JP5847892B2 - Transmission oil composition for automobiles - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a transmission oil composition for automobiles, and more specifically, an automotive transmission oil composition that is excellent in lubricity and excellent in insulation and cooling, and that is suitably used for an electric motor-equipped vehicle such as an electric vehicle or a hybrid vehicle. Related to things.

  In order to improve fuel efficiency in recent years, automobile transmissions are required to have improved power transmission efficiency and reduced size and weight. As the transmission mechanism, a manual transmission or an automatic transmission is mounted, and recently, a continuously variable transmission has been mounted on some vehicles.

  In addition, lead live batteries, nickel metal hydride batteries, lithium ion batteries, fuel cells, and the like, and electric vehicles equipped with electric motors, or hybrid vehicles using these in combination with an internal combustion engine have been developed. In these automobiles, transmission oil and electric motor oil are used separately.

  Recently, in an electric vehicle or a hybrid vehicle, it is required to reduce the size and weight by packaging a transmission and an electric motor. In this case, it is necessary to share transmission oil and electric motor oil, and in addition to the lubrication performance required for transmission oil, there is a demand for a new oil that has both insulation and cooling properties required for electric motor oil. Yes.

  Transmission oils are required to have heat / oxidation stability, clean dispersibility, wear resistance, seizure resistance, and the like. In order to meet these requirements, transmission oils are generally mineral or synthetic base oils with various additives (eg, antioxidants, detergent dispersants, antiwear agents, rust inhibitors, metal deactivators, frictions). Addition agents such as a regulator, an antistagnation agent, a colorant, a seal swelling agent, and a viscosity index improver are used. Since normal transmission oil has low volume resistivity and insufficient insulation, when used as an electric motor oil, there is a possibility that problems such as a short circuit of the electric motor may occur. Moreover, since kinematic viscosity is high, there exists a possibility that malfunctions, such as a cooling failure and a power loss, may arise.

  On the other hand, the electric motor oil is required to have insulating properties, cooling properties, and the like, but does not need lubricity, and therefore contains almost no additive. For this reason, when electric motor oil is used for a transmission, there exists a problem that a bearing, a gearwheel, etc. will wear remarkably. In addition, with the progress of miniaturization and high rotation of the electric motor, the electric motor oil is required to have excellent cooling properties.

Patent Document 1 discloses a base oil selected from the group consisting of mineral oils, synthetic oils, and mixtures thereof for the purpose of excellent insulating properties, cooling properties, and lubricity, and 0. 1 to 15.0% by mass of (A) a hydrocarbon group-containing zinc dithiophosphate, (B) a triaryl phosphate, (C) a phosphorus compound selected from the group consisting of triaryl thiophosphates and mixtures thereof In addition, a transmission oil composition for automobiles having a volume resistivity at 80 ° C. of 1 × 10 ⁷ Ω · m or more is disclosed.
International Publication WO2002-097017

  However, the transmission oil composition for automobiles of Patent Document 1 has a problem that not only the cooling property of the electric motor is insufficient, but also a study on the low temperature starting property has not been made.

  Therefore, the present invention is an oil composition for a transmission and an electric motor mounted in an electric vehicle or a hybrid vehicle, an oil composition for a transmission and an electric motor, or a transmission and an electric motor are packaged. An object of the present invention is to provide a transmission oil composition for automobiles that is useful as an oil composition for equipment in which these lubrication systems are shared, and that is excellent in lubricity and insulation, and that is excellent in low-temperature startability and cooling performance. To do.

1st this invention contains the lube base oil whose urea adduct value is 4 mass% or less, whose kinematic viscosity in 40 degreeC is 25 mm < ² > / s or less, and whose viscosity index is 100 or more, and heat transfer coefficient Is a transmission oil composition for automobiles having a 720 W / m ² · ° C. or higher.

  In the first aspect of the present invention, the iodine value of the lubricating base oil is preferably 1 or less.

  The transmission oil composition for automobiles according to the first aspect of the present invention is suitably used as a transmission oil for hybrid cars.

  The transmission oil composition for automobiles of the present invention is excellent in lubricity and insulation by using a predetermined lubricating base oil, and is excellent in low-temperature startability and cooling, and is mounted on an electric vehicle or a hybrid vehicle. Useful as an oil composition for transmissions and electric motors, a combined oil composition for transmissions and electric motors, or an oil composition for equipment in which transmissions and electric motors are packaged and these lubrication systems are shared It is.

<Transmission oil composition for automobile>
The transmission oil composition for automobiles of the present invention (hereinafter sometimes simply referred to as a lubricating oil composition) has a urea adduct value of 4% by mass or less, a kinematic viscosity at 40 ° C. of 25 mm ² / s or less, A lubricating base oil having a viscosity index of 100 or more is provided.

(Lubricant base oil)
As long as the lubricating base oil satisfies the above performance, a mineral base oil and / or a synthetic base oil used for ordinary lubricating oils can be used. For example, two or more kinds of mineral base oils may be mixed and used, or two or more kinds of synthetic base oils may be mixed and used, or a mineral oil base oil and a synthetic base oil May be used in combination.

Mineral oil base oils include, for example, solvent removal, solvent extraction, hydrocracking, and solvent dewaxing of lubricating oil fractions obtained by distillation under reduced pressure of atmospheric residual oil obtained by atmospheric distillation of crude oil. Lubricants manufactured by one or more processes such as hydrorefining, or manufactured by isomerizing GTL WAX (Gas Liquid Liquid) manufactured by wax isomerized mineral oil, Fischer-Tropsch process, etc. An oil base oil etc. are mentioned. In particular, feedstock containing normal paraffin is hydrocracked / hydroisomerized so that the urea adduct value is 4% by mass or less, the kinematic viscosity at 40 ° C. is 25 mm ² / s or less, and the viscosity index is 100 or more. Mineral oil base oils obtained by converting to the above are preferred.

  Specific examples of synthetic base oils include polybutene or hydrides thereof; poly-α-olefins such as 1-octene oligomers and 1-decene oligomers or hydrides thereof; ditridecyl glutarate, di-2-ethylhexyl adipate Diesters such as diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate; polyol esters such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate; Copolymers of dicarboxylic acids such as dibutyl maleate and α-olefins having 2 to 30 carbon atoms; aromatic synthetic oils such as alkylnaphthalenes, alkylbenzenes, and aromatic esters, or mixtures thereof It is. Among them, polybutene or hydrides thereof; poly-α-olefins such as 1-octene oligomers and 1-decene oligomers or hydrides thereof are preferably used.

Hydrocracking / hydroisomerization of feedstock oil containing normal paraffin so that the urea adduct value is 4 mass% or less, the kinematic viscosity at 40 ° C. is 25 mm ² / s or less, and the viscosity index is 100 or more. The mineral base oil obtained by the above, the synthetic base oil described above, or a mixture thereof can satisfy the requirements of viscosity-temperature characteristics, low-temperature viscosity characteristics and thermal conductivity at a high level.

(Urea adduct value)
The urea adduct value of the lubricating base oil is measured by the following method. 100 g of weighed sample oil (lubricating base oil) is placed in a round bottom flask, 200 mg of urea, 360 ml of toluene and 40 ml of methanol are added and stirred at room temperature for 6 hours. As a result, white granular crystals are produced as urea adducts in the reaction solution. The reaction solution is filtered through a 1 micron filter to collect the produced white granular crystals, and the obtained crystals are washed 6 times with 50 ml of toluene. The collected white crystals are put into a flask, 300 ml of pure water and 300 ml of toluene are added, and the mixture is stirred at 80 ° C. for 1 hour. The aqueous phase is separated and removed with a separatory funnel, and the toluene phase is washed three times with 300 ml of pure water. A desiccant (sodium sulfate) is added to the toluene phase for dehydration, and then toluene is distilled off. The ratio (mass percentage) of the urea adduct thus obtained to the sample oil was defined as the urea adduct value.

  In the measurement of urea adduct value, as urea adducts, isoparaffin components that adversely affect low-temperature viscosity characteristics or components that deteriorate thermal conductivity, and when normal paraffin remains in the lubricating base oil The normal paraffin is collected accurately and reliably. For this reason, the urea adduct value is excellent as an evaluation index for low temperature viscosity characteristics and thermal conductivity of the lubricating base oil. The inventors of the present invention have analyzed by using GC and NMR that the main component of the urea adduct is a normal paraffin and an isoparaffin urea adduct having 6 or more carbon atoms from the end of the main chain to the branch position. I confirmed that there was.

  The urea adduct value of the lubricating base oil is preferably 3.5% by mass or less, more preferably 3% by mass from the viewpoint of improving the low temperature viscosity characteristic without impairing the viscosity-temperature characteristic and obtaining high thermal conductivity. Hereinafter, it is more preferably 2.5% by mass or less, particularly preferably 2.0% by mass or less. In addition, the urea adduct value of the lubricating base oil may be 0% by mass, but it is possible to obtain a lubricating base oil having sufficient low-temperature viscosity characteristics and a higher viscosity index, and eases the dewaxing conditions and is economical. From the viewpoint of excellent properties, it is preferably at least 0.1 mass%, more preferably at least 0.5 mass%, even more preferably at least 0.8 mass%, particularly preferably at least 1.0 mass%.

(Kinematic viscosity)
The kinematic viscosity at 40 ° C. of the lubricating base oil used in the present invention is 25 mm ² / s or less, preferably 20 mm ² / s or less, more preferably 18 mm ² / s or less, and even more preferably 14 mm ² / s or less. Particularly preferably, it is 12 mm ² / s or less. The kinematic viscosity at 40 ° C. is preferably 5 mm ² / s or more, more preferably 6 mm ² / s or more, and further preferably 8 mm ² / s or more. If the kinematic viscosity at 40 ° C. of the lubricating base oil is too high, the low-temperature viscosity characteristics may be deteriorated and sufficient cooling performance may not be obtained. Conversely, if the kinematic viscosity at 40 ° C. of the lubricating base oil is too low, the formation of an oil film at the lubrication point becomes insufficient, resulting in poor lubricity and a large evaporation loss of the lubricating base oil.

(Viscosity index)
The viscosity index of the lubricating base oil used in the present invention is 100 or more in order to obtain excellent viscosity characteristics from low temperature to high temperature, and to make it difficult to evaporate even at low viscosity, preferably 120 or more, more preferably 125 or more, still more preferably 135 or more, and particularly preferably 140 or more. The upper limit of the viscosity index is not particularly limited, and those having a viscosity index of about 135 to 180, such as normal paraffin, slack wax, GTL wax, etc., or isoparaffin mineral oil obtained by isomerizing them, complex ester base oil, Those having a viscosity index of about 150 to 250 such as HVI-PAO base oil can also be used.

(Iodine number)
The iodine value of the lubricating base oil used in the present invention is preferably 1 or less, more preferably 0.5 or less, still more preferably 0.3 or less, and particularly preferably 0.15 or less. Further, the lower limit is not particularly limited and may be less than 0.01, but the iodine value of the lubricating base oil is preferably 0.001 from the viewpoint of the small effect that is commensurate with it and the economy. Above, more preferably 0.05 or more. By setting the iodine value of the lubricating base oil to 1 or less, the heat and oxidation stability can be dramatically improved, and further, the cooling performance and the insulation performance can be improved. In addition, the iodine value as used in the field of this invention means the iodine value measured by the indicator titration method of JISK0070 "the acid value of a chemical product, the saponification value, the iodine value, the hydroxyl value, and the unsaponification value."

(Manufacturing method of lubricating base oil)
As a raw material for producing a lubricating base oil suitable for the lubricating oil composition of the present invention, a raw oil containing normal paraffin can be used. The raw material oil may be either mineral oil or synthetic oil, or a mixture of two or more of these. Further, the content of normal paraffin in the raw material oil is preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and more preferably, based on the total amount of the raw material oil (100% by mass). Preferably it is 90 mass% or more, Especially preferably, it is 95 mass% or more, Most preferably, it is 97 mass% or more.

  Examples of the raw material oil containing normal paraffin include solvent extracted raffinate, partial solvent dewaxed oil, degreasing oil, distillate, reduced pressure gas oil, coker gas oil, slack wax, foots oil, Fischer-Tropsch wax, etc. Is mentioned. Of these, slack wax and Fischer-Tropsch wax are preferred.

  Slack wax is a hydrocarbon feedstock containing normal paraffins, typically obtained by solvent extraction or propane removal. Slack waxes may contain residual oil, which can be removed by deoiling. Foots oil corresponds to this deoiled slack wax. Fischer-Tropsch wax is produced by a so-called Fischer-Tropsch synthesis method.

  Moreover, the raw material oil derived from solvent extraction is obtained by sending a high-boiling petroleum fraction from atmospheric distillation to a vacuum distillation apparatus and solvent-extracting the distillation fraction from this apparatus. The residue from the vacuum distillation may be removed. In the solvent extraction method, the aromatic component is dissolved in the extraction phase while leaving more paraffinic components in the raffinate phase. Naphthene is partitioned into the extraction phase and the raffinate phase. As the solvent for solvent extraction, phenol, furfural, N-methylpyrrolidone and the like are preferably used. By controlling the solvent / oil ratio, the extraction temperature, the method of contacting the distillate to be extracted with the solvent, etc., the degree of separation between the extraction phase and the raffinate phase can be controlled. Further, a bottom fraction obtained from the fuel oil hydrocracking apparatus may be used as a raw material by using a fuel oil hydrocracking apparatus having a higher hydrocracking resolution.

Hydrocracking / releasing the above-mentioned feedstock oil so that the urea adduct value of the obtained lubricant base oil is 4% by mass or less, the kinematic viscosity at 40 ° C. is 25 mm ² / s or less, and the viscosity index is 100 or more. By performing hydroisomerization, the lubricating base oil of the present invention is obtained. The hydrocracking / hydroisomerization step is not particularly limited as long as the obtained lubricating base oil satisfies the above conditions, but the following hydrocracking / hydroisomerization step is preferably performed.

  A preferred hydrocracking / hydroisomerization step is a first step of hydrotreating a normal paraffin-containing feedstock using a hydrotreating catalyst, and a workpiece obtained by the first step. A second step of hydrodewaxing using the hydrodewaxing catalyst, and a third step of hydrotreating the workpiece obtained in the second step using the hydrorefining catalyst. In addition, you may isolate | separate and remove a predetermined component by performing distillation etc. with respect to the to-be-processed object obtained after a 3rd process as needed.

(Specific characteristics of lubricating base oil)
The lubricating base oil of the present invention obtained by the above production method is not particularly limited as long as it has the above urea adduct value, kinematic viscosity at 40 ° C., and viscosity index, but the following conditions are satisfied. It is preferable to satisfy.

  The content of the saturated component in the lubricating base oil is preferably 90% by weight or more, more preferably 93% by weight or more, even more preferably 95% by weight or more, particularly based on the total amount of the lubricating base oil (100% by weight). Preferably it is 98 mass% or more, Most preferably, it is 99 mass% or more. In addition, the ratio of the cyclic saturated component (saturated component-based naphthene component) to the saturated component is preferably 0.5% by mass or more, more preferably 0.5% by mass or more, based on the total amount of saturated component (100% by mass). Is 1% by mass or more, more preferably 2% by mass or more, and particularly preferably 5% by mass or more. The upper limit is preferably 50% by mass or less, more preferably 30% by mass or less, further preferably 20% by mass or less, particularly preferably 15% by mass or less, and most preferably 10% by mass or less.

  By satisfying the above conditions for the saturated content and the cyclic saturated content in the saturated content, excellent viscosity-temperature characteristics, thermal / oxidative stability, low-temperature viscosity characteristics, and cooling characteristics can be achieved. Moreover, it can be set as the composition excellent in the balance of cost and performance. In addition, when an additive is blended in the lubricating base oil, the additive can be sufficiently stably dissolved and held in the lubricating base oil, and the function of the additive can be improved to a higher level. Can be expressed. Furthermore, the friction characteristics of the lubricating base oil itself are improved, and as a result, an improvement in friction reduction effect and, in turn, an improvement in energy saving can be achieved.

  If the content of the saturated component in the lubricating base oil is too small, the viscosity-temperature characteristics, thermal / oxidative stability, and friction characteristics may be insufficient. In addition, if the ratio of the cyclic saturated component in the saturated component is too small, when the additive is added to the lubricating base oil, the additive becomes insufficiently soluble and is retained in the lubricating base oil. Since the effective amount of the additive decreases, the function of the additive may not be obtained effectively. On the other hand, when the ratio of the cyclic saturated component in the saturated component is too large, the effectiveness of the additive may be reduced when the additive is added to the lubricating base oil. Moreover, there exists a possibility that a low-temperature viscosity characteristic and a cooling characteristic may deteriorate. As described above, the lubricating base oil contains a predetermined amount of saturated components, and in the saturated components, a predetermined amount of cyclic saturated components (saturated basis naphthene component) and non-cyclic saturated components ( Contains saturated paraffin content). Examples of the non-cyclic saturated component include normal paraffin and isoparaffin.

  The ratio of isoparaffin in the lubricating base oil of the present invention is not particularly limited as long as the urea adduct value satisfies the above conditions, but preferably 50% by weight based on the total amount of saturated content in the lubricating base oil (100% by weight). It is 99 mass% or less, More preferably, it is 70 mass% or more and 97 mass% or less, More preferably, they are 80 mass% or more and 95 mass% or less, Most preferably, they are 90 mass% or more and 93 mass% or less. By using a lubricating base oil containing isoparaffin at such a ratio, viscosity-temperature characteristics and thermal / oxidation stability can be further improved, and both low-temperature viscosity characteristics and cooling characteristics can be achieved at a high level. It becomes. Further, when an additive is blended in this lubricating base oil, the additive can be sufficiently stably dissolved and held, and the function of the additive can be suitably expressed.

  In addition, content of the saturated part said by this invention means the value (unit: mass%) measured based on ASTMD2007-93. In addition, the ratio of the cyclic saturated component and the non-cyclic saturated component in the saturated component referred to in the present invention is a naphthene component measured in accordance with ASTM D 2786-91, respectively (measuring object: 1 ring to 6 ring naphthene, unit : Mass%) and paraffin content (unit: mass%).

  The aromatic content in the lubricating base oil is not particularly limited, but is preferably 10% by weight or less, more preferably 5% by weight or less, based on the total amount of the lubricating base oil (100% by weight). More preferably 2% by mass or less, particularly preferably 1% by mass, and most preferably 0.5% by mass or less. The aromatic content may be 0% by mass, but is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, from the viewpoint of solubility of the additive, and 0.15% by mass. % Or more is more preferable. When the aromatic content of the base oil is too large, the oxidation stability is poor.

  The aromatic content means an aromatic fraction content measured according to ASTM D2549. Usually, this aromatic fraction includes alkylbenzene, alkylnaphthalene, anthracene, phenanthrene, alkylated products thereof, compounds in which four or more benzene rings are condensed, and heterogeneous compounds such as pyridines, quinolines, phenols, and naphthols. Compounds having aromatics are included.

  The sulfur content in the lubricating base oil is not particularly limited, but is preferably 0.1% by weight or less, more preferably 0.01% by weight based on the total amount of the lubricating base oil (100% by weight). % Or less, more preferably 0.001% by mass or less, and particularly preferably 0.0005% by mass or less.

The kinematic viscosity at 100 ° C. of the lubricating base oil used in the present invention is not particularly limited, but is preferably 6.5 mm ² / s or less, more preferably 4.5 mm ² / s or less, and still more preferably 4.0 mm. ² / s or less, particularly preferably 3.0 mm ² / s or less, and most preferably 2.9 mm ² / s or less. Further, the kinematic viscosity at 100 ° C. of the lubricating base oil used in the present invention is preferably 1 mm ² / s or more, more preferably 2 mm ² / s or more, and 2.5 mm ² / s or more. More preferably. If the kinematic viscosity at 100 ° C. of the lubricating base oil is too high, the low-temperature viscosity characteristics may be deteriorated and sufficient cooling performance may not be obtained. Conversely, if the kinematic viscosity at 100 ° C. of the lubricating base oil is too low, the formation of an oil film at the lubrication point becomes insufficient, resulting in poor lubricity and an increase in evaporation loss of the lubricating base oil.

  The aniline point of the lubricating base oil used in the present invention is not particularly limited, but is preferably 150 ° C. or lower, more preferably 130 ° C. or lower, still more preferably 120 ° C. or lower, and particularly preferably 115 ° C. or lower. The aniline point of the lubricating base oil used in the present invention is preferably 80 ° C. or higher, more preferably 100 ° C. or higher, and further preferably 110 ° C. or higher. When the aniline point of the lubricating base oil is too high, the solubility of the additive is lowered, and the swelling property to the rubber agent is lowered, which causes oil leakage. If the aniline point is too low, the viscosity temperature characteristic is deteriorated and sufficient cooling performance may not be obtained.

  The pour point of the lubricating base oil depends on the viscosity grade of the lubricating base oil, but is preferably −15 ° C. or lower, more preferably −20 ° C. or lower, still more preferably −25 ° C. or lower, particularly preferably − 30 ° C. or lower. If the pour point is too high, the low temperature fluidity of the lubricating oil composition using the lubricating base oil may be reduced. In addition, the pour point as used in the field of this invention means the pour point measured based on JISK2269-1987.

The density (ρ ₁₅ ) of the lubricating base oil at 15 ° C. depends on the viscosity grade of the lubricating base oil, but is not more than the value of ρ represented by the following formula (1), that is, ρ ₁₅ ≦ ρ. Preferably there is.
ρ = 0.0025 × kv100 + 0.816 (1)
[Wherein, kv100 represents the kinematic viscosity (mm ² / s) of the lubricating base oil at 100 ° C. ]

When ρ ₁₅ > ρ, the cooling performance, the viscosity-temperature characteristics and the heat / oxidation stability, as well as the volatilization prevention, the low temperature viscosity characteristics and the low temperature fluidity tend to decrease. Moreover, when an additive is mix | blended with lubricating base oil, there exists a possibility that the effectiveness of the said additive may fall.

Specifically, the density (ρ ₁₅ ) of the lubricating base oil at 15 ° C. is preferably 0.840 or less, more preferably 0.830 or less, still more preferably 0.825 or less, and particularly preferably 0.815 or less. It is.

  In addition, the density in 15 degreeC said by this invention means the density measured in 15 degreeC based on JISK2249-1995.

(Additive)
In addition, the lubricating oil composition of the present invention can contain various additives as necessary as long as the thermal conductivity is not impaired. Such an additive is not particularly limited, and any additive conventionally used in the field of lubricating oils can be blended. Specific additives include metal detergents, ashless dispersants, antioxidants, extreme pressure agents, antiwear agents, friction modifiers, viscosity index improvers, pour point depressants, corrosion inhibitors, rust inhibitors. , 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.

  As a metal type detergent, 1 or more types chosen from a sulfonate type detergent, a salicylate type detergent, and a phenate type detergent can be blended. As these metallic detergents, any of normal salts, basic normal salts, and overbased salts with alkali metals or alkaline earth metals can be blended.

  As the ashless dispersant, any ashless dispersant used in lubricating oils can be used. For example, a mono- or mono-chain having at least one linear or branched alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule. Bisuccinimide, benzylamine having at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, polyamine having at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, or these And modified products of boron compounds, carboxylic acids, phosphoric acids, and the like. In use, one kind or two or more kinds arbitrarily selected from these can be blended.

  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.

  As the extreme pressure agent and antiwear agent, any extreme pressure agent and antiwear agent used in lubricating oils can be used. For example, sulfur-based, phosphorus-based, sulfur-phosphorus extreme pressure agents and the like can be used. Specifically, phosphites, thiophosphites, dithiophosphites, trithiophosphites Esters, phosphate esters, thiophosphate esters, dithiophosphate esters, trithiophosphate esters, amine salts thereof, metal salts thereof, derivatives thereof, dithiocarbamate, zinc dithiocarbamate, molybdenum dithiocarbamate, disulfide , Polysulfides, sulfurized olefins, sulfurized fats and oils, and the like.

  As the viscosity index improver, polymethacrylate viscosity index improver, olefin copolymer viscosity index improver, styrene-diene copolymer viscosity index improver, styrene-maleic anhydride copolymer viscosity index improver or poly Examples thereof include alkylstyrene viscosity index improvers. The weight average molecular weight of these viscosity index improvers is usually 800 to 1,000,000, preferably 100,000 to 900,000. Further, it may be a dispersion type viscosity index improver or a non-dispersion type viscosity index improver.

  As the pour point depressant, for example, a polymethacrylate polymer compatible with the lubricating base oil to be used can be used. Examples of the corrosion inhibitor include benzotriazole, tolyltriazole, thiadiazole, or imidazole compounds.

  Examples of the rust inhibitor 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, and polyoxyethylene alkyl naphthyl ether.

  Examples of metal deactivators include imidazoline, pyrimidine derivatives, alkylthiadiazoles, mercaptobenzothiazoles, benzotriazoles or derivatives thereof, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5-bis. Examples thereof include dialkyldithiocarbamate, 2- (alkyldithio) benzimidazole, and 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 0.01% by mass or more and 20% by mass or less based on the total amount of the composition (100% by mass).

(Kinematic viscosity of lubricating oil composition)
The kinematic viscosity at 40 ° C. of the lubricating oil composition of the present invention is not particularly limited, but the upper limit is preferably 30 mm ² / s or less, more preferably 25 mm ² / s or less, and still more preferably 20 mm ² / s. s or less, particularly preferably 15 mm ² / s or less. The lower limit is preferably 5 mm ² / s or more, more preferably 8 mm ² / s or more, and particularly preferably 10 mm ² / s or more. When the kinematic viscosity at 40 ° C. of the lubricating oil composition of the present invention is too small, there is a risk of causing problems in oil film retention and evaporation at the lubrication site. There is.

The kinematic viscosity at 100 ° C. of the lubricating oil composition of the present invention is not particularly limited, but the upper limit is preferably 7.0 mm ² / s or less, more preferably 5.0 mm ² / s or less, and still more preferably Is 4.0 mm ² / s or less, particularly preferably 3.5 mm ² / s or less, and most preferably 3.1 mm ² / s or less. Moreover, as a lower limit, Preferably it is 1.5 mm < ² > / s or more, More preferably, it is 2.0 mm < ² > / s or more, Most preferably, it is 2.5 mm < ² > / s or more. If the kinematic viscosity at 100 ° C. is too small, there is a risk of problems in oil film retention and evaporability at the lubrication site, and conversely, if too large, there is a risk of insufficient cooling.

(Heat transfer coefficient of lubricating oil composition)
The lower limit of the heat transfer coefficient of the lubricating oil composition of the present invention although 720W / ^{m 2} · ℃ or more, more preferably 740W / ^{m 2} · ℃ or more, more preferably 750W / ^{m 2} · ℃ or more, Particularly preferably, it is 760 W / m ² · ° C. or higher. There is no particular limitation on the upper limit of the heat transfer coefficient, preferably 1000W / ^{m 2} · ℃ or less, more preferably 900W / ^{m 2} · ℃, particularly preferably not more than 800W / ^{m 2} · ℃. If the heat transfer coefficient is too small, the cooling property of the transmission lubricating oil composition will be insufficient, and if the heat transfer coefficient is too large, there may be a problem in the oil film retention and lubricity of the lubrication site.

  Hereinafter, the contents of the present invention will be described more specifically with reference to Examples and Comparative Examples.

(Examples 1-2, Comparative Examples 1-2)
Using the base oil shown in Table 1, the lubricating oil compositions of the present invention (Examples 1 and 2) and comparative lubricating oil compositions (Comparative Examples 1 and 2) having the compositions shown in Table 2 were prepared. About the obtained composition, kinematic viscosity (40 degreeC, 100 degreeC) and a heat transfer coefficient were measured, and the result was written together in Table 2. As the additive, 3% by mass of an additive package for transmission oil containing an antiwear agent, a friction modifier, an antioxidant and the like was uniformly added.

The contents of the base oil shown in Table 1 are as follows.
Base oil 1: mineral base oil obtained by hydrocracking / hydroisomerization of n-paraffin-containing oil 2: mineral oil base oil obtained by hydrocracking / hydroisomerization of n-paraffin-containing oil 3: solvent refined mineral oil base oil 4 : Hydrocracked mineral oil

(Measurement of heat transfer coefficient)
Using the apparatus of FIG. 1, the heat between the lubricating oil and the cooling water when the heater heat amount (250 W), the cooling water flow rate (1000 ml / min) and the stirring speed (300 rpm) are constant and the sample oil temperature reaches equilibrium. The transfer coefficient was obtained by the following equation.
_{h = q / A (T h} -T c)
Here, h: heat transfer coefficient, q: the heat movement amount, _{T h:} lubricating oil temperature, _{T c:} the coolant temperature, A: a heat exchange area.

  It turned out that the composition of the Example whose urea adduct value of a base oil is 4 mass% or less has a large heat transfer coefficient compared with the composition of a comparative example.

  While the present invention has been described in connection with embodiments that are presently the most practical and preferred, the present invention is not limited to the embodiments disclosed herein. Rather, the transmission oil composition for automobiles and the transmission oil composition for hybrid vehicles can be changed as appropriate without departing from the spirit or concept of the invention that can be read from the claims and the entire specification. It should be understood as being included within the scope of the present invention.

It is a conceptual diagram of the apparatus used for the measurement of a heat transfer coefficient.

Claims (5)

The urea adduct value is 4 mass% or less, the kinematic viscosity at 40 ° C. is 5 mm ² / s to 25 mm ² / s, and the kinematic viscosity at 100 ° C. is 1 mm ² / s to 6.5 mm ² / s. , The viscosity index is 100 or more, the content of saturated component is 90% by mass or more, the proportion of naphthene in the saturated component is 50% by mass or less based on the total amount of saturated component, and the aniline point is 80 ° C. or more. A lubricating base oil that is
Metal detergent, ashless dispersant, antioxidant, extreme pressure agent, antiwear agent, friction modifier, viscosity index improver, pour point depressant, corrosion inhibitor, rust inhibitor, demulsifier, metal deactivation One or more additives selected from an agent and an antifoaming agent, containing 0.01% by mass or more and 20% by mass or less based on the total amount of the transmission oil composition for automobiles,
The kinematic viscosity at 40 ° C. is 5 mm ² / s to 30 mm ² / s,
The kinematic viscosity at 100 ° C. is 1.5 mm ² / s to 7.0 mm ² / s,
A transmission oil composition for automobiles having a heat transfer coefficient of 720 W / m ² · ° C to 1000 W / m ² · ° C.

The heat transfer coefficient is
A container containing sample oil for measuring the heat transfer coefficient;
A heater for heating the sample oil in the container;
A stir bar for stirring the sample oil in the container;
A cooling pipe which is disposed so as to come into contact with the sample oil in the container, both end portions are disposed outside the container, and in which cooling water flows;
A quantity of heat having a temperature of the sample oil in the container, a temperature before flowing into the container of the cooling water, and a thermocouple arranged to measure the temperature after flowing out of the container of the cooling water Using a measuring device
The temperature of the sample oil in the container is made to reach equilibrium by keeping the heat amount generated by the heater 250 W, the flow rate of the cooling water at 1000 mL / min, and the stirring speed of the stirrer at 300 rpm, respectively.
The temperature T _h (° C.) of the sample oil in the container at the time of equilibrium, the temperature T _c (° C.) of the cooling water, the amount of heat q (W) transferred from the sample oil in the container to the cooling water, And the heat exchange area A (m ² ), the following formula (1):
_{h = q / A (T h} -T c) (1)
A value h (W / m ² · ° C.) obtained by the method of calculating by
In the formula (1), the value of A is
Solvent refined mineral oil, kinematic viscosity at 40 ° C. 22.77 mm ² / s, kinematic viscosity at 100 ° C. 4.413 mm ² / s, viscosity index 103, density 0.8637 g / cm ^{3 at} 15 ° C., pour point −15 ° C., aniline point 98.5 ° C., iodine value 3.82 , saturated content 74.9% by mass, aromatic content 24.9% by mass, saturated standard paraffin content 25.7% by mass, saturated standard 97% by mass of a base oil having a naphthene content of 74.3% by mass and a urea adduct value of 6.7% by mass,
The value measured by the above method of the heat transfer coefficient h with respect to the reference oil comprising 3% by mass of the transmission oil additive package described in Comparative Example 1 is 620 W / m ² · ° C.   The transmission oil composition for automobiles according to claim 1, wherein the iodine value of the lubricating base oil is 1 or less. The transmission oil composition for automobiles according to claim 1 or 2, wherein a density of the lubricating base oil at 15 ° C is equal to or less than a value of ρ represented by the following formula (1).
ρ = 0.0025 × kv100 + 0.816 (1)
[In the formula (1), kv100 represents the kinematic viscosity of the lubricating base oil in mm ² / s at 100 ° C. ] The transmission oil composition for automobiles according to any one of claims 1 to 3, which is used for a transmission for a hybrid vehicle. The transmission oil composition for automobiles according to any one of claims 1 to 4, which is a combined oil for transmission and electric motor in an electric vehicle or a hybrid vehicle.