JP7312717B2 - lubricating oil composition - Google Patents

Description

The present invention relates to lubricating oil compositions. More particularly, it relates to a lubricating oil composition that can be used in power trains such as automobile transmissions, particularly in continuously variable transmissions.

In powertrains used in electric vehicles, hybrid vehicles, and the like, if lubricating oil with poor anti-foaming properties is filled, there is a risk that the lubricating oil will leak out in the form of bubbles from the breather. Therefore, it is common practice to add an antifoaming agent to the lubricating oil to prevent foaming. As antifoaming agents, polysiloxane antifoaming agents (organopolysiloxanes, etc.) have been conventionally known. For example, Patent Document 1 describes a lubricating oil composition containing (a) polydimethylsiloxane having a kinematic viscosity at 25°C of 300,000 to 1,500,000 mm ² /s and (b) fluorinated polysiloxane having a kinematic viscosity at 25°C of 500 to 9,000 mm ² /s.

In addition, conventional transmissions were designed so that lubricating oil would not leak from the breather even if the defoaming properties of the transmission oil were lost. However, in recent years, there is a strong need for multi-speed transmissions and miniaturization for the purpose of improving fuel efficiency, and it has become difficult to prevent the leakage of lubricating oil from the breather structurally. Therefore, rather than developing an improved mechanical structure, it is desirable to develop a lubricant material that can maintain defoaming properties for a long period of time. For example, Patent Document 2 describes the use of a polymer compound microparticulated by a dispersion polymerization method as an antifoaming agent in order to maintain the antifoaming performance of the lubricating oil for a long period of time even in a lubricating environment where a high centrifugal action acts on the lubricating oil.

JP-A-2000-87065 JP 2017-39124 A

However, in general, lubricating oils used in powertrains often contain compounds containing phosphorus, sulfur, or the like as antiwear agents that impart wear resistance to sliding surfaces. These compounds change into acidic components as the lubricating oil deteriorates due to heat or oxidation. When this acidic component acts on the antifoaming agent, the structure of the antifoaming agent changes, and the antifoaming action may be lost in a short period of time.

In view of the above problems, it is an object of the present invention to provide a lubricating oil composition that exhibits sufficient antifoaming properties even when denatured by heat or oxidation while maintaining good wear resistance.

（式中、Ｒ^１はそれぞれ独立に、炭素数１～８の脂肪族炭化水素基である）
で表される第１の亜リン酸エステルと、
（Ｄ）下記式（２）：

（式中、Ｒ^２はそれぞれ独立に、炭素数６～１２の芳香族炭化水素基である）
で表される第２の亜リン酸エステルと、
（Ｅ）下記式（３）：

（式中、Ｒ^３はそれぞれ独立に、炭素数３～１８の脂肪族炭化水素基であり、Ｌ^３は炭素数２～５の脂肪族炭化水素鎖である）
で表されるジチオリン酸エステル誘導体と、
（Ｆ）シリコーン系消泡剤と、
を含み、
前記（Ｂ）リン酸塩、前記（Ｃ）第１の亜リン酸塩、前記（Ｄ）第２の亜リン酸塩、および（Ｅ）ジチオリン酸エステル誘導体に由来するリン含有量が、前記組成物の総質量に対して、それぞれ、２５～３００質量ｐｐｍ、３～１５０質量ｐｐｍ、９０～４２０質量ｐｐｍ、および３～７５質量ｐｐｍであることを特徴とする、潤滑油組成物。
［２］ 前記（Ｆ）シリコーン系消泡剤の含有量が、前記組成物の総質量を基準として１０～１０００質量ｐｐｍである、［１］に記載の潤滑油組成物。
［３］ ２つのＲ^１が、いずれも直鎖アルキル基である、［１］または［２］に記載の潤滑油組成物。
［４］ ２つのＲ^２が、いずれも非置換フェニルまたはアルキル置換フェニルである、［１］～［３］のいずれかに記載の潤滑油組成物。
［５］ Ｌ^３が、エチレン基またはプロピレン基である、［１］～［４］のいずれかに記載の潤滑油組成物。
［６］ 増粘剤、無灰分散剤、清淨剤、摩擦調整剤、金属不活性化剤、酸化防止剤、消泡剤、防錆剤、流動点降下剤、および抗乳化剤からなる群から選択される添加剤をさらに含んでなる、［１］～［５］のいずれかに記載の潤滑油組成物。
［７］ 自動変速機、またはハイブリッド自動車もしくは電気自動車のパワートレインに用いられる、［１］～［６］のいずれかに記載の潤滑油組成物。
［８］ 無段変速機用組成物である、［１］～［６］のいずれかに記載の潤滑油組成物。
［９］ ［１］～［８］のいずれかに記載の潤滑油組成物を用いて、自動変速機、またはハイブリッド自動車もしくは電気自動車のパワートレインを潤滑する方法。 According to the present invention, the following inventions are provided.
[1] A lubricating oil composition comprising
(A) a lubricating base oil;
(B) a phosphate;
(C) the following formula (1):

(Wherein, each R ¹ is independently an aliphatic hydrocarbon group having 1 to 8 carbon atoms)
A first phosphite ester represented by
(D) the following formula (2):

(Wherein, each R ² is independently an aromatic hydrocarbon group having 6 to 12 carbon atoms)
A second phosphite ester represented by
(E) the following formula (3):

(In the formula, each R ³ is independently an aliphatic hydrocarbon group having 3 to 18 carbon atoms, and L ³ is an aliphatic hydrocarbon chain having 2 to 5 carbon atoms.)
A dithiophosphate derivative represented by
(F) a silicone antifoaming agent;
including
The phosphorus content derived from the (B) phosphate, the (C) first phosphite, the (D) second phosphite, and (E) the dithiophosphate derivative is 25 to 300 ppm by weight, 3 to 150 ppm by weight, 90 to 420 ppm by weight, and 3 to 75 ppm by weight, respectively, based on the total weight of the composition. A lubricating oil composition.
[2] The lubricating oil composition according to [1], wherein the content of (F) the silicone antifoaming agent is 10 to 1000 ppm by mass based on the total mass of the composition.
[3] The lubricating oil composition according to [1] or [2], wherein both of the two R ¹ 's are linear alkyl groups.
[4] The lubricating oil composition according to any one of [1] to [3], wherein both R ² are unsubstituted phenyl or alkyl-substituted phenyl.
[5] The lubricating oil composition according to any one of [1] to [4], wherein ^L3 is an ethylene group or a propylene group.
[6] The lubricating oil composition according to any one of [1] to [5], further comprising an additive selected from the group consisting of thickeners, ashless dispersants, clarifying agents, friction modifiers, metal deactivators, antioxidants, defoaming agents, rust inhibitors, pour point depressants, and demulsifiers.
[7] The lubricating oil composition according to any one of [1] to [6], which is used in automatic transmissions or powertrains of hybrid or electric vehicles.
[8] The lubricating oil composition according to any one of [1] to [6], which is a composition for a continuously variable transmission.
[9] A method of lubricating an automatic transmission or a powertrain of a hybrid or electric vehicle using the lubricating oil composition according to any one of [1] to [8].

ADVANTAGE OF THE INVENTION According to this invention, the lubricating oil composition which can demonstrate sufficient antifoaming property, even if it modifies|denatures by heat or oxidation, is provided, maintaining wear resistance favorably.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail. In this specification, unless otherwise specified, the content of each element of calcium, magnesium, zinc, phosphorus, sulfur, boron, barium, and molybdenum in oil shall be measured by inductively coupled plasma atomic emission spectrometry (intensity ratio method) in accordance with JPI-5S-38-2003. Also, the nitrogen element content in the oil shall be measured by a chemiluminescence method in accordance with JIS K2609.

[Lubricating oil composition]
A lubricating oil composition according to the present invention comprises a lubricating base oil, two specific phosphites, a specific dithiophosphate derivative, and a silicone antifoaming agent. In addition, other additives may be included. The lubricating oil composition according to the present invention can be suitably used as an automatic transmission oil or a lubricating oil for a power train of a hybrid vehicle or an electric vehicle, particularly a transmission oil for a power train. Each component constituting the lubricating oil composition according to the present invention will be described in detail below.

[(A) Lubricating base oil]
The lubricating base oil is not particularly limited, for example, a lubricating oil fraction obtained by atmospheric distillation and / or vacuum distillation of crude oil, solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, paraffinic base oil refined by a combination of two or more selected from refining treatments such as clay treatment, normal paraffinic base oil, isoparaffinic base oil, and mixtures thereof.

Preferred examples of the lubricating base oil include base oils obtained by using the following base oils (1) to (8) as a raw material, refining this raw material oil and/or a lubricating oil fraction recovered from this raw material oil by a predetermined refining method, and recovering the lubricating oil fraction.
(1) Distillate oil obtained by atmospheric distillation of paraffinic crude oil and/or mixed crude oil (2) Distillate oil obtained by vacuum distillation of atmospheric distillation residue oil of paraffinic crude oil and/or mixed crude oil (WVGO)
(3) Waxes (such as slack waxes) obtained by lubricating oil dewaxing processes and/or synthetic waxes (such as Fischer-Tropsch waxes and GTL waxes) obtained by gas-to-liquid (GTL) processes, etc.
(4) One or more mixed oil selected from base oils (1) to (3) and/or mild hydrocracked oil of the mixed oil (5) Mixed oil of two or more selected from base oils (1) to (4) (6) Deasphalted oil (DAO) of base oil (1), (2), (3), (4) or (5)
(7) Mild hydrocracking treated oil (MHC) of base oil (6)
(8) A mixed oil of two or more types selected from base oils (1) to (7).

As the above-mentioned predetermined purification method, hydrorefining such as hydrocracking and hydrofinishing; solvent refining such as furfural solvent extraction; dewaxing such as solvent dewaxing and catalytic dewaxing; clay refining using acid clay, activated clay, etc.; In the present invention, one of these purification methods may be used alone, or two or more of them may be used in combination. When combining two or more purification methods, the order is not particularly limited and can be selected as appropriate.

Furthermore, as the lubricating base oil, the following base oil (9) or (10) obtained by performing a predetermined treatment on a base oil selected from the base oils (1) to (8) or a lubricating oil fraction recovered from the base oil is particularly preferable.
(9) Hydrocracking the base oil selected from the base oils (1) to (8) or the lubricating oil fraction recovered from the base oil, and subjecting the product or the lubricating oil fraction recovered from the product by distillation or the like to dewaxing such as solvent dewaxing or catalytic dewaxing, or hydrocracking base oil obtained by distillation after the dewaxing treatment (10) The base oil selected from the above base oils (1) to (8) or the lubricating oil fraction recovered from the base oil is hydrogenated A hydroisomerized base oil obtained by performing dewaxing treatment such as solvent dewaxing or catalytic dewaxing on the product or a lubricating oil fraction recovered from the product by distillation or the like, or by distilling after the dewaxing treatment. As the dewaxing step, a base oil produced through a catalytic dewaxing step is preferred.

In obtaining the lubricating base oil of (9) or (10) above, a solvent refining treatment and/or a hydrofinishing treatment step may be further carried out at an appropriate stage, if necessary.

The catalyst used for hydrocracking and hydroisomerization is not particularly limited, but a composite oxide having cracking activity (e.g., silica-alumina, alumina boria, silica-zirconia, etc.) or a combination of one or more types of such composite oxides and bound with a binder is used as a carrier, and a hydrocracking catalyst or zeolite (e.g., ZSM-5, zeolite beta) carrying a metal having hydrogenation ability (e.g., one or more metals of Group VIa or Group VIII of the periodic table) is supported. , SAPO-11, etc.) on which a hydrogenation-capable metal containing at least one group VIII metal is preferably used. The hydrocracking catalyst and hydroisomerization catalyst may be used in combination, such as by layering or mixing.

The reaction conditions for hydrocracking/hydroisomerization are not particularly limited, but hydrogen partial pressure of 0.1 to 20 MPa, average reaction temperature of 150 to 450° C., LHSV of 0.1 to 3.0 hr ⁻¹ , and hydrogen/oil ratio of 50 to 20,000 scf/b are preferred.

The kinematic viscosity at 100° C. of the lubricating base oil is preferably 1.7 to 8.0 mm ² /s, more preferably 2.2 to 7.0 mm ² /s, still more preferably 2.5 to 6.0 mm ² /s. If the kinematic viscosity at 100° C. of the lubricating base oil is within the above numerical range, sufficient fuel efficiency can be obtained, and the oil film formation at the lubricating portion is well performed, resulting in excellent lubricity. As used herein, the term "kinematic viscosity at 100°C" means the kinematic viscosity at 100°C measured according to JIS K 2283-2010.

The kinematic viscosity of the lubricating base oil at 40° C. is preferably 5.0 to 40 mm ² /s, more preferably 7.0 to 35 mm ² /s, still more preferably 10 to 30 mm ² /s. If the kinematic viscosity at 40° C. of the lubricating base oil is within the above numerical range, sufficient fuel efficiency can be obtained, and an oil film can be well formed at the lubrication points, resulting in excellent lubricity. As used herein, "kinematic viscosity at 40°C" means kinematic viscosity at 40°C measured according to JIS K 2283-2010.

The viscosity index of the lubricating base oil is preferably 100 or higher, more preferably 110 or higher, and may be 120 or higher. If the viscosity index is within the above numerical range, the viscosity-temperature characteristics of the lubricating oil composition, thermal and oxidation stability, and volatilization prevention properties are improved, the friction coefficient is reduced, and the wear resistance is further improved. As used herein, the term "viscosity index" means a viscosity index measured according to JIS K 2283-2010.

The density (ρ ₁₅ ) of the lubricating base oil at 15°C is preferably 0.860 or less, more preferably 0.850 or less, still more preferably 0.840 or less. As used herein, the term "density" at 15°C means the density at 15°C measured according to JIS K 2249-1995.

The pour point of the lubricating base oil is preferably -10°C or lower, more preferably -12.5°C or lower, and still more preferably -15°C or lower. If the pour point is within the above numerical range, the low-temperature fluidity of the entire lubricating oil composition can be improved. As used herein, the term "pour point" means the pour point measured according to JIS K 2269-1987.

The sulfur content in the lubricating base oil depends on the sulfur content of the raw material. For example, when a raw material containing substantially no sulfur such as a synthetic wax component obtained by a Fischer-Tropsch reaction or the like is used, a lubricating base oil substantially containing no sulfur can be obtained. In addition, when using a sulfur-containing raw material such as slack wax obtained in the refining process of lubricating base oil or microwax obtained in the waxing process, the sulfur content in the obtained lubricating base oil is usually 100 ppm by mass or more. In the lubricating base oil, the sulfur content is preferably 100 mass ppm or less, more preferably 50 mass ppm or less, and still more preferably 10 mass ppm or less from the viewpoint of improving thermal and oxidation stability and reducing sulfur. In the present specification, "sulfur content in lubricating base oil" (hereinafter sometimes simply referred to as sulfur content) means sulfur content measured according to JIS K 2541-2003.

The saturated content in the lubricating base oil is preferably 90% by mass or more, preferably 95% by mass or more, more preferably 99% by mass or more, based on the total amount of the lubricating base oil. When the content of the saturated component satisfies the above conditions, viscosity-temperature characteristics and thermal/oxidation stability can be improved, and when an additive is blended in the lubricating base oil, the additive can be sufficiently stably dissolved and retained in the lubricating base oil, and the function of the additive can be expressed at a higher level. Furthermore, the frictional properties of the lubricating base oil itself can be improved, and as a result, an improvement in the friction reduction effect and, in turn, an improvement in fuel efficiency can be achieved. As used herein, the content of saturates means a value measured according to ASTM D 2007-93.

The ratio of cyclic saturated content to the saturated content in the lubricating base oil may be 0% by mass, but is preferably 0.5% by mass or more. In addition, the ratio of the cyclic saturated portion to the saturated portion is preferably 40% by mass or less, preferably 35% by mass or less, preferably 30% by mass or less, more preferably 25% by mass or less, and still more preferably 21% by mass or less. By satisfying the above conditions, the viscosity-temperature characteristics and heat/oxidation stability can be improved, and when an additive is added to the lubricating base oil, the additive can be sufficiently stably dissolved and retained in the lubricating base oil, and the function of the additive can be expressed at a higher level. In addition, in this specification, the content of the cyclic saturated content in the saturated content in the lubricating base oil means the value measured based on the following conditions.
[Test condition]
Test equipment: JEOL JMS-MS700V
Sample introduction method: Glass reservoir Resolution: 500
Test method: ASTM D2786-91 compliant However, instead of ASTM D2786-91 Chapter 8, perform calibration to meet the following conditions and determine measurement conditions.
Σ67/Σ71 = 0.20 to 0.22
Σ69/Σ71=0.14 to 0.16
H127/H226=0.80-0.85
(Here, Σ67, Σ69, and Σ71 are defined according to ASTM D2786, and H127 and H226 mean the respective peak intensities at m/z = 127 and 226)
The amount of ion introduced into the ion source is set to such an extent that the peak at m/z=57, which has the highest intensity among the detected peaks of n-hexadecane, is not saturated.

It should be noted that, if there are circumstances that make it impossible to carry out the measurement using the above-described apparatus and/or sample introduction method, a similar apparatus can be used as long as similar results are obtained and it complies with ASTM E137. In addition, the test conditions at that time shall comply with the content described in the preceding paragraph.

The aromatic content in the lubricating base oil is preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 4% by mass or less, still more preferably 3% by mass or less, most preferably 2% by mass or less, and may be 0% by mass, based on the total amount of the lubricating base oil. If the content of the aromatic component is within the above numerical range, the viscosity-temperature characteristics, heat/oxidation stability and friction characteristics, as well as the anti-volatility and low-temperature viscosity characteristics will be good.

The term "aromatic content" as used herein means a value measured according to ASTM D 2007-93. Aromatic components generally include alkylbenzene, alkylnaphthalene, anthracene, phenanthrene and alkylated products thereof, compounds in which four or more benzene rings are condensed, pyridines, quinolines, phenols, naphthols and other heteroatom-containing aromatic compounds.

As the lubricating base oil, a group II base oil, a group III base oil, a group IV base oil, or a group V base oil of the API base oil classification, or a mixed base oil thereof can be preferably used. API Group II base oils are mineral base oils having a sulfur content of 0.03 mass % or less, a saturate content of 90 mass % or more, and a viscosity index of 80 or more and less than 120. API Group III base oils are mineral base oils having a sulfur content of 0.03 wt.% or less, a saturates content of 90 wt.% or more, and a viscosity index of 120 or more. API Group IV base oils are poly-alpha-olefin base oils. API Group V base oils are base oils that do not belong to any of Groups I to IV, and examples thereof include ester-based base oils.

A synthetic base oil may be used as the lubricating base oil. Synthetic base oils include poly α-olefins and their hydrides, isobutene oligomers and their hydrides, isoparaffins, alkylbenzenes, alkylnaphthalenes, monoesters (butyl stearate, octyl laurate, 2-ethylhexyl oleate, etc.), diesters (ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate, etc.), polyol esters. (trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol 2-ethylhexanoate, pentaerythritol pelargonate, etc.), polyoxyalkylene glycols, dialkyldiphenyl ethers, polyphenyl ethers, and mixtures thereof. Among them, poly-α-olefins are preferred. Polyα-olefins typically include oligomers or co-oligomers of α-olefins having 2 to 32 carbon atoms, preferably 6 to 16 carbon atoms (1-octene oligomer, decene oligomer, ethylene-propylene co-oligomer, etc.) and their hydrogenation products.

The method for producing poly-α-olefin is not particularly limited, but examples include a method of polymerizing α-olefin in the presence of a polymerization catalyst such as a catalyst containing a complex of aluminum trichloride or boron trifluoride with water, alcohol (ethanol, propanol, butanol, etc.), carboxylic acid or ester.

The lubricating base oil may consist of a single base oil component or may contain a plurality of base oil components as the entire lubricating base oil.

The content of the lubricating base oil in the lubricating oil composition is usually 70% by mass or more, preferably 75% by mass or more, more preferably 80% by mass or more, and usually 98% by mass or less, based on the total mass of the lubricating oil composition.

[(B) phosphoric acid]
A lubricating oil composition according to the present invention comprises a phosphate. Phosphate usually means a reaction product of phosphoric acid and a metal or a basic compound, but in the present invention, phosphoric acid itself is also included in phosphate for convenience. Therefore, the phosphoric acid added to the composition during preparation may react with other components in the composition to form a salt, and the phosphate added to the composition during preparation may dissociate in the composition to form phosphoric acid. Examples of metals capable of forming salts by reacting with phosphoric acid include alkali metals such as lithium, sodium and potassium, and alkaline earth metals such as calcium and magnesium. Examples of basic compounds include organic compounds having an amino group or an imide group, and inorganic compounds such as metal hydroxides.

In the present invention, the content of phosphate in the lubricating oil composition is based on phosphorus contained in the phosphate. Specifically, based on the total mass of the lubricating oil composition, the phosphorus content derived from the phosphate is 25 mass ppm or more, preferably 30 mass ppm or more, and particularly preferably 50 mass ppm or more. Moreover, it is 300 mass ppm or less, preferably 270 mass ppm or less, and particularly preferably 250 mass ppm or less. When the phosphorus content derived from the phosphate is equal to or higher than the lower limit value, wear resistance is improved, and when the phosphorus content derived from the phosphate is equal to or lower than the upper limit value, it becomes possible to suppress the deterioration of defoaming properties after thermal/oxidative deterioration.

（式中、Ｒ^１はそれぞれ独立に、炭素数１～８の脂肪族炭化水素基である） [(C) First phosphite ester]
A lubricating oil composition according to the present invention comprises two specific phosphites. One of them, the first phosphite, is represented by the following general formula (1).

(Wherein, each R ¹ is independently an aliphatic hydrocarbon group having 1 to 8 carbon atoms)

Although the phosphite compound represented by general formula (1) usually has tautomerism, any tautomer of the compound represented by general formula (1) is considered to be the component (C) in this specification.

R ¹ may be a linear aliphatic hydrocarbon group or a branched aliphatic hydrocarbon group. Here, the two R ¹ 's may be the same or different, but are preferably the same from the viewpoint of cost. In addition, each aliphatic hydrocarbon group preferably has 2 to 10 carbon atoms, more preferably 3 to 8 carbon atoms. Specific examples include ethyl group, n-propyl group, n-butyl group, i-butyl group, n-pentyl group, n-hexyl group and the like. The aliphatic group may also contain unsaturated bonds, but preferably does not contain unsaturated bonds, as the unsaturated bonds may react with other components to modify the lubricating oil composition.

式中、
ｉ－Ｂｕ： ｉ－ブチル基
ｎ－Ｂｕ： ｎ－ブチル基
ｉ－Ｐｒ： ｉ－プロピル基
Ｅｔ： エチル基
ｎ－Ｈｅｘ： ｎ－ヘキシル基
である。 Specific examples of such a first phosphite include the following.

During the ceremony,
i-Bu: i-butyl group n-Bu: n-butyl group i-Pr: i-propyl group Et: ethyl group n-Hex: n-hexyl group.

The lubricating oil composition according to the present invention may contain two or more kinds of the first phosphite represented by the general formula (1).

In the present invention, the content of the first phosphite in the lubricating oil composition is based on phosphorus contained in the first phosphite. Specifically, based on the total mass of the lubricating oil composition, the phosphorus content derived from the first phosphite is 3 mass ppm or more, preferably 10 mass ppm or more, and particularly preferably 20 mass ppm or more. Moreover, it is 150 mass ppm or less, preferably 130 mass ppm or less, and particularly preferably 100 mass ppm or less. When the phosphorus content derived from the first phosphite is equal to or higher than the lower limit, wear resistance is improved, and when the phosphorus content derived from the first phosphite is equal to or lower than the upper limit, deterioration of defoaming properties after thermal/oxidative deterioration can be suppressed.

（式中、Ｒ^２はそれぞれ独立に、炭素数６～１２の芳香族炭化水素基である） [(D) Second phosphite]
The lubricating oil composition according to the invention further comprises a second phosphite. This second phosphite is represented by the following general formula (2).

(Wherein, each R ² is independently an aromatic hydrocarbon group having 6 to 12 carbon atoms)

Although the phosphite ester compound represented by the general formula (2) usually has tautomerism, any tautomer of the compound represented by the general formula (2) corresponds to the component (D) in this specification.

^R2 is an aromatic hydrocarbon group containing at least one aromatic ring. The aromatic rings are benzene rings or naphthalene rings, and they may be substituted with aliphatic hydrocarbon groups. Specific examples include a phenyl group, a naphthyl group, a methylphenyl group, an ethylphenyl group, a benzyl group and the like. Here, the two ^R2 's may be the same or different, but are preferably the same from the viewpoint of cost. In addition, each aromatic hydrocarbon group preferably has 6 to 10 carbon atoms, more preferably 6 to 8 carbon atoms.

式中、Ｍｅはメチル基である。 Specific examples of such second phosphites include the following.

In the formula, Me is a methyl group.

The lubricating oil composition according to the present invention may contain two or more second phosphites represented by the general formula (2).

In the present invention, the content of the second phosphite in the lubricating oil composition is based on phosphorus contained in the second phosphite. Specifically, based on the total mass of the lubricating oil composition, the phosphorus content derived from the second phosphite ester is 90 mass ppm or more, preferably 100 mass ppm or more, and particularly preferably 200 mass ppm or more. Moreover, it is 420 mass ppm or less, preferably 400 mass ppm or less, and particularly preferably 300 mass ppm or less. When the phosphorus content derived from the second phosphite is equal to or higher than the lower limit, wear resistance is improved, and when the phosphorus content derived from the second phosphite is equal to or lower than the upper limit, deterioration of antifoaming properties after thermal/oxidative deterioration can be suppressed.

The lubricating oil composition according to the present invention may contain two or more types of phosphorus-containing compounds represented by general formula (2).

（式中、Ｒ^３はそれぞれ独立に、炭素数３～１８の脂肪族炭化水素基であり、Ｌ^３は炭素数２～５の脂肪族炭化水素鎖である） [(E) dithiophosphate derivative]
Lubricating oil compositions according to the present invention comprise certain dithiophosphate derivatives. This dithiophosphate derivative is represented by the following general formula (3).

(In the formula, each R ³ is independently an aliphatic hydrocarbon group having 3 to 18 carbon atoms, and L ³ is an aliphatic hydrocarbon chain having 2 to 5 carbon atoms.)

R ³ may be a linear aliphatic hydrocarbon group or a branched aliphatic hydrocarbon group. Here, the two R ¹ 's may be the same or different, but are preferably the same from the viewpoint of cost. In addition, each aliphatic hydrocarbon group preferably has 3 to 10 carbon atoms, more preferably 3 to 8 carbon atoms. Specific examples include n-propyl group, i-propyl group, n-butyl group, i-butyl group, t-butyl group, n-pentyl group, n-hexyl group, 3-heptyl group, octyl group, 2-ethylhexyl group and the like, and i-propyl group, i-butyl group and 2-ethylhexyl group are preferred.

L ³ is an aliphatic hydrocarbon chain that may be linear or branched and preferably has no unsaturated bonds. Specific examples include -(CH ₂ ) ₂ -, -(CH ₂ ) ₃ -, -(CH ₂ ) ₄ -, -CH ₂ -CH(CH ₃ )-, -(CH ₂ ) ₂ -CH(CH ₃ )-, -CH ₂ -CH(CH ₂ CH ₃ )- and the like.

式中、
ｉ－Ｂｕ： ｉ－ブチル基
ｉ－Ｐｒ： ｉ－プロピル基
ｎ－Ｐｒ： ｎ－プロピル基
である。 Specific examples of such dithiophosphate derivatives include the following.

During the ceremony,
i-Bu: i-butyl group i-Pr: i-propyl group n-Pr: n-propyl group.

As such dithiophosphate derivatives, IRGALUBE353, IRGALUBE62, etc. (both trade names, manufactured by BASF) are commercially available and can be used.

The lubricating oil composition according to the present invention may contain two or more dithiophosphate derivatives represented by general formula (3).

In the present invention, the content of the dithiophosphate derivative in the lubricating oil composition is based on phosphorus contained in the dithiophosphate derivative. Specifically, based on the total mass of the lubricating oil composition, the phosphorus content derived from the dithiophosphate derivative is 3 mass ppm or more, preferably 5 mass ppm or more, and particularly preferably 7 mass ppm or more. Moreover, it is 75 mass ppm or less, preferably 60 mass ppm or less, and particularly preferably 30 mass ppm or less. When the phosphorus content derived from the dithiophosphate derivative is equal to or higher than the lower limit, wear resistance is improved, and when the phosphorus content derived from the dithiophosphate derivative is equal to or lower than the upper limit, deterioration of antifoaming properties after thermal/oxidative deterioration can be suppressed.

[(F) Silicone antifoaming agent]
A lubricating oil composition according to the present invention comprises a silicone antifoaming agent. A silicone antifoaming agent is a polymer in which a large number of siloxane units ( _--SiR.sub.2 --O--, where R is hydrogen, an alkyl group, etc.) are bonded. Specific examples include dimethylsilicone composed of dimethylsiloxane units, methylphenylsilicone composed of dimethylsiloxane units and diphenylsiloxane units, methylhydrogensilicone in which some of the methyl groups of dimethylsilicone are substituted with hydrogen, and fluorosilicone in which some or all of the methyl groups of dimethylsilicone are substituted with fluorine-containing alkyl groups. In addition, an organically modified silicone substituted with an organic group such as a hydroxyl group or an amino group can be used. Further, these silicone antifoaming agents preferably have a kinematic viscosity of 1,000 to 1,000,000 mm ² /s at 25°C. Various silicone antifoaming agents such as KF series and FA series (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) are commercially available and can be used.

The content of the (F) silicone antifoaming agent in the lubricating oil composition is not particularly limited as long as the effects of the present invention are not impaired, but is usually 10 to 1000 ppm by mass based on the total mass of the lubricating oil composition. Depending on the purpose, it may be in the range of 10 to 100 ppm by mass. .

（式中、Ｒ^４はそれぞれ独立に、炭素数１～１２の炭化水素基である） [Other additives]
The lubricating oil composition according to the present invention comprises the components (A) to (F) described above as essential components, but may optionally contain various additives within a range in which the effects of the present invention can be obtained appropriately. Phosphate triester is one such additive. This phosphoric acid triester is different from the first phosphite and the second phosphate described above, and all hydrogen atoms constituting phosphorous acid are substituted with hydrocarbon groups, and can be represented by the following formula (4).

(Wherein, each R ⁴ is independently a hydrocarbon group having 1 to 12 carbon atoms)

^R4 may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. When ^R4 is an aliphatic hydrocarbon group, it may be linear or branched. In addition, each aliphatic hydrocarbon group preferably has 2 to 10 carbon atoms, more preferably 3 to 8 carbon atoms. Specific examples include n-propyl, n-butyl, i-butyl, n-pentyl, n-hexyl and n-octyl groups. Also, when R ⁴ is an aromatic hydrocarbon group, R ⁴ contains at least one aromatic ring. The aromatic rings are benzene rings or naphthalene rings, and they may be substituted with aliphatic hydrocarbon groups. Specific examples include a phenyl group, a naphthyl group, a methylphenyl group, an ethylphenyl group, a benzyl group and the like. Here, the three ^R4 's may be the same or different, but from the viewpoint of cost, they are preferably the same.

式中、
Ｍｅ： メチル基
ｉ－Ｂｕ： ｉ－ブチル基
ｎ－Ｏｃｔ： ｎオクチル基
である。
Specific examples of such phosphate triesters include the following.

During the ceremony,
Me: methyl group i-Bu: i-butyl group n-Oct: n-octyl group.

In the present invention, the content of the phosphate triester in the lubricating oil composition is determined based on phosphorus contained in the phosphate triester. When a lubricating oil composition according to the present invention comprises a phosphate triester, the phosphorus content derived from the phosphate triester is, for example, 50 to 1000 ppm, can range from 100 to 500 ppm, or from 200 to 400 ppm, based on the total weight of the lubricating oil composition.

In addition, the lubricating oil composition according to the present invention may further comprise other ingredients such as thickeners (viscosity modifiers), ashless dispersants, detergents, friction modifiers, metal deactivators, antioxidants, rust inhibitors, pour point depressants, demulsifiers, etc., which are commonly used in lubricating oil compositions. Moreover, as an antifoaming agent, an antifoaming agent other than the above-described (F) silicone antifoaming agent may be included.

As the thickener, known thickeners used in lubricating oils can be used without particular limitation. Examples thereof include polymethacrylate, ethylene-α-olefin copolymers and hydrides thereof, copolymers of α-olefins and ester monomers having polymerizable unsaturated bonds, polyisobutylene and hydrides thereof, styrene-diene copolymer hydrides, styrene-maleic anhydride ester copolymers, and polyalkylstyrenes. Among these, polymethacrylates, ethylene-α-olefin copolymers or hydrides thereof, or combinations thereof can be preferably used. Thickeners may be dispersant or non-dispersed. The weight average molecular weight of the thickener can be, for example, 2000-200,000. The lubricating oil composition may not contain a thickener, but when the lubricating oil contains a thickening agent, the content is preferably 0.01 to 25% by mass, more preferably 0.05 to 20% by mass, based on the total mass of the lubricating oil composition.

The ashless dispersant is not particularly limited, for example
(i) a succinimide or derivative thereof having at least one alkyl or alkenyl group in the molecule;
(ii) benzylamine or derivative thereof having at least one alkyl or alkenyl group in the molecule;
(iii) polyamines or derivatives thereof having at least one alkyl or alkenyl group in the molecule;
can be used.

The content of the ashless dispersant is 0.1 to 6.0% by mass, preferably 0.5 to 5.0% by mass, more preferably 0.5 to 4.0% by mass, based on the total mass of the lubricating oil composition. When the content of the ashless dispersant is at least the above lower limit, the seizure resistance of the lubricating oil composition can be further improved. Moreover, when the content of the ashless dispersant is equal to or less than the above upper limit, the electrical insulation of the lubricating oil composition can be maintained satisfactorily.

The cleaning agent can be selected from those commonly used in lubricants, and is not particularly limited. For example, an alkaline earth metal detergent can be used. More specifically, alkaline earth metal phenates, alkaline earth metal sulfonates, alkaline earth metal salicylates, or combinations thereof can be used, and it is preferred to use alkaline earth metal sulfonates, alkaline earth metal salicylates, or combinations thereof.

The content of the alkaline earth metal-based detergent in the lubricating oil composition is 10 to 1000 ppm, preferably 20 to 700 ppm, more preferably 50 to 500 ppm as an alkaline earth metal content based on the total mass of the lubricating oil composition. If the content of the alkaline earth metal-based detergent is at least the above lower limit, the wear resistance and seizure resistance can be further improved. Moreover, if the content of the alkaline earth metal-based detergent is equal to or less than the above upper limit, good electrical insulation can be maintained.

The friction modifier is not particularly limited, and compounds commonly used as friction modifiers for lubricating oils can be used. Examples thereof include compounds having 6 to 50 carbon atoms and containing one or more heteroatoms selected from oxygen atoms, nitrogen atoms and sulfur atoms in the molecule. More specifically, friction modifiers such as amine compounds, fatty acid esters, fatty acid amides, fatty acids, fatty alcohols, aliphatic ethers, urea-based compounds, and hydrazide-based compounds having at least one alkyl group or alkenyl group having 6 to 30 carbon atoms, particularly a straight-chain alkyl group, straight-chain alkenyl group, branched alkyl group, or branched alkenyl group having 6 to 30 carbon atoms in the molecule.

The content of the friction modifier is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and still more preferably 0.2% by mass or more, based on the total mass of the lubricating oil composition. When the content of the ashless friction modifier is within the above numerical range, the friction reducing effect is improved and the solubility of the additive can be maintained.

Examples of metal deactivators include triazole derivatives, thiadiazole derivatives, benzotriazole derivatives, tolyltriazole derivatives, imidazole derivatives, pyrimidine derivatives and the like. More specifically, alkylthiadiazole, N,N-bis(2-ethylhexyl)-(4 or 5)-methyl-1H-benzotriazole-1-methylamine, 1-[N,N-bis(2-ethylhexyl)aminomethyl]-benzotriazole, 1-[(2-ethylhexyl)aminomethyl]-benzotriazole, N,N-bis(2-ethylhexyl)-[(1,2,4-triazol-1-yl)methyl]amine, tri Lutriazole, 1,2,3-benzotriazole, mercaptobenzothiazole, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5-bisdialkyldithiocarbamate, 2-(alkyldithio)benzimidazole, β-(o-carboxybenzylthio)propiononitrile, imidazoline and the like. The lubricating oil composition may not contain a metal deactivator, but if the lubricating oil composition contains a metal deactivator, its content is preferably 0.01 to 1 wt%, more preferably 0.05 to 0.5 wt%, based on the total weight of the lubricating oil composition.

Examples of antioxidants include amine-based antioxidants and phenol-based antioxidants. As the amine antioxidant, known amine antioxidants such as alkylated diphenylamine, alkylated phenyl-α-naphthylamine, phenyl-α-naphthylamine and phenyl-β-naphthylamine can be used. As phenolic antioxidants, known phenolic antioxidants such as 2,6-di-tert-butyl-4-methylphenol (DBPC) and 4,4′-methylenebis(2,6-di-tert-butylphenol) can be used.

The content of the antioxidant is preferably 0.01 to 5% by mass, more preferably 0.1 to 3% by mass, based on the total mass of the lubricating oil composition. If the content of the antioxidant is within the above numerical range, a sufficient antioxidant effect can be obtained.

(F) Additional antifoaming agents other than silicone antifoaming agents include, for example, acrylic acid ester polymers, alkenylsuccinic acid derivatives, esters of polyhydroxyaliphatic alcohols and long-chain fatty acids, methyl salicylate, and o-hydroxybenzyl alcohol. The lubricating oil composition may contain no additional antifoaming agents, but if the lubricating oil composition contains additional antifoaming agents, the total content of the additional antifoaming agents is, for example, 0.0001 to 0.5% by weight, preferably 0.0005 to 0.1% by weight, based on the total weight of the lubricating oil composition.

Rust inhibitors include, for example, petroleum sulfonates, alkylbenzene sulfonates, dinonylnaphthalene sulfonates, alkenyl succinates, and polyhydric alcohol esters. The lubricating oil composition may not contain a rust inhibitor, but when the lubricating oil composition contains a rust inhibitor, the content thereof is preferably 0.01 to 1% by mass, more preferably 0.05 to 0.5% by mass, based on the total mass of the lubricating oil composition.

As the pour point depressant, for example, a polymethacrylate-based polymer compatible with the lubricating base oil used can be used. The lubricating oil composition may not contain a pour point depressant, but if the lubricating oil composition contains a pour point depressant, its content is preferably 0.01 to 1% by mass, more preferably 0.05 to 0.5% by mass, based on the total mass of the lubricating oil composition.

Examples of demulsifiers include polyalkylene glycol-based nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and polyoxyethylene alkyl naphthyl ethers. The lubricating oil composition may not contain a demulsifier, but if the lubricating oil composition contains a demulsifier, its content is preferably 0.01 to 5% by weight, more preferably 0.05 to 3% by weight, based on the total weight of the lubricating oil composition.

[Physical properties of lubricating oil composition]
The kinematic viscosity at 100° C. of the lubricating oil composition is preferably 3 to 10 mm ² /s or less, more preferably 4 to 8 mm ² /s. If the kinematic viscosity at 100 ° C. of the lubricating oil composition is within the above numerical range, the low-temperature viscosity characteristics will be good, sufficient fuel efficiency will be obtained, and the oil film will be well formed at the lubricating location. Excellent lubricity.

The kinematic viscosity at 40° C. of the lubricating oil composition is preferably 10-50 mm ² /s, more preferably 20-35 mm ² /s. If the kinematic viscosity at 40 ° C. of the lubricating oil composition is within the above numerical range, the low-temperature viscosity characteristics will be good, sufficient fuel efficiency will be obtained, and the oil film will be well formed at the lubricating point, resulting in excellent lubricity.

The viscosity index of the lubricating oil composition is preferably 120 or higher, more preferably 130 or higher, even more preferably 160 or higher. If the viscosity index of the lubricating oil composition is within the above numerical range, the low-temperature viscosity characteristics will be good, sufficient fuel efficiency will be obtained, and the oil film will be well formed at the lubrication point, resulting in excellent lubricity.

[Lubrication method]
The present invention also relates to a method of lubricating an automatic transmission or the powertrain of a hybrid or electric vehicle using the lubricating oil composition described above. In the present invention, by using a lubricating oil composition that exhibits sufficient antifoaming properties even when modified by heat or oxidation while maintaining good wear resistance, the performance of powertrains in use can be improved.

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[Method for measuring physical properties]
The physical properties of the lubricating base oils and the lubricating oil compositions of Examples and Comparative Examples were measured according to the following methods.
・Kinematic viscosity: Measured according to ASTM D-445.
- JIS foaming test: Based on JIS K2518:2017, the degree of foaming was measured according to the sequence II procedure. The degree of foaming was measured immediately after composition adjustment (fresh oil) and a denatured oil subjected to forced thermal/oxidative deterioration conditions. If the degree of foaming is 60 ml or less, it can be judged that the defoaming property is good. Here, the thermal/oxidative deterioration conditions are as described below.
[Thermal/Oxidative Degradation Conditions]
Test method: JIS K2514 compliant (excluding oil temperature and test time)
Oil temperature: 150°C
Test time: 120 hours

- High-speed four-ball test: Based on ASTM D 4172, the wear cone diameter (mm) was measured after operating at a rotation speed of 1500 rpm and a load of 392 N for 1 hour. If the wear cone diameter measured in this test is 0.60 mm or less, it can be judged that the wear resistance is good.

[Preparation of lubricating oil composition]
Using the lubricating base oil and various additives shown below, the lubricating oil compositions of the present invention (Examples 1 to 15) and comparative lubricating oil compositions (Comparative Examples 1 to 9) were prepared according to the formulations shown in Table 1. In Table 1, "inmass%" represents the mass% of each base oil based on the total mass of the lubricating base oil, and massppmP represents the phosphorus content derived from each component when based on the total mass of the lubricating oil composition.

[(A) Lubricating base oil]
The following lubricating base oils O-1 to O-5 were blended in the proportions shown in Table 1 to prepare lubricating base oils.
Lubricating base oil O-1: API Group III base oil (wax isomerized base oil, kinematic viscosity (40°C): 9.1 mm ² /s, kinematic viscosity (100°C): 2.6 mm ² /s, viscosity index: 127, pour point: -37.5°C, saturated content: 99.8% by mass, cyclic saturated content: 2.6% by mass)
Lubricating base oil O-2: API Group III base oil (wax isomerized base oil, kinematic viscosity (40°C): 15.7 mm ² /s, kinematic viscosity (100°C): 3.8 mm ² /s, viscosity index: 142, pour point: -22.5°C, saturated content: 99.8% by mass, cyclic saturated content: 4.8% by mass)
Lubricant base oil O-3: API Group IV base oil (poly-α-olefin, kinematic viscosity (40 ° C.): 4.9 mm ² / s, kinematic viscosity (100 ° C.): 1.7 mm ² / s, pour point: less than -45 ° C.)
Lubricant base oil O-4: API Group IV base oil (poly-α-olefin, kinematic viscosity (40 ° C.): 18.3 mm ² / s, kinematic viscosity (100 ° C.): 4.1 mm ² / s, viscosity index: 122, pour point: less than -45 ° C.)
Lubricating base oil O-5: API Group V base oil (di-2-ethylhexyl azelate, kinematic viscosity (40°C): 10.3 mm ² /s, kinematic viscosity (100°C): 2.9 mm ² /s, viscosity index: 138, pour point: less than -45°C)

[(B) Phosphate]
As a phosphate, phosphoric acid was blended in the amount shown in Table 1.
[(C) First phosphite ester]
As the first phosphite ester, dibutyl hydrogen phosphite represented by the formula (1-2) was blended in the amount shown in Table 1.
[(D) a second phosphite];
Diphenyl hydrogen phosphite represented by the formula (2-1) was blended in the amount shown in Table 1 as the second phosphite ester.
[(E) dithiophosphate derivative]
As a dithiophosphate derivative, 3-(di-isobutoxy-thiophosphorylsulfanyl)-2-methyl-propionic acid represented by formula (3-1) was blended in the amount shown in Table 1.
[(F) Silicone antifoaming agent]
As a silicone-based antifoaming agent, an antifoaming agent selected from the following was blended in the amount shown in Table 1.
Defoamer F-1: Polydimethyl silicone (trade name KF-96-50,000 cs, manufactured by Shin-Etsu Chemical Co., Ltd., kinematic viscosity (25° C.) 50,000 mm ² /s)
Defoamer F-2: Polydimethyl silicone (trade name KF-96-1,000,000 cs, manufactured by Shin-Etsu Chemical Co., Ltd., kinematic viscosity (25° C.) 1,000,000 mm ² /s)
Defoamer F-3: Fluorine-modified silicone (trade name FA-600, manufactured by Shin-Etsu Chemical Co., Ltd.)
[Phosphate triester]
As a phosphate triester, tricresyl phosphate represented by formula (4-1) was blended in the amount shown in Table 1.

[Other additives]
The contents of "other additives" in Table 1 are as follows.
Thickener: non-dispersed polymethacrylate (weight average molecular weight 30,000) 12% by mass
Ashless dispersant: Boron-containing succinimide 4% by weight
Antioxidant: diphenylamine antioxidant 0.5% by mass
Rubber swelling agent: 0.5% by mass of alkylsulfonolane
Metal deactivator: Thiadiazole 0.1% by mass
Cleaning agent: calcium sulfonate 0.2% by mass
Friction modifier: Fatty acid polyhydric alcohol ester 0.2% by mass
Glycolic acid dilaurylamide: 0.5% by mass

[Physical properties of lubricating oil composition]
Table 1 shows the physical property values obtained for the lubricating oil compositions of Examples 1 to 15 and Comparative Examples 1 to 9.

(Evaluation results)
Examples 1-15 according to the present invention all exhibited excellent defoaming and abrasion resistance. In addition, even if an antifoaming agent is included, if the contents of components (B) to (E) deviate from the ranges specified by the present invention, the wear resistance and/or antifoaming properties of the modified oil subjected to thermal and oxidative deterioration conditions are inferior.

Claims (9)

A lubricating oil composition,
(A) a lubricating base oil;
(B) a phosphate;
(C) the following formula (1):

(Wherein, each R ¹ is independently an aliphatic hydrocarbon group having 1 to 8 carbon atoms)
A first phosphite ester represented by
(D) the following formula (2):

(Wherein, each R ² is independently an aromatic hydrocarbon group having 6 to 12 carbon atoms)
A second phosphite ester represented by
(E) the following formula (3):

(In the formula, each R ³ is independently an aliphatic hydrocarbon group having 3 to 18 carbon atoms, and L ³ is an aliphatic hydrocarbon chain having 2 to 5 carbon atoms.)
A dithiophosphate derivative represented by
(F) a silicone antifoaming agent;
including
The phosphorus content derived from the (B) phosphate, the (C) first phosphite, the (D) second phosphite, and (E) the dithiophosphate derivative is 25 to 300 ppm by weight, 3 to 150 ppm by weight, 90 to 420 ppm by weight, and 3 to 75 ppm by weight, respectively, based on the total weight of the composition. A lubricating oil composition. The lubricating oil composition according to claim 1, wherein the content of (F) a silicone antifoaming agent is 10 to 1000 ppm by mass based on the total mass of the composition. 3. The lubricating oil composition according to claim 1 or 2, wherein both ^R1 's are linear alkyl groups. The lubricating oil composition according to any one of claims 1 to 3, wherein both R ² are unsubstituted phenyl or alkyl-substituted phenyl. A lubricating oil composition according to any one of claims 1 to 4, wherein L ³ is an ethylene group or a propylene group. The lubricating oil composition according to any one of claims 1 to 5, further comprising additives selected from the group consisting of thickeners, ashless dispersants, clearing agents, friction modifiers, metal deactivators, antioxidants, defoamers, rust inhibitors, pour point depressants, and demulsifiers. The lubricating oil composition according to any one of claims 1 to 6, which is used in automatic transmissions or powertrains of hybrid or electric vehicles. The lubricating oil composition according to any one of claims 1 to 6, which is a composition for a continuously variable transmission. A method of lubricating an automatic transmission or the powertrain of a hybrid or electric vehicle with a lubricating oil composition according to any one of claims 1-8.