Lubricating oil composition

Abstract

The present invention addresses the problem of providing a lubricating oil composition that exhibits excellent brake squeal prevention performance and anti-seizure performance. This problem can be solved by a lubricating oil composition that contains: a base oil (A); zinc dithiophosphate (B); and a sarcosine-based compound (C). The content of the sarcosine-based compound (C) is more than 0.05 mass% and not more than 0.40 mass% relative to the total amount of the lubricating oil composition. The composition satisfies requirement (α) or requirement (β). Requirement (α): in a case where the content of the sarcosine-based compound (C) is more than 0.05 mass% and less than 0.20 mass% relative to the total amount of the lubricating oil composition, the composition optionally contains one or more types of phosphorus-based compound (D) selected from the group consisting of an acidic phosphoric acid ester (D1) and an amine salt thereof (D2). Requirement (β): in a case where the content of the sarcosine-based compound (C) is 0.20-0.40 mass% relative to the total amount of the lubricating oil composition, the composition contains the phosphorus-based compound (D) at a quantity of less than 0.50 mass% relative to the total amount of the lubricating oil composition.

Description

[Technical Field]

[0001] This invention relates to a lubricating oil composition. [Background technology]

[0002] Industrial machinery such as agricultural machinery, construction machinery, and transport machinery are typically equipped with transmissions (gears) and hydraulic actuators. Among industrial machinery, agricultural machinery such as tractors, rice transplanters, binders, and combine harvesters; construction machinery such as hydraulic excavators, cranes, and bulldozers; and transport machinery such as dump trucks, forklifts, shovel loaders, and rough-terrain transport vehicles are also equipped with wet brakes. It is common practice for the transmissions (gears), hydraulic actuators, and wet brakes of these machines to be lubricated with the same lubricating oil composition.

[0003] Various lubricating oil compositions for use in such industrial machinery have been proposed. For example, Patent Document 1 proposes a tractor hydraulic fluid composition containing a main amount of oil with lubricating viscosity, a specific detergent composition, a specific amount of at least one hydrocarbyl polyhydric alcohol, and a specific amount of at least one dialkyldithiophosphate zinc having a secondary alkyl group. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Special table number 2017-505852 [Overview of the project] [Problems that the invention aims to solve]

[0005] Incidentally, a problem unique to wet brakes is brake squeal, which is caused by vibrations resulting from the repeated adhesion and slippage between friction surfaces, i.e., stick-slip. Therefore, lubricating oil compositions used in industrial machinery equipped with wet brakes are required to have performance that prevents brake squeal (hereinafter also referred to as "brake squeal prevention performance"). In addition, when the transmission (gears), hydraulic actuation parts, and wet brakes of industrial machinery are lubricated using the same lubricating oil composition, the lubricating oil composition used for this common lubrication must also have the ability to prevent the transmission (gears) from seizing (hereinafter also referred to as "seizure resistance"). However, Patent Document 1 does not address the balance between brake squeal prevention and seizure resistance. While friction modifiers are sometimes added to lubricant compositions to ensure brake squeal prevention, increasing the amount of friction modifier tends to decrease seizure resistance, and conversely, decreasing the amount of friction modifier may result in a loss of brake squeal prevention. Thus, achieving both of these performances simultaneously has been difficult.

[0006] Therefore, the object of the present invention is to provide a lubricating oil composition that is excellent in both brake squeal prevention performance and seizure resistance performance. [Means for solving the problem]

[0007] As a result of diligent research, the inventors have found that a lubricating oil composition containing a base oil, zinc dithiophosphate, and a sarcosine compound, and satisfying specific requirements, can solve the above problem.

[0008] In other words, the present invention relates to the following [1] to [2]. [1] A lubricating oil composition containing a base oil (A), zinc dithiophosphate (B), and a sarcosine compound (C), A lubricating oil composition in which the content of the sarcosine compound (C) is greater than 0.05% by mass and less than or equal to 0.40% by mass on a total basis of the lubricating oil composition, and which satisfies the following requirement (α) or (β). Requirement (α): If the content of the sarcosine compound (C) is greater than 0.05% by mass and less than 0.20% by mass on a total basis of the lubricating oil composition, then the composition optionally contains one or more phosphorus compounds (D) selected from the group consisting of acidic phosphate esters (D1) and their amine salts (D2). Requirement (β): If the content of the sarcosine compound (C) is 0.20% by mass or more and 0.40% by mass or less on a total basis of the lubricating oil composition, the lubricating oil composition contains less than 0.50% by mass of the phosphorus compound (D) on a total basis. [2] A method for lubricating industrial machinery using the lubricating oil composition described in [1] above. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a lubricating oil composition that is excellent in both brake noise prevention performance and seizure resistance performance. [Modes for carrying out the invention]

[0010] The upper and lower limits of the numerical ranges described herein can be combined in any way. For example, if the numerical ranges "A to B" and "C to D" are described, the numerical ranges "A to D" and "C to B" are also included within the scope of the present invention. Furthermore, unless otherwise specified, the numerical range "lower limit to upper limit" described herein means that the value is greater than or equal to the lower limit and less than or equal to the upper limit. Furthermore, in this specification, the numerical values ​​in the examples are values ​​that can be used as upper or lower limits.

[0011] [Aspects of the lubricating oil composition of the present invention] The lubricating oil composition of the present invention contains a base oil (A), zinc dithiophosphate (B), and a sarcosine compound (C). The lubricating oil composition of the present invention has a content of sarcosine compound (C) that is greater than 0.05% by mass and less than or equal to 0.40% by mass on a basis of the total amount of the lubricating oil composition, and satisfies the following requirement (α) or (β). Requirement (α): If the content of the sarcosine compound (C) is greater than 0.05% by mass and less than 0.20% by mass on a total basis of the lubricating oil composition, then the composition optionally contains one or more phosphorus compounds (D) selected from the group consisting of acidic phosphate esters (D1) and their amine salts (D2). Requirement (β): If the content of the sarcosine compound (C) is 0.20% by mass or more and 0.40% by mass or less on a total basis of the lubricating oil composition, the lubricating oil composition contains less than 0.50% by mass of the phosphorus compound (D) on a total basis.

[0012] The inventors diligently conducted research to solve the above problems. As a result, the inventors found that a lubricating oil composition containing a base oil (A), zinc dithiophosphate (B), and a sarcosine compound (C), in which the content of the sarcosine compound (C) is adjusted to a specific range, exhibits excellent brake squeal prevention performance and seizure resistance. Furthermore, the inventors found that by further incorporating one or more phosphorus compounds (D) selected from the group consisting of acidic phosphate esters (D1) and their amine salts (D2) into the above lubricating oil composition, the range of content of the sarcosine compound (C) that provides good brake squeal prevention performance and seizure resistance can be expanded. Based on these findings, the inventors conducted further research and completed the present invention. The mechanism by which the effects of the present invention are achieved can be inferred as follows. Specifically, lubricating oil compositions containing only zinc dithiophosphate (B), or lubricating oil compositions containing only zinc dithiophosphate (B) and a phosphorus-based compound (D), exhibit anti-seizure performance but not brake squeal prevention performance. Therefore, it is inferred that the inclusion of a specific amount of sarcosine-based compound (C) in the lubricating oil composition greatly contributes to the achievement of brake squeal prevention performance. However, if the amount of sarcosine-based compound (C) exceeds a specific amount, the brake squeal prevention performance is no longer achieved. Thus, it has been found that there is an appropriate amount of sarcosine-based compound (C) to be included alone for the purpose of brake squeal prevention performance. On the other hand, if it is necessary to include more sarcosine-based compound than the appropriate amount for various reasons, some kind of countermeasure will be necessary because the brake squeal prevention performance will not be achieved as described above. Through various studies, the inventors have discovered that in such cases, by incorporating a phosphorus-based compound (D), brake squeal prevention performance can be achieved even at concentrations where sarcosine-based compound (C) alone does not exhibit brake squeal prevention performance. The reason why brake squeal prevention performance can be achieved by incorporating a phosphorus-based compound (D), even at concentrations where sarcosine-based compound (C) alone does not exhibit brake squeal prevention performance, is presumed to be due to some kind of interaction between sarcosine-based compound (C) and phosphorus-based compound (D).

[0013] A lubricating oil composition according to one aspect of the present invention may consist only of a base oil (A) (hereinafter also referred to as "component (A)"), zinc dithiophosphate (B) (hereinafter also referred to as "component (B)"), and a sarcosine compound (C) (hereinafter also referred to as "component (C)"), but may further contain a phosphorus compound (D) (hereinafter also referred to as "component (D)") under certain conditions. In other words, a lubricating oil composition according to one aspect of the present invention may consist only of component (A), component (B), and component (C), or it may consist only of component (A), component (B), component (C), and component (D). Furthermore, the lubricating oil composition according to one embodiment of the present invention may further contain other components other than components (A), (B), (C), and (D).

[0014] In a lubricating oil composition according to one embodiment of the present invention, the total content of component (A), component (B), and component (C) is preferably 70% by mass or more, more preferably 75% by mass or more, and even more preferably 80% by mass or more, based on the total amount of the lubricating oil composition. Furthermore, it is preferably 100% by mass or less, more preferably 97% by mass or less, and even more preferably 95% by mass or less. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, they are preferably 70% to 100% by mass, more preferably 75% to 97% by mass, and even more preferably 80% to 95% by mass.

[0015] Furthermore, in a lubricating oil composition according to one embodiment of the present invention, the total content of component (A), component (B), component (C), and component (D) is preferably 70% by mass or more, more preferably 75% by mass or more, and even more preferably 80% by mass or more, based on the total amount of the lubricating oil composition. Also, it is preferably 100% by mass or less, more preferably 97% by mass or less, and even more preferably 95% by mass or less. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, they are preferably 70% to 100% by mass, more preferably 75% to 97% by mass, and even more preferably 80% to 95% by mass.

[0016] The requirements (α) and (β) specified in the lubricating oil composition of the present invention will be described in detail below, followed by a detailed description of each component constituting the lubricating oil composition of the present invention.

[0017] <Requirement (α) and Requirement (β)> The lubricating oil composition of the present invention satisfies requirement (α) or requirement (β). If the lubricating oil composition fails to satisfy either requirement (α) or requirement (β), the effects of the present invention will not be achieved. Requirements (α) and (β) will be explained in detail below.

[0018] (Requirement(α)) In the lubricating oil composition of the present invention, requirement (α) is defined as follows. Requirement (α): If the content of sarcosine compounds (C) is greater than 0.05% by mass and less than 0.20% by mass on a total basis of the lubricating oil composition, then it optionally contains one or more phosphorus compounds (D) selected from the group consisting of acidic phosphate esters (D1) and their amine salts (D2).

[0019] In the lubricating oil composition of the present invention, the content of sarcosine compound (C) is limited to more than 0.05% by mass and 0.40% by mass or less in the total amount of the lubricating oil composition. Requirement (α) specifies the embodiment when the content is more than 0.05% by mass and less than 0.20% by mass within this limit. In other words, if the content of sarcosine compound (C) is greater than 0.05% by mass and less than 0.20% by mass, phosphorus compound (D) may or may not be present. In either case, the effects of the present invention are achieved. Furthermore, if the lubricating oil composition contains phosphorus compound (D) in requirement (α), its content is not limited.

[0020] Furthermore, if requirement (α) does not contain phosphorus-based compound (D), the content of sarcosine-based compound (C) in requirement (α) is preferably 0.07% by mass or more, more preferably 0.08% by mass or more, and even more preferably 0.09% by mass or more, based on the total amount of the lubricating oil composition, from the viewpoint of making it easier to exhibit the effects of the present invention. Also, it is preferably 0.16% by mass or less, more preferably 0.13% by mass or less, and even more preferably 0.11% by mass or less. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, they are preferably 0.07 mass% to 0.16 mass%, more preferably 0.08 mass% to 0.13 mass%, and even more preferably 0.09 mass% to 0.11 mass%. Furthermore, if requirement (α) contains a phosphorus-based compound (D), the content of the sarcosine-based compound (C) in requirement (α) is preferably 0.07% by mass or more, more preferably 0.08% by mass or more, and even more preferably 0.09% by mass or more, based on the total amount of the lubricating oil composition, from the viewpoint of making it easier to exhibit the effects of the present invention. It is also preferably 0.19% by mass or less. The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, they are preferably 0.07 mass% to 0.19 mass%, more preferably 0.08 mass% to 0.19 mass%, and even more preferably 0.09 mass% to 0.19 mass%.

[0021] Herein, if the lubricating oil composition of one aspect of the present invention satisfies requirement (α), it is more preferable, from the viewpoint of making it easier to exhibit the effects of the present invention, to satisfy either requirement (α1) or requirement (α2) described below, and even more preferable, to satisfy both requirements (α1) and requirement (α2) described below.

[0022] -Requirement (α1)- In a lubricating oil composition according to one embodiment of the present invention, requirement (α1) is defined as follows. • Requirement (α1): The ratio of sarcosine compound (C) to zinc dithiophosphate (B) [(C) / (B)] is greater than 0.04 and less than 0.17 by mass. By having [(C) / (B)] within the above range, the effects of the present invention can be more easily realized.

[0023] Here, in the case where requirement (α1) does not contain phosphorus compound (D), [(C) / (B)] is preferably 0.05 or more, more preferably 0.06 or more, and even more preferably 0.07 or more in mass ratio, from the viewpoint of further enhancing the effects of the present invention. Also, it is preferably 0.14 or less, more preferably 0.11 or less, and even more preferably 0.10 or less. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, they are preferably 0.05 to 0.14, more preferably 0.06 to 0.11, and even more preferably 0.07 to 0.10. Furthermore, in the case where requirement (α1) contains a phosphorus compound (D), the mass ratio of [(C) / (B)] is preferably 0.05 or more, more preferably 0.06 or more, and even more preferably 0.07 or more, from the viewpoint of further enhancing the effects of the present invention. It is also preferably 0.16 or less. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, they are preferably 0.05 to 0.16, more preferably 0.06 to 0.16, and even more preferably 0.07 to 0.16.

[0024] -Requirements (α2)- In a lubricating oil composition according to one embodiment of the present invention, requirement (α2) is defined as follows. • Requirement (α2): The ratio of phosphorus-based compounds (D) to zinc dithiophosphate (B) [(D) / (B)] is 1.04 or less by mass. By having [(D) / (B)] within the above range, the effects of the present invention can be more easily realized.

[0025] Here, in requirement (α2), [(D) / (B)] is preferably less than 1.04, more preferably 0.90 or less, even more preferably 0.80 or less, and even more preferably 0.70 or less, in terms of mass ratio, from the viewpoint of facilitating the preparation of a lubricating oil composition with superior seizure resistance. Note that a lubricating oil composition that satisfies requirement (α2) does not necessarily have to contain phosphorus-based compound (D), and therefore, the lower limit of [(D) / (B)] may be 0.00 in terms of mass ratio.

[0026] (Requirements (β)) In the lubricating oil composition of the present invention, requirement (β) is defined as follows. • Requirement (β): If the content of sarcosine compound (C) is 0.20% by mass or more and 0.40% by mass or less on a total basis of the lubricating oil composition, the lubricating oil composition contains less than 0.50% by mass of the phosphorus compound (D).

[0027] In the lubricating oil composition of the present invention, the content of sarcosine compound (C) is limited to more than 0.05% by mass and 0.40% by mass or less in the total amount of the lubricating oil composition. Requirement (β) specifies the embodiment when the content is between 0.20% by mass and 0.40% by mass within this limit. By satisfying this provision, the effects of the present invention are achieved even if the above requirement (α) is not met. Furthermore, requirement (β) requires that the lubricating oil composition must contain a phosphorus-based compound (D). If the lubricating oil composition does not contain a phosphorus-based compound (D) in requirement (β), the effects of the present invention will not be exhibited. However, the content of the phosphorus-based compound (D) is limited to less than 0.50% by mass.

[0028] Here, the content of the sarcosine compound (C) in requirement (β) is preferably less than 0.40% by mass, more preferably 0.35% by mass or less, and even more preferably 0.30% by mass or less, on a total basis of the lubricating oil composition, from the viewpoint of facilitating the preparation of a lubricating oil composition with superior seizure resistance.

[0029] Furthermore, the content of the phosphorus compound (D) in requirement (β) is preferably 0.40% by mass or less, more preferably 0.35% by mass or less, and even more preferably 0.30% by mass or less, from the viewpoint of making it easier to exhibit the effects of the present invention. Also, it is preferably 0.10% by mass or more, more preferably 0.15% by mass or more, and even more preferably 0.20% by mass or more. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, they are preferably 0.10% by mass to 0.40% by mass, more preferably 0.15% by mass to 0.35% by mass, and even more preferably 0.20% by mass to 0.30% by mass.

[0030] Herein, if the lubricating oil composition of one aspect of the present invention satisfies requirement (β), it is more preferable, from the viewpoint of making it easier to exhibit the effects of the present invention, to satisfy either requirement (β1) or requirement (β2) described below, and even more preferable, to satisfy both requirements (β1) and requirement (β2) described below.

[0031] -Requirements (β1)- In a lubricating oil composition according to one embodiment of the present invention, requirement (β1) is defined as follows. • Requirement (β1): The content ratio of the sarcosine compound (C) to the zinc dithiophosphate (B) [(C) / (B)] is 0.33 or less by mass. By having [(C) / (B)] within the above range, the effects of the present invention can be more easily realized.

[0032] Here, in requirement (β1), [(C) / (B)] is preferably less than 0.33, more preferably 0.30 or less, even more preferably 0.27 or less, and even more preferably 0.25 or less, in terms of mass ratio, from the viewpoint of facilitating the preparation of a lubricating oil composition with superior seizure resistance. Furthermore, from the viewpoint of further facilitating the demonstration of the present invention, it is preferably 0.10 or more, more preferably 0.15 or more, and even more preferably 0.17 or more. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, preferably they are 0.10 or more and less than 0.33, more preferably 0.10 to 0.30, even more preferably 0.15 to 0.27, and even more preferably 0.17 to 0.25.

[0033] -Requirements (β2)- In a lubricating oil composition according to one embodiment of the present invention, requirement (β2) is defined as follows. Requirement (β2): The content ratio of the phosphorus compound (D) to the zinc dithiophosphate (B) [(D) / (B)] is less than 0.42 by mass. By having [(D) / (B)] within the above range, the effects of the present invention can be more easily realized.

[0034] Here, in requirement (β2), [(D) / (B)] is preferably 0.35 or less, more preferably 0.30 or less, and even more preferably 0.25 or less in mass ratio, from the viewpoint of making it easier to exhibit the effects of the present invention. Also, it is preferably 0.10 or more, more preferably 0.15 or more, and even more preferably 0.17 or more. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, they are preferably 0.10 to 0.35, more preferably 0.15 to 0.30, and even more preferably 0.17 to 0.25.

[0035] <Base oil (A)> The lubricating oil composition of the present invention contains a base oil (A). As the base oil (A), one or more types selected from mineral oils and synthetic oils that have been conventionally used as base oils for lubricating oils can be used without any particular restrictions.

[0036] Examples of mineral oils include atmospheric residues obtained by atmospheric distillation of crude oils such as paraffinic crude oil, intermediate base crude oil, or naphthenic crude oil; distillates obtained by vacuum distillation of these atmospheric residues; and mineral 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. The mineral oil is preferably a mineral oil classified as Group 2 or 3 in the base oil categories of the American Petroleum Institute (API).

[0037] Examples of synthetic oils include poly-α-olefins such as α-olefin homopolymers and α-olefin copolymers (e.g., α-olefin copolymers with 8 to 14 carbon atoms, such as ethylene-α-olefin copolymers); isoparaffins; various esters such as polyol esters and dibasic acid esters; various ethers such as polyphenyl ethers; polyalkylene glycols; alkylbenzenes; alkylnaphthalenes; and GTL base oils obtained by isomerizing waxes (gas-liquid (GTL) waxes) produced from natural gas by the Fischer-Tropsch process, etc.

[0038] The base oil (A) may be used alone or in combination of two or more kinds of mineral oils, or may be used alone or in combination of two or more kinds of synthetic oils. Further, one or more mineral oils and one or more synthetic oils may be used in combination. Here, in the lubricating oil composition of one aspect of the present invention, it is preferable that the base oil (A) contains a mineral oil. In this case, the content of the mineral oil is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, still more preferably 70% by mass to 100% by mass, even more preferably 80% by mass to 100% by mass, and still even more preferably 90% by mass to 100% by mass, based on the total amount of the base oil (A).

[0039] The kinematic viscosity of the base oil (A) at 100 °C is preferably 1 mm 2 / s or more, more preferably 2 mm 2 / s or more, still more preferably 3 mm 2 / s or more. Further, the kinematic viscosity of the base oil (A) at 100 °C is preferably 25 mm 2 / s or less, more preferably 20 mm 2 / s or less, still more preferably 15 mm 2 / s or less. When the kinematic viscosity of the base oil (A) is within the above range, in addition to the brake squeal prevention performance, it is advantageous from the viewpoint of improving the seizure prevention performance and wear prevention performance of the transmission (gear), viscosity characteristics, and stability against oxidation deterioration. The upper limit value and the lower limit value of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 1 mm 2 / s to 25 mm 2 / s, more preferably 2 mm 2 / s to 20 mm 2 / s, still more preferably 3 mm 2 / s to 25 mm 2 / s.

[0040] The viscosity index of the base oil (A) is preferably 100 or more, more preferably 110 or more, and still more preferably 120 or more. When the viscosity index of the base oil (A) is within the above range, in addition to the brake squeal prevention performance, it is advantageous from the viewpoint of improving the seizure prevention performance and wear prevention performance of the transmission (gear), viscosity characteristics, and stability against oxidation deterioration.

[0041] Furthermore, if the base oil (A) is a mixed base oil containing two or more base oils, it is preferable that the kinematic viscosity at 100°C and viscosity index of the mixed base oil are within the above range.

[0042] In this specification, the kinematic viscosity and viscosity index of base oil (A) at 100°C refer to values ​​measured or calculated in accordance with JIS K 2283:2000.

[0043] (Base oil (A) content) In a lubricating oil composition according to one embodiment of the present invention, the content of the base oil (A) is preferably 95% by mass or less on a total basis of the lubricating oil composition. By setting the content of the base oil (A) to 95% by mass or less, it is possible to ensure sufficient amounts of zinc dithiophosphate (B), sarcosine compounds (C), and phosphorus compounds (D) in the lubricating oil composition, making it easier to exert the effects of the present invention. Furthermore, from the viewpoint of making it easier to exhibit the effects of the present invention, the content of base oil (A) is more preferably 93% by mass or less, and even more preferably 92% by mass or less, on a total basis of the lubricating oil composition. Also, it is preferably 65% ​​by mass or more, more preferably 70% by mass or more, and even more preferably 75% by mass or more. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, they are preferably 65% ​​to 95% by mass, more preferably 70% to 93% by mass, and even more preferably 75% to 92% by mass. Furthermore, as will be described later, a lubricating oil composition according to one aspect of the present invention may contain other additives in addition to a viscosity index improver. These additives may be provided diluted with a diluent oil and may be incorporated into the lubricating oil composition in this diluted state. In such cases, the diluent oil shall also be included in the content of the base oil (A) described above.

[0044] <Zinc dithiophosphate (B)> The lubricating oil composition of the present invention contains zinc dithiophosphate (B). If the lubricating oil composition does not contain zinc dithiophosphate (B), the effects of the present invention (particularly seizure resistance) will not be exhibited. As for zinc dithiophosphate (B), any type that has been widely used as an additive in lubricating oils can be used without any particular restrictions. Zinc dithiophosphate (B) may be used alone or in combination of two or more types.

[0045] In a lubricating oil composition according to one aspect of the present invention, it is preferable to use a compound represented by the following general formula (b-1) as zinc dithiophosphate (B) from the viewpoint of making it easier to exhibit the effects of the present invention.

[0046] [ka]

[0047] In general formula (b-1), R b1 ~R b4 Each of these independently represents a hydrocarbon group. R b1 ~R b4 The hydrocarbon group that can be selected is not particularly limited as long as it is a monovalent hydrocarbon group, and examples of preferred groups include alkyl groups, alkenyl groups, cycloalkyl groups, and aryl groups, with alkyl groups and aryl groups being more preferred, and alkyl groups being even more preferred. In other words, as the zinc dithiophosphate (B) used in a lubricating oil composition according to one embodiment of the present invention, dialkyldithiophosphate zinc and diaryldithiophosphate zinc are more preferred, and dialkyldithiophosphate zinc is even more preferred.

[0048] R b1 ~R b4 The alkyl and alkenyl groups that can be selected may be linear or branched. Also, R b1 ~R b4 If is an alkyl group, zinc dithiophosphate (B) is R b1 ~R b4R may be a primary dialkyldithiophosphate zinc, where R is a primary alkyl group. b1 ~R b4 While a secondary dialkyldithiophosphate zinc, in which is a secondary alkyl group, may be used, it is preferable to use a primary dialkyldithiophosphate zinc from the viewpoint of the stability of zinc dithiophosphate (B).

[0049] Note, R b1 ~R b4 The cycloalkyl and aryl groups that can be selected may be polycyclic groups such as decalyl and naphthyl groups.

[0050] Also, R b1 ~R b4 The monovalent hydrocarbon group that can be selected may have substituents containing oxygen and / or nitrogen atoms, such as hydroxyl groups, carboxyl groups, amino groups, amide groups, nitro groups, and cyano groups, and may be partially substituted with nitrogen atoms, oxygen atoms, halogen atoms, etc.

[0051] Also, R b1 ~R b4 The number of carbon atoms in the hydrocarbon group that can be selected is preferably 1 or more, more preferably 2 or more, and even more preferably 3 or more, when the monovalent hydrocarbon group is an alkyl group, and the upper limit is preferably 24 or less, more preferably 18 or less, and even more preferably 12 or less. When the monovalent hydrocarbon is an alkenyl group, the number of carbon atoms is preferably 2 or more, more preferably 3 or more, with an upper limit of preferably 24 or less, more preferably 18 or less, and even more preferably 12 or less. When the monovalent hydrocarbon is a cycloalkyl group, the number of carbon atoms is preferably 5 or more, and preferably 20 or less as the upper limit. When the monovalent hydrocarbon is an aryl group, the number of carbon atoms is preferably 6 or more, and preferably 20 or less as the upper limit.

[0052] The compounds represented by the following general formula (b-1) may be used individually or in combination of two or more.

[0053] (Zinc dithiophosphate (B) content) In a lubricating oil composition according to one embodiment of the present invention, the content of zinc dithiophosphate (B) is preferably 0.50% by mass or more, more preferably 0.80% by mass or more, even more preferably 1.00% by mass or more, and even more preferably 1.10% by mass or more, based on the total amount of the lubricating oil composition, from the viewpoint of facilitating the exertion of the effects of the present invention. Furthermore, it is preferably 2.00% by mass or less, more preferably 1.60% by mass or less, even more preferably 1.40% by mass or less, and even more preferably 1.30% by mass or less. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, preferably 0.50% to 2.00% by mass, more preferably 0.80% to 1.60% by mass, even more preferably 1.00% to 1.40% by mass, and even more preferably 1.10% to 1.30% by mass.

[0054] <Sarcosine compounds (C)> The lubricating oil composition of the present invention contains a sarcosine compound (C). The lubricating oil composition of the present invention contains a sarcosine compound (C) and satisfies either requirement (α) or requirement (β) described later, thereby exhibiting excellent brake squeal prevention performance and seizure resistance. If the lubricating oil composition does not contain a sarcosine compound (C), the effects of the present invention (particularly brake squeal prevention performance) will not be exhibited. Furthermore, the sarcosine compound (C) may be used alone or in combination of two or more types.

[0055] In a lubricating oil composition according to one aspect of the present invention, it is preferable to use a sarcosine compound (C1) represented by the following general formula (c-1) as the sarcosine compound (C) from the viewpoint of making it easier to exhibit the effects of the present invention.

[0056] [ka]

[0057] In the above general formula (c-1), R c1 R represents a hydrocarbon group having 2 to 30 carbon atoms, which may contain heteroatoms. c2 This represents a hydrogen atom or a methyl group.

[0058] R c1 The hydrocarbon groups that can be selected are not particularly limited as long as they are monovalent hydrocarbon groups, and examples include C2-C30 alkyl groups, C3-C30 cycloalkyl groups, and C3-C30 alkenyl groups. These monovalent hydrocarbon groups may contain heteroatoms. Specifically, they may have substituents containing oxygen and / or nitrogen atoms, such as hydroxyl groups, carboxyl groups, amino groups, amide groups, nitro groups, and cyano groups, and may be partially substituted with nitrogen atoms, oxygen atoms, halogen atoms, etc.

[0059] R c1 The number of carbon atoms in the hydrocarbon group that can be selected is preferably 8 to 26, more preferably 12 to 24, and even more preferably 16 to 20. c1 Preferably, the alkyl and alkenyl groups may have substituents, and more preferably, the alkenyl groups may have substituents.

[0060] R c1 Examples of alkyl groups that may have substituents and can be selected include ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, hexadecyl group, octadecyl group, tetracosyl group, and hexacosyl group. The alkyl group may be a linear alkyl group or a branched alkyl group. R c1 Examples of optionally substituted cycloalkyl groups that can be selected include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, and adamantyl groups. The cycloalkyl group may be substituted with an alkyl group having 1 to 10 carbon atoms (preferably 1 to 4 carbon atoms). R c1 Examples of optional alkenyl groups that may have substituents include propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, hexadecenyl, octadecenyl, tetracocenyl, and hexacocenyl groups. The alkenyl group may be a linear alkenyl group or a branched alkenyl group.

[0061] Furthermore, the sarcosine compound (C1) may be used alone or in combination of two or more types.

[0062] Herein, in a lubricating oil composition according to one aspect of the present invention, it is more preferable to use a sarcosine compound (C2) represented by the following general formula (c-2) as the sarcosine compound (C1) in order to further enhance the effects of the present invention.

[0063] [ka] [In general formula (c-2), R C3 This indicates a hydrocarbon group with 1 to 29 carbon atoms.

[0064] R c3 There are no particular restrictions on the hydrocarbon groups that can be selected as such, as long as they are monovalent hydrocarbon groups. Examples include alkyl groups having 1 to 29 carbon atoms, cycloalkyl groups having 3 to 29 carbon atoms, and alkenyl groups having 3 to 29 carbon atoms.

[0065] R c3 The number of carbon atoms in the hydrocarbon group that can be selected is preferably 7 to 25, more preferably 11 to 23, and even more preferably 15 to 19. c3 The alkyl group and alkenyl group are preferred, and the alkenyl group is more preferred.

[0066] R c3The alkyl, cycloalkyl, and alkenyl groups that can be selected as R are c1 Similar groups to those exemplified above can be cited.

[0067] A preferred specific example of the sarcosine compound (C2) represented by the above general formula (c-2) is N-oleoyl sarcosine (R c3 Examples include alkenyl groups with 17 carbon atoms.

[0068] Furthermore, sarcosine compounds (C2) may be used individually or in combination of two or more.

[0069] (Content of sarcosine compounds (C)) In the lubricating oil composition of the present invention, the content of sarcosine compound (C) is greater than 0.05% by mass and less than or equal to 0.40% by mass, based on the total amount of the lubricating oil composition. If the content of sarcosine compounds (C) is 0.05% by mass or less, it is not possible to achieve good brake squeal prevention performance. Furthermore, if the content of sarcosine compounds (C) exceeds 0.40% by mass, good seizure resistance cannot be achieved.

[0070] Here, from the viewpoint of easily achieving good brake squeal prevention performance, the content of sarcosine compound (C) is preferably 0.07% by mass or more, more preferably 0.08% by mass or more, even more preferably 0.09% by mass or more, and even more preferably 0.10% by mass or more, based on the total amount of the lubricating oil composition. Furthermore, from the viewpoint of providing good seizure resistance, the content of sarcosine-based compound (C) is preferably less than 0.40% by mass, more preferably 0.35% by mass or less, and even more preferably 0.30% by mass or less, based on the total amount of the lubricating oil composition. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, preferably they are 0.07% by mass or more and less than 0.40% by mass, more preferably 0.08% by mass or more and less than 0.40% by mass, even more preferably 0.09% by mass to 0.35% by mass, and even more preferably 0.10% by mass to 0.30% by mass.

[0071] <Phosphorus compounds (D)> The lubricating oil composition of the present invention optionally contains one or more phosphorus compounds (D) selected from the group consisting of acidic phosphate esters (D1) and their amine salts (D2), provided that the above requirement (α) is met. Furthermore, the lubricating oil composition of the present invention contains the phosphorus-based compound (D) if the above requirement (β) is met. As described above, by incorporating one or more phosphorus compounds (D) selected from the group consisting of acidic phosphate esters (D1) and their amine salts (D2) into the lubricating oil composition, the range of content of sarcosine compounds (C) that provide good brake squeal prevention and seizure resistance can be expanded. In other words, in the range of sarcosine compound (C) content from 0.20% by mass to 0.40% by mass as defined in requirement (β) above, sarcosine compound (C) alone cannot provide good brake squeal prevention and seizure resistance. However, by incorporating a specific amount of phosphorus compound (D) when the sarcosine compound (C) content is within this range, both brake squeal prevention and seizure resistance can be improved. Note that phosphorus compounds (D) do not include zinc dithiophosphate (B).

[0072] In a lubricating oil composition according to one aspect of the present invention, as the acidic phosphate ester (D1) used as the phosphorus-based compound (D), it is preferable to use a compound represented by the following general formula (d-1) from the viewpoint of making it easier to exhibit the effects of the present invention.

[0073] [ka]

[0074] In the above general formula (d-1), R d1 Each of these independently represents a hydrocarbon group having 1 to 30 carbon atoms. From the viewpoint of obtaining better wear resistance, alkyl groups, alkenyl groups, aryl groups, arylalkyl groups, etc., are preferred as hydrocarbon groups.

[0075] R d1 When the alkyl group is used, the number of carbon atoms is preferably 2 to 20, considering factors such as obtaining better wear resistance and ease of availability. The alkyl group may be linear, branched, or cyclic, but linear and branched are preferred, considering factors such as ease of availability. R d1 When the group is an alkenyl group, the number of carbon atoms is preferably 2 to 20, taking into consideration factors such as obtaining better wear resistance and ease of availability. The alkenyl group may be linear, branched, or cyclic, but linear and branched are preferred.

[0076] R d1 When the group is an aryl group, the number of carbon atoms is preferably 6 to 20, more preferably 6 to 15, from the viewpoint of obtaining better seizure resistance and wear resistance, as well as ease of availability. R d1 When the carbon atom is an arylalkyl group, the carbon number is preferably 6 to 20, more preferably 6 to 15, from the viewpoint of obtaining better seizure resistance and wear resistance, as well as ease of availability.

[0077] Furthermore, in the above general formula (d-1), m represents either 1 or 2. If m=2, then multiple R d1 They may be the same, or they may be different from one another.

[0078] Examples of acidic phosphate esters represented by the above general formula (d-1) include mono(di)ethyl acid phosphate, mono(di)n-propyl acid phosphate, mono(di)2-ethylhexyl acid phosphate, mono(di)butyl acid phosphate, mono(di)octyl acid phosphate, mono(di)dodecyl acid phosphate, mono(di)oleyl acid phosphate, mono(di)isodecyl acid phosphate, mono(di)lauryl acid phosphate, mono(di)stearyl acid phosphate, and mono(di)isostearyl acid phosphate.

[0079] The compound represented by general formula (d-1) may be used individually or in combination of two or more types.

[0080] Furthermore, as the amine salt (D2) of the acidic phosphate ester, an amine salt formed from the above-mentioned acidic phosphate ester (D1) and an amine is preferred. Here, examples of amines used in the formation of the amine salt include primary amines, secondary amines, tertiary amines, polyalkylene amines, etc., and examples of primary amines, secondary amines, and tertiary amines include amines represented by the following general formula (d-2).

[0081] [ka]

[0082] In general formula (d-2), R d2 This represents a hydrocarbon group having 1 to 30 carbon atoms. If the hydrocarbon group is an alkyl group, it may be a hydroxyalkyl group in which at least one of the hydrogen atoms of the alkyl group is substituted with a hydroxyl group. R d2 Preferably, the C6-C18 alkyl group, C6-C18 alkenyl group, ring-forming C6-C18 aryl group, C7-C18 arylalkyl group, or C6-C18 hydroxyalkyl group is preferred, and among these, the C6-C18 alkyl group is more preferred. Furthermore, n can be 1, 2, or 3. When n is 1, it is a primary amine; when n is 2, it is a secondary amine; and when n is 3, it is a tertiary amine.

[0083] Examples of polyalkyleneamines include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, heptaethyleneoctamine, tetrapropylenepentamine, and hexasubtileneheptamine.

[0084] The amine salt of the above-mentioned acidic phosphate ester (D1) and the amine or polyamine represented by the above-mentioned general formula (d-2) may be used individually or in combination of two or more types.

[0085] (Content of phosphorus compounds (D)) In a lubricating oil composition according to one embodiment of the present invention, when requirement (α) is met, the content of the phosphorus compound (D) is preferably 0.05% by mass or more, more preferably 0.10% by mass or more, and even more preferably 0.13% by mass or more, based on the total amount of the lubricating oil composition, from the viewpoint of making it easier to exhibit the effects of the present invention. Furthermore, it is preferably 1.25% by mass or less, more preferably less than 1.25% by mass, and even more preferably 1.00% by mass or less. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, preferably they are 0.05% by mass or more and 1.25% by mass or less, more preferably 0.10% by mass or more and less than 1.25% by mass, and even more preferably 0.13% by mass or more and 1.00% by mass or less.

[0086] Furthermore, in a lubricating oil composition according to one embodiment of the present invention, if requirement (β) is satisfied, the content of phosphorus-based compound (D) is as specified in requirement (β), and the preferred range is the same as the preferred range described in requirement (β).

[0087] <Other requirements> In a lubricating oil composition according to one embodiment of the present invention, when requirement (α) is met, the content ratio of phosphorus-based compound (D) to sarcosine-based compound (C) [(D) / (C)] is preferably greater than 0.50, more preferably 1.10 or more, and even more preferably 1.30 or more, in terms of mass ratio, from the viewpoint of making it easier to exhibit the effects of the present invention. Also, it is preferably 12.5 or less, more preferably less than 12.5, and even more preferably 10.0 or less. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, they are preferably 0.50 or more and 12.5 or less, more preferably 1.10 or more and less than 12.5, and even more preferably 1.30 or more and 10.0 or less.

[0088] Furthermore, in a lubricating oil composition according to one embodiment of the present invention, when requirement (β) is satisfied, the content ratio of phosphorus-based compound (D) to sarcosine-based compound (C) [(D) / (C)] is preferably 0.40 or more, more preferably 0.50 or more, even more preferably 0.55 or more, even more preferably 0.65 or more, and still more preferably 0.70 or more, in terms of mass ratio, from the viewpoint of making it easier to exhibit the effects of the present invention. Also, it is preferably less than 1.67, more preferably 1.40 or less, and even more preferably 1.30 or less. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, preferably they are 0.40 or more and less than 1.67, more preferably 0.50 or more and 1.40 or less, even more preferably 0.55 or more and 1.30 or less, even more preferably 0.65 or more and 1.30 or less, and still more preferably 0.70 or more and 1.30 or less.

[0089] <Other additives> A lubricating oil composition according to one aspect of the present invention may contain additives other than the above-mentioned components (A) to (D) (hereinafter also referred to as "other additives"), to the extent that they do not significantly impair the effects of the present invention. Other additives include antioxidants, friction modifiers, lubricity agents, corrosion inhibitors (metal deactivators), detergents, dispersants, viscosity index improvers, pour point depressants, defoamers, rust inhibitors, and extreme pressure agents. These additives may be used individually or in combination of two or more.

[0090] The total content of other additives is preferably 0% by mass or more and 25% by mass or less, more preferably 0% by mass or more and 20% by mass or less, and even more preferably 0% by mass or more and 16% by mass or less, based on the total amount of the lubricating oil composition.

[0091] (Antioxidant) Examples of antioxidants include monoalkyldiphenylamines having alkyl groups with approximately 3 to 10 carbon atoms, such as mono-t-butyldiphenylamine; dialkyldiphenylamines having approximately 3 to 10 carbon atoms in each alkyl group, such as 4,4'-dibutyldiphenylamine; polyalkyldiphenylamines having three or more alkyl groups, each alkyl group having approximately 1 to 10 carbon atoms, such as tetrabutyldiphenylamine; and alkyl-substituted phenyl-α-naphthylamines and phenyl-α-naphthylamines having at least one alkyl group with approximately 1 to 12 carbon atoms, such as methylphenyl-α-naphthylamine. Examples of antioxidants include amine-based antioxidants such as phenyl-α-naphthylamines such as amines; monohindered amine-based antioxidants such as 2,2,6,6-tetramethylpiperidinyl methacrylate; bisphenol-based antioxidants such as 4,4'-methylenebis(2,6-di-t-butylphenol)bis(3-methyl-4-hydroxy-5-t-butylbenzyl) sulfide; and phenol-based antioxidants such as monophenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol and n-octadecyl-3-(4-hydroxy-3,5-di-t-butylphenyl)propionate. These may be used individually or in combination of two or more types.

[0092] (Friction modifier) Examples of friction modifiers include ashless friction modifiers such as aliphatic amines, fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols, and aliphatic ethers, which have at least one alkyl or alkenyl group with 6 to 30 carbon atoms in their molecule. These may be used individually or in combination of two or more types.

[0093] (Oily-based agent) Examples of oily agents include aliphatic alcohols; fatty acid compounds such as fatty acids and fatty acid metal salts; ester compounds such as polyol esters, sorbitan esters, and glycerides; and amine compounds such as aliphatic amines. These may be used individually or in combination of two or more types.

[0094] (Corrosion inhibitor (metal deactivator)) Examples of corrosion inhibitors (metal deactivators) include benzotriazole compounds, tolyltriazole compounds, imidazole compounds, and pyrimidine compounds. These may be used individually or in combination of two or more types.

[0095] (cleaning agent) Examples of cleaning agents include salicylates of sodium, calcium, and magnesium, as well as metal-based cleaning agents such as sulfonates and phenates. These may be used individually or in combination of two or more types.

[0096] (Dispersant) Examples of dispersants include ashless dispersants such as boron-free succinimides, boron-containing succinimides, benzylamines, boron-containing benzylamines, succinic acid esters, and monovalent or divalent carboxylic acid amides represented by fatty acids or succinic acid. These may be used individually or in combination of two or more types.

[0097] (Viscosity index improver) Examples of viscosity index improvers include non-dispersible polymethacrylate (PMA), dispersed polymethacrylate, olefin copolymers (olefin copolymers (OCP); for example, ethylene-propylene copolymers, etc.), dispersed olefin copolymers, and styrene copolymers (for example, styrene-diene hydrogenated copolymers, etc.). These may be used individually or in combination of two or more types. Here, it is preferable to use non-dispersive polymethacrylate (PMA) as the viscosity index improver. Furthermore, as non-dispersive polymethacrylate (PMA), it is preferable to use a combination of two or more types with different mass-average molecular weights (Mw), preferably within the range of 10,000 to 300,000. The mass-average molecular weight (Mw) of the viscosity index improver was measured by gel permeation chromatography and calculated using the polystyrene equivalent.

[0098] (Pour point depressant) Examples of polymers that can be used as pour point depressants include ethylene-vinyl acetate copolymers, condensates of chlorinated paraffin and naphthalene, condensates of chlorinated paraffin and phenol, polymethacrylates, and polyalkylstyrenes. The weight-average molecular weight (Mw) of these polymers is preferably 50,000 to 150,000.

[0099] (Antifoaming agent) Examples of defoaming agents include silicone-based defoaming agents such as silicone oil and fluorosilicone oil, and fluorine-based defoaming agents such as fluoroalkyl ethers. These may be used individually or in combination of two or more types.

[0100] (Rust inhibitor) Examples of rust inhibitors include petroleum sulfonates, alkylbenzene sulfonates, dinonyl naphthalene sulfonates, alkenyl succinate esters, and polyhydric alcohol esters. These may be used individually or in combination of two or more types.

[0101] (Extreme pressure agent) Examples of extreme pressure agents include sulfur-based extreme pressure agents such as sulfurized olefins, hydrocarbyl sulfides, sulfurized oils and fats, sulfurized fatty acids, and sulfurized esters; phosphorus-based extreme pressure agents other than phosphorus compounds (D), such as phosphate esters, phosphite esters, hydrogen phosphite esters, and amine salts of said phosphate ester compounds; and extreme pressure agents containing sulfur atoms and phosphorus atoms, such as monothiophosphate esters, dithiophosphate esters, trithiophosphate esters, amine bases of monothiophosphate esters, amine salts of dithiophosphate esters, monothiophosphite esters, dithiophosphite esters, and trithiophosphite esters. These may be used individually or in combination of two or more types. However, from the viewpoint of maximizing the effect of adding phosphorus compound (D), it is preferable that the content of one or more extreme pressure agents selected from phosphorus extreme pressure agents other than phosphorus compound (D) and extreme pressure agents containing sulfur atoms and phosphorus atoms is kept to a minimum. Specifically, the content of phosphorus-based extreme pressure agents other than phosphorus-based compound (D) and extreme pressure agents containing sulfur atoms and phosphorus atoms is preferably less than 0.01% by mass, more preferably less than 0.005% by mass, and even more preferably less than 0.001% by mass, and even more preferably none of these extreme pressure agents or both are present.

[0102] [Physical properties of lubricating oil compositions] <40℃ kinematic viscosity, 100℃ kinematic viscosity, viscosity index> A lubricating oil composition according to one aspect of the present invention has a kinematic viscosity at 40°C, preferably 10 mm². 2 / s or more, more preferably 20 mm 2 / s or more, more preferably 30mm 2 The value is 1 / s or more, and preferably 70 mm 2 / s or less, more preferably 60mm 2 / s or less, more preferably 50mm 2 It is less than or equal to / s. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, 10 mm is preferred. 2 / s or more 70mm 2 / s or less, more preferably 20mm 2 / s or more 60mm 2 / s or less, more preferably 30mm 2 / s or more 50mm 2 It is less than or equal to / s. Furthermore, the lubricating oil composition according to one embodiment of the present invention has a kinematic viscosity at 100°C, preferably 5.0 mm. 2 / s or more, more preferably 6.0 mm 2 / s or more, more preferably 6.5 mm 2 / s or more, more preferably 7.0 mm 2 The value is 1 / s or more, and preferably 11 mm 2 / s or less, more preferably 10mm 2 / s or less, more preferably 9.0 mm 2 It is less than or equal to / s. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, 5.0 mm is preferred. 2 / s or more 11mm 2 / s or less, more preferably 6.0 mm 2 / s or more 10mm 2 / s or less, more preferably 6.5 mm 2 / s or more 9.0mm 2 / s or less, more preferably 7.0 mm 2 / s or more 9.0mm 2 It is less than or equal to / s. Furthermore, the lubricating oil composition according to one embodiment of the present invention has a viscosity index of preferably 180 or higher, more preferably 190 or higher, and even more preferably 200 or higher. When the kinematic viscosity and viscosity index of the lubricating oil composition are within the above range, it becomes easier to improve wear prevention performance and viscosity characteristics, as well as brake squeal prevention performance and seizure resistance. The methods for measuring the kinematic viscosity at 40°C, kinematic viscosity at 100°C, and viscosity index of the lubricating oil composition are the same as those for base oil (A) described above.

[0103] <base value> A lubricating oil composition according to one embodiment of the present invention has a base number of preferably 4 mg KOH / g or more, preferably 5 mg KOH / g or more, and preferably 6 mg KOH / g or more. It is also typically 12 mg KOH / g or less. Having a base number within the above range of the lubricating oil composition is advantageous in terms of improving detergency, dispersibility, and stability against oxidative degradation. The base number of the lubricating oil composition is a value measured by the potentiometric method (hydrochloric acid method) in accordance with JIS K2501:2003.

[0104] <Various atomic contents> In one embodiment of the present invention, the lubricating oil composition preferably has the following atom content ranges, from the viewpoint of making it easier to exhibit the effects of the present invention. The content of calcium atoms, phosphorus atoms, zinc atoms, and sulfur atoms in the lubricating oil composition is measured according to JIS-5S-38-03. Furthermore, the nitrogen atom content in the lubricating oil composition is a value measured in accordance with JIS K2609:1998.

[0105] (Calcium atom content) In one embodiment of the present invention, the lubricating oil composition has a calcium atom content of preferably 5,000 ppm by mass or less, more preferably 4,500 ppm by mass or less, and even more preferably 4,200 ppm by mass or less, based on the total amount of the lubricating oil composition. Furthermore, it is preferably 2,500 ppm by mass or more, more preferably 3,000 ppm by mass or more, and even more preferably 3,500 ppm by mass or more. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, preferably, they are 2,500 ppm by mass or more and 5,000 ppm by mass or less, more preferably 3,000 ppm by mass or more and 4,500 ppm by mass or less, and even more preferably 3,500 ppm by mass or more and 4,200 ppm by mass or less.

[0106] (Phosphorus atom content) In one embodiment of the present invention, the lubricating oil composition has a phosphorus atom content of preferably 2,000 ppm by mass or less, more preferably 1,500 ppm by mass or less, and even more preferably 1,300 ppm by mass or less, based on the total amount of the lubricating oil composition. Furthermore, it is preferably 500 ppm by mass or more, more preferably 700 ppm by mass or more, and even more preferably 800 ppm by mass or more. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, preferably, they are 500 ppm by mass or more and 2,000 ppm by mass or less, more preferably 700 ppm by mass or more and 1,500 ppm by mass or less, and even more preferably 800 ppm by mass or more and 1,300 ppm by mass or less.

[0107] (Zinc atom content) In one embodiment of the present invention, the lubricating oil composition has a zinc atom content of preferably 2,000 ppm by mass or less, more preferably 1,500 ppm by mass or less, and even more preferably 1,200 ppm by mass or less, based on the total amount of the lubricating oil composition. Furthermore, it is preferably 500 ppm by mass or more, more preferably 800 ppm by mass or more, and even more preferably 1,000 ppm by mass or more. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, preferably, they are 500 ppm by mass or more and 2,000 ppm by mass or less, more preferably 800 ppm by mass or more and 1,500 ppm by mass or less, and even more preferably 1,000 ppm by mass or more and 1,200 ppm by mass or less.

[0108] (Sulfur atom content) In one embodiment of the present invention, the lubricating oil composition has a sulfur atom content of preferably 0.30% by mass or less, more preferably 0.25% by mass or less, and even more preferably 0.23% by mass or less, based on the total amount of the lubricating oil composition. Furthermore, it is preferably 0.10% by mass or more, more preferably 0.15% by mass or more, and even more preferably 0.20% by mass or more. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, preferably they are 0.10% by mass or more and 0.30% by mass or less, more preferably 0.15% by mass or more and 0.25% by mass or less, and even more preferably 0.20% by mass or more and 0.23% by mass or less.

[0109] (Nitrogen atom content) In one embodiment of the present invention, the lubricating oil composition has a nitrogen atom content of preferably 1,200 ppm by mass or less, more preferably 900 ppm by mass or less, and even more preferably 700 ppm by mass or less, based on the total amount of the lubricating oil composition. Furthermore, it is preferably 250 ppm by mass or more, more preferably 300 ppm by mass or more, and even more preferably 350 ppm by mass or more. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, preferably, they are 250 ppm by mass or more and 1,200 ppm by mass or less, more preferably 300 ppm by mass or more and 900 ppm by mass or less, and even more preferably 350 ppm by mass or more and 700 ppm by mass or less.

[0110] < coefficient of friction μ 50 > The lubricating oil composition according to one aspect of the present invention has a friction coefficient μ at 80°C, measured using a low-speed sliding friction tester (LVFA tester) in accordance with JASO M 349:2012, under the conditions of the examples described later. 50 However, it is preferably less than 0.115, more preferably 0.114 or less, even more preferably 0.113 or less, even more preferably 0.112 or less, and still more preferably 0.111 or less.

[0111] <Load-bearing capacity> A lubricating oil composition according to one embodiment of the present invention has a load-bearing capacity (seizure resistance) measured under the conditions of the examples described later, preferably greater than 0.50 MPa, more preferably greater than 0.55 MPa, even more preferably greater than 0.55 MPa, and even more preferably greater than 0.60 MPa.

[0112] [Method for producing a lubricating oil composition] The method for producing the lubricating oil composition of the present invention is not particularly limited, but examples include the production method described below. In other words, the method for producing a lubricating oil composition comprises a step (S1) of blending a base oil (A), zinc dithiophosphate (B), and a sarcosine-based compound (C). A method for producing a lubricating oil composition is provided, wherein the content of the sarcosine compound (C) is greater than 0.05% by mass and less than or equal to 0.40% by mass on a total basis of the lubricating oil composition, and is adjusted to satisfy the following requirement (α) or (β). • Requirement (S1α): When the amount of the sarcosine compound (C) is adjusted to more than 0.05% by mass and less than 0.20% by mass on a basis of the total amount of the lubricating oil composition, one or more phosphorus compounds (D) selected from the group consisting of acidic phosphate esters (D1) and their amine salts (D2) may be optionally added. • Requirement (S1β): When the amount of the sarcosine compound (C) is adjusted to 0.20% by mass or more and 0.40% by mass or less on a total basis of the lubricating oil composition, the phosphorus compound (D) is blended in an amount of less than 0.50% by mass on a total basis of the lubricating oil composition. There are no particular restrictions on the order in which the above components are blended. For example, the base oil (A), zinc dithiophosphate (B), sarcosine compound (C), phosphorus compound (D), and other additives may be blended in that order, or two or more selected from zinc dithiophosphate (B), sarcosine compound (C), phosphorus compound (D), and other additives may be mixed in advance before blending.

[0113] [Uses of lubricating oil compositions] The lubricating oil composition of the present invention exhibits excellent performance in both preventing brake squeal and preventing seizure. Therefore, it is suitable for use in industrial machinery. Furthermore, when commonly lubricating industrial machinery equipped with transmissions (gears), hydraulic operating parts, and wet brakes, such as agricultural machinery like tractors, rice transplanters, binders, and combine harvesters; construction machinery like hydraulic excavators, cranes, and bulldozers; and transport machinery like dump trucks, forklifts, shovel loaders, and rough-terrain transport vehicles, it can prevent transmission (gear) seizure while preventing wet brake squeal. Therefore, it is suitable for use in these applications.

[0114] [Lubrication method] The lubrication method of the present invention is a lubrication method using the lubricating oil composition of the present invention. The lubricating oil composition of the present invention exhibits excellent performance in both brake squeal prevention and seizure resistance. Therefore, the lubrication method of the present invention can effectively utilize the above-mentioned performance of the lubricating oil composition of the present invention and is therefore suitably used in industrial machinery. In addition, among industrial machinery, it is suitably used when lubricating a common industrial machine equipped with a transmission (gear), hydraulic actuation parts, and wet brakes, such as agricultural machinery such as tractors, rice transplanters, binders, and combine harvesters, construction machinery such as hydraulic excavators, cranes, and bulldozers, and transport machinery such as dump trucks, forklifts, shovel loaders, and rough terrain transport vehicles.

[0115] [Industrial machinery] The industrial machinery of the present invention contains the lubricating oil composition of the present invention. In one aspect of the present invention, it is preferable that the industrial machine comprises a transmission (gears), a hydraulic actuation unit, and a wet brake. Industrial machinery equipped with a transmission (gears), hydraulic operating parts, and wet brakes includes, for example, agricultural machinery such as tractors, rice transplanters, binders, and combine harvesters; construction machinery such as hydraulic excavators, cranes, and bulldozers; and transport machinery such as dump trucks, forklifts, shovel loaders, and rough-terrain transport vehicles. Furthermore, in these industrial machines, from the viewpoint of effectively utilizing the excellent performance of the lubricating oil composition of the present invention, it is preferable to have a mechanism that commonly lubricates the transmission (gears), hydraulic operating parts, and wet brakes.

[0116] [One aspect of the present invention provided] According to one aspect of the present invention, the following [1] to

[13] are provided. [1] A lubricating oil composition containing a base oil (A), zinc dithiophosphate (B), and a sarcosine compound (C), A lubricating oil composition in which the content of the sarcosine compound (C) is greater than 0.05% by mass and less than or equal to 0.40% by mass on a total basis of the lubricating oil composition, and which satisfies the following requirement (α) or (β). Requirement (α): If the content of the sarcosine compound (C) is greater than 0.05% by mass and less than 0.20% by mass on a total basis of the lubricating oil composition, then the composition optionally contains one or more phosphorus compounds (D) selected from the group consisting of acidic phosphate esters (D1) and their amine salts (D2). Requirement (β): If the content of the sarcosine compound (C) is 0.20% by mass or more and 0.40% by mass or less on a total basis of the lubricating oil composition, the lubricating oil composition contains less than 0.50% by mass of the phosphorus compound (D) on a total basis. [2] The lubricating oil composition described in [1] above, which, if the requirement (α) is met, further satisfies the following requirement (α1). • Requirement (α1): The content ratio of the sarcosine compound (C) to the zinc dithiophosphate (B) [(C) / (B)] is greater than 0.04 and less than 0.17 by mass. [3] The lubricating oil composition according to [1] or [2] above, which, if the above requirement (α) is met, further satisfies the following requirement (α2). • Requirement (α2): The content ratio of the phosphorus compound (D) to the zinc dithiophosphate (B) [(D) / (B)] is 1.04 or less by mass. [4] The lubricating oil composition described in [1] above, which, if the above requirement (β) is met, further satisfies the following requirement (β1). • Requirement (β1): The content ratio of the sarcosine compound (C) to the zinc dithiophosphate (B) [(C) / (B)] is 0.33 or less by mass. [5] The lubricating oil composition described in [1] or [4] above, which, if the above requirement (β) is met, further satisfies the following requirement (β2). Requirement (β2): The content ratio of the phosphorus compound (D) to the zinc dithiophosphate (B) [(D) / (B)] is less than 0.42 by mass. [6] The lubricating oil composition according to any one of [1] to [5] above, wherein the sarcosine compound (C) is a sarcosine compound (C1) represented by the following general formula (c-1). [ka] [In the general formula (c-1), R c1 R represents a hydrocarbon group having 2 to 30 carbon atoms, which may contain heteroatoms. c2 This represents a hydrogen atom or a methyl group. [7] The lubricating oil composition according to [6] above, wherein the sarcosine compound (C1) is a sarcosine compound (C2) represented by the following general formula (c-2). [ka] [In general formula (c-2), R C3 This indicates a hydrocarbon group with 1 to 29 carbon atoms. [8] A lubricating oil composition according to any of [1] to [7] above, for use in lubricating industrial machinery. [9] The lubricating oil composition according to [8] above, wherein the industrial machine has a transmission, a hydraulic actuation unit, and a wet brake.

[10] The lubricating oil composition according to [8] or [9] above, wherein the industrial machine is an agricultural machine.

[11] A method for lubricating industrial machinery using any of the lubricating oil compositions described in [1] to [7] above.

[12] The lubrication method according to

[11] above, wherein the industrial machine has a transmission, a hydraulic actuation unit, and a wet brake.

[13] The lubrication method according to

[11] or

[12] above, wherein the industrial machine is an agricultural machine. [Examples]

[0117] The present invention will be specifically described by the following examples, but the present invention is not limited to the following examples.

[0118] [Methods for measuring various physical properties] The properties of each raw material used in each example and comparative example, as well as the properties of each lubricating oil composition in each example and comparative example, were measured according to the following procedure. (1) Kinematic viscosity at 40°C, kinematic viscosity at 100°C, and viscosity index The kinematic viscosity at 40°C, kinematic viscosity at 100°C, and viscosity index of the base oil were measured and calculated in accordance with JIS K2283:2000. Furthermore, the kinematic viscosity at 40°C, the kinematic viscosity at 100°C, and the viscosity index of the lubricating oil composition were also measured and calculated in accordance with JIS K2283:2000. (2) Base value The base number of the lubricating oil composition was measured by potentiometric method (hydrochloric acid method) in accordance with JIS K2501:2003. (3) Various atomic contents The content of calcium atoms, phosphorus atoms, zinc atoms, and sulfur atoms in the lubricating oil composition was measured in accordance with JIS-5S-38-03. Furthermore, the nitrogen atom content in the lubricating oil composition was measured in accordance with JIS K2609:1998.

[0119] [Examples 1-9, Comparative Examples 1-7] The following base oils and various additives were thoroughly mixed in the amounts (mass%) shown in Table 1 to prepare lubricating oil compositions. Details of the base oils and various additives used in Examples 1 to 9 and Comparative Examples 1 to 7 are as shown below.

[0120] <Base oil (A)> · "100N mineral oil": Kinematic viscosity at 40°C = 30.0 mm 2 / s, kinematic viscosity at 100°C = 4.5 mm 2 / s, viscosity index = 125 · "500N mineral oil": Kinematic viscosity at 40°C = 90.5 mm 2 / s, kinematic viscosity at 100°C = 10.9 mm 2 / s, viscosity index = 107

[0121] <Zinc dithiophosphate (B)> · "Primary zinc dialkyldithiophosphate (primary ZnDTP)": A mixture of compounds in which the main alkyl group is a primary alkyl group with 4 carbon atoms and contains primary alkyl groups with 6 and 8 carbon atoms as other alkyl groups

[0122] <Sarcosine-based compound (C)> · "N-oleoyl sarcosine": In the above general formula (c-2), R c3 is a sarcosine-based compound in which the alkenyl group has 17 carbon atoms.

[0123] <Phosphorus-based compound (D)> · "Amine salt of acidic phosphate ester (D2)": Amine salts of alkyl acid phosphates and alkenyl acid phosphates The alkyl acid phosphates and alkenyl acid phosphates are a mixture of monooleyl acid phosphate, monooctyl acid phosphate, dioleyl acid phosphate, dioctyl acid phosphate, and didodecyl acid phosphate. The amine salts are a mixture of dodecylamine salts and undecylamine salts. · "Acidic phosphate ester (D) ": Oleyl acid phosphate

[0124] <Viscosity index improver> · "Viscosity Index Improver A": Non-dispersible polymethacrylate (Mw = 14×10 5 , resin content = 39% by mass) · "Viscosity Index Improver B": Non-dispersible polymethacrylate (Mw = 2.9×10 5 , resin content = 58% by mass) · "Viscosity Index Improver C": Non-dispersible polymethacrylate (Mw = 5.0×10 5 , resin content = unknown) The mass average molecular weight (Mw) of each viscosity index improver was measured by gel permeation chromatography and calculated as a value in terms of polystyrene conversion. <Other Additives> Friction modifiers, defoamers, oiliness agents, antioxidants, dispersants, metal detergents, metal deactivators, rust inhibitors, etc.

[0125] [Evaluation 1: Evaluation of Brake Squeal Prevention Performance] For the lubricating oil compositions prepared in the examples and comparative examples, based on JASO M 349:2012, using a low-speed sliding friction tester (LVFA tester), the friction coefficients on the friction plate (A795.D0AK) and the steel plate (FZ132-8-Y2) were measured. The test oil temperature during measurement was 80°C, and the surface pressure was 1 MPa. The friction coefficient was evaluated by the friction coefficient μ 50 at a rotational speed of 50 rpm. The friction coefficient μ 50 The smaller the value, the more the stick-slip is suppressed, and it can be said that the brake squeal prevention performance is good. Conversely, the larger the friction coefficient μ 50 , the more likely the stick-slip occurs, and the inferior the brake squeal prevention performance. In this example, the brake squeal prevention performance was evaluated according to the following criteria. · Friction coefficient μ 50 is 0.114 or less: Evaluation A (excellent brake squeal prevention performance) · Friction coefficient μ 50 is 0.115 or more: Evaluation F (inferior brake squeal prevention performance)

[0126] [Evaluation 2: Evaluation of extreme pressure resistance] In accordance with JIS K2519:1995, the load-bearing capacity (anti-seizure performance) was evaluated using a Soda four-ball testing machine at a rotational speed of 200 rpm. In this example, the seizure resistance was evaluated according to the following criteria. • Load capacity exceeding 0.55 MPa: Rating A (Excellent seizure resistance) • Load capacity between 0.50 MPa and 0.55 MPa: Rating B (slightly superior seizure resistance) • Load capacity of 0.50 MPa or less: Rating F (Poor seizure resistance)

[0127] The results are shown in Tables 1 and 2. Note that in Tables 1 and 2, the content of each viscosity index improver includes the content of the diluent. Furthermore, in each lubricating oil composition, the total content of diluent derived from viscosity index improvers A to C is greater than 5.50% by mass and less than 6.00% by mass, based on the total volume of the lubricating oil composition.

[0128] [Table 1]

[0129] [Table 2]

[0130] From Tables 1 and 2, the following can be seen. The lubricating oil compositions of Examples 1 to 6 contain a base oil (A), zinc dithiophosphate (B), and a sarcosine compound (C), and satisfy requirement (α), demonstrating excellent brake noise prevention and seizure resistance. The lubricating oil compositions of Examples 7 to 9 contain a base oil (A), zinc dithiophosphate (B), and a sarcosine compound (C), and by satisfying requirement (β), they exhibit excellent brake noise prevention and seizure resistance. In contrast, the lubricating oil compositions of Comparative Examples 1, 5, and 6 do not contain sarcosine compounds (C), and therefore exhibit inferior brake squeal prevention performance. Furthermore, even when a lubricating oil composition contains phosphorus compounds (D), as in Comparative Examples 5 and 6, it is clear that if it does not contain sarcosine compounds (C), it will still exhibit inferior brake squeal prevention performance. Although the lubricating oil composition of Comparative Example 2 contains a base oil (A), zinc dithiophosphate (B), and a sarcosine compound (C), it is found to have inferior brake squeal prevention performance because the content of the sarcosine compound (C) is 0.05% by mass. Although the lubricating oil compositions of Comparative Examples 3, 4, and 7 contain a base oil (A), zinc dithiophosphate (B), and a sarcosine compound (C), they fail to meet either requirement (α) or requirement (β), and therefore exhibit inferior brake noise prevention performance.

Claims

1. A lubricating oil composition containing a base oil (A), zinc dithiophosphate (B), a sarcosine compound (C), and two or more polymethacrylates. The sarcosine compound (C) is a sarcosine compound (C1) represented by the following general formula (c-1): 【Chemistry 1】 [In the general formula (c-1) above, R c1 represents a hydrocarbon group having 2 to 30 carbon atoms, which may contain a heteroatom, and R c2 represents a hydrogen atom or a methyl group.] A lubricating oil composition for use in lubricating transmissions, hydraulic operating parts, and wet brakes, wherein the content of the sarcosine compound (C) is greater than 0.05% by mass and less than or equal to 0.40% by mass on a total basis of the lubricating oil composition, and satisfies the following requirement (α) or (β). Requirement (α): If the content of the sarcosine compound (C) is greater than 0.05% by mass and less than 0.20% by mass on a total basis of the lubricating oil composition, it contains one or more phosphorus compounds (D) selected from the group consisting of acidic phosphate esters (D1) and their amine salts (D2). Requirement (β): If the content of the sarcosine compound (C) is 0.20% by mass or more and 0.40% by mass or less on a total basis of the lubricating oil composition, the lubricating oil composition contains the phosphorus compound (D), and the content of the phosphorus compound (D) is 0.10% by mass or more and less than 0.50% by mass on a total basis of the lubricating oil composition.

2. The lubricating oil composition according to claim 1, which, if the above requirement (α) is met, further satisfies the following requirement (α1). Requirement (α1): The content ratio of the sarcosine compound (C) to the zinc dithiophosphate (B) [(C) / (B)] is greater than 0.04 and less than 0.17 by mass.

3. The lubricating oil composition according to claim 1 or 2, which, if the above requirement (α) is met, further satisfies the following requirement (α2). Requirement (α2): The content ratio of the phosphorus compound (D) to the zinc dithiophosphate (B) [(D) / (B)] is 1.04 or less by mass.

4. The lubricating oil composition according to claim 1, which, if the above requirement (β) is met, further satisfies the following requirement (β1). Requirement (β1): The content ratio of the sarcosine compound (C) to the zinc dithiophosphate (B) [(C) / (B)] is 0.33 or less by mass.

5. The lubricating oil composition according to claim 1 or 4, which, if the above requirement (β) is met, further satisfies the following requirement (β2). Requirement (β2): The content ratio of the phosphorus compound (D) to the zinc dithiophosphate (B) [(D) / (B)] is less than 0.42 by mass.

6. The lubricating oil composition according to any one of claims 1 to 5, wherein the sarcosine compound (C1) is a sarcosine compound (C2) represented by the following general formula (c-2). 【Chemistry 2】 [In general formula (c-2), R ｃ３ This indicates a hydrocarbon group having 1 to 19 carbon atoms.

7. The lubricating oil composition according to any one of claims 1 to 6, wherein the industrial machine is an agricultural machine.

8. A method for lubricating an industrial machine having a transmission, a hydraulic actuation part, and a wet brake, using the lubricating oil composition described in any one of claims 1 to 7.

9. The lubrication method according to claim 8, wherein the industrial machine is an agricultural machine.

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