JP2024013504A - lubricating oil composition - Google Patents

Abstract

To provide a lubricating oil composition capable of having a good balance of insulation, oxidation stability and extreme pressure property at a high level and also having high copper corrosion prevention properties.SOLUTION: There is provided a lubricating oil composition which comprises (A) a lubricating oil base oil, (B) an extreme pressure agent and (C) a nitrogen-containing ashless dispersant, wherein the component (B) includes a specific phosphorus-based extreme pressure agent (B1) and does not include a sulfur-containing extreme pressure agent (B2) or includes the component (B2) so as to satisfy a specific condition, the mass ratio of phosphorus derived from the component (B1) to nitrogen derived from the component (C) and the mass ratio of sulfur derived from the component (B2) to phosphorus derived from the component (B1) satisfy specified conditions respectively and the ratio of the kinematic viscosity of the lubricating oil composition at 40°C before and after performing a specific oxidation treatment is a specific value or less.SELECTED DRAWING: None

Description

TECHNICAL FIELD This invention relates to lubricating oil compositions.

In recent years, electric vehicles that do not emit carbon dioxide, a greenhouse gas, have been attracting attention. Such electric vehicles usually use an electric motor as a driving power source and are equipped with a gear mechanism such as a transmission. Conventionally, different lubricating oil compositions have been used to cool and lubricate electric motors and gear mechanisms, but in recent years, in order to simplify the circulation mechanism of lubricating oil compositions, the same lubricating oil composition has been used. The use of lubricating oil compositions has been proposed. In particular, when an electric vehicle has a structure in which an electric motor and a transmission are integrated, it is required to use the same lubricating oil composition to lubricate the electric motor and the transmission. Under these circumstances, research into various lubricating oil compositions for electric vehicles has been progressing.

For example, JP 2019-137829 A (Patent Document 1) describes (A) a lubricating base oil, (B1) a phosphite having at least one alkyl group having 4 to 10 carbon atoms or an amine salt thereof, A lubricating oil composition comprising (C) a boric acid ester, (D) a sulfur-based extreme pressure agent, and (E) an organic friction modifier, the lubricating oil composition having a kinematic viscosity of 1.5 at 100°C. ~5 mm ² /s, a phosphorus content of 310 to 1000 ppm, a boron content of 50 to 400 ppm, and a sulfur content of 250 to 1000 ppm based on the mass of the lubricating oil composition. Compositions are disclosed.

In addition, JP 2020-066673 A (Patent Document 2) describes base oil (A), neutral phosphorus compound (B), acidic phosphorus compound (C), sulfur compound (D), and metal A lubricating oil composition containing a metal salt (E) selected from sulfonates, metal salicylates, and metal phenates, wherein the content of the acidic phosphorus compound (C) in terms of phosphorus atoms is the total amount of the lubricating oil composition. The content of the sulfur-based compound (D) in terms of sulfur atoms is 10 to 1000 ppm by mass based on the total amount of the lubricating oil composition, and the metal atom of the metal salt (E) A lubricating oil composition is disclosed in which the content in terms of conversion is 5 to 180 mass ppm based on the total amount of the lubricating oil composition.

Furthermore, in JP 2021-066809 (Patent Document 3), (A) lubricating oil base oil, (B) metal detergent, specific (C) phosphorus-based extreme pressure agent, (D) sulfur-based extreme pressure (E) a specific ashless dispersant, and (F) a viscosity index improver having a weight average molecular weight (Mw) of 10,000 to 100,000, the lubricating oil composition having a kinematic viscosity of 10 mm at 40°C. Lubricating oil compositions are disclosed that range from more than ² /s to 20 mm ² /s and have a boron content of 25 to 150 ppm by mass.

JP 2019-137829 Publication JP2020-066673A Japanese Patent Application Publication No. 2021-066809

However, the lubrication of electric motors and transmissions in electric vehicles requires high insulation properties, high oxidation stability, and high extreme pressure properties (seizure resistance (load capacity) and anti-wear properties (wear resistance)). However, conventional lubricating oil compositions such as those described in Patent Documents 1 to 3 do not have the properties of insulation, oxidation stability, and extreme pressure properties. It was not necessarily sufficient in terms of making it sophisticated. Furthermore, in recent years, in order to obtain higher motor output, electric motors are required to be used at higher voltages, and gears and bearings are also required to be used under harsher conditions. It is desired to develop a lubricating oil composition that has a high level of well-balanced properties and extreme pressure properties. Furthermore, since copper is used as a material in electric motors, the lubricating oil composition used for lubrication and cooling thereof is also required to have high corrosion prevention properties against copper (copper corrosion prevention properties).

The present invention has been made in view of the above-mentioned problems of the prior art, and makes it possible to have insulation properties, oxidation stability, and extreme pressure properties at a high level and in a well-balanced manner, as well as to have a high degree of copper corrosion prevention property. The object of the present invention is to provide a lubricating oil composition.

As a result of extensive research to achieve the above object, the present inventors have discovered a lubricating oil composition containing (A) a lubricating base oil, (B) an extreme pressure agent, and (C) a nitrogen-containing ashless dispersant. Component (B) is said to contain (B1) a phosphorus-based extreme pressure agent that is at least one compound selected from the group consisting of phosphoric acid, phosphoric acid ester, phosphite ester, and salts thereof. and (B2) does not contain a sulfur-containing extreme pressure agent, or the content of sulfur derived from the component (B2) is 0.01% by mass or less based on the total amount of the lubricating oil composition. The condition of containing the component (B2) as follows; the mass ratio of phosphorus derived from the component (B1) to nitrogen derived from the component (C) ([phosphorus]/[nitrogen]) is 0.60 or more and 2.30 or less; the mass ratio ([sulfur]/[phosphorus]) of sulfur derived from the component (B2) and phosphorus derived from the component (B1) is 3.0 or less; The kinematic viscosity at 40°C ( _KV40OL ) of the lubricating oil composition after oxidation treatment at an oil temperature of 165°C for 192 hours by the ISOT method in accordance with JIS K2514-1:2013 and the oxidation treatment. By setting the ratio ([KV40 _OL ]/[KV40 _L ]) to the kinematic viscosity (KV40 _L ) at 40°C of the previous lubricating oil composition to 1.06 or less, the resulting lubricating oil composition has insulation properties. They discovered that it is possible to have a high level of oxidation stability and extreme pressure resistance in a well-balanced manner, and also to have a high degree of copper corrosion prevention, and have completed the present invention. reached.

That is, the present invention provides the following aspects.

[1] (A) Lubricating base oil,
(B) an extreme pressure agent, and
(C) nitrogen-containing ashless dispersant;
A lubricating oil composition comprising:
The component (B) is
(B1) contains a phosphorus-based extreme pressure agent that is at least one compound selected from the group consisting of phosphoric acid, phosphoric acid ester, phosphite ester, and salts thereof, and
(B2) Does not contain a sulfur-containing extreme pressure agent, or contains the ( B2) Contains the component,
The mass ratio of phosphorus derived from the component (B1) to nitrogen derived from the component (C) ([phosphorus]/[nitrogen]) is 0.60 or more and 2.30 or less,
The mass ratio of sulfur derived from the component (B2) to phosphorus derived from the component (B1) ([sulfur]/[phosphorus]) is 3.0 or less,
The kinematic viscosity at 40°C (KV40OL) of the lubricating oil composition after oxidation treatment at an oil temperature of 165°C for 192 hours by the ISOT method according to JIS K2514-1, and the kinematic viscosity ( _KV40OL ) of the lubricating oil composition before the oxidation treatment The ratio ([ _KV40OL ]/[ _KV40L ]) of the lubricating oil composition to the kinematic viscosity ( _KV40L ) at 40°C is 1.06 or less;
A lubricating oil composition characterized by:

[2] The kinematic viscosity at 40°C of the lubricating base oil without the oxidation treatment (KV40 _B ) and the kinematic viscosity at 40°C of the lubricating composition before the oxidation treatment (KV40 _L ) The lubricating oil composition according to [1], wherein the ratio ([KV40 _L ]/[KV40 _B ]) is 0.95 or more and 1.15 or less.

[3] The lubricating base oil contains at least one selected from the group consisting of hydrotreated base oils and wax isomerized base oils, and the lubricating base oil has a kinematic viscosity of 20 mm ² at 40°C. /s or less, the lubricating oil composition according to [1] or [2].

[4] (D) Any one of [1] to [3] containing a calcium sulfonate detergent such that the calcium content is 200 mass ppm or less based on the total amount of the lubricating oil composition. The lubricating oil composition according to item 1.

[5] The lubricating oil composition according to any one of [1] to [4], which is a composition for lubricating a transmission and for cooling and lubricating an electric motor.

According to the present invention, it is possible to provide a lubricating oil composition that has a high level of insulation, oxidation stability, and extreme pressure property in a well-balanced manner, and also has high copper corrosion prevention properties.

Hereinafter, the present invention will be explained in detail based on its preferred embodiments. In this specification, unless otherwise specified, the notation "X to Y" for numerical values X and Y means "more than or equal to X and less than or equal to Y." In such a notation, if a unit is attached only to the numerical value Y, the unit shall also be applied to the numerical value X.

The lubricating oil composition of the present invention includes:
(A) Lubricant base oil,
(B) an extreme pressure agent, and
(C) nitrogen-containing ashless dispersant;
A lubricating oil composition comprising:
The component (B) is
(B1) contains a phosphorus-based extreme pressure agent that is at least one compound selected from the group consisting of phosphoric acid, phosphoric acid ester, phosphite ester, and salts thereof, and
(B2) Does not contain a sulfur-containing extreme pressure agent, or contains the ( B2) Contains the component,
The mass ratio of phosphorus derived from the component (B1) to nitrogen derived from the component (C) ([phosphorus]/[nitrogen]) is 0.60 or more and 2.30 or less,
The mass ratio of sulfur derived from the component (B2) to phosphorus derived from the component (B1) ([sulfur]/[phosphorus]) is 3.0 or less,
The kinematic viscosity at 40°C (KV40OL) of the lubricating oil composition after oxidation treatment at an oil temperature of 165°C for 192 hours by the ISOT method according to JIS K2514-1, and the kinematic viscosity ( _KV40OL ) of the lubricating oil composition before the oxidation treatment The ratio ([ _KV40OL ]/[ _KV40L ]) of the lubricating oil composition to the kinematic viscosity ( _KV40L ) at 40°C is 1.06 or less;
It is characterized by:

[Component (A): Lubricating base oil]
The lubricating oil composition of the present invention contains a lubricating base oil as component (A). The lubricant base oil used as such component (A) is not particularly limited, and any known lubricant base oil (mineral oil base oil, synthetic base oil, or mixed base oil thereof, etc.) may be used. For example, the lubricant base oil described in International Publication No. 2020/095968 can be used as appropriate. The lubricating base oil used as component (A) may be composed of one type of base oil, or may be a mixed base oil containing two or more types of base oil.

In addition, the lubricant base oils used as component (A) include Group II base oils, Group III base oils, Group IV base oils, and Group V base oils according to the classification of base oils by API (American Petroleum Institute). At least one selected from base oils can be suitably used, and among them, it is possible to obtain a composition with higher oxidation stability, corrosion resistance, and insulation (volume resistivity), and Group II base oil or Group III base oil is more preferable from the viewpoint of making it possible to improve the low electricity consumption of electric vehicles. ).

Furthermore, as the lubricating base oil used as component (A), mineral oil base oils are preferred. Such mineral base oils include solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and lubricating oil fractions obtained by atmospheric distillation and vacuum distillation of crude oil. Preferred examples include paraffinic or naphthenic mineral base oils obtained by applying one or more refining methods, such as hydrorefining, sulfuric acid washing, and clay treatment, in an appropriate combination. . In addition, among such mineral base oils, it is possible to obtain compositions with higher oxidation stability, corrosion resistance, and insulation (volume resistivity), as well as lower electricity costs for electric vehicles. From the viewpoint of being able to improve properties, hydrorefined base oils and wax isomerized base oils are particularly preferred as component (A). Note that these mineral oil base oils may be used alone or in combination of two or more in any proportion.

Furthermore, the kinematic viscosity at 40°C of the lubricating base oil (in the case of a mixed base oil containing two or more base oils, the mixed base oil) used as component (A) is 20 mm ² /s or less. The speed is preferably 5 to 18 mm ² /s, more preferably 8 to 12 mm ² /s. By setting the kinematic viscosity of the lubricant base oil at 40°C to the above upper limit value or less, higher performance (effect) can be obtained in terms of low temperature viscosity characteristics and fuel efficiency performance compared to the case where the kinematic viscosity at 40 ° C. exceeds the above upper limit value. becomes possible. In addition, by setting the kinematic viscosity of the lubricant base oil at 40°C to or above the lower limit value, the oil film formation performance at the lubricated area is higher than when it is less than the lower limit value, improving seizure resistance and wear prevention. This makes it possible to further improve the extreme pressure properties based on properties, and it also becomes possible to further improve the electrical insulation properties of the new oil. In this specification, the kinematic viscosity of the base oil or composition at 40°C or 100°C means the kinematic viscosity at each temperature (40°C or 100°C) specified in JIS K 2283-2000.

Furthermore, the kinematic viscosity at 100°C of the lubricating base oil (in the case of a mixed base oil containing two or more base oils, the mixed base oil) used as component (A) is 2.0 to 4. The speed is preferably .0 mm ² /s, and more preferably 2.0 to 2.7 mm ² /s. By setting the kinematic viscosity of the lubricant base oil at 100°C to below the above upper limit, higher performance (effect) can be obtained in terms of low temperature viscosity characteristics and fuel efficiency performance compared to the case where it exceeds the above upper limit. becomes possible. In addition, by setting the kinematic viscosity of the lubricating base oil at 100°C to or above the lower limit value, the oil film formation performance at the lubricated area is higher than when it is less than the lower limit value, improving seizure resistance and wear prevention. This makes it possible to further improve the extreme pressure properties based on properties, and furthermore, it becomes possible to further improve the electrical insulation properties of the new oil.

Further, the viscosity index of the lubricating base oil (in the case of a mixed base oil containing two or more base oils, the mixed base oil) used as component (A) is preferably 95 or more, More preferably, it is 120 or more. By setting the viscosity index of the lubricating base oil to the above-mentioned lower limit value or more, it is possible to improve the viscosity-temperature characteristics and thermal/oxidative stability of the lubricating oil composition, and further reduce the coefficient of friction. It becomes possible to further improve wear resistance. In addition, the viscosity index of component (A) is preferably 120 to 160, since higher effects can be obtained from the viewpoint of fuel saving performance. In this specification, the "viscosity index" of a base oil or a composition means a viscosity index measured in accordance with JIS K 2283-2000.

In addition, the sulfur content of the lubricating base oil (in the case of a mixed base oil containing two or more base oils, the mixed base oil) used as component (A) is 10 mass ppm or less (more preferably is preferably 8 mass ppm or less, more preferably 5 mass ppm or less, particularly preferably 4 mass ppm or less. When the sulfur content is below the upper limit, the oxidation stability can be further improved compared to when the sulfur content exceeds the upper limit.

Furthermore, the pour point of the lubricating base oil (in the case of a mixed base oil containing two or more base oils, the mixed base oil) used as component (A) is not particularly limited; , -12°C or lower. When such a pour point is below the above-mentioned upper limit, it becomes possible to further improve the low-temperature fluidity of the lubricating oil composition finally obtained, compared to when it exceeds the above-mentioned upper limit. Further, such a pour point is more preferably −22° C. or lower from the viewpoint of making it possible to increase the viscosity index. In this specification, "pour point" means a pour point measured in accordance with JIS K 2269-1987.

Furthermore, the flash point of the lubricating base oil (in the case of a mixed base oil containing two or more base oils, the mixed base oil) used as component (A) is 160°C or higher (more preferably 190°C or higher). ℃ or higher) is preferable. Further, by setting the flash point to the above-mentioned lower limit or higher, safety during high-temperature use tends to be more improved than when the flash point is below the above-mentioned lower limit. In this specification, "flash point" means a flash point measured in accordance with JIS K 2265-4-2007 (Cleveland Open Method).

[Component (B): extreme pressure agent]
The lubricating oil composition of the present invention contains an extreme pressure agent as component (B). The extreme pressure agent used as such component (B) is
(B1) contains a phosphorus-based extreme pressure agent that is at least one compound selected from the group consisting of phosphoric acid, phosphoric acid ester, phosphite ester, and salts thereof, and
(B2) Does not contain a sulfur-containing extreme pressure agent, or contains the ( It contains component B2). That is, the extreme pressure agent as component (B) is
A condition that the component (B1) is contained; and
The (B2) component does not contain the component (B2), or the content of sulfur derived from the component (B2) is 0.01% by mass or less based on the total amount of the lubricating oil composition. The condition that it contains;
It satisfies both of the following.

As described above, the component (B) contains the component (B1) as an essential component, but by using the component (B1), the sulfur-containing extreme pressure agent (component (B2)) can be omitted or Even if the amount of sulfur-containing extreme pressure agent (component (B2)) used is minute (an amount such that the amount of sulfur is 0.01% by mass or less based on the total amount of the lubricating oil composition), a high degree of load resistance can be achieved. It becomes possible to exhibit high performance and wear resistance, and it also becomes possible to improve insulation properties more efficiently.

The phosphorus-based extreme pressure agent used as the component (B1) is at least one compound selected from the group consisting of phosphoric acid, phosphoric acid esters, phosphite esters, and salts thereof. Note that the term "phosphorus-based extreme pressure agent" as used herein excludes phosphorus-based extreme pressure agents that contain sulfur atoms (so-called "sulfur-phosphorus extreme pressure agents"). The phosphorus-based extreme pressure agent contained corresponds to the sulfur-containing extreme pressure agent described below).

The phosphoric acid ester that can be used as the component (B1) is not particularly limited, and any known phosphoric acid ester that can be used as an extreme pressure agent can be used as appropriate. It should be noted that the term "phosphoric acid ester" as used herein is a concept that includes acidic phosphoric acid ester. That is, such phosphoric acid esters include, for example, tributyl phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, trioctyl phosphate, trinonyl phosphate, tridecyl phosphate, triundecyl phosphate, tridodecyl phosphate, and tritriphosphate. Decyl phosphate, tritetradecyl phosphate, tripentadecyl phosphate, trihexadecyl phosphate, triheptadecyl phosphate, triotadecyl phosphate, trioleyl phosphate, triphenyl phosphate, tricresyl phosphate, tricylenyl phosphate, cresyl diphenyl phosphate, In addition to xylenyl diphenyl phosphate, so-called acidic phosphate esters (e.g. monobutyl acid phosphate, monopentyl acid phosphate, monohexyl acid phosphate, monoheptyl acid phosphate, monooctyl acid phosphate, monononyl acid phosphate, monodecyl acid phosphate) , monoundecyl acid phosphate, monododecyl acid phosphate, monotridecyl acid phosphate, monotetradecyl acid phosphate, monopentadecyl acid phosphate, monohexadecyl acid phosphate, monoheptadecyl acid phosphate, monooctadecyl acid phosphate, monooleyl acid Monoalkyl acid phosphate such as phosphate, dibutyl acid phosphate, dipentyl acid phosphate, dihexyl acid phosphate, diheptyl acid phosphate, dioctyl acid phosphate, dinonyl acid phosphate, didecyl acid phosphate, diundecyl acid phosphate, didodecyl acid phosphate, ditri Examples include dialkyl acid phosphates such as decyl acid phosphate, ditetradecyl acid phosphate, dipentadecyl acid phosphate, dihexadecyl acid phosphate, diheptadecyl acid phosphate, dioctadecyl acid phosphate, and dioleyl acid phosphate.

Furthermore, the phosphorous acid ester that can be used as the component (B1) is not particularly limited, and any known ones that can be used as extreme pressure agents can be used as appropriate, such as dibutyl phosphite, dipentyl phosphite, dihexyl phosphite, etc. , diheptyl phosphite, dioctyl phosphite, dinonyl phosphite, didecyl phosphite, diundecyl phosphite, didodecyl phosphite, dioleyl phosphite, diphenyl phosphite, dicresyl phosphite, tributyl phosphite, tripentyl Phosphite, trihexyl phosphite, triheptyl phosphite, trioctyl phosphite, trinonyl phosphite, tridecyl phosphite, triundecyl phosphite, tridodecyl phosphite, trioleylphosphite, triphenyl phosphite, tri cresyl phosphite, monolauryl hydrogen phosphite, monooleyl hydrogen phosphite, monostearyl hydrogen phosphite, monophenyl hydrogen phosphite, dibutyl hydrogen phosphite, dihexyl hydrogen phosphite, diheptyl hydrogen phosphite, di-n - Octyl hydrogen phosphite, diethylhexyl hydrogen phosphite, etc. Among these phosphites, dialkyl hydrogen phosphites having two alkyl groups are preferred from the viewpoint of improving seizure resistance and wear resistance, and dialkyl hydrogen phosphites having two alkyl groups having 4 to 12 carbon atoms are preferred. More preferred are dialkyl hydrogen phosphites.

In addition, as the phosphoric acid salt, phosphoric ester salt, and phosphite salt that can be used in the component (B1), known salts that can be used as extreme pressure agents can be used as appropriate, and there are no particular restrictions, but For example, phosphoric acid, phosphoric acid ester, or phosphite; metal base, or ammonia, a hydrocarbon group having 1 to 8 carbon atoms, or an amine containing only a hydroxy group-containing hydrocarbon group in the molecule. Examples include salts in which part or all of the remaining acidic hydrogen is neutralized by the action of a nitrogen-containing compound such as a nitrogen-containing compound.

Further, the phosphorus-based extreme pressure agent (component (B1)) preferably contains (B1-1) an alkylamine salt of phosphoric acid ester. Such component (B1-1) is not particularly limited, and known alkylamine salts of phosphoric acid esters that can be used as extreme pressure agents can be used as appropriate. Such alkylamine salts of phosphoric acid esters include salts obtained by neutralizing some or all of the remaining acidic hydrogen by reacting phosphoric acid esters with an amine compound having an alkyl group in the molecule (phosphoric acid esters). and the above-mentioned amine compound (reactant)) can be suitably used.

In addition, as the phosphoric ester used to form such a component (B1-1), the aforementioned phosphoric esters can be used as appropriate, and there are no particular limitations, but among them, acidic phosphoric esters can be used. Preferably, monoalkyl acid phosphates and/or dialkyl acid phosphates are more preferable.

Such monoalkyl acid phosphates and dialkyl acid phosphates include the following formula (1):

[In formula (1), R ^a is a hydrocarbon group (more preferably an alkyl group) having 2 to 22 carbon atoms (more preferably 8 to 18 carbon atoms), and n is an integer of 1 or 2. ]
It is preferable that it is a compound represented by That is, as the phosphoric acid ester used to form the component (B1-1), it is preferable to use a compound represented by the formula (1).

Further, as the amine compound used to form the alkylamine salt of phosphoric acid ester, monoalkylamine, dialkylamine, and trialkylamine can be suitably used. Examples of such amine compounds include methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, and tetradecylamine. , pentadecylamine, hexadecylamine, heptadecylamine, octadecylamine, oleylamine, tetracosylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine , diundecylamine, didodecylamine, ditridecylamine, ditetradecylamine, dipentadecylamine, dihexadecylamine, diheptadecylamine, dioctadecylamine, dioleylamine, ditetracosylamine, trimethylamine, triethylamine, tri- Propylamine, tributylamine, tripentylamine, trihexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, triundecylamine, tridodecylamine, tritridecylamine, tritetradecylamine, tripenta Examples include decylamine, trihexadecylamine, triheptadecylamine, triotadecylamine, trioleylamine, and tritetracosylamine. Such amine compounds may be used alone or in combination of two or more. As such an amine compound, the following formula (2):

[In formula (2), R ^b , R ^c and R ^d are each independently a hydrogen atom or a monovalent alkyl group (provided that at least one of R ^b , R ^c and R ^d is a monovalent alkyl group) ). ]
It is preferable that it is a compound represented by In addition, the monovalent alkyl groups that can be selected as R ^b , R ^c and R ^d in the formula (2) may be linear or branched. Further, the number of carbon atoms in such a monovalent alkyl group is not particularly limited, but may be 1 or more, 3 or more, 5 or more, 7 or more, 9 or more, or 11 or more, and 20 or less, 18 or less, 16 or less. , or 14 or less. In addition, the compound represented by such formula (2) is a monoalkylamine (one of R ^b , R ^c and R ^d in formula (2) is a monovalent alkyl group (particularly preferably a carbon and/or dialkylamine (2 of R ^b , R ^c and R ^d in formula (2)); is a monovalent alkyl group (particularly preferably an alkyl group having 8 to 18 carbon atoms), and the others are hydrogen atoms).

In addition, as the component (B1-1), the compound represented by the formula (1) and the A salt with a compound represented by formula (2) is preferable. Further, the component (B1-1) can be used alone or in combination of two or more.

In addition, the phosphorus-based extreme pressure agent (component (B1)) includes:
The (B1-1) component and
Components other than the (B1-1) component (hereinafter referred to as "(B1 -2) ingredients);
A mixture of is more preferred. The above-mentioned (B1-2) component to be included in such a mixture is from the viewpoint that it is possible to more easily achieve excellent seizure resistance, wear resistance, corrosion resistance, and oxidation stability at the same time. Among them, phosphorous acid esters are more preferable. That is, as the component (B1), it is preferable to use a mixture of (B1-1) an alkylamine salt of a phosphoric acid ester and a phosphorous acid ester.

Further, when the component (B1) is a mixture of the component (B1-1) and the component (B1-2), the phosphorus derived from the component (B1-1) and the component (B1-2) The mass ratio of phosphorus derived from the component ([P derived from the (B1-1) component]/[P derived from the (B1-2) component]) is 0.4 to 2.5 (more preferably 0.4 to 2.5). 2.0) is preferable. When the mass ratio of phosphorus is at least the above-mentioned lower limit, it is possible to obtain a higher effect in terms of anti-seizure performance than when it is below the above-mentioned lower limit, and on the other hand, when it is below the above-mentioned upper limit, In this case, it is possible to obtain even higher effects in terms of electrical insulation than in the case where the above upper limit is exceeded.

In addition, the component (B) does not contain (B2) a sulfur-containing extreme pressure agent, or the content of sulfur derived from the component (B2) is 0.01 mass by mass based on the total amount of the lubricating oil composition. % (100 mass ppm) or less of the component (B2).

Here, when the component (B) contains the sulfur-containing extreme pressure agent (component (B2)), the sulfur-containing extreme pressure agent is not particularly limited, and any known extreme pressure agent containing sulfur can be used. Can be used as appropriate. Such sulfur-containing extreme pressure agents include, for example, sulfur-based extreme pressure agents such as dithiocarbamate, zinc dithiocarbamate, molybdenum dithiocarbamate (MoDTC), disulfide, polysulfide, sulfurized olefin, and sulfurized oil; thiophosphite ester. (thiophosphites), dithiophosphites (dithiophosphites), trithiophosphites (trithiophosphites), thiophosphates (thiophosphates), dithiophosphates (dithiophosphates), trithiophosphates Examples include sulfur-phosphorus extreme pressure agents such as acid esters (trithiophosphate), amine salts thereof, and derivatives thereof.

When the component (B) contains the sulfur-containing extreme pressure agent (component (B2)), the content of sulfur derived from the component (B2) is 0.01% based on the total amount of the lubricating oil composition. % (100 mass ppm) or less (more preferably 80 mass ppm or less, still more preferably 60 mass ppm or less, particularly preferably 50 mass ppm or less, most preferably 20 mass ppm or less). When the content of such component (B2) is below the upper limit, it is possible to obtain higher oxidation stability and higher copper corrosion prevention than when the content exceeds the upper limit. Become. In addition, from the viewpoint of further improving copper corrosion prevention properties and insulation properties (value of volume resistivity), it is preferable that the component (B) does not contain the sulfur-containing extreme pressure agent (B2).

Moreover, the method for producing such component (B) is not particularly limited, and any known method can be used as appropriate. Moreover, as such component (B), a commercially available product may be used.

[Component (C): Nitrogen-containing ashless dispersant]
The lubricating oil composition of the present invention contains a nitrogen-containing ashless dispersant (nitrogen-containing ashless dispersant) as component (C).

Component (C) is not particularly limited, and any known nitrogen-containing ashless dispersant can be used as appropriate. Further, from the viewpoint of further improving corrosion resistance and oxidation stability, the component (C) is preferably an ashless dispersant having a nitrogen-containing functional group as a dispersion group.

Examples of the ashless dispersant having a nitrogen-containing functional group as a dispersing group include succinimide, benzylamine, and polyamine having a hydrocarbon group having 40 to 400 carbon atoms (e.g., alkyl group, alkenyl group). , these derivatives, etc. can be exemplified as suitable examples.

In addition, the component (C) is not particularly limited, but from the viewpoint of further improving corrosion resistance and oxidation stability, the component (C) may contain a hydrocarbon group having 40 to 400 carbon atoms (for example, an alkyl group or an alkenyl group). More preferably, it is at least one succinimide-based ashless dispersant selected from the group consisting of succinimide and derivatives of succinimide (modified compounds of succinimide).

In addition, the succinimide having a hydrocarbon group having 40 to 400 carbon atoms is not particularly limited, but includes the following formulas (3) and (4):

[In formulas (3) and (4), R ¹ and R ² are each independently an alkyl group having 40 to 400 carbon atoms (more preferably 60 to 350 carbon atoms) or an alkyl group having 40 to 400 carbon atoms (more preferably 60 to 350 carbon atoms) 350), and n represents an integer of 0 to 5. ]
It is preferable that it is a compound represented by In addition, in such formulas (3) and (4), the alkyl group or alkenyl group that can be selected as R ¹ and the alkyl group or alkenyl group that can be selected as R ² are both called polyisobutylene. More preferably, it is a branched alkyl group or alkenyl group (polyisobutenyl group) derived from an isobutene oligomer, or a polybutenyl group. Furthermore, the alkyl group or alkenyl group that can be selected as R ¹ and R ² preferably has a weight average molecular weight of 800 to 1,500 (more preferably 950 to 1,400). Further, n in formula (3) is preferably an integer of 1 to 5 (more preferably 2 to 4). On the other hand, n in formula (4) is preferably an integer of 0 to 4 (more preferably 1 to 4, still more preferably 1 to 3). Furthermore, among the compounds represented by formulas (3) to (4), from the viewpoint of further improving corrosion resistance performance and oxidation stability performance, the compound represented by formula (4) (bis form) is more preferable. Note that the method for producing such succinimide is not particularly limited, and for example, an alkyl succinic acid having an alkyl or alkenyl group having 40 to 400 carbon atoms, alkenyl succinic acid, and anhydride thereof. A method may be adopted in which the succinimide is produced as a condensation reaction product by reacting at least one selected from the group consisting of polyamine with a polyamine.

Further, the succinimide derivative (modified compound of succinimide) is not particularly limited, and any known modified compound of succinimide that can be used as an ashless dispersant can be appropriately used. Modified compounds with oxygen organic compounds (monocarboxylic acids with 1 to 30 carbon atoms such as fatty acids, polycarboxylic acids with 2 to 30 carbon atoms (e.g. oxalic acid, phthalic acid, trimellitic acid, pyromellitic acid, etc.), these acids The remaining amino groups and (ii) a boron-modified compound (by treating the succinimide with boric acid, one of the remaining amino groups and/or imino groups is neutralized or amidated); (iii) Phosphoric acid-modified compounds (by treating the succinimide with phosphoric acid, residual amino groups and/or Examples include compounds in which part or all of the imino group is neutralized or amidated.

In addition, as the "succinimide-based ashless dispersant" suitable as the component (C), among others, from the viewpoint of further improving corrosion resistance performance and oxidation stability performance, boron-modified compounds of the succinimide (boronated Succinimide) is more preferred.

The "succinimide-based ashless dispersant" suitable as the component (C) has a nitrogen content of 1.0 to 4.8% by mass (more preferably 1.0% by mass). 2 to 2.4% by mass). By controlling the nitrogen content within the above range, it becomes possible to more efficiently achieve high levels of corrosion resistance and oxidation stability. Further, when a "boronated succinimide" is used as the succinimide-based ashless dispersant, the boron content in the boronated succinimide is 0.01 to 5.0% by mass (more preferably 0.0% by mass). .2 to 2.2% by mass).

Further, as the "succinimide-based ashless dispersant" suitable as the component (C), those having a weight average molecular weight of 1000 to 9000 (more preferably 1000 to 5000) are more preferable. When the weight average molecular weight of the succinimide-based ashless dispersant is at least the above lower limit, it becomes possible to further improve the electrical insulation properties of the fresh oil and the electrical insulation properties of the composition after oxidative degradation. Moreover, when the weight average molecular weight of the succinimide-based ashless dispersant is equal to or less than the above upper limit, it becomes possible to further improve the electrical insulation properties of the composition after oxidative deterioration.

Furthermore, the "succinimide-based ashless dispersant" suitable as the component (C) has a total base number (TBN) of 20 to 80 mgKOH/g (more preferably 30 to 60 mgKOH/g). When the value of the total base number is within the above range, even higher effects in terms of oxidation stability performance tend to be obtained.

Moreover, the method for producing such component (C) is not particularly limited, and any known method can be used as appropriate. Moreover, as such component (C), a commercially available product may be used.

[About the composition of the lubricating oil composition]
The lubricating oil composition of the present invention contains the component (A), the component (B), and the component (C). In addition, as mentioned above, the component (B) contains the component (B1) (phosphorus-based extreme pressure agent) as an essential component.

Furthermore, in the lubricating oil composition of the present invention, the mass ratio of phosphorus derived from the component (B1) to nitrogen derived from the component (C) ([phosphorus]/[nitrogen]) is 0.60 or more. It needs to be 2.30 or less. When the mass ratio of phosphorus to nitrogen is equal to or higher than the above lower limit, the extreme pressure properties are made higher and the insulation properties are made higher than when the mass ratio is less than the above lower limit. On the other hand, if it is below the upper limit, it is possible to have higher seizure resistance and oxidation stability than when it exceeds the upper limit. . In addition, the mass ratio ([phosphorus]/[nitrogen]) of phosphorus derived from the component (B1) and nitrogen derived from the component (C) has a high degree of seizure resistance, wear resistance, and volume resistivity. 0.60 or more and 1.70 or less (more preferably 0.60 or more and 1.50 or less, particularly preferably 0.60 or more 1.30 or less) is more preferable.

Furthermore, in the lubricating oil composition of the present invention, the mass ratio ([sulfur]/[phosphorus]) of sulfur derived from the component (B2) to phosphorus derived from the component (B1) is 3.0 or less ( (more preferably 2.93 or less, still more preferably 2.2 or less). When the mass ratio of sulfur and phosphorus is below the upper limit, it is possible to achieve better oxidation stability and copper corrosion prevention than when it exceeds the upper limit. becomes.

Further, in the lubricating oil composition of the present invention, the content of the component (A) is not particularly limited, but is 80 to 98% by mass (more preferably 85 to 95% by mass) based on the total amount of the lubricating oil composition. It is preferable that When the content of such component (A) is at least the above-mentioned lower limit, it is possible to make the oxidation stability even better than when it is below the above-mentioned lower limit; In this case, it is possible to further improve the effect of the additive at the lubricated location and to make the lubricity even more excellent than in the case where the above upper limit is exceeded.

Furthermore, in the lubricating oil composition of the present invention, the content of phosphorus (P) derived from the component (B1) (total amount of phosphorus (P) derived from the component (B1)) It is preferably 0.050% by mass or less (more preferably 0.045% by mass or less, even more preferably 190 to 410 mass ppm, particularly preferably 190 to 380 mass ppm) based on the total amount of. When the content of phosphorus derived from such component (B1) is below the above upper limit, it is possible to further improve seizure resistance and wear resistance compared to when the content exceeds the above upper limit. becomes. In addition, when the content of phosphorus derived from the component (B1) is at least the above-mentioned lower limit, it becomes possible to obtain a composition having a higher volume resistivity than when it is less than the above-mentioned lower limit.

As mentioned above, the lubricating oil composition of the present invention does not contain a sulfur-containing extreme pressure agent (component (B2)), or even when it contains a component (B2), the component (B2) does not contain an extreme pressure agent (component (B2)). The derived sulfur content is 0.01% by mass (100 mass ppm) or less (more preferably 80 mass ppm or less, still more preferably 60 mass ppm or less, particularly preferably 50 mass ppm) based on the total amount of the lubricating oil composition. ppm or less, most preferably 20 mass ppm or less). By controlling the amount of sulfur derived from the sulfur-containing extreme pressure agent to below the above-mentioned upper limit, it is possible to achieve excellent oxidation stability and copper corrosion prevention properties.

Further, when the lubricating oil composition of the present invention contains a sulfur-containing extreme pressure agent (component (B2)) and the component (B2) contains phosphorus, the amount of phosphorus derived from the component (B2) is It is preferably 100 mass ppm or less (more preferably 80 mass ppm or less) based on the total amount of the oil composition. By controlling the amount of phosphorus derived from such component (B2) to be below the above-mentioned upper limit, it becomes possible to further improve corrosion resistance and oxidation stability.

Further, in the lubricating oil composition of the present invention, when the component (B) contains the component (B1-1), the content of phosphorus (P) derived from the component (B1-1) is It is preferably 50 to 500 mass ppm (more preferably 70 to 350 mass ppm) based on the total amount of the composition. When the content of phosphorus is equal to or higher than the lower limit, it is easier to improve load resistance (seizure resistance) and wear resistance than when the content is below the lower limit. On the other hand, when it is below the upper limit, it becomes possible to improve the insulation more easily than when it exceeds the upper limit.

Furthermore, in the lubricating oil composition of the present invention, when the component (B) contains the component (B1-2), the content of phosphorus (P) derived from the component (B1-2) is as described above. It is preferably 50 to 500 mass ppm (more preferably 100 to 200 mass ppm) based on the total amount of the lubricating oil composition. When the content of phosphorus is above the above-mentioned lower limit, it is possible to further improve seizure resistance and wear resistance compared to when the content is below the above-mentioned lower limit. In this case, it becomes possible to more efficiently obtain a composition with a high volume resistivity compared to a case in which the above-mentioned upper limit is exceeded.

Further, in the lubricating oil composition of the present invention, the content of the component (C) is not particularly limited, but the content of nitrogen derived from the component (C) is 100 to 100% based on the total amount of the lubricating oil composition. The amount is preferably 800 ppm by mass (more preferably 180 to 600 ppm by mass) (the upper limit of the content of nitrogen derived from the component (C) is more preferably 400 ppm by mass). , particularly preferably 200 ppm by mass). When the amount of nitrogen is at least the above lower limit, it is possible to further improve oxidation stability compared to when it is less than the above lower limit, while on the other hand, when it is below the above upper limit, the It becomes possible to increase the volume resistivity more easily than when the upper limit is exceeded.

Further, when a "boronated succinimide" is used as the component (C), the content of boron derived from the component (C) is preferably 200 mass ppm or less (more preferably is preferably 50 mass ppm or more and 130 mass ppm or less). When the amount of boron is at least the above-mentioned lower limit, it is possible to further improve seizure resistance and oxidation stability compared to when it is less than the above-mentioned lower limit, while on the other hand, when it is below the above-mentioned upper limit Compared to the case where the upper limit is exceeded, it becomes possible to suppress an increase in kinematic viscosity and to obtain a higher volume resistivity.

In the present invention, the contents of sulfur, phosphorus, nitrogen, and boron in the composition and various components are determined based on ASTM D4951.

Furthermore, the lubricating oil composition of the present invention may further contain additives in addition to the components (A) to (C). As such additives, known additives used in the field of lubricating oil compositions can be appropriately used, and are not particularly limited. It can be mentioned as a thing.

Examples of the component (D) include calcium sulfonate which is a calcium salt of an alkyl aromatic sulfonic acid, a basic salt of the calcium sulfonate, and an overbased salt of the calcium sulfonate. Examples of such alkyl aromatic sulfonic acids include so-called petroleum sulfonic acids and synthetic sulfonic acids. The petroleum sulfonic acid mentioned here includes those obtained by sulfonating an alkyl aromatic compound of a lubricating oil fraction of mineral oil, and so-called mahogany acid, which is a by-product during the production of white oil. Examples of synthetic sulfonic acids include straight-chain or branched alkyls obtained by recovering by-products in alkylbenzene manufacturing plants, which are raw materials for detergents, or by alkylating benzene with polyolefins. Examples include sulfonated alkylbenzenes having groups. Other examples of synthetic sulfonic acids include sulfonated alkylnaphthalenes such as dinonylnaphthalene. Further, the sulfonating agent for sulfonating these alkyl aromatic compounds is not particularly limited, and for example, fuming sulfuric acid or sulfuric anhydride can be used. Further, the weight average molecular weight of such alkyl aromatic sulfonic acid is preferably 300 to 1,500, more preferably 400 to 1,300. Further, the basic salt and overbased salt of the calcium sulfonate are not particularly limited, and known salts can be used as appropriate. For example, calcium sulfonate (over)based with calcium carbonate, calcium borate, etc. can be mentioned. The method for preparing basic salts and overbased salts is not particularly limited, and known methods can be used as appropriate (if the overbased salt is calcium sulfonate overbased with calcium carbonate, for example, A method may be employed to obtain calcium sulfonate overbased with calcium carbonate by reacting the calcium sulfonate with a base such as calcium hydroxide in the presence of calcium sulfonate).

Furthermore, such component (D) preferably has a total base number (TBN) of 20 to 450 mgKOH/g (more preferably 300 to 450 mgKOH/g). When the value of the total base number is within the above range, even higher effects in terms of oxidative stability tend to be obtained.

In addition, when the lubricating oil composition of the present invention contains the component (D), the content of the component (D) is the content of calcium derived from the component (D), which is the total amount of the lubricating oil composition. It is preferable to set the amount to 200 mass ppm or less (more preferably 180 mass ppm or less, still more preferably 160 mass ppm or less) based on . When the content of calcium is below the upper limit, it is possible to obtain a higher effect in terms of insulation than when the content exceeds the upper limit. In the present invention, the content of calcium in the composition and various components is determined based on ASTM D4951.

As component (E), those known in the field of lubricating oil compositions (for example, known ashless antioxidants such as amine antioxidants, phenolic antioxidants, etc.) can be used as appropriate, and in particular Although not limited thereto, it is preferable to use (E1) a phenolic antioxidant and (E2) an amine antioxidant in combination.

As the component (E1), for example, compounds known as phenolic antioxidants (for example, compounds exemplified in International Publication No. 2020/095970, etc.) can be used as appropriate. Examples of such phenolic antioxidants include hindered phenol compounds and bisphenol compounds.

In addition, as the component (E2), for example, compounds known as amine-based antioxidants such as aromatic amine-based antioxidants and hindered amine-based antioxidants (for example, exemplified in WO 2020/095970) Compounds etc.) can be used as appropriate. Among the aromatic amine antioxidants, alkylated diphenylamine and alkylated phenyl-α-naphthylamine can be suitably used. Further, as the hindered amine antioxidant, for example, a compound having a 2,2,6,6-tetraalkylpiperidine skeleton (2,2,6,6-tetraalkylpiperidine derivative), etc. can be suitably used. Among the amine antioxidants, aromatic amine antioxidants are more preferred, and alkylated diphenylamines are particularly preferred.

Further, when the lubricating oil composition of the present invention contains the component (E), the content (total amount) of the component (E) is 0.01 to 4.0% by mass (more preferably 0.01 to 4.0% by mass). 2.0% by mass). Further, when the component (E1) is contained, the content of the component (E1) is preferably 0.005 to 2.0% by mass (more preferably 0.005 to 1.0% by mass). . Furthermore, when the component (E2) is contained, the content of the component (E2) is preferably 0.005 to 2.0% by mass (more preferably 0.01 to 2.0% by mass). . By setting the content within the above range, it is possible to further improve anti-oxidation properties and improve anti-corrosion performance.

In addition, although the above-mentioned (D) component and the above-mentioned (E) component have been illustrated and explained as suitable additives that can be suitably used in the lubricating oil composition of the present invention, Usable additives are not limited to the above-mentioned components (D) and (E), but include pour point depressants, metal deactivators, friction modifiers, etc., as long as they do not impair the effects of the present invention. agent, dispersant other than the nitrogen-containing ashless dispersant, viscosity index improver, rubber swelling agent, antifoaming agent, diluent oil, rust preventive agent, demulsifier, coloring agent, corrosion inhibitor, antiwear agent, acid Other known additive components such as scavengers (for example, JP 2016-3258 A, WO 2015/056783, JP 2016-160312, JP 2003-155492, WO 2017/ 073748, JP-A-2020-76004, etc.) can also be used as appropriate.

In addition, when using additive components other than the above-mentioned (D) component and (E) component, the total amount (total amount) of the other additive components is 0.5 to 2% based on the total amount of the lubricating oil composition. More preferably, it is .0% by mass. When the total amount of these other additive components is at least the above lower limit, it is possible to obtain higher effects in terms of corrosion resistance and oxidation stability than when it is less than the above lower limit. If it is below the upper limit, it is possible to obtain higher effects in terms of seizure resistance and wear resistance than when it exceeds the upper limit.

The various additives that can be used in such lubricating oil compositions may be prepared and added to each component separately, or may be prepared and added as a mixture of other components. Good too. As a mixture of such other components, a commercially available packaged product (for example, an additive package containing a rubber swelling agent, an antifoaming agent, a pour point depressant, etc.) may be used as appropriate.

[About the characteristics, manufacturing method, uses, etc. of lubricating oil compositions]
The lubricating oil composition of the present invention has a kinematic viscosity (KV40 _OL ) of the lubricating oil composition at 40°C after being oxidized at an oil temperature of 165°C for 192 hours by the ISOT method in accordance with JIS K2514-1. The ratio ([KV40 _OL ]/[KV40 _L ]) of the lubricating oil composition to the kinematic viscosity at 40°C (KV40 _L ) of the lubricating oil composition before performing the oxidation treatment needs to be 1.06 or less. By setting the kinematic viscosity ratio ([ _KV40OL ]/[ _KV40L ]) at 40°C of the lubricating oil composition before and after such oxidation treatment to be below the above-mentioned upper limit, compared to the case where it exceeds the above-mentioned upper limit, It becomes possible to suppress the increase in viscosity due to oxidative deterioration, and when used in a transmission, it becomes possible to exhibit high transmission efficiency over a long period of time. The kinematic viscosity ratio ([KV40 _OL ]/[KV40 _L ]) at 40° C. of the lubricating oil composition before and after such oxidation treatment is more preferably 0.95 or more and 1.06 or less, and 1.0 More preferably, the value is 1.02 or less. By setting such a ratio ([KV40 _OL ]/[KV40 _L ]) within the above range, a higher effect in terms of oxidation stability tends to be obtained compared to a case outside the above range. When used in a transmission, it becomes possible to exhibit high transmission efficiency over a longer period of time.

The lubricating oil composition of the present invention has a kinematic viscosity at 40°C (KV40 _L : kinematic viscosity of the composition (new oil) that has not been subjected to the above-mentioned oxidation treatment) of 8.0 to 18.0 mm ² /s (more than 8.0 to 14.0 mm ² /s) is preferred. When _{the KV40L} of the lubricating oil composition is below the upper limit, compared to the case where it exceeds the upper limit, in a relatively low temperature range around 40°C (preferably about 20 to 60°C), It becomes possible to further reduce stirring resistance, and it becomes possible to further improve power transmission efficiency even in low temperature conditions such as immediately after the start of use, so it becomes possible to further improve fuel efficiency performance. In addition, when the kinematic viscosity at 40°C of the lubricating oil composition is equal to or higher than the lower limit, the lubricating oil composition may be used at a lubricating point in a relatively low temperature range around 40°C (preferably about 20 to 60°C). The oil film forming property and oil film retaining property of the composition are further improved, making it possible to maintain a better lubrication state, and from this viewpoint, it is possible to further improve gear transmission efficiency and power saving performance.

The lubricating oil composition of the present invention has a kinematic viscosity (KV40 _OL ) is preferably 8.0 to 20.0 mm ² /s (more preferably 8.0 to 18.0 mm ² /s). If the KV40 _OL of the lubricating oil composition is below the upper limit, it will improve oxidation stability and improve transmission efficiency when used in a transmission, compared to when it exceeds the upper limit. On the other hand, when the KV40 _OL of the lubricating oil composition is equal to or higher than the lower limit, higher wear resistance and anti-seizure properties can be obtained than when the KV40 OL of the lubricating oil composition is below the lower limit. It becomes possible to obtain sex.

The lubricating oil composition of the present invention has a kinematic viscosity at 40° C. of the lubricating base oil that has not been subjected to the oxidation treatment (KV40 _B : kinematic viscosity of the base oil in a fresh oil state that has not been subjected to the oxidation treatment). and the kinematic viscosity at 40°C of the lubricating composition before the oxidation treatment ( _KV40L : kinematic viscosity of the composition in the fresh oil state that has not been subjected to the oxidation treatment)) ([ _KV40L ] /[KV40 _B ]) is preferably 0.95 or more and 1.15 or less (more preferably 0.95 or more and 1.10 or less). If the kinematic viscosity ratio ([KV40 _L ]/[KV40 _B ]) is below the above upper limit, the kinematic viscosity of the lubricant base oil at 40°C will be lower than when it exceeds the above upper limit. Since the kinematic viscosity ratio at 40°C of the lubricating oil composition is smaller, the effect of viscosity is smaller, and when used in a transmission, a higher effect can be obtained in terms of improving transmission efficiency. , when the ratio ([KV40 _L ]/[KV40 _B ]) is equal to or higher than the lower limit, higher effects can be obtained in terms of wear resistance and seizure resistance than when the ratio is less than the lower limit. It will be done.

The lubricating oil composition of the present invention has a kinematic viscosity at 100°C (the kinematic viscosity of the composition (new oil) that has not been subjected to the above-mentioned oxidation treatment) of 1.8 to 4.0 mm ² /s (more preferably 2 .2 to 3.5 mm ² /s) is preferred. If the kinematic viscosity at 100°C of the lubricating oil composition is below the upper limit, it will have a lower viscosity in a relatively high temperature range around 100°C than when it exceeds the upper limit. Since it is possible to further reduce the stirring resistance, it is possible to further improve power transmission efficiency, and it is possible to improve fuel efficiency. In addition, when the kinematic viscosity at 100°C of the lubricating oil composition is equal to or higher than the lower limit, the lubricating oil at the lubricating point may Since the oil film forming and oil film retaining properties of the composition are further improved and the oil film can be maintained more uniformly, it is possible to further improve the anti-seizure performance during use.

Further, as the lubricating oil composition of the present invention, it is preferable that the lubricating oil composition has a viscosity index of 105 or more (more preferably 120 or more). When the viscosity index is at least the lower limit (more preferably at least 120), the viscosity-temperature characteristics and anti-wear properties of the lubricating oil composition are improved compared to when it is less than the lower limit (more preferably at least 120). It becomes possible to further improve fuel efficiency, and it becomes possible to further improve fuel efficiency.

The lubricating oil composition of the present invention has a volume resistivity at 80° C. of 0.0020×10 ¹² Ωcm or more (more preferably 0.0022×10 ¹² Ωcm or more, still more preferably 0.0024×10 ¹² Ωcm or more). It is preferable that there be. By setting the volume resistivity to the lower limit value or more, it is possible to ensure a high level of insulation that is higher than the level required for use in electric vehicles. Note that the upper limit of the volume resistivity at 80° C. of the lubricating oil composition is not particularly limited, but from the viewpoint of discharge resistance, it is preferably 0.10×10 ¹² Ωcm. As such volume resistivity, a value measured by performing measurement at an oil temperature of 80° C. in accordance with the volume resistivity test specified in JIS C2101 is adopted.

The method for producing the lubricating oil composition of the present invention is not particularly limited, and each component to be contained is selected so that the lubricating oil composition of the present invention can be obtained (so as to satisfy the above conditions). It may be prepared by appropriately selecting and mixing.

The lubricating oil composition of the present invention has a high level of well-balanced insulation properties, oxidation stability, and extreme pressure properties, and has high copper corrosion prevention properties, so its applications are particularly limited. However, it can be suitably used as a composition for lubricating transmissions and for cooling and lubricating electric motors. That is, the lubricating oil composition of the present invention can be suitably used as a lubricating oil composition for an electric vehicle equipped with an electric motor and a transmission.

EXAMPLES Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

(About the ingredients used in each example, etc.)
First, the base oil and additives used in each example are shown below.

[(A) Lubricant base oil]
(A1) Wax isomerized base oil [mineral oil: API Group III, kinematic viscosity at 40°C: 9.422 mm ² /s, kinematic viscosity at 100°C: 2.676 mm ² /s, viscosity index: 125, in base oil Sulfur content (sulfur content in base oil): 0 mass ppm, pour point: -37°C, flash point: 190°C]
(A2) Hydrocracked base oil [mineral oil: API Group II, kinematic viscosity at 40°C: 8.546 mm ² /s, kinematic viscosity at 100°C: 2.431 mm ² /s, viscosity index: 105, in base oil Sulfur content (sulfur content in base oil): 0 mass ppm, pour point: -30°C, flash point: 170°C].

[(B) Extreme pressure agent]
<(B1) Phosphorous extreme pressure agent>
(B1-1) Alkylamine salt of phosphoric acid ester [phosphoric acid ester (mixture of monoester and diester: a compound represented by the above formula (1), and R ^a in the formula is an oleyl group (formula: C ₁₈ A compound that is a group represented by H ₃₅ ) and an alkylamine (a compound represented by the above formula (2), in which one of R ^b , R ^c and R ^d is a dodecyl group (a group represented by the formula : a group represented by C ₁₂ H ₂₅ ) and the others among R ^b , R ^c and R ^d are hydrogen atoms]
(B1-2) Phosphite [dibutyl hydrogen phosphite]
<(B2) Sulfur-containing extreme pressure agent>
(B2-1) Thiophosphoric acid ester [phosphorus content: 100,000 mass ppm, sulfur content: 190,000 mass ppm].

[(C) Nitrogen-containing ashless dispersant]
(C1) Succinimide-based ashless dispersant [boronated succinimide, nitrogen content: 2.0% by mass, boron content: 0.5% by mass, total base number (TBN): 50, succinic acid Imide type: bis-type succinimide (bis-type succinimide represented by the above formula (4) (here, R ¹ and R ² in formula (4) are polyisobutenyl groups with a weight average molecular weight (Mw) of 1000). and n is 3)].

[(D) Calcium sulfonate detergent]
(D1) Calcium sulfonate detergent [base number (TBN): 400 mgKOH/g, content of calcium atoms: 15.0% by mass].

[(E) Antioxidant]
(E1) Phenolic antioxidant [octyl 3-(4-hydroxy-3,5-diisopropylphenyl)propionate]
(E2) Amine antioxidant [alkylated diphenylamine].

[(F) Other additives (performance additives)]
(F1) Performance additive [mixture of rubber swelling agent, antifoam agent and pour point depressant (additive package)].

(Examples 1 to 7 and Comparative Examples 1 to 4)
The lubricating oil compositions of Examples 1 to 7 and Comparative Examples 1 to 4 were prepared using the above-mentioned components so as to have the compositions shown in Tables 1 to 2. In addition, regarding the item "composition" in Tables 1 and 2, "-" indicates that the component is not used. In addition, in the "composition" item in Tables 1 and 2, "inmass%" represents the mass-based content (mass%) relative to the total amount of the lubricant base oil, and "mass%" represents the total amount of the lubricant composition. "ppm (N conversion)" represents the mass-based content (mass %) of the lubricating oil composition, and "ppm (N conversion)" is the mass-based content (mass ppm) of the lubricating oil composition derived from the component, based on nitrogen atoms, relative to the total amount of the lubricating oil composition. "ppm (P conversion)" represents the mass-based content (mass ppm: total amount of the lubricating oil composition derived from the component) in terms of phosphorus atoms relative to the total amount of the lubricating oil composition. "ppm (S conversion)" represents the mass-based content (mass ppm: sulfur content relative to the total amount of the lubricating oil composition derived from the component) in terms of sulfur atoms relative to the total amount of the lubricating oil composition. "ppm (Ca equivalent)" represents the mass-based content (mass ppm: calcium content relative to the total amount of the lubricating oil composition derived from the component) in terms of calcium atoms relative to the total amount of the lubricating oil composition. amount). Furthermore, in Tables 1 and 2, the contents of phosphorus, nitrogen, sulfur, boron, and calcium are values measured in accordance with ASTM D4951. In addition, in Tables 1 and 2, the expression "Content of phosphorus derived from component (B1)" refers to the percentage of the mass-based content of phosphorus derived from component (B1) contained in the lubricating oil composition ( mass%: mass%), and the expression "content of sulfur derived from component (B2)" refers to the mass-based content ratio of sulfur derived from component (B2) contained in the lubricating oil composition. (mass%), and the expression "content of nitrogen derived from component (C)" refers to the mass-based content of nitrogen derived from component (C) contained in the lubricating oil composition. The expression "content of boron derived from component (C)" refers to the mass-based content of boron derived from component (C) contained in the lubricating oil composition. The ratio (mass%) is shown. In addition, in Tables 1 and 2, the expression "phosphorus derived from component (B1)/nitrogen derived from component (C)" refers to the above "phosphorus content derived from component (B1)" and the above "phosphorus content derived from component (C)". The expression "sulfur derived from component (B2)/phosphorus derived from component (B1)" indicates the ratio (mass ratio: [phosphorus]/[nitrogen]) to the nitrogen content of The ratio (mass ratio: [sulfur]/[phosphorus]) of the "content of sulfur derived from the component" and the "content of phosphorus derived from the component (B1)" is shown.

[About the evaluation method of the characteristics of the lubricating oil composition obtained in each example etc.]
<Measurement of volume resistivity>
For each lubricating oil composition, the volume resistivity of the new oil was measured. Here, the volume resistivity was measured at an oil temperature of 80° C. in accordance with the volume resistivity test specified in JIS C2101. The results obtained are shown in Tables 1 and 2. Note that if the volume resistivity at 80° C. is 0.0020×10 ¹² Ω·cm or more, it can be evaluated as having a high degree of insulation.

<Falex seizure test: Seizure resistance confirmation test>
Each lubricating oil composition was subjected to a Farex seizure test in accordance with ASTM D3233 A method, and the load at which seizure occurred (unit: lbf) was measured. The results obtained are shown in Tables 1 and 2. Note that if the load at which seizure occurred is 700 lbf or more, it can be determined that the seizure resistance is good.

<Falex abrasion test: Wear resistance confirmation test>
For each lubricating oil composition, a Falex test (Falex wear resistance test) was conducted in accordance with ASTM D2670 at an oil temperature of 80°C, a load of 390 lb, a rotation speed of 290 rpm, and a duration of 1 hour, and the amount of wear (mg ) was measured. The results obtained are shown in Tables 1 and 2. Note that if the amount of wear is 55.0 mg or less, it can be determined that the wear resistance is good.

<Confirmation test of copper plate corrosion resistance>
Approximately 30 mL of samples were prepared from each lubricating oil composition and subjected to a copper plate corrosion test in accordance with JIS K 2513 to evaluate copper plate corrosion resistance. That is, in accordance with JIS K2513, a copper plate is completely immersed in approximately 30 mL of a sample, held at an oil temperature of 150°C for 192 hours, taken out, washed, and compared with a copper plate corrosion standard to determine the copper plate corrosion of the sample. The corrosion resistance against copper was evaluated by determining the corrosion resistance against copper. The results obtained are shown in Tables 1 and 2. In addition, when the judgment value (discoloration number) of the copper plate corrosion standard is 2 or less, it can be judged that the copper corrosion prevention property is high.

<Evaluation of oxidation stability: Confirmation test for the occurrence of strong acid value after oxidation treatment>
Each lubricating oil composition was oxidized using the ISOT (Indiana Stirring Oxidation Test) method in accordance with JIS K2514-1 at an oil temperature of 165°C for 192 hours. The presence or absence of strong acid value was confirmed. Lubricating oil compositions that did not generate a strong acid value were evaluated as having high oxidation stability and were evaluated as "passing," while lubricating oil compositions that did develop a strong acid value were evaluated as having insufficient oxidation stability and were evaluated as "failing." ” The results obtained are shown in Tables 1 and 2.

<Measurement of kinematic viscosity ratio>
For each lubricating oil composition, the kinematic viscosity at 40°C (KV40 _OL ) of the lubricating oil composition after oxidation treatment at an oil temperature of 165°C for 192 hours by the ISOT method in accordance with JIS K2514-1, The kinematic viscosity at 40° C. (KV40 _L ) of the lubricating oil composition before the oxidation treatment was determined, and the ratio thereof ([KV40 _OL ]/[KV40 _L ]) was determined. In addition, for each lubricating oil composition, the kinematic viscosity at 40°C of the base oil used (KV40 _B : kinematic viscosity of new oil) and the kinematic viscosity at 40°C of the lubricating oil composition before performing the oxidation treatment (KV40 _L ) ([KV40 _L ]/[KV40 _B ]) was also determined. The kinematic viscosity at 40° C. was determined according to JIS K 2283-2000. The results obtained are shown in Tables 1 and 2.

As is clear from the results shown in Table 1, the lubricating oil compositions obtained in Examples 1 to 7 (corresponding to the lubricating oil compositions of the present invention) have a volume resistivity of 0.0020×10 ¹² Ωcm or more. It was found that this material is suitable for lubrication and cooling of electric motors that require a high level of insulation. Furthermore, the lubricating oil compositions obtained in Examples 1 to 7 (corresponding to the lubricating oil compositions of the present invention) have good anti-seizing properties and good wear resistance. It was confirmed that the extreme pressure resistance based on wear resistance was also high. Furthermore, it was found that the lubricating oil compositions obtained in Examples 1 to 7 (corresponding to the lubricating oil compositions of the present invention) did not generate strong acid values and had a high degree of oxidative stability. . Furthermore, as shown in Table 1, it was confirmed that the lubricating oil compositions obtained in Examples 1 to 7 (corresponding to the lubricating oil compositions of the present invention) had high copper corrosion prevention properties. . Further, all of the lubricating oil compositions obtained in Examples 1 to 7 (corresponding to the lubricating oil compositions of the present invention) had a kinematic viscosity ratio ([KV40 _OL ]/[KV40 _L ]) was 1.05 or less, and from this point of view, it was also found that the oxidation stability was high. From these results, the lubricating oil compositions obtained in Examples 1 to 7 have high levels of insulation, oxidation stability, and extreme pressure properties, and are considered to have a good balance of these properties. In addition, it was found to have high copper corrosion prevention properties.

On the other hand, as is clear from the results shown in Table 2, the mass ratio (P/N) of the phosphorus content derived from component (B1) and the nitrogen content derived from component (C) is 2.30. The lubricating oil composition obtained in Comparative Example 1 with a value exceeding (2.68) did not have sufficient anti-seizure properties and was unable to achieve a high level of extreme pressure properties. There wasn't. Furthermore, the lubricating oil composition obtained in Comparative Example 1 had a strong acid value, and could not have a high level of oxidation stability. Furthermore, the lubrication obtained in Comparative Examples 2 and 3 in which the mass ratio (P/N) of the phosphorus content derived from component (B1) and the nitrogen content derived from component (C) was less than 0.60. Oil compositions have not always been sufficient in terms of extreme pressure properties or insulation properties. In addition, the content of sulfur derived from the sulfur-containing extreme pressure agent exceeds 100 mass ppm (200 mass ppm), and the sulfur derived from the component (B2) and the phosphorus derived from the component (B1) are combined. The lubricating oil composition obtained in Comparative Example 4 in which the mass ratio (S/P) exceeds 3.0 (4.55) has a strong acid value, and the lubricating oil composition before and after the oxidation treatment The kinematic viscosity ratio ([KV40 _OL ]/[KV40 _L ]) of the composition at 40° C. was also 1.08, and the oxidation stability could not be achieved at a high level. Furthermore, the lubricating oil composition obtained in Comparative Example 4 did not have high copper corrosion prevention properties.

As explained above, according to the present invention, there is provided a lubricating oil composition that has a high level of well-balanced insulation properties, oxidation stability, and extreme pressure properties, as well as a high degree of copper corrosion prevention. becomes possible. Therefore, the lubricating oil composition of the present invention is particularly useful as a lubricating oil composition for electric vehicles.

Claims (5)

(A) Lubricant base oil,
(B) an extreme pressure agent, and
(C) nitrogen-containing ashless dispersant;
A lubricating oil composition comprising:
The component (B) is
(B1) contains a phosphorus-based extreme pressure agent that is at least one compound selected from the group consisting of phosphoric acid, phosphoric acid ester, phosphite ester, and salts thereof, and
(B2) Does not contain a sulfur-containing extreme pressure agent, or contains the ( B2) Contains the component,
The mass ratio of phosphorus derived from the component (B1) to nitrogen derived from the component (C) ([phosphorus]/[nitrogen]) is 0.60 or more and 2.30 or less,
The mass ratio of sulfur derived from the component (B2) to phosphorus derived from the component (B1) ([sulfur]/[phosphorus]) is 3.0 or less,
The kinematic viscosity at 40°C (KV40OL) of the lubricating oil composition after oxidation treatment at an oil temperature of 165°C for 192 hours by the ISOT method according to JIS K2514-1, and the kinematic viscosity ( _KV40OL ) of the lubricating oil composition before the oxidation treatment The ratio ([ _KV40OL ]/[ _KV40L ]) of the lubricating oil composition to the kinematic viscosity ( _KV40L ) at 40°C is 1.06 or less;
A lubricating oil composition characterized by: _The ratio ( _[ The lubricating oil composition according to claim 1, wherein KV40 _L ]/[KV40 _B ]) is 0.95 or more and 1.15 or less. The lubricating base oil contains at least one selected from the group consisting of hydrotreated base oils and wax isomerized base oils, and the lubricating base oil has a kinematic viscosity of 20 mm ² /s or less at 40°C. The lubricating oil composition according to claim 1, characterized in that: The lubricating oil composition according to claim 1, further comprising (D) a calcium sulfonate detergent such that the calcium content is 200 mass ppm or less based on the total amount of the lubricating oil composition. The lubricating oil composition according to claim 1, which is a composition for lubricating a transmission and for cooling and lubricating an electric motor.