JP6284450B2 - Lubricating oil composition for transmission - Google Patents

Description

  The present invention relates to a lubricating oil composition, and more specifically, a lubricating oil composition having fuel consumption savings due to excellent viscosity-temperature characteristics, and excellent wear and seizure resistance despite low viscosity, and compatibility with a sealing material, In particular, the present invention relates to a lubricating oil composition suitable for an automatic transmission and / or a continuously variable transmission.

  Conventional lubricating oils used in automatic transmissions, manual transmissions, internal combustion engines, etc., have a viscosity temperature to improve various durability such as thermal oxidation stability, wear resistance and fatigue resistance, and to improve fuel economy. Improvements in low-temperature viscosity properties such as improved properties, reduced low-temperature viscosity, improved low-temperature fluidity are required, and in order to improve such performance, antioxidants, detergent dispersants, and abrasion are appropriately applied to base oils. Lubricating oils containing various additives such as an inhibitor, a friction modifier, a seal swelling agent, a viscosity index improver, an antifoaming agent and a colorant are used.

  Recent transmissions and engines are required to be fuel efficient, lighter, smaller, and have higher output. Furthermore, with transmissions that are combined with higher output, improvements in power transmission capability are being pursued. . For this reason, the lubricant used in these products has a reduced product viscosity and base oil viscosity, maintains high lubrication performance, and prevents wear and fatigue on the surface of bearings, gears, etc., and seizure resistance. Is required. In general, in order to improve fuel economy, a technique for improving viscosity temperature characteristics by reducing the base oil viscosity and increasing the viscosity index improver is adopted. Since fatigue resistance deteriorates, development of a lubricating oil that can achieve both fuel saving, wear prevention, seizure resistance, and fatigue prevention at a higher level is eagerly desired.

Under these circumstances, in order to achieve both fuel economy and low-temperature viscosity characteristics and fatigue prevention, use of base oils with good low-temperature performance, use of high-viscosity base oils, phosphorus-based extreme pressure agents and sulfur-based materials It is known to add an appropriate amount of an extreme pressure agent or the like (for example, Patent Documents 1 to 3).
However, the above-mentioned method alone does not sufficiently achieve both viscosity-temperature characteristics and low-temperature performance, anti-fatigue properties, and seizure resistance. There is a need for the development of compositions.

Japanese Patent Application Laid-Open No. 2004-262979 Japanese Patent Laid-Open No. 11-286696 Special table 2003-514099 gazette

  In view of the circumstances as described above, the present invention has a lubricating oil composition, particularly an automatic transmission and / or a continuously variable transmission, which has excellent fuel saving performance, wear resistance, seizure resistance, and seal material compatibility. It is an object to provide a lubricating oil composition for a transmission suitable for a machine.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a lubricating oil composition containing a specific additive in a specific lubricating base oil has fuel saving performance and wear / seizure resistance, and a sealing material. The present inventors have found that the compatibility is excellent and have completed the present invention.

That is, the present invention, (A) a kinematic viscosity at 100 ° C. is 2.0 mm ² / s or more 3.8 mm ² / s or less,% _{C P} 60 85 less,% _{C N} is 15 or more and 40 or less,% C _A mineral base oil having _A of 3 or less,
(B) Phosphite ester in terms of phosphorus element is 200 to 600 ppm by mass,
(C) 50-200 ppm by mass of an alkali metal and / or alkaline earth metal detergent in terms of metal element,
(D) containing 20 to 120 mass ppm of boron-containing ashless dispersant in terms of boron element,
A lubricating oil composition, wherein the kinematic viscosity at 100 ° C. is not more than 2.5 mm ² / s or more 4.3 mm ² / s.

  Further, the present invention is the above-mentioned lubricating oil composition for a transmission, further comprising (E) polysulfide and / or thiadiazole.

  The present invention is also the above-described lubricating oil composition for a transmission, wherein the component (C) is calcium sulfonate.

  Furthermore, the present invention is the lubricating oil composition for a transmission as described in any one of the above, which is used for an automatic transmission.

  The lubricating oil composition of the present invention is low in viscosity for improving fuel efficiency, is excellent in antiwear and seizure resistance, and has good oxidation stability and compatibility with a sealing material, and It is a lubricating oil composition for a transmission that is particularly suitable for automatic transmissions and / or continuously variable transmissions because of its excellent seal leakage at low temperatures.

  The present invention is described in detail below.

  The lubricating oil composition for transmissions of the present invention (hereinafter also referred to as the lubricating oil composition of the present invention) contains a mineral oil base oil having the following properties as the component (A).

The kinematic viscosity at 100 ° C. of the component (A) is 2.0 mm ² / s or more, preferably 2.2 mm ² / s or more, more preferably 2.4 mm ² / s or more. Moreover, it is 3.8 mm < ² > / s or less, Preferably it is 3.6 mm < ² > / s or less, More preferably, it is 3.4 mm < ² > / s or less.
When the kinematic viscosity at 100 ° C. of the component (A) exceeds 3.8 mm ² / s, the viscosity temperature characteristics and the low temperature viscosity characteristics deteriorate, and when it is less than 2.0 mm ² / s, an oil film is formed at the lubrication point. Is insufficient because the metal fatigue resistance and heat resistance are inferior, and the evaporation loss of the lubricating base oil increases.

(A)% _{C P} of the component is 60 or more, preferably 62 or more, more preferably 65 or more. On the other hand, it is 85 or less, preferably 83 or less, and more preferably 80 or less. % C _P viscosity-temperature characteristic can exhibit fuel efficiency by the above range is obtained a further solubility and additives and sludge, is compatible to the seal member becomes excellent.

% _{C N} of the component (A) is 40 or less, preferably 38 or less, more preferably 35 or less. Moreover, it is 15 or more, 17 or more are preferable and 20 or more are more preferable. % C _N viscosity-temperature characteristic can exhibit fuel efficiency by the above range is obtained a further and solubility of additives and sludge, is compatible to the seal member becomes excellent.

% C _A of Component (A) is less than or equal to 3, preferably 2 or less, and more preferably 1 or less. % C _A thermal-oxidative stability decreases exceeds 3.

Moreover, there is no special restriction | limiting in the viscosity index of the mineral oil base oil of (A) component, However 85 or more are preferable, 90 or more are more preferable, 95 or more are further more preferable, 100 or more are the most preferable. On the other hand, it is preferably 160 or less, more preferably 150 or less, further preferably 140 or less, particularly preferably 135 or less, and most preferably 130 or less.
When the viscosity index is lower than 85, viscosity temperature characteristics that can exhibit fuel saving performance cannot be obtained. On the other hand, if it exceeds 160, normal paraffin increases in the base oil, so that the viscosity at a low temperature increases rapidly and the function as a lubricating oil is lost.

The pour point of the component (A) mineral oil base oil is not particularly limited, but is preferably −15 ° C. or lower, more preferably −20 ° C. or lower, still more preferably −22.5 ° C. or lower, particularly preferably. It is −25 ° C. or lower, most preferably −27.5 ° C. or lower. On the other hand, if it is too low, the viscosity index is lowered, and from the viewpoint of economy in the dewaxing process, it is preferably −50 ° C. or higher, more preferably −45 ° C. or higher, and further preferably −40 ° C. or higher.
By setting the pour point to −15 ° C. or less, a lubricating oil composition having excellent low-temperature viscosity characteristics can be obtained. On the other hand, if it is lower than −50 ° C., a sufficient viscosity index cannot be obtained.
As the dewaxing step, any of solvent dewaxing and contact dewaxing steps may be applied. However, the contact dewaxing step is particularly preferable because the low temperature viscosity characteristics can be further improved.

The flash point of the component (A) is preferably 160 ° C. or higher, more preferably 165 ° C. or higher, further preferably 170 ° C. or higher, and particularly preferably 175 ° C. or higher. When the flash point is less than 160 ° C., there is a possibility of causing a problem in safety at high temperature use.
In addition, the flash point as used in the field of this invention means the flash point measured based on JISK2265 (open type flash point).

  The aniline point of the component (A) is not particularly limited, but it is preferably 90 ° C or higher, more preferably 95 ° C or higher in that a lubricating oil composition having excellent low temperature viscosity characteristics and fatigue life can be obtained. Preferably, 97 ° C or higher is more preferable, and 100 ° C or higher is particularly preferable. On the other hand, the upper limit is not particularly limited, and may exceed 130 ° C. as one aspect of the present invention, but it is excellent in solubility of additives and sludge, and 130 ° C. or less in terms of excellent compatibility with a sealing material. Is preferable, 125 ° C. or lower is more preferable, and 120 ° C. or lower is further preferable.

The sulfur content of the component (A) is not particularly limited, but is preferably 0.1% by mass or less, more preferably 0.05% by mass or less, still more preferably 0.01% by mass or less, and most preferably It is desirable that is not substantially contained.
In addition, the sulfur content as used in the field of this invention means the value measured based on ASTM D4951.

As long as the component (A) has the above properties, the production method is not particularly limited. Specifically, the base oils (1) to (8) shown below are used as raw materials, and the raw oils and / or the The base oil obtained by refine | purifying the lubricating oil fraction collect | recovered from raw material oil with a predetermined | prescribed refinement | purification method, and collect | recovering lubricating oil fractions can be mentioned.
(1) Distilled oil by atmospheric distillation of paraffinic crude oil and / or mixed base crude oil (2) Distilled oil by vacuum distillation of atmospheric distillation residue of paraffinic crude oil and / or mixed base crude oil ( WVGO)
(3) Wax (such as slack wax) obtained by the lubricant dewaxing process and / or synthetic wax (Fischer-Tropsch wax, GTL wax, etc.) obtained by the gas-liquid (GTL) process, etc.
(4) One or two or more mixed oils selected from base oils (1) to (3) and / or mild hydrocracking treatment oils of the mixed oils (5) selected from base oils (1) to (4) (6) base oil (1), (2), (3), (4) or (5) debris oil (7) base oil (6) hydrocracked oil (8 ) Two or more mixed oils selected from base oils (1) to (7)

  The above-mentioned predetermined purification methods include hydrorefining such as hydrocracking and hydrofinishing; solvent refining such as furfural solvent extraction; dewaxing such as solvent dewaxing and catalytic dewaxing; acid clay and activated clay White clay purification; chemical (acid or alkali) cleaning such as sulfuric acid cleaning and caustic soda cleaning is preferable. In the present invention, one of these purification methods may be performed alone, or two or more may be combined. Moreover, when combining 2 or more types of purification methods, the order in particular is not restrict | limited, It can select suitably.

  Furthermore, the lubricating base oil according to the present invention is obtained by subjecting a base oil selected from the above base oils (1) to (8) or a lubricating oil fraction recovered from the base oil to a predetermined treatment. The following base oil (9) or (10) is particularly preferred.

(9) The base oil selected from the base oils (1) to (8) or the lubricating oil fraction recovered from the base oil is hydrocracked and recovered from the product or the product by distillation or the like. Hydrocracked mineral oil obtained by subjecting a lubricating oil fraction to dewaxing treatment such as solvent dewaxing or catalytic dewaxing, or distillation after the dewaxing treatment.
(10) A base oil selected from the base oils (1) to (8) or a lubricating oil fraction recovered from the base oil is hydroisomerized and recovered from the product or the product by distillation or the like. Hydroisomerized mineral oil obtained by subjecting the lubricating oil fraction to dewaxing treatment such as solvent dewaxing or catalytic dewaxing, or distillation after the dewaxing treatment.

When obtaining the lubricating base oil of (9) or (10) above, as the dewaxing step, the thermal / oxidative stability and low temperature viscosity characteristics can be further enhanced, and the fatigue prevention performance of the lubricating oil composition is further enhanced. It is particularly preferable to include a contact dewaxing step.
Moreover, when obtaining the lubricating base oil of (9) or (10) above, a solvent refining treatment and / or a hydrofinishing treatment step may be further provided as necessary.

  In the case of catalytic dewaxing (catalyst dewaxing), the hydrocracking / isomerization product oil is reacted with hydrogen in the presence of a suitable dewaxing catalyst under conditions effective to lower the pour point. In catalytic dewaxing, some of the high-boiling substances in the cracking / isomerization product are converted to low-boiling substances, the low-boiling substances are separated from the heavier base oil fraction, and the base oil fraction is fractionated. Two or more kinds of lubricating base oils are obtained. The low-boiling substances can be separated before obtaining the target lubricating base oil or during fractional distillation.

  The component (A) may be a single mineral oil or a mixture of two or more mineral oils. In the present invention, the lubricating base oil contains, for example, a small amount of synthetic oil, specifically, poly α-olefin, ester synthetic oil, etc. in addition to the mineral base oil of component (A). However, in the lubricating oil composition of the present invention, the lubricating base oil preferably contains at least 50% by mass of the mineral oil base oil of component (A), more preferably 60% by mass or more, More preferably, it is 75 mass% or more, Most preferably, it is 80 mass% or more.

  The lubricating oil composition of the present invention contains phosphorous acid ester as component (B).

  (B) The phosphorous acid ester which does not contain sulfur and / or (B2) the phosphorous acid ester which contains sulfur are mentioned as the phosphorous acid ester of component (B).

(B1) Phosphorous acid ester containing no sulfur is represented by the general formula P (OR) ₃ , and specific examples include phosphorous acid monoesters, phosphorous acid diesters, and phosphorous acid triesters. . Here, R is a hydrogen atom or a hydrocarbon group having 2 to 30 carbon atoms, preferably 3 to 20 carbon atoms, and at least one of R is a hydrocarbon group. (B1) Sulfurous acid ester containing no sulfur may be used alone or in combination of two or more.

  Examples of the hydrocarbon group having 2 to 30 carbon atoms include an alkyl group, a cycloalkyl group, an alkylcycloalkyl group, an alkenyl group, an aryl group, an alkylaryl group, and an arylalkyl group.

  Specific examples of the alkyl group include an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, various pentyl groups, various hexyl groups, and various heptyl groups. , Various octyl groups, various nonyl groups, various decyl groups, various dodecyl groups, and the like. Examples of the cycloalkyl group include a cyclohexyl group.

  Specific examples of alkenyl groups include butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl. And alkenyl groups such as an octadecenyl group (these alkenyl groups may be linear or branched, and the position of the double bond is also optional).

Specific examples of the aryl group include aryl groups such as a phenyl group and a naphthyl group.
Specific examples of the arylalkyl group include arylalkyl groups having 7 to 12 carbon atoms such as benzyl group, phenylethyl group, phenylpropyl group, phenylbutyl group, phenylpentyl group, and phenylhexyl group. It may be a chain or a branch).

Specific examples of preferable compounds of the component (B1) include, but are not limited to, monopropyl phosphite, monobutyl phosphite, monopentyl phosphite, monohexyl phosphite, monopeptyl phosphite, monooctyl phosphite and the like. Phosphoric acid monoalkyl ester (alkyl group may be linear or branched); Phosphorous acid mono (alkyl) aryl ester such as monophenyl phosphite, monocresyl phosphite; Dipropyl phosphite, dibutyl phosphite Dialkyl phosphites such as dipentyl phosphite, dihexyl phosphite, dipeptyl phosphite, dioctyl phosphite (the alkyl group may be linear or branched); diphenyl phosphite, dicresyl phosphite, etc. Di (alkyl) phosphite aryl Esters; Tripropyl phosphites, tributyl phosphites, tripentyl phosphites, trihexyl phosphites, tripeptyl phosphites, trioctyl phosphites, etc. Trialkyl phosphites (alkyl groups can be linear or branched) And tri (alkyl) aryl phosphites such as triphenyl phosphite and tricresyl phosphite; and mixtures thereof.
Among these, dialkyl phosphite is preferable, and dibutyl phosphite is particularly preferable.

  (B2) As the phosphorous acid ester containing sulfur, phosphorous acid esters, thiophosphite monoesters, and thiophosphite diesters containing sulfur in the side chain represented by the following general formula (1) And thiophosphorous triesters. (B2) Sulfurous acid ester containing sulfur may be used alone or in combination of two or more.

In Formula (1), X ¹ , X ² and X ³ each independently represent an oxygen atom or a sulfur atom. R ¹ , R ² and R ³ are each independently a hydrogen atom or a hydrocarbon group having 2 to 30 carbon atoms, preferably 3 to 20 carbon atoms, more preferably 4 to 8 carbon atoms, and at least one is a hydrocarbon group. It is. The hydrocarbon group may contain sulfur. This can improve wear resistance and metal fatigue durability. Also, if more than two of R ¹ to R ³ is a hydrocarbon group, is preferably each a different number of carbons. The average number of carbon atoms is preferably in the above range. This can improve wear resistance and metal fatigue durability.
In addition, as a C2-C30 hydrocarbon group, the same thing as what was previously shown by R in (B1) component is mentioned.

  As an example of a preferable compound of component (B2), specifically, a phosphite containing sulfur in the side chain such as 3-thiopentyl hydrogen phosphite, 3-thioundecyl hydrogen phosphite, Trialkyl triphosphite such as tripropyltrithiophosphite, tributyltrithiophosphite, tripentyltrithiophosphite, trihexyltrithiophosphite, tripeptyltrithiophosphite, trioctyltrithiophosphite, trilauryltrithiophosphite ( The alkyl group may be linear or branched); tri (alkyl) aryl phosphites such as triphenyltrithiophosphite and tricresyltrithiophosphite; and mixtures thereof.

  In the present invention, any one of (B1) sulfur phosphite swell containing no sulfur or (B2) sulfur phosphite selle containing sulfur or a mixture thereof can be used. However, seizure resistance, wear resistance, and fatigue life can be used. From the point of (B2), it is preferable to contain the phosphorous ester containing sulfur.

  The content of the component (B) in the lubricating oil composition of the present invention is such that the phosphorus content in the lubricating oil composition is 200 mass ppm or more in terms of phosphorus element in order to impart excellent extreme pressure properties and fatigue life. , Preferably it is 230 mass ppm or more, More preferably, it is 250 mass ppm or more. On the other hand, it is 600 mass ppm or less, preferably 550 mass ppm or less, more preferably 500 mass ppm or less. When the amount of phosphorus is less than 200 ppm by mass, there is no effect on extreme pressure properties and fatigue life, and when it exceeds 600 ppm by mass, the oxidation stability and durability of resin materials such as nylon are deteriorated and fatigue is also reduced. Since it also has an adverse effect on the service life, each is not preferable.

  The lubricating oil composition of the present invention contains an alkali metal and / or alkaline earth metal detergent as component (C).

  (C) Alkali metal and / or alkaline earth metal detergents include alkali metals such as sodium and potassium, sulfonates, phenates, salicylates having alkaline earth metals such as magnesium, calcium and barium as positive components, and These mixtures are preferably used.

Examples of the sulfonate include an alkali metal salt or an alkaline earth metal salt of an alkyl aromatic sulfonic acid obtained by sulfonating an alkyl aromatic compound having a molecular weight of 100 to 1500, preferably 200 to 700, particularly magnesium. Salts and / or calcium salts are preferably used.
Specific examples of the alkyl aromatic sulfonic acid include so-called petroleum sulfonic acid and synthetic sulfonic acid. As the petroleum sulfonic acid, those obtained by sulfonating an alkyl aromatic compound of a lubricating oil fraction of mineral oil or so-called mahoganic acid which is produced as a by-product when white oil is produced is used. In addition, as the synthetic sulfonic acid, for example, an alkylbenzene having a linear or branched alkyl group, which is produced by alkylating polyolefin into benzene, which is produced in an alkylbenzene production plant that is a raw material for detergents, is used as a raw material And a sulfonated one of this, a sulfonated dinonylnaphthalene, or the like.
In particular, a sulfonate obtained by using polyolefin as an alkylating agent is preferable from the viewpoint of friction characteristics.

  Also, as typical metal sulfonates, the above alkyl aromatic sulfonic acids can be directly reacted with alkali or alkaline earth metal bases such as metal oxides or hydroxides, or particularly alkaline earth metal-based sulfonates. In this case, not only the neutral alkaline earth metal sulfonate obtained by replacing the alkaline earth metal salt such as sodium salt or potassium salt with an alkaline earth metal salt, but also the above neutral alkaline earth metal sulfonate Basic alkaline earth metal sulfonates obtained by heating alkaline earth metal salts and alkaline earth metal bases (hydroxides and oxides) in the presence of water, carbon dioxide and / or boric acid or boric acid Carbonates obtained by reacting the above neutral alkaline earth metal sulfonates with alkaline earth metal bases in the presence of salts Also included are overbased alkaline earth metal sulfonates and borate overbased alkaline earth metal sulfonates.

  Specific examples of the phenate include alkali metal salts or alkaline earth metal salts of alkylphenols having 1 to 2 alkyl groups having 4 to 20 carbon atoms in the presence or absence of elemental sulfur, and mixtures thereof. Is mentioned.

  Specifically, as the salicylate, an alkali metal salt or alkaline earth metal salt of an alkyl salicylic acid having 1 to 2 alkyl groups having 4 to 20 carbon atoms in the presence or absence of elemental sulfur and a mixture thereof Etc.

  Among these, sulfonate is preferable from the viewpoint of seizure resistance, wear resistance, and oxidation stability, alkaline earth metal sulfonate is particularly preferable, and calcium sulfonate is most preferable.

The base number of the component (C) is preferably 2 mgKOH / g or more, more preferably 10 mgKOH / g or more, further preferably 50 mgKOH / g or more, and particularly preferably 100 mgKOH / g or more from the viewpoint of friction characteristics. Moreover, it is preferable that it is 500 mgKOH / g or less, and 450 mgKOH / g or less is more preferable.
The base number referred to here is 6. JIS K2501 “Petroleum products and lubricating oils-Neutralization number test method”. The base number [mgKOH / g] measured by the hydrochloric acid method according to the above.

  The content of the component (C) is 50 mass ppm or more, preferably 60 mass ppm or more, more preferably 70 mass ppm or more in terms of the total amount of the lubricating oil composition and in terms of metal elements, from the viewpoint of oxidation stability. On the other hand, from the standpoint of seizure resistance and wear resistance, it is 200 mass ppm or less, preferably 180 mass ppm or less, and more preferably 160 mass ppm or less.

  The lubricating oil composition of the present invention contains a boron-containing ashless dispersant as component (D).

Examples of boron-containing ashless dispersants include boronated products of ashless dispersants commonly used in lubricating oils.
Examples of the ashless dispersant include nitrogen-containing compounds having at least one linear or branched alkyl group or alkenyl group having 40 to 400 carbon atoms or derivatives thereof, or alkyl or alkenyl succinimide. . One type or two or more types arbitrarily selected from these can be blended.
As the component (D), a boron-containing ashless dispersant usually used in lubricating oils can be used, but a boron-containing succinimide is preferable because it is excellent in cleanliness.

  The carbon number of the alkyl group or alkenyl group that the alkyl or alkenyl succinimide has is preferably 40 to 400, more preferably 60 to 350. When the carbon number of the alkyl group or alkenyl group is less than 40, the solubility of the compound in the lubricating base oil tends to be reduced. On the other hand, when the carbon number of the alkyl group or alkenyl group exceeds 400, the lubricating oil composition The low-temperature fluidity of the product tends to deteriorate. This alkyl group or alkenyl group may be linear or branched, but specifically, preferred are derived from olefin oligomers such as propylene, 1-butene and isobutylene, and co-oligomers of ethylene and propylene. And a branched alkyl group or a branched alkenyl group.

  Particularly preferred is a succinimide having an alkyl group or an alkenyl group of a polymer such as 1-butene and isobutylene. The molecular weight of the alkyl group or alkenyl group is preferably 1000 or more, and more preferably 1500 or more. Moreover, 3000 or less is preferable. If it is less than 1000, the friction characteristics of the wet clutch may be deteriorated, and if it exceeds 3000, the low-temperature viscosity of the composition is deteriorated.

  The succinimide may be a mono-type succinimide, a bis-type succinimide, or a mixture thereof.

  The method for producing succinimide is not particularly limited. For example, an alkyl succinic acid or alkenyl succinic acid obtained by reacting a compound having an alkyl group or alkenyl group having 40 to 400 carbon atoms with maleic anhydride at 100 to 200 ° C. It can be obtained by reacting with a polyamine. Specific examples of the polyamine include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine.

  The content of the component (D) is 20 mass ppm or more, preferably 30 mass ppm or more, in terms of the total amount of the lubricating oil composition in terms of boron element, from the viewpoint of improving fatigue life and extreme pressure. On the other hand, it is 120 mass ppm or less, 100 mass% ppm or less is preferable, and 80 mass ppm or less is more preferable. If it is less than 20 mass ppm, the effect is insufficient, and if it exceeds 120 mass ppm, the performance may rather deteriorate.

  Further, the ratio of the boron content of the component (D) and the phosphorus content of the component (B) (ratio of boron element equivalent mass% / phosphorus element equivalent mass% (B / P)) is preferably 0.07 or more, More preferably, it is 0.09 or more, More preferably, it is 0.12 or more. Moreover, it is preferable that it is 0.42 or less, More preferably, it is 0.35 or less, More preferably, it is 0.25 or less. By setting the B / P ratio in the above range, fatigue life and extreme pressure can be improved in a balanced manner.

  Further, the lubricating oil composition of the present invention preferably further contains polysulfide and / or thiadiazole as the component (E).

  Examples of the polysulfide include sulfurized fats and oils, sulfurized olefins, and dihydrocarbyl polysulfides.

  Examples of sulfurized fats and oils include sulfurized lard, sulfurized rapeseed oil, sulfurized castor oil, sulfurized soybean oil, and sulfurized rice bran oil; disulfide fatty acids such as sulfurized oleic acid; and sulfurized esters such as methyl sulfide oleate. .

Examples of the sulfurized olefin include a compound represented by the following general formula (2).
R ¹ —S _X —R ² (2)
In the general formula (2), R ¹ represents an alkenyl group having 2 to 15 carbon atoms, R ² represents an alkyl group or alkenyl group having 2 to 15 carbon atoms, and x represents an integer of 1 to 8. x is preferably 2 or more, and particularly preferably 4 or more.
This compound can be obtained by reacting an olefin having 2 to 15 carbon atoms or a dimer or tetramer thereof with a sulfurizing agent such as sulfur or sulfur chloride.
As the olefin, for example, propylene, isobutene, diisobutene and the like are preferably used.

Dihydrocarbyl polysulfide is a compound represented by the following general formula (3).
R ³ -S _y -R ⁴ (3)
In General Formula (3), R ³ and R ⁴ are each independently an alkyl group having 1 to 20 carbon atoms (including a cycloalkyl group), an aryl group having 6 to 20 carbon atoms, or an aryl having 7 to 20 carbon atoms. An alkyl group or an alkylaryl group, which may be the same as or different from each other, and y represents an integer of 2 to 8;

Specific examples of R ³ and R ⁴ include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, and various pentyl groups. Groups, various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups, various decyl groups, various dodecyl groups, cyclohexyl groups, phenyl groups, naphthyl groups, tolyl groups, xylyl groups, benzyl groups, and phenethyl groups. be able to.

  Specific examples of preferred dihydrocarbyl polysulfides include dibenzyl polysulfide, di-tert-nonyl polysulfide, didodecyl polysulfide, di-tert-butyl polysulfide, dioctyl polysulfide, diphenyl polysulfide, and dicyclohexyl polysulfide. It is done.

  (E) As a polysulfide of a component, Most preferably, it is a sulfurized olefin, More preferably, x shown by General formula (2) is a thing of 4-8.

  Examples of the thiadiazole include a 1,3,4-thiadiazole compound represented by the following general formula (4), a 1,2,4-thiadiazole compound represented by the general formula (5), and a general formula (6). 1,4,5-thiadiazole compounds.

In the general formulas (4) to (6), R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ may be the same or different, and each independently represents a hydrogen atom or 1 to 30 carbon atoms. And g, h, i, j, k, and l each independently represent an integer of 0 to 8. Examples of the hydrocarbon group having 1 to 30 carbon atoms include an alkyl group, a cycloalkyl group, an alkylcycloalkyl group, an alkenyl group, an aryl group, an alkylaryl group, and an arylalkyl group.

  In addition, the lubricating oil composition of the present invention can contain various additives as required as long as the excellent viscosity temperature characteristics and low temperature performance, fatigue resistance and seizure resistance are not impaired. Such an additive is not particularly limited, and any additive conventionally used in the field of lubricating oils can be blended. Specific examples of such lubricating oil additives include ashless dispersants other than the component (D), antioxidants, extreme pressure agents, antiwear agents, friction modifiers, pour point depressants, corrosion inhibitors, and rust inhibitors. Agents, demulsifiers, metal deactivators, antifoaming agents and the like. These additives may be used individually by 1 type, and may be used in combination of 2 or more type.

  The lubricating oil composition of the present invention preferably contains substantially no viscosity index improver. The fact that the viscosity index improver is substantially not included is not included at all, or even if it is included, it is compared with the amount (2 to 10% by mass) that is usually blended with the expectation of the effect as a viscosity index improver. This means that the amount is extremely small. Specifically, the content is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, and most preferably not contained at all, based on the total amount of the composition. When the content of the viscosity index improver exceeds 1.0% by mass, there is a concern about viscosity reduction during use due to shearing, and in order to maintain the minimum viscosity as a lubricating oil that maximizes fuel economy. It is not preferable.

  Examples of the viscosity index improver here include non-dispersed or dispersed viscosity index improvers. Specific examples of the non-dispersed viscosity index improver include alkyl acrylates or alkyl methacrylates having 1 to 30 carbon atoms, olefins having 2 to 20 carbon atoms, styrene, methylstyrene, maleic anhydride esters, maleic anhydride amides, and the like. One or two or more monomers selected from the above or a copolymer thereof or a hydride thereof can be exemplified.

  Examples of the dispersion type viscosity index improver include dimethylaminomethyl methacrylate, diethylaminomethyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, 2-methyl-5-vinylpyridine, morpholinomethyl methacrylate, morpholinoethyl methacrylate, and N-vinylpyrrolidone. A copolymer of a monomer component of a non-dispersion type viscosity index improver, or a copolymer of one or two or more types of monomers selected from: A hydride etc. can be illustrated.

  Like the viscosity index improver, the lubricating oil composition of the present invention preferably contains substantially no pour point depressant. The fact that it does not contain a pour point depressant substantially does not contain at all, or even if it is contained, it is usually added in an amount expected to have an effect as a pour point depressant (0.01 to 3% by mass). This means that the amount is very small compared to. Specifically, the content is 0.005% by mass or less, more preferably 0.001% by mass or less, and most preferably not contained at all, based on the total amount of the composition. When the content of the pour point depressant exceeds 0.005% by mass, there is a concern about viscosity reduction during use due to shearing, and in order to maintain the minimum viscosity as a lubricating oil that maximizes fuel economy. It is not preferable.

  Examples of the ashless dispersant other than the component (D) include ashless dispersants such as alkenyl succinimide that does not contain boron.

  Examples of the antioxidant include ashless antioxidants such as phenols and amines, and metal antioxidants such as copper and molybdenum.

  Examples of the friction modifier include ashless friction modifiers such as fatty acid esters, aliphatic amines, and fatty acid amides, and metal friction modifiers such as molybdenum dithiocarbamate and molybdenum dithiophosphate.

  Examples of the corrosion inhibitor include benzotriazole, tolyltriazole, and imidazole compounds.

  Examples of the rust preventive include petroleum sulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenyl succinic acid ester, and polyhydric alcohol ester.

  Examples of the demulsifier include polyalkylene glycol nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, or polyoxyethylene alkyl naphthyl ether.

  Examples of the metal deactivator include imidazoline, pyrimidine derivatives, benzotriazole or derivatives thereof, 2- (alkyldithio) benzimidazole, β- (o-carboxybenzylthio) propiononitrile.

Examples of antifoaming agents include silicone oils having a kinematic viscosity at 25 ° C. of less than 0.1 to 100 mm ² / s, alkenyl succinic acid derivatives, esters of polyhydroxy aliphatic alcohols and long chain fatty acids, methyl salicylates and o. -Hydroxybenzyl alcohol etc. are mentioned.

  When these additives are contained in the lubricating oil composition of the present invention, the content is preferably from 0.1 to 20% by mass based on the total amount of the composition.

Kinematic viscosity at 100 ° C. of the lubricating oil composition of the present invention is required to be 2.5~4.3mm ² / s, preferably 2.7 mm ² / s or more, or less 4.0 mm ² / s is there.
If the kinematic viscosity at 100 ° C. of less than 2.5 mm ² / s has likely to cause problems in the oil film retention and evaporation of the lubricating site, if the kinematic viscosity at 100 ° C. is more than 4.3 mm ² / s There is a risk that fuel efficiency will be insufficient.

  Although there is no restriction | limiting in particular about the viscosity index of the lubricating oil composition of this invention, Preferably it is 120 or more from a viewpoint of fuel-saving property, More preferably, it is 140 or more.

The Brookfield (BF) viscosity at −40 ° C. of the lubricating oil composition of the present invention is preferably 15000 mPa · s or less, more preferably 10,000 mPa · s or less, still more preferably 8000 mPa · s or less, particularly preferably 5000 mPa · s. s or less, and most preferably 4000 mPa · s or less. If it exceeds 15000 mPa · s, the viscous resistance at the start will be high, and the fuel efficiency will be reduced.
The Brookfield viscosity referred to here is a value measured by ASTM D2983.

The lubricating oil composition of the present invention is a lubricating oil composition having excellent wear resistance and fatigue resistance and excellent low-temperature fluidity, and is particularly suitable as an automatic transmission oil and / or continuously variable transmission oil. It is.
The lubricating oil composition of the present invention is also excellent in performance as a transmission oil other than the above, and is used for automatic transmissions such as automobiles, construction machines, and agricultural machines, manual transmissions, and differential gears. Also preferably used. Other lubricants that require wear prevention, fatigue prevention and low temperature viscosity characteristics, such as industrial gear oils, automobiles such as motorcycles and automobiles, power generation, marine gasoline engines, diesel engines, and gas It can also be suitably used for engine lubricating oil, turbine oil, compressor oil, and the like.

  Hereinafter, the content of the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these.

(Examples 1-9 and Comparative Examples 1-9)
As shown in Table 1, lubricating oil compositions of the present invention (Examples 1 to 9 ) and comparative lubricating oil compositions (Comparative Examples 1 to 9) were prepared. The resulting composition was measured for kinematic viscosity, viscosity index, sealing material compatibility, low temperature viscosity characteristics, wear resistance, and oxidation stability, and the results are also shown in Table 1.

(1) Sealing material compatibility In the sealing material immersion test, acrylic rubber material (T445) was immersed under conditions of an oil temperature of 150 ° C. for 240 hours in accordance with JIS K 6258. The volume and hardness of the rubber material after immersion were measured, and the volume change rate and hardness change from before immersion were determined. If the volume is reduced, the sealing property is adversely affected. If the volume is excessively increased, the sliding property is adversely affected. Therefore, the change rate is 0% or more, and the smaller the change is, the better the sealing material compatibility is. The smaller the change in hardness, the better the seal material compatibility.
(2) Low-temperature viscosity characteristic Based on ASTM D2983, the Brookfield viscosity (BF viscosity) in -40 degreeC of each lubricating oil composition was measured. In this test, the smaller the value of the BF viscosity, the better the low temperature fluidity. However, the rubber material is cured and the sealing performance is lost at low temperatures. Is preferred.
(3) Abrasion prevention property A shell quaternary test based on ASTM D4172 was conducted. The wear scar diameter after sliding for 1 hour under the conditions of a load of 392 N, a rotational speed of 1900 rpm, and an oil temperature of 100 ° C. was measured.
(4) Falex seizure test In accordance with ASTM D3233, a seizure load at 290 revolutions and 100 ° C of each lubricating oil composition was measured using a Falex tester. In this test, the larger the seizure load, the better the seizure resistance.
(5) Oxidation stability test An oxidation stability test based on JIS K 2514 was performed. Oxidation stability was measured at an oil temperature of 150 ° C. for 96 hours.

  As is apparent from the results in Table 1, it can be seen that the lubricating oil composition of the present invention is excellent in fuel saving performance, wear resistance / seizure resistance, and sealing material compatibility.

Claims (4)

(A) a kinematic viscosity at 100 ° C. is 2.0 mm ² / s or more 3.8 mm ² / s or less,% _{C P} is 60 or more 83 or less,% _{C N} is 15 or more and 40 or less,% _{C A} is 3 or less Mineral oil base oil
(B) Phosphite containing sulfur in the side chain is 200 to 600 ppm by mass in terms of phosphorus element,
(C) 50-200 ppm by mass of an alkali metal and / or alkaline earth metal detergent in terms of metal element,
(D) containing 20 to 120 mass ppm of boron-containing ashless dispersant in terms of boron element,
The lubricating oil composition kinematic viscosity at 100 ° C. is equal to or less than 2.5 mm ² / s or more 4.3 mm ² / s.   The transmission lubricating oil composition according to claim 1, further comprising (E) polysulfide and / or thiadiazole.   The lubricating oil composition for a transmission according to claim 1 or 2, wherein the component (C) is calcium sulfonate.   The lubricating oil composition for a transmission according to any one of claims 1 to 3, which is used for an automatic transmission.