JP6718349B2 - Lubricating oil composition for continuously variable transmission - Google Patents

Description

The present invention relates to a lubricating oil composition for a continuously variable transmission, and more particularly to a lubricating oil composition suitable for a metal belt type continuously variable transmission for automobiles.

In recent years, various machines such as automobiles, construction machines, and agricultural machines are required to save energy, that is, to reduce fuel consumption, and devices such as engines and transmissions are required to contribute to energy saving.

One of the energy saving means in a transmission is to reduce the viscosity of lubricating oil. It is considered that by lowering the viscosity of the lubricating oil, the stirring resistance and the drag torque due to the viscous resistance of the lubricating oil are reduced, the power transmission efficiency is improved, and as a result, the fuel economy can be improved.

Another energy saving means in a transmission is reduction in size and weight of the transmission. The reduction in size and weight of the transmission will improve the fuel economy of vehicles equipped with the transmission. Especially for continuously variable transmissions (for example, metal belt type continuously variable transmissions), if the friction coefficient between metals can be increased, the transmission can be downsized. It is desirable to have the property of maintaining a high coefficient of friction between metals.

JP, 2014-196396, A Japanese Patent No. 4663843

When the viscosity of the lubricating oil is reduced, the oil film thickness on the lubricating surface is reduced. It is considered that the reduction of the oil film thickness in the mixed lubrication region is advantageous from the viewpoint of increasing the friction coefficient between metals. However, when the oil film thickness on the lubricated surface decreases, seizure resistance and wear resistance decrease, and the fatigue life tends to decrease.

The present invention provides a lubricating oil composition for a continuously variable transmission, which satisfies the requirements for seizure resistance, wear resistance, and fatigue life required for continuously variable transmission oil, while improving fuel economy and metal-to-metal friction coefficient. This is an issue.

One embodiment of the present invention comprises (A) a lubricating base oil and (B) a borate ester compound in a total amount of the lubricating oil composition of 25 mass ppm or more and 500 mass ppm as a boron amount (boron atom equivalent amount). The following, (C) phosphoric acid is 100 mass ppm or more and 750 mass ppm or less as a phosphorus amount (phosphorus atom conversion amount) on the basis of the total amount of the lubricating oil composition, and (D) poly(meta having a weight average molecular weight of 100,000 or less ) An acrylate, and a lubricating oil composition for a continuously variable transmission, wherein the lubricating oil composition has a kinematic viscosity at 40° C. of 25 mm ² /s or less.

In the present specification, the “(meth)acrylate” means “acrylate and/or methacrylate”.

The lubricating oil composition for continuously variable transmission further contains (E) a thiadiazole compound in an amount of 180 mass ppm or more and 900 mass ppm or less as a sulfur amount (sulfur atom equivalent amount) based on the total amount of the lubricating oil composition, In the lubricating oil composition, the sum of the boron content B (unit: mass ppm) derived from the component (B) in the composition and the phosphorus content P (unit: mass ppm) in the lubricating oil composition. The ratio (B+P)/S with respect to the sulfur content S (unit: mass ppm) derived from the component (E) is preferably 1 or more and 3 or less.

In the lubricating oil composition for continuously variable transmission, the lubricating oil base oil (A) has (A1) a kinematic viscosity at 100° C. of 2.8 mm ² /s or less, a viscosity index of 110 or more, and a% C _P of 90. API group III containing 30% by mass or more and 100% by mass or less of the above base oil based on the total amount of the lubricating base oil, and (A2) having a kinematic viscosity at 100° C. of 3 mm ² /s or more and 10 mm ² /s or less. 70% by mass or less of a base oil or a group IV base oil or a mixed base oil thereof based on the total amount of the lubricating base oil, or a base oil other than the base oils (A1) and (A2) Is 0 to 4 mass% based on the total amount of the lubricating base oil, and the kinematic viscosity of the lubricating base oil (A) at 100° C. is preferably 3.4 mm ² /s or less.

In the lubricating oil composition for continuously variable transmission, the component (B) is preferably one or more borate ester compounds represented by the following general formula (1).

(In the general formula (1), R ¹ is a hydrocarbyl group having 1 to 30 carbon atoms, and R ² and R ³ are each independently a hydrogen atom or a hydrocarbyl group having 1 to 30 carbon atoms.)

According to the present invention, there is provided a lubricating oil composition for a continuously variable transmission, which has improved seizure resistance, wear resistance, and fatigue life required for continuously variable transmission oil, and which has improved fuel economy and friction coefficient between metals. Can be provided.

Hereinafter, the present invention will be described in detail. Unless otherwise specified, the notation “A to B” for the numerical values A and B means “A or more and B or less”. When a unit is attached only to the numerical value B in this notation, the unit is also applied to the numerical value A. The terms "or" and "or" mean logical sum unless otherwise specified.

<(A) Lubricating base oil>
In the lubricating oil composition for a continuously variable transmission of the present invention (hereinafter sometimes referred to as "continuously variable transmission oil" or "lubricating oil composition"), the lubricating base oil is a mineral base oil or a synthetic base oil. A base oil comprising at least one selected from base oils can be used without particular limitation.

Specific examples of the mineral oil-based base oil include solvent degassing, solvent extraction, and hydrogenation of the lubricating oil fraction obtained by distilling the crude oil under atmospheric pressure and distilling the atmospheric residual oil under reduced pressure. Paraffinic or naphthenic mineral base oil obtained by performing one or more purification treatments such as cracking, hydroisomerization, solvent dewaxing, catalytic dewaxing, hydrorefining, and wax isomerized mineral oil, GTL Examples include base oils produced by the method of isomerizing WAX (gas liquid wax).

As the mineral oil-based base oil, wax isomerization obtained by isomerizing a raw material containing 50% by mass or more of hydrocracked mineral oil-based base oil and/or petroleum-based wax or GTL wax (for example, Fischer-Tropsch synthetic oil) Isoparaffinic base oil can be preferably used.

Examples of synthetic base oils include poly-α-olefins (eg, ethylene-propylene copolymer, polybutene, 1-octene oligomer, 1-decene oligomer, etc.) or hydrides thereof; monoesters (eg, butyl stearate, octyl). Laurate, etc.); Diester (eg, ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sepaate, etc.); Polyester (eg trimellitic acid ester, etc.); Polyol Esters (eg, trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate, etc.); Aromatic synthetic oils (eg, alkylbenzene, alkylnaphthalene, aromatic esters, etc.). ); and mixtures thereof.

The% C _P of the mineral oil base oil is preferably 70 or more, more preferably 80 or more, and usually 99 or less, preferably 95 or less. When the% C _P of the mineral oil-based base oil is at least the above lower limit value, it becomes possible to improve the viscosity-temperature characteristics, thermal/oxidation stability and friction characteristics. Further, when the% C _p of the lubricating base oil is not more than the above upper limit value, the solubility of the additive can be increased.

The% C _A of the mineral oil-based base oil is preferably 2 or less, more preferably 1 or less, still more preferably 0.8 or less, and particularly preferably 0.5 or less. By% C _A of the mineral base oil is more than the above upper limit, the viscosity - it is possible to increase the temperature characteristics, thermal and oxidation stability and fuel efficiency.

The% C _N of the mineral oil base oil is preferably 30 or less, more preferably 25 or less, preferably 1 or more, more preferably 4 or more. When the% C _N of the mineral oil-based base oil is equal to or less than the above upper limit value, it becomes possible to enhance the viscosity-temperature characteristic, the heat/oxidation stability and the friction characteristic. Further, when % _CN is at least the above lower limit value, the solubility of the additive can be enhanced.

In the present specification,% C _P ,% C _N and% C _A are the percentages of the paraffin carbon number to the total carbon number, which are determined by the method (ndM ring analysis) according to ASTM D 3238-85, respectively. , Naphthene carbon number to total carbon number, and aromatic carbon number to total carbon number. That is, the above-mentioned preferable ranges of %C _P , %C _N and %C _A are based on the values obtained by the above method. For example, even mineral oil-based base oils containing no naphthene are obtained by the above method. The% C _N given may show values above 0.

The kinematic viscosity of the lubricating base oil at 100° C. is preferably 6.0 mm ² /s or less, more preferably 4.5 mm ² /s or less, particularly preferably 3.4 mm ² /s or less, and preferably 2 .0mm ² / s or more, more preferably 2.5 mm ² / s or more, particularly preferably 2.6 mm ² / s or more. When the kinematic viscosity of the base oil at 100° C. is not more than the above upper limit value, it becomes possible to improve the low temperature viscosity characteristics of the lubricating oil composition and to improve fuel economy. When the kinematic viscosity of the base oil at 100° C. is equal to or higher than the lower limit value described above, it becomes possible to sufficiently form an oil film at the lubricated portion and enhance the lubricity. In addition, in this specification, "kinematic viscosity at 100 degreeC" means the kinematic viscosity at 100 degreeC prescribed|regulated to ASTM D-445.

The kinematic viscosity of the lubricating base oil at 40° C. is preferably 40 mm ² /s or less, more preferably 30 mm ² /s or less, further preferably 25 mm ² /s or less, particularly preferably 20 mm ² /s or less, and It is preferably 8.0 mm ² /s or more, more preferably 8.5 mm ² /s or more, and particularly preferably 9.0 mm ² /s or more. When the kinematic viscosity of the lubricating base oil at 40° C. is not more than the above upper limit value, it becomes possible to improve the low temperature viscosity characteristics of the lubricating oil composition and to improve fuel economy. Further, since the kinematic viscosity of the base oil at 40° C. is equal to or higher than the above lower limit value, it becomes possible to sufficiently form an oil film at the lubricated portion and enhance lubricity. In the present specification, the "kinematic viscosity at 40°C" means the kinematic viscosity at 40°C specified in ASTM D-445.

The viscosity index of the lubricating base oil is preferably 100 or more. It is more preferably 110 or more, still more preferably 115 or more. When the viscosity index of the base oil is not less than the above lower limit value, not only the viscosity-temperature characteristic and heat/oxidation stability of the lubricating oil composition can be improved, but also the antiwear property can be enhanced. In addition, in this specification, a viscosity index means the viscosity index measured based on JISK2283-1993.

The pour point of the lubricating base oil is preferably -10°C or lower, more preferably -12.5°C or lower, further preferably -15°C or lower, particularly preferably -17.5°C or lower, and most preferably -20. It is 0°C or lower. When the pour point exceeds the above upper limit, the low temperature fluidity of the entire lubricating oil composition tends to decrease. In addition, in this specification, a pour point means the pour point measured based on JISK2269-1987.

The content of sulfur in the lubricating base oil is preferably 1.5% by mass or less, and more preferably 1.0% by mass or less, from the viewpoint of oxidation stability.

The lubricating base oil in the lubricating oil composition of the present invention,
(A1) Base oil having a kinematic viscosity at 100° C. of 2.8 mm ² /s or less, a viscosity index of 110 or more, and a% _CP of 90 or more is contained in an amount of 30% by mass or more and 100% by mass or less based on the total amount of the lubricating base oil. And
(A2) API group III base oil or group IV base oil or mixed base oil thereof having a kinematic viscosity at 100° C. of 3 mm ² /s or more and 10 mm ² /s or less, 70% by mass or less based on the total amount of the lubricating base oil. With or without
The content of the base oil other than the base oils (A1) and (A2) is 0 to 4% by mass based on the total amount of the lubricating base oil, and the kinematic viscosity at 100° C. is 3.4 mm ² /s or less. Hereinafter, it may be referred to as “the lubricating base oil according to the present embodiment”). By using the lubricant base oil according to the present embodiment as the lubricant base oil, it is possible to reduce the oil film thickness in the transition region (mixed lubrication region) from the fluid lubrication region to the boundary lubrication region and increase the intermetallic friction coefficient. Will be possible.

The kinematic viscosity of the base oil (A1) at 100° C. is 2.8 mm ² /s or less, preferably 2.7 mm ² /s or less. Further, it is preferably 1.5 mm ² /s or more, more preferably 2.0 mm ² /s or more. When the kinematic viscosity of the base oil (A1) at 100° C. is not more than the above upper limit value, it becomes possible to increase the coefficient of friction between metals. Further, when the kinematic viscosity of the base oil (A1) at 100° C. is equal to or higher than the above lower limit value, it becomes possible to sufficiently form the oil film at the lubricated portion and enhance the lubricity.

The kinematic viscosity of the base oil (A1) at 40° C. is preferably 15 mm ² /s or less, more preferably 10 mm ² /s or less, and preferably 2.0 mm ² /s or more, more preferably 5.0 mm ² /S or more. When the kinematic viscosity of the base oil (A1) at 40° C. is not more than the above upper limit value, it becomes easy to increase the intermetallic friction coefficient. Further, when the kinematic viscosity of the base oil (A1) at 40° C. is equal to or higher than the above lower limit value, it becomes possible to sufficiently form an oil film at the lubricated portion and enhance the lubricity.

The viscosity index of the base oil (A1) is 110 or more. When the viscosity index of the base oil (A1) is 110 or more, it becomes easy to increase the intermetallic friction coefficient. The upper limit is not particularly limited, but is usually 150 or less, preferably 135 or less.

The% C _P of the base oil (A1) is 90 or more. When the% C _P of the base oil (A1) is 90 or more, the heat/oxidation stability becomes good. The upper limit is not particularly limited, but is usually 99 or less, and preferably 95 or less from the viewpoint of solubility of the additive.

The% C _A of the base oil (A1) is preferably 1 or less, more preferably 0.8 or less, particularly preferably 0.5 or less, and may be 0. By% C _A of base oil (A1) is more than the above upper limit, the viscosity - it is possible to increase the temperature characteristics, thermal and oxidation stability and fuel efficiency.

As the base oil (A1), a mineral oil-based base oil having the above properties can be used without particular limitation.

The kinematic viscosity of the base oil (A2) at 100° C. is 3 to 10 mm ² /s or less, preferably 8.0 mm ² /s or less, more preferably 6.0 mm ² /s or less, and further preferably 4.5 mm ² /S or less. When the kinematic viscosity of the base oil (A2) at 100° C. is not more than the above upper limit value, the coefficient of friction between metals can be increased. Further, when the kinematic viscosity of the base oil (A2) at 100° C. is equal to or higher than the above lower limit value, it becomes possible to sufficiently form an oil film at the lubricated portion and enhance the lubricity.

The base oil (A2) is a Group III base oil or Group IV base oil of API classification, or a mixed base oil thereof, and preferably a Group III base oil. The Group III base oil is a mineral base oil having a sulfur content of 0.03 mass% or less, a saturated content of 90 mass% or more, and a viscosity index of 120 or more. Group IV base oils are poly alpha-olefins.

The content of the base oil (A1) in the lubricating base oil according to the present embodiment is 30% by mass or more, preferably 35% by mass or more, and even 100% by mass, based on the total amount of the lubricating base oil. Good. In the present specification, the content of the base oil (A1) being 100% by mass based on the total amount of the lubricating base oil means that the lubricating base oil is composed of the base oil (A1).
The content of the base oil (A2) in the lubricating base oil according to the present embodiment is 70% by mass or less, preferably 65% by mass or less, and even 0% by mass, based on the total amount of the lubricating base oil. Good. In the present specification, the content of the base oil (A2) being 0% by mass means that the lubricating base oil does not contain the base oil (A2).
The content of the base oil other than the base oils (A1) and (A2) in the lubricating base oil according to the present embodiment is 4% by mass or less, preferably 1% by mass or less, based on the total amount of the lubricating base oil. , 0 mass% may be sufficient. In the present specification, the content of the base oil other than the base oils (A1) and (A2) is 0% by mass means that the lubricating base oil is the base oil (A1) and (optionally) the base oil (A2). ) Is meant to consist of.

<(B) boric acid ester compound>
The lubricating oil composition of the present invention contains a borate ester compound (hereinafter sometimes referred to as “component (B)”).

As the component (B), one or more borate ester compounds represented by the following general formula (1) can be used.

(In the general formula (1), R ¹ is a hydrocarbyl group having 1 to 30 carbon atoms, and R ² and R ³ are each independently a hydrogen atom or a hydrocarbyl group having 1 to 30 carbon atoms.)

As the hydrocarbyl group, an alkyl group (which may have a ring structure), an alkenyl group (the position of the double bond is optional and may have a ring structure), an aryl group, an alkylaryl group , Alkenylaryl groups, arylalkyl groups, arylalkenyl groups and the like.

Examples of the alkyl group include various linear or branched alkyl groups. Examples of the alkyl group having a ring structure include an alkylcycloalkyl group and a cycloalkylalkyl group. Examples of the cycloalkyl group include cycloalkyl groups having 5 to 7 carbon atoms such as cyclopentyl group, cyclohexyl group, and cycloheptyl group. Further, the substitution position on the cycloalkyl ring is arbitrary.

Examples of the alkenyl group include various linear or branched alkenyl groups. Examples of the alkenyl group having a ring structure include an alkylcycloalkenyl group, an alkenylcycloalkyl group, a cycloalkenylalkyl group and a cycloalkenylalkenyl group. The cycloalkyl group is the same as above. Examples of the cycloalkenyl group include cycloalkyl groups having 5 to 7 carbon atoms such as cyclopentenyl group, cyclohexenyl group and cycloheptenyl group. Further, the substitution position on the cycloalkenyl ring and the cycloalkyl ring is arbitrary.

Examples of the aryl group include a phenyl group and a naphthyl group. The aryl group may have a hydrocarbyl substituent. Further, in the above alkylaryl group, alkenylaryl group, arylalkyl group, and arylalkenyl group, the position of substitution with the aryl group is arbitrary.

The hydrocarbyl group having 1 to 30 carbon atoms in the general formula (1) is preferably an alkyl or alkenyl group, and more preferably an alkyl group. The carbon number is preferably 3 or more, more preferably 5 or more. It is preferably 24 or less, more preferably 12 or less. When the number of carbon atoms of the hydrocarbyl group is at least the above lower limit value, it becomes possible to enhance the solubility and enhance the coefficient of friction between metals. When the carbon number of the hydrocarbyl group exceeds the above upper limit, the coefficient of friction between metals tends to decrease.

In the general formula (1), it is preferable that at least one of R ² and R ³ are hydrogen atoms, and more preferably both R ² and R ³ are hydrogen atoms. By using the component (B) in such a form, it is possible to increase the strength of the lubricating film in the boundary lubrication region and improve seizure resistance and wear resistance.

As a preferred example of the component (B), there may be mentioned a boric acid ester in which R ¹ is an alkyl or alkenyl group having 3 to 12 carbon atoms and R ² and R ³ are hydrogen atoms in the general formula (1). it can.

The content of the component (B) in the lubricating oil composition is, based on the total amount of the lubricating oil composition, 25 to 500 mass ppm as a boron amount (boron atom equivalent amount), preferably 400 mass ppm or less, and more preferably It is 300 mass ppm or less. When the content of the component (B) is at least the above lower limit value, the strength of the lubricating film in the boundary lubrication region can be increased, and the seizure resistance and wear resistance can be improved. Further, when the content of the component (B) is not more than the above upper limit value, the strength of the lubricating film in the boundary lubrication region can be increased, and seizure resistance and fatigue life can be improved.

<(C) Phosphoric acid>
The lubricating oil composition of the present invention contains phosphoric acid (hereinafter sometimes referred to as “(C) component”).

As the component (C), one or more kinds of phosphoric acid selected from orthophosphoric acid, pyrophosphoric acid, condensed phosphoric acid, and metaphosphoric acid can be used. As the component (C), orthophosphoric acid and/or metaphosphoric acid are preferable, and orthophosphoric acid is particularly preferable.

The content of the component (C) in the lubricating oil composition is 100 to 750 mass ppm as a phosphorus amount (phosphorus atom conversion amount), preferably 120 mass ppm or more, and particularly preferably, based on the total amount of the lubricating oil composition. It is 140 mass ppm or more. When the content of the component (C) is at least the above lower limit value, the strength of the lubricating film in the boundary lubrication region can be increased, and the seizure resistance and wear resistance can be improved. When the content of the component (C) is not more than the above upper limit value, the strength of the lubricating film in the boundary lubrication region can be increased, and the seizure resistance and the fatigue life can be improved.

<(D) Poly(meth)acrylate>
The lubricating oil composition of the present invention contains a poly(meth)acrylate having a weight average molecular weight of 100,000 or less (hereinafter sometimes referred to as "(D) component"). In addition, in this specification, "(meth)acrylate" means "acrylate and/or methacrylate."

The component (D) may be a dispersion type poly(meth)acrylate or a non-dispersion type poly(meth)acrylate. The weight average molecular weight of the component (D) is 100,000 or less, preferably 80,000 or less, more preferably 60,000 or less, and preferably 10,000 or more, more preferably 15,000 or more. .. When the weight average molecular weight of the component (D) is not more than the above upper limit value, it becomes possible to enhance the shear stability of the lubricating oil composition. When the weight average molecular weight of the component (D) is at least the above lower limit, it becomes easy to increase the viscosity index of the lubricating oil composition.

The component (D) acts as a viscosity index improver. The content of the component (D) in the lubricating oil composition can be such that the kinematic viscosity of the lubricating oil composition at 40° C. falls within the range described below. Although the specific content varies depending on the weight average molecular weight of the component (D), it may be, for example, 5 to 20% by mass based on the total amount of the lubricating oil composition (100% by mass).

<(E) thiadiazole compound>
The lubricating oil composition of the present invention preferably contains one or more thiadiazole compounds (hereinafter sometimes referred to as “(E) component”).

Examples of the component (E) include 1,3,4-thiadiazole represented by the following general formula (2), 1,2,4-thiadiazole compound represented by the following general formula (3), and the following general formula. 1 is represented by (4), 2,3 - can be exemplified thiadiazole compound.

(In the general formulas (2) to (4), R ⁴ and R ⁵ may be the same or different and each independently represent hydrogen or a hydrocarbyl group having 1 to 20 carbon atoms; and a and b are the same or different. May represent each independently an integer of 0-8.)

Among the above thiadiazole compounds, a thiadiazole compound represented by any of the above general formulas (2) to (4) and having a hydrocarbyldithio group can be particularly preferably used.

The content of the component (E) in the lubricating oil composition is 180 to 900 mass ppm, and preferably 300 to 900 mass ppm, as the amount of sulfur (sulfur atom equivalent) based on the total amount of the lubricating oil composition. When the content of the component (E) is at least the above lower limit value, it becomes easy to increase seizure resistance, wear resistance, fatigue life, and intermetallic friction coefficient. Further, when the content of the component (E) is not more than the above upper limit value, it becomes easy to enhance seizure resistance and fatigue life.

When the lubricating oil composition contains the component (E), the boron content B (unit: mass ppm) derived from the component (B) in the lubricating oil composition and the total phosphorus content P(in the lubricating oil composition The ratio (B+P)/S of the sum of (unit: mass ppm) to the sulfur content S (unit: mass ppm) derived from the component (E) in the lubricating oil composition is preferably 1 to 3, and more preferably It is preferably 1.2 or more, more preferably 1.4 or more, more preferably 2.7 or less, further preferably 2.4 or less, even more preferably 2.2 or less, particularly preferably 2.0 or less. , And most preferably 1.8 or less. When the ratio (B+P)/S is at least the above lower limit value, it becomes easy to enhance seizure resistance and fatigue life. Further, when the ratio (B+P)/S is not more than the above upper limit value, it becomes easy to increase seizure resistance, wear resistance, fatigue life, and intermetallic friction coefficient.

<(F) Metallic detergent>
In one preferred embodiment, the lubricating oil composition may further contain a metallic detergent (hereinafter sometimes referred to as “(F) component”).

As the component (F), known metal-based detergents such as sulfonate-based detergents, phenate-based detergents and salicylate-based detergents can be used, and sulfonate and/or salicylate-based detergents can be preferably used.

Preferable examples of the sulfonate-based detergent include alkaline earth metal salts of alkylaromatic sulfonic acids obtained by sulfonation of alkylaromatic compounds, or basic salts or overbased salts thereof. The weight average molecular weight of the alkyl aromatic compound is preferably 400 to 1500, more preferably 700 to 1300.
Examples of the alkaline earth metal include magnesium, barium, and calcium, and magnesium or calcium is preferable. Examples of the alkyl aromatic sulfonic acid include so-called petroleum sulfonic acid and synthetic sulfonic acid. Examples of the petroleum sulfonic acid used herein include those obtained by sulfonation of an alkyl aromatic compound of a lubricating oil fraction of mineral oil, and so-called mahogany acid produced as a by-product during the production of white oil. Further, as an example of the synthetic sulfonic acid, a linear or branched alkyl obtained by recovering a by-product in an alkylbenzene production plant which is a raw material of a detergent or by alkylating benzene with a polyolefin. The thing which sulfonated the alkylbenzene which has a group can be mentioned. As another example of the synthetic sulfonic acid, an alkylnaphthalene such as dinonylnaphthalene may be sulfonated. The sulfonating agent used for sulfonating these alkyl aromatic compounds is not particularly limited, and fuming sulfuric acid or sulfuric anhydride can be used, for example.

Preferable examples of the phenate-based detergent include an overbased salt of an alkaline earth metal salt of a compound having a structure represented by the following general formula (10).

In the formula (5), R ⁶ represents a linear or branched chain having ⁶ to 21 carbon atoms, a saturated or unsaturated alkyl group or alkenyl group, c represents a degree of polymerization and represents an integer of 1 to 10, and A the sulfide (-S-) group or a methylene (-CH ₂ -) represents a group, d is an integer of 1-3. R ⁶ may be a combination of two or more different groups.

The carbon number of R ⁶ in formula (5) is preferably 9 to 18, and more preferably 9 to 15. When the carbon number of R ⁶ is less than 6, the solubility in the base oil may be poor, while when the carbon number of R ⁶ exceeds 21, the production may be difficult and the heat resistance may be poor.

The polymerization degree c in the formula (5) is preferably 1 to 3. When the polymerization degree c is within this range, heat resistance can be improved.

Preferred examples of salicylate detergents include alkaline earth metal salicylates or their basic or overbased salts. Preferred examples of alkaline earth metal salicylates include compounds represented by the following general formula (6).

In formula (6), R ^7's each independently represent an alkyl group or an alkenyl group having 14 to 30 carbon atoms. e represents 1 or 2, and is preferably 1. When e=2, R ⁷ may be a combination of different groups. M represents an alkaline earth metal, preferably calcium or magnesium.

The method for producing the alkaline earth metal salicylate is not particularly limited, and a known method for producing monoalkyl salicylate or the like can be used. For example, phenol is used as a starting material, alkylation is performed using an olefin, and then monoalkyl salicylic acid obtained by carboxylation with carbon dioxide gas or the like, or salicylic acid is used as a starting material, and an equivalent amount of the above olefin is used for alkylation. The obtained monoalkylsalicylic acid or the like is reacted with a metal base such as an oxide or hydroxide of an alkaline earth metal, or these monoalkylsalicylic acid or the like is once converted into an alkali metal salt such as a sodium salt or a potassium salt. Alkaline earth metal salicylate can be obtained by subjecting the above to metal exchange with an alkaline earth metal salt.

The component (F) may be overbased. The method for obtaining the overbased calcium sulfonate, phenate, or salicylate is not particularly limited, but for example, alkaline earth metal sulfonate, phenate, or salicylate in the presence of carbon dioxide can be used for calcium hydroxide, hydroxylation. It can be obtained by reacting with a base such as magnesium.

When the lubricating oil composition contains the component (F), the content thereof is preferably 100 to 1200 mass ppm as a metal amount (metal element conversion amount), and more preferably 200, based on the total amount of the lubricating oil composition. It is at least ppm by mass, and more preferably at most 1,000 ppm by mass. When the content of the component (F) is within the above range, it becomes possible to further improve the friction characteristics of the wet clutch.

<(G) Ashless dispersant>
In one preferred embodiment, the lubricating oil composition may further comprise an ashless dispersant (hereinafter sometimes referred to as "(G) component").

As the component (G), for example, one or more compounds selected from the following (G-1) to (G-3) can be used.
(G-1) Succinimide having at least one alkyl group or alkenyl group in the molecule or a derivative thereof (hereinafter sometimes referred to as "(G-1) component"),
(G-2) Benzylamine having at least one alkyl group or alkenyl group in the molecule or a derivative thereof (hereinafter sometimes referred to as "(G-2) component"),
(G-3) A polyamine having at least one alkyl group or alkenyl group in the molecule or a derivative thereof (hereinafter sometimes referred to as "(G-3) component").

As the component (G), the component (G-1) can be particularly preferably used.
Among the component (G-1), examples of the succinimide having at least one alkyl group or alkenyl group in the molecule include compounds represented by the following general formula (7) or (8).

In the formula (7), R ⁸ represents an alkyl group or an alkenyl group having 40 to 400 carbon atoms, and f represents an integer of 1 to 5, preferably 2 to 4. The carbon number of R ⁸ is preferably 60 or more, and preferably 350 or less.

In formula (8), R ⁹ and R ¹⁰ each independently represent an alkyl group or an alkenyl group having 40 to 400 carbon atoms, and may be a combination of different groups. R ⁹ and R ¹⁰ are particularly preferably polybutenyl groups. Further, g represents an integer of 0 to 4, preferably 1 to 3. The carbon number of R ⁹ and R ¹⁰ is preferably 60 or more, and preferably 350 or less.

By the number of carbon atoms of R ⁸ to R ¹⁰ in the formula (7) and (8) is less than the above lower limit, it is possible to obtain good solubility in the lubricating base oil. On the other hand, when the carbon number of R ^{8 to} R ¹⁰ is not more than the above upper limit value, the low temperature fluidity of the lubricating oil composition can be enhanced.

The alkyl group or alkenyl group (R ^{8 to} R ¹⁰ ) in formulas (7) and (8) may be linear or branched, and is preferably an oligomer of an olefin such as propylene, 1-butene or isobutene. And a branched alkyl group or a branched alkenyl group derived from a co-oligomer of ethylene and propylene. Among them, a branched alkyl group or alkenyl group derived from an oligomer of isobutene which is conventionally called polyisobutylene, and a polybutenyl group are most preferable.
A suitable number average molecular weight of the alkyl group or the alkenyl group (R ^{8 to} R ¹⁰ ) in the formulas (7) and (8) is 800 to 3500.

The succinimide having at least one alkyl group or alkenyl group in the molecule is a so-called monotype succinimide represented by the formula (7) in which succinic anhydride is added to only one end of a polyamine chain. And a so-called bis-type succinimide represented by the formula (8) in which succinic anhydride is added to both ends of a polyamine chain. The lubricating oil composition may contain either a monotype succinimide or a bis type succinimide, or both of them may be contained as a mixture.

The method for producing the succinimide having at least one alkyl group or alkenyl group in the molecule is not particularly limited, and for example, a compound having an alkyl group or alkenyl group having 40 to 400 carbon atoms may be mixed with maleic anhydride and 100 It can be obtained by reacting an alkylsuccinic acid or an alkenylsuccinic acid obtained by reacting at ˜200° C. with a polyamine. Here, examples of the polyamine include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine.

Among the component (G-2), examples of the benzylamine having at least one alkyl group or alkenyl group in the molecule include compounds represented by the following general formula (9).

In formula (9), R ¹¹ represents an alkyl group or an alkenyl group having 40 to 400 carbon atoms, and h represents an integer of 1 to 5, preferably 2 to 4. The carbon number of R ¹¹ is preferably 60 or more, and preferably 350 or less.

The method for producing the component (G-2) is not particularly limited. For example, propylene oligomer, polybutene, or polyolefin such as ethylene-α-olefin copolymer is reacted with phenol to form an alkylphenol, and then formaldehyde, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine are added thereto. A method of reacting with a polyamine such as by a Mannich reaction can be mentioned.

Examples of the polyamine having at least one alkyl group or alkenyl group in the component (G-3) include compounds represented by the following formula (10).

In the formula (10), R ¹² represents an alkyl group or an alkenyl group having 40 to 400 carbon atoms, and i represents an integer of 1 to 5, preferably 2 to 4. The carbon number of R ¹² is preferably 60 or more, and preferably 350 or less.

The method for producing the component (G-3) is not particularly limited. For example, after chlorinating a polyolefin such as propylene oligomer, polybutene or ethylene-α-olefin copolymer, this is reacted with a polyamine such as ammonia or ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine. There is a method.

Examples of the derivative in the components (G-1) to (G-3) include (i) a succinimide, a benzylamine or a polyamine having at least one alkyl group or alkenyl group described above in the molecule (hereinafter referred to as “the above-mentioned”). "Nitrogen-containing compound"), a monocarboxylic acid having 1 to 30 carbon atoms such as a fatty acid, and a polycarboxylic acid having 2 to 30 carbon atoms (for example, oxalic acid, phthalic acid, trimellitic acid, pyromellitic acid, etc.). , These anhydrides or ester compounds, alkylene oxides having 2 to 6 carbon atoms, or hydroxy(poly)oxyalkylene carbonate are allowed to act to neutralize some or all of the remaining amino groups and/or imino groups. Or a modified compound with an oxygen-containing organic compound which is amidated; (ii) by reacting boric acid with the above-mentioned nitrogen-containing compound, a part or all of the remaining amino group and/or imino group is neutralized or Amidated, boron-modified compound; (iii) A part or all of the remaining amino group and/or imino group is neutralized or amidated by reacting the above nitrogen-containing compound with phosphoric acid. A phosphoric acid-modified compound; (iv) a sulfur-modified compound obtained by reacting the above-mentioned nitrogen-containing compound with a sulfur compound; and (v) a modification of the above-mentioned nitrogen-containing compound with an oxygen-containing organic compound, boron-modified, A modified compound obtained by combining two or more kinds of modifications selected from phosphoric acid modification and sulfur modification is mentioned. Among these derivatives (i) to (v), it is preferable to use the boron-modified compound as the component (G-1) because the heat resistance of the lubricating oil composition can be further improved.

The molecular weight of the component (G) is not particularly limited, but a suitable weight average molecular weight is 1,000 to 20,000.

When the lubricating oil composition contains the component (G), the content thereof is preferably 100 to 2000 mass ppm as nitrogen content, more preferably 500 mass ppm or more, and further more, based on the total amount of the lubricating oil composition. It is preferably 1000 mass ppm or less. When the content of the component (G) is at least the above lower limit value, it becomes possible to improve the caulking resistance (heat resistance) of the lubricating oil composition. Further, when the content of the component (G) is not more than the above upper limit value, it becomes possible to further improve fuel economy.

When a boron-modified compound is used as the component (G), the amount of boron derived from the component (G) in the lubricating oil composition is preferably 50 to 500 mass ppm, more preferably 100, based on the total amount of the lubricating oil composition. It is at least ppm by mass, and more preferably at most 300 ppm by mass. When the boron content derived from the component (G) is at most the above upper limit value, it becomes possible to further improve fuel economy.

<(H) Phosphorus antiwear agent>
In one preferred embodiment, the lubricating oil composition may further contain a phosphorus antiwear agent (hereinafter sometimes referred to as “(H) component”). As the component (H), one type may be used alone, or two or more types may be used in combination.

Examples of the component (H) include zinc dialkyldithiophosphate, phosphoric acid monoester, phosphoric acid diester, phosphoric acid triester, phosphorous acid monoester, phosphorous acid diester, phosphorous acid triester, incomplete phosphoric acid ester. Can be mentioned, salts of incomplete phosphite esters, and mixtures thereof.

Of the above examples, the compounds other than phosphorous acid are usually compounds having a hydrocarbon group of 2 to 30, preferably 3 to 20 carbon atoms. Specific examples of the hydrocarbon group having 2 to 30 carbon atoms include an alkyl group, a cycloalkyl group, an alkyl-substituted cycloalkyl group, an alkenyl group, an aryl group, an alkyl-substituted aryl group, and an aryl-substituted alkyl group. Can be mentioned. These alkyl groups may be linear or branched.

Examples of the salt of incomplete phosphoric acid ester and the salt of incomplete phosphorous acid ester include phosphoric acid monoester, phosphoric acid diester, phosphorous acid monoester, or phosphorous acid diester, or a mixture thereof. By reacting a nitrogen-containing compound such as an amine compound containing ammonia or a hydrocarbon group having 1 to 8 carbon atoms or a hydrocarbon group containing a hydroxy group in the molecule, a part or all of the remaining acidic hydrogen is removed. Mention may be made of neutralized salts.

As the component (H), phosphite esters or salts thereof can be preferably used, and phosphite incomplete esters or salts thereof are more preferable, and phosphite incomplete having a hydrocarbon group having 8 or less carbon atoms. Esters or salts thereof are particularly preferred.

When the lubricating oil composition contains the component (H), the content thereof is preferably 100 to 2000 mass ppm as a phosphorus amount, more preferably 200 mass ppm or more, and further more, based on the total amount of the lubricating oil composition. It is preferably 1000 mass ppm or less. When the content of the component (H) is at least the above lower limit value, it becomes possible to further increase wear resistance and intermetallic friction coefficient. Further, when the content of the component (H) is not more than the above upper limit value, it becomes possible to enhance the oxidation stability and the seal compatibility.

<(I) Friction modifier>
In one preferred embodiment, the lubricating oil composition may further contain a friction modifier (hereinafter sometimes referred to as “(I) component”). As the component (I), one type may be used alone, or two or more types may be used in combination.

As the component (I), a compound used as a friction modifier in the field of lubricating oil can be used without particular limitation. Examples of the friction modifier include compounds having 6 to 50 carbon atoms, which contain at least one hetero element selected from oxygen atom, nitrogen atom and sulfur atom in the molecule. More specifically, an aliphatic amine compound, an aliphatic imide compound, a fatty acid ester, a fatty acid amide, a fatty acid hydrazide, a fatty acid having at least one linear or branched alkyl or alkenyl group having 6 to 30 carbon atoms in the molecule. Ashless friction modifiers such as metal salts, aliphatic alcohols, aliphatic ethers and aliphatic urea compounds can be preferably used.

As the aliphatic amine compound, a linear or branched, preferably linear aliphatic monoamine having 6 to 30 carbon atoms; a linear or branched, preferably linear aliphatic polyamine having 6 to 30 carbon atoms; and Examples thereof include alkylene oxide adducts of these aliphatic amines.

Examples of the aliphatic imide compound include a succinimide having a linear or branched alkyl or alkenyl group having 6 to 30 carbon atoms; and a modified product thereof with carboxylic acid, boric acid, phosphoric acid, sulfuric acid or the like. To be

Examples of the fatty acid ester include esters of linear or branched, preferably linear, fatty acids having 6 to 30 carbon atoms with an aliphatic monohydric alcohol or an aliphatic polyhydric alcohol.

Examples of fatty acid amides include amides of straight or branched chain, preferably straight chain fatty acids having 6 to 30 carbon atoms with aliphatic monoamines or aliphatic polyamines or ammonia.

Examples of the fatty acid hydrazide include a condensation product of a linear or branched, preferably linear, fatty acid having 6 to 30 carbon atoms and an unsubstituted or aliphatic substituted hydrazine.

Examples of the fatty acid metal salt include straight-chain or branched-chain, preferably straight-chain fatty acid having 6 to 30 carbon atoms, such as alkaline earth metal salts (magnesium salt, calcium salt, etc.) and zinc salt.

When the lubricating oil composition contains the component (I), the content thereof is preferably 0.01 to 2% by mass, more preferably 0.1% by mass or more, further preferably 0.1% by mass or more, based on the total amount of the lubricating oil composition. It is preferably 0.3% by mass or more, more preferably 1.0% by mass or less, and further preferably 0.8% by mass or less. When the content of the component (I) is at least the above lower limit value, it becomes possible to enhance the anti-shudder property. When the content of the component (I) is not more than the above upper limit value, it becomes possible to further increase the coefficient of friction between metals.

<Other additives>
In one embodiment, the lubricating oil composition is an antiwear agent or extreme pressure agent other than the component (H), an antioxidant, a pour point depressant other than the component (D), and a corrosion inhibitor other than the component (E). , A rust preventive, a metal deactivator other than the component (E), an antifoaming agent, a demulsifier, and a colorant may be further included.

Examples of the antiwear agent or extreme pressure agent other than the component (H) include sulfur compounds such as disulfides, sulfurized olefins, sulfurized fats and oils. When the lubricating oil composition contains an antiwear agent or an extreme pressure agent other than the component (H), the content is usually 0.01 to 5 mass% based on the total amount of the lubricating oil composition.

Examples of the antioxidant include ashless antioxidants such as phenol and amine, and metal antioxidants such as copper and molybdenum. Specifically, for example, phenol-based ashless antioxidants include 4,4′-methylenebis(2,6-di-tert-butylphenol) and 4,4′-bis(2,6-di-tert-butylphenol). ) And the like, and examples of the amine-based ashless antioxidant include phenyl-α-naphthylamine, alkylphenyl-α-naphthylamine, and dialkyldiphenylamine. When the lubricating oil composition contains an antioxidant, the content thereof is usually 0.01 to 5 mass% based on the total amount of the lubricating oil composition.

As the pour point depressant other than the component (D), a known pour point depressant such as a polymethacrylate polymer can be used depending on the properties of the lubricating base oil used. When the lubricating oil composition contains a pour point depressant, the content thereof is usually 0.05 to 1 mass% based on the total amount of the lubricating oil composition.

As the corrosion inhibitor other than the component (E), for example, known corrosion inhibitors such as benzotriazole-based, tolyltriazole-based, and imidazole-based compounds can be used. When the lubricating oil composition contains a corrosion inhibitor other than the component (E), its content is usually 0.005 to 5 mass% based on the total amount of the lubricating oil composition.

As the rust preventive, known rust preventives such as petroleum sulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenyl succinic acid ester, and polyhydric alcohol ester can be used. When the lubricating oil composition contains a rust preventive agent, the content thereof is usually 0.005 to 5 mass% based on the total amount of the lubricating oil composition.

Examples of the metal deactivator other than the component (E) include imidazoline, pyrimidine derivatives, mercaptobenzothiazole, benzotriazole and its derivatives, 2-(alkyldithio)benzimidazole, and β-(o-carboxybenzylthio). A known metal deactivator such as propionnitrile can be used. When the lubricating oil composition contains a metal deactivator other than the component (E), its content is usually 0.005 to 5 mass% based on the total amount of the lubricating oil composition.

As the defoaming agent, for example, known defoaming agents such as silicone, fluorosilicone, and fluoroalkyl ether can be used. When the lubricating oil composition contains an antifoaming agent, the content thereof is usually 0.0005 to 0.01% by mass based on the total amount of the lubricating oil composition.

As the demulsifier, for example, a known demulsifier such as a polyalkylene glycol-based nonionic surfactant can be used. When the lubricating oil composition contains a demulsifier, the content thereof is usually 0.005 to 5 mass% based on the total amount of the lubricating oil composition.

As the colorant, a known colorant such as an azo compound can be used.

<Lubricant composition>
The kinematic viscosity of the lubricating oil composition at 40° C. is 25 mm ² /s or less. Further, it is preferably 10 mm ² /s or more, more preferably 12 mm ² /s or more, further preferably 15 mm ² /s or more. When the kinematic viscosity of the lubricating oil composition at 40° C. is 25 mm ² /s or less, it becomes possible to improve fuel economy. Further, when the kinematic viscosity of the lubricating oil composition at 40° C. is equal to or higher than the above lower limit value, it becomes easy to sufficiently form an oil film at the lubricated portion and enhance wear resistance.

The kinematic viscosity of the lubricating oil composition at 100° C. is preferably 5.0 mm ² /s or more. Further, it is preferably 9.0 mm ² /s or less, more preferably 8.0 mm ² /s or less, and further preferably 7.0 mm ² /s or less. When the kinematic viscosity of the lubricating oil composition at 100° C. is equal to or higher than the above lower limit value, it is easy to sufficiently form an oil film at a lubricated portion and enhance wear resistance. Further, when the kinematic viscosity of the lubricating oil composition at 100° C. is not more than the above upper limit value, it becomes easy to improve fuel economy.

The viscosity index of the lubricating oil composition is preferably 170 or more. The upper limit of the viscosity index of the lubricating oil composition is not particularly limited, but is usually 300 or less. When the viscosity index of the lubricating oil composition is 170 or more, it becomes easy to improve fuel economy.

The Brookfield viscosity at -40°C (hereinafter sometimes referred to as "BF viscosity") of the lubricating oil composition is preferably 8,000 mPa·s or less, and more preferably 7,000 mPa·s or less. When the BF viscosity of the lubricating oil composition at −40° C. is 8,000 mPa·s or less, low temperature startability can be enhanced.

(Use)
The lubricating oil composition of the present invention can be preferably used as a continuously variable transmission oil for automobiles and the like, and can be particularly preferably used for lubrication of a metal belt type continuously variable transmission that transmits torque through a metal belt. ..

Hereinafter, the present invention will be described more specifically based on Examples and Comparative Examples. However, the present invention is not limited to these examples.

<Examples 1 to 19 and Comparative Examples 1 to 7>
As shown in Tables 1 to 3, lubricating oil compositions of the present invention (Examples 1 to 19) and comparative lubricating oil compositions (Comparative Examples 1 to 7) were prepared. In the table, the content of the base oil is based on the total amount of the base oil, and the content of each additive is based on the total amount of the composition. The details of the components are as follows.

((A) Lubricating base oil)
A1-1: Wax isomerized base oil (kinematic viscosity (40° C.): 9.072 mm ² /s, kinematic viscosity (100° C.): 2.621 mm ² /s, viscosity index: 127, sulfur content: less than 10 mass ppm , %C _P : 91.8, %C _N : 8.2, %C _A :0)
A1-2: Wax isomerized base oil (kinematic viscosity (40° C.): 9.617 mm ² /s, kinematic viscosity (100° C.): 2.653 mm ² /s, viscosity index: 112, sulfur content: less than 10 mass ppm _{,% C P: 92.5,%} C N: 7.3,% C A: 0.1)
A2-1: Wax isomerized base oil (kinematic viscosity (40° C.): 15.65 mm ² /s, kinematic viscosity (100° C.): 3.883 mm ² /s, viscosity index: 142, sulfur content: less than 10 mass ppm , %C _P : 92.5, %C _N : 7.5, %C _A :0)
A2-2: Wax isomerized base oil (kinematic viscosity (40° C.): 18.24 mm ² /s, kinematic viscosity (100° C.): 4.119 mm ² /s, viscosity index: 130, sulfur content: less than 10 mass ppm _{,% C P: 89.1,%} C N: 10.9,% C A: 0)

((B) boric acid ester compound)
B-1: borate mono _{(C 6-8} alkyl) esters, B: 2.83 wt%

((C) phosphoric acid)
C-1: phosphoric acid, P: 36 mass%

((D) poly(meth)acrylate)
D-1: Non-dispersion type polymethacrylate, weight average molecular weight: 20,000
D-2: Non-dispersion type polymethacrylate, weight average molecular weight: 50,000
D-3: Dispersion type polymethacrylate, weight average molecular weight: 40,000
D-4: Dispersion type polymethacrylate, weight average molecular weight: 150,000

((E) thiadiazole compound)
E-1: a thiadiazole compound having a hydrocarbyldithio group represented by any one of formulas (2) to (4), S: 36% by mass

((F) Metallic detergent)
F-1: Ca sulfonate, Ca: 18.4 mass%
F-2: Ca salicylate, Ca: 8.1 mass%

((G) Ashless dispersant)
G-1: succinimide, N: 2.1 mass%
G-2: Boron-containing succinimide, N: 2.3 mass%, B: 2.0 mass%

((H) Phosphorus antiwear agent)
H-1: di(n-butyl) phosphite, P: 15.5 mass%
H-2: diphenyl hydrogen phosphite, P: 13.2 mass%

((I) Friction modifier)
I-1: oleyl amine I-2: oleyl I-3: condensation product of a fatty acid with a fatty Zokua Min

((J) Other additives)
J-1: Rubber swelling agent J-2: Amine antioxidant J-3: Dimethyl silicone defoaming agent, kinematic viscosity (25° C.): 60,000 mm ² /s

(Low temperature viscosity characteristics)
The viscosity (BF viscosity) at an oil temperature of −40° C. was measured using a Brookfield viscometer for each of the lubricating oil compositions. The results are shown in Tables 1-3. When the BF viscosity at −40° C. is 8,000 mPa·s or less, it can be judged that the low temperature viscosity characteristic is good.

(Shear stability test)
For each of the lubricating oil compositions, the shear stability of the gear oil composition was evaluated by a shear stability test according to JPI-5S-29-88. The sample oil is irradiated with ultrasonic waves with a frequency of 10 kHz and a vibration range of 28 μm from the vibrator for 1 hour, and the kinematic viscosity of the sample oil after ultrasonic irradiation at 100° C. is 100° C. of the sample oil before ultrasonic irradiation. The reduction rate (%) with respect to the kinematic viscosity was calculated. The results are shown in Tables 1-3. If the kinematic viscosity reduction rate in this test is 2.5 or less, it can be judged that the shear stability is good.

(EHL test)
For each of the lubricating oil compositions, the oil film thickness in the elastohydrodynamic lubrication state was measured by an optical interference method using an EHL tester (EHD2 oil film thickness measuring instrument manufactured by PCS). The measurement conditions are as follows.
Steel ball: PCS Standard Ball (material: SUJ-2), diameter 19.05 mm
Disc: A glass disc having a glass substrate, a chromium layer coated on the surface of the glass substrate, and a silica layer coated on the surface of the chromium layer Oil temperature: 80° C.
Load: 20N
Average Hertz pressure: 0.5 GPa
Peripheral speed: 1m/s
Sliding rate: 10%
The results are shown in Tables 1-3. If the oil film thickness measured in this test is 55 nm or less, it can be determined that the oil film thickness is sufficiently thin.

(High-speed four-ball test)
With respect to each of the lubricating oil compositions, the load bearing capacity and the wear resistance of the lubricating oil composition were evaluated by a high-speed four-ball test based on JPI-5S-40-93.
(1) The final non-seizure load (LNSL) was measured at a rotation speed of 1800 rpm.
(2) The wear scar diameter was measured after operating at a rotation speed of 1200 rpm, a load of 392 N, and an oil temperature of 80° C. for 30 minutes.
The results are shown in Tables 1-3. In this test, if LNSL is 618 N or more, it can be judged that the load bearing capacity (seizure resistance) is good. If the wear scar diameter is 0.70 mm or less, it can be determined that the wear resistance is good.

(FALEX seizure test)
The load bearing capacity of each of the lubricating oil compositions was evaluated by a FALEX seizure test according to ASTM D3233. Under the condition of oil temperature of 110° C., a steel pin sandwiched between two stationary steel V blocks was rotated at 290 rpm, and the load at which seizure occurred was measured. The results are shown in Tables 1-3. If the load causing seizure in this test is 3900 N or more, it can be judged that the load resistance (seizure resistance) is good.

(Uni-steel test)
For each of the lubricating oil compositions, a unit steel rolling fatigue tester (triple type high temperature rolling fatigue tester (TRF-1000/3-01H), manufactured by Tokyo Testing Machine Co., Ltd.) was used to test the unit steel (British Petroleum Institute of Japan). Method: The rolling bearing fatigue life of the thrust bearing was measured by IP305/79). Regarding a test bearing in which a bearing ring on one side of a thrust needle bearing (NSK FNTA-2542C) is replaced with a flat test piece (material: SUJ2), a load of 7,000 N, a surface pressure of 2 GPa, a rotation speed of 1450 rpm, and an oil temperature of 120° C. Underneath, the time until either the roller or the specimen was fatigue damaged was measured. When the vibration acceleration of the test portion measured by the vibration accelerometer provided in the Uni-steel rolling fatigue testing machine reached 1.5 m/s ² , it was determined that fatigue damage had occurred. Fatigue life was calculated as 50% life (L50: time at which cumulative probability becomes 50%) by Weibull plot from the time until fatigue damage in 10 repeated tests. The results are shown in Tables 1-3. If the 50% life measured in this test is 1200 minutes or more, it can be judged that the fatigue life is good.

(LFW-1 test)
For each of the lubricating oil compositions, according to JASO M358-2005 (belt type CVT oil intermetallic friction coefficient characteristic test, high load method), using a block on ring friction wear tester (LFW-1), intermetallic friction The coefficient (dynamic friction coefficient) was measured. The test conditions were a block: H60, a ring: S10, a load of 1112 N, a sliding speed of 0.5 m/s, and an oil temperature of 90°C. The results are shown in Tables 1-3. If the intermetallic friction coefficient measured in this test is 0.90 or more, it can be determined that the intermetallic friction coefficient is sufficiently high.

(Evaluation results)
The lubricating oil compositions of Examples 1 to 19 gave good results in low temperature viscosity characteristics, shear stability, oil film thickness, load bearing capacity (seizure resistance), wear resistance, fatigue life, and intermetallic friction coefficient. Indicated.
The lubricating oil composition of Comparative Example 1 in which the content of the component (B) was too small was inferior in wear resistance and seizure resistance.
The lubricating oil composition of Comparative Example 2 in which the content of the component (B) was excessive was inferior in seizure resistance and fatigue life.
The lubricating oil composition of Comparative Example 3 in which the content of the component (C) was too small was inferior in wear resistance and seizure resistance.
The lubricating oil composition of Comparative Example 4 in which the content of the component (C) was excessive was inferior in seizure resistance and fatigue life.
The lubricating oil composition of Comparative Example 5, which did not contain the components (B) and (C), was inferior in seizure resistance, wear resistance, fatigue life, and intermetallic friction coefficient.
The lubricating oil composition of Comparative Example 6 in which the contents of the component (B) and the component (C) were excessively large was inferior in fatigue life.
The lubricating oil composition of Comparative Example 7 containing the polymethacrylate outside the range of the component (D) instead of the component (D) was inferior in shear stability.

Claims (3)

(A) lubricant base oil,
(B) a boric acid ester compound, in terms of the total amount of the lubricating oil composition, as a boron amount of 25 mass ppm or more and 500 mass ppm or less,
(C) Phosphoric acid is 100 mass ppm or more and 750 mass ppm or less as a phosphorus amount on the basis of the total amount of the lubricating oil composition,
(D) a poly(meth)acrylate having a weight average molecular weight of 100,000 or less ,
(E) the thiadiazole compound is contained in an amount of 180 mass ppm or more and 900 mass ppm or less in terms of sulfur based on the total amount of the lubricating oil composition ,
Kinematic viscosity at 40 ° C. of the lubricating oil composition is 25 mm ² / s Ri der below,
The lubricating oil composition, which is the sum of the boron content B (unit: mass ppm) derived from the component (B) in the lubricating oil composition and the phosphorus content P (unit: mass ppm) in the lubricating oil composition. A lubricating oil composition for a continuously variable transmission , wherein the ratio (B+P)/S to the sulfur content S (unit: mass ppm) derived from the component (E) therein is 1 or more and 3 or less . The (A) lubricating base oil is
(A1) Base oil having a kinematic viscosity at 100° C. of 2.8 mm ² /s or less, a viscosity index of 110 or more, and a% _CP of 90 or more is contained in an amount of 30% by mass or more and 100% by mass or less based on the total amount of the lubricating base oil. And
(A2) API group III base oil or group IV base oil or mixed base oil thereof having a kinematic viscosity at 100° C. of 3 mm ² /s or more and 10 mm ² /s or less, 70% by mass or less based on the total amount of the lubricating base oil. With or without
The content of the base oil other than the base oils (A1) and (A2) is 0% by mass or more and 4% by mass or less based on the total amount of the lubricating base oil,
The kinematic viscosity of the lubricating base oil (A) at 100° C. is 3.4 mm ² /s or less,
The lubricating oil composition for a continuously variable transmission according to claim 1 . The lubricating oil composition for a continuously variable transmission according to claim 1 or 2 , wherein the component (B) is one or more borate ester compounds represented by the following general formula (1).
(In the general formula (1), R ¹ is a hydrocarbyl group having 1 to 30 carbon atoms, and R ² and R ³ are each independently a hydrogen atom or a hydrocarbyl group having 1 to 30 carbon atoms.)