Lubricating oil composition

Abstract

The present invention provides a lubricating oil composition that is used for the lubrication of a shock absorber and contains: a base oil (A); one or more basic compounds (B) selected from an amide compound (B1) and an imide compound (B2); and a phosphorous acid ester (C) having an alkenyl group or an alkyl group having 11 or more carbon atoms, wherein the content of the component (C) is 0.01 to 1.90 mass% in terms of the total content of the lubricating oil composition, and the base value of the lubricating oil composition is 0.05 to 1.30 mg KOH / g.

Description

lubricating oil composition

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

[0002] Shock absorbers are mechanisms mounted on a vehicle body that are filled with a shock absorber lubricant composition and are intended to generate a damping force to reduce vibrations of the vehicle body. At the same time, they are required to optimize the friction characteristics of the sliding parts to control the ride comfort of the vehicle body, and to suppress frictional wear of the sliding parts to ensure durability.

[0003] Various lubricating oil compositions for shock absorbers have been developed that are suitable for use in such shock absorbers. For example, Patent Document 1 discloses a novel lubricating oil composition that is better suited for the lubrication of shock absorbers, which contains a base oil, a predetermined zinc dithiophosphate, calcium sulfonate, and a seal sweller.

[0004] Japanese Patent Publication No. 2022-022721

[0005] Under these circumstances, there is a need for novel lubricating oil compositions for shock absorbers that improve various performance characteristics required for shock absorber lubrication (e.g., frictional properties with respect to rubber and resistance to immersion).

[0006] One aspect of the present invention provides a lubricating oil composition containing a base oil, a predetermined basic compound, and a predetermined phosphite ester, with the base number adjusted to a predetermined range. Specifically, one aspect of the present invention provides the following invention: [1] A lubricating oil composition comprising a base oil (A), one or more basic compounds (B) selected from amide compounds (B1) and imide compounds (B2), and a phosphite ester (C) having an alkyl group or alkenyl group having 11 or more carbon atoms, wherein the content of component (C) is 0.01 to 1.90% by mass on a basis of the total amount of the lubricating oil composition, the base number of the lubricating oil composition is 0.05 to 1.30 mgKOH / g, and the lubricating oil composition is used for lubricating buffers. [2] The lubricating oil composition according to [1] above, wherein the content ratio of component (B) to component (C) [(B) / (C)] is 0.20 to 3.50 by mass. [3] The lubricating oil composition according to [1] or [2] above, wherein the content of component (B) is 0.01 to 4.00% by mass on a basis of the total amount of the lubricating oil composition. [4] The lubricating oil composition according to any one of [1] to [3] above, wherein component (B1) is an amide compound (B11) having a hydrocarbon group containing at least one imino structure. [5] The lubricating oil composition according to any one of [1] to [4] above, wherein component (B2) comprises one or more non-boron alkenyl succinimides (B21) selected from non-boron modified alkenyl succinimides and non-boron modified alkenyl succinimides, and one or more boron modified products (B22) of component (B21). [6] The lubricating oil composition according to any one of the above [1] to [5], wherein the content of acidic phosphate esters and their amine salts is less than 0.10% by mass on a total basis of the lubricating oil composition. [7] The lubricating oil composition according to any one of the above [1] to [6], wherein the content of phosphorous acid esters (CX) that do not have an alkyl group or alkenyl group having 11 or more carbon atoms is less than 0.10% by mass on a total basis of the lubricating oil composition. [8] The lubricating oil composition according to any one of the above [1] to [7], wherein the content of molybdenum compounds on a molybdenum atom basis is less than 50 ppm by mass on a total basis of the lubricating oil composition.[9] The lubricating oil composition according to any one of the above items [1] to [8], wherein the content of the zinc-based compound in terms of zinc atoms is less than 50 ppm by mass on a total basis of the lubricating oil composition.

[10] The lubricating oil composition according to any one of the above items [1] to [9], wherein the content of the sulfur-based compound in terms of sulfur atoms is less than 400 ppm by mass on a total basis of the lubricating oil composition.

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

[10] , wherein the content of the metal-based detergent containing a metal atom selected from calcium atoms, magnesium atoms, and sodium atoms in terms of the metal atom is less than 100 ppm by mass on a total basis of the lubricating oil composition.

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

[11] , which substantially does not contain a primary amine.

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

[12] , which substantially does not contain a diamine.

[14] A lubricating oil composition according to any one of [1] to

[13] above, which substantially does not contain an N-substituted derivative of sarcosine.

[15] A lubricating oil composition according to any one of [1] to

[14] above, which substantially does not contain a fluorescent agent.

[16] A lubricating oil composition according to any one of [1] to

[15] above, which substantially does not contain a fatty acid polyester of a fatty acid and a polyhydric alcohol.

[17] A method for lubricating a buffer, wherein the lubricating oil composition according to any one of [1] to

[16] above is used for lubricating the buffer.

[0007] A preferred embodiment of the present invention is a lubricating oil composition having various properties required for the lubrication of shock absorbers, and a more specific embodiment of the lubricating oil composition can improve frictional properties and immersion resistance to rubber in a well-balanced manner. Furthermore, in addition to these properties, a more preferred embodiment of the lubricating oil composition can also reduce the coefficient of friction between metals and improve wear resistance.

[0008] The numerical ranges described herein can be any combination of upper and lower limits. For example, if the numerical range is described as "preferably 30 to 100, more preferably 40 to 80," the ranges of "30 to 80" and "40 to 100" are also included in the numerical range described herein. Similarly, if the numerical range is described as "preferably 30 or more, more preferably 40 or more, and also preferably 100 or less, more preferably 80 or less," the ranges of "30 to 80" and "40 to 100" are also included in the numerical range described herein. In addition, for example, if the numerical range described herein is described as "60 to 100," it means the range is "60 or more (60 or greater than 60), and 100 or less (100 or less than 100)." Furthermore, in the provisions for upper and lower limits described herein, the numerical range from the lower limit to the upper limit can be defined by appropriately selecting and combining the options from each set of choices.

[0009] Furthermore, in this specification, kinematic viscosity and viscosity index refer to values ​​measured or calculated in accordance with JIS K2283:2000. The content of phosphorus atoms (P), molybdenum atoms (Mo), zinc atoms (Zn), calcium atoms (Ca), magnesium atoms (Mg), and sodium atoms (Na) refer to values ​​measured in accordance with JPI-5S-38-92. The content of nitrogen atoms (N) refers to values ​​measured in accordance with JIS K2609:1998. The content of sulfur atoms (S) refers to values ​​measured in accordance with JIS K2541-6:2013. The base number refers to values ​​measured in accordance with JIS K2501:2003 (perchloric acid method).

[0010] In this specification, "substantially does not contain" a particular compound, meaning that the compound is added with a specific intention, but not that the compound is inevitably included in the product.

[0011] [Composition of Lubricating Oil Composition] A lubricating oil composition according to one aspect of the present invention contains a base oil (A) (hereinafter also referred to as "component (A)"), one or more basic compounds (B) selected from amide compounds (B1) (hereinafter also referred to as "component (B1)") and imide compounds (B2) (hereinafter also referred to as "component (B2)"), and a phosphorous acid ester (C) (hereinafter also referred to as "component (C)") having an alkyl group or alkenyl group with 11 or more carbon atoms.

[0012] A lubricating oil composition according to one aspect of the present invention contains the above-mentioned components (B) and (C), and by adjusting the content of component (C) and the base number of the lubricating oil composition to be within a predetermined range, various performances required for the lubrication of a shock absorber can be improved. More specifically, the frictional properties, wear resistance, and immersion resistance to rubber can be improved in a well-balanced manner. In particular, component (B) contributes to improving the immersion resistance of the lubricating oil composition to rubber, and component (C) reduces the coefficient of friction μ between rubber and metal, thereby contributing to improving the frictional properties of the lubricating oil composition to rubber. Therefore, when the lubricating oil composition according to one aspect of the present invention is used to lubricate a shock absorber, the rubber oil seal of the shock absorber effectively suppresses the immersion of the lubricating oil composition, and reduces the coefficient of friction between the iron or chromium rod of the shock absorber and the rubber oil seal, thereby improving the ride comfort of a vehicle equipped with the shock absorber.

[0013] A lubricating oil composition according to one aspect of the present invention may further contain lubricating oil additives other than components (B) to (C) as needed, to the extent that the effects of the present invention are not impaired. In a lubricating oil composition according to one aspect of the present invention, the total content of components (A) to (C) may be 50% by mass or more, 55% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, 93% by mass or more, 95% by mass or more, or 97% by mass or more, based on the total amount (100% by mass) of the lubricating oil composition, or it may be 100% by mass or less, 99.5% by mass or less, 99.0% by mass or less, or 98.5% by mass or less.

[0014] In one embodiment of the present invention, the lubricating oil composition has its base number adjusted to 0.05 to 1.30 mgKOH / g by adjusting the content of component (B) and other basic compounds. This makes it possible to obtain a lubricating oil composition that balances frictional properties and immersion resistance with respect to rubber. The base number of the lubricating oil composition according to one embodiment of the present invention is 0.05 mg KOH / g or higher, from the viewpoint of providing a lubricating oil composition with improved resistance to immersion in rubber, but it is preferably 0.10 mg KOH / g or higher, 0.12 mg KOH / g or higher, 0.14 mg KOH / g or higher, 0.16 mg KOH / g or higher, 0.18 mg KOH / g or higher, or 0.20 mg KOH / g or higher, and may also be 0.30 mg KOH / g or higher, 0.40 mg KOH / g or higher, 0.50 mg KOH / g or higher, 0.60 mg KOH / g or higher, or 0.70 mg KOH / g or higher, and from the viewpoint of providing a lubricating oil composition with improved frictional properties against rubber, 1.30 mg KOH / g is also acceptable. While the amount is less than or equal to OH / g, it is preferable to set it to 1.20 mg KOH / g or less, 1.10 mg KOH / g or less, 1.00 mg KOH / g or less, 0.95 mg KOH / g or less, 0.90 mg KOH / g or less, or 0.85 mg KOH / g or less. Furthermore, it may also be 0.80 mg KOH / g or less, 0.75 mg KOH / g or less, 0.70 mg KOH / g or less, 0.65 mg KOH / g or less, 0.60 mg KOH / g or less, 0.55 mg KOH / g or less, 0.50 mg KOH / g or less, 0.45 mg KOH / g or less, 0.40 mg KOH / g or less, 0.35 mg KOH / g or less, 0.30 mg KOH / g or less, or 0.25 mg KOH / g or less.

[0015] The details of each component contained in a lubricating oil composition according to one embodiment of the present invention will be described below.

[0016] <Component (A): Base Oil> In one aspect of the present invention, the base oil, which is component (A), can 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 base 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 delamination, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining (hydrocracking).

[0017] Examples of synthetic oils include poly-α-olefins such as α-olefin homopolymers or α-olefin copolymers (e.g., 8-14 carbon olefin copolymers such as ethylene-α-olefin copolymers); isoparaffins; polyalkylene glycols; ester oils such as polyol esters, dibasic acid esters, and phosphate esters; ether oils such as polyphenyl ethers; alkylbenzenes; alkylnaphthalenes; GTL base oils obtained by isomerizing GTL wax (Gas To Liquids Wax) produced from natural gas by the Fischer-Tropsch process, etc.; CTL base oils obtained by direct liquefaction methods (such as the Bergius process) in which coal is crushed, mixed with a solvent, and reacted directly with hydrogen under high temperature and pressure; and CTL base oils obtained by indirect liquefaction methods (such as the Fischer-Tropsch process) in which coal is gasified (coal gasification), and the resulting gas is separated and purified and reacted with the raw materials to liquefy it. Component (A) used in one aspect of the present invention may contain one or more selected from these synthetic oils, or it may not contain one or more selected from these synthetic oils.

[0018] In one aspect of the present invention, component (A) preferably includes one or more selected from mineral oils classified as Group II and Group III of the API (American Petroleum Institute) base oil categories, and synthetic oils.

[0019] The kinematic viscosity of component (A) used in one aspect of the present invention at 40°C is 3.0 mm². ２ / s or more, 4.0mm ２ / s or more, 5.0mm ２ / s or more, 5.5mm ２ / s or more, 6.0 mm ２ / s or more, 6.5 mm ２ / s or more, or 7.0 mm ２ / s or more is preferable, and 80.0 mm ２ / s or less, 70.0 mm ２ / s or less, 60.0 mm ２ / s or less, 50.0 mm ２ / s or less, 40.0 mm ２ / s or less, 30.0 mm ２ / s or less, 25.0 mm ２ / s or less, 20.0 mm ２ / s or less, 15.0 mm ２ / s or less, 12.0 mm ２ / s or less, 10.0 mm ２ / s or less, 9.0 mm ２ / s or less, or 8.0 mm ２ / s or less is preferable.

[0020] The kinematic viscosity at 100 °C of component (A) used in one aspect of the present invention is 1.0 mm ２ / s or more, 1.2 mm ２ / s or more, 1.4 mm ２ / s or more, 1.6 mm ２ / s or more, 1.8 mm ２ / s or more, 2.0 mm ２ / s or more, or 2.1 mm ２ / s or more is preferable, and 20.0 mm ２ / s or less, 18.0 mm ２ / s or less, 16.0 mm ２ / s or less, or 14.0 mm ２ / s or less, 12.0 mm ２ / s or less, 10.0 mm ２ / s or less, 9.0 mm ２ / s or less, or 8.0 mm ２ / s or less, 7.0 mm ２ / s or less, 6.0 mm ２ / s or less, 5.0 mm ２ / s or less, 4.5 mm ２ / s or less, 4.0 mm ２ / s or less, 3.8 mm ２ / s or less, 3.6 mm ２ / s or less, 3.4 mm２ / s or less, 3.2mm ２ / s or less, 3.0mm ２ / s or less, 2.8mm ２ / s or less, 2.6mm ２ / s or less or 2.4mm ２ It is preferable to keep it below / s.

[0021] Furthermore, the viscosity index of component (A) used in one aspect of the present invention is preferably 70 or higher, 80 or higher, 90 or higher, or 100 or higher, and may also be 400 or lower, 350 or lower, 300 or lower, 250 or lower, 200 or lower, or 180 or lower. In addition, the viscosity index of component (A) used in one aspect of the present invention may not be calculable.

[0022] Furthermore, in one embodiment of the present invention, when a mixed oil is used as component (A), it is preferable that the kinematic viscosity and viscosity index of the mixed oil are within the above range. For this reason, a low-viscosity base oil and a high-viscosity base oil may be used in combination to prepare the mixed oil so that the kinematic viscosity and viscosity index are within the above range. The mixed oil may be a mixed oil obtained by combining two or more base oils whose kinematic viscosity and viscosity index at 40°C fall within the above range, or it may be a mixed oil obtained by combining a base oil whose kinematic viscosity and viscosity index at 40°C fall within the above range and a base oil whose kinematic viscosity and viscosity index at 40°C fall within the above range. Alternatively, a mixed oil may be obtained by combining a low-viscosity base oil whose kinematic viscosity and viscosity index at 40°C do not fall within the above range and a high-viscosity base oil, and adjusting them to fall within the above range.

[0023] In a lubricating oil composition according to one aspect of the present invention, the content of component (A) is 40% by mass or more, 45% by mass or more, 50% by mass or more, 55% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, 92% by mass or more, or 95% by mass or more, based on the total amount (100% by mass) of the lubricating oil composition, or it may be 99.9% by mass or less, 99.5% by mass or less, 99.0% by mass or less, or 98.5% by mass or less.

[0024] <Component (B): Basic Compound> A lubricating oil composition according to one aspect of the present invention contains one or more basic compounds (B) selected from amide compounds (B1) and imide compounds (B2). By including such a specific component (B), a lubricating oil composition with improved resistance to immersion in rubber can be made. This characteristic effectively suppresses the immersion of the lubricating oil composition into the rubber oil seals of a shock absorber when the lubricating oil composition is used to lubricate the shock absorber, thereby contributing to the prevention of oil leakage. The component (B) used in one aspect of the present invention may be only an amide compound (B1), only an imide compound (B2), or a combination of an amide compound (B1) and an imide compound (B2).

[0025] The base number derived from component (B) used in one aspect of the present invention is preferably 0.05 mg KOH / g or more, 0.10 mg KOH / g or more, 0.12 mg KOH / g or more, 0.14 mg KOH / g or more, 0.16 mg KOH / g or more, 0.18 mg KOH / g or more, or 0.20 mg KOH / g or more, from the viewpoint of providing a lubricating oil composition with improved resistance to immersion in rubber, and may also be 0.30 mg KOH / g or more, 0.40 mg KOH / g or more, 0.50 mg KOH / g or more, 0.60 mg KOH / g or more, or 0.70 mg KOH / g or more, and from the viewpoint of providing a lubricating oil composition with improved frictional properties for rubber, 1.30 mg K While the amount is less than or equal to OH / g, it is preferable to set it to 1.20 mg KOH / g or less, 1.10 mg KOH / g or less, 1.00 mg KOH / g or less, 0.95 mg KOH / g or less, 0.90 mg KOH / g or less, or 0.85 mg KOH / g or less. Furthermore, it may also be 0.80 mg KOH / g or less, 0.75 mg KOH / g or less, 0.70 mg KOH / g or less, 0.65 mg KOH / g or less, 0.60 mg KOH / g or less, 0.55 mg KOH / g or less, 0.50 mg KOH / g or less, 0.45 mg KOH / g or less, 0.40 mg KOH / g or less, 0.35 mg KOH / g or less, 0.30 mg KOH / g or less, or 0.25 mg KOH / g or less.

[0026] In a lubricating oil composition according to one aspect of the present invention, the content of component (B) is adjusted so that the base number of the lubricating oil composition falls within the above range. However, from the viewpoint of providing a lubricating oil composition with improved resistance to immersion in rubber, it may also be 0.01% by mass or more, 0.05% by mass or more, 0.10% by mass or more, 0.15% by mass or more, 0.20% by mass or more, 0.25% by mass or more, 0.30% by mass or more, 0.35% by mass or more, 0.40% by mass or more, 0.45% by mass or more, 0.50% by mass or more, 0.60% by mass or more, 0.70% by mass or more, 0.80% by mass or more, 0.90% by mass or more, 1.00% by mass or more, 1.10% by mass or more, 1.20% by mass or more, or 1.30% by mass or more. Furthermore, from the viewpoint of providing a lubricating oil composition with improved frictional properties against rubber... , 4.00 mass% or less, 4.50 mass% or less, 4.00 mass% or less, 3.50 mass% or less, 3.00 mass% or less, 2.80 mass% or less, 2.60 mass% or less, 2.40 mass% or less, 2 .20 mass% or less, 2.00 mass% or less, 1.90 mass% or less, 1.80 mass% or less, 1.70 mass% or less, 1.60 mass% or less, 1.50 mass% or less, 1.40 mass% or less, 1.3 0 mass% or less, 1.20 mass% or less, 1.10 mass% or less, 1.10 mass% or less, 1.00 mass% or less, 0.90 mass% or less, 0.80 mass% or less, 0.70 mass% or less, 0.60 quality It may be less than or equal to 0.50 mass%, less than 0.45 mass%, less than 0.40 mass%, less than 0.35 mass%, less than 0.30 mass%, less than 0.25 mass%, or less than 0.20 mass%.

[0027] In a lubricating oil composition according to one aspect of the present invention, the content of component (B) in terms of nitrogen atoms is adjusted so that the base number of the lubricating oil composition falls within the above range. However, from the viewpoint of providing a lubricating oil composition with improved resistance to immersion in rubber, it may also be 0.001% by mass or more, 0.002% by mass or more, 0.004% by mass or more, 0.006% by mass or more, 0.008% by mass or more, 0.010% by mass or more, 0.012% by mass or more, 0.014% by mass or more, 0.016% by mass or more, 0.018% by mass or more, 0.020% by mass or more, 0.022% by mass or more, or 0.023% by mass or more. Furthermore, from the viewpoint of providing a lubricating oil composition with improved frictional properties for rubber, the amount may be 0.100% by mass or less, 0.090% by mass or less, 0.080% by mass or less, 0.070% by mass or less, 0.060% by mass or less, 0.050% by mass or less, 0.045% by mass or less, 0.040% by mass or less, 0.035% by mass or less, 0.030% by mass or less, 0.025% by mass or less, 0.023% by mass or less, 0.021% by mass or less, 0.020% by mass or less, 0.018% by mass or less, 0.016% by mass or less, 0.014% by mass or less, 0.012% by mass or less, or 0.010% by mass or less.

[0028] <Component (B1): Amide Compound> In one aspect of the present invention, the "amide compound" refers to a compound having an amide structure (excluding structures corresponding to imide structures) represented by the following formula (b1-0), and includes chain compounds having the amide structure and cyclic compounds having the amide structure. Furthermore, the "amide compound" may be any compound having the amide structure, and includes, for example, fatty acid amides, aromatic amides, alicyclic amides, etc. (In the above formula, * indicates the bonding position.)

[0029] Among such amide compounds, from the viewpoint of providing a lubricating oil composition with improved resistance to immersion in rubber, it is preferable that component (B1) used in one aspect of the present invention includes an amide compound (B11) having at least one hydrocarbon group containing an imino structure (-NH-). The content ratio of component (B11) in component (B1) used in one aspect of the present invention is preferably 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, 95% by mass or more, 98% by mass or more, or 100% by mass, based on the total amount (100% by mass) of component (B1).

[0030] In a lubricating oil composition according to one embodiment of the present invention, from the viewpoint of making the effects of the present invention more readily apparent, the content of amide compounds other than component (B11) may be less than 3.00% by mass, less than 2.50% by mass, less than 2.00% by mass, less than 1.50% by mass, less than 1.00% by mass, less than 0.80% by mass, less than 0.60% by mass, less than 0.40% by mass, less than 0.20% by mass, less than 0.10% by mass, less than 0.05% by mass, less than 0.02% by mass, less than 0.01% by mass, less than 0.005% by mass, less than 0.001% by mass, less than 0.0005% by mass, or less than 0.0001% by mass, based on the total amount (100% by mass) of the lubricating oil composition.

[0031] The hydrocarbon group of the amide compound (B11) may be an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, or an aryl group having 6 to 30 carbon atoms that may be substituted with an alkyl group having 1 to 6 carbon atoms, but it is preferable that it is an alkyl group having 1 to 30 carbon atoms that has at least one imino structure (-NH-).

[0032] Examples of the alkyl groups include methyl, ethyl, propyl (n-propyl, isopropyl), butyl (n-butyl, s-butyl, t-butyl, isobutyl), pentyl, hexyl, 2-ethylhexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, hexadecyl, and octadecyl groups. These alkyl groups may be linear or branched, but branched alkyl groups are preferred. The number of carbon atoms in the alkyl group is 1 to 30, but may be 2 or more, 5 or more, 8 or more, 10 or more, or 12 or more, or 28 or less, 26 or less, 24 or less, 22 or less, or 20 or less.

[0033] Examples of the aforementioned alkenyl group include ethenyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, and octadecenyl groups. These alkenyl groups may be linear or branched alkenyl groups, but branched alkenyl groups are preferred. The number of carbon atoms in the alkenyl group is 2 to 30, but may be 3 or more, 5 or more, 8 or more, 10 or more, or 12 or more, or 28 or less, 26 or less, 24 or less, 22 or less, or 20 or less.

[0034] Examples of the aryl group include phenyl, naphthyl, anthryl, phenanthryl, biphenyl, terphenyl, and phenylnaphthyl groups, with phenyl being preferred. The "C1-C6 alkyl groups" that can substitute for these aryl groups are, among the alkyl groups mentioned above, C1-C6 alkyl groups.

[0035] In one aspect of the present invention, component (B11) can be a condensation compound of a monoamine or polyamine and a carboxylic acid, but from the viewpoint of providing a lubricating oil composition with improved resistance to immersion in rubber, a compound represented by the following general formula (b1-1) is preferred.

[0036] In the above general formula (b1-1), R Ｂ１ R is a hydrocarbon group having 1 to 30 carbon atoms. Ｂ２ X is a hydrocarbon group having 1 to 30 carbon atoms, which may be substituted with a hydrogen atom or a hydroxyl group. Each X is independently a hydrogen atom or -(C=O)-R Ｂ１ An acyl group represented by R Ｂ１ The above applies. b1 is an integer from 1 to 6, preferably an integer from 1 to 4, more preferably an integer from 2 to 3, and even more preferably 2. d2 is an integer of 1 or more, preferably an integer from 1 to 20, more preferably an integer from 1 to 15, even more preferably an integer from 1 to 10, even more preferably an integer from 2 to 8, and particularly preferably an integer from 2 to 6.

[0037] R Ｂ１ and R Ｂ２ Examples of hydrocarbon groups that can be selected include C1-C30 alkyl groups, C2-C30 alkenyl groups, and C6-C30 aryl groups which may be substituted with C1-C6 alkyl groups. It is preferable that the group be a C1-C30 alkyl group or a C2-C30 alkenyl group, more preferably a C1-C30 alkyl group, and even more preferably a C5-C30 branched alkyl group. The specific types of groups and preferred carbon numbers for the alkyl groups, alkenyl groups, and aryl groups are as described above.

[0038] From the viewpoint of providing a lubricating oil composition with improved resistance to immersion in rubber, component (B11) used in one aspect of the present invention is R in the general formula (b1-1). Ｂ１ is an alkyl group having 1 to 30 carbon atoms, and R Ｂ２ X is a hydrogen atom, and X is independently a hydrogen atom or -(C=O)-R Ｂ１ The acyl group represented by (R Ｂ１ A compound in which (the alkyl group has 1 to 30 carbon atoms) is preferred.

[0039] In a lubricating oil composition according to one aspect of the present invention, the content of component (B11) in terms of nitrogen atoms is adjusted so that the base number of the lubricating oil composition falls within the above range. However, from the viewpoint of providing a lubricating oil composition with improved resistance to immersion in rubber, the following are possible: 0.001% by mass or more, 0.002% by mass or more, 0.004% by mass or more, 0.006% by mass or more, 0.008% by mass or more, 0.010% by mass or more, 0.012% by mass or more, 0.014% by mass or more, 0.016% by mass or more, 0.018% by mass or more, 0.020% by mass or more, 0.022% by mass or more, or 0.023% by mass or less. It is also acceptable to use the above amount, and from the viewpoint of providing a lubricating oil composition with improved frictional properties for rubber, it may be 0.100% by mass or less, 0.090% by mass or less, 0.080% by mass or less, 0.070% by mass or less, 0.060% by mass or less, 0.050% by mass or less, 0.045% by mass or less, 0.040% by mass or less, 0.035% by mass or less, 0.030% by mass or less, 0.025% by mass or less, 0.023% by mass or less, 0.021% by mass or less, 0.020% by mass or less, 0.018% by mass or less, 0.016% by mass or less, 0.014% by mass or less, or 0.013% by mass or less.

[0040] <Component (B2): Imide Compound> In one aspect of the present invention, "imide compound" means a compound having an imide structure represented by the following formula (b2-0), and includes chain compounds having said imide structure and cyclic compounds having said imide structure. (In the above formula, * indicates the bonding position.)

[0041] Component (B2) used in one aspect of the present invention may be any compound having an imide structure represented by formula (b2-0), and this compound may be a modified imide compound obtained by reacting it with one or more selected from boron compounds, alcohols, aldehydes, ketones, alkylphenols, cyclic carbonates, epoxy compounds, and organic acids. A boron-modified imide compound is preferred as such a modified product.

[0042] In one aspect of the present invention, component (B2) used preferably contains one or more non-boron alkenyl succinimides (B21) selected from non-boron modified alkenyl succinic acid monoimides and non-boron modified alkenyl succinic acid bisimides, and one or more boron-modified products (B22) of component (B21), from the viewpoint of providing a lubricating oil composition with improved resistance to immersion in rubber. In one aspect of the present invention, the total content ratio of component (B21) and component (B22) in component (B2) used preferably is 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, 95% by mass or more, 98% by mass or more, or 100% by mass, based on the total amount of component (B2) (100% by mass).

[0043] Component (B21) used in one aspect of the present invention includes non-boron modified alkenyl succinate monoimide represented by the following general formula (b2-1) and non-boron modified alkenyl succinate biimide represented by the following general formula (b2-2). Component (B22) used in one aspect of the present invention includes boron-modified compounds of the compound represented by the following general formula (b2-1) or formula (b2-2).

[0044] In the above general formulas (b2-1) and (b2-2), R Ｂ３ , R Ｂ４ and R Ｂ５ Each of these is an alkenyl group having a mass-average molecular weight (Mw) of 500 to 3000 (preferably 900 to 2500). Ｂ３ , R Ｂ４ and R Ｂ５ Examples of alkenyl groups that can be selected include polybutenyl groups, polyisobutenyl groups, ethylene-propylene copolymers, and among these, polybutenyl groups or polyisobutenyl groups are preferred. １ A ２ and A ３ Each of these is an alkylene group having 2 to 5 carbon atoms. z1 is an integer from 0 to 10, preferably an integer from 1 to 4, more preferably 2 or 3. z2 is an integer from 1 to 10, preferably an integer from 2 to 5, more preferably 3 or 4.

[0045] In a lubricating oil composition according to one aspect of the present invention, the content of component (B21) in terms of nitrogen atoms is adjusted so that the base number of the lubricating oil composition falls within the above range. However, from the viewpoint of providing a lubricating oil composition with improved resistance to immersion in rubber, the content may also be 0.001% by mass or more, 0.002% by mass or more, 0.004% by mass or more, 0.006% by mass or more, 0.008% by mass or more, 0.010% by mass or more, 0.012% by mass or more, 0.014% by mass or more, 0.016% by mass or more, 0.018% by mass or more, 0.020% by mass or more, 0.022% by mass or more, or 0.023% by mass or more. Furthermore, from the viewpoint of providing a lubricating oil composition with improved frictional properties for rubber, the amount may be 0.100% by mass or less, 0.090% by mass or less, 0.080% by mass or less, 0.070% by mass or less, 0.060% by mass or less, 0.050% by mass or less, 0.045% by mass or less, 0.040% by mass or less, 0.035% by mass or less, 0.030% by mass or less, 0.025% by mass or less, 0.023% by mass or less, 0.021% by mass or less, 0.020% by mass or less, 0.018% by mass or less, 0.016% by mass or less, 0.014% by mass or less, 0.012% by mass or less, or 0.010% by mass or less.

[0046] In a lubricating oil composition according to one aspect of the present invention, when component (B22) is used, the content of component (B22) in terms of boron atoms may be 10 ppm or more, 30 ppm or more, 50 ppm or more, 70 ppm or more, or 100 ppm or more, based on the total amount (100% by mass) of the lubricating oil composition, from the above viewpoint, or it may be 800 ppm or less, 600 ppm or less, 500 ppm or less, 400 ppm or less, 300 ppm or less, 250 ppm or less, 200 ppm or less, or 180 ppm or less.

[0047] In a lubricating oil composition according to one aspect of the present invention, the content ratio [B / N] of boron atoms derived from component (B22) to nitrogen atoms derived from component (B2) may be 0.01 or more, 0.03 or more, 0.05 or more, 0.07 or more, 0.10 or more, 0.12 or more, or 0.15 or more, or 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, 0.30 or less, or 0.25 or less.

[0048] <Other basic compounds besides component (B)> A lubricating oil composition according to one embodiment of the present invention may contain other basic compounds besides component (B) as long as the effects of the present invention are not impaired. Examples of other basic compounds besides component (B) include amine compounds such as monoamines having one amino nitrogen atom in one molecule, diamines having two amino nitrogen atoms in one molecule, and polyamines having three or more amino nitrogen atoms in one molecule.

[0049] However, from the viewpoint of making the effects of the present invention more readily apparent, it is preferable that the content of these amine compounds be as low as possible. In a lubricating oil composition according to one embodiment of the present invention, from the viewpoint of making the effects of the present invention more readily apparent, it is preferable that the composition is substantially free of primary amines, secondary amines, tertiary amines, or diamines, and more preferably that it is substantially free of primary amines or diamines.

[0050] In a lubricating oil composition according to one embodiment of the present invention, from the viewpoint of making the effects of the present invention more readily apparent, the content of the primary amine may be less than 0.30% by mass, less than 0.20% by mass, less than 0.10% by mass, less than 0.05% by mass, less than 0.01% by mass, less than 0.001% by mass, or less than 0.0001% by mass, based on the total amount (100% by mass) of the lubricating oil composition.

[0051] In a lubricating oil composition according to one embodiment of the present invention, from the viewpoint of making the effects of the present invention more readily apparent, the content of the secondary amine may be less than 0.30% by mass, less than 0.20% by mass, less than 0.10% by mass, less than 0.05% by mass, less than 0.01% by mass, less than 0.001% by mass, or less than 0.0001% by mass, based on the total amount (100% by mass) of the lubricating oil composition.

[0052] In a lubricating oil composition according to one embodiment of the present invention, from the viewpoint of making the effects of the present invention more readily apparent, the content of the tertiary amine may be less than 0.30% by mass, less than 0.20% by mass, less than 0.10% by mass, less than 0.05% by mass, less than 0.01% by mass, less than 0.001% by mass, or less than 0.0001% by mass, based on the total amount (100% by mass) of the lubricating oil composition.

[0053] In a lubricating oil composition according to one embodiment of the present invention, from the viewpoint of making the effects of the present invention more readily apparent, the content of diamine may be less than 0.30% by mass, less than 0.20% by mass, less than 0.10% by mass, less than 0.05% by mass, less than 0.01% by mass, less than 0.001% by mass, or less than 0.0001% by mass, based on the total amount (100% by mass) of the lubricating oil composition.

[0054] In a lubricating oil composition according to one embodiment of the present invention, from the viewpoint of making the effects of the present invention more readily apparent, the content of triamine may be less than 0.30% by mass, less than 0.20% by mass, less than 0.10% by mass, less than 0.05% by mass, less than 0.01% by mass, less than 0.001% by mass, or less than 0.0001% by mass, based on the total amount (100% by mass) of the lubricating oil composition.

[0055] The base number derived from components other than component (B) used in one embodiment of the present invention may be 0.20 mg KOH / g or less, 0.15 mg KOH / g or less, 0.12 mg KOH / g or less, 0.10 mg KOH / g or less, 0.08 mg KOH / g or less, 0.06 mg KOH / g or less, 0.04 mg KOH / g or less, 0.02 mg KOH / g or less, or 0.01 mg KOH / g or less, from the viewpoint of making the effects of the present invention more easily expressed.

[0056] <Component (C): Phosphite ester having an alkyl or alkenyl group with 11 or more carbon atoms> A lubricating oil composition according to one aspect of the present invention contains a phosphite ester having an alkyl or alkenyl group with 11 or more carbon atoms as component (C). In one aspect of the present invention, component (C) may be used alone or in combination of two or more. By including component (C), a lubricating oil composition can be made that reduces the coefficient of friction μ between rubber and metal and improves the frictional properties of rubber. This property contributes to improving the ride comfort of a vehicle body equipped with a shock absorber by reducing the coefficient of friction between the bronze bushing and the rubber oil seal of the shock absorber when the lubricating oil composition is used to lubricate the shock absorber. Furthermore, component (C) also contributes to improving the frictional properties between metals and the wear resistance of the lubricating oil composition.

[0057] On the other hand, the presence of component (C) can also be a factor that causes a decrease in the immersion resistance to rubber. Therefore, in one aspect of the present invention, by adjusting the content of component (C) to a predetermined range, a lubricating oil composition can be made that improves frictional properties to rubber while maintaining good immersion resistance to rubber. In the lubricating oil composition of one aspect of the present invention, the content of component (C) is 0.01% by mass or more, based on the total amount (100% by mass) of the lubricating oil composition, from the viewpoint of making a lubricating oil composition that improves frictional properties to rubber, frictional properties between metals, and wear resistance in a well-balanced manner, but can be 0.05% by mass or more, 0.07% by mass or more, 0.10% by mass or more, 0.15% by mass or more, 0.20% by mass or more, 0.25% by mass or more, 0.30% by mass or more, 0.35% by mass or more, 0.40% by mass or more, 0.45% by mass or more. It is preferable that the amount be % by mass or more, or 0.50% by mass or more, and from the viewpoint of providing a lubricating oil composition with good resistance to immersion in rubber, it is 1.90% by mass or less, but it is preferable that it be 1.80% by mass or less, 1.70% by mass or less, 1.60% by mass or less, 1.50% by mass or less, 1.40% by mass or less, 1.30% by mass or less, 1.20% by mass or less, 1.10% by mass or less, 1.00% by mass or less, 0.90% by mass or less, 0.80% by mass or less, 0.70% by mass or less, or 0.60% by mass or less.

[0058] In a lubricating oil composition according to one aspect of the present invention, the content of component (C) in terms of phosphorus atoms is, based on the total amount (100% by mass) of the lubricating oil composition, 5 ppm or more by mass, 10 ppm or more by mass, 30 ppm or more by mass, 50 ppm or more by mass, 70 ppm or more by mass, 100 ppm or more by mass, 120 ppm or more by mass, 150 ppm or more by mass, 170 ppm or more by mass, 200 ppm or more by mass, 220 ppm or more by mass, 250 ppm or more by mass, 270 ppm or more by mass, The concentration may be 300 ppm by mass or more, or 320 ppm by mass or more. Furthermore, from the viewpoint of providing a lubricating oil composition with good resistance to immersion in rubber, it may be 1500 ppm by mass or less, 1400 ppm by mass or less, 1300 ppm by mass or less, 1200 ppm by mass or less, 1100 ppm by mass or less, 1000 ppm by mass or less, 900 ppm by mass or less, 800 ppm by mass or less, 700 ppm by mass or less, 600 ppm by mass or less, 500 ppm by mass or less, 450 ppm by mass or less, 400 ppm by mass or less, 350 ppm by mass or less, 300 ppm by mass or less, or 280 ppm by mass or less.

[0059] In a lubricating oil composition according to one aspect of the present invention, the content ratio of component (B) to component (C) [(B) / (C)] is preferably 0.20 or more, 0.25 or more, 0.30 or more, 0.35 or more, or 0.40 or more by mass, from the viewpoint of providing a lubricating oil composition with improved resistance to immersion in rubber. Furthermore, it may be 0.45 or more, 0.50 or more, 0.55 or more, 0.60 or more, 0.65 or more, 0.70 or more, 0.75 or more, 0.80 or more, 0.85 or more, 0.90 or more, or 1.00 or more, and also a lubricating oil composition with improved frictional properties against rubber. From the viewpoint of composition, it is preferable to have a value of 3.50 or less, 3.40 or less, 3.30 or less, 3.20 or less, 3.10 or less, 3.00 or less, 2.90 or less, 2.80 or less, 2.70 or less, or 2.60 or less. Furthermore, it may be 2.50 or less, 2.40 or less, 2.30 or less, 2.20 or less, 2.10 or less, 2.00 or less, 1.90 or less, 1.80 or less, 1.70 or less, 1.60 or less, 1.50 or less, 1.40 or less, 1.30 or less, 1.20 or less, 1.10 or less, 1.00 or less, 0.90 or less, 0.80 or less, 0.70 or less, or 0.60 or less.

[0060] Component (C) used in one aspect of the present invention may include, for example, an acidic phosphite represented by the following general formula (c-1) or (c-2).

[0061] In the above formula (c-1) or (c-2), R Ｃ１ R is an alkyl or alkenyl group having 11 or more carbon atoms. Ｃ２ Examples include alkyl groups having 1 to 30 carbon atoms, alkenyl groups having 2 to 30 carbon atoms, and aryl groups having 6 to 30 carbon atoms that may be substituted with alkyl groups having 1 to 6 carbon atoms.

[0062] R Ｃ１The number of carbon atoms in the alkyl group that can be selected is 11 or more, but from the viewpoint of providing a lubricating oil composition that balances and further improves frictional properties with respect to rubber, frictional properties between metals, and wear resistance, it is preferable to have 12 or more carbon atoms, and further, it may be 14 or more, 16 or more, or 18 or more, and it is also preferable to have 30 or less, 28 or less, 26 or less, 24 or less, 22 or less, 20 or less, 18 or less, 16 or less, or 14 or less. Ｃ１ Examples of alkyl groups that can be selected include undecyl, dodecyl (lauryl), tridecyl, tetradecyl, hexadecyl, and octadecyl groups, and may be linear or branched alkyl groups.

[0063] R Ｃ１ The number of carbon atoms in the alkenyl group that can be selected is 11 or more, but from the viewpoint of obtaining a lubricating oil composition that has a good balance of improved frictional properties with rubber, frictional properties between metals, and wear resistance, it is preferable to have 12 or more, 14 or more, 16 or more, or 18 or more, and also preferable to have 30 or less, 28 or less, 26 or less, 24 or less, 22 or less, 20 or less, or 18 or less. Ｃ１ Examples of alkenyl groups that can be selected include undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, and octadecenyl (oleyl) groups, and may be linear or branched alkenyl groups.

[0064] R Ｃ２ Examples of alkyl groups that can be selected include methyl group, ethyl group, propyl group (n-propyl group, isopropyl group), butyl group (n-butyl group, s-butyl group, t-butyl group, isobutyl group), pentyl group, hexyl group, 2-ethylhexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, hexadecyl group, octadecyl group, and the like. These alkyl groups may be linear or branched. Ｃ２The number of carbon atoms in the alkyl group that can be selected is 1 to 30, but it may be 2 or more, 4 or more, 6 or more, 8 or more, or 10 or more. However, from the viewpoint of providing a lubricating oil composition that balances and further improves frictional properties with respect to rubber, frictional properties between metals, and wear resistance, it is preferable to have 11 or more, 12 or more, 14 or more, 16 or more, or 18 or more, and it is also preferable to have 30 or less, 28 or less, 26 or less, 24 or less, 22 or less, or 20 or less.

[0065] R Ｃ２ Examples of the alkenyl groups that can be selected include ethenyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, and octadecenyl groups. These alkenyl groups may be linear or branched. The number of carbon atoms in the alkenyl group is 2 to 30, but may be 3 or more, 5 or more, 6 or more, 8 or more, or 10 or more. However, from the viewpoint of creating a lubricating oil composition that balances and further improves frictional properties with rubber, frictional properties between metals, and wear resistance, it is preferable to have 11 or more, 12 or more, 14 or more, 16 or more, or 18 or more, and also preferable to have 30 or less, 28 or less, 26 or less, 24 or less, 22 or less, or 20 or less.

[0066] R Ｃ２ Examples of aryl groups that can be selected include phenyl, naphthyl, anthryl, phenanthryl, biphenyl, terphenyl, and phenylnaphthyl groups, with phenyl being preferred. Examples of C1-C6 alkyl groups that can substitute for these aryl groups include C1-C6 alkyl groups from the above-mentioned alkyl groups.

[0067] Among these, R Ｃ２It is preferably an alkyl group having 1 to 30 carbon atoms, and more preferably an alkyl group having 11 to 30 carbon atoms, from the viewpoint of providing a lubricating oil composition that balances and further improves frictional properties with respect to rubber, frictional properties between metals, and wear resistance. Also, from the same viewpoint as above, R in formula (c-1) Ｃ１ and R Ｃ２ It is preferable that they are the same alkyl group.

[0068] In one aspect of the present invention, the phosphite ester used as component (C) may be in the form of an amine salt. The amine forming the amine salt is preferably a compound represented by the following general formula (c-3). This amine may be used alone or in combination of two or more types.

[0069] In the above general formula (c-3), r is an integer between 1 and 3, and is preferably 1. ｘ Each of these is independently an alkyl group having 6 to 18 carbon atoms, an alkenyl group having 6 to 18 carbon atoms, an aryl group having 6 to 18 carbon atoms, or a hydroxyalkyl group having 6 to 18 carbon atoms. ｘ If multiple R ｘ They may be the same, or they may be different from one another.

[0070] R ｘ The C6-C18 alkyl group, C6-C18 alkenyl group, and C6-C18 aryl group that can be selected as are the above-mentioned R Ｂ Examples of selectable alkyl groups, alkenyl groups, and aryl groups include those with a number of carbon atoms within the above range. Furthermore, examples of hydroxyalkyl groups having 6 to 18 carbon atoms include those in which a hydrogen atom of an alkyl group having 6 to 18 carbon atoms is substituted with a hydroxyl group, specifically including hydroxyhexyl group, hydroxyoctyl group, hydroxydodecyl group, hydroxytridecyl group, etc.

[0071] <Other phosphorus compounds other than component (C)> A lubricating oil composition according to one embodiment of the present invention may contain phosphorus compounds other than component (C) to the extent that they do not impair the effects of the present invention. Examples of phosphorus compounds other than component (C) include phosphorous phosphate esters (CX) that do not correspond to component (C) and do not have an alkyl group or alkenyl group having 11 or more carbon atoms, neutral phosphorus esters, acidic phosphorus esters, and amine salts of acidic phosphorus esters.

[0072] However, in one aspect of the present invention, from the viewpoint of providing a lubricating oil composition that balances and further improves frictional properties with respect to rubber, frictional properties between metals, and wear resistance, it is preferable that the amount of phosphorous acid ester (CX) that does not have an alkyl group having 11 or more carbon atoms or an alkenyl group having 11 or more carbon atoms is as small as possible. From the above viewpoint, it is preferable that the content of component (CX) be less than 0.10% by mass, less than 0.05% by mass, less than 0.01% by mass, less than 0.001% by mass, less than 0.0001% by mass, or less than 0.00001% by mass, based on the total amount (100% by mass) of the lubricating oil composition.

[0073] Examples of neutral phosphate esters include compounds represented by the following general formula (c'-4). Examples of acidic phosphate esters include compounds represented by the following general formula (c'-5) or (c'-6), and examples of amine salts of acidic phosphate esters include amine salts of compounds represented by the following general formula (c'-5) or (c'-6). In the above formula, R can be independently an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or an aryl group having 6 to 18 carbon atoms which may be substituted with an alkyl group having 1 to 6 carbon atoms. Specifically, R in the above general formula (c-1) Ｃ２ The same groups that can be selected as are listed. Note that multiple Rs may be the same or may be different from one another.

[0074] In one aspect of the present invention, the lubricating oil composition is preferable to have a low amount of acidic phosphate ester and its amine salt, from the viewpoint of providing a lubricating oil composition with good frictional properties and immersion resistance to rubber. From the above viewpoint, the content of acidic phosphate ester and its amine salt is preferably less than 0.10% by mass, less than 0.05% by mass, less than 0.01% by mass, less than 0.001% by mass, less than 0.0001% by mass, or less than 0.00001% by mass, based on the total amount (100% by mass) of the lubricating oil composition.

[0075] <Additives for Lubricating Oils> A lubricating oil composition according to one embodiment of the present invention may contain, as necessary, lubricating oil additives other than components (B) to (C), to the extent that the effects of the present invention are not impaired. Examples of such lubricating oil additives include pour point depressants, viscosity index improvers, antioxidants, metal-based detergents, rust inhibitors, defoamers, colorants, and the like. These various additives may be used individually or in combination of two or more.

[0076] In a lubricating oil composition according to one aspect of the present invention, the content of each of these lubricating oil additives can be appropriately adjusted within a range that does not impair the effects of the present invention. Based on the total amount (100% by mass) of the lubricating oil composition, the content of each additive can be independently set to typically 0.001% by mass or more, 0.005% by mass or more, 0.01% by mass or more, 0.05% by mass or more, or 0.10% by mass or more, or 15% by mass or less, 10% by mass or less, 5.0% by mass or less, 2.0% by mass or less, or 1.0% by mass or less.

[0077] Furthermore, in one embodiment of the present invention, the content of the above-mentioned lubricating oil additives may be limited, and the content of each of the above-mentioned lubricating oil additives may be less than 5.0% by mass, less than 2.0% by mass, less than 1.0% by mass, less than 0.1% by mass, less than 0.01% by mass, less than 0.001% by mass, less than 0.0001% by mass, or less than 0.00001% by mass, based on the total amount (100% by mass) of the lubricating oil composition.

[0078] [Pour Point Depressant] The lubricating oil composition according to one aspect of the present invention may further contain a pour point depressant, or it may not contain one. The pour point depressant may be used alone, or two or more may be used in combination. Examples of pour point depressants used in one aspect of the present invention include ethylene-vinyl acetate copolymer, condensate of chlorinated paraffin and naphthalene, condensate of chlorinated paraffin and phenol, polymethacrylate, polyalkylstyrene, etc., and one or more of these may be included, or one or more of these may not be included. The mass-average molecular weight (Mw) of the pour point depressant used in one aspect of the present invention 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, or 150,000 or less, 120,000 or less, 100,000 or less, 90,000 or less, or 80,000 or less.

[0079] [Viscosity Index Improver] The lubricating oil composition according to one aspect of the present invention may further contain a viscosity index improver, or it may not contain one. The viscosity index improver may be used alone, or two or more may be used in combination. Examples of viscosity index improvers used in one aspect of the present invention include polymers such as non-dispersible polymethacrylate, dispersed polymethacrylate, olefin copolymers (e.g., ethylene-propylene copolymer, etc.), dispersed olefin copolymers, and styrene copolymers (e.g., styrene-diene copolymer, styrene-isoprene copolymer, etc.), and one or more of these may be included, or one or more of these may not be included. The weight-average molecular weight (Mw) of the viscosity index improver used in one aspect 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 it 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.

[0080] [Antioxidant] The lubricating oil composition according to one embodiment of the present invention may further contain an antioxidant, or may not contain one. The antioxidant may be used alone, or two or more may be used in combination. Examples of antioxidants used in one aspect of the present invention include amine-based antioxidants such as alkylated diphenylamine, phenylnaphthylamine, and alkylated phenylnaphthylamine; 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; and sulfur-based antioxidants such as phenothiazine, dioctadecyl sulfide, dilauryl-3,3'-thiodipropionate, and 2-mercaptobenzimidazole. The invention may contain one or more of these, or it may not contain one or more of these.

[0081] [Metal-based detergent] The lubricating oil composition according to one aspect of the present invention may further contain a metal-based detergent, or it may not contain one. The metal-based detergent may be used alone, or two or more may be used in combination. Examples of metal-based detergents used in one aspect of the present invention include metal salts such as metal sulfonates, metal salicylates, and metal phenates, and one or more of these may be included, or one or more of these may not be included. Examples of metal atoms constituting the metal salt include metal atoms selected from alkali metals and alkaline earth metals, such as sodium, calcium, and magnesium, and one or more of these may be included, or one or more of these may not be included.

[0082] In addition, in a lubricating oil composition according to one embodiment of the present invention, the content of a metal-based detergent may be limited. Specifically, the content of a metal-based detergent containing metal atoms selected from calcium atoms, magnesium atoms, and sodium atoms, in terms of the amount of such metal atoms, may be less than 500 ppm by mass, less than 400 ppm by mass, less than 300 ppm by mass, less than 200 ppm by mass, less than 150 ppm by mass, less than 100 ppm by mass, less than 50 ppm by mass, less than 20 ppm by mass, less than 10 ppm by mass, or less than 5 ppm by mass, based on the total amount (100% by mass) of the lubricating oil composition.

[0083] [Rust Inhibitor] The lubricating oil composition according to one aspect of the present invention may further contain a rust inhibitor, or may not contain one. The rust inhibitor may be used alone, or two or more may be used in combination. Examples of rust inhibitors used in one aspect of the present invention include fatty acids, alkenyl succinate half esters, fatty acid soaps, alkyl sulfonates, polyhydric alcohol fatty acid esters, fatty acid amines, oxidized paraffins, alkyl polyoxyethylene ethers, etc., and one or more of these may be included, or one or more of these may not be included.

[0084] [Antifoaming agent] The lubricating oil composition according to one embodiment of the present invention may further contain an antifoaming agent or may not contain one. The antifoaming agent may be used alone or in combination of two or more types. Examples of antifoaming agents used in one embodiment of the present invention include alkyl silicone antifoaming agents, fluorosilicone antifoaming agents, fluoroalkyl ether antifoaming agents, and one or more of these may be contained or not contained.

[0085] [Coloring agent] The lubricating oil composition according to one aspect of the present invention may further contain a coloring agent or may not contain one. The coloring agent may be used alone or in combination of two or more types. Examples of coloring agents used in one aspect of the present invention include dyes and pigments, and one or more of these may be included or not included.

[0086] [Fatty Acid Ester Compounds] A lubricating oil composition according to one embodiment of the present invention may or may not contain a fatty acid ester compound, but by including a fatty acid ester compound, a lubricating oil composition with improved wear resistance can be obtained. Examples of fatty acid ester compounds include complete esters or partial esters obtained by the reaction of a fatty acid having a hydrocarbon group having 6 to 30 carbon atoms with a fatty acid monoalcohol or a fatty acid polyhydric alcohol. Examples of the hydrocarbon group include alkyl groups having 6 to 30 carbon atoms, alkenyl groups having 6 to 30 carbon atoms, and aryl groups having 6 to 30 carbon atoms that may be substituted with alkyl groups having 1 to 6 carbon atoms, and one or more of these may be included, or one or more of these may not be included.

[0087] Among these, fatty acid monoester compounds, which are complete or partial esters obtained by the reaction of a fatty acid having a hydrocarbon group with 6 to 30 carbon atoms with a fatty acid monoalcohol, are preferred as fatty acid ester compounds.

[0088] In a lubricating oil composition according to one aspect of the present invention, the content of the fatty acid ester compound is preferably 0.01% by mass or more, 0.05% by mass or more, 0.10% by mass or more, 0.15% by mass or more, 0.20% by mass or more, 0.25% by mass or more, 0.30% by mass or more, 0.35% by mass or more, 0.40% by mass or more, 0.45% by mass or more, or 0.50% by mass or more, based on the total amount (100% by mass) of the lubricating oil composition, from the viewpoint of providing a lubricating oil composition with improved wear resistance. It may also be 3.00% by mass or less, 2.50% by mass or less, 2.00% by mass or less, 1.50% by mass or less, 1.00% by mass or less, or 0.80% by mass or less.

[0089] In one embodiment of the present invention, the lubricating oil composition does not need to substantially contain a fatty acid polyester of a fatty acid and a polyhydric alcohol. In one embodiment of the present invention, the content of the fatty acid polyester may be less than 0.30% by mass, less than 0.20% by mass, less than 0.10% by mass, less than 0.05% by mass, less than 0.01% by mass, less than 0.001% by mass, or less than 0.0001% by mass, based on the total amount (100% by mass) of the lubricating oil composition.

[0090] [Molybdenum Compounds] In a lubricating oil composition according to one embodiment of the present invention, the content of molybdenum compounds may be limited, or molybdenum compounds may not be included. Examples of molybdenum compounds include molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (MoDTP), and amine salts of molybdic acid. The content of one or more of these may be limited, or one or more of these may not be included. The specific content of organic molybdenum compounds in terms of molybdenum atoms may be less than 50 ppm by mass, less than 30 ppm by mass, less than 20 ppm by mass, less than 10 ppm by mass, or less than 5 ppm by mass, based on the total amount (100% by mass) of the lubricating oil composition.

[0091] [Zinc-based compounds] In a lubricating oil composition according to one embodiment of the present invention, the content of zinc-based compounds may be limited, or the composition may not contain zinc-based compounds. Examples of zinc-based compounds include zinc dithiophosphate (ZnDTP), and the content of ZnDTP may be limited, or the composition may not contain ZnDTP. The specific content of zinc-based compounds in terms of zinc atoms may be less than 50 ppm by mass, less than 30 ppm by mass, less than 20 ppm by mass, less than 10 ppm by mass, or less than 5 ppm by mass, based on the total amount (100% by mass) of the lubricating oil composition.

[0092] [Sulfur-based compounds] In a lubricating oil composition according to one embodiment of the present invention, the content of sulfur-based compounds may be limited, or sulfur-based compounds may not be included. Examples of sulfur-based compounds include, in addition to the above-mentioned sulfur-based antioxidants and zinc dithiophosphate (ZnDTP), thiophosphite esters, thiophosphate esters, thiophosphonic acid esters, and their amine salts or metal salts; sulfurized olefins, dialkyl polysulfides, diarylalkyl polysulfides, diaryl polysulfides; and so on. The content of one or more of these may be limited, or one or more of these may not be included. The specific content of sulfur-based compounds in terms of sulfur atoms may be less than 400 ppm by mass, less than 300 ppm by mass, less than 200 ppm by mass, less than 100 ppm by mass, less than 50 ppm by mass, less than 30 ppm by mass, less than 20 ppm by mass, or less than 10 ppm by mass, based on the total amount (100% by mass) of the lubricating oil composition.

[0093] [N-substituted derivatives of sarcosine] In a lubricating oil composition according to one aspect of the present invention, the composition may not substantially contain N-substituted derivatives of sarcosine. Examples of N-substituted derivatives of sarcosine include compounds in which the hydrogen bonded to the nitrogen atom of sarcosine is substituted with an alkyl group, such as N-oleyl sarcosine, N-lauroyl sarcosine, N-myristoyl sarcosine, and N-palmitoyl sarcosine, and the composition may not contain one or more of these. In a lubricating oil composition according to one aspect of the present invention, the content of the N-substituted derivative of sarcosine may be less than 0.30% by mass, less than 0.20% by mass, less than 0.10% by mass, less than 0.05% by mass, less than 0.01% by mass, less than 0.001% by mass, or less than 0.0001% by mass, based on the total amount (100% by mass) of the lubricating oil composition.

[0094] [Fluorescent Agent] In the lubricatingating oil composition of one embodiment of the present invention, it may not substantially contain a fluorescent agent. Examples of the fluorescent agent include hydrocarbon compounds having a stilbene structure such as p-bis(o-methylstyryl)benzene, styrylbenzene, bisstyryl biphenyl, 1,4-distilbene benzene, etc., and it may not contain one or more of these. In the lubricating oil composition of one embodiment of the present invention, the content of the fluorescent agent may be less than 0.30% by mass, less than 0.20% by mass, less than 0.10% by mass, less than 0.05% by mass, less than 0.01% by mass, less than 0.001% by mass, or less than 0.0001% by mass based on the total amount (100% by mass) of the lubricating oil composition.

[0095] <Method for Producing Lubricating Oil Composition> The method for producing the lubricating oil composition of one embodiment of the present invention is not particularly limited, but from the viewpoint of productivity, it preferably has a step of blending component (B) to (C) and, if necessary, other lubricating oil additives other than component (B) to (C) with component (A). Here, the preferred compounds and blending amounts of components (A) to (C) and the lubricating oil additives are as described above. Also, additives such as viscosity index improvers, pour point depressants, and antifoaming agents are preferably blended in a state dissolved in diluent oil.

[0096] [Properties of Lubricating Oil Composition] The kinematic viscosity at 40 °C of the lubricating oil composition of one embodiment of the present invention is 3.0 mm ２ / s or more, 4.0 mm ２ / s or more, 5.0 mm ２ / s or more, 6. mm ２ / s or more, 6.5 mm ２ / s or more, 7.0 mm ２ / s or more, 7.5 mm ２ / s or more, 8.0 mm ２ / s or more, 8.5 mm ２ / s or more, 9.0 mm ２ / s or more, 9.5 mm ２ / s or more, or 10.0 mm ２ / s or more, and preferably 80.0 mm ２ / s or less, 70.0 mm ２ / s or less, 60.0 mm ２ / s or less, 50.0 mm ２ / s or less, 45.0mm ２ / s or less, 40.0mm ２ / s or less, 35.0mm ２ / s or less, 30.0mm ２ / s or less, 25.0mm ２ / s or less, 20.0mm ２ / s or less, 18.0mm ２ / s or less, or 16.0 mm ２ It is preferable to keep it below / s.

[0097] Furthermore, the viscosity index of component (A) used in one aspect of the present invention is preferably 70 or higher, 80 or higher, 90 or higher, 100 or higher, 110 or higher, 120 or higher, 130 or higher, 140 or higher, 150 or higher, 160 or higher, 170 or higher, or 180 or higher, and may also be 450 or lower, 400 or lower, 350 or lower, 300 or lower, or 250 or lower.

[0098] The phosphorus atom content of a lubricating oil composition according to one aspect of the present invention is, based on the total amount (100% by mass) of the lubricating oil composition, 5 ppm or more, 10 ppm or more, 30 ppm or more, 50 ppm or more, 70 ppm or more, 100 ppm or more, 120 ppm or more, 150 ppm or more, 170 ppm or more, 200 ppm or more, 220 ppm or more, 250 ppm or more, 270 ppm or more, 300 ppm or more, or 320 ppm or more, from the viewpoint of providing a lubricating oil composition that improves frictional properties with rubber, frictional properties between metals, and wear resistance in a well-balanced manner. It may be set to ppm or higher, and from the viewpoint of providing a lubricating oil composition with good resistance to immersion in rubber, it may be set to 2000 ppm or less by mass, 1700 ppm or less by mass, 1500 ppm or less by mass, 1400 ppm or less by mass, 1300 ppm or less by mass, 1200 ppm or less by mass, 1100 ppm or less by mass, 1000 ppm or less by mass, 900 ppm or less by mass, 800 ppm or less by mass, 700 ppm or less by mass, 600 ppm or less by mass, 500 ppm or less by mass, 450 ppm or less by mass, 400 ppm or less by mass, 350 ppm or less by mass, 300 ppm or less by mass, or 280 ppm or less by mass.

[0099] The nitrogen atom content of a lubricating oil composition according to one aspect of the present invention may be 0.001% by mass or more, 0.002% by mass or more, 0.004% by mass or more, 0.006% by mass or more, 0.008% by mass or more, 0.010% by mass or more, 0.012% by mass or more, 0.014% by mass or more, 0.016% by mass or more, 0.018% by mass or more, 0.020% by mass or more, 0.022% by mass or more, or 0.023% by mass or more, based on the total amount (100% by mass) of the lubricating oil composition, or 0.200% by mass or less, 0.150% by mass or less, 0. 120 mass% or less, 0.100 mass% or less, 0.090 mass% or less, 0.080 mass% or less, 0.070 mass% or less, 0.060 mass% or less, 0.050 mass% or less, 0.045 mass% or less, 0.040 mass% or less, 0.035 mass% or less, 0.030 It may be less than or equal to 0.025 mass%, 0.023 mass% or less, 0.021 mass% or less, 0.020 mass% or less, 0.018 mass% or less, 0.016 mass% or less, 0.014 mass% or less, 0.012 mass% or less, or 0.010 mass% or less.

[0100] For a lubricating oil composition according to one embodiment of the present invention, the coefficient of friction μ with respect to rubber, measured using a reciprocating friction tester under the measurement conditions of the examples described later, is preferably 0.16 or less, more preferably 0.15 or less, more preferably 0.14 or less, even more preferably 0.13 or less, even more preferably 0.12 or less, even more preferably 0.11 or less, and particularly preferably 0.10 or less.

[0101] For a lubricating oil composition according to one embodiment of the present invention, the coefficient of friction measured at an oil temperature of 60°C in accordance with the "Sota pendulum test" specified in JASO-M314-88 is preferably 0.140 or less, more preferably 0.135 or less, more preferably 0.130 or less, even more preferably 0.125 or less, even more preferably 0.120 or less, even more preferably 0.115 or less, and particularly preferably 0.110 or less.

[0102] For a lubricating oil composition according to one embodiment of the present invention, the wear mark diameter of a test ball measured in accordance with ASTM D4172-18 under the measurement conditions of the examples described below is preferably 0.51 mm or less, more preferably 0.50 mm or less, more preferably 0.49 mm or less, even more preferably 0.48 mm or less, even more preferably 0.47 mm or less, and particularly preferably 0.46 mm or less.

[0103] [Applications of the Lubricating Oil Composition] A lubricating oil composition according to one preferred embodiment of the present invention can improve the frictional properties and immersion resistance of rubber in a well-balanced manner. A lubricating oil composition according to one embodiment of the present invention having such properties can be suitably applied to the lubrication of various devices, for example, as a shock absorber lubricant, hydraulic fluid, construction machinery operating fluid, power steering oil, turbine oil, compressor oil, machine tool lubricant, cutting fluid, gear oil, fluid bearing oil, rolling bearing oil, etc. Among these, a lubricating oil composition according to one embodiment of the present invention can be suitably applied to shock absorbers. More specifically, a lubricating oil composition according to one embodiment of the present invention can be used in both twin-tube and single-tube shock absorbers, and can be suitably used in shock absorbers for both two-wheeled and four-wheeled vehicles.

[0104] Considering the above-described properties of the lubricating oil composition according to one aspect of the present invention, the present invention may also provide the following [1] and [2]: [1] A buffer filled with the lubricating oil composition according to one aspect of the present invention described above. [2] Use of the lubricating oil composition, applying the lubricating oil composition according to one aspect of the present invention described above to the buffer. Preferred embodiments of the lubricating oil composition described in [1] and [2] above are as described above.

[0105] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited in any way by these examples. The methods for measuring various physical properties are as follows.

[0106] (1) Kinematic viscosity and viscosity index were measured and calculated in accordance with JIS K2283:2000. (2) Nitrogen atom content was measured in accordance with JIS K2609. (3) Weight-average molecular weight (Mw) was measured using a gel permeation chromatograph (Agilent, "1260 HPLC") under the following conditions, and the value measured on a standard polystyrene basis was used. (Measurement conditions) ・Column: Two "Shodex LF404" columns linked in sequence. ・Column temperature: 35℃ ・Developing solvent: Chloroform ・Flow rate: 0.3 mL / min (4) Phosphorus, molybdenum, zinc, calcium, magnesium, and sodium atom content was measured in accordance with JPI-5S-38-92. (5) Sulfur atom content was measured in accordance with JIS K2541-6:2013. (6) Base number (perchloric acid method) Measured in accordance with JIS K2501:2003 (perchloric acid method).

[0107] Examples 1-5 and Comparative Examples 1-7: Lubricating oil compositions were prepared by adding the types of base oils and various additives shown in Tables 1 and 2 in the amounts shown in each table and mixing them thoroughly. Details of each component used in the preparation of the lubricating oil compositions are as follows.

[0108] <Components (A): Base Oil> ・"Mineral Oil": 60N mineral oil classified as Group II of the API base oil category, kinematic viscosity at 40°C = 7.11 mm ２ / s, viscosity index = 109. <Component (B1): Amide compound> - "Amide compound (b-1)": Reaction product of tetraethylenepentamine and isostearic acid. R in the above general formula (b1-1) Ｂ１ is a 15-methylhexadecyl group (-C １７ H ３５ ), R Ｂ２A compound in which is a hydrogen atom, X is a hydrogen atom, b1 is 2, b2 is 4, nitrogen atom content = 6.2 mass%. <Component (B2): Imide compound> - "Imide compound (b-2)": Non-boron modified succinate bisimide having a polybutenyl group with Mw = 960, nitrogen atom content = 1.8 mass%. <Other basic compounds> - "Tertiary amine (1)": Monobutylphenylmonoctylphenylamine. - "Tertiary amine (2)": Triethanolamine. <Component (C): Phosphite ester> - "Phosphite ester (C12)": Dilauryl hydrogen phosphite. R in the above general formula (c-1) Ｃ１ and R Ｃ２ A compound in which is a lauryl group (C12 alkyl group), phosphorus atom content = 6.8% by mass. • "Phosphite ester (C18)": Dioleyl hydrogen phosphite. R in the above general formula (c-1) Ｃ１ and R Ｃ２ Compounds with an oleyl group (C18 alkenyl group), phosphorus atom content = 5.1% by mass. <Other phosphorus compounds> - "Phosphite ester (C8)": Di(2-ethylhexyl) phosphonic acid. Phosphorus atom content = 10.0% by mass. - "Acidic phosphate ester amine salt": A mixture of diC12-14-t-alkylamine methyl phosphate salt and monoC12-14-t-alkylamine dimethyl phosphate salt. Phosphorus atom content = 9.5% by mass. - "Neutral phosphate ester": Tricresyl phosphate. Phosphorus atom content = 8.4% by mass. <Other additives> - "PMA": Polymethacrylate with Mw 190,000. - "Fatty acid monoester": Sorbitan monooleate.

[0109] Furthermore, the content of molybdenum atoms, zinc atoms, calcium atoms, magnesium atoms, and sodium atoms in the prepared lubricating oil compositions was less than 5 ppm by mass each, and the content of sulfur atoms was less than 10 ppm by mass. In addition, none of the prepared lubricating oil compositions substantially contained primary amines, diamines, N-substituted derivatives of sarcosine, fluorescent agents, or fatty acid polyesters of fatty acids and polyhydric alcohols, with each content being less than 0.0001% by mass.

[0110] The kinematic viscosity, viscosity index, and base number derived from component (B), base number derived from components other than component (B), and base number of the lubricating oil composition were measured or calculated for the prepared lubricating oil composition, and the following tests were performed. These results are shown in Tables 1 and 2.

[0111] (1) Friction Test for Rubber The coefficient of friction μ for rubber was measured using a reciprocating friction tester under the following test conditions. The rubber (NBR) was prepared by cutting a rubber plate into a circle with a diameter of 15 mm and extruding it with a ball with a diameter of 12.7 mm. A few drops of the lubricating oil composition prepared in the examples and comparative examples were placed on the plate, and after a break-in run of 2 minutes at an amplitude of ±2 mm and a frequency of 1 Hz, the test was performed. Temperature: 40°C Frequency: 1 Hz Amplitude: ±2 mm Test piece: NBR / chrome plated plate (50 × 1000 × 5 mm) Load: 0.4 kgf

[0112] (2) Soda Pendulum Test In accordance with the "Soda Pendulum Test" specified in JASO-M314-88, the coefficient of friction was measured using a Soda pendulum test machine (Type II) at an oil temperature of 60°C. The smaller the coefficient of friction, the better the frictional properties of the lubricating oil composition.

[0113] (3) Shell Four-Ball Abrasion Test In accordance with ASTM D4172-18, the abrasion mark diameter of the test ball was measured under the following test conditions. The smaller the abrasion mark diameter, the better the abrasion resistance of the lubricant composition. • Test ball: 0.5-inch ball made of SUJ-2, Grade 20 • Oil temperature: 80°C • Rotation speed: 1,200 rpm • Load: 392 N • Test time: 60 minutes

[0114] (4) Immersion Test (U-801) A 2 mm thick, 1 cm square white urethane sheet was immersed in 100 mL of the lubricating oil composition prepared in the Examples and Comparative Examples, and left to stand in a constant temperature bath set to 100°C for 70 hours. After standing, the urethane sheet was removed, the oil was removed, and the appearance was observed. The immersion resistance to rubber was evaluated according to the following criteria. <Evaluation Criteria> ・A: Almost the same as the white color before immersion, with almost no discoloration observed. ・B: Part or the whole discolored to light brown. ・C: Part or the whole discolored to brown or dark brown. As a criterion for each evaluation, the result of Example 1 was set to "B", the result of Example 2 to "A", and the result of Comparative Example 4 to "C", and the degree of discoloration of the other Examples and Comparative Examples was evaluated based on these discolorations.

[0115]

[0116]

[0117] The lubricating oil compositions prepared in Examples 1 to 5 exhibited excellent frictional properties, wear resistance, and resistance to immersion in rubber. Therefore, these lubricating oil compositions can be suitably used for lubricating shock absorbers. On the other hand, the lubricating oil compositions prepared in Comparative Examples 1 to 7 were inferior to those in Examples 1 to 5 in at least one of the following areas: frictional properties, wear resistance, and resistance to immersion in rubber.

Claims

1. A lubricating oil composition comprising a base oil (A), one or more basic compounds (B) selected from amide compounds (B1) and imide compounds (B2), and a phosphorous acid ester (C) having an alkyl group or alkenyl group with 11 or more carbon atoms, wherein the content of component (C) is 0.01 to 1.90% by mass on a basis of the total amount of the lubricating oil composition, and the base number of the lubricating oil composition is 0.05 to 1.30 mgKOH / g, and the lubricating oil composition is used for lubricating buffers.

2. The lubricating oil composition according to claim 1, wherein the content ratio of component (B) to component (C) [(B) / (C)] is 0.20 to 3.50 by mass.

3. The lubricating oil composition according to claim 1 or 2, wherein the content of component (B) is 0.01 to 4.00% by mass on a basis of the total amount of the lubricating oil composition.

4. The lubricating oil composition according to any one of claims 1 to 3, wherein component (B1) is an amide compound (B11) having a hydrocarbon group containing at least one imino structure.

5. The lubricating oil composition according to any one of claims 1 to 4, wherein component (B2) comprises one or more non-boron alkenyl succinimides (B21) selected from non-boron modified alkenyl succinimides and non-boron modified alkenyl succinimides, and one or more boron-modified products (B22) of component (B21).

6. The lubricating oil composition according to any one of claims 1 to 5, wherein the content of acidic phosphate esters and their amine salts is less than 0.10% by mass on a total basis of the lubricating oil composition.

7. The lubricating oil composition according to any one of claims 1 to 6, wherein the content of phosphorous acid ester (CX) having 11 or more C atoms and not having an alkyl group or alkenyl group is less than 0.10% by mass on a basis of the total amount of the lubricating oil composition.

8. The lubricating oil composition according to any one of claims 1 to 7, wherein the content of the molybdenum compound in terms of molybdenum atoms is less than 50 ppm by mass on a total basis of the lubricating oil composition.

9. The lubricating oil composition according to any one of claims 1 to 8, wherein the content of the zinc-based compound, in terms of zinc atoms, is less than 50 ppm by mass on a total basis of the lubricating oil composition.

10. The lubricating oil composition according to any one of claims 1 to 9, wherein the content of sulfur-based compounds in terms of sulfur atoms is less than 400 ppm by mass on a total basis of the lubricating oil composition.

11. The lubricating oil composition according to any one of claims 1 to 10, wherein the content of a metal-based detergent containing a metal atom selected from calcium atoms, magnesium atoms, and sodium atoms, in terms of the amount of said metal atom, is less than 100 ppm by mass on a total basis of the lubricating oil composition.

12. A lubricating oil composition according to any one of claims 1 to 11, which substantially does not contain a primary amine.

13. A lubricating oil composition according to any one of claims 1 to 12, which is substantially free of diamines.

14. A lubricating oil composition according to any one of claims 1 to 13, which substantially does not contain an N-substituted derivative of sarcosine.

15. A lubricating oil composition according to any one of claims 1 to 14, which is substantially free of fluorescent agents.

16. A lubricating oil composition according to any one of claims 1 to 15, which substantially does not contain fatty acid polyesters of fatty acids and polyhydric alcohols.

17. A method for lubricating a shock absorber, comprising using the lubricating oil composition described in any one of claims 1 to 16 for the lubrication of the shock absorber.

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