e.g., styrene-diene copolymers, styrene-isoprene copolymers, etc.). These viscosity index improvers may be used alone or in combination of two or more. The weight average molecular weight (Mw) of the viscosity index improver used in one embodiment of the present invention may be 5,000 or more, 7,000 or more, 10,000 or more, 15,000 or more, or 20,000 or more, or may be 1,000,000 or less, 700,000 or less, 500,000 or less, 300,000 or less, 200,000 or less, 100,000 or less, or 50,000 or less. In the lubricating oil composition of one embodiment of the present invention, the content of the viscosity index improver may be less than 7.0 mass%, less than 5.0 mass%, less than 2.0 mass%, less than 1.0 mass%, less than 0.5 mass%, less than 0.1 mass%, less than 0.01 mass%, less than 0.001 mass%, or less than 0.0001 mass%, based on the total amount (100 mass%) of the lubricating oil composition.

[0058] <Antioxidant> Examples of antioxidants used in one embodiment of the present invention include amine-based antioxidants such as alkylated diphenylamine, phenylnaphthylamine, and alkylated phenylnaphthylamine; and phenol-based antioxidants such as 2,6-di-t-butylphenol, 4,4'-methylenebis(2,6-di-t-butylphenol), isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate. These antioxidants may be used alone or in combination of two or more. In the lubricating oil composition of one embodiment of the present invention, it is preferable to use an amine-based antioxidant and a phenol-based antioxidant in combination. In the lubricating oil composition of one embodiment of the present invention, the content of the antioxidant may be less than 7.0 mass%, less than 5.0 mass%, less than 2.0 mass%, less than 1.0 mass%, less than 0.5 mass%, less than 0.1 mass%, less than 0.01 mass%, less than 0.001 mass%, or less than 0.0001 mass%, based on the total amount (100 mass%) of the lubricating oil composition.

[0059] <Extreme Pressure Agent> Examples of the extreme pressure agent (antiwear agent) used in one embodiment of the present invention include sulfur-based extreme pressure agents such as sulfurized olefin, polysulfide, sulfurized ester, thiazole, thiadiazole, zinc dithiophosphate, molybdenum dithiophosphate, molybdenum dithiocarbamate, and powdered sulfur; phosphorus-based extreme pressure agents such as phosphate esters (tricresyl phosphate, trioleyl phosphate, etc.), acidic phosphate esters (monooleyl acid phosphate, dioleyl acid phosphate, etc.), acidic phosphate amine salts (oleylamine salt of monooleyl acid phosphate, etc.), and phosphite esters (dioleyl acid phosphite, tridecyl phosphite, trisnonylphenyl sulfite, etc.); and fats and oils (beef tallow, lard, soybean oil, rapeseed oil, rice bran oil, coconut oil, palm oil, etc.).

[0060] The lubricating oil composition of one embodiment of the present invention solidifies to form a strong oil film at an early stage when the pressure is 70 MPa or less during a pressure increase process in which pressure is gradually applied, thereby enabling good lubricity to be achieved early, and therefore does not need to contain an extreme pressure agent such as a sulfur-based extreme pressure agent or a phosphorus-based extreme pressure agent. Therefore, in the lubricating oil composition of one embodiment of the present invention, the content of the extreme pressure agent may be less than 50 parts by mass, less than 40 parts by mass, less than 30 parts by mass, less than 20 parts by mass, less than 15 parts by mass, less than 10 parts by mass, less than 5.0 parts by mass, less than 2.0 parts by mass, less than 1.0 parts by mass, less than 0.1 parts by mass, less than 0.01 parts by mass, or less than 0.001 parts by mass, relative to 100 parts by mass of the total amount of component (B) contained in the lubricating oil composition. In the lubricating oil composition of one embodiment of the present invention, the content of the extreme pressure agent may be less than 7.0 mass%, less than 5.0 mass%, less than 2.0 mass%, less than 1.0 mass%, less than 0.5 mass%, less than 0.1 mass%, less than 0.01 mass%, less than 0.001 mass%, or less than 0.0001 mass%, based on the total amount (100 mass%) of the lubricating oil composition.

[0061] In the lubricating oil composition of one embodiment of the present invention, the content of the sulfur-based extreme pressure agent may be less than 50 parts by mass, less than 40 parts by mass, less than 30 parts by mass, less than 20 parts by mass, less than 15 parts by mass, less than 10 parts by mass, less than 5.0 parts by mass, less than 2.0 parts by mass, less than 1.0 parts by mass, less than 0.1 parts by mass, less than 0.01 parts by mass, or less than 0.001 parts by mass, based on the total amount (100% by mass) of the lubricating oil composition.

[0062] In the lubricating oil composition of one embodiment of the present invention, the content of the phosphorus-based extreme pressure agent may be less than 50 parts by mass, less than 40 parts by mass, less than 30 parts by mass, less than 20 parts by mass, less than 15 parts by mass, less than 10 parts by mass, less than 5.0 parts by mass, less than 2.0 parts by mass, less than 1.0 parts by mass, less than 0.1 parts by mass, less than 0.01 parts by mass, or less than 0.001 parts by mass, based on the total amount (100 parts by mass) of the lubricating oil composition.

[0063] <Metallic Detergent> Examples of metallic detergents used in one embodiment of the present invention include metal salts such as metal sulfonates, metal salicylates, and metal phenates. The metal atoms constituting the metal salts are preferably metal atoms selected from alkali metals and alkaline earth metals, more preferably sodium, calcium, magnesium, or barium, and even more preferably calcium. These metallic detergents may be used alone or in combination of two or more.

[0064] The base number of the metallic detergent is preferably 0 to 600 mgKOH / g. However, in the lubricating oil composition of one embodiment of the present invention, the metallic detergent is preferably an overbased metallic detergent having a base number of 100 mgKOH / g or more. The base number of the overbased metallic detergent is 100 mgKOH / g or more, preferably 150 to 500 mgKOH / g, and more preferably 200 to 450 mgKOH / g. In this specification, "base number" refers to the base number measured by the perchloric acid method in accordance with JIS K2501:2003 "Petroleum products and lubricants - Neutralization number test method".

[0065] In the lubricating oil composition of one embodiment of the present invention, the content of the metallic detergent may be less than 10.0 mass%, less than 7.0 mass%, less than 5.0 mass%, less than 2.0 mass%, less than 1.0 mass%, less than 0.5 mass%, less than 0.1 mass%, less than 0.01 mass%, less than 0.001 mass%, or less than 0.0001 mass%, based on the total amount (100 mass%) of the lubricating oil composition.

[0066] <Ashless Dispersant> Examples of the ashless dispersant used in one embodiment of the present invention include boron-free succinimides such as boron-free alkenyl succinimides, boron-containing succinimides such as boron-containing alkenyl succinimides, benzylamines, boron-containing benzylamines, succinic acid esters, fatty acids, and mono- or di-carboxylic acid amides represented by succinic acid, etc. These ashless dispersants may be used alone or in combination of two or more. In the lubricating oil composition of one embodiment of the present invention, the content of the ashless dispersant may be less than 15.0 mass%, less than 12.0 mass%, less than 10.0 mass%, less than 7.0 mass%, less than 5.0 mass%, less than 2.0 mass%, less than 1.0 mass%, less than 0.5 mass%, less than 0.1 mass%, less than 0.01 mass%, less than 0.001 mass%, or less than 0.0001 mass%, based on the total amount (100 mass%) of the lubricating oil composition.

[0067] <Metal Deactivator> Examples of metal deactivators used in one embodiment of the present invention include benzothiazole compounds, benzotriazole-based compounds, tolyltriazole-based compounds, imidazole-based compounds, thiadiazole-based compounds, and pyrimidine-based compounds. These metal deactivators may be used alone or in combination of two or more. In the lubricating oil composition of one embodiment of the present invention, the content of the metal deactivator may be less than 7.0 mass%, less than 5.0 mass%, less than 2.0 mass%, less than 1.0 mass%, less than 0.5 mass%, less than 0.1 mass%, less than 0.01 mass%, less than 0.001 mass%, or less than 0.0001 mass%, based on the total amount (100 mass%) of the lubricating oil composition.

[0068] <Corrosion inhibitor> Examples of corrosion inhibitors used in one embodiment of the present invention include amine compounds, alkanolamine compounds, amide compounds, and carboxylic acid compounds. These corrosion inhibitors may be used alone or in combination of two or more. In the lubricating oil composition of one embodiment of the present invention, the content of the corrosion inhibitor may be less than 7.0 mass%, less than 5.0 mass%, less than 2.0 mass%, less than 1.0 mass%, less than 0.5 mass%, less than 0.1 mass%, less than 0.01 mass%, less than 0.001 mass%, or less than 0.0001 mass%, based on the total amount (100 mass%) of the lubricating oil composition.

[0069] <Rust inhibitor> Examples of rust inhibitors used in one embodiment of the present invention include fatty acids, alkenyl succinic acid half esters, fatty acid soaps, alkyl sulfonates, polyhydric alcohol fatty acid esters, fatty acid amines, oxidized paraffins, and alkyl polyoxyethylene ethers. These rust inhibitors may be used alone or in combination of two or more. In the lubricating oil composition of one embodiment of the present invention, the content of the rust inhibitor may be less than 7.0 mass%, less than 5.0 mass%, less than 2.0 mass%, less than 1.0 mass%, less than 0.5 mass%, less than 0.1 mass%, less than 0.01 mass%, less than 0.001 mass%, or less than 0.0001 mass%, based on the total amount (100 mass%) of the lubricating oil composition.

[0070] <Oilability Improver> Examples of oiliness improvers used in one embodiment of the present invention include polymers of polymerized fatty acids such as dimer acid and hydrogenated dimer acid; saturated or unsaturated aliphatic monoalcohols such as lauryl alcohol and oleyl alcohol; saturated or unsaturated aliphatic monoamines such as stearylamine and oleylamine; saturated or unsaturated aliphatic monocarboxylic acid amides such as lauric acid amide and oleic acid amide; and the like. These oiliness improvers may be used alone or in combination of two or more. In the lubricating oil composition of one embodiment of the present invention, the content of the oiliness improver may be less than 7.0 mass%, less than 5.0 mass%, less than 2.0 mass%, less than 1.0 mass%, less than 0.5 mass%, less than 0.1 mass%, less than 0.01 mass%, less than 0.001 mass%, or less than 0.0001 mass%, based on the total amount (100 mass%) of the lubricating oil composition.

[0071] <Degreaser> Examples of degreasers used in one embodiment of the present invention include alkenyl sulfosuccinic acid. These degreasers may be used alone or in combination of two or more. In the lubricating oil composition of one embodiment of the present invention, the content of the degreaser may be less than 7.0 mass%, less than 5.0 mass%, less than 2.0 mass%, less than 1.0 mass%, less than 0.5 mass%, less than 0.1 mass%, less than 0.01 mass%, less than 0.001 mass%, or less than 0.0001 mass%, based on the total amount (100 mass%) of the lubricating oil composition.

[0072] <Antifoaming agent> Examples of antifoaming agents used in one embodiment of the present invention include silicone oil, fluorosilicone oil, and fluoroalkyl ether. These antifoaming agents may be used alone or in combination of two or more. In the lubricating oil composition of one embodiment of the present invention, the content of the antifoaming agent may be less than 7.0 mass%, less than 5.0 mass%, less than 2.0 mass%, less than 1.0 mass%, less than 0.5 mass%, less than 0.1 mass%, less than 0.01 mass%, less than 0.001 mass%, or less than 0.0001 mass%, based on the total amount (100 mass%) of the lubricating oil composition.

[0073] [Lubricating Oil] One aspect of the present invention may be a lubricating oil essentially composed of a compound (B) selected from carboxylic acid esters, carboxylic acids, alcohols, and ethers, and having a phase transition pressure of 70 MPa or less, calculated by the above-described procedures (i) to (iv). Component (B) constituting the lubricating oil of one aspect of the present invention may be the same as component (B) contained in the lubricating oil composition of one aspect of the present invention described above, and preferred aspects are also as described above. The lubricating oil of one aspect of the present invention is distinguished from the lubricating oil composition of one aspect of the present invention described above, which essentially contains a base oil (A) and lubricating oil additives other than component (B).

[0074] In this specification, the phrase "consisting essentially of compound (B)" excludes embodiments in which components other than component (B) are contained for a specific purpose, but does not exclude embodiments in which components other than component (B) are inevitably contained as impurities. However, even taking into account embodiments in which components other than component (B) are inevitably contained as impurities, it is preferable that the amount of components other than component (B) be as small as possible.

[0075] In the lubricating oil of one embodiment of the present invention, the content of components other than component (B) is, based on the total amount (100% by mass) of the lubricating oil, preferably less than 1.0% by mass, more preferably less than 0.1% by mass, more preferably less than 0.01% by mass, even more preferably less than 0.001% by mass, still more preferably less than 0.0001% by mass, and particularly preferably less than 0.00001% by mass.

[0076] [Uses of Lubricating Oil Composition and Lubricating Oil] The lubricating oil composition and lubricating oil of one embodiment of the present invention have the property that a phase transition occurs at a relatively early stage in an environment accompanied by an increase in surface pressure, a strong oil film is formed, and good lubricity can be exhibited, and therefore the composition and lubricating oil can be used in a variety of applications.

[0077] For example, the lubricating oil composition or lubricating oil of one embodiment of the present invention can be used as a metalworking fluid in metalworking. For example, in cold forging, seizure on metal materials can be suppressed, and in deep drawing, the formation of a strong oil film can suppress cracks in the processed product, thereby achieving excellent workability. Specific metalworking includes, for example, plastic working of the above-mentioned metal materials, such as press working, forging, extrusion, rolling, deep drawing, drawing, ironing, bending, rolling, and cold forging. Furthermore, the metal materials processed using the lubricating oil composition or lubricating oil of one embodiment of the present invention are not particularly limited, and examples thereof include iron alloys such as steel, stainless steel, alloy steel, and surface-treated steel, and non-ferrous alloys such as aluminum alloys, copper, titanium, titanium alloys, nickel-based alloys, niobium alloys, tantalum alloys, molybdenum alloys, and tungsten alloys.

[0078] When a deep drawing test is carried out using the lubricating oil composition or lubricating oil according to one embodiment of the present invention in accordance with the method described in the Examples below, the maximum blank holding load is preferably 100 kN or more, more preferably 120 kN or more, more preferably 140 kN or more, even more preferably 150 kN or more, still more preferably 170 kN or more, and particularly preferably 200 kN or more.

[0079] In addition to plastic working, the lubricating oil composition of one embodiment of the present invention can also be used as a metal working oil in cutting work, and can also be used in other applications besides metal working oils, such as bearing oils, internal combustion engine oils, ATF oils, gear oils, hydraulic oils, and greases.

[0080] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. The methods for measuring various physical properties are as follows.

[0081] (1) Kinematic viscosity and viscosity index: Measured and calculated in accordance with JIS K2283:2000. (2) Weight-average molecular weight (Mw), number-average molecular weight (Mn): Measured using a gel permeation chromatograph (Agilent, "1260 HPLC") under the following conditions, and values ​​measured in terms of standard polystyrene were used. (Measurement conditions) Column: Two "Shodex LF404" columns connected in series. Column temperature: 35°C. Developing solvent: chloroform. Flow rate: 0.3 mL / min.

[0082] (3) Phase Transition Pressure Using a high-pressure measuring tester as shown in FIG. 1, the "phase transition pressure" of the lubricating oil composition or sample oil to be measured at 30°C was calculated by carrying out the above-mentioned procedures (i) to (iv). Specifically, in procedure (i), 2 mL of the sample oil to be measured at 30°C was filled into the cylindrical cell 14 (cell inner diameter: 12.0 mm) of the high-pressure measuring tester 1. Next, in procedure (ii), a load was applied vertically via the plunger 13 to the sample oil in the cell 14 using a compression-tensile tester (manufactured by Instron, product name "55RF1186 Model Tester") (not shown) at a speed of 0.01 mm / s. Note that the load on the plunger 13 includes resistance due to the sealing material of the plunger 13 and the pressure vessel. Therefore, the pressure calculated from the load / cross-sectional area was multiplied by 0.964 to take this resistance into account. This value, i.e., the value calculated from "load / cross-sectional area x 0.964," was used as the pressure P (MPa) in the cell 14. A correlation graph was then obtained, with the pressure P (MPa) in the cell on the horizontal axis and the plunger's vertical depression length Y (mm) on the vertical axis. Then, in operation (iii) and operation (iv), the slope [ΔX / ΔY] of the tangent line and the rate of change (%) of the slope [ΔX / ΔY] of the tangent line at the point where the pressure P in the cell became n (MPa) (n is an integer equal to or greater than 1) were calculated from the correlation graph obtained in operation (ii) based on the above-described procedure. The phase transition pressure was then determined as n (MPa), which is the pressure P in the cell when the rate of change first exceeded 2%. When the pressure P in the cell was increased to 100 MPa, the test oils for which the rate of change did not exceed 2% were judged to be "not undergoing phase transition," and the measurement of the phase transition pressure was terminated.

[0083] Examples 1 to 11 and Comparative Examples 1 to 10 Lubricating oil compositions or lubricating oils were prepared by blending components selected from the base oils, various additives, and pour point depressants shown below in the amounts shown in Tables 1 and 2. [Base oil] Paraffinic mineral oil: kinematic viscosity at 40°C = 8.11 mm ２ / s, paraffinic mineral oil with a viscosity index of 83. Naphthenic mineral oil: kinematic viscosity at 40°C = 9.11 mm ２ / s, and a naphthenic mineral oil having a viscosity index of 26. [Various Compounds] Butyl stearate: a compound represented by the general formula (b-1) above, １= C17 alkyl group, R ａ = n-butyl group, melting point = 17 to 22°C. Methyl stearate: a compound where R in the general formula (b-1) is １ = C17 alkyl group, R ａ = methyl group, melting point = 37 to 41°C. Lauryl alcohol: R in the general formula (b-3) ３ = C12 alkyl group, melting point = 23.5°C. Myristyl alcohol: a compound in which R ３ = C14 alkyl group, melting point = 38°C. Stearyl alcohol: a compound in which R in the general formula (b-3) ３ = C18 alkyl group, melting point = 59.4 to 59.8°C. Methyl oleate: a compound in which R １ = oleyl group, R ａ = Compound having a methyl group, melting point = -19.9°C. [Pour point depressant] Polymethacrylate (polymethacrylate having Mw = 69,000, Mn = 28,000, Mw / Mn = 2.46)

[0084] The phase transition pressures of the prepared lubricating oil compositions or lubricating oils were measured using the method described above, and the following deep drawing test was also performed. The results are shown in Tables 1 and 2. Figure 2 shows a correlation graph between the pressure P in the cell and the plunger depression length Y obtained through procedures (i) to (iv) for the sample oil of Example 1, as well as a graph of the rate of change of the tangent slope [ΔX / ΔY] with respect to the pressure P in the cell. As shown in the rate of change graph in Figure 2, when the pressure P in the cell was increased by 1 MPa increments, the pressure in the cell was "26 MPa" when the rate of change of the tangent slope [ΔX / ΔY] exceeded 2% for the first time, and this value was designated the "phase transition pressure." Note that the same correlation graph and rate of change graph as in Figure 2 were obtained for the sample oils of Examples 2 to 11, and the phase transition pressures were calculated in the same manner.

[0085] [Deep Drawing Test] A deep drawing test was carried out using a deep drawing tester (manufactured by Tokyo Koki Testing Instruments Co., Ltd., product name "Automatic Universal Deep Drawing Tester USM-350D"). A workpiece was prepared by generously applying the prepared lubricating oil composition or lubricating oil to both sides of a disk-shaped cold-rolled steel sheet SPCC-SD (diameter 100 mm, thickness 0.8 mm). A deep drawing test was carried out using a punch (material: SKD11, R=10, diameter=50 mm) and a die (material: SKD11, R=10, diameter=52 mm) at room temperature (25°C) with blank holder loads set to 30 kN, 40 kN, 50 kN, 60 kN... and increasing in 10 kN increments up to 200 kN. In the deep drawing test at each blank holder load, for example, blank holder load X (kN) If cracks occurred in the processed product, the load measured immediately before, "X-10 (kN)", was taken as the "maximum blank holding load", and the test was terminated without further testing. If no cracks occurred in the processed product even when the blank holding load was set to 200 kN, the "maximum blank holding load" was taken as "200 kN". The higher the value of the maximum blank holding load, the more excellent the processability of the prepared lubricating oil composition or lubricating oil. Note that if the maximum blank holding load was 100 kN or more, the lubricating oil composition or lubricating oil to be measured was determined to have excellent processability.

[0086]

[0087]

[0088] As can be seen from Table 1, the lubricating oil compositions or lubricating oils prepared in Examples 1 to 11 had a maximum blank holding load of 100 kN or more, resulting in excellent processability. On the other hand, the lubricating oil compositions or lubricating oils prepared in Comparative Examples 1 to 10 had a maximum blank holding load of less than 100 kN, resulting in poor processability.

[0089] REFERENCE SIGNS LIST 1 High pressure measurement tester 11 Pressure vessel outer cylinder 12 Pressure vessel inner cylinder 13 Plunger 14 Cell 15 Holding stand

Claims

1. A lubricating oil composition comprising a base oil (A) and a compound (B) selected from a carboxylic acid ester, a carboxylic acid, an alcohol, and an ether, wherein the phase transition pressure calculated by the following procedures (i) to (iv) is 70 MPa or less. Step (i): The lubricating oil composition at 30° C. is filled into a cylindrical cell having a constant cross-sectional area. - Operation (ii): After operation (i), a load is applied to the lubricating oil composition in the cell in the vertical direction via a plunger, and the lubricating oil composition is pushed in at a speed of 0.01 mm / s. A correlation graph is obtained between the pressure P in the cell and the plunger pushing length Y, with the pressure P (MPa) in the cell calculated from the load / cross-sectional area as the horizontal axis and the plunger pushing length Y (mm) in the vertical direction as the vertical axis. Procedure (iii): In the correlation graph obtained in procedure (ii), the slopes [ΔX / ΔY] of the tangents at the points where the pressure P in the cell becomes n (MPa) (n is an integer of 1 or more) are calculated for each increment of the pressure P in the cell from 0 MPa to 1 MPa. Operation (iv): When the pressure P in the cell changes from n-1 (MPa) to n (MPa), the rate of change in the slope of the tangent line [ΔX / ΔY] calculated from the following formula (1) exceeds 2% for the first time; n (MPa) is defined as the phase transition pressure. Equation (1): Rate of change (%) of tangent slope [ΔX / ΔY] = ([ΔX / ΔY] ｎ −[ΔX / ΔY] ｎ－１ ) / 1(MPa)×100 (In the above formula (1), [ΔX / ΔY] ｎ indicates the slope [ΔX / ΔY] of the tangent at the point where the pressure P in the cell is n (MPa) in the correlation graph. [ΔX / ΔY] ｎ－１ indicates the slope [ΔX / ΔY] of the tangent line at the point where the pressure P in the cell is n-1 (MPa) in the correlation graph.

2. 2. The lubricating oil composition of claim 1, wherein component (A) comprises a paraffinic mineral oil (A1).

3. 3. The lubricating oil composition according to claim 1, wherein the total content of component (A) and component (B) is 70 to 100 mass % based on the total amount of the lubricating oil composition.

4. 3. The lubricating oil composition according to claim 1, wherein the total content of lubricating oil additives other than component (B) is less than 90 parts by mass per 100 parts by mass of the total amount of component (B).

5. 3. The lubricating oil composition according to claim 1, wherein the content of the sulfur-based extreme pressure agent is less than 50 parts by mass per 100 parts by mass of the total amount of component (B).

6. the carboxylic acid ester is a saturated or unsaturated chain carboxylic acid ester, the carboxylic acid is a saturated or unsaturated chain carboxylic acid, the alcohol is a saturated or unsaturated chain alcohol, The ether is a saturated or unsaturated chain ether. The lubricating oil composition according to claim 1 or 2.

7. the carboxylic acid ester is a saturated chain carboxylic acid ester, the carboxylic acid is a saturated chain carboxylic acid, the alcohol is a saturated chain alcohol, The ether is a saturated chain ether. The lubricating oil composition according to claim 1 or 2.

8. 3. The lubricating oil composition according to claim 1, wherein component (B) comprises a compound represented by any one of the following general formulas (b-1) to (b-4): 【Chemical 1】 (In the above formula, R １ , R ２ and R ３ are each independently an alkyl group having 10 to 40 carbon atoms. ａ , R ｂ and R ｃ are each independently an alkyl group having 1 to 30 carbon atoms. ｂ and R ｃ The total number of carbon atoms is 10 or more.

9. 3. The lubricating oil composition according to claim 1, wherein the content of component (B) is 1.0 mass % or more based on the total amount of the lubricating oil composition.

10. The kinematic viscosity of the lubricating oil composition at 40°C is 100 mm ２ 3. The lubricating oil composition according to claim 1, wherein the viscosity of the lubricating oil composition is 1 / s or less.

11. 3. The lubricating oil composition of claim 1 or 2, further comprising a pour point depressant.

12. The lubricating oil composition according to claim 1 or 2, which is used in metal working.

13. A lubricating oil essentially consisting of a compound (B) selected from a carboxylic acid ester, a carboxylic acid, an alcohol, and an ether, and having a phase transition pressure of 70 MPa or less as calculated by the following procedures (i) to (iv): Step (i): The lubricating oil composition at 30° C. is filled into a cylindrical cell having a constant cross-sectional area. - Operation (ii): After operation (i), a load is applied to the lubricating oil composition in the cell in the vertical direction via a plunger, and the lubricating oil composition is pushed in at a speed of 0.01 mm / s. A correlation graph is obtained between the pressure P in the cell and the plunger pushing length Y, with the pressure P (MPa) in the cell calculated from the load / cross-sectional area as the horizontal axis and the plunger pushing length Y (mm) in the vertical direction as the vertical axis. Procedure (iii): In the correlation graph obtained in procedure (ii), the slopes [ΔX / ΔY] of the tangents at the points where the pressure P in the cell becomes n (MPa) (n is an integer of 1 or more) are calculated for each increment of the pressure P in the cell from 0 MPa to 1 MPa. Operation (iv): When the pressure P in the cell changes from n-1 (MPa) to n (MPa), the rate of change in the slope of the tangent line [ΔX / ΔY] calculated from the following formula (1) exceeds 2% for the first time; n (MPa) is defined as the phase transition pressure. Equation (1): Rate of change (%) of tangent slope [ΔX / ΔY] = ([ΔX / ΔY] ｎ −[ΔX / ΔY] ｎ－１ ) / 1(MPa)×100 (In the above formula (1), [ΔX / ΔY] ｎ indicates the slope [ΔX / ΔY] of the tangent at the point where the pressure P in the cell is n (MPa) in the correlation graph. [ΔX / ΔY] ｎ－１ indicates the slope [ΔX / ΔY] of the tangent line at the point where the pressure P in the cell is n-1 (MPa) in the correlation graph.

14. 14. The lubricating oil according to claim 13, wherein the content of components other than component (B) is less than 1.0 mass % based on the total amount of the lubricating oil.

15. The lubricating oil according to claim 13 or 14, which is used in metalworking.

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