JP2009126897A - Lubricating oil composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lubricating oil composition capable of contributing to the reduction of electric power consumption. <P>SOLUTION: Provided is this lubricating oil composition obtained by blending an olefin-based viscosity index-improving agent including a copolymer of ethylene and a monomer except ethylene with a hydrocarbon-based base oil for the lubricating oil having a high pressure viscosity of 1.0×10<SP>10</SP>to 2.0×10<SP>12</SP>cP at 40°C and 1.7 GPa and a %CA of 5 or less (excluding a poly α-olefin base oil), wherein the mixture of the base oil and the olefinic viscosity index-improving agent at 20°C has a refractive index of 1.453 to 1.470, and the composition has a dynamic viscosity of 19 to 51 mm<SP>2</SP>/s at 40°C. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a power-saving lubricating oil composition.

  In recent years, global warming has progressed, and there is an urgent need to reduce carbon dioxide emissions, which is one of the greenhouse gases. In Japan, the Law Concerning the Rational Use of Energy and the Law Concerning the Promotion of Global Warming Countermeasures were revised and implemented in 2006, and factories, transporters, etc. are now required to reduce power consumption more than ever. I came.

  As one method of reducing power consumption, power saving from the lubricating oil side used in industrial machines and transportation machines is being attempted. Examples of power saving include reducing friction and wear by blending specific additives. Phosphate ester, phosphate ester amine salt, fatty acid ester, carboxylic acid amide, oxymolybdenum dithiophosphate, Attempts have been made to cope with blending techniques such as sulfurized oxymolybdenum dithiocarbamate (see, for example, Patent Documents 1 and 2). Moreover, the example which aimed at reduction of pressure loss, such as piping, by using specific base oil is also mentioned (refer patent document 3).

On the other hand, recently, the output of industrial machines has been increasing, and along with this, the use of lubricating oil under high pressure conditions is expected to increase further. Therefore, in order to reduce power consumption, a reduction in friction of lubricating oil under high pressure conditions, that is, low traction is required.
In addition to the normal operation, reduction of power consumption at startup is also required, and excellent low temperature fluidity is also required for the lubricating oil.

Japanese Patent Laid-Open No. 5-140556 JP 2001-040383 A JP 2004-250504 A

An object of this invention is to provide the lubricating oil composition which shows the low traction property and the outstanding low-temperature fluidity | liquidity.

As a result of diligent research to solve the above problems, the present inventor formulated a specific olefinic viscosity index improver into a hydrocarbon-based lubricating base oil having a specific high-pressure viscosity, and a specific composition and As a result, it was found that a lubricating oil composition exhibiting low traction and excellent low-temperature fluidity can be obtained, and the present invention has been completed based on this finding.

That is, the present invention is a hydrocarbon-based lubricating base oil having a high-pressure viscosity of 1.0 × 10 ^{10 to} 2.0 × 10 ¹² cP at 40 ° C. and 1.7 GPa and a% CA of 5 or less by ring analysis (however, A lubricating oil composition in which an olefin viscosity index improver composed of a copolymer of ethylene and a monomer other than ethylene is blended with a base oil and the olefin viscosity. Provided is a lubricating oil composition characterized in that the index improver mixture has a refractive index of 1.453 to 1.470 at 20 ° C. and a kinematic viscosity at 40 ° C. of 19 to 51 mm ² / s. To do.
The present invention provides the lubricating oil composition, wherein the olefin viscosity index improver is a copolymer of ethylene and an olefin having 3 to 30 carbon atoms, and the refractive index is 1.453 to 1 at 20 ° C. A lubricating oil composition that is .480 is provided.

The lubricating oil composition of the present invention exhibits low traction and excellent low-temperature fluidity by using a hydrocarbon-based lubricating base oil having a specific composition and high-pressure viscosity. It can be used suitably.

The high-pressure viscosity of the hydrocarbon-based lubricating base oil used in the lubricating oil composition of the present invention is 1.0 × 10 ^{10 to} 2.0 × 10 ¹² cP at 40 ° C. and 1.7 GPa, more preferably 2. 0 × 10 ^{10 to} 5.0 × 10 ¹¹ cP, more preferably 2.5 × 10 ^{10 to} 4.0 × 10 ¹¹ cP, and particularly preferably 3.5 × 10 ^{10 to} 2.5 × 10. ¹¹ cP. If the high-pressure viscosity is less than 1.0 × 10 ¹⁰ cP, an appropriate oil film thickness cannot be maintained, and sufficient wear prevention properties cannot be obtained, which is not preferable. When the high-pressure viscosity exceeds 2.0 × 10 ¹² cP, the traction coefficient increases and the power consumption increases, so that the power saving effect of the present application cannot be sufficiently obtained.

The high-pressure viscosity in the present application is calculated using the following Barus equation.
The Barus equation is represented by the general formula (1).
η = η ₀ exp (αP) (1)
(In general formula (1), η is the absolute viscosity (cP) at pressure P, η ₀ is the absolute viscosity (cP) at atmospheric pressure, and α is the viscosity pressure coefficient.)
The viscosity-pressure coefficient α in the general formula (1) was calculated using the Ohno formula represented by the general formula (2).
^{_{α = 0.62ν 0 0.176 B 2.047 ρ}} 0.293 (2)
(In general formula (2), ν ₀ is the kinematic viscosity (mm ² / s) under atmospheric pressure, ρ is the density (g / cm ³ ) under atmospheric pressure, and B is the viscosity temperature gradient coefficient.)

（一般式（３）において、Ｔ１、Ｔ２は温度（℃）、ν_Ｔ１、ν_Ｔ２は温度Ｔ１、Ｔ２における動粘度（ｍｍ^２／ｓ）である。） Moreover, the viscosity temperature gradient coefficient B of the general formula (2) was calculated using the general formula (3) according to ASTM D341-93.

(In the general formula (3), T1, T2 is the temperature _{(℃), ν T1, ν} T 2 is the kinematic viscosity at ^{T1, T2 (mm 2 / s} ).)

The% CA of the hydrocarbon-based lubricating base oil used in the lubricating oil composition of the present invention by ASTM D3238 ring analysis method is 5 or less, preferably 3 or less, more preferably 2 or less. When% CA exceeds 5, the traction coefficient increases and the power consumption tends to increase. Note that% CA correlates with the content of aromatic hydrocarbons, but aromatic hydrocarbons tend to have a high traction coefficient, so less is preferable. The aromatic hydrocarbon may not be substantially contained.

The refractive index of the hydrocarbon-based lubricating base oil used in the lubricating oil composition of the present invention is not particularly limited, but the refractive index at 20 ° C. according to the JIS K0062 refractive index measurement method is preferably 1.455 to 1.473. More preferably 1.456 to 1.468, still more preferably 1.456 to 1.466, particularly preferably 1.457 to 1.464, and most preferably 1.460 to 1.468. 464. By setting the refractive index at 20 ° C. to 1.455 or more, the refractive index of the mixture of the base oil and the olefin-based viscosity index improver has a refractive index of 1.453 to 1.470 at 20 ° C. of 1.453 or more. It tends to be easy to adjust, and it is easy to achieve good wear resistance. By setting the refractive index at 20 ° C. to 1.473 or less, the refractive index at 20 ° C. of the mixture of the base oil and the olefin viscosity index improver when an olefin viscosity index improver described later is blended is 1. There is a tendency to adjust to 470 or less. That is, the traction coefficient of the composition tends to be kept low, and power saving tends to be easily obtained.

The hydrocarbon-based lubricating base oil of the present invention may be produced by any method as long as the constitution of the present invention is satisfied. For example, a crude oil lubricating oil fraction is subjected to solvent refining, hydrorefining, hydrocracking. Although the manufacturing method combined suitably, such as refinement | purification, is mentioned, The following methods are mentioned as a preferable manufacturing method. First, bottom oil obtained by atmospheric distillation of crude oil is treated with a vacuum distillation apparatus. The vacuum gas oil thus obtained is hydrotreated and hydrocracked, and then a residue obtained by removing light and fuel components with a vacuum stripper is obtained. This residue is distilled under reduced pressure, and the resulting lubricating oil fraction is subjected to hydrodewaxing treatment and stabilization treatment. The hydrodewaxing treatment was carried out using a catalyst in which a group 6 or group 8 metal of the periodic table such as Mo, W, Ni, Pd, etc. was supported on an alumina, silica-alumina or zeolite support. A pressure of 155 to 190 kg / cm ² G, a reaction temperature of 230 to 300 ° C., and LHSV of 0.7 to 1.3 h ⁻¹ are preferable.

Further, a preferable method is a method in which slack wax by solvent dewaxing or wax obtained by Fischer-Tropsch synthesis is used as a raw material, and these are hydrotreated and hydrocracked.
Furthermore, the base oil of the present invention is a hydrocarbon-based lubricating oil having a high-pressure viscosity of 1.0 × 10 ^{10 to} 2.0 × 10 ¹² cP at 40 ° C. and 1.7 GPa and a% CA by ring analysis of 5 or less. The base oil of the present invention can be prepared by mixing two or more hydrocarbon-based lubricating base oils that do not correspond to the base oil. For example, a hydrocarbon-based lubricating base oil having a high pressure viscosity of 1.0 × 10 ¹³ cP at 40 ° C. and 1.7 GPa and a% CA of 7 by ring analysis, and a high pressure viscosity of 1. GPa at 40 ° C. and 1.7 GPa are 1. The preparation method which mixes 0 * 10 < ⁹ > cP and the hydrocarbon-type lubricating base oil whose% CA by ring analysis is 0 is mentioned.

As long as the above-mentioned hydrocarbon-based lubricating base oil is in the described high-pressure viscosity range, one type may be used alone, or two or more types may be used in combination.
The hydrocarbon-based lubricating base oil of the present invention does not contain a polyalphaolefin base oil. Here, the poly α-olefin base oil is a base oil made of a polymer of α-olefin.
In addition, the lubricating oil composition of the present invention may contain a base oil other than the base oil as long as the object of the present invention is not impaired. The total amount is preferably 70% by mass or more, more preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

The olefin viscosity index improver used in the lubricating oil composition of the present invention is a copolymer composed of ethylene and a monomer other than ethylene.
Examples of monomers other than ethylene that form a copolymer with ethylene include olefin hydrocarbons, diene hydrocarbons, vinyl aromatic hydrocarbons, and the like. The number of carbon atoms of these monomers other than ethylene is preferably 3 to 30, more preferably 3 to 25, still more preferably 3 to 15, particularly preferably 3 to 8, and most preferably 3. ~ 5. It is preferable that the number of carbon atoms of the monomer other than ethylene is 30 or less because the molecular weight of the viscosity index improver can be kept relatively low and shear stability can be improved.

The olefinic hydrocarbon used as a monomer other than ethylene may be linear, cyclic, or branched. Specific examples of the olefinic hydrocarbon include propylene, n-butene, i-butylene, cyclobutene, n-pentene, i-pentene, cyclopentene, n-hexene, i-hexene, n-heptene, and i-to. Puten and the like.
The diene hydrocarbon used as a monomer other than ethylene may be a chain, a ring, or a branched chain. Specific examples of the diene hydrocarbon include butadiene, cyclobutadiene, pentadiene, cyclopentadiene, hexadiene, heptadiene and the like.

Examples of vinyl aromatic hydrocarbons used as monomers other than ethylene include styrene and divinylbenzene.
Among these monomers other than ethylene, preferred are olefinic hydrocarbons, and particularly preferred are olefinic hydrocarbons having 3 to 5 carbon atoms.
The olefin viscosity index improver is synthesized by polymerizing monomers other than ethylene and ethylene. However, the number of monomers other than ethylene may be one, or two or more.

The molar ratio of ethylene and a monomer other than ethylene is not particularly limited, but is preferably 80:20 to 20:80, more preferably 70:30 to 30:70, and still more preferably 65:35 to 35:65. It is.
The olefin viscosity index improver may be a regular alternating polymer, a random polymer, a block polymer, or a graft polymer.

The preferred weight average molecular weight of the olefin viscosity index improver is 1000 to 180,000, more preferably 1200 to 145,000, and still more preferably 3000.
˜140,000, particularly preferably 8000 to 130,000, and most preferably 10,000 to 50,000. By setting the weight average molecular weight to 1000 or more, predetermined traction characteristics tend to be easily obtained. By setting the weight average molecular weight to 180,000 or less, it tends to easily suppress a decrease in viscosity under shear. The weight average molecular weight is measured by gel permeation chromatography and is a value in terms of polystyrene.

As long as the object of the present invention is not impaired, the olefin-based viscosity index improver may be either a dispersion type or a non-dispersion type (one having a monomer-derived polar group is a dispersion type and does not have a polar group) Things are called non-dispersive). That is, a dispersion type in which nitrogen atom-containing compounds or alkyl esters are used as monomer molecules other than ethylene may be used. Specific examples of such a nitrogen atom-containing compound include alkyl-vinyl pyridine, N-vinyl pyrrolidone, vinyl imidazole and the like. Specific examples of the alkyl esters include polyalkylene glycol esters, maleic acid esters, and fumaric acid esters. These can be used alone or in combination of two or more.

However, when the molar ratio of the monomer having a dispersing group in the olefin-based viscosity index improver to the other monomer exceeds 25, the traction coefficient of the mixture of the base oil and the olefin-based viscosity index improving agent Tends to increase and power consumption tends to increase. Therefore, the molar ratio of the monomer having a dispersing group and the other monomer is preferably 0: 100 to 25:75, and more preferably 0: 100 to 10:90.

The refractive index of the olefin viscosity index improver is not particularly limited, but the refractive index at 20 ° C. according to the JIS K0062 refractive index measurement method is preferably 1.453 to 1.480, more preferably 1.455 to 1. .478, and more preferably 1.460 to 1.475. By setting the refractive index at 20 ° C. to 1.453 or more, the refractive index of the composition tends to be easily adjusted to 1.453, and good wear resistance can be easily obtained. By setting the refractive index at 20 ° C. to 1.480 or less, it is easy to adjust the refractive index of the composition to 1.470 or less. Therefore, the traction coefficient of the composition tends to be low, and the power saving effect can be easily obtained.

The blending amount of the olefin viscosity index improver with respect to the lubricating oil composition is preferably 1 to 60% by mass, more preferably 2 to 40% by mass, still more preferably 3 to 30% by mass, and particularly preferably. Is 3.5 to 20% by mass. By setting the blending amount to 1% by mass or more, the traction coefficient can be easily kept low, and the power saving effect tends to be easily obtained. If the blending amount exceeds 60% by mass, an increase in the effect cannot be obtained as compared with the increasing amount of the blending amount, which is not economical.
One of the above olefinic viscosity index improvers may be used alone, or two or more thereof may be used in combination.

The refractive index at 20 ° C. according to the JIS K0062 refractive index measurement method of the mixture of the base oil and the olefinic viscosity index improver of the present invention is 1.453 to 1.470, more preferably 1.454 to 1. .468, more preferably 1.455 to 1.465, and particularly preferably 1.456 to 1.463. When the refractive index at 20 ° C. is less than 1.453, the wear resistance tends to decrease. When the refractive index at 20 ° C. exceeds 1.470, the traction coefficient increases, and a sufficient power saving effect cannot be obtained.

40 ° C. The kinematic viscosity of the lubricating oil composition of the present invention, in the JIS K2283 Kinematic Viscosity Test Method (40 ° C.), a 19~51mm ² / s, preferably 24~42mm ² / s, more preferably 28 ˜35 mm ² / s. When the 40 ° C. kinematic viscosity is less than 19 mm ² / s, an appropriate oil film thickness cannot be maintained, and the wear resistance tends to decrease. If the 40 ° C. kinematic viscosity exceeds 51 mm ² / s, the traction coefficient tends to increase and the power consumption tends to increase.

The viscosity index of the lubricating oil composition of the present invention is preferably 103 or more, more preferably 110 or more, still more preferably 120 or more, and particularly preferably 130 or more in the JIS K2283 kinematic viscosity test method. If the viscosity index is too low, the low-temperature viscosity tends to be high, and the power consumption during low-temperature starting tends to increase.

In the lubricating oil composition of the present invention, various known additives can be blended as necessary within a range that does not impair the object of the present invention. For example, antioxidants, extreme pressure agents, oily agents, detergent dispersants, rust inhibitors, metal deactivators, pour point depressants, foam depressants, demulsifiers and the like can be mentioned.
Antioxidants include phenol-based antioxidants such as 2,6-di-tert-butyl-p-cresol, amine-based antioxidants such as alkylated diphenylamine and alkylated phenyl-α-naphthylamine, phosphonic acid esters, etc. And phosphorus-based antioxidants.

Examples of the extreme pressure agent include phosphorus extreme pressure agents such as phosphate and phosphite, sulfur extreme pressure agents such as olefin sulfide, and organometallic extreme pressure agents such as ZnDTP and ZnDTC.
Examples of the oily agent include higher fatty acids such as oleic acid and stearic acid, higher alcohols such as oleyl alcohol, amines such as oleylamine, and esters such as butyl stearate.

Examples of the cleaning dispersant include ashless cleaning dispersants such as alkenyl succinimides and alkenyl succinic esters, and alkaline earth metal cleaning dispersants.
Examples of the rust inhibitor include carboxylic acid, metal soap, carboxylic acid amine salt, sulfonic acid metal salt, and partial ester of polyhydric alcohol.
Examples of metal deactivators include benzotriazole and derivatives thereof, and alkyl succinic acid derivatives.
Examples of the pour point depressant include polyalkyl methacrylate, polybutene, polyalkyl styrene, polyvinyl acetate, polyalkyl acrylate and the like.

Examples of antifoaming agents include silicone oil and ester-based antifoaming agents.
Examples of the demulsifier include demulsifiers such as an anionic surfactant, a cationic surfactant, and a nonionic surfactant.
These additives may be used alone or in combination of two or more.
Although the lubricating oil composition of the present invention can be applied to various applications, it can be particularly suitably used as an industrial lubricating oil such as hydraulic fluid, bearing oil, compressor oil, turbine oil, machine tool oil and the like.

Next, the present invention will be described more specifically with reference to examples. In addition, this invention is not restrict | limited at all by these examples.
The base oil and additive components used in the preparation of the lubricating oil composition in each Example and Comparative Example are as follows.

<Method for producing hydrocarbon-based lubricating base oil>
(1) The bottom oil obtained by atmospheric distillation of the hydrocarbon-based lubricating base oil crude oil of the example was treated with a vacuum distillation apparatus, and the vacuum gas oil obtained there was hydrotreated and hydrocracked. Then, the residue which removed the light part and the fuel part with the vacuum stripper was obtained. The residue was distilled under reduced pressure, and the resulting lubricating oil fraction was subjected to hydrodewaxing treatment and stabilization treatment. The hydrodewaxing treatment is performed under the conditions of a reaction pressure of 160 to 180 kg / cm ² G, a reaction temperature of 270 to 290 ° C., and LHSV of 0.9 to 1.1 h ⁻¹ , and the base oils (A-1) and (A− 2) was obtained.
The properties of the base oils (A-1) and (A-2) are shown below.

(A-1) Hydrocracked mineral oil (hydrocarbon base oil)
40 ° C. kinematic viscosity: 20.1mm ² / s, 100 ℃ kinematic viscosity: 4.3mm ² / s, a refractive index at 20 ℃: 1.463,40 density at ℃: 0.817,40 ℃, in 1.7GPa High-pressure viscosity: 2.1 × 10 ¹¹ cP,% CA: 0.6
(A-2) Hydrocracked mineral oil (hydrocarbon-based lubricating base oil)
40 ° C. kinematic viscosity: 13.2 mm ² / s, 100 ° C. kinematic viscosity: 3.2 mm ² / s, refractive index at 20 ° C .: 1.460, density at 40 ° C .: 0.820, 40 ° C., at 1.7 GPa High pressure viscosity: 1.7 × 10 ¹¹ cP,% CA: 0.9

(2) The base oil crude of the comparative example was distilled at atmospheric pressure, the residual oil after fractional distillation was fractionated under reduced pressure, and the resulting distillate was purified to paraffin-rich raffinate by a furfural solvent extraction method. Subsequently, the dewaxed oil obtained by dewaxing the raffinate was subjected to high-pressure hydrogenation. The high-pressure hydrogenation treatment was performed under the conditions of a reaction pressure of 170 kg / cm ² G, a reaction temperature of 325 ° C., and LHSV 0.36 h ⁻¹ using a catalyst having Mo and Ni supported on an alumina support. The properties of the obtained base oil (A-3) are shown below.
(A-3) Hydrorefined mineral oil (hydrocarbon lubricating base oil)
40 ° C. kinematic viscosity: 30.8mm ² / s, 100 ℃ kinematic viscosity: 5.4mm ² / s, a refractive index at 20 ℃: 1.472,40 density at ℃: 0.842,40 ℃, in 1.7GPa High pressure viscosity: 4.6 × 10 ¹² cP,% CA: 0.4

* The kinematic viscosity at 40 ° C. was measured by the JIS K2283 kinematic viscosity test method, the density was measured by the JIS K2249 density test method, and the refractive index at 20 ° C. was measured by the JIS K0062 refractive index measurement method. The high-pressure viscosity was calculated using the Barus equation. The viscosity pressure coefficient necessary for the calculation was calculated using the Ohno equation. The absolute viscosity can be calculated from kinematic viscosity / density, and calculated from the measured values at 40 ° C., respectively.
% CA was determined by ASTM D3238 ring analysis. The refractive index, density, molecular weight and sulfur content necessary for the calculation were measured by JIS K0062 refractive index measurement method, JIS K2249 density test method, ASTM D2502 molecular weight test method, and JIS K2541 sulfur content test method.

Viscosity index improver (B-1) An ethylene / propylene random copolymer (B-2) having a weight average molecular weight of 16,000, a refractive index of 1.473 at 20 ° C., and an ethylene / propylene molar ratio of 53:47 ) Ethylene / propylene random copolymer (B-3) having a weight average molecular weight of 5,000, a refractive index at 20 ° C. of 1.468, and an ethylene / propylene molar ratio of 53:47 The weight average molecular weight of 1,400 The ethylene-propylene random copolymer (B-4) having a refractive index of 1.461 at 20 ° C. and a molar ratio of ethylene / propylene of 53:47 is 125,000, and the refractive index at 20 ° C. is 1. 463, an ethylene / propylene random copolymer having an ethylene / propylene molar ratio of 55/45

(B-5) An ethylene / propylene random copolymer having a weight average molecular weight of 180,000, a refractive index at 20 ° C. of 1.476, and an ethylene / propylene molar ratio of 60/40.
(B-6) Polyisobutylene having a weight average molecular weight of 150,000 (B-7) Polymethacrylate having a weight average molecular weight of 22,000

* The refractive index at 20 ° C. was measured by the JIS K0062 refractive index measurement method.
The weight average molecular weight was measured by gel permeation chromatography and calculated in terms of polystyrene. Gel permeation chromatography is applied to the column
Three GPC LF-804s were used, THF was used for the moving layer, and a differential refraction detector was used for the detector.

(Evaluation methods)
The high-pressure viscosity of the hydrocarbon-based lubricating base oil, the viscosity index of the lubricating oil composition, the low temperature viscosity, and the traction coefficient were evaluated by the following evaluation methods.
<Low temperature viscosity>
The low temperature viscosity at −25 ° C. was evaluated by ASTM D4684 MRV low temperature viscosity.

<Traction coefficient>
The traction coefficient was evaluated with a four-cylinder fatigue friction tester.
A test piece having a material SUJ-2, an outer diameter of 40 mm, a width of 10 mm, and a surface roughness of 0.08 μm or less, a slip ratio of 5.3%, a maximum Hertz load of 1.7 GPa, an oil temperature of 40 ° C., and a test time of 5 The test was conducted in minutes.
<Abrasion resistance>
A shell four-ball test was conducted under the following test conditions, and the wear scar diameter was evaluated.
Test conditions Test piece: Steel (fixed ball)-Steel (rotating ball)
Number of revolutions:
1800 rpm
Load:
10kgf
test time :
30min

(Examples 1-6)
A lubricating oil composition was prepared by blending a viscosity index improver in the base oil in the proportion (mass%) shown in the upper part of Table 1. Various performances of these lubricating oil compositions were evaluated, and the results are shown in the lower part of Table 1.
(Comparative Examples 1-5)
A viscosity index improver was blended with the base oil in the proportion (mass%) shown in the upper part of the surface load to prepare a lubricating oil composition. Various performances of these lubricating oil compositions were evaluated, and the results are shown in the lower part of Table 2.

* Viscosity index: Measured by JIS K2283 kinematic viscosity test method.

* Viscosity index: Measured by JIS K2283 kinematic viscosity test method.

Examples 1 to 6 have lower traction coefficients than Comparative Example 1 in which polyisobutylene is blended, Comparative Example 2 in which polymethacrylate is blended, and Comparative Examples 3 and 4 that do not contain an olefin viscosity index improver. Moreover, Examples 1-6 have a low traction coefficient compared with the comparative example 5 which mix | blended the olefin type viscosity index improver with the base oil with a high pressure viscosity. Therefore, these embodiments can provide a power saving effect.
In addition, the low-temperature viscosity of the example is lower than that of the comparative example 4, and an effect of reducing power at the time of start-up can be obtained.

Claims (2)

Hydrocarbon base oil having a high-pressure viscosity of 1.0 × 10 ^{10 to} 2.0 × 10 ¹² cP at 40 ° C. and 1.7 GPa and a% CA of 5 or less by ring analysis (however, a poly α-olefin base oil) And an olefinic viscosity index improver comprising a copolymer of ethylene and a monomer other than ethylene, and a mixture of the base oil and the olefinic viscosity index improver A lubricating oil composition having a refractive index of 1.453 to 1.470 at 20 ° C. and a kinematic viscosity at 40 ° C. of 19 to 51 mm ² / s. The olefin-based viscosity index improver is a copolymer of ethylene and an olefin having 3 to 30 carbon atoms, and has a refractive index of 1.453 to 1.480 at 20 ° C. The lubricating oil composition described.