JP7393938B2 - lubricating oil composition - Google Patents

Description

The present invention relates to a lubricating oil composition containing a low viscosity base oil containing a specific amount of a fraction with a specific boiling point range and a specific copolymer.

In recent years, in order to reduce CO ₂ emissions and protect oil resources, there has been an increasing demand for fuel efficiency in automobiles. One way to save fuel is, for example, by lowering the viscosity of engine oil to reduce viscous resistance. However, lowering the viscosity causes problems such as liquid leakage and seizure. Also, in cold regions, low-temperature startability is required. To address this problem, the viscosity standard for engine oils (SAE J300) of SAE in the United States is stipulated, and for 0W-20 grade, the HTHS viscosity at 150°C under high temperature and high shear (ASTM D4683 or D5481) is the minimum. ．． 2.6. In addition, this grade is specified to have a low-temperature viscosity of 60,000 mPa·s or less at -40°C and no yield stress (ASTMD4684) to ensure startability in cold regions.

Regarding fuel efficiency, there is a need for an engine oil that satisfies the above standards and has a lower HTHS viscosity in the effective temperature range of 80°C or 100°C, and various viscosity index improvers have been proposed. Further fuel efficiency by lowering the viscosity of lubricating oil compositions is required not only for engine oils but also for driving oil lubricating oil compositions. On the other hand, hybrid cars and electric cars are rapidly becoming popular in order to reduce _CO2 emissions and protect oil resources. In particular, with the spread of hybrid vehicles, the frequency of engine operation is decreasing and the frequency of driving at low oil temperatures is increasing. Therefore, while reducing viscosity on the low temperature side is important for improving fuel efficiency, reliability on the high temperature side is also required from the viewpoint of reliability during high speed operation, etc., although this is less frequent. Therefore, it is necessary to ensure an appropriately high viscosity even at high temperatures (Patent Documents 1 to 3).

Japanese Patent Application Publication No. 2013-147608 Re-publication No. 2015-129732 JP2017-57378A

However, the viscosity of conventional lubricating base oils increases at low temperatures. There are limits to reducing low-temperature viscosity and ensuring relatively high viscosity at high temperatures. The present invention aims to reduce fuel consumption by creating a lubricating oil composition that reduces low-temperature viscosity, ensures relatively high viscosity at high temperatures, and has a small difference between viscosity at low temperatures and viscosity at high temperatures. The purpose is to provide something.

The present invention suppresses the increase in viscosity at extremely low temperatures (hereinafter referred to as extremely low temperatures) and has a small viscosity difference over a wider temperature range, that is, at low temperatures (e.g. 40°C) and extremely low temperatures (e.g. 0°C). An object of the present invention is to provide a lubricating oil composition that suppresses viscosity increase and maintains a relatively high viscosity equivalent to conventional products at high temperatures (for example, 100° C. or higher).

As a result of extensive studies, the present inventors have determined that a specific amount of a (co)polymer (B) having a main chain having a repeating unit derived from a polymerizable monomer and a side chain having a polyolefin structure is used as a viscosity index improver. By blending and containing 20 to 60% by mass of a fraction with a boiling point in the range of 350°C to 400°C based on the total mass of the lubricating oil composition, it can be used at low temperatures (for example, 40°C) and extremely low temperatures ( For example, the increase in viscosity is suppressed at low temperatures (e.g., 0°C), and at high temperatures (e.g., 100°C), a relatively high viscosity equivalent to that of conventional products can be ensured, and the difference between the viscosity at extremely low temperatures and at high temperatures is relatively small. It has been discovered that a lubricating oil composition can be provided. The present invention particularly relates to a lubricating oil composition having a NOACK evaporation amount of 15% by mass or more and less than 25% by mass.

That is, the present invention provides a lubricating oil composition comprising (A) a base oil and (B) a (co)polymer, and having a NOACK evaporation amount of 15% by mass or more and less than 25% by mass, wherein the component (B) is It is a (co)polymer having a main chain having a repeating unit derived from a polymerizable monomer and a side chain having a polyolefin structure, and the amount of the component (B) is from 0.5 to the total mass of the lubricating oil composition. The lubricating oil composition is characterized in that it contains a fraction having a boiling point of 10% by mass and a boiling point in the range of 350°C to 400°C in an amount of 20% to 60% by mass based on the total mass of the lubricating oil composition. provide something.

In a preferred embodiment of the present invention, the lubricating oil composition further has at least one of the following characteristics (1) to (11).
(1) A fraction having a boiling point in the range of over 400°C to 450°C is contained in an amount of 10 to 70% by mass based on the total mass of the lubricating oil composition.
(2) It does not contain a fraction whose boiling point is above 600°C derived from the base oil (A).
(3) The content of a fraction having a boiling point of less than 350°C is 10% by weight or less.
(4) As the base oil (A), (A1) a base oil containing 50 to 99% by mass of a fraction with a boiling point in the range of 350 to 400°C, and (A2) a base oil with a boiling point in the range of more than 400 to 450°C Contains a base oil containing 40 to 90% by mass of a fraction within the range, the content of component (A1) is 20 to 70% by mass with respect to the total mass of the lubricating oil composition, and the content of component (A2) is 20 to 70% by mass is 25 to 75% by mass.
(5) The (B) (co)polymer has a unit derived from a compound having a polyolefin structure having 50 to 1,000 carbon atoms at one end and a (meth)acryloxy group at the other end. (co)polymer (B-1) having a solubility parameter (SP value) of 9.1 to 9.5 (cal/cm ³ ) ^1/2. have
(6) The (B) (co)polymer is
(i) a repeating unit derived from a polyolefin-based macromonomer;
(ii) styrene monomers with 8 to 17 carbon atoms, alkyl (meth)acrylates with 1 to 10 carbon atoms in the alcohol group, vinyl esters with 1 to 11 carbon atoms in the acyl group, Vinyl ethers with 1 to 10 carbon atoms in the alcohol group, (di)alkyl fumarates with 1 to 10 carbon atoms in the alcohol group, (di)alkyl fumarates with 1 to 10 carbon atoms in the alcohol group, ) alkyl maleate, and a repeating unit derived from a low molecular monomer (hereinafter simply referred to as a low molecular monomer) selected from the group consisting of a mixture of these monomers, ,
The degree of molar branching is within the range of 0.1 to 10 mol%,
A total of at least 80% by mass of the (i) repeating unit derived from a polyolefin-based macromonomer and the (ii) repeating unit derived from a low molecular monomer, based on the mass of the repeating unit,
The comb-shaped polymer (B-2) is characterized by containing 8 to 30% by mass of repeating units derived from the polyolefin-based macromonomer (i).
(7) The base oil (A) has a kinematic viscosity of 2.0 to 5.0 mm ² /s at 100°C.
(8) The base oil (A) is mineral oil and/or GTL.
(9) A lubricating oil composition further containing at least one additive selected from metal detergents, friction modifiers, antioxidants, and antiwear agents.
(10) A lubricating oil composition for internal combustion engines.
(11) A lubricating oil composition for hybrid vehicles.

The lubricating oil composition of the present invention can maintain relatively high viscosity at high temperatures and reduce low-temperature viscosity over a wide temperature range. More specifically, it suppresses viscosity increase at low temperatures (e.g. 40°C) and extremely low temperatures (e.g. 0°C), and maintains a relatively high viscosity equivalent to conventional products at high temperatures (e.g. 100°C). , it is possible to provide a lubricating oil composition in which the difference between the low-temperature viscosity and the high-temperature viscosity is relatively small. By having a low viscosity difference over a wide temperature range, fuel efficiency can be improved.

FIG. 1 is a graph (solid line) showing the difference between the kinematic viscosity at 0°C and the kinematic viscosity at 100°C for the lubricating oil compositions of Examples 1, 2, and 7, and the lubricating oil compositions of Comparative Examples 1, 9, and 11. A graph (dotted line) showing the difference between the kinematic viscosity at 0°C and the kinematic viscosity at 100°C for a substance is shown.

The present invention is characterized in that it contains (A) a base oil, and (B) a (co)polymer having a main chain having a repeating unit derived from a polymerizable monomer and a side chain having a polyolefin structure. It is a lubricating oil composition having 15% by mass or more and less than 25% by mass. The NOACK evaporation amount is more preferably 16 to 24% by mass, still more preferably 18 to 23% by mass, and particularly preferably 20 to 22% by mass. The lubricating oil composition contains 20 to 60% by mass of a fraction having a boiling point in the range of 350°C to 400°C based on the total mass of the lubricating oil composition, and the above ( The content of component B) is 0.5 to 10% by mass based on the total weight of the lubricating oil composition. As a result, an increase in viscosity at low temperatures can be suppressed, and a relatively high viscosity equivalent to that of conventional products can be maintained even at high temperatures. Preferably, the lubricating oil composition of the present invention has a kinematic viscosity of 10 to 60 mm ² /s at 40°C and a kinematic viscosity of 5 to 22 mm ² /s at 100°C. More preferably, the lubricating oil composition of the present invention has a kinematic viscosity of 10 to 30 mm ² /s at 40°C and a kinematic viscosity of 5 to 12 mm ² /s at 100°C. In the present invention, the NOACK evaporation amount is a value measured at 250° C. for 1 hour in accordance with ASTM D 5800.

In the above (co)polymer, the main chain has a polar structure, whereas the side chain polyolefin structure has a non-polar structure. At low temperatures, the main chain structure of the (co)polymer is aggregated and dispersed in the base oil, making it possible to suppress an increase in the viscosity of the base oil. Furthermore, when the temperature rises to high temperature (for example, 100° C.), the main chain structure of the (co)polymer is unraveled, making it possible to maintain the conventional base oil viscosity. As a result, it is possible to reduce the viscosity of the lubricating oil composition at low temperatures (for example, 40°C) while ensuring a relatively high viscosity at high temperatures (for example, 100°C). The difference between the viscosity and the viscosity of the lubricating oil composition at high temperatures can be reduced.

The distillation properties of the lubricating oil composition of the present invention will be explained in detail below.
(1) The content of the fraction having a boiling point in the range of 350°C to 400°C is 20 to 60% by mass, preferably 21 to 55% by mass, more preferably 22 to 52% by mass, based on the total mass of the lubricating oil composition. % by weight, more preferably 24-48% by weight, particularly preferably 25-45% by weight. If it exceeds the above upper limit, oil consumption may increase or cleanliness may deteriorate, and if it is less than the above lower limit, fuel efficiency may deteriorate, which is not preferable.
(2) The content of the fraction having a boiling point in the range of over 400°C to 450°C is preferably 10 to 70% by mass, more preferably 15 to 60% by mass, and more preferably 15 to 60% by mass, based on the total mass of the lubricating oil composition. Preferably it is from 20 to 50% by weight, particularly preferably from 25 to 45% by weight and most preferably from 30 to 40% by weight. If it exceeds the above upper limit, fuel efficiency may deteriorate, and if it is less than the above lower limit, oil consumption may increase or cleanliness may deteriorate, which is not preferable.
(3) The content of the fraction whose boiling point exceeds 450°C is preferably 1 to 30% by mass, more preferably 2 to 25% by mass, and even more preferably 5% by mass based on the total mass of the lubricating oil composition. It is preferably between 10 and 20% by weight, most preferably between 12 and 18% by weight.
(4) (A) It is preferable that a fraction derived from the base oil and having a boiling point exceeding 600°C is not included.
(5) The content of the fraction having a boiling point of less than 350°C is preferably 0 to 10% by mass, more preferably 0.1 to 5% by mass, and even more preferably is preferably 0.2 to 4% by weight, particularly preferably 0.5 to 2% by weight.
(6) The content of the fraction having a boiling point in the range of 370°C to 390°C is preferably 10 to 50% by mass, more preferably 15 to 45% by mass, and even more preferably is 20 to 40% by weight, particularly preferably 22 to 35% by weight, most preferably 25 to 30% by weight.

(A) Base oil The base oil constituting the lubricating oil composition of the present invention can be appropriately selected from conventionally known base oils, and may be mixed in combination so as to satisfy the requirements of the present invention described above. The base oil having a fraction in the above boiling point range can be prepared by using mineral oils or synthetic oils having an appropriate viscosity alone or by using two or more types in combination.

Mineral oils include, for example, lubricating oil fractions obtained by vacuum distillation of atmospheric residual oil obtained by atmospheric distillation of crude oil, solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, and hydrogen or wax isomerized mineral oil, GTL (Gas to Liquid) base oil, ATL (Asphalt to Liquid) base oil, vegetable oil base oil, or a mixture thereof. Base oils may be mentioned.

Examples of synthetic oils include polybutene or its hydride; poly-α-olefin such as 1-octene oligomer and 1-decene oligomer or its hydride; 2-ethylhexyl laurate, 2-ethylhexyl palmitate, and 2-stearate. Monoesters such as ethylhexyl; diesters such as ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate; neopentyl glycol di-2-ethylhexanoate, neopentyl Glycol di-n-octanoate, neopentyl glycol di-n-decanoate, trimethylolpropane tri-n-octanoate, trimethylolpropane tri-n-decanoate, pentaerythritol tetra-n-pentanoate, pentaerythritol tetra-n-hexanoate, Examples include polyol esters such as pentaerythritol tetra-2-ethylhexanoate; aromatic synthetic oils such as alkylnaphthalenes, alkylbenzenes, aromatic esters, and mixtures thereof.

Preferably, the kinematic viscosity of the base oil at 100° C. is 2.0 to 5.0 mm ² /s, more preferably 2.0 to 4.0 mm ² /s, even more preferably 2.3 ~3.8 mm ² /s, more preferably 2.5 to 3.7 mm ² /s, even more preferably 2.7 to 3.6 mm ² /s. As the base oil having low viscosity, the above-mentioned mineral oil, GTL, and synthetic oil can be prepared individually or in appropriate combinations. The viscosity index of the base oil (A) is preferably 100 or more, more preferably 110 or more, and even more preferably 120 or more.

Preferably, the base oil (A) is (A1) a base oil containing 50 to 99% by mass of a fraction with a boiling point in the range of 350 to 400 °C, and (A2) a base oil with a boiling point in the range of more than 400 to 450 °C or less. It is better to use a base oil containing 40 to 90% by mass of a certain fraction, and the content of base oil (A1) is 20 to 70% by mass based on the total amount of the lubricating oil composition, and the base oil ( The content of A2) is preferably 25 to 75% by mass based on the total amount of the lubricating oil composition. By containing component (A1) and component (A2) in amounts within the above range, a lubricating oil composition having distillation properties within the above range can be provided.

Base oil (A1)
The lubricating oil composition of the present invention preferably contains, as the base oil (A), a base oil (A1) containing 50 to 99% by mass of a fraction having a boiling point in the range of 350 to 400°C. In the base oil (A1), the content of the fraction having a boiling point in the range of 350 to 400°C is preferably 55 to 98% by mass, more preferably 60 to 97% by mass, and more preferably 70 to 96% by mass. , particularly preferably 75 to 95% by weight, most preferably 80 to 93% by weight. The content of the base oil (A1) in the lubricating oil composition of the present invention is preferably 20 to 70% by mass, preferably 25 to 60% by mass, and more preferably is 30 to 50% by mass, more preferably 35 to 45% by mass.

Furthermore, the base oil (A1) preferably contains 10 to 80% by mass of a fraction having a boiling point in the range of 370 to 390°C, more preferably 20 to 70% by mass, still more preferably 30 to 60% by mass. It is good to be. Further, the content of the fraction having a boiling point in the range of over 400°C to 450°C is preferably 1 to 50% by mass, more preferably 2 to 40% by mass, even more preferably 3 to 30% by mass, particularly preferably The content is preferably 5 to 20% by mass. The content of the fraction having a boiling point exceeding 450°C is preferably 0 to 5% by mass, more preferably 0 to 3% by mass, even more preferably 0 to 1% by mass, and particularly preferably 0 to 1% by mass. It is preferable that it is mass %. Further, it is preferable that the fraction having a boiling point in a range exceeding 600° C. is 0% by mass. The fraction having a boiling point below 350°C is preferably 0 to 20% by mass, more preferably 1 to 15% by mass, even more preferably 2 to 10% by mass, particularly preferably 3 to 5% by mass. Mass%.

Further, the base oil (A1) preferably has a kinematic viscosity (KV100) of 2.0 to 4.5 mm ² /s at 100°C. More preferably 2.3 to 4.0 mm ² /s, still more preferably 2.5 to 3.7 mm ² /s, still more preferably 2.7 to 3.6 mm ² /s, particularly preferably is preferably 2.9 to 3.5 mm ² /s, most preferably 3.1 to 3.3 mm ² /s. Furthermore, the viscosity index of the base oil (A1) is preferably 100 or more, more preferably 110 or more, and still more preferably 120 or more.

Base oil (A2)
The lubricating oil composition of the present invention preferably further contains, as the base oil (A), a base oil (A2) containing 40 to 90% by mass of a fraction in the range of more than 400°C to 450°C or less. In the base oil (A2), the content of the fraction having a boiling point in the range of over 400°C to 450°C is more preferably 45 to 80% by mass, still more preferably 50 to 75% by mass, and particularly Preferably it is 55 to 70% by weight, most preferably 60 to 65% by weight.
The content of the base oil (A2) in the lubricating oil composition of the present invention is preferably 25 to 75% by mass, more preferably 30 to 70% by mass, and further It is preferably 35 to 65% by weight, particularly preferably 40 to 60% by weight, and most preferably 45 to 55% by weight.

Further, in the base oil (A2), the content of fractions having a boiling point exceeding 450°C is preferably 1 to 40% by mass, more preferably 2 to 38% by mass, and even more preferably 5 to 35% by mass. The content is particularly preferably 10 to 30% by mass. Further, the fraction having a boiling point exceeding 600°C is preferably 0% by mass, and more preferably the fraction having a boiling point exceeding 500°C is 0% by mass. The fraction having a boiling point below 400°C is preferably 0 to 30% by mass, more preferably 1 to 25% by mass, even more preferably 2 to 20% by mass, particularly preferably 5 to 15% by mass. be. Further, the base oil (A2) preferably has a kinematic viscosity (KV100) of 3.1 to 5.0 mm ² /s at 100°C. More preferably 3.3 to 4.8 mm ² /s, still more preferably 3.5 to 4.7 mm ² /s, still more preferably 3.7 to 4.6 mm ² /s, particularly preferably is between 3.9 and 4.5 mm ² /s, most preferably between 4.1 and 4.3 mm ² /s. The viscosity index of the base oil (A2) is preferably 100 or more, preferably 110 or more, and more preferably 120 or more.

Incidentally, the distillation properties of the above base oil and composition can be measured by GCD (distillation gas chromatography). The GCD measurement was performed in accordance with JIS K2254 "Petroleum products - Distillation test method" except that the external standard method was used instead of the total area method.

Generally, when the base oil viscosity is lowered, the NOACK evaporation amount of the lubricating oil composition tends to increase. There is a standard for engine oils that requires NOACK evaporation of a maximum of 15% by mass, and in the past there was a limit to how much base oil viscosity could be lowered to meet this standard. The present invention aims at a lubricating oil composition having a NOACK evaporation amount of 15% by mass or more, particularly a NOACK evaporation amount of 15% by mass or more and less than 25% by mass. The NOACK evaporation amount is more preferably 16 to 24% by weight, still more preferably 18 to 23% by weight, particularly preferably 20 to 22% by weight. As mentioned above, by combining a low viscosity base oil that has a specific amount of a fraction with a specific boiling point range, it becomes easier to adjust the amount of (co)polymer (B) to be added, which will be described later, and it can be used in a wider range. It is possible to find the optimum blending balance that results in a lubricating oil composition with a small viscosity difference.

In order to obtain a lubricating oil composition having a NOACK evaporation amount of 15% by mass or more and less than 25% by mass, at least one of the above-mentioned mineral oil and GTL base oil is preferably required. When mineral oil is included, GTL may be 0% by mass, and when GTL is included, mineral oil may be 0% by mass, but a combination of mineral oil and GTL base oil is particularly preferred. For example, as base oil (A1), GTL of KV100 = 2.0 to 4.5 mm ² /s is used in an amount of 20 to 70% by mass based on the total amount of the lubricating oil composition, and as base oil (A2), KV100 = 3.1 A combination of mineral oil and/or GTL of ~4.5 mm ² /s in an amount of 25 to 75% by mass based on the total amount of the lubricating oil composition is preferred.
More preferably, the base oil (A1) is 25 to 60% by mass of GTL with KV100 = 2.0 to 4.5 mm ² /s based on the total amount of the lubricating oil composition, and the base oil (A2) is KV100 = 3. A combination of mineral oil and/or GTL of .1 to 4.5 mm ² /s in an amount of 30 to 70% by mass based on the total amount of the lubricating oil composition, more preferably KV100 = 2.0 to 4 as the base oil (A1). .5 mm ² /s GTL is 30 to 50% by mass based on the total amount of the lubricating oil composition, and the base oil (A2) is KV100 = 3.1 to 4.5 mm ² /s mineral oil and or GTL as the lubricating oil. A combination of 30 to 65% by mass based on the total amount of the composition, particularly preferably a GTL of KV100 = 2.0 to 4.5 mm ² /s as the base oil (A1) based on the total amount of the lubricating oil composition. 35 to 40% by mass, and 40 to 60% by mass of mineral oil and or GTL with KV100 = 3.1 to 4.5 mm ² /s as base oil (A2) based on the total amount of the lubricating oil composition. Good.

In yet another preferred embodiment, GTL of KV100 = 2.0 to 3.0 mm ² /s is used as the base oil (A1) in an amount of 20 to 50% by mass based on the total amount of the lubricating oil composition, and as the base oil (A2). Mineral oil with KV100 = 3.1 to 4.5 mm ² /s is used as 0 to 70% by mass based on the total amount of the lubricating oil composition, and further as base oil (A2) KV100 = 3.1 to 4.5 mm ² /s The combination of GTL is preferably 10 to 60% by mass based on the total amount of the lubricating oil composition. More preferably, the base oil (A1) is 25 to 45% by mass of GTL with KV100 = 2.0 to 3.0 mm ² /s based on the total amount of the lubricating oil composition, and the base oil (A2) is KV100 = 3.1. 1 to 50% by mass of mineral oil of ~4.5 mm ² /s based on the total amount of the lubricating oil composition, and further GTL of KV100 = 3.1 to 4.5 mm ² /s as the base oil (A2) as a lubricating oil. The combination is preferably 25 to 55% by mass based on the total amount of the composition. Particularly preferably, as the base oil (A1), 30 to 40% by mass of GTL of KV100 = 2.0 to 3.0 mm ² /s is used based on the total amount of the lubricating oil composition, and as the base oil (A2), KV100 = 3.1 10 to 30% by mass of mineral oil of ~4.5 mm ² /s based on the total amount of the lubricating oil composition, and further GTL of KV100 = 3.1 to 4.5 mm ² /s as the base oil (A2) to the lubricating oil. The combination may be 35 to 50% by mass based on the total amount of the composition.

Moreover, the lubricating oil composition of the present invention can appropriately use base oils other than base oil (A1) and base oil (A2) in combination within a range that satisfies the above-mentioned requirements for distillation properties and NOACK evaporation amount. For example, PAO with KV100 = 2.0 to 4.5 mm ² /s is added in an amount of 0 to 80% by mass, preferably 1 to 50% by mass, more preferably 2 to 30% by mass, based on the total amount of the lubricating oil composition. can further include. The NOACK evaporation amount of a lubricating oil composition further comprising such a base oil is preferably 16 to 24% by weight, more preferably 17 to 23% by weight, even more preferably 18 to 23% by weight, and most preferably 19 to 22% by weight. It is preferable that it is mass %.

The viscosity index (VI) of the lubricating base oil is not particularly limited, but is preferably 100 or more, more preferably 120 or more, and most preferably 125 or more. By using a base oil having such a viscosity index, it is possible to reduce the viscosity at low temperatures while ensuring more viscosity at high temperatures, which is preferable.

(B) (co)polymer having a main chain having a repeating unit derived from a polymerizable monomer and a side chain having a polyolefin structure The lubricating oil composition of the present invention contains a predetermined (co)polymer that functions as a viscosity index improver. ) polymer in an amount of 0.5 to 10% by weight, preferably 1.0 to 8% by weight, more preferably 1.5 to 6.0% by weight, most preferably 2% by weight, based on the weight of the entire lubricating oil composition. It is characterized in that it is contained in an amount of .0 to 5.0% by mass. By blending the (co)polymer in an amount within the above range into a composition containing the lubricant base oil (A) as a main component, a lubricant with a small viscosity difference can be used in a wide temperature range from extremely low temperatures to high temperatures. An oil composition can be provided.
In addition, when providing a lubricating oil composition that satisfies SAE30, SAE40, and SAE50 as described below, the (co)polymer is contained in an amount of 0.5 to 10% by mass, preferably 0.5 to 10% by mass based on the mass of the entire lubricating oil composition. The content is preferably 1.0 to 9.0% by weight, more preferably 2.0 to 8.0% by weight, and most preferably 3.0 to 7.5% by weight.

A first embodiment of a given (co)polymer that functions as a viscosity index improver is:
(B1) A (co)polymer having a polyolefin structure having 50 to 1,000 carbon atoms at one end and a unit derived from a compound having a (meth)acryloxy group at the other end, which is soluble. It is a (co)polymer characterized by having a parameter (SP value) of 9.1 to 9.5 (cal/cm ³ ) ^1/2 .

A second embodiment of certain (co)polymers that function as viscosity index improvers is
(B2) A comb-shaped polymer comprising the following (i) and (ii),
(i) a repeating unit derived from a polyolefin-based macromonomer,
(ii) (Alkyl)styrene monomer having 8 to 17 carbon atoms, alkyl (meth)acrylate having an alkyl group having 1 to 10 carbon atoms, vinyl ester having an alkyl group having 1 to 11 carbon atoms in the acyl group, carbon number Vinyl ether having an alkyl group of 1 to 10 carbon atoms, (di)alkyl fumarate having an alkyl group of 1 to 10 carbon atoms, (di)alkyl maleate having an alkyl group of 1 to 10 carbon atoms, and mixtures of these monomers A repeating unit derived from a low molecular monomer selected from the group consisting of (hereinafter simply referred to as a low molecular monomer),
The degree of molar branching is within the range of 0.1 to 10 mol%, and based on the total mass of the repeating units, the repeating units derived from the (i) polyolefin-based macromonomer and the (ii) low-molecular monomer The above-mentioned comb-shaped polymer is characterized in that it contains a total of at least 80% by mass of repeating units derived from the (i) polyolefin-based macromonomer, and 8 to 30% by mass of repeating units derived from the polyolefin-based macromonomer (i).
Each copolymer will be explained in detail below.

(B1) A (co)polymer having a polyolefin structure having 50 to 1,000 carbon atoms at one end and a unit derived from a compound having a (meth)acryloxy group at the other end. The combination is characterized by having a polyolefin structure having 50 to 1,000 carbon atoms. The polyolefin structure having 50 to 1,000 carbon atoms is a long-chain nonpolar structure. By having this structure, the main chain structure of the (co)polymer is held together at low temperatures (for example, 40°C) and dispersed in the base oil, making it possible to suppress an increase in the viscosity of the base oil. . Furthermore, when the temperature rises to high temperature (for example, 100° C.), the main chain structure of the (co)polymer is unraveled, making it possible to maintain the conventional base oil viscosity. As a result, it is possible to reduce the viscosity of the base oil at low temperatures (for example, 40 °C) while ensuring a relatively high viscosity at high temperatures (for example, 100 °C). Differences in oil viscosity can be reduced.

In the above, "(meth)acrylic" means methacrylic or acrylic. A compound having a polyolefin structure with 50 to 1,000 carbon atoms at one end and a (meth)acryloxy group at the other end is, for example, a compound in which the polyolefin structure and (meth)acryloxy structure have an amide bond or an ether bond. They just need to be connected by the skeleton they have. For example, hydroxyl group-containing hydrocarbon (co)polymers obtained by introducing hydroxyl groups into a hydrocarbon polymer (polyolefin) (e.g., hydroxyl group-containing polymers obtained by introducing hydroxyl groups into hydrogenated polybutadiene and polybutene, etc.), and (meth)acrylic acid. A monomer obtained by an esterification reaction of , and an amino group-containing (co)polymer obtained by introducing an amino group into a hydrocarbon polymer (polyolefin), and an amidation reaction of (meth)acrylic acid. Examples include the body. The number of hydroxyl groups and amino groups in these hydrocarbon polymers (polyolefins) is preferably one from the viewpoint of HTHS viscosity and viscosity index.

As mentioned above, the polyolefin structure has 50 to 1,000 carbon atoms. It preferably has 100 to 900 carbon atoms, more preferably 200 to 800 carbon atoms, and still more preferably 300 to 700 carbon atoms. The polyolefin structure having 50 to 1,000 carbon atoms is, for example, a structure obtained by polymerizing monomers selected from the following (1) to (3). The polyolefin may have a block polymer. When the polyolefin structure has double bonds, part or all of the double bonds may be hydrogenated by hydrogenation.
(1) Aliphatic unsaturated hydrocarbons [olefins having 2 to 36 carbon atoms (e.g., ethylene, propylene, isobutene, 1-butene, 2-butene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, tricosene, etc.) , dienes having 2 to 36 carbon atoms (for example, 1,2-butadiene, 1,3-butadiene, isoprene, 1,4-pentadiene, 1,5-hexadiene, and 1,7-octadiene, etc.)]
(2) Alicyclic unsaturated hydrocarbons [e.g. cyclohexene, (di)cyclopentadiene, pinene, limonene, indene, vinylcyclohexene, ethylidenebicycloheptene, etc.]
(3) Unsaturated hydrocarbons containing aromatic groups (e.g. styrene, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, ethylstyrene, isopropylstyrene, butylstyrene, phenylstyrene, cyclohexylstyrene, benzylstyrene, crotyl) benzene, vinylnaphthalene, divinylbenzene, divinyltoluene, divinylxylene, trivinylbenzene, etc.).
Among these, from the viewpoint of HTHS viscosity and viscosity index, aliphatic unsaturated hydrocarbons are preferred, olefins having 2 to 36 carbon atoms and dienes having 2 to 36 carbon atoms are more preferred, and even more preferred are olefins having 2 to 36 carbon atoms. They are olefins having 2 to 16 carbon atoms and dienes having 2 to 10 carbon atoms, and structures formed by polymerizing isobutene, 1-butene, 2-butene, or 1,3-butadiene are particularly preferred.

A compound having a polyolefin structure having 50 to 1,000 carbon atoms at one end and a (meth)acryloxy group at the other end preferably has a number average molecular weight (hereinafter referred to as Mn) from the viewpoint of shear stability and HTHS viscosity. abbreviated) 1,000 to 20,000, more preferably 1,500 to 15,000, particularly preferably 2,000 to 10,000, most preferably 2,500 to 8 ,000.
In the present invention, the number average molecular weight (Mn) and weight average molecular weight (Mw) of the copolymer can be measured by gel permeation chromatography under the following conditions. The number of carbon atoms in the polyolefin structure at one end was determined by dividing the number average molecular weight by the molecular weight of _CH2 , which was 14.
<Measurement conditions for Mn of polyolefin monomer and Mw of copolymer>
Device: “HLC-802A” [manufactured by Tosoh Corporation]
Column: 2 “TSK gel GMH6” [manufactured by Tosoh Corporation] Measurement temperature: 40°C
Sample solution: 0.5% by weight tetrahydrofuran solution Solution injection volume: 200μl
Detection device: Refractive index detector Reference material: 12 points of standard polystyrene (TSK standard POLYSTYRENE) (molecular weight: 500, 1,050, 2,800, 5,970, 9,100, 18,100, 37,900, 96,400 , 190,000, 355,000, 1,090,000, 2,890,000) [manufactured by Tosoh Corporation]

（式（１）において、Ｒ^１は水素原子又はメチル基であり、－Ｘ^１－は、－Ｏ－、－Ｏ（ＡＯ）ｍ－又は－ＮＨ－であり、Ａは、互いに独立に、炭素数２～４のアルキレン基であり、ｍは０～１０の整数であり、Ａが２以上の互いに異なるアルキレン基である場合に（ＡＯ）で示される単位はランダムに結合していてもブロック結合を形成していてもよく、Ｒ^２はイソブチレン及び／又は１，２－ブチレンを構成単位として含むポリオレフィンの残基であり、及び、ｐは０又は１の数である）。 (a) Preferably, the compound having a polyolefin structure and a (meth)acryloxy group is a compound represented by the following general formula (1) (hereinafter referred to as monomer (a)).

(In formula (1), R ¹ is a hydrogen atom or a methyl group, -X ¹ - is -O-, -O(AO)m- or -NH-, and A is independently a carbon When the number of alkylene groups is 2 to 4, m is an integer of 0 to 10, and A is 2 or more different alkylene groups, the units represented by (AO) are block bonds even if they are bonded randomly. , R ² is a residue of a polyolefin containing isobutylene and/or 1,2-butylene as a constituent unit, and p is a number of 0 or 1).

R ¹ in general formula (1) is a hydrogen atom or a methyl group. Among these, methyl group is preferred from the viewpoint of HTHS viscosity in the effective temperature range.

-X ¹ - in general formula (1) is -O-, -O(AO) _m - or NH-.
A is an alkylene group having 2 to 4 carbon atoms. Examples of the alkylene group having 2 to 4 carbon atoms include ethylene group, 1,2- or 1,3-propylene group, and 1,2-, 1,3- or 1,4-butylene group. m is an integer of 0 to 10, preferably an integer of 0 to 4, more preferably an integer of 0 to 2, from the viewpoint of HTHS viscosity in the effective temperature range. When m is 2 or more, A may be the same or different, and when A is 2 or more different alkylene groups, (AO) _{the m} portion may be a random bond or a block bond. Among -X ¹ -, -O- and -O(AO) _m - are preferred from the viewpoint of HTHS viscosity in the effective temperature range, and -O- and -O(CH ₂ CH ₂ O )-.

In general formula (1), p is a number of 0 or 1.

R ² in the general formula (1) is a residue of a polyolefin containing isobutylene and/or 1,2-butylene as a constituent unit. Examples of polyolefins containing isobutylene and/or 1,2-butylene as constituent units include polymers containing isobutene, 1-butene and 2-butene as constituent monomers, and 1,2-butane polymerized with 1,3-butadiene. Examples include polymers in which the terminal double bonds of adducts are hydrogenated. The polyolefin may be a block polymer or a random polymer. The polyolefin containing isobutylene and/or 1,2-butylene as a constituent unit may further contain constituent units other than isobutylene and/or 1,2-butylene. Constituent monomers include (1) aliphatic unsaturated hydrocarbons, (2) alicyclic unsaturated hydrocarbons, and (3) aromatic group-containing unsaturated hydrocarbons, excluding isobutene, 1-butene, and 2-butene. Examples include saturated hydrocarbons. When the polyolefin has double bonds, part or all of the double bonds may be hydrogenated by hydrogenation.

Based on the total number of constituent units of the polyolefin, from the viewpoint of HTHS viscosity, viscosity index, and shear stability, the total amount of isobutylene and/or 1,2-butylene is preferably 30 mol% or more, more preferably 40 mol% or more. , particularly preferably 50 mol% or more, most preferably 60 mol% or more.

Based on the total number of structural units of the polyolefin, the total of isobutylene and 1,2-butylene can be determined by analyzing the hydrocarbon polymer by C-nuclear magnetic resonance spectrum and calculating using the following formula (1). can. In the 13C-nuclear magnetic resonance spectrum, the peak derived from the methyl group of isobutylene is an integral value of 30-32 ppm (integral value A), and the branched methylene group of 1,2-butylene (-CH ₂ -CH (CH ₂ CH ₃ ) -) appears in the integral value of 26-27 ppm (integral value B). It can be determined from the integral value of the above-mentioned peak and the integral value (integral value C) regarding the total carbon peak of the hydrocarbon polymer.

The monomer (a) represented by the general formula (1) is a hydroxyl group-containing (co)polymer obtained by introducing a hydroxyl group into a polyolefin, or an amino group-containing (co)polymer obtained by introducing an amino group into a polyolefin, and (meta) It can be obtained by an esterification reaction or an amidation reaction with acrylic acid.

Specific examples of the hydroxyl group-containing (co)polymers and amino group-containing (co)polymers (Y) include the following hydroxyl group-containing copolymers (Y1) to (Y4) and amino group-containing (co)polymers (Y5). ).
Alkylene oxide adduct (Y1); the above (1) aliphatic unsaturated hydrocarbon, (2) alicyclic unsaturated hydrocarbon, and (3) aromatic group-containing unsaturated hydrocarbon (for example, an olefin having 2 to 36 carbon atoms) etc.) etc.) in the presence of an ionic polymerization catalyst (sodium catalyst, etc.) to a polyolefin obtained by adding alkylene oxide (ethylene oxide, propylene oxide, etc.).
Hydroboronated product (Y2); hydroboration reaction product of a hydrocarbon polymer (for example, as described in US Pat. No. 4,316,973), etc.
Maleic anhydride-ene-amino alcohol adduct (Y3); one obtained by imidizing the reaction product obtained by the ene reaction between a hydrocarbon polymer having a double bond and maleic anhydride with amino alcohol, etc. .
Hydroformyl-hydride (Y4): one obtained by hydroformylating a hydrocarbon polymer having double bonds and then hydrogenating it (for example, the one described in JP-A-63-175096).
Maleic anhydride-ene-ethylenediamine adduct (Y5): one obtained by imidizing a reaction product obtained by an ene reaction between a hydrocarbon polymer having a double bond and maleic anhydride with ethylenediamine, etc.
Among (Y), (Y1), (Y2) and (Y3) are preferred from the viewpoint of HTHS viscosity and viscosity index, and (Y1) is more preferred.

The number average molecular weight of the hydroxyl group-containing (co)polymer and the amino group-containing (co)polymer (Y) is preferably 1,000 to 20,000, more preferably 1,000 to 20,000 from the viewpoint of shear stability and HTHS viscosity. ,500 to 15,000, particularly preferably 2,000 to 10,000, most preferably 2,500 to 8,000.

（式（２）において、Ｒ^３は、水素原子又はメチル基であり、－Ｘ^２－は－Ｏ－又は－ＮＨ－であり、Ｒ^４は、互いに独立に、炭素数２～４のアルキレン基であり、Ｒ^５は、炭素数１～８のアルキル基であり、ｑは１～２０の整数であり、Ｒ^４が２以上の互いに異なるアルキレン基である場合に（Ｒ^４Ｏ）で示される単位はランダムに結合していてもブロック構造を有してもよい）。 Component (B1) of the present invention preferably includes a unit derived from the above-mentioned monomer (a) and (b) a unit derived from a compound having an alkyl(poly)oxyalkylene structure and a (meth)acryloxy group. A copolymer having the following is preferable. The compound having an alkyl(poly)oxyalkylene structure and a (meth)acryloxy group (hereinafter referred to as monomer (b)) is preferably represented by the following general formula (2).

(In formula (2), R ³ is a hydrogen atom or a methyl group, -X ² - is -O- or -NH-, and R ⁴ is independently an alkylene group having 2 to 4 carbon atoms. , R ⁵ is an alkyl group having 1 to 8 carbon atoms, q is an integer of 1 to 20, and when R ⁴ is 2 or more different alkylene groups, it is represented by (R ⁴ O) The units may be randomly connected or have a block structure).

R ³ in general formula (2) is a hydrogen atom or a methyl group. Among these, methyl group is preferred from the viewpoint of viscosity index.

-X ² - in general formula (2) is -O- or -NH-. Among these, -O- is preferred from the viewpoint of viscosity index.

R ⁴ in general formula (2) is an alkylene group having 2 to 4 carbon atoms. Examples of the alkylene group having 2 to 4 carbon atoms include ethylene group, isopropylene group, 1,2- or 1,3-propylene group, isobutylene group, and 1,2-, 1,3- or 1,4-butylene group. can be mentioned.

In general formula (2), q is an integer of 1 to 20, preferably an integer of 1 to 5, more preferably an integer of 1 to 2, from the viewpoint of viscosity index and low temperature viscosity.
When q is 2 or more, A may be the same or different, and the (R ⁴ O)q portion may be a random bond or a block bond.

R ⁵ in general formula (2) is an alkyl group having 1 to 8 carbon atoms. From the viewpoint of viscosity index, an alkyl group having 1 to 6 carbon atoms is preferred, an alkyl group having 1 to 5 carbon atoms is more preferred, and an alkyl group having 4 carbon atoms is most preferred. For example, methyl group, ethyl group, n-propyl, isopropyl group, n-butyl group, isobutyl group, t-butyl group, n-heptyl group, isoheptyl group, n-hexyl group, 2-ethylhexyl group, n-pentyl group and n-octyl group.

Examples of the compound represented by the above formula (2) include methoxypropyl (meth)acrylate, methoxybutyl (meth)acrylate, methoxyheptyl (meth)acrylate, methoxyhexyl (meth)acrylate, methoxypentyl (meth)acrylate, Methoxyoctyl (meth)acrylate, Ethoxyethyl (meth)acrylate, Ethoxypropyl (meth)acrylate, Ethoxybutyl (meth)acrylate, Ethoxyheptyl (meth)acrylate, Ethoxyhexyl (meth)acrylate, Ethoxypentyl (meth)acrylate, Ethoxyoctyl (Meth)acrylate, Proxymethyl (meth)acrylate, Proxyethyl (meth)acrylate, Proxypropyl (meth)acrylate, Proxybutyl (meth)acrylate, Proxyheptyl (meth)acrylate, Proxyhexyl (meth)acrylate, Proxypentyl ( meth)acrylate, Proxyoctyl(meth)acrylate, Butoxymethyl(meth)acrylate, Butoxyethyl(meth)acrylate, Butoxypropyl(meth)acrylate, Butoxybutyl(meth)acrylate, Butoxyheptyl(meth)acrylate, Butoxyhexyl(meth)acrylate ) acrylate, butoxypentyl (meth)acrylate, butoxyoctyl (meth)acrylate, and alcohols with 1 to 8 carbon atoms added with 2 to 20 moles of ethylene oxide to butylene oxide, and esters of (meth)acrylic acid, etc. It will be done.
Among the monomers (b), preferred from the viewpoint of viscosity index are ethoxyethyl (meth)acrylate and butoxyethyl (meth)acrylate.

In addition to the units derived from the monomer (a) and the monomer (b), the copolymer (B1) in the present invention further contains an alkyl group having 1 to 4 carbon atoms. (meth)acrylic acid alkyl ester (c) having a straight chain alkyl group having 12 to 36 carbon atoms, (meth)acrylic acid alkyl ester (d) having a straight chain alkyl group having 12 to 36 carbon atoms, and 12 to 36 carbon atoms represented by the following general formula (3) From the viewpoint of HTHS viscosity at effective temperature, it is preferable to have a unit derived from one or more selected from (meth)acrylic acid alkyl esters (e) having a branched alkyl group.

Examples of the (meth)acrylic acid alkyl ester (c) having an alkyl group having 1 to 4 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate. etc. Among them, methyl (meth)acrylate and butyl (meth)acrylate are preferred from the viewpoint of HTHS viscosity and viscosity index, and butyl (meth)acrylate is more preferred.

Examples of the (meth)acrylic acid alkyl ester (d) having a linear alkyl group having 12 to 36 carbon atoms include n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, and n-(meth)acrylate. Tetradecyl, n-pentadecyl (meth)acrylate, n-hexadecyl (meth)acrylate, n-octadecyl (meth)acrylate, n-icosyl (meth)acrylate, n-tetracosyl (meth)acrylate, (meth) Examples include n-triacontyl acrylate and n-hexatriacontyl (meth)acrylate.
Among these, preferable from the viewpoint of HTHS viscosity and viscosity index are (meth)acrylic acid alkyl esters having a linear alkyl group having 12 to 32 carbon atoms, and more preferable are acrylic acid alkyl esters having a linear alkyl group having 12 to 28 carbon atoms. Particularly preferred are (meth)acrylic esters having a linear alkyl group having 12 to 22 carbon atoms.

（式（３）において、Ｒ^６は水素原子又はメチル基であり、－Ｘ^３－は－Ｏ－又は－ＮＨ－であり、Ｒ^７は互いに独立に、炭素数２～４のアルキレン基であり、Ｒ^８及びＲ^９は互いに独立に、炭素数４～２４の直鎖アルキル基であり、ｒは０～２０の整数であり、Ｒ^７が２以上の互いに異なるアルキレン基である場合に（Ｒ^７Ｏ）で示される単位はランダムに結合していてもブロック構造を有してもよい）。 The (meth)acrylic acid alkyl ester (e) having a branched alkyl group having 12 to 36 carbon atoms is a compound represented by the general formula (3).

(In formula (3), R ⁶ is a hydrogen atom or a methyl group, -X ³ - is -O- or -NH-, and R ⁷ is independently an alkylene group having 2 to 4 carbon atoms. , R ⁸ and R ⁹ are each independently a linear alkyl group having 4 to 24 carbon atoms, r is an integer of 0 to 20, and when R ⁷ is two or more different alkylene groups, (R The units represented by ⁷ O) may be bonded randomly or may have a block structure).

R ⁶ in general formula (3) is a hydrogen atom or a methyl group. Among these, methyl group is preferred from the viewpoint of viscosity index.

-X ³ - in general formula (3) is -O- or -NH-. Among these, -O- is preferred from the viewpoint of viscosity index.

R ⁷ in general formula (3) is an alkylene group having 2 to 4 carbon atoms. Examples of the alkylene group having 2 to 4 carbon atoms include ethylene group, isopropylene group, 1,2- or 1,3-propylene group, isobutylene group, and 1,2-, 1,3- or 1,4-butylene group. can be mentioned.

In the general formula (3), r is an integer of 0 to 20, preferably an integer of 0 to 5, and more preferably an integer of 0 to 2, from the viewpoint of the viscosity index.
When r is 2 or more, R ⁷ may be the same or different, and when R ⁷ is 2 or more different alkylene groups, the (R ⁷ O)r moiety may be a random bond or a block bond.

R ⁸ and R ⁹ in the general formula (3) are each independently a straight-chain alkyl group having 4 to 24 carbon atoms. From the viewpoint of viscosity index, straight chain alkyl groups having 6 to 24 carbon atoms are preferred, straight chain alkyl groups having 6 to 20 carbon atoms are more preferred, and straight chain alkyl groups having 8 to 16 carbon atoms are particularly preferred. It is an alkyl group. For example, n-butyl group, n-heptyl group, n-hexyl group, n-pentyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tetradecyl group. group, n-hexadecyl group, n-octadecyl group, n-eicosyl group, n-tetracosyl group, and the like.

Examples of the compound represented by the above formula (3) include 2-octyldecyl (meth)acrylate, ester of ethylene glycol mono-2-octylpentadecyl ether and (meth)acrylic acid, and (meth)acrylic acid. 2-octyldodecyl, 2-n-decyltetradecyl (meth)acrylate, 2-n-dodecylhexadecyl (meth)acrylate, 2-tetradecyloctadecyl (meth)acrylate, 2-dodecyl (meth)acrylate Pentadecyl, 2-tetradecylheptadecyl (meth)acrylate, 2-hexadecylheptadecyl (meth)acrylate, 2-heptadecylicosyl (meth)acrylate, 2-hexadecyldocosyl (meth)acrylate , 2-eicosyl docosyl (meth)acrylate, 2-tetracosylhexacosyl (meth)acrylate, and N-2-octyldecyl (meth)acrylamide.
Among the above, preferred from the viewpoint of viscosity index are (meth)acrylic acid alkyl esters having a branched alkyl group having 12 to 36 carbon atoms, and more preferred are (meth)acrylic acid alkyl esters having a branched alkyl group having 14 to 32 carbon atoms. Meth)acrylic acid alkyl esters, particularly preferred are (meth)acrylic acid alkyl esters having a branched alkyl group having 16 to 28 carbon atoms.

The monomers (b) to (e) described above are obtained by reacting the terminal hydroxy group or amino group of a hydrocarbon group-containing compound with (meth)acrylic acid. These do not have a polyolefin structure having 50 to 1,000 carbon atoms at the end, and are different from the above component (a). Also, 2 to 20 moles of ethylene oxide or butylene oxide are added to an alcohol with 1 to 8 carbon atoms, and 1 to 20 moles of ethylene oxide or butylene oxide are added to an alcohol with a branched alkyl group of 10 to 50 carbon atoms. Since these are not hydrocarbon polymers, they do not fall under the category of polyolefin monomers.

The proportion of repeating units derived from the monomer (a) constituting the copolymer (B1) is preferably 1 to 1 based on the weight of the copolymer (B) from the viewpoint of HTHS viscosity in the effective temperature range. The amount is 50% by weight, more preferably 3 to 40% by weight, particularly preferably 5 to 30% by weight, and most preferably 8 to 20% by weight.
The proportion of repeating units derived from the monomer (b) constituting the copolymer (B1) is preferably 1 to 1 based on the weight of the copolymer (B) from the viewpoint of HTHS viscosity in the effective temperature range. 80% by weight, more preferably 5 to 75% by weight, particularly preferably 10 to 70% by weight, most preferably 15 to 65% by weight.
The total ratio of monomer (a) and monomer (b) constituting the copolymer (B1) is determined based on the weight of the copolymer (B) from the viewpoint of HTHS viscosity in the effective temperature range. The amount is preferably 10% by weight or more, more preferably 15 to 90% by weight, particularly preferably 20 to 80% by weight, and most preferably 25 to 75% by weight.
The proportion of repeating units derived from the monomer (c) constituting the copolymer (B1) is preferably 0 to 50 based on the weight of the copolymer (B) from the viewpoint of HTHS viscosity in the effective temperature range. % by weight, more preferably 5 to 40% by weight, particularly preferably 10 to 40% by weight.
The proportion of repeating units derived from the monomer (d) constituting the copolymer (B1) is preferably 0 to 0 based on the weight of the copolymer (B) from the viewpoint of HTHS viscosity in the effective temperature range. 40% by weight, more preferably 1 to 35% by weight, particularly preferably 2 to 30% by weight, and most preferably 5 to 20% by weight.
The proportion of repeating units derived from the monomer (e) constituting the copolymer (B1) is preferably based on the weight of the copolymer (B) from the viewpoint of HTHS viscosity in the effective temperature range and low temperature viscosity. is 0 to 40% by weight, more preferably 1 to 30% by weight, particularly preferably 1 to 20% by weight.

In the present invention, the solubility parameter (hereinafter abbreviated as SP value) of the copolymer (B1) is preferably 9.1 to 9.5 (cal/cm ³ ) from the viewpoint of viscosity index and solubility in base oil. ) ^1/2 , more preferably 9.1 to 9.4 (cal/cm ³ ) ^1/2 , particularly preferably 9.1 to 9.3 (cal/cm ³ ) ^1/2 .
If the SP value of the copolymer (B1) is less than the above-mentioned lower limit, the required temperature-viscosity characteristics cannot be obtained, and if it exceeds the above-mentioned upper limit, there is a problem that the solubility in the base oil deteriorates.
The SP value of the copolymer (B1) is a value calculated by the method described in the Fedors method (Polymer Engineering and Science, February, 1974, Vol. 14, No. 2, P. 147-154).

The SP value of the copolymer (B1) is determined by calculating the SP value of each monomer constituting the copolymer (B) using the method described above, and calculating the SP value of each monomer based on the constituent monomer units. This is the average value based on the mole fraction of
The SP value of the copolymer (B1) can be adjusted by appropriately adjusting the SP value and molar fraction of the monomers used.

The Mw of the copolymer (B1) is preferably 100,000 to 1,000,000, more preferably 200,000 to 900,000, from the viewpoint of HTHS viscosity in the effective temperature range and low temperature viscosity. , particularly preferably from 300,000 to 800,000, most preferably from 400,000 to 700,000.

The crystallization temperature of the copolymer (B1) is preferably -30°C or lower, more preferably -40°C or lower, particularly preferably -50°C or lower, and most preferably -60℃ or below.

Copolymer (B1) can be obtained by a known production method. For example, it can be obtained by solution polymerizing each of the monomer compounds described above in a solvent in the presence of a polymerization catalyst. For example, it can be produced by the method described in Patent Document 2 (Republication No. 2015-129732).
Examples of the solvent include toluene, xylene, alkylbenzene having 9 to 10 carbon atoms, methyl ethyl ketone, and mineral oil.
Examples of polymerization catalysts include azo catalysts (2,2'-azobis(2-methylbutyronitrile) and 2,2'-azobis(2,4-dimethylvaleronitrile), etc.), peroxide catalysts (benzoyl peroxide), etc. oxide, cumyl peroxide, lauryl peroxide, etc.) and redox catalysts (mixtures of benzoyl peroxide and tertiary amine, etc.). Furthermore, if necessary, a known chain transfer agent (such as an alkyl mercaptan having 2 to 20 carbon atoms) may be used.
The polymerization temperature is preferably 25 to 140°C, more preferably 50 to 120°C from the viewpoint of industrialization. In addition to the solution polymerization described above, the copolymer (B-1) can be obtained by bulk polymerization, emulsion polymerization, or suspension polymerization. The polymerization form of the copolymer may be either a random addition polymer or an alternating copolymer, and may also be a graft copolymer or a block copolymer.

(B2) The second embodiment of the (co)polymer is:
(i) a repeating unit derived from a polyolefin-based macromonomer;
(ii) (Alkyl)styrene monomer having 8 to 17 carbon atoms, alkyl (meth)acrylate having an alkyl group having 1 to 10 carbon atoms, vinyl ester having an alkyl group having 1 to 11 carbon atoms in the acyl group, carbon number Vinyl ether having an alkyl group of 1 to 10 carbon atoms, (di)alkyl fumarate having an alkyl group of 1 to 10 carbon atoms, (di)alkyl maleate having an alkyl group of 1 to 10 carbon atoms, and mixtures of these monomers A comb-shaped polymer containing a repeating unit derived from a low-molecular monomer (hereinafter simply referred to as a low-molecular monomer) selected from the group consisting of
The degree of molar branching is within the range of 0.1 to 10 mol%,
A total of at least 80% by mass of the (i) repeating unit derived from a polyolefin-based macromonomer and the (ii) repeating unit derived from a low molecular monomer, based on the total mass of the repeating units, and the (i) ) The above-mentioned comb-shaped polymer contains 8 to 30% by weight of repeating units derived from a polyolefin-based macromonomer.
Incidentally, the term "comb-shaped polymer" used in the present invention means that a relatively long side chain is bonded to the main chain of the polymer. The side chain has a repeating unit of an olefin such as an alkene or an alkadiene, and the main chain has a repeating unit derived from a low-molecular-weight monomer.

The comb-shaped polymer may be 0.1 to 10 mol%, preferably 0.2 to 5 mol%, more preferably 0.3 to 1.1 mol%, more preferably 0.4 to 1.0 mol%, especially Preferably it has a molar branching degree within the range of 0.4 to 0.6 mol%. The detailed method for producing the comb-shaped polymer and the method for calculating the degree of branching are as described in Japanese Patent No. 5502730. For example, it is produced by free radical polymerization with macromonomers and low-molecular monomers described below.

Polyolefin-based macromonomers are known in the art and may have at least one group derived from a polyolefin. For example, it can be obtained by polymerizing alkenes having 2 to 10 carbon atoms, alkadienes having 4 to 10 carbon atoms, and the like. The groups derived from said alkene and/or alkadiene are preferably at least 70% by weight, more preferably at least 80% by weight, most preferably at least 90% by weight, relative to the weight of the repeating unit derived from the polyolefin-based macromonomer. include. The polyolefin groups can especially be present in hydrogenated form. Furthermore, in addition to the groups derived from the alkane and/or alkadiene, the polymer may further include a group derived from a copolymerizable monomer. The number average molecular weight of the repeating units derived from the polyolefin-based macromonomer is preferably in the range 500 to 50,000 g/mol, more preferably in the range 700 to 10,000 g/mol, especially in the range 1,500 to 4,900 g/mol. /mol range. Also, functionalized polyolefins can be converted into macromonomers. For example, it may be a polyolefin-based macroalcohol and/or a macroamine, and these may be commercially available.

Examples of (alkyl)styrene monomers having 8 to 17 carbon atoms include styrene, α-methylstyrene, α-ethylstyrene, vinyltoluene, and p-methylstyrene, as well as monochlorostyrene, dichlorostyrene, tribromostyrene, and tetrabromostyrene. Examples include halogenated styrenes such as.

The alkyl (meth)acrylate having an alkyl group having 1 to 10 carbon atoms preferably has an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, such as methyl (meth)acrylate. Acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, 2-propynyl (meth)acrylate, allyl (meth)acrylate, vinyl (meth)acrylate, Examples include cyclopentyl (meth)acrylate and 3-vinylcyclohexyl (meth)acrylate.

The vinyl ester having an alkyl group having 1 to 11 carbon atoms in the acyl group preferably has an alkyl group having 2 to 9 carbon atoms, more preferably an alkyl group having 2 to 5 carbon atoms in the acyl group. Examples include vinyl formate, vinyl acetate, vinyl propionate, and vinyl butyrate. The vinyl ether having an alkyl group having 1 to 10 carbon atoms preferably includes vinyl methyl ether, vinyl ethyl ether, and vinyl propyl ether having an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms. , vinyl butyl ether, etc.

A (di)alkyl fumarate having an alkyl group having 1 to 10 carbon atoms preferably has an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, such as monomethyl fumarate. , dimethyl fumarate, monoethyl fumarate, diethyl fumarate, methylethyl fumarate, monobutyl fumarate, and the like. A (di)alkyl maleate having an alkyl group having 1 to 10 carbon atoms preferably has an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, such as monomethyl maleate. , dimethyl maleate, monoethyl maleate, diethyl maleate, methylethyl maleate, monobutyl maleate, dibutyl maleate, and the like.

The comb-shaped polymer further includes alkyl (meth)acrylates having an alkyl group having 11 to 30 carbon atoms, aminoalkyl (meth)acrylates, aminoalkyl (meth)acrylamides, hydroxyalkyl (meth)acrylates, and heterocyclic (meth)acrylates. It may have repeating units derived from etc.

The ratio of (i) the repeating unit derived from the polyolefin-based macromonomer and (ii) the repeating unit originating from the low molecular monomer is based on the mass of the repeating unit. It has at least 80% by weight, preferably at least 90% by weight of repeating units derived from low molecular weight monomers and repeating units derived from macromonomers based on the total weight of the comb polymer. Further, the comb-shaped polymer preferably has macromonomer-derived repeating units in an amount of 8 to 30% by mass, more preferably 10 to 26% by mass based on the total mass of repeating units. The comb polymer preferably has a weight average molecular weight of 50,000 to 1,000,000 g/mol, more preferably 100,000 to 500,000 g/mol. The number average molecular weight is preferably 20,000 to 800,000 g/mol, more preferably 40,000 to 200,000 g/mol.

The comb polymer (B2) preferably has repeating units derived from styrene and repeating units derived from n-butyl (meth)acrylate. These mass ratios are preferably in the range of mass of styrene-derived units: mass of n-butyl (meth)acrylate-derived units from 1:1 to 1:9, more preferably from 1:2 to 1:8. . Alternatively, it is preferable to have a repeating unit derived from methyl methacrylate and a repeating unit derived from n-butyl methacrylate. In this case, the mass ratio of units derived from methyl methacrylate to units derived from n-butyl methacrylate is preferably 1:1 to 0:100, more preferably 3:7 to 0:100.

（上記式中、Ｒ’は、水素原子又はメチル基であり、Ｒは炭素数１～１０の一価炭化水素基であり、Ｑは炭素数１～６のアルキル基で置換されていてもよいブタジエンの１，４付加により形成されたセグメントであり、Ｑ’は炭素数１～６のアルキル基で置換されていてもよいブタジエンのビニル付加により形成されたセグメントであり、ｎ、ｍは、ｎ＋ｍの値が１０～３０００を満たす整数である）

（上記式中、Ｒ’は、水素原子又はメチル基であり、Ｒ^２は炭素原子数１～３０個を有するアルキル基である）。
当該共重合体の詳細な製造方法は特許第３４７４９１８号に記載の通りである。 More preferably, the copolymer (B2) is derived from a repeating unit derived from a polyolefin-based macromonomer represented by the following formula (4) and an alkyl (meth)acrylate represented by the following formula (5). It is a comb-shaped polymer having repeating units.

(In the above formula, R' is a hydrogen atom or a methyl group, R is a monovalent hydrocarbon group having 1 to 10 carbon atoms, and Q may be substituted with an alkyl group having 1 to 6 carbon atoms. A segment formed by 1,4 addition of butadiene, Q' is a segment formed by vinyl addition of butadiene which may be substituted with an alkyl group having 1 to 6 carbon atoms, and n and m are n+m is an integer satisfying 10 to 3000)

(In the above formula, R' is a hydrogen atom or a methyl group, and R ² is an alkyl group having 1 to 30 carbon atoms).
The detailed method for producing the copolymer is as described in Japanese Patent No. 3474918.

The lubricating oil composition of the present invention may contain, in addition to the lubricating base oil (A) and the copolymer (B), an alkyl (meth)acrylic ester (co)polymer other than (B). . The copolymer is not particularly limited as long as it is an alkyl (meth)acrylic acid ester (co)polymer other than (B), but it is an alkyl (meth)acrylic acid ester having a linear alkyl group having 1 to 18 carbon atoms. Examples include (co)polymers. For example, n-octadecyl methacrylate/n-dodecyl methacrylate (molar ratio 10-30/90-70) copolymer, n-tetradecyl methacrylate/n-dodecyl methacrylate (molar ratio 10-30/90-70) Copolymer, n-hexadecyl methacrylate/n-dodecyl methacrylate/methyl methacrylate (molar ratio 20-40/55-75/0-10) copolymer and n-dodecyl acrylate/n-dodecyl methacrylate ( Examples include copolymers with a molar ratio of 10 to 40/90 to 60, and these may be used alone or in combination of two or more.

From the viewpoint of low-temperature viscosity, the amount of the alkyl (meth)acrylic acid ester (co)polymer is preferably 0.01 to 30 parts by weight, more preferably 0.01 parts by weight, based on 100 parts by weight of component (B). ~20 parts by weight, particularly preferably 0.01 to 10 parts by weight, most preferably 0.01 to 5 parts by weight.

The lubricating oil composition of the present invention suppresses the increase in viscosity at extremely low temperatures (hereinafter referred to as cryogenic temperatures) and has a small viscosity difference over a wider temperature range, that is, the viscosity increase is suppressed at cryogenic temperatures. Moreover, at high temperatures, a relatively high viscosity equivalent to that of conventional products can be ensured.
That is, the kinematic viscosity (mm ² /s) at 40° C. of the lubricating oil composition of the present invention is 10 to 60 mm ² /s, preferably 10 to 40 mm ² /s, and more preferably 15 to 35 mm ² /s. s, more preferably 20 to 30 mm ² /s, and still more preferably 22 to 27 mm ² /s.
The lubricating oil composition of the present invention has a kinematic viscosity (mm ² /s) at 100° C. of 5 to 22 mm ² /s, preferably 5 to 12 mm ² /s, and preferably 5 to 10 mm ² /s. , more preferably 5.5 to 9.0 mm ² /s, still more preferably 6.0 to 8.5 mm ² /s, particularly preferably 6.5 to 8.0 mm ² /s, and most preferably Preferably it is 7.0 to 7.8 mm ² /s.
In particular, the lubricating oil composition of the present invention has a kinematic viscosity (mm ² /s) at 0°C of 60 to 250 mm ² /s, preferably 60 to 180 mm ² /s, and preferably 80 to 170 mm ² /s. s, more preferably 100 to 165 mm ² /s, still more preferably 120 to 160 m ² /s, and most preferably 140 to 155 mm ² /s.
Furthermore, the lubricating oil composition of the present invention can be expected to have a viscosity equivalent to the kinematic viscosity at 100°C, even in a high temperature range of over 100°C.
Among them, the lubricating oil composition of the present invention, in which the lubricating oil composition has a kinematic viscosity at 100°C of 6.9 or more and less than 9.3, satisfies SAE20 in the SAE viscosity classification, and has a kinematic viscosity of 6.1 or more and less than 8.2 at 100°C. The lubricating oil composition of the present invention satisfies SAE 16 in the SAE viscosity classification.

Further, although not limited to, the lubricating oil composition of the present invention has a kinematic viscosity (mm ² /s) at 100° C. that satisfies SAE30, SAE40, and SAE50 in the SAE viscosity classification ( ^9.3 mm 2 /s). /s or more and less than 21.9 mm ² /s).
The kinematic viscosity satisfying SAE30 means that the lubricating oil composition has a kinematic viscosity of 9.3 mm ² /s or more and less than 12.5 mm ² /s at 100°C. In this case, although not in the SAE viscosity classification, the kinematic viscosity (mm ² /s) at 0°C is preferably 120 to 200 mm ² /s, more preferably 140 to 190 mm ² /s, and the kinematic viscosity (mm 2 /s) at 40°C ( mm ² /s) is preferably 15 to 60 mm ² /s, more preferably 20 to 50 mm ² /s, particularly preferably 25 to 40 mm ² /s.
The kinematic viscosity satisfying SAE40 means that the lubricating oil composition has a kinematic viscosity of 12.5 mm ² /s or more and less than 16.3 mm ² /s at 100°C. In this case, although it is not an SAE viscosity classification, the kinematic viscosity (mm ² /s) at 0°C is preferably 140 to 230 mm ² /s, more preferably 150 to 200 mm ² /s, and the kinematic viscosity (mm 2 /s) at 40°C mm ² /s) is preferably 15 to 60 mm ² /s, more preferably 20 to 50 mm ² /s, particularly preferably 25 to 40 mm ² /s.
The kinematic viscosity that satisfies SAE50 means that the lubricating oil composition has a kinematic viscosity of 16.3 mm ² /s or more and less than 21.9 mm ² /s at 100°C. In this case, although it is not an SAE viscosity classification, the kinematic viscosity (mm ² /s) at 0°C is preferably 160 to 250 mm ² /s, more preferably 180 to 230 mm ² /s, and the kinematic viscosity (mm 2 /s) at 40°C ( mm ² /s) is preferably 15 to 60 mm ² /s, more preferably 20 to 50 mm ² /s, particularly preferably 25 to 40 mm ² /s.
Such a lubricating oil composition that satisfies SAE30, SAE40, and SAE50 can be obtained by blending a larger amount of the copolymer in the lubricating oil composition having the structure of the present invention described above. That is, the amount of copolymer (B) is 0.5 to 10% by weight, preferably 1.0 to 9.0% by weight, more preferably 2.0 to 8.0% by weight, and most preferably 3.0% by weight. The content is preferably 7.5% by mass.

That is, as another aspect of the present invention,
A lubricating oil composition comprising (A) a base oil and (B) a (co)polymer and having a NOACK evaporation amount of 15% by mass or more and less than 25% by mass, wherein the component (B) is derived from a polymerizable monomer. It is a (co)polymer having a main chain having a repeating unit and a side chain having a polyolefin structure, and the amount of the component (B) is 0.5 to 10% by mass based on the total mass of the lubricating oil composition. , and contains a fraction having a boiling point in the range of 350°C to 400°C in an amount of 20 to 60% by mass based on the total mass of the lubricating oil composition, and has a kinematic viscosity at 100°C of 9.3 or more and 21.9 mm ² / s and a kinematic viscosity at 0° C. of 120 to 250 mm ² /s.

As a more preferred embodiment of the aspect satisfying SAE30, SAE40, or SAE50, the lubricating oil composition preferably further has at least one of the characteristics (1) to (11) shown below.
(1) A fraction having a boiling point in the range of over 400°C to 450°C is contained in an amount of 10 to 70% by mass based on the total mass of the lubricating oil composition.
(2) It does not contain a fraction whose boiling point is above 600°C derived from the base oil (A).
(3) The content of a fraction having a boiling point of less than 350°C is 10% by weight or less.
(4) A fraction having a boiling point in the range of 370°C to 390°C is contained in an amount of 10 to 50% by mass based on the total mass of the lubricating oil composition.
(5) As the base oil (A), (A1) a base oil containing 50 to 99% by mass of a fraction with a boiling point in the range of 350 to 400°C, and (A2) a base oil with a boiling point in the range of more than 400 to 450°C or less. Contains a base oil containing 40 to 90% by mass of a fraction within the range, the content of component (A1) is 20 to 70% by mass with respect to the total mass of the lubricating oil composition, and the content of component (A2) is 20 to 70% by mass is 25 to 75% by mass.
(6) The (B) (co)polymer has a polyolefin structure having 50 to 1,000 carbon atoms at one end and a unit derived from a compound having a (meth)acryloxy group at the other end. (co)polymer (B-1) having a solubility parameter (SP value) of 9.1 to 9.5 (cal/cm ³ ) ^1/2. have
(7) The (B) (co)polymer is
(i) a repeating unit derived from a polyolefin-based macromonomer;
(ii) styrene monomers with 8 to 17 carbon atoms, alkyl (meth)acrylates with 1 to 10 carbon atoms in the alcohol group, vinyl esters with 1 to 11 carbon atoms in the acyl group, Vinyl ethers with 1 to 10 carbon atoms in the alcohol group, (di)alkyl fumarates with 1 to 10 carbon atoms in the alcohol group, (di)alkyl fumarates with 1 to 10 carbon atoms in the alcohol group, ) alkyl maleate, and a repeating unit derived from a low molecular monomer (hereinafter simply referred to as a low molecular monomer) selected from the group consisting of a mixture of these monomers, ,
The degree of molar branching is within the range of 0.1 to 10 mol%,
A total of at least 80% by mass of the (i) repeating unit derived from a polyolefin-based macromonomer and the (ii) repeating unit derived from a low molecular monomer, based on the mass of the repeating unit,
The comb-shaped polymer (B-2) is characterized by containing 8 to 30% by mass of repeating units derived from the polyolefin-based macromonomer (i).
(8) The base oil (A) has a kinematic viscosity of 2.0 to 5.0 mm ² /s at 100°C.
(9) The base oil (A) is mineral oil and/or GTL.
(10) A lubricating oil composition further containing at least one additive selected from metal detergents, friction modifiers, antioxidants, and antiwear agents.
(11) A lubricating oil composition for internal combustion engines.
(12) A lubricating oil composition for hybrid vehicles.
The contents explained above apply to the details of the distillation properties and the components (A) and (B) of the lubricating oil composition. Other components will be described later.

The lubricating oil composition that satisfies SAE30, SAE40, and SAE50 has a higher kinematic viscosity at 100°C than the above-mentioned SAE20 and SAE16, but at the same time, the kinematic viscosity at 40°C and 0°C is also higher, so the lubricating oil composition The ratio of the kinematic viscosity (mm ² /s) at 40°C and the kinematic viscosity (mm ² /s) at 100°C, and the kinematic viscosity (mm 2 /s) at 0°C and the kinematic viscosity (mm ² /s) at 100°C of ^a material. The ratio of s) can satisfy the objective range of the present invention, which will be described later. Therefore, even in the embodiments of SAE30, SAE40, and SAE50, a lubricating oil composition with a small difference in viscosity at low temperatures and viscosity at high temperatures can be provided.

That is, the ratio of the kinematic viscosity (mm ² /s) at 40°C and the kinematic viscosity (mm ² /s) at 100°C of the lubricating oil composition of the present invention [(kinematic viscosity (mm ² /s) at 40°C)/ (Kinematic viscosity (mm ² /s) at 100° C.) is preferably 3.4 or less. It is more preferably 3.3 or less, still more preferably 3.2 or less, particularly preferably 3.1 or less, and most preferably 3.0 or less. If this ratio exceeds the above upper limit, the desired viscosity-temperature characteristics cannot be obtained, which is not preferable.
In a further preferred embodiment, the ratio of the kinematic viscosity (mm ² /s) at 0°C to the kinematic viscosity (mm ² /s) at 100°C of the lubricating oil composition of the present invention [(kinematic viscosity (mm ² /s) at 0°C s))/(Kinematic viscosity at 100° C. (mm ² /s))] is preferably 25 or less. It is more preferably 23 or less, still more preferably 21 or less, particularly preferably 20 or less, even more preferably 19 or less, and most preferably 18 or less.
The ratio of the kinematic viscosity (mm ² /s) at 40°C to the kinematic viscosity (mm ² /s) at 100°C of the lubricating oil composition satisfying SAE30, SAE40, and SAE50 [(Kinematic viscosity (mm 2 /s) at ⁴⁰ °C /s))/(Kinematic viscosity at 100°C (mm ² /s))] is preferably 3.4 or less. It is more preferably 3.1 or less, still more preferably 2.9 or less, particularly preferably 2.6 or less, and most preferably 2.3 or less. The ratio of the kinematic viscosity (mm ² /s) at 0°C to the kinematic viscosity (mm ² /s) at 100°C of the lubricating oil composition satisfying SAE30, SAE40, and SAE50 [(Kinematic viscosity (mm 2 /s) at ⁰ °C /s))/(Kinematic viscosity at 100°C (mm ² /s))] is preferably 25 or less, more preferably 20 or less, even more preferably 18 or less, particularly preferably 16 or less, even more preferably It is 14 or less, most preferably 12 or less.

The viscosity index of the lubricating oil composition of the present invention is preferably 200 or more. More preferably 230 or more, still more preferably 250 or more, even more preferably 270 or more, even more preferably 300 or more, particularly preferably 320 or more, and most preferably 350 or more. In the present invention, the viscosity index is calculated by a method based on ASTM D 2270. Further, the viscosity index of the lubricating oil composition in an embodiment satisfying SAE30, SAE40, and SAE50 is preferably 300 or more, more preferably 350 or more, particularly preferably 400 or more, and most preferably 450 or more.

The high temperature high shear viscosity (HTHS100) at 100° C. of the lubricating oil composition of the present invention is preferably 5.1 mPa·s or less. More preferably it is 4.8 mPa·s or less, and still more preferably 4.5 mPa·s or less. The high temperature high shear viscosity (HTHS150) at 150°C is preferably 3.0 mPa·s or less. More preferably, it is 2.8 mPa·s or less, and still more preferably 2.6 mPa·s or less. Further, the ratio of the HTHS value at 100° C. to the HTHS value at 150° C. (HTHS100/HTHS150) of the lubricating oil composition of the present invention is preferably 2.0 or less. It is more preferably 1.9 or less, still more preferably 1.8 or less, and most preferably 1.7 or less.
The high-temperature high-shear viscosity (HTHS150) at 150°C of the lubricating oil composition that satisfies SAE30 is 2.9 mPa·s or more, preferably 5.0 mPa·s or less, more preferably 4.5 mPa·s or less , more preferably 4.0 mPa·s or less. The high-temperature high-shear viscosity (HTHS150) at 150°C of the lubricating oil composition in an embodiment that satisfies SAE40 is 3.5 mPa·s or more, preferably 5.5 mPa·s or less, more preferably 5.0 mPa·s or less, More preferably, it is 4.5 mPa·s or less. The high temperature high shear viscosity (HTHS150) at 150° C. of the lubricating oil composition in an embodiment satisfying SAE50 is 3.7 mPa·s or more, preferably 6.0 mPa·s or less, more preferably 5.5 mPa·s or less, More preferably, it is 5.0 mPa·s or less.
The high-temperature high-shear viscosity (HTHS100) at 100°C of the lubricating oil composition that satisfies SAE30 is preferably 8.0 mPa·s or less, more preferably 7.0 mPa·s or less, and still more preferably 6.0 mPa·s. It is as follows. The high-temperature high-shear viscosity (HTHS100) at 100°C of the lubricating oil composition that satisfies SAE40 is preferably 9.0 mPa·s or less, more preferably 8.0 mPa·s or less, and even more preferably 7.0 mPa·s or less. It is. The high temperature high shear viscosity (HTHS100) at 100°C of the lubricating oil composition that satisfies SAE50 is preferably 10.0 mPa·s or less, more preferably 9.0 mPa·s or less, even more preferably 8.0 mPa·s or less. It is.
The ratio of the HTHS value at 100° C. to the HTHS value at 150° C. (HTHS100/HTHS150) of the lubricating oil composition in an embodiment satisfying SAE30, SAE40, and SAE50 is preferably 2.0 or less. It is more preferably 1.9 or less, still more preferably 1.8 or less, and most preferably 1.7 or less.
In the present invention, HTHS at 100°C is measured in accordance with ASTM D6616, and HTHS150 at 150°C is measured in accordance with ASTM D4683.

Although the CCS viscosity at -35°C of the lubricating oil composition of the present invention is not limited, it is preferably 6.2 Pa·s or less, more preferably 3.5 Pa·s or less, even more preferably 3.2 Pa·s or less, More preferably, it is 3.0 Pa·s or less, particularly preferably 2.8 Pa·s or less, particularly preferably 2.5 Pa·s or less, most preferably 2.3 Pa·s or less. In the present invention, CCS viscosity at -35°C is measured in accordance with ASTM D5293.

As described above, the lubricating oil composition of the present invention contains (A) a specific base oil and (B) a specific viscosity index improver as essential components. Furthermore, in addition to these, one or more types selected from (C) a friction modifier, (D) an anti-wear agent, (E) a metal detergent, and (F) an antioxidant may be included as an optional component.

(C) Friction modifier The friction modifier is not particularly limited, and conventionally known ones can be used. For example, sulfur-containing organic molybdenum compounds such as molybdenum dithiophosphate (MoDTP) and molybdenum dithiocarbamate (MoDTC), complexes of molybdenum compounds with sulfur-containing organic compounds or other organic compounds, and molybdenum sulfide and molybdic acid sulfide. Examples include complexes of sulfur-containing molybdenum compounds and alkenylsuccinimides. Examples of the molybdenum compounds include molybdenum oxides such as molybdenum dioxide and molybdenum trioxide, molybdic acids such as orthomolybdic acid, paramolybdic acid, and (poly)sulfurized molybdic acid, and molybdenum salts such as metal salts and ammonium salts of these molybdic acids. Salts, molybdenum sulfides such as molybdenum disulfide, molybdenum trisulfide, molybdenum pentasulfide and molybdenum polysulfide, molybdic acid sulfide, metal salts or amine salts of molybdic acid sulfide, and molybdenum halides such as molybdenum chloride. Examples of the sulfur-containing organic compounds include alkyl(thio)xanthate, thiadiazole, mercaptothiadiazole, thiocarbonate, tetrahydrocarbylthiuram disulfide, bis(di(thio)hydrocarbyl dithiophosphonate) disulfide, and organic(poly)sulfide. and sulfurized esters. Particularly preferred are organic molybdenum compounds such as molybdenum dithiophosphate (MoDTP) and molybdenum dithiocarbamate (MoDTC).

Sulfur-free organic molybdenum compounds can also be used as friction modifiers. Examples of such compounds include molybdenum-amine complexes, molybdenum-succinimide complexes, molybdenum salts of organic acids, and molybdenum salts of alcohols. Furthermore, the trinuclear molybdenum compounds described in US Pat. No. 5,906,968 and friction modifiers other than those mentioned above include, for example, esters, amines, amides, and sulfurized esters.

The content of the friction modifier may be within a range that does not impair the low viscosity, low evaporability, and friction reducing effect of the lubricating oil composition. The friction modifier has a molybdenum concentration [Mo] of 200 to 1400 mass ppm, preferably 300 to 1200 mass ppm, more preferably 400 to 1000 mass ppm, and most preferably It is added in an amount ranging from 500 to 900 ppm by mass. If the amount of the friction modifier exceeds the above upper limit, cleanliness may deteriorate; if it is less than the above lower limit, friction may not be sufficiently reduced or cleanliness may deteriorate. .

(D) Anti-wear agent Conventionally known anti-wear agents can be used as the anti-wear agent. Among these, antiwear agents containing phosphorus are preferred, and zinc dithiophosphate (ZnDTP (also referred to as ZDDP)) is particularly preferred. Additionally, zinc dithiocarbamate (ZnDTC) may be used in combination.

In the present lubricating oil composition, the amount of the zinc dialkyldithiophosphate is preferably such that the amount of ZnDTP-derived phosphorus is 300 to 1500 ppm by mass, preferably 350 to 1200 ppm by mass based on the total mass of the lubricating oil composition. The amount may be 500 to 900 ppm, more preferably 400 to 1000 ppm by mass, particularly preferably 500 to 900 ppm by mass. By containing the zinc dialkyldithiophosphate in an amount within the above range, it is possible to achieve both improved friction reduction effect between sliding surfaces and excellent wear resistance without causing catalyst poisoning. In the lubricating oil composition of the present invention, one of zinc dialkyldithiophosphate (Pri-ZnDTP) having a primary alkyl group and zinc dialkyldithiophosphate (Sec-ZnDTP) having a secondary alkyl group is used alone. It may be used, or two or more of these may be used in combination. When used in combination, the mixing ratio is not particularly limited. By combining with MoDTP, both Pri-ZnDTP and Sec-ZnDTP can achieve equally excellent friction reduction effect and wear resistance. Note that, although not limited, an embodiment in which Sec-ZnDTP is essential is particularly preferred, and an amount in which the amount of phosphorus derived from Sec-ZnDTP is 200 to 1500 mass ppm based on the mass of the entire lubricating oil composition is preferred, and preferably The amount is preferably 300 to 1200 ppm by mass, more preferably 400 to 1000 ppm by mass, particularly preferably 500 to 900 ppm by mass.

In addition, at least one compound selected from phosphates, phosphite-based phosphorus compounds, and metal salts and amine salts thereof can also be used in combination with zinc dialkyldithiophosphate. However, the amount of these compounds is limited to an amount such that the total mass of phosphorus in the entire lubricating oil composition satisfies the above range. For example, it is preferably less than 0.1% by mass, more preferably less than 0.05% by mass, even more preferably less than 0.01% by mass, and most preferably not contained at all, based on the total amount of the lubricating oil composition. . Examples of the phosphorus compound include phosphorous acid monoester and (hydrocarbyl)phosphonic acid having one hydrocarbon group having 1 to 30 carbon atoms; phosphorous acid having two hydrocarbon groups having 1 to 30 carbon atoms; Diesters, monothiophosphite diesters, and (hydrocarbyl)phosphonite monoesters; phosphite triesters having three hydrocarbon groups having 1 to 30 carbon atoms, and (hydrocarbyl)phosphonite diesters; and mixtures thereof. etc.

(E) Metal Detergents Examples of metal detergents include detergents containing alkali metals or alkaline earth metals. Examples include, but are not limited to, sulfonates containing alkali metals or alkaline earth metals, salicylates containing alkali metals or alkaline earth metals, and phenates containing alkali metals or alkaline earth metals. Furthermore, examples of alkali metals or alkaline earth metals include, but are not limited to, magnesium, barium, sodium, and calcium.

More specifically, calcium sulfonate, magnesium sulfonate, calcium salicylate, magnesium salicylate, calcium phenate, and magnesium phenate are preferably used. The metal detergents may be used alone or in combination of two or more. The amount of alkali metal or alkaline earth metal contained in the metal detergent is not limited, but is preferably 0.1 to 20% by mass, more preferably 0.5 to 15% by mass, and 1.0 to 15% by mass. Mass % is more preferred.

The metal detergent preferably has a total base number of 20 to 600 mgKOH/g, more preferably 50 to 500 mgKOH/g, even more preferably 100 to 450 mgKOH/g, particularly preferably 150 to 400 mgKOH/g, although it is not limited to this. It is g. This makes it possible to ensure acid neutralization, high-temperature cleanliness, and rust prevention properties necessary for the lubricating oil.

The metal detergent may be contained in any proportion in the lubricating oil composition. For example, it is 0.01 to 5% by weight, more preferably 0.1 to 4% by weight, and even more preferably 0.2 to 3% by weight.

(F) Antioxidant Examples of the antioxidant include ashless antioxidants such as phenol-based and amine-based antioxidants, and metal-based antioxidants such as copper-based and molybdenum-based antioxidants. For example, phenolic ashless antioxidants include 4,4'-methylenebis(2,6-di-tert-butylphenol), 4,4'-bis(2,6-di-tert-butylphenol), isooctyl- Examples of amine-based ashless antioxidants include phenyl-α-naphthylamine, alkylphenyl-α-naphthylamine, and dialkyldiphenylamine. It will be done. The antioxidant is usually blended into the lubricating oil composition in an amount of 0.1 to 5% by mass.

In addition, additives other than those mentioned above include antioxidants such as hindered phenols and aromatic secondary amines, long-chain fatty acids and their esters (oleic acid and oleic acid esters, etc.), long-chain amines and their amides ( oiliness improvers such as oleylamine and oleylamide, silicone oils, metal soaps, antifoaming agents such as fatty acid esters and phosphate compounds, quaternary ammonium salts (tetraalkylammonium salts, etc.), sulfated oils and phosphates demulsifiers such as oxyethylene-containing nonionic surfactant phosphates, etc., and corrosion inhibitors such as nitrogen atom-containing compounds (benzotriazole and 1,3,4-thiodiazolyl-2,5-bisdialkyl dithiocarbamates, etc.) can be mentioned. Various lubricating oil package additives containing at least one of these may also be added.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples.

The base oil (A1) and base oil (A2) used in the following Examples and Comparative Examples are as follows.
Base oil 1: Group III: GTL base oil 1 (kinematic viscosity at 100°C: 4.1 mm ² /s, VI = 131)
Base oil 2: Group III: GTL base oil 2 (kinematic viscosity at 100°C: 2.7 mm ² /s, VI = 113)
Base oil 3: Group III: Mineral oil 1 (kinematic viscosity at 100°C: 4.2 mm ² /s, VI = 125)
Base oil 4: Group III: Mineral oil 2 (kinematic viscosity at 100°C: 3.0 mm ² /s, VI = 107)
Base oil 5: Group IV: PAO1 (kinematic viscosity at 100°C: 3.7 mm ² /s, VI = 122)
Base oil 6: Group II: Mineral oil 3 (kinematic viscosity at 100°C: 2.3 mm ² /s, VI = 102)
Base oil 7: Group III: Mineral oil 4 (kinematic viscosity at 100°C: 4.1 mm ² /s, VI = 134)

The distillation properties of each of the above base oils 1 to 7 are shown in Table 1 below.

Copolymer (B1)
The table below shows the ratio of units derived from monomers (a) to (e-2) in each copolymer used in Examples and Comparative Examples.

Monomers (a) to (e-2) listed in Table 2 above are as described below.
(a): Methacrylic acid ester of the following (Y1) [Mn: 5,000]
(Y1): Polymer containing a hydroxyl group at one end of hydrogenated polybutadiene (trade name: KrasolHLBH-5000M, manufactured by Cray Valley, 1,2-butylene ratio: 65 mol%, hydroxyl value: 10.4 mgKOH/g) [(Y1) Based on the total number of structural units, the total of isobutylene and 1,2-butylene is 65 mol%, the crystallization temperature of (Y1) -60°C or lower]
(b): Butoxyethyl methacrylate (c-1): Methyl methacrylate (c-2): Butyl methacrylate (d-1): n-dodecyl methacrylate (d-2): n-tetradecyl methacrylate (e- 1): 2-n-decyltetradecyl methacrylate (e-2): 2-n-dodecylhexadecyl methacrylate

[Preparation example 1]
Preparation of copolymer (B1A) 400 parts by weight of the above base oil 3 and monomers (a) to (e-2) were placed in a reaction vessel equipped with a stirring device, a heating/cooling device, a thermometer, and a nitrogen introduction tube. Amounts for a total of 100 parts by weight in the composition of the copolymer (B1A) listed in Table 2 above, 0.5 parts by weight of 2,2'-azobis(2,4-dimethylvaleronitrile) and 2,2'- After adding 0.2 parts by weight of azobis(2-methylbutyronitrile) and performing nitrogen substitution (gas phase oxygen concentration 100 ppm), the temperature was raised to 76°C with stirring under closed conditions and kept at the same temperature for 4 hours. A polymerization reaction was performed. After raising the temperature to 120 to 130°C, unreacted monomers were removed at the same temperature under reduced pressure (0.027 to 0.040 MPa) over 2 hours, and the copolymer (B1A) and base oil 3 were added. An additive composition was obtained. The SP value of the obtained copolymer (B1A) was calculated by the method described above. Mw was measured by the method described above.
The copolymer (B1A) used in Example 8 was prepared in the same manner as above except that base oil 1 was used instead of base oil 3 as a solvent. An additive composition containing.

[Preparation example 2]
Preparation of copolymers (B1B, B1C, B1D) The procedure of Preparation Example 1 was repeated except that each monomer (a) to (e-2) was blended to have the composition shown in Table 2 above. A polymerization reaction was conducted to prepare an additive composition containing copolymer (B1B), copolymer (B1C), or copolymer (B1D) and base oil 3. Polymerization time was adjusted appropriately.

Preparation of lubricating oil composition Each additive composition obtained in Preparation Example 1 or 2 above, other additives, and base oils 1 to 7 are listed in Table 3, Table 6, Table 9, or Table 12 below. A lubricating oil composition was obtained by mixing the following amounts. The contents of copolymers (B1A) to (B1D) in Tables 3, 6, 9, and 12 refer to the contents of copolymers (B1A) to (B1D) contained in the lubricating oil composition, with the total amount of the lubricating oil composition being 100% by weight. This is the amount (wt%) of the copolymer alone. The amount of base oil 3 contained as a solvent in the above additive composition is stated as the amount of base oil 3 contained in the lubricating oil composition (weight % when the entire lubricating oil composition is 100 weight %). did. Similarly, in Example 8, the amount of base oil 1 contained as a solvent in the additive composition was the amount of base oil 1 contained in the lubricating oil composition (100% by weight of the entire lubricating oil composition). % by weight).

Copolymer (B2)
Copolymers (B2A) to (B2C) have the following configurations.
(B2A): hPBD _MM4800 ^{Note 1)} Comb-shaped polymer (Mw = 191000 g/mol, molar branching degree = 1.0%, polydispersity index (PDI) = 3.5)
(B2B): hPBD _MM4800 ^{Note 1)} A comb-shaped product made by polymerizing a mixture of 12.0% by mass of hPBD MM4800, 83.0% by mass of n-butyl methacrylate, and 5% by mass of an alkyl methacrylate mixture having an alkyl group having 12 to 14 carbon atoms. Polymer (Mw=374000 g/mol, molar branching degree=0.4%, polydispersity index (PDI)=4.5)
(B2C): hPBD _MM4800 ^{Note 1)} A mixture of 16.0% by mass, 67.0% by mass of n-butyl methacrylate, 12% by mass of styrene, and 5% by mass of an alkyl methacrylate mixture having an alkyl group having 12 to 14 carbon atoms. Polymerized comb-shaped polymer (Mw = 352000 g/mol, molar branching degree = 0.5%, polydispersity index (PDI) = 3.7)
^{Note 1)} The above hPBD _MM4800 is a hydrogenated polybutadiene provided by Cray Valley (Paris, France), with Mn = 4800 g/mol, T _M = -25°C, and macromonomer functionality (f _MM ) range of 90 ~95% macromonomer.

[Preparation example 3]
Preparation of copolymer (B2A) A device equipped with a 4-necked flask and a precision glass saber stirrer was equipped with 600 g of a mixture of a low-molecular monomer mixture and a macromonomer having the composition of B2A, and 400 g of base oil 3. I entered. After heating to 115° C. under nitrogen, 1.2 g of 2,2-bis-tert-butylperoxybutane was added and the temperature was maintained. 3 and 6 hours after the first addition of the initiator, 1.2 g of 2,2-bis-tert-butylperoxybutane were each added again and the mixture was stirred at 115° C. overnight. The next day, the mixture was diluted from 60% to 40% solids with 500g of base oil 3, yielding 1500g of a 40% solution of comb polymer in mineral oil.
Copolymer B2B and copolymer B2C were also prepared in the same manner as above.

Preparation of lubricating oil composition The above copolymers B2A, B2B, and B2C, other additives, and base oils 1 to 7 are blended in the amounts shown in Table 3 or 6 below (the amount of the entire lubricating oil composition is 100% by weight). % by weight) to obtain a lubricating oil composition.

Other copolymers/Copolymer B3: Polyalkyl methacrylate (PMA): Shear stability index (SSI) value 20
・Copolymer B4: Ethylene-propylene copolymer: Shear stability index (SSI) value 50
・Copolymer B5: Star-shaped isoprene copolymer: Shear stability index (SSI) value 9
・Copolymer B6: Isoprene/styrene diblock copolymer: Shear stability index (SSI) value 15

Other additives: Package consisting of metal detergent, antioxidant, ashless dispersant, friction modifier, anti-wear agent

For each lubricating oil composition, the kinematic viscosity, viscosity index, high temperature high shear viscosity, CCS viscosity, and NOACK evaporation amount were measured by the following methods. The compositions, distillation properties, and evaluation results of the lubricating oil compositions of Examples are shown in Tables 3 to 8 below. In addition, the composition, distillation properties, and evaluation results of the lubricating oil compositions of comparative examples are shown in Tables 9 to 14 below. Example 6 and Example 8 are SAE20, Example 7, Example 11 and Example 14 are SAE30, Example 9, Example 12, Example 13 and Example 15 are SAE40, Example 10 and Example 16 are SAE50. It is a lubricating oil composition that satisfies the viscosity classification (high temperature high shear viscosity (HTHS150) at 150°C).
Kinematic viscosity was measured at 0°C, 40°C, and 100°C by a method based on ASTM D 445.
The viscosity index was calculated according to ASTM D 2270.
High temperature high shear viscosity (HTHS100) at 100°C was measured in accordance with ASTM D6616, and high temperature high shear viscosity (HTHS150) at 150°C was measured in accordance with ASTM D4683.
CCS viscosity at -35°C (CCS viscosity) was measured according to ASTM D5293.
NOACK evaporation was measured at 250° C. for 1 hour according to ASTM D 5800.

As can be seen from the comparison between Examples and Comparative Examples listed in the table above, the lubricating oil composition of the present invention maintains its viscosity at high temperatures (100°C) while maintaining its viscosity at low temperatures (40°C) and extremely low temperatures (0°C). The viscosity at is reduced. Thereby, the value of (kinematic viscosity at 40°C)/(kinematic viscosity at 100°C) becomes 3.4 or less. In particular, the value of (kinematic viscosity at 0°C)/(kinematic viscosity at 100°C) is 25 or less.
Graph (solid line) showing the difference between the kinematic viscosity at 0°C and the kinematic viscosity at 100°C for the lubricating oil compositions of Examples 1, 2, and 7, and the kinematic viscosity at 0°C for the lubricating oil compositions of Comparative Examples 1, 9, and 11. A graph (dotted line) showing the difference between the kinematic viscosity at 100° C. and the kinematic viscosity at 100° C. is shown in FIG. As can be seen from Figure 1, in the lubricating oil composition of the present invention, the difference in kinematic viscosity at an extremely low temperature (0°C) and that at a high temperature (100°C) is the same as that in the lubricating oil composition of the comparative example. small compared to The lubricating oil composition makes it possible to reduce fuel consumption.

Claims (10)

A lubricating oil composition for a hybrid vehicle , comprising (A) a base oil and (B) a (co)polymer, and having a NOACK evaporation amount of 15% by mass or more and less than 25% by mass, wherein the component (B) is polymerizable. It is a (co)polymer having a main chain having a repeating unit derived from a monomer and a side chain having a polyolefin structure, and the amount of the component (B) is 0.5 to 10% by mass based on the total mass of the lubricating oil composition. % and having a boiling point in the range of 350°C to 400°C in an amount of 20 to 60% by mass based on the total mass of the lubricating oil composition. The lubricant according to claim 1, which contains a fraction derived from the base oil (A) having a boiling point in the range of more than 400°C to 450°C in an amount of 10 to 70% by mass based on the total mass of the lubricating oil composition. oil composition. The lubricating oil composition according to claim 1 or 2, which does not contain a fraction derived from the base oil (A) having a boiling point in a range exceeding 600°C. The lubricating oil composition according to any one of claims 1 to 3, wherein the content of a fraction having a boiling point in a range of less than 350°C is 10% by mass or less. As the base oil (A), (A1) a base oil containing 50 to 99% by mass of a fraction with a boiling point in the range of 350 to 400 ° C., and (A2) a base oil with a boiling point in the range of more than 400 to 450 ° C. Contains a base oil containing 40 to 90% by mass of a fraction, the content of component (A1) is 20 to 70% by mass and the content of component (A2) is 25 to 75% by mass, based on the total mass of the lubricating oil composition. Composition according to any one of claims 1 to 4, which is % by weight. The (co)polymer (B) has a polyolefin structure having 50 to 1,000 carbon atoms at one end and a unit derived from a compound having a (meth)acryloxy group at the other end. ) Polymer (B1), characterized in that the (B1) (co)polymer has a solubility parameter (SP value) of 9.1 to 9.5 (cal/cm ³ ) ^1/2 . The lubricating oil composition according to any one of claims 1 to 5. The (B) (co)polymer is
(i) a repeating unit derived from a polyolefin-based macromonomer;
(ii) styrene monomers with 8 to 17 carbon atoms, alkyl (meth)acrylates with 1 to 10 carbon atoms in the alcohol group, vinyl esters with 1 to 11 carbon atoms in the acyl group, Vinyl ethers with 1 to 10 carbon atoms in the alcohol group, (di)alkyl fumarates with 1 to 10 carbon atoms in the alcohol group, (di)alkyl fumarates with 1 to 10 carbon atoms in the alcohol group, ) a comb-shaped polymer (B2) comprising a repeating unit derived from a low molecular monomer (hereinafter simply referred to as low molecular monomer) selected from the group consisting of alkyl maleate, and a mixture of these monomers,
The degree of molar branching is within the range of 0.1 to 10 mol%,
A total of at least 80% by mass of the (i) repeating unit derived from a polyolefin-based macromonomer and the (ii) repeating unit derived from a low molecular monomer, based on the mass of the repeating unit,
The comb-shaped polymer (B2) according to any one of claims 1 to 5, characterized in that (i) the comb-shaped polymer (B2) contains 8 to 30% by mass of repeating units derived from a polyolefin-based macromonomer. The described lubricating oil composition. The lubricating oil composition according to any one of claims 1 to 7, wherein the base oil (A) has a kinematic viscosity of 2.0 to 5.0 mm ² /s at 100°C. The lubricating oil composition according to any one of claims 1 to 8, wherein the base oil (A) is mineral oil and/or GTL. The lubricating oil composition according to any one of claims 1 to 9, further comprising at least one additive selected from metal detergents, friction modifiers, antioxidants, and antiwear agents.

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