Lubricating oil composition

Abstract

To provide a lubricant composition capable of having good balance between a low traction coefficient and high low temperature fluidity while maintaining kinematic viscosity at 40°C at an appropriate height.SOLUTION: There is provided a lubricant composition which comprises the following base oils (A) and (B): (A) a poly-α-olefin-based base oil which is a 1-tetradecene polymer and (B) a mineral oil-based base oil, wherein the base oil (A) contains a component (A1) which is a 1-tetradecene dimer and a component (A2) which is a 1-tetradecene trimer, a mass ratio ([component (A1)] / [component (A2)]) of the component (A1) to the component (A2) contained in the base oil A is 3 to 10, a content of the base oil (A) is 40 mass% or more and 75 mass% or less based on a total amount of the lubricant oil, a content of the base oil (B) is 25 mass% or more and 60 mass% or less based on the total amount of the lubricant oil and the total amount of the base oil (A) and the base oil (B) is 80 mass% or more based on the total amount of the lubricant oil and the composition has kinematic viscosity at 40°C of 8 to 30 mm2 / s.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] In recent years, lubricating oil compositions used in automobile engines, electric motors, transmissions, etc. have been required to have performance according to their applications, and various lubricating oil compositions have been studied. For example, in International Publication No. 2020 / 068527A1 (Patent Document 1), as a first base oil, a C28-32 hydrocarbon fraction (dimer) produced by oligomerization of C14 monoolefin, C16 monoolefin, or a mixture thereof in the presence of a Lewis acid catalyst, and an optionally contained C42-48 hydrocarbon fraction (trimer), and a base oil containing a Group II, III, or IV base oil different from the first base oil as an optionally contained second base oil are disclosed. However, conventional lubricating oil compositions such as those described in Patent Document 1 are not yet sufficient in terms of achieving an appropriate high kinematic viscosity at 40°C so that lubricating performance according to the application can be exhibited, while having a low traction coefficient and high low-temperature fluidity in a well-balanced manner.

[0003] Conventionally, electric motors and transmissions have generally been lubricated using different lubricating oil compositions. However, if it becomes possible to lubricate an electric motor and a transmission using the same lubricating oil composition, the circulation mechanism of the lubricating oil composition can be simplified. Therefore, in recent years, research has been conducted on lubricating an electric motor and a transmission with the same lubricating oil composition. In addition, in an oil-cooled electric motor, a high cooling effect can also be obtained by bringing the lubricating oil composition into contact with heat-generating parts inside the motor (such as coils, cores, magnets, etc.) as a cooling medium. Therefore, research on lubricating oil compositions that can also be used as cooling oils is underway. In the field of transmissions, in particular, from the viewpoints of fuel consumption reduction and durability improvement, a reduction in the traction coefficient is required. Thus, in the fields of electric motors and transmissions, depending on their applications, etc., in particular, while setting the kinematic viscosity at 40°C to an appropriate height such that both the power transmission efficiency, anti-wear property, and extreme pressure property (load-bearing property) are excellent, the emergence of a lubricating oil composition having a low traction coefficient and high low-temperature fluidity in a well-balanced manner is desired.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention has been made in view of the problems of the prior art, and an object thereof is to provide a lubricating oil composition capable of achieving a well-balanced low traction coefficient and high low-temperature fluidity while setting the kinematic viscosity at 40°C to an appropriate height.

Means for Solving the Problems

[0006] As a result of intensive research to achieve the above object, the inventors of the present invention have made the lubricating oil composition contain a lubricating oil base oil comprising base oil (A): a poly-α-olefin base oil which is a polymer of 1-tetradecene, and base oil (B): a mineral oil base oil. The base oil (A) is made to contain component (A1) which is a dimer of 1-tetradecene and component (A2) which is a trimer of 1-tetradecene. The mass ratio ([component (A1)] / [component (A2)]) of the components (A1) and (A2) contained in the base oil (A) is set to 3 to 10. Based on the total amount of the lubricating oil base oil, the content of the base oil (A) is set to 40% by mass or more and 75% by mass or less, and the content of the base oil (B) is set to 25% by mass or more and 60% by mass or less. Furthermore, based on the total amount of the lubricating oil base oil, the total amount of the base oil (A) and the base oil (B) is set to 80% by mass or more. By doing so, it has been found that it is possible to have a low traction coefficient and high low-temperature fluidity in good balance while setting the kinematic viscosity at 40°C to an appropriate level, and the present invention has been completed.

[0007] That is, the lubricating oil composition of the present invention is the following base oils (A) and (B): (A) A poly-α-olefin base oil which is a polymer of 1-tetradecene, (B) At least one selected from the group consisting of hydrocracked mineral oil-based base oils which are Group III base oils in the API base oil classification; hydrocracked base oils of GTL wax which are Group II base oils in the API base oil classification; and hydrocracked base oils of GTL wax which are Group III base oils in the API base oil classification a mineral oil base oil, and is a composition containing a lubricating oil base oil containing the same, the base oil (A) contains component (A1) which is a dimer of 1-tetradecene and component (A2) which is a trimer of 1-tetradecene, the mass ratio ([component (A1)] / [component (A2)]) of the components (A1) and (A2) contained in the base oil (A) is 3 to 10, based on the total amount of the lubricating oil base oil, the content of the base oil (A) is 60% by mass or more and 75% by mass or less, based on the total amount of the lubricating oil base oil, the content of the base oil (B) is 25% by mass or more and 40% by mass or less, based on the total amount of the lubricating oil base oil, the total amount of the base oil (A) and the base oil (B) is 80% by mass or more, and The kinematic viscosity of the composition at 40 °C is 8 to 30 mm 2 / s, which is characterized by this.

[0009] In the lubricating oil composition of the present invention, it is preferable that the total amount of the components (A1) and (A2) is 90% by mass or more based on the total amount of the base oil (A).

[0010] In the lubricating oil composition of the present invention, it is also preferable to further contain a poly(meth)acrylate-based pour point depressant.

[0011] Furthermore, in the lubricating oil composition of the present invention, it is preferable to further contain an anti-friction agent composed of (sub)phosphoric acid ester.

[0012] In addition, the lubricating oil composition of the present invention is preferably used for lubricating and / or cooling a transmission and / or an electric motor.

Advantages of the Invention

[0013] According to the present invention, it is possible to provide a lubricating oil composition capable of achieving a good balance between a low traction coefficient and high low-temperature fluidity while setting the kinematic viscosity at 40 °C to an appropriate level.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, the present invention will be described in detail according to its preferred embodiments. In this specification, unless otherwise specified, the notation "X to Y" for numerical values X and Y means "X or more and Y or less". When a unit is attached only to the numerical value Y in such notation, the unit is also applied to the numerical value X.

[0015] The lubricating oil composition of the present invention is the following base oils (A) and (B): (A) A poly-α-olefin base oil that is a polymer of 1-tetradecene, (B) A mineral oil base oil, A composition containing a lubricating base oil, and the base oil (A) contains a component (A1) which is a dimer of 1-tetradecene and a component (A2) which is a trimer of 1-tetradecene, the mass ratio ([component (A1)] / [component (A2)]) of the component (A1) and the component (A2) contained in the base oil (A) is 3 to 10, based on the total amount of the lubricating base oil, the content of the base oil (A) is 40% by mass or more and 75% by mass or less, based on the total amount of the lubricating base oil, the content of the base oil (B) is 25% by mass or more and 60% by mass or less, based on the total amount of the lubricating base oil, the total amount of the base oil (A) and the base oil (B) is 80% by mass or more, and the kinematic viscosity of the composition at 40 °C is 8 to 30 mm 2 / s, characterized thereby. First, the base oils (A) and (B) will be described, and then the composition, properties, etc. of the lubricating base oil and the lubricating oil composition will be described.

[0016] [Base oil (A)] The base oil (A) according to the present invention is a poly-α-olefin base oil which is a polymer of 1-tetradecene. And the base oil (A) needs to contain a component (A1) which is a dimer of 1-tetradecene and a component (A2) which is a trimer of 1-tetradecene. Thus, the base oil (A) is a polymer of 1-tetradecene containing the component (A1) and the component (A2) as essential components.

[0017] In addition, for the base oil (A), the mass ratio ([component (A1)] / [component (A2)]) of the components (A1) and (A2) contained in the base oil (A) needs to be 3 to 10. When the mass ratio of the components (A1) and (A2) is at or above the lower limit, the traction coefficient becomes a lower value compared to the case where it is less than the lower limit. On the other hand, when it is at or below the upper limit, it is possible to achieve both a lower traction coefficient and high low-temperature fluidity (reduction of low-temperature viscosity) compared to the case where it exceeds the upper limit. Also, from the same perspective, a higher effect can be obtained, so the mass ratio ([component (A1)] / [component (A2)]) of the components (A1) and (A2) is more preferably 4 to 9, still more preferably 4 to 6, particularly preferably 4 to 5.5, and most preferably 4 to 5.3.

[0018] In addition, as the base oil (A), those in which the total amount of the components (A1) and (A2) is 90% by mass or more (more preferably 93% by mass or more, still more preferably 98 to 100% by mass) based on the total amount of the base oil (A) are preferred. When the total amount of the components (A1) and (A2) is at or above the lower limit, it is possible to achieve both a lower traction coefficient and a further reduction in low-temperature viscosity compared to the case where it is less than the lower limit.

[0019] In addition, the content of the component (A1) in the base oil (A) is more preferably 75 to 91% by mass, still more preferably 80 to 91% by mass, based on the total amount of the base oil (A). When the content of the component (A1) is at or above the lower limit, the traction coefficient can be made a lower value compared to the case where it is less than the lower limit. On the other hand, when it is at or below the upper limit, the low-temperature viscosity can be further reduced compared to the case where it exceeds the upper limit.

[0020] Further, the content of the component (A2) in the base oil (A) is more preferably 10 to 33% by mass, and even more preferably 10 to 20% by mass, based on the total amount of the base oil (A). When the content of the component (A2) is at least the lower limit, it becomes possible to maintain the oil consumption suppression performance as compared with the case where it is less than the lower limit. On the other hand, when it is at most the upper limit, it becomes possible to make the traction coefficient a lower value as compared with the case where it exceeds the upper limit.

[0021] Moreover, since the base oil (A) may be a polymer of 1-tetradecene, it may further contain other polymerization components (tetramers, pentamers, etc.) formed by polymerizing 1-tetradecene other than the components (A1) and (A2). However, from the viewpoint of maintaining a low traction coefficient, other polymerization components contained in the base oil (A) are preferably polymers of 1-tetradecene pentamer or less (tetramer and / or pentamer of 1-tetradecene), and more preferably tetramer of 1-tetradecene. Thus, in the base oil (A), even when other polymerization components other than the components (A1) and (A2) are contained, it is more preferable that the polymerization component is a tetramer of 1-tetradecene (in other words, it is more preferable that it does not contain polymers of 1-tetradecene pentamer or more).

[0022] When the base oil (A) contains other polymerization components other than the components (A1) and (A2), the content of the other polymerization components (total amount of other polymerization components) is preferably 10% by mass or less (more preferably 7% by mass or less, even more preferably 2% by mass or less) based on the total amount of the base oil (A). When the content of the other polymerization components (tetramer, pentamer, etc. of 1-tetradecene) is at most the upper limit, it becomes possible to more efficiently lower the traction coefficient as compared with the case where it exceeds the upper limit.

[0023] The contents of the component (A1), the component (A2), and other polymerization components (tetramers, pentamers, etc. of 1-tetradecene) in the base oil (A) may be determined by performing gas chromatography measurement on the base oil to obtain a gas chromatogram, and calculating the values (area %) of the contents based on the mass of each component (dimers, trimers, other polymerization components (tetramers, pentamers, etc.)) in the base oil. Such an analysis method by gas chromatography is not particularly limited. For example, under the conditions described below, after obtaining gas chromatograms of dimers, trimers, tetramers, pentamers, etc. of 1-tetradecene as reference substances, a gas chromatogram of the base oil to be measured is obtained, and from the comparison with the measurement results of the reference substances, a method for determining the relationship of the contents (content ratios: area %) based on the mass of each component (dimers, trimers, tetramers, pentamers, etc.) contained in the base oil to be measured may be adopted.

[0024] <Gas Chromatography Conditions> Measuring device: GC-2010 (manufactured by Shimadzu Corporation) Column: Ultra Alloy-1HT (length: 30 mm, inner diameter: 0.25 mm, manufactured by Frontier Lab Co., Ltd.) Carrier gas: Helium (100 kPa) Measurement sample: Use the base oil as it is (without dilution with a solvent). Sample injection volume: 0.2 μL Detector: Flame ionization detector (FID) Detector temperature: 300 °C Oven temperature: Hold at 40 °C for 5 minutes, then increase the temperature to 280 °C at a rate of 5 °C / min.

[0025] Also, when the base oil (A) is obtained by mixing a dimer of 1-tetradecene and a trimer of 1-tetradecene (and optionally other polymerization components), the charging ratio of each component during its production may be directly used as the mass ratio of each component. Note that the methods for producing each component of the polymer of 1-tetradecene (the dimer of 1-tetradecene (component (A1)), the trimer of 1-tetradecene (component (A2)), other polymerization components of 1-tetradecene (tetramer, pentamer, etc.)) are not particularly limited, and each can be produced by known methods. For example, when producing each component such as component (A1) and component (A2), after polymerizing 1-tetradecene by a known method (such as a method of low-pressure polymerization in the presence of a catalyst by the Ziegler catalyst method, radical polymerization method, aluminum chloride method, boron fluoride method, etc.), the target components can be isolated from the polymer by distillation separation, and a method of obtaining each component can be adopted.

[0026] Also, the method for producing the base oil (A) is not particularly limited. As described above, after isolating each component of the polymer of 1-tetradecene, a method of producing the base oil (A) may be adopted by appropriately mixing the dimer of 1-tetradecene (component (A1)), the trimer of 1-tetradecene (component (A2)), and other polymerization components of 1-tetradecene (tetramer, pentamer, etc.) according to the target design.

[0027] [Base oil (B)] The base oil (B) according to the present invention is a mineral oil-based base oil. Thus, by using the base oil (A) and the base oil (B) in combination, it is possible to have a low traction coefficient and good low-temperature fluidity in a well-balanced manner. Note that depending on the type of the base oil (A) and the types of other components that may be contained, etc., by appropriately selecting and using the type of the base oil (B), it is also possible to efficiently bring the kinematic viscosity (kinematic viscosity at 40°C, etc.) of the finally obtained composition into a desired range.

[0028] As the mineral oil base oil that can be used as the base oil (B), there are no particular restrictions, and known mineral oils can be used as appropriate. Among such mineral oil base oils, Group II base oils in the API base oil classification (classification of base oils by API (American Petroleum Institute)) and Group III base oils in the API base oil classification are more preferable. Note that Group II base oils in the API base oil classification are mineral oil base oils with a sulfur content of 0.03% by mass or less, a saturation content (saturated hydrocarbon) of 90% by volume or more, and a viscosity index of 80 or more and less than 120. Group III base oils in the API base oil classification are mineral oil base oils with a sulfur content of 0.03% by mass or less, a saturation content (saturated hydrocarbon) of 90% by volume or more, and a viscosity index of 120 or more.

[0029] In addition, as the mineral oil base oil, for example, a lubricating oil fraction obtained by atmospheric distillation and / or vacuum distillation of crude oil is refined by one or a combination of two or more selected from purification treatments such as solvent dewaxing, solvent extraction, hydrocracking, solvent deasphalting, catalytic deasphalting, hydrorefining, sulfuric acid washing, and clay treatment. Paraffinic mineral oils, normal paraffin base oils, isoparaffin base oils, and mixtures thereof can be used.

[0030] Preferable examples of the mineral oil base oil include base oils obtained by using the following base oils (1) to (8) as raw materials, refining this raw material oil and / or the lubricating oil fraction recovered from this raw material oil by a predetermined refining method, and recovering the lubricating oil fraction. (1) Distillate oil obtained by atmospheric distillation of paraffinic crude oil and / or mixed-base crude oil (2) Distillate oil (WVGO) obtained by vacuum distillation of atmospheric distillation residue oil of paraffinic crude oil and / or mixed-base crude oil (3) Wax (such as slack wax) obtained by the lubricating oil deasphalting process and / or synthetic wax (such as Fischer-Tropsch wax, GTL wax) obtained by the gas-to-liquid (GTL) process or the like (4) One or more mixed oils selected from base oils (1) to (3) and / or mild hydrocracking treated oils of said mixed oils (5) Two or more mixed oils selected from base oils (1) to (4) (6) Decanted oil (DAO) of base oil (1), (2), (3), (4) or (5) (7) Mild hydrocracking treated oil (MHC) of base oil (6) (8) Two or more mixed oils selected from base oils (1) to (7).

[0031] Note that as the said predetermined purification method, hydrocracking purification such as hydrocracking and hydrofinishing; solvent purification such as furfural solvent extraction; dewaxing such as solvent dewaxing and catalytic dewaxing; clay purification with acidic clay or activated clay; chemical (acid or alkali) washing such as sulfuric acid washing and caustic soda washing are preferred. One of these purification methods may be carried out alone, or two or more may be combined. Also, when combining two or more purification methods, the order is not particularly limited and can be appropriately selected.

[0032] Also, as the mineral oil-based base oil, the following base oil (9) or (10) obtained by performing a predetermined treatment on the base oil selected from the said base oils (1) to (8) or the lubricating oil fraction recovered from the said base oil is particularly preferred. (9) Hydrocracking the base oil selected from the said base oils (1) to (8) or the lubricating oil fraction recovered from the said base oil, and performing dewaxing treatment such as solvent dewaxing or catalytic dewaxing on the product or the lubricating oil fraction recovered from the product by distillation or the like, or hydrocracked base oil obtained by distilling after performing the said dewaxing treatment (10) Hydroisomerizing the base oil selected from the said base oils (1) to (8) or the lubricating oil fraction recovered from the said base oil, and performing dewaxing treatment such as solvent dewaxing or catalytic dewaxing on the product or the lubricating oil fraction recovered from the product by distillation or the like, or hydroisomerized base oil obtained by distilling after performing the said dewaxing treatment.

[0033] Note that, as the lubricating oil base oils (9) and (10), those produced through a contact dewaxing process (step) as a dewaxing treatment are more preferable respectively. Further, when obtaining the lubricating oil base oil of (9) or (10), a solvent refining treatment and / or a hydrofinishing treatment process may be further performed at an appropriate stage as necessary.

[0034] Such mineral oil-based base oils (base oil (B)) may be used by individually using one type of mineral oil or in combination of two or more types. Also, commercially available products may be used as the base oil (B).

[0035] [Lubricating oil base oil] The lubricating oil base oil according to the present invention contains the base oils (A) and (B). Further, in the lubricating oil base oil, the content (total amount) of the base oils (A) and (B) needs to be 80% by mass or more based on the total amount of the lubricating oil base oil. By setting the total amount of the base oils (A) and (B) to be equal to or higher than the lower limit, compared with the case where it is less than the lower limit, it becomes possible to maintain the high-temperature detergency and water resistance of the composition at a high level, and also when further using an additive to obtain characteristics according to the application, the effect of the additive becomes more likely to appear, and it becomes possible to more efficiently obtain a composition having characteristics according to the purpose. Further, since it becomes possible to obtain a higher effect from the same viewpoint, the content (total amount) of the base oils (A) and (B) based on the total amount of the lubricating oil base oil is more preferably 90% by mass or more (more preferably 95% by mass or more, particularly preferably 98% by mass or more). Note that the base oil other than the base oils (A) and (B) is not particularly limited, and examples thereof include base oils of Group IV and Group V in the API base oil classification. Note that, from the viewpoint of improving high-temperature detergency and water resistance, the lubricating oil base oil composed only of the base oils (A) and (B) is more preferable.

[0036] In addition, in the lubricating oil base oil according to the present invention, the content of the base oil (A) needs to be 40% by mass or more and 75% by mass or less based on the total amount of the lubricating oil base oil. When the content of the base oil (A) is equal to or higher than the lower limit, the traction coefficient becomes a lower value compared to the case where it is less than the lower limit. On the other hand, when it is equal to or lower than the upper limit, the low-temperature fluidity becomes higher compared to the case where it exceeds the upper limit. Further, from the same viewpoint, it becomes possible to obtain a higher effect. Therefore, the content of the base oil (A) based on the total amount of the lubricating oil base oil is preferably 50% by mass or more and 75% by mass or less (more preferably 60% by mass or more and 75% by mass or less).

[0037] In addition, in the lubricating oil base oil according to the present invention, the content of the base oil (B) needs to be 25% by mass or more and 60% by mass or less based on the total amount of the lubricating oil base oil. When the content of the base oil (B) is equal to or higher than the lower limit, the low-temperature fluidity becomes higher compared to the case where it is less than the lower limit. On the other hand, when it is equal to or lower than the upper limit, the traction coefficient becomes a lower value compared to the case where it exceeds the upper limit. Further, from the same viewpoint, it becomes possible to obtain a higher effect. Therefore, the content of the base oil (B) based on the total amount of the lubricating oil base oil is preferably 25% by mass or more and 50% by mass or less (more preferably 25% by mass or more and 40% by mass or less).

[0038] In addition, the content of the component (A1) in the lubricating oil base oil is more preferably 30 to 68% by mass, and even more preferably 40 to 68% by mass, based on the total amount of the lubricating oil base oil. When the content of the component (A1) is equal to or higher than the lower limit, it becomes possible to make the traction coefficient a lower value compared to the case where it is less than the lower limit. On the other hand, when it is equal to or lower than the upper limit, it becomes possible to further improve the low-temperature fluidity compared to the case where it exceeds the upper limit. In addition, when the content of the component (A1) is equal to or lower than the upper limit, the performance of suppressing oil consumption tends to improve.

[0039] Further, the content of the component (A2) in the lubricating base oil is more preferably 7 to 15% by mass, and even more preferably 7.5 to 11.3% by mass, based on the total amount of the lubricating base oil. When the content of the component (A2) is equal to or higher than the lower limit, the traction coefficient can be made lower than that in the case where the content is less than the lower limit. On the other hand, when the content is equal to or lower than the upper limit, it is possible to achieve both a more efficient low traction coefficient and high low-temperature fluidity as compared with the case where the upper limit is exceeded. In addition, when the content of the component (A2) is equal to or lower than the upper limit, the oil consumption suppression performance tends to improve.

[0040] Furthermore, in the lubricating base oil according to the present invention, since it is possible to more efficiently and more balancedly achieve both a lower traction coefficient and an improved low-temperature fluidity, the mass ratio ([base oil (A)] / [base oil (B)]) of the base oils (A) and (B) in the lubricating base oil is more preferably 2 / 3 to 3 (more preferably from 1 to 3).

[0041] In addition, as the lubricating base oil according to the present invention, the kinematic viscosity at 40°C is preferably 8.0 to 25.0 mm 2 / s, more preferably 12.0 to 18.0 mm 2 / s, even more preferably 13.9 to 17.6 mm 2 / s, and particularly preferably 15.3 to 17.6 mm 2 / s. In the present specification, the "kinematic viscosity at 40°C" means the kinematic viscosity at 40°C measured in accordance with JIS K2283-2000 using an automatic viscometer (trade name "CAV-2100", manufactured by Cannon Instrument Company) as a measuring device.

[0042] As the lubricating base oil according to the present invention, the kinematic viscosity at 100°C is preferably 3.0 to 5.0 mm 2 / s, more preferably 3.5 to 4.5 mm 2 / s, even more preferably 3.5 to 4. mm 2 / s, and particularly preferably 3.9 to 4.1 mm 2Those with / s are particularly preferred. In this specification, the "kinematic viscosity at 100°C" means the kinematic viscosity at 100°C measured in accordance with JIS K2283-2000 using an automatic viscometer (trade name "CAV-2100", manufactured by Cannon Instrument Company) as the measuring device.

[0043] Further, for the lubricating base oil according to the present invention, when the kinematic viscosity of the base oil at 100°C is 2 mm 2 / s or more, those with a viscosity index of 105 or more (more preferably 130 to 140) are preferred. When the viscosity index is below the upper limit, compared with the case where it exceeds the upper limit, the rapid increase in viscosity at low temperatures is more suppressed, and the fluidity at low temperatures is higher. On the other hand, when the viscosity index is above the lower limit, compared with the case where it is below the lower limit, the temperature dependence of the viscosity of the resulting lubricating oil composition is more reduced, and it is possible to further improve the power transmission efficiency in a wide temperature range. In this specification, the "viscosity index" means the viscosity index measured in accordance with JIS K 2283-2000.

[0044] [Lubricating Oil Composition] The lubricating oil composition of the present invention is a composition containing the above lubricating base oil, and has a kinematic viscosity at 40°C of 8 to 30 mm 2 / s. Thus, the lubricating oil composition of the present invention only needs to contain the above lubricating base oil and have a kinematic viscosity at a specific temperature within the above range at, for example, 4°C. It may be in a form containing only the above lubricating base oil (in this case, the lubricating oil composition becomes a composition containing base oil (A) and base oil (B) (a composition composed of the lubricating base oil)), or may be in a form containing an additive together with the above lubricating base oil.

[0045] As described above, the lubricating oil composition of the present invention has a kinematic viscosity at 40°C of 8 to 30 mm 2It is necessary to be / s. When the kinematic viscosity at 40°C is equal to or below the upper limit, compared with the case where it exceeds the upper limit, especially in a relatively low temperature range near 40°C (preferably about 20 to 60°C), it is possible to improve the power transmission efficiency. On the other hand, when the kinematic viscosity at 40°C is equal to or above the lower limit, compared with the case where it is below the lower limit, especially in a relatively low temperature range near 40°C (preferably about 20 to 60°C), it is possible to further improve the oil film forming property and oil film retention property of the lubricating oil composition at the lubricated part, and it is possible to have excellent anti-wear property and extreme pressure property (load-bearing property). That is, in the lubricating oil composition of the present invention, by setting the kinematic viscosity at 40°C to 8 to 30 mm 2 / s, it is possible to improve the power transmission efficiency, anti-wear property, and extreme pressure property. From the same perspective, since higher effects can be obtained, the kinematic viscosity of the lubricating oil composition at 40°C is more preferably 10 to 20 mm 2 / s, and even more preferably 14 to 18 mm 2 / s. Also, the kinematic viscosity of such a composition can be adjusted to the above desired range by appropriately changing the types and amounts of base oil (A) and base oil (B) (and in some cases, the types and amounts of further added components (additives)) within the ranges defined in the present invention.

[0046] In addition, the content of the lubricating oil base oil in the lubricating oil composition of the present invention is not particularly limited, but it is preferably 90% by mass or more (more preferably 92% by mass or more, even more preferably 95% by mass or more) based on the total amount of the lubricating oil composition.

[0047] When the lubricating oil composition of the present invention contains an additive together with the lubricating oil base oil, as such an additive, depending on its use, known additives used in the field of lubricating oils (for example, those described in JP-A-2003-155492, WO 2017 / 073748, JP-A-2020-76004, etc.) can be appropriately used.

[0048] Such additives are not particularly limited, and examples thereof include viscosity index improvers, pour point depressants, ashless dispersants, metal detergents, antioxidants, antiwear agents, metal deactivators, rubber swelling agents, friction modifiers, defoamers, viscosity modifiers, diluent oils, and the like. Such additives may be used alone or in combination of two or more depending on the use of the lubricating oil composition.

[0049] The viscosity index improver is not particularly limited, and known viscosity index improvers can be appropriately used. Among the viscosity index improvers, poly(meth)acrylate-based viscosity index improvers (viscosity index improvers composed of poly(meth)acrylate) are more preferable from the viewpoints of the effect of increasing the viscosity index and the improvement of shear stability. In the present specification, “(meth)acrylate” means acrylate and / or methacrylate. Such poly(meth)acrylate-based viscosity index improvers may be so-called non-dispersed type or dispersed type. Further, the poly(meth)acrylate used for the viscosity index improver preferably has a weight average molecular weight of 5,000 to 35,000. Here, the “weight average molecular weight” means a value obtained by gel permeation chromatography (GPC) (molecular weight obtained by conversion to standard polystyrene). The viscosity index improver may be used alone or in combination of two or more. When using a viscosity index improver, its content is preferably 0.1 to 10.0% by mass (more preferably 0.1 to 5.0% by mass) based on the total amount of the lubricating oil composition.

[0050] The pour point depressant is not particularly limited, and known pour point depressants can be appropriately used. For example, poly(meth)acrylate, ethylene-vinyl acetate copolymer, etc. can be mentioned. Among such pour point depressants, from the viewpoints of low-temperature pour point depressing action and improvement of shear stability, poly(meth)acrylate-based pour point depressants (pour point depressants composed of poly(meth)acrylate) are more preferable. Such poly(meth)acrylate-based pour point depressants may be so-called non-dispersed type or dispersed type. Further, as the poly(meth)acrylate used for the pour point depressant, from the viewpoints of improving the pour point depressing action and shear stability, those having a weight average molecular weight of 40,000 to 100,000 are preferable. Further, it is more preferable that the upper limit value of such a weight average molecular weight is 80,000 or less (more preferably 60,000 or less). Here, the "weight average molecular weight" means a value determined by gel permeation chromatography (GPC) (molecular weight obtained by conversion to standard polystyrene). Further, the pour point depressant may be used alone or in combination of two or more. When using a pour point depressant, its content is preferably 0.01 to 1.0% by mass (more preferably 0.03 to 0.6% by mass) based on the total amount of the lubricating oil composition.

[0051] The ashless dispersant is not particularly limited, and known ashless dispersants (see, for example, JP-A-2003-155492, JP-A-2020-76004, WO 2013 / 147162, etc.) can be appropriately used. Among them, non-boronated succinimide, boronated succinimide, and mixtures thereof can be preferably used. Note that as the non-boronated succinimide, the boronated succinimide, or a mixture thereof, those having a nitrogen atom content of 0.5 to 3.0% by mass are preferable. The ashless dispersant may be used alone or in combination of two or more. Further, when using the ashless dispersant, its content is preferably 0.2 to 6.0% by mass (more preferably 0.5 to 5.0% by mass) based on the total amount of the lubricating oil composition.

[0052] The metal detergent is not particularly limited, and examples thereof include alkaline earth metal sulfonates, alkaline earth metal phenates, alkaline earth metal salicylates, etc. The metal detergent may be used alone or in combination of two or more. Further, when using the metal detergent, its content is preferably 0.01 to 1.0% by mass (more preferably 0.05 to 0.6% by mass) based on the total amount of the lubricating oil composition.

[0053] The antioxidant is not particularly limited, and examples thereof include phenolic antioxidants and amine antioxidants. The antioxidant may be used alone or in combination of two or more. When using the antioxidant, its content is preferably 0.1 to 2.0% by mass (more preferably 0.2 to 1.0% by mass) based on the total amount of the lubricating oil composition.

[0054] The antiwear agent is not particularly limited, and known compounds used as antiwear agents in the field of lubricating oil compositions (see, for example, JP-A-2003-155492, JP-A-2020-76004, WO 2013 / 147162, etc.) can be appropriately used. Among them, (sub)phosphoric acid esters are more preferable. In this specification, the term "(sub)phosphoric acid ester" means a phosphoric acid ester and / or a phosphorous acid ester. As the antiwear agent composed of such (sub)phosphoric acid esters, those having a phosphorus atom (P) content of 2.0 to 35.0% by mass are preferable. The antiwear agent may be used alone or in combination of two or more. When using an antiwear agent, its content is preferably 0.02 to 2.0% by mass (more preferably 0.05 to 1.0% by mass) based on the total amount of the lubricating oil composition. Although it is possible to use zinc dialkyldithiophosphate (ZnDTP) as the antiwear agent, when used for lubricating a transmission, in terms of antiwear performance, it does not necessarily provide a high-level effect compared to other components such as (sub)phosphoric acid esters. Therefore, from the perspective of lubricating an electric motor and a transmission with the same lubricating oil composition, it is preferable to use something other than ZnDTP, and among them, it is particularly preferable to use (sub)phosphoric acid esters.

[0055] The metal deactivator is not particularly limited. Examples include imidazoline, pyrimidine derivatives, alkylthiadiazole, mercaptobenzothiazole, benzotriazole or its derivatives, tolyltriazole or its derivatives, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5-bisdialkyldithiocarbamate, 2-(alkyldithio)benzimidazole, β-(o-carboxybenzylthio)propionitrile, and the like. The metal deactivator may be used alone or in combination of two or more. When using a metal deactivator, its content is preferably 0.01 to 0.5% by mass (more preferably 0.02 to 0.3% by mass) based on the total amount of the lubricating oil composition.

[0056] The rubber swelling agent is not particularly limited, and known compounds that can be used as seal swelling agents for lubricating oils can be appropriately used. For example, seal swelling agents such as ester-based, sulfur-based, and aromatic-based (such as sulfolane compounds) can be mentioned. The rubber swelling agent may be used alone or in combination of two or more. When using a rubber swelling agent, its content is not particularly limited, but it is preferably 0.01 to 1.0% by mass (more preferably 0.05 to 0.8% by mass) based on the total amount of the lubricating oil composition.

[0057] The friction modifier is not particularly limited. For example, amine-based, amide-based, imide-based, fatty acid ester-based, fatty acid-based, aliphatic alcohol-based, and aliphatic ether-based friction modifiers can be mentioned. Further, as such a friction modifier, from the viewpoint of obtaining a higher friction reduction effect, amine-based friction modifiers are more preferable, and alkylamines and alkenylamines are even more preferable. The friction modifier may be used alone or in combination of two or more. When using a friction modifier, its content is preferably 0.005 to 3.0% by mass (more preferably 0.01 to 2.5% by mass) based on the total amount of the lubricating oil composition.

[0058] Examples of the defoaming agent include silicone oils having a kinematic viscosity at 25°C of 1,000 to 100,000 mm2 / s, alkenyl succinic acid derivatives, esters of polyhydroxy aliphatic alcohols and long-chain fatty acids, methyl salicylate, and o-hydroxybenzyl alcohol. The defoaming agent may be used alone or in combination of two or more. When using a defoaming agent, its content is not particularly limited, but it is preferably 0.0001 to 0.005% by mass (more preferably 0.0003 to 0.003% by mass) based on the total amount of the lubricating oil composition.

[0059] The viscosity modifier is not particularly limited, and known compounds used as viscosity modifiers in the field of lubricating oil compositions can be appropriately used. Such a viscosity modifier is preferably a polymer having a weight average molecular weight of 5,000 to 20,000 (more preferably 6,000 to 15,000). Further, as the polymer having a weight average molecular weight of 5,000 to 20,000 used as the viscosity modifier, an ethylene-propylene copolymer is more preferable. The ethylene-propylene copolymer may be a block copolymer or a random copolymer. Here, the "weight average molecular weight" means a value determined by gel permeation chromatography (GPC) (molecular weight obtained by conversion to standard polystyrene). The viscosity modifier may be used alone or in combination of two or more. When such a viscosity modifier is used, its content is not particularly limited, but it is preferably 0.1 to 10.0% by mass (more preferably 0.1 to 5.0% by mass) based on the total amount of the lubricating oil composition.

[0060] The diluent oil is also not particularly limited, and known ones can be appropriately used. When such a diluent oil is used, its content is not particularly limited, but it is preferably 0.01 to 10.0% by mass (more preferably 0.01 to 5.0% by mass) based on the total amount of the lubricating oil composition.

[0061] Further, when the lubricating oil composition of the present invention is in a form containing an additive, it is more preferable to contain the poly(meth)acrylate pour point depressant together with the lubricating base oil. When the lubricating oil composition of the present invention further contains a poly(meth)acrylate pour point depressant, it becomes possible to further improve the low-temperature fluidity and further reduce the low-temperature viscosity.

[0062] Furthermore, when the lubricating oil composition of the present invention is in a form containing an additive, it is more preferable that it contains an anti-friction agent composed of (sub)phosphate ester together with the lubricating base oil. When the lubricating oil composition of the present invention further contains an anti-friction agent composed of (sub)phosphate ester, it becomes possible to further improve the anti-wear property.

[0063] In addition, when adding the above-described additives to the lubricating oil composition of the present invention, the additives may be prepared and added separately for each component, or a mixture of other components may be prepared and added. As such a mixture of other components, commercially available packages (for example, additive packages containing ashless dispersants, metal detergents, antioxidants, anti-wear agents, metal deactivators, rubber swelling agents, diluent oils) may be appropriately used.

[0064] Also, the traction coefficient of the lubricating oil composition of the present invention is preferably 0.0054 or less, more preferably 0.0040 to 0.0054, and even more preferably 0.0042 to 0.0053. When the traction coefficient is below the upper limit, compared with the case where it exceeds the upper limit, when this is used, a higher effect can be obtained in terms of fuel savings and durability improvement, and the power transmission efficiency can be further improved. On the other hand, when it is above the lower limit, compared with the case where it is less than the lower limit, the oil film forming property and oil film holding property of the lubricating oil composition at the lubricated part are further improved, and it becomes possible to maintain a better lubrication state in a wide temperature range. Here, the "traction coefficient" refers to a value measured under the conditions of temperature: 25°C, load: 20 N, peripheral speed (average speed): 0.5 m / s, and slip ratio (SRR): 3% using an EHL tester (tester "EHD2" manufactured by PCS Instruments) and using a steel disk and a steel ball as members.

[0065] The BF viscosity of the lubricating oil composition of the present invention at -40°C is preferably 10,000 mPa·s or less (more preferably 8,000 mPa·s, still more preferably 7,200 mPa·s or less, particularly preferably 6,000 mPa·s or less, and most preferably 4,400 mPa·s or less). When the BF viscosity at -40°C is equal to or less than the above upper limit value, it can be determined that the low-temperature fluidity of the lubricating oil composition is at a high level. Note that the BF viscosity at -40°C in this specification means a value measured in accordance with ASTM D 2983.

[0066] In addition, as the lubricating oil composition of the present invention, the kinematic viscosity at 100°C is preferably 1.0 to 5.0 mm 2 / s, and more preferably 3.5 to 4.1 mm 2 / s. When the kinematic viscosity at 100°C is equal to or less than the above upper limit, compared with the case where it exceeds the upper limit, it is possible to further improve the power transmission efficiency particularly in a relatively high-temperature range near 100°C (preferably about 80 to 120°C). On the other hand, when the kinematic viscosity at 100°C is equal to or more than the above lower limit, compared with the case where it is less than the lower limit, particularly in a relatively high-temperature range near 100°C (preferably about 80 to 120°C), the oil film forming property and oil film holding property of the lubricating oil composition at the lubricated part are further improved, and it is possible to maintain a better lubrication state.

[0067] In addition, the lubricating oil composition of the present invention preferably has a NOACK evaporation loss at 250°C of 21.0% by mass or less (more preferably 13.8% by mass or less). The lower limit of the NOACK evaporation loss of the lubricating oil composition at 250°C is not particularly limited, but it is preferably 3% by mass or more. Note that in this specification, the "NOACK evaporation loss at 250°C" is the evaporation loss of the lubricating oil composition at 250°C measured in accordance with ASTM D 5800. When the NOACK evaporation loss is 21.0% by mass or less, the loss of the composition due to evaporation during use is reduced, and it is possible to suppress oil consumption at a high level.

[0068] In addition, due to its properties, the lubricating oil composition of the present invention can be particularly suitably used for lubricating and cooling a transmission and an electric motor. That is, the lubricating oil composition of the present invention has a well-balanced low traction coefficient, high low-temperature fluidity, and high oil consumption suppression performance, and thus can be particularly suitably used for applications such as lubricating and / or cooling a transmission and / or an electric motor.

Examples

[0069] Hereinafter, the present invention will be described more specifically based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[0070] First, the base oils and additives used in each Example etc. are described below. In each Example etc., the following base oils (I-1) to (I-12) were prepared and used respectively. Here, base oils (I-1) to (I-3) correspond to the "base oil (A)" according to the present invention, and base oils (I-9) to (I-12) correspond to the "base oil (B)" according to the present invention. Also, although base oils (I-4) to (I-6) are composed of polymers of 1-tetradecene, they do not correspond to the "base oil (A)" according to the present invention from the viewpoint of the mass ratio of the dimer and trimer of 1-tetradecene.

[0071] 〔I〕Regarding base oils [Base oil (I-1)] A base oil which is a polymer of 1-tetradecene having the composition shown in Table 1 [Base oil (I-2)] A base oil which is a polymer of 1-tetradecene having the composition shown in Table 1 [Base oil (I-3)] A base oil which is a polymer of 1-tetradecene having the composition shown in Table 1 [Base oil (I-4)] A base oil which is a polymer of 1-tetradecene having the composition shown in Table 1 [Base oil (I-5)] A base oil which is a polymer of 1-tetradecene having the composition shown in Table 1 [Base oil (I-6)] A base oil which is a polymer of 1-tetradecene having the composition shown in Table 1 [Base oil (I-7)] A base oil which is a polymer of 1-dodecene having the composition shown in Table 1 (API base oil classification: Group IV) [Base oil (I-8)] Base oil which is a polymer of 1-decene having the composition shown in Table 1 (API base oil classification: Group IV) [Base oil (I-9)] Hydrocracked mineral oil base oil (manufactured by SK Lubricants Co., Ltd., trade name "Yubase® 4+", API base oil classification: Group III) [Base oil (I-10)] Hydrocracked base oil of GTL wax (GTL3: API base oil classification: Group II) [Base oil (I-11)] Hydrocracked base oil of GTL wax (GTL4: API base oil classification: Group III) [Base oil (I-12)] Hydrocracked mineral oil base oil (manufactured by SK Lubricants Co., Ltd., trade name "Yubase® 6+", API base oil classification: Group III).

[0072]

Table 1

[0073] [II] Regarding additives [Additive package] Ashless dispersant (mixture of non-boronated succinimide and boronated succinimide); metallic detergent (calcium sulfonate, total base number: 300 (TBN300), calcium concentration: 12% by mass); antioxidant (mixture of amine-based antioxidant and phenolic antioxidant); antiwear agent (phosphite ester); metal deactivator (thiadiazole); rubber swelling agent (sulfolane compound); and additive package containing diluent oil [Pour point depressant] Polymethacrylate (non-dispersible, weight average molecular weight: 56,000).

[0074] (Examples 1 to 6. Reference Example 1 and Comparative Examples 1 to 7) A lubricating oil composition was prepared by appropriately selecting components from the aforementioned base oil [I] and additive [II] so as to have the compositions shown in Tables 2 to 4 below. In each of the examples and the like, as the lubricating oil base oil, a mixture of two or three types of base oils selected from the base oils described in base oil [I] and mixed at the ratios described in Tables 2 to 4 was used. Here, in Tables 2 to 4, the unit "inmass%" of the content of the lubricating oil base oil represents the content (mass%) of each base oil with respect to the total amount of the lubricating oil base oil, and the unit "mass%" of the content of the additive represents the content (mass%) of each component with respect to the total amount of the lubricating oil composition. Also, in Tables 2 to 4, C14 dimer indicates the dimer of 1-tetradecene, C14 trimer indicates the trimer of 1-tetradecene, C14 tetramer indicates the tetramer of 1-tetradecene, the C14 dimer is sometimes indicated as component (A1), and the C14 trimer is sometimes indicated as component (A2). Also, regarding the compositions in Tables 2 to 4, "-" indicates that the component is not used. In Comparative Examples 3 to 7, base oils (I-4) to (I-8) are used as base oils for comparison with "base oil (A)". From the perspective of comparison with such base oil (A) (comparison with base oils (I-1) to (I-3)), for convenience, in Table 4, base oils (I-4) to (I-8) are sometimes denoted as "base oil (C)".

[0075] Also, Tables 2 to 4 also show the kinematic viscosities of each lubricating oil base oil (a mixture of two or three types of base oils selected from base oils (I-1) to (I-12)) at 40°C and 100°C. The kinematic viscosities of the lubricating oil base oils shown in Tables 2 to 4 at each temperature are values measured using an automatic viscometer (trade name "CAV-2100", manufactured by Cannon Instrument Co., Ltd.) as the measuring device in accordance with JIS K2283-2000. Also, Tables 2 to 4 also show the viscosity indexes of the lubricating oil base oils. The viscosity indexes of the lubricating oil base oils are values measured in accordance with JIS K 2283-2000.

[0076] [Evaluation method for the properties of the lubricating oil compositions obtained in each example, etc.] <Measurement of traction coefficient> The traction coefficients of the lubricating oil compositions obtained in each example etc. were measured under the conditions of temperature: 25 °C, load: 20 N, peripheral speed (average speed): 0.5 m / s, and slip ratio (SRR): 3% using an EHL tester (tester "EHD2" manufactured by PCS Instruments) and using a steel disk and a steel ball as members. The results obtained are shown in Tables 2 to 4. When the traction coefficient is 0.0054 or less, it can be said that it is at a high level from the viewpoint of a low traction coefficient (it can be said that the traction coefficient is sufficiently low).

[0077] <Measurement of Brookfield viscosity (BF viscosity)> The BF viscosity at -40 °C of the lubricating oil compositions obtained in each example etc. was measured under the condition of temperature: -40 °C using a thermostatic bath for Brookfield viscosity / Brookfield viscometer as a measuring device in accordance with ASTM D 2983. The results obtained are shown in Tables 2 to 4. When the value of the BF viscosity is 10,000 mPa·s or less, it can be said that the fluidity at low temperature is at a high level.

[0078] <Measurement of kinematic viscosity of lubricating oil composition> Regarding the lubricating oil compositions obtained in each example etc., the kinematic viscosity at 40 °C and the kinematic viscosity at 100 °C were measured in accordance with JIS K2283-2000 and using an automatic viscometer (trade name "CAV-2100", manufactured by Cannon Instrument) as a measuring device. The results obtained are shown in Tables 2 to 4.

[0079]

Table 2

[0080]

Table 3

[0081]

Table 4

[0082] As is clear from Tables 2 to 4, a base oil corresponding to base oil (A) (a base oil containing component (A1) which is a dimer of 1-tetradecene and component (A2) which is a trimer of 1-tetradecene in a mass ratio ([component (A1)] / [component (A2)]) of 3 to 10) is contained in a proportion of 40% by mass or more and 75% by mass or less, and a base oil corresponding to base oil (B) is contained in a proportion of 25% by mass or more and 60% by mass or less. The lubricating oil base oil contains the lubricating oil compositions obtained in Examples 1 to 6 and Reference Example 1 All of the lubricating oil compositions obtained in Examples 1 to had a traction coefficient of 0.0054 or less and a BF viscosity of 10,000 mPa·s or less. Also, Examples 1 to 6 and Reference Example 1 All of the lubricating oil compositions obtained in Examples 1 to had a kinematic viscosity of the composition in the range of 8 to 30 mm 2 / s. Since the kinematic viscosity at 40°C is within the above range, all of the lubricating oil compositions obtained in Examples 1 to 6 and Reference Example 1 are clearly excellent in power transmission efficiency, wear resistance, and extreme pressure (load-carrying capacity) during use, particularly in a relatively low-temperature range near 40°C (preferably about 20 to 60°C).

[0083] On the other hand, even when using a base oil corresponding to base oil (A), when its content exceeded 75% by mass (Comparative Example 1), the BF viscosity exceeded 1,000,000 mPa·s, and the low-temperature fluidity was low. Also, even when using a base oil corresponding to base oil (A), when its content was less than 40% by mass (Comparative Example 2), the traction coefficient was a value greater than 0.0054, and it was not sufficient in terms of a low traction coefficient. Furthermore, when using a base oil which is a polymer of 1-dodecene (API base oil classification: Group IV) instead of base oil (A) (Comparative Example 3), the traction coefficient was a value greater than 0.0054, and in this case as well, it was not sufficient in terms of a low traction coefficient. Also, when using a base oil which is a polymer of 1-decene (API base oil classification: Group IV) instead of base oil (A) (Comparative Example 4), the kinematic viscosity of the composition at 40°C was 8 mm 2It was less than / s. Therefore, when a base oil (API base oil classification: Group IV) which is a polymer of 1-decene is used instead of the base oil (A) (Comparative Example 4), it is clear that excellent anti-wear properties and extreme pressure properties cannot be exhibited during use, particularly in a relatively low temperature range near 40°C (preferably about 20 to 60°C). Further, when a base oil in which the mass ratio ([component (A1)] / [component (A2)]) of the component (A1) and the component (A2) is less than 3 is used instead of the base oil (A) (Comparative Example 5), the traction coefficient is a value greater than 0.0054, and it is not sufficient in terms of a low traction coefficient. Also, the lubricating oil compositions obtained in Comparative Examples 6 and 7 are combined with the lubricating oil composition obtained in Example 1 in terms of the kinematic viscosity at 40°C. However, in the lubricating oil compositions obtained in Comparative Examples 6 and 7, a base oil in which the mass ratio ([component (A1)] / [component (A2)]) of the component (A1) and the component (A2) is 19.0 (a base oil in which the mass ratio exceeds 10) is used instead of the base oil (A), and particularly, it is not sufficient in terms of a low traction coefficient.

[0084] From such results, it has been found that the lubricating oil composition of the present invention can have a low traction coefficient and high low-temperature fluidity in a well-balanced manner while setting the kinematic viscosity at 40°C to an appropriate level.

Industrial Applicability

[0085] As described above, according to the present invention, it is possible to provide a lubricating oil composition that can have a low traction coefficient and high low-temperature fluidity in a well-balanced manner while setting the kinematic viscosity at 40°C to an appropriate level. Therefore, the lubricating oil composition of the present invention is particularly useful as a composition for use in applications such as lubricating oils and cooling oils for devices such as transmissions, electric motors, and integrated devices thereof.

Claims

1. The following base oils (A) and (B): (A) A poly-α-olefin base oil which is a polymer of 1-tetradecene, (B) A hydrocracked mineral oil base oil which is a Group III base oil in the API base oil classification; a hydrocracked base oil of GTL wax which is a Group II base oil in the API base oil classification; and a hydrocracked base oil of GTL wax which is a Group III base oil in the API base oil classification; at least one mineral oil base oil selected from the group consisting of, A composition comprising a lubricating oil base oil containing, The base oil (A) contains a component (A1) which is a dimer of 1-tetradecene and a component (A2) which is a trimer of 1-tetradecene, The mass ratio ([component (A1)] / [component (A2)]) of the components (A1) and (A2) contained in the base oil (A) is 3 to 10, Based on the total amount of the lubricating oil base oil, the content of the base oil (A) is 60% by mass or more and 75% by mass or less, Based on the total amount of the lubricating oil base oil, the content of the base oil (B) is 25% by mass or more and 40% by mass or less, Based on the total amount of the lubricating oil base oil, the total amount of the base oil (A) and the base oil (B) is 80% by mass or more, and The kinematic viscosity of the composition at 40 °C is 8 to 30 mm ２ / s, A lubricating oil composition characterized by the above.

2. The lubricating oil composition according to claim 1, characterized in that the total amount of the components (A1) and (A2) is 90% by mass or more based on the total amount of the base oil (A).

3. The lubricating oil composition according to claim 1 or 2, further comprising a poly(meth)acrylate pour point depressant.

4. The lubricating oil composition according to any one of claims 1 to 3, further comprising an anti-friction agent composed of a (sub)phosphoric acid ester.

5. The lubricating oil composition according to any one of claims 1 to 4, which is used for lubricating and / or cooling a transmission and / or an electric motor.

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