WO2021193443A1

WO2021193443A1 - Lubricating oil composition

Info

Publication number: WO2021193443A1
Application number: PCT/JP2021/011432
Authority: WO
Inventors: 翔横山
Original assignee: 出光興産株式会社
Priority date: 2020-03-27
Filing date: 2021-03-19
Publication date: 2021-09-30
Also published as: EP4130212A4; US20230174887A1; CN115279872A; JPWO2021193443A1; TW202200769A; EP4130212A1

Abstract

The present invention addresses the problem of providing a lubricating oil composition having excellent long-term defoaming performance and cleanliness despite being compounded with a silicone-based defoaming agent. The problem was overcome by a lubricating oil composition containing a base oil (A) and a silicone-based defoaming agent (B), wherein the lubricating oil composition has a silicon atom content of 50 to 4,000 mass ppb based on the total amount of lubricating oil composition.

Description

Lubricating oil composition

The present invention relates to a lubricating oil composition.

Lubricating oil compositions are widely used in various fields because they have anti-friction action, sealing action, rust-preventive / anti-corrosion action, cooling action, power transmission action and the like in various mechanical devices.
By the way, in the lubricating oil composition, foaming may occur due to air entrainment or the like when the mechanical device is operated. The bubbles generated in the lubricating oil composition lead to a decrease in lubrication performance, a decrease in sealing property, a promotion of oxidative deterioration, a decrease in cooling efficiency, a decrease in power transmission efficiency, and the like.
Therefore, a defoaming agent is added to the lubricating oil composition as a countermeasure against foaming. As a typical example of the defoaming agent blended in the lubricating oil composition, a silicone-based defoaming agent is known (see, for example, Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 2020-026447 Japanese Unexamined Patent Publication No. 2017-066220

However, as a result of diligent studies by the present inventor, the silicone-based defoaming agent can impart defoaming performance to the lubricating oil composition for a long period of time, but is a factor that deteriorates the cleanliness of the lubricating oil composition. It came to be found that it has a problem of becoming.
In the present invention, the cleanliness of the lubricating oil composition means the cleanliness evaluated by the pollution degree code of ISO4406: 1999.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a lubricating oil composition excellent in both long-term defoaming performance and cleanliness while blending a silicone-based defoaming agent. ..

As a result of diligent studies, the present inventor has found that the above problems can be solved by adjusting the silicon atom content of the lubricating oil composition containing a silicone-based defoaming agent to a specific range.

That is, the present invention relates to the following [1].
[1] A lubricating oil composition containing a base oil (A) and a silicone-based defoaming agent (B).
A lubricating oil composition having a silicon atom content of 50 mass ppb to 4,000 mass ppb based on the total amount of the lubricating oil composition.

According to the present invention, it is possible to provide a lubricating oil composition excellent in both long-term defoaming performance and cleanliness while blending a silicone-based defoaming agent.

In the present specification, the lower limit value and the upper limit value described stepwise for a preferable numerical range (for example, a range such as content) can be independently combined. For example, from the description of "preferably 10 to 90, more preferably 30 to 60", the "favorable lower limit value (10)" and the "more preferable upper limit value (60)" are combined to obtain "10 to 60". be able to.
In the present specification, the numerical values of Examples are numerical values that can be used as upper limit values or lower limit values.
In the present specification, the numerical range expressed as "AA to BB" means "AA or more and BB or less" unless otherwise specified.

[Aspects of Lubricating Oil Composition of the Present Invention]
The lubricating oil composition of the present invention is a lubricating oil composition containing a base oil (A) and a silicone-based defoaming agent (B), and the silicon atom content is based on the total amount of the lubricating oil composition. , 50 mass ppb to 4,000 mass ppb.

The present inventor has made diligent studies in order to provide a lubricating oil composition excellent in both long-term defoaming performance and cleanliness while blending a silicone-based defoaming agent.
First, the present inventor has conducted various studies on factors that deteriorate the cleanliness of a lubricating oil composition containing a silicone-based defoaming agent. As a result, the amount of silicone-based defoaming agent (about 1% by mass based on the total amount of the lubricating oil composition, about 10% by mass in terms of silicon atom), which was conventionally assumed to be necessary for maintaining the defoaming performance, was added. It was found that when blended in a lubricating oil composition, the cleanliness evaluated by ISO4406: 1999 deteriorated and did not meet the standard. As a result of examining the cause in detail, in ISO4406: 1999, in order to grasp the distribution of contaminants in the sample by counting the fine particles in the sample, the silicone particles, which are the active components of the silicone-based defoaming agent, are used as fine particles. As a result of the measurement, it was found that the cleanliness evaluated by ISO4406: 1999 deteriorated and did not meet the standard.
As a result of further studies by the present inventor based on such problems, it is surprisingly clear that long-term defoaming performance can be ensured even if the blending amount of the silicone-based defoaming agent is significantly reduced. became. Moreover, by significantly reducing the amount of the silicone-based defoaming agent, the number of silicone particles is reduced and the cleanliness is improved. Therefore, as a result of investigating the content of the silicone-based defoaming agent, the present inventor has found a range in which a lubricating oil composition excellent in both long-term defoaming performance and cleanliness can be obtained, and completed the present invention. I came to do it.

In the following description, the "base oil (A)" and the "silicone antifoaming agent (B)" are also referred to as "component (A)" and "component (B)", respectively.
The lubricating oil composition of one aspect of the present invention may be composed of only the component (A) and the component (B), but the component (A) and the component (B) are used as long as the effects of the present invention are not impaired. It may contain other components other than.
In the lubricating oil composition of one aspect of the present invention, the total content of the component (A) and the component (B) is preferably 75% by mass or more, more preferably 80% by mass or more, based on the total amount of the lubricating oil composition. , More preferably 85% by mass or more.
The upper limit of the total content of the component (A) and the component (B) may be adjusted in consideration of the balance with the components other than the component (A) and the component (B), and is based on the total amount of the lubricating oil composition. It is preferably 94.9% by mass or less, more preferably 94% by mass or less, still more preferably 92% by mass or less, still more preferably 90% by mass or less.

Hereinafter, each component contained in the lubricating oil composition of the present invention will be described in detail.

<Base oil (A)>
As the base oil (A), a base oil conventionally used as a lubricating oil base oil can be used without particular limitation, and for example, one or more selected from the group consisting of mineral oils and synthetic oils may be used. Can be done.

As the mineral oil, for example, atmospheric residual oil obtained by atmospheric distillation of crude oil such as paraffin crude oil, intermediate base crude oil, or naphthenic crude oil; and distillate obtained by vacuum distillation of these atmospheric residual oils. Oil; Mineral oil obtained by subjecting the distillate oil to one or more refining treatments such as solvent desorption, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining; and the like.
One type of mineral oil may be used alone, or two or more types may be used in combination.

Examples of synthetic oils include hydrocarbon oils, aromatic oils, ester oils, ether oils, and distillations between two points of distillation amounts of 2.0% by volume and 5.0% by volume on the distillation curve. Base oil having a temperature gradient Δ | Dt | of 6.8 ° C./% by volume or less (preferably, the saturation content by the Kregel method measured according to ASTM D-2007 is 90% by mass or more, and ASTM. A base oil having a sulfur content of 0.03% by mass or less measured according to D1552 and a viscosity index of 120 or more obtained according to ASTM D2270) and the like can be mentioned.
In the present specification, the temperature gradient Δ | Dt | of the distillation temperature between the two points of the distillation amount of 2.0% by volume and 5.0% by volume in the distillation curve means a value calculated from the following formula. do.
-Temperature gradient Δ | Dt | (° C./volume%) = | [Distillation temperature (° C.) at which the distillate amount of base oil is 5.0% by volume]-[Distillation amount of base oil is 2.0% by volume. Distillation temperature (° C)] | /3.0 (volume%)
The "distillation temperature at which the distillation amount of the base oil is 5.0% by volume and 2.0% by volume" in the above formula is a value measured by a method based on ASTM D6352, and specifically, in Examples. Means the value measured by the method described in.
The temperature gradient Δ | Dt | is preferably 6.5 ° C./volume% or less, more preferably 6.3 ° C./volume% or less, still more preferably 6.0 ° C./volume% or less, still more preferably 5. It is 0 ° C./volume% or less.
Further, the temperature gradient Δ | Dt | is usually 0.1 ° C./volume% or more.
The distillation temperature at a distillation amount of 2.0% by volume on the distillation curve is preferably 405 to 510 ° C., more preferably 410 to 500 ° C., still more preferably 415 to 490 ° C., still more preferably 430 to 480 ° C. be.
The distillation temperature at a distillation amount of 5.0% by volume on the distillation curve is preferably 425 to 550 ° C, more preferably 430 to 520 ° C, still more preferably 434 to 500 ° C, still more preferably 450 to 490 ° C. be.
The paraffin content in the base oil in which the temperature gradient Δ | Dt | of the distillation temperature between the two points of the distillation amount of 2.0% by volume and 5.0% by volume on the distillation curve is 6.8 ° C./% by volume or less. The (% _CP ) is usually 50 or more, preferably 55 or more, more preferably 60 or more, still more preferably 65 or more, still more preferably 70 or more, still more preferably 80 or more, and usually 99 or less. be.
In this specification, the paraffin component (% _{C P)} means a value measured in conformity with ASTM D-3238 ring analysis (n-d-M method).
Here, the temperature gradients specified in the above requirements are the state of the base oil, such as the light content and the structure of the wax, which cannot be removed even in the refining process performed by performing one or more of the above refining treatments, and the lubricating oil. It is a parameter that takes into account the relationship with the ignition point when made into a composition. When the distillate amount is 2.0 to 5.0% by volume, the fluctuation of the distillation curve is stable and even the light component remains. Since it is in the temperature range, it is possible to accurately evaluate the state of the light and wax components of the base oil.
As the synthetic oil, one type may be used alone, or two or more types may be used in combination.

In the lubricating oil composition of one aspect of the present invention, the base oil (A) may be one selected from mineral oils or one selected from synthetic oils, and foaming is likely to occur among these. , May be one selected from mineral oil.
Further, the base oil (A) may be a mixed base oil in which two or more kinds selected from the group consisting of mineral oil and synthetic oil are mixed. The base oil used in the lubricating oil composition may be a mixed base oil in which two or more kinds of base oils are mixed from the viewpoint of improving various performances required for the lubricating oil composition. On the other hand, a mixed base oil in which two or more kinds of base oils are mixed is particularly prone to foaming. INDUSTRIAL APPLICABILITY The present invention can provide a lubricating oil composition excellent in both long-term defoaming performance and cleanliness even for a mixed base oil in which foaming is particularly likely to occur.
The two or more types of base oil may be a combination of two or more types of base oils having different oil types, and the two types have the same oil type but different physical property values (for example, kinematic viscosity at 40 ° C.). It may be a combination of the above base oils. Further, it is a combination of two or more kinds of base oils having the same oil type but different physical characteristics (for example, kinematic viscosity at 40 ° C.) and one or more kinds of base oils having different oil types from the base oil. You may.

Here, the base oil (A) may be a mixed base oil in which a high-viscosity base oil (AH) and a low-viscosity base oil (AL) are combined. Further, it may be a mixed base oil in which another base oil (AZ) is further combined with the high-viscosity base oil (AH) and the low-viscosity base oil (AL).
Hereinafter, the high-viscosity base oil (AH), the low-viscosity base oil (AL), and other base oils (AZ) will be described.

(High viscosity base oil (AH))
The high-viscosity base oil (AH) contributes to the improvement of the wear resistance and the fatigue-resistant life of the lubricating oil composition by maintaining the kinematic viscosity of the base oil (A) at a high level.
Here, from the viewpoint of making it easier to improve the wear resistance and fatigue resistance life of the lubricating oil composition, the kinematic viscosity of the high-viscosity base oil (AH) at 40 ° C. (hereinafter, also referred to as “40 ° C. kinematic viscosity”). Is preferably 1,000 mm ² / s or more, more preferably 1,100 mm ² / s or more, and further preferably 1,200 mm ² / s or more. The upper limit of the high viscosity base oil (AH) is preferably 2,000 mm ² / s. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, preferably ^{^{1,000mm 2 / s ~ 2,000mm 2 /}} s, more preferably ^{^{1,100mm 2 / s ~ 2,000mm 2 /}} s, more preferably 1,200mm ² / s ~ ^2, It is 000 mm ² / s.

The high-viscosity base oil (AH) is preferably a poly α-olefin (hereinafter, also referred to as “PAO”) from the viewpoint of high viscosity indexing of the lubricating oil composition. Examples of PAO include polybutene, polyisobutylene, 1-decene oligomer, ethylene-propylene copolymer and the like, and hydrides thereof.
One type of PAO may be used alone, or two or more types may be used in combination.

Further, from the viewpoint of further increasing the viscosity index of the lubricating oil composition, the high viscosity base oil (AH) is a polyα-olefin obtained by using a metallocene catalyst as PAO (hereinafter, also referred to as “mPAO”). Is more preferable.
The mPAO is a poly-α obtained by using one kind of α-olefin having 8 to 12 carbon atoms alone or in combination of two or more kinds as a raw material and producing (polymerizing) it in the presence of a metallocene catalyst. -An olefin or a hydride thereof.
The α-olefin having 8 to 12 carbon atoms as a raw material of mPAO may be linear or has a branched chain, but a linear α-olefin is preferably used, for example. Examples thereof include 1-octene, 1-nonene, 1-decene, 1-undecene and 1-dodecene, and preferably decene oligomers obtained by polymerization using 1-decene as a raw material.
As the metallocene catalyst, which is a polymerization catalyst used in the production of mPAO, a complex having a conjugated carbon 5-membered ring containing a Group 4 element of the periodic table, that is, a metallocene complex and an oxygen-containing organoaluminum compound can be used in combination. ..
As the Group 4 element of the periodic table in the metallocene complex, titanium, zirconium and hafnium are used, and zirconium is preferable. Further, as the complex having a conjugated carbon 5-membered ring, a complex having a substituted or unsubstituted cyclopentadienyl ligand is generally used.
Examples of suitable metallocene complexes include bis (n-octadecylcyclopentadienyl) zirconium dichloride, bis (trimethylsilylcyclopentadienyl) zirconium dichloride, bis (tetrahydroindenyl) zirconium dichloride, bis [(t-butyldimethylsilyl). ) Cyclopentadienyl] zirconium dichloride, bis (di-t-butylcyclopentadienyl) zirconium dichloride, (ethylidene-bisindenyl) zirconium dichloride, biscyclopentadienyl zirconium dichloride, etilidenbis (tetrahydroindenyl) zirconium dichloride and Examples thereof include bis [3,3- (2-methyl-benzindenyl)] dimethylsilanediyl zirconium dichloride.
One of these may be used alone, or two or more thereof may be used in combination.
On the other hand, examples of the oxygen-containing organoaluminum compound include methylaluminoxane, ethylaluminoxane, and isobutylaluminoxane. One or one of these may be used alone, or two or more thereof may be used in combination.
Since mPAO has a higher viscosity index than PAO produced using a non-metallocene catalyst (Ziegler catalyst or the like), it has an effect of increasing the viscosity index of the lubricating oil composition.
One type of mPAO may be used alone, or two or more types may be used in combination.

The viscosity index of the high-viscosity base oil (AH) is preferably 100 or more, more preferably 150 or more, still more preferably 170 or more. Further, the viscosity index may be 300 or less, or 250 or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 100 to 300, more preferably 150 to 250, and even more preferably 170 to 250.

Here, the high-viscosity base oil (AH) preferably has a pour point of −20 ° C. or lower. When the pour point of the high-viscosity base oil (AH) is −20 ° C. or lower, the lubricating oil composition containing the high-viscosity base oil (AH) is preferable because it has sufficient fluidity even in a low temperature environment. .. The pour point of the high viscosity base oil (AH) is more preferably −25 ° C. or lower, still more preferably −30 ° C. or lower.

The kinematic viscosity and viscosity index are values measured and calculated in accordance with JIS K 2283: 2000, and the pour point is a value measured in accordance with JIS K 2269: 1987.

In the lubricating oil composition of one aspect of the present invention, the content of the high-viscosity base oil (AH) is preferably 35% by mass or more, more preferably 38% by mass or more, still more preferably, based on the total amount of the lubricating oil composition. It is 40% by mass or more. Further, it is preferably 75% by mass or less, more preferably 72% by mass or less, and further preferably 70% by mass or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 35% by mass to 75% by mass, more preferably 38% by mass to 72% by mass, and further preferably 40% by mass to 70% by mass. When the content of the high-viscosity base oil (AH) is within the above range, the kinematic viscosity of the lubricating oil composition can be maintained high, and a lubricating oil composition having excellent wear resistance and fatigue resistance life can be prepared. can.

As the high-viscosity base oil (AH), one type may be used alone, or two or more types may be used in combination.

(Low viscosity base oil (AL))
The low viscosity base oil (AL) contributes to ensuring the low temperature characteristics of the lubricating oil composition.
Here, from the viewpoint of improving the low temperature characteristics of the lubricating oil composition, the kinematic viscosity of the low-viscosity base oil (AL) at 40 ° C. is preferably 5.0 mm ² / s or more, more preferably 6.0 mm ² / s or more. , More preferably 7.0 mm ² / s or more, and even more preferably 8.0 mm ² / s or more. Further, it is preferably 110 mm ² / s or less, more preferably 90.0 mm ² / s or less, ^{still more preferably 80.0 mm 2} / s or less, ^{still more preferably 75 mm 2} / s or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, preferably ^{^{5.0mm 2 / s ~ 110mm 2 /}} s, more preferably 6.0mm ^² /s~90.0mm ² / s, more preferably 7.0mm ^² /s~80.0mm ² / s, even more preferably a 8.0mm ^² /s~75.0mm ² / s.

Here, the low-viscosity base oil contributes to ensuring the low-temperature characteristics of the lubricating oil composition, but has a lower ignition point than the high-viscosity base oil, lowers the ignition point of the base oil as a whole, and has a lubricating oil composition. It becomes a factor that lowers the ignition point of an object. Therefore, as the low-viscosity base oil (AL), it is preferable to use one having a high flash point among the low-viscosity base oils. From this point of view, low-viscosity base oil (AL) is a low-viscosity poly-α-olefin (hereinafter, also referred to as “PAO”), API (American Petroleum Association) base oil category, and is a group II or III mineral oil, distillation curve. Base oil (preferably ASTM D-) in which the temperature gradient Δ | Dt | of the distillation temperature between the two points of the distillation amount of 2.0% by volume and 5.0% by volume is 6.8 ° C./volume% or less. The saturation content by the Kleegel method measured in accordance with 2007 is 90% by mass or more, and the viscosity content measured in accordance with ASTM D1552 is 0.03% by mass or less, which is obtained in accordance with ASTM D2270. It is preferable to use a base oil having a viscosity index of 120 or more). As the PAO, among the above-mentioned ones, those having a low viscosity can be used.

The temperature gradient in the base oil in which the temperature gradient Δ | Dt | of the distillation temperature between the two points of the distillation amount of 2.0% by volume and 5.0% by volume on the distillation curve is 6.8 ° C./volume% or less. Δ | Dt | is preferably 6.5 ° C./volume% or less, more preferably 6.3 ° C./volume% or less, still more preferably 6.0 ° C./volume% or less, still more preferably 5.0 ° C./% or less. It is less than or equal to the volume.
Further, the temperature gradient Δ | Dt | is usually 0.1 ° C./volume% or more.
The distillation temperature at a distillation amount of 2.0% by volume on the distillation curve is preferably 405 to 510 ° C., more preferably 410 to 500 ° C., still more preferably 415 to 490 ° C., still more preferably 430 to 480 ° C. be.
The distillation temperature at a distillation amount of 5.0% by volume on the distillation curve is preferably 425 to 550 ° C, more preferably 430 to 520 ° C, still more preferably 434 to 500 ° C, still more preferably 450 to 490 ° C. be.
The paraffin content (%) of the base oil in which the temperature gradient Δ | Dt | of the distillation temperature between the two points of the distillation amount of 2.0% by volume and 5.0% by volume on the distillation curve is 6.8 ° C./% by volume or less. The _CP ) is usually 50 or more, preferably 55 or more, more preferably 60 or more, still more preferably 65 or more, still more preferably 70 or more, still more preferably 80 or more, and usually 99 or less.
In this specification, the paraffin component (% _{C P)} means a value measured in conformity with ASTM D-3238 ring analysis (n-d-M method).

The viscosity index of the low-viscosity base oil (AL) is preferably 80 or more, more preferably 90 or more, further preferably 100 or more, still more preferably 110 or more, still more preferably 120 or more, and further. The upper limit is not particularly limited, but is, for example, 200.

In the lubricating oil composition of one aspect of the present invention, the content of the low-viscosity base oil (AL) is from the viewpoint of facilitating the securing of the low temperature characteristics of the lubricating oil composition and suppressing the decrease in the ignition point of the lubricating oil composition. Is preferably 10% by mass or more, more preferably 15% by mass or more, still more preferably 20% by mass or more, based on the total amount of the lubricating oil composition. Further, it is preferably 60% by mass or less, more preferably 55% by mass or less, and further preferably 50% by mass or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 10% by mass to 60% by mass, more preferably 15% by mass to 55% by mass, and further preferably 20% by mass to 50% by mass.

(Other base oil (AZ))
The other base oil (AZ) is not particularly limited, and examples thereof include various base oils that do not correspond to the high-viscosity base oil (AH) and the low-viscosity base oil (AL). From the viewpoint of improvement and the like, ester-based oil is preferable.
As the ester-based oil, a polyol ester is preferably used. The polyol ester may be a partial ester of a polyol or a complete ester, but it is preferable to use a partial ester of the polyol from the viewpoint of sludge solubility.

The polyol used as a raw material for the polyol ester is not particularly limited, but an aliphatic polyol is preferable, for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, neopentyl glycol and the like. Dihydric alcohols; trihydric alcohols such as glycerin, trimethylolethane, trimethylolpropane, etc .; tetrahydric or higher polyhydric alcohols such as diglycerin, triglycerin, pentaerythritol, dipentaerythritol, mannit, sorbit, etc. can be mentioned. ..

As the hydrocarbyl group constituting the polyol ester, an alkyl group or an alkenyl group having 6 to 30 carbon atoms is preferable, an alkyl group or an alkenyl group having 12 to 24 carbon atoms is more preferable, and for example, various hexyl groups and octyl groups. , Decyl group, dodecyl group, tetradecyl group, hexadecyl group, heptadecyl group, octadecyl group, hexenyl group, octenyl group, decenyl group, dodecenyl group, tetradecenyl group, hexadecenyl group, octadecenyl group and the like.
The alkyl group and the alkenyl group may be linear or branched.

Specific examples of the complete ester of the polyol include neopentyl glycol dilaurate, neopentyl glycol dimilistate, neopentyl glycol dipalmitate, neopentyl glycol distearate, neopentyl glycol diisostearate, and trimethyl propantrilau. Rate, Trimethylol Propane Trimilistate, Trimethylol Propane Tripalmitate, Trimethylol Propane Tristearate, Trimethylol Propanetriisostearate, Glycerin Trilaurate, Glycerin Tristearate, Glycerin Triisostearate, etc. However, it is not limited to these.

The partial ester of the polyol is not particularly limited as long as at least one hydroxyl group remains.
Specific examples of the partial ester of the polyol include neopentyl glycol monolaurate, neopentyl glycol monomillistate, neopentyl glycol monopalmitate, neopentyl glycol monostearate, neopentyl glycol monoisostearate, and trimethylolpropane. Mono (or di) laurate, trimethylolpropane mono (or di) millistate, trimethylolpropane mono (or di) palmitate, trimethylolpropane mono (or di) stearate, trimethylolpropane mono (or di) isostearate , Glycerin mono (or di) laurate, glycerin mono (or di) stearate, glycerin mono (or di) isostearate and the like, preferably trimethylolpropane mono (or di) isostearate. However, it is not limited to these.

In the lubricating oil composition of one aspect of the present invention, the content of the other base oil (AZ) is preferably 6% by mass or more based on the total amount of the lubricating oil composition from the viewpoint of further improving sludge solubility. be. Further, it is preferably 15% by mass or less, more preferably 13% by mass or less, and further preferably 11% by mass or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 6% by mass to 15% by mass, more preferably 6% by mass to 13% by mass, and further preferably 6% by mass to 11% by mass.
As the other base oil (AZ), one type may be used alone, or two or more types may be used in combination.

In the lubricating oil composition of one aspect of the present invention, the content of the base oil (A) is preferably 75% by mass or more, more preferably 78% by mass or more, still more preferably, based on the total amount of the lubricating oil composition. Is 80% by mass or more. Further, it is preferably 99.9% by mass or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 75% by mass to 99.9% by mass, more preferably 78% by mass to 99.9% by mass, and further preferably 80% by mass to 99.9% by mass.

Further, in the lubricating oil composition of one aspect of the present invention, when the base oil (A) contains a high-viscosity base oil (AH) and a low-viscosity base oil (AL), the high-viscosity base oil (AH) and the low-viscosity group The total content of the oil (AL) is preferably 75% by mass to 100% by mass, more preferably 78% by mass to 100% by mass, and further preferably 80% by mass to 100% by mass based on the total amount of the base oil (A). %.

Further, in the lubricating oil composition of one aspect of the present invention, when the base oil (A) contains a high-viscosity base oil (AH) and a low-viscosity base oil (AL), the high-viscosity base oil (AH) and the low-viscosity group The content ratio with oil (AL) [(AH) / (AL)] is preferably 50/50 or more in terms of mass ratio. Further, it is preferably 80/20 or less, more preferably 75/25 or less, and further preferably 60/30 or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 80/20 to 50/50, more preferably 75/25 to 50/50, and even more preferably 60/30 to 50/50.

Further, in the lubricating oil composition of one aspect of the present invention, when the base oil (A) contains another base oil (AZ), the total content of the high-viscosity base oil (AH) and the low-viscosity base oil (AL). The ratio [{(AH) + (AL)} / (AZ)] to the content of the other base oil (AZ) is preferably 6/1 or more, more preferably 6.5 / 1 in terms of mass ratio. Above, more preferably 7/1 or more. Further, it is preferably 10/1 or less, more preferably 9.5 / 1 or less, and further preferably 9/1 or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 6/1 to 10/1, more preferably 6.5 / 1 to 9.5 / 1, and even more preferably 7/1 to 9/1.

<Silicone defoamer (B)>
The lubricating oil composition of the present invention contains a silicone-based defoaming agent (B).
However, in the present invention, the content of the silicone-based defoaming agent (B) is significantly reduced from the content of the conventional lubricating oil composition to achieve both long-term defoaming performance and cleanliness. It is possible. That is, although the lubricating oil composition of the present invention contains the silicone-based defoaming agent (B), its content is overwhelmingly smaller than that of the conventional lubricating oil composition.

Specifically, the lubricating oil composition of the present invention is adjusted so that the silicon atom content is 50 mass ppb to 4,000 mass ppb based on the total amount of the lubricating oil composition. The silicone-based defoaming agent (B) is added so that the silicon atom content in the lubricating oil composition satisfies this numerical range.
In other words, in the lubricating oil composition of the present invention, the silicone-based defoaming agent (B) is added so as to have a silicon atom equivalent of 50 mass ppb to 4,000 mass ppb.
In the lubricating oil composition of one aspect of the present invention, the content of the silicone-based defoaming agent (B) in terms of silicon atom is determined from the viewpoint of facilitating the effect of the present invention. Based on the total amount of, preferably 100 mass ppb or more, more preferably 200 mass ppb or more, still more preferably 250 mass ppb or more, still more preferably 300 mass ppb or more, still more preferably 350 mass ppb or more, still more preferably 400. It is added so as to have a mass of ppb or more, more preferably 450 mass ppb or more, and even more preferably 500 mass ppb or more. Further, preferably 3,500 mass ppb or less, more preferably 3,000 mass ppb or less, still more preferably 2,500 mass ppb or less, still more preferably 2,200 mass ppb or less, still more preferably 2,000 mass. It is added so as to be ppb or less, more preferably 1,800 mass ppb or less, even more preferably 1,600 mass ppb or less, and even more preferably 1,500 mass ppb or less.
The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, preferably 100 mass ppb to 3,500 mass ppb, more preferably 200 mass ppb to 3,000 mass ppb, still more preferably 250 mass ppb to 2,500 mass ppb, still more preferably 300 mass ppb. -2,200 mass ppb, even more preferably 350 mass ppb to 2,000 mass ppb, more preferably 400 mass ppb to 1,800 mass ppb, even more preferably 450 mass ppb to 1,600 mass ppb, even more. It is preferably 500 mass ppb to 1,500 mass ppb.

In the lubricating oil composition of one aspect of the present invention, the active ingredient contained in the silicone-based defoaming agent (B) is not particularly limited as long as it is a polymer containing a silicon atom and exhibiting defoaming performance. Examples of such polymers include polydimethylsiloxane, fluorinated polysiloxane, and the like.
One of these may be used alone, or two or more thereof may be used in combination.

The silicone-based defoaming agent (B) is prepared into a solution (dispersion) by adding a diluting oil or the like in consideration of handleability and solubility / dispersibility in the base oil (A), and then the base oil. It is preferable to mix it with (A) and stir to uniformly dissolve and disperse it.

<Additives for lubricating oil>
The lubricating oil composition according to one aspect of the present invention contains additives other than the silicone-based defoaming agent (B) (hereinafter, also referred to as “lubricating oil additives”) as long as the effects of the present invention are not impaired. It may be contained.
Examples of additives for lubricating oil include antioxidants, extreme pressure agents, anti-embroidery agents, rust preventives, viscosity index improvers, pour point lowering agents, metal inactivating agents, ashless cleaning dispersants, and friction modifiers. And so on.
These lubricant additives may be used alone or in combination of two or more.

In addition, in this specification, an additive such as a viscosity index improver may be mixed with other components in the form of a solution dissolved in a diluted oil in consideration of handleability and solubility in a base oil. .. In such a case, in the present specification, the content of the additive such as the viscosity index improver is the content in terms of the active ingredient (converted to the resin content) excluding the diluted oil.
The details of each of the above-mentioned additives for lubricating oil will be described below.

(Antioxidant)
As the antioxidant, amine-based antioxidants, phenol-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, and molybdenum amine complex-based antioxidants used in conventional lubricating oil compositions are used. can do. These antioxidants may be used alone or in combination of two or more.

Examples of the amine-based antioxidant include monoalkyldiphenylamine-based compounds such as monooctyldiphenylamine and monononyldiphenylamine; 4,4'-dibutyldiphenylamine, 4,4'-dipentyldiphenylamine, 4,4'-dihexyldiphenylamine, 4 , 4'-Diheptyldiphenylamine, 4,4'-dioctyldiphenylamine, 4,4'-dinonyldiphenylamine, monobutylphenylmonooctylphenylamine and other dialkyldiphenylamine compounds; tetrabutyldiphenylamine, tetrahexyldiphenylamine, tetraoctyldiphenylamine , Polyalkyldiphenylamine compounds such as tetranonyldiphenylamine; α-naphthylamine, phenyl-α-naphthylamine, butylphenyl-α-naphthylamine, pentylphenyl-α-naphthylamine, hexylphenyl-α-naphthylamine, heptylphenyl-α-naphthylamine, Examples thereof include naphthylamine-based compounds such as octylphenyl-α-naphthylamine and nonylphenyl-α-naphthylamine.

Examples of the phenolic antioxidant include 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, and octadecyl 3- (3,5-di-). Monophenolic compounds such as tert-butyl-4-hydroxyphenyl) propionate; 4,4'-methylenebis (2,6-di-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert- Examples thereof include diphenol compounds such as butylphenol).

Examples of the phosphorus-based antioxidant include triphenylphosphine and the like.
Examples of the sulfur-based antioxidant include 2,6-di-tert-butyl-4- (4,6-bis (octylthio) -1,3,5-triazine-2-ylamino) phenol and phosphorus pentasulfide. Examples thereof include thioterpene compounds such as a reaction product with pinene.
As the molybdenum amine complex-based antioxidant, a hexavalent molybdenum compound, specifically, a compound obtained by reacting molybdenum trioxide and / or molybdic acid with an amine compound can be used.

The content of the antioxidant may be the minimum amount necessary to maintain the oxidative stability, and is preferably 0.01% by mass to 1.5% by mass, more preferably 0.01% by mass, based on the total amount of the lubricating oil composition. It is 0.1% by mass to 1% by mass.

(Extreme pressure agent)
As the extreme pressure agent, an organic metal-based extreme pressure agent, a sulfur-based extreme pressure agent, a phosphorus-based extreme pressure agent, and a sulfur-phosphorus-based extreme pressure agent, which are used in conventional lubricating oil compositions, can be used. .. These extreme pressure agents may be used alone or in combination of two or more.

Examples of the organic metal-based extreme pressure agent include organic molybdenum compounds such as molybdenum dialkyldithiocarbamate (MoDTC) and molybdenum dialkyldithiophosphate (MoDTP), zinc dialkyldithiophosphate (ZnDTC) and zinc dialkyldithiophosphate (ZnDTP), and the like. Organic zinc-based compounds can be mentioned.

Examples of sulfur-based extreme pressure agents include sulfide fats and oils, sulfide fatty acids, sulfide esters, sulfide olefins, monosulfide, polysulfide, dihydrocarbyl sulfide, thiadiazol compounds, alkylthiocarbamoyl compounds, thiocarbamate compounds, thioterpene compounds, and dialkylthiodipropio. Nate compounds can be mentioned.

Examples of phosphorus-based extreme pressure agents include phosphoric acid esters such as aryl phosphate, alkyl phosphate, alkenyl phosphate, and alkyl aryl phosphate; monoaryl acid phosphate, diallyl acid phosphate, monoalkyl acid phosphate, dialkyl acid phosphate, and monoalkenyl acid phosphate. , Acidic phosphates such as dialkenyl acid phosphate; Hypophosphates such as arylhydrogen phosphite, alkylhydrogen phosphite, aryl phosphite, alkyl phosphite, alkenyl phosphite, arylalkyl phosphite; monoalkyl acid phosphite. , Acid subphosphates such as dialkyl acid phosphite, monoalkenyl acid phosphite, dialkenyl acid phosphite; and amine salts thereof.

Examples of the sulfur-phosphorus extreme pressure agent include monoalkyl thiophosphate, dialkyl dithiophosphate, trialkyl trithiophosphate, amine salts thereof, and zinc dialkyl dithiophosphate (Zn-DTP).

The content of the extreme pressure agent is preferably 0.1% by mass to 10% by mass, more preferably 0.5% by mass to 8.0% by mass, based on the total amount of the lubricating oil composition from the viewpoint of the addition effect. More preferably, it is 1.0% by mass to 6.0% by mass.

(Anti-emulsifier)
Anti-emulsifiers include, for example, quaternary ammonium salts, cationic surfactants such as imidazolines; polyoxyalkylene block polymers (ethylene oxide (EO) -propylene oxide (PO) block copolymers, etc.), polyoxyalkylene glycols, and Polyoxyalkylene polyglycol; alkylene oxide adduct of alkylphenol-formaldehyde polycondensate and the like can be mentioned.
The content of the anti-emulsifier is preferably 0.001% by mass to 0.5% by mass, more preferably 0.002% by mass to 0.2% by mass, based on the total amount of the lubricating oil composition.

(anti-rust)
Examples of the rust preventive agent include metal sulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate, organic phosphite ester, organic phosphate ester, organic sulfonic acid metal salt, organic phosphate metal salt, alkenyl succinate, and polyhydric alcohol. Examples thereof include esters and benzotriazole-based compounds.
The content of the rust preventive is preferably 0.01% by mass to 10.0% by mass, more preferably 0.05% by mass to 5.0% by mass, based on the total amount of the lubricating oil composition.

(Viscosity index improver)
Examples of the viscosity index improver include polymethacrylate (PMA), dispersed polymethacrylate, olefin-based copolymer (olefin copolymer (OCP); for example, ethylene-propylene copolymer, etc.), and dispersed olefin-based copolymer. , Styrene-based copolymer (for example, styrene-diene hydride copolymer, etc.) and the like.
From the viewpoint of the effect of addition, the amount of these viscosity index improvers added is preferably 1% by mass to 10% by mass, more preferably 2% by mass to 8% by mass, based on the total amount of the lubricating oil composition.
Further, the lubricating oil composition of one aspect of the present invention preferably contains at least an olefin copolymer as these viscosity index improvers, and the content of the olefin copolymer is preferably based on the total amount of the lubricating oil composition. It is 1% by mass to 10% by mass, and more preferably 2% by mass to 8% by mass.

(Pour point depressant)
Examples of the pour point lowering agent include a polymer such as an ethylene-vinyl acetate copolymer, a condensate of chlorinated paraffin and naphthalene, a condensate of chlorinated paraffin and phenol, polymethacrylate, and polyalkylstyrene. .. The weight average molecular weight (Mw) of these polymers is preferably 50,000 to 150,000.
The content of the pour point lowering agent is preferably 0.01% by mass to 5.0% by mass, more preferably 0.02% by mass to 2.0, based on the total amount of the lubricating oil composition from the viewpoint of the addition effect. It is mass%.

(Metal inactivating agent)
Examples of the metal inactivating agent include benzotriazole-based compounds, tolyltriazole-based compounds, thiadiazole-based compounds, imidazole-based compounds, pyrimidine-based compounds and the like.
The content of the metal inactivating agent is preferably 0.01% by mass to 5.0% by mass, more preferably 0.02% by mass to 3.0, based on the total amount of the lubricating oil composition from the viewpoint of the addition effect. It is mass%.

(Ashless cleaning dispersant)
Examples of the ashless cleaning dispersant include monovalent or divalent succinic acid imides, boron-containing succinic acid imides, benzylamines, boron-containing benzylamines, succinic acid esters, fatty acids or succinic acid. Examples thereof include carboxylic acid amides.
The content of the ashless cleaning dispersant is preferably 0.01% by mass to 5.0% by mass, more preferably 0.02% by mass to 3.0, based on the total amount of the lubricating oil composition from the viewpoint of the addition effect. It is mass%.

(Friction modifier)
Examples of the friction modifier include ashless friction modifiers such as aliphatic amines, aliphatic alcohols and aliphatic ethers having at least one alkyl group or alkenyl group having 6 to 30 carbon atoms in the molecule. ..
The content of the friction modifier is preferably 0.01% by mass to 5.0% by mass based on the total amount of the lubricating oil composition.

[Physical characteristics of lubricating oil composition]
<Silicon atom content>
The lubricating oil composition of the present invention is required to have a silicon atom content of 50 mass ppb to 4,000 mass ppb based on the total amount of the lubricating oil composition.
If the silicon atom content is less than 50 mass ppb, long-term defoaming performance cannot be ensured. Further, if the silicon atom content exceeds 4,000 mass ppb, cleanliness cannot be ensured.
Here, in the lubricating oil composition of one aspect of the present invention, the content of silicon atoms is preferably 100 mass ppb or more based on the total amount of the lubricating oil composition from the viewpoint of facilitating the effect of the present invention. , More preferably 200 mass ppb or more, still more preferably 250 mass ppb or more, even more preferably 300 mass ppb or more, still more preferably 350 mass ppb or more, still more preferably 400 mass ppb or more, still more preferably 450 mass ppb or more. The above is even more preferably 500 mass ppb or more. Further, preferably 3,500 mass ppb or less, more preferably 3,000 mass ppb or less, still more preferably 2,500 mass ppb or less, still more preferably 2,200 mass ppb or less, still more preferably 2,000 mass. It is ppb or less, more preferably 1,800 mass ppb or less, even more preferably 1,600 mass ppb or less, and even more preferably 1,500 mass ppb or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, preferably 100 mass ppb to 3,500 mass ppb, more preferably 200 mass ppb to 3,000 mass ppb, still more preferably 250 mass ppb to 2,500 mass ppb, still more preferably 300 mass ppb. -2,200 mass ppb, even more preferably 350 mass ppb to 2,000 mass ppb, still more preferably 400 mass ppb to 1,800 mass ppb, even more preferably 450 mass ppb to 1,600 mass ppb, even more. It is preferably 500 mass ppb to 1,500 mass ppb.
The silicon atom content in the lubricating oil composition can be measured by an inductively coupled plasma atomic emission spectrometer (ICP). When no silicon atom other than the silicon atom derived from the silicone-based defoaming agent (B) is present in the lubricating oil composition, the silicon atom content in the lubricating oil composition is determined by the silicone-based defoaming agent (B). It can also be theoretically calculated from the content (in terms of solid content) and the content of silicon atoms contained in the silicone-based defoaming agent (B).

<Kinematic viscosity, viscosity index>
The 40 ° C. kinematic viscosity of the lubricating oil composition of one aspect of the present invention is preferably 10 mm ² / s to 500 mm ² / s, more preferably 30 mm ² / s to 450 mm ² / s, ^{still more preferably 50 mm 2} / s to. It is 400 mm ² / s.
The viscosity index of the lubricating oil composition according to one aspect of the present invention is preferably 100 or more, more preferably 110 or more, still more preferably 120 or more.
In this specification, the 40 ° C. kinematic viscosity and the viscosity index mean values measured and calculated in accordance with JIS K2283: 2000.

[Manufacturing method of lubricating oil composition]
The method for producing the lubricating oil composition of the present invention is not particularly limited.
For example, the method for producing a lubricating oil composition according to one aspect of the present invention includes a step of mixing the base oil (A) and the silicone-based defoaming agent (B), and the silicon atom content is the lubricating oil composition. This is a method for producing a lubricating oil composition, which is adjusted so as to have a total amount of 50 mass ppb to 4,000 mass ppb.
The method for mixing each of the above components is not particularly limited, and examples thereof include a method having a step of blending the silicone-based defoaming agent (B) with the base oil (A). Additives (additives for lubricating oil) other than the silicone-based defoaming agent (B) may be blended at the same time as the silicone-based defoaming agent (B), or may be blended separately. The silicone-based defoaming agent (B) and other additives (additives for lubricating oil) may be blended after adding a diluting oil or the like to form a solution (dispersion). After blending each component, it is preferable to stir and uniformly disperse by a known method.

[Use of lubricating oil composition]
The lubricating oil composition of the present invention is a lubricating oil composition excellent in both long-term defoaming performance and cleanliness. Therefore, it can be widely used in lubrication applications that require long-term defoaming performance and cleanliness.
For example, it can be suitably used as a speed increasing machine oil for a wind turbine, a hydraulic hydraulic oil, a compressor oil, a gear oil, a cutting oil, a machine tool oil, a refrigerating machine oil, a turbine oil, an internal combustion machine oil, a transmission oil, or an axle unit oil for an automobile. ..
Therefore, in one aspect of the invention, the following methods are provided.
-The lubricating oil composition of the present invention can be applied to a speed-up machine oil for a wind turbine, a hydraulic hydraulic oil, a compressor oil, a gear oil, a cutting oil, a machine tool oil, a refrigerating machine oil, a turbine oil, an internal combustion machine oil, a transmission oil, or an automobile axle unit. How to use as oil.

[Aspect of the present invention provided]
In one aspect of the present invention, the following [1] to [8] are provided.
[1] A lubricating oil composition containing a base oil (A) and a silicone-based defoaming agent (B).
A lubricating oil composition having a silicon atom content of 50 mass ppb to 4,000 mass ppb based on the total amount of the lubricating oil composition.
[2] The lubricating oil composition according to [1], wherein the base oil (A) is at least one selected from the group consisting of synthetic oils (A1) and mineral oils (A2).
[3] The lubricating oil composition according to [1], wherein the base oil (A) is two or more kinds selected from the group consisting of synthetic oils (A1) and mineral oils (A2).
[4] The lubrication according to [1], wherein the base oil (A) is selected from the group consisting of synthetic oil (A1) and mineral oil (A2), and has two or more kinds having different kinematic viscosities at 40 ° C. Oil composition.
[5] The total content of the base oil (A) and the silicone-based defoaming agent (B) is 75% by mass or more and 94.9% by mass or less based on the total amount of the lubricating oil composition [1]. ] To [4].
[6] The lubricating oil according to any one of [1] to [5], wherein the silicone-based defoaming agent (B) contains at least one selected from the group consisting of polydimethylsiloxane and fluorinated polysiloxane. Composition.
[7] Further, from the group consisting of antioxidants, extreme pressure agents, anti-emulsifiers, rust preventives, viscosity index improvers, flow point lowering agents, metal deactivators, ashless cleaning dispersants, and friction modifiers. The lubricating oil composition according to any one of [1] to [6], which comprises one or more selected additives for lubricating oil.
[8] Used as a speed-up machine oil for wind turbines, hydraulic hydraulic oil, compressor oil, gear oil, cutting oil, machine tool oil, refrigerating machine oil, turbine oil, internal combustion machine oil, transmission oil, or axle unit oil for automobiles [1] ] To [7].

The present invention will be specifically described with reference to the following examples, but the present invention is not limited to the following examples.

[Measurement method of various physical property values]
(1) Dynamic viscosity and viscosity index of base oil and lubricating oil composition Measured and calculated in accordance with JIS K2283: 2000.
(2) Paraffin content (% C _p )
It was determined according to ASTM D-3238 ring analysis (nd-M method).

[Examples 1 to 4, Comparative Examples 1 to 4]
The base oil (A) and the silicone-based defoaming agent (B) shown below are sufficiently mixed in the blending amounts (mass%) shown in Table 1 to form the lubricating oil compositions of Examples 1 to 3 and Comparative Examples 1 and 2. The thing was prepared.
Further, the base oil (A), the silicone-based defoaming agent (B), and the additive for lubricating oil shown below are sufficiently mixed in the blending amounts (mass%) shown in Table 2, and Examples 4 and Comparative Examples are used. 3-4 lubricating oil compositions were prepared.

<Base oil (A)>
(High viscosity base oil (AH))
High-viscosity base oil (AH) -1: Poly-α-olefin (PAO), 40 ° C. kinematic viscosity = 1,240 mm ² / s, viscosity index = 170
High-viscosity base oil (AH) -2: Decene oligomer (mPAO) obtained by polymerizing 1-decene using a metallocene catalyst, 40 ° C kinematic viscosity = 1,616 mm ² / s, viscosity index = 202
(Low viscosity base oil (AL))
Low-viscosity base oil (AL) -1: C40-based poly-α-olefin (PAO), 40 ° C. kinematic viscosity = 28.8 mm ² / s, viscosity index = 136
-Low viscosity base oil (AL) -2: Mineral oil classified into Group II by API classification, 40 ° C kinematic viscosity = 30.6 mm ² / s, viscosity index = 104
Low-viscosity base oil (AL) -3: The saturation content by the Kleegel method measured according to ASTM D-2007 is 90% by mass or more, and the sulfur content measured according to ASTM D1552 is 0.03. or less by mass%, base oil viscosity index obtained in conformity with ASTM D2270 of 120 or more, 40 ° C. kinematic viscosity = 43.75mm ² / s, viscosity index = 143, paraffins _(% C P) = 94 .1
The low-viscosity base oil (AL) -3 is a base oil prepared by the following method.
<Manufacturing method>
The raw material oil, which is a distillate oil of 200 neutral or more, is subjected to a hydrogenation isomerization dewaxing treatment and then a hydrofinishing treatment, and then the 5% by volume fraction of the distillation curve is 460 ° C. or higher. Distillation was carried out at such a distillation temperature, ^{and a fraction having a kinematic viscosity at 40 ° C. in the range of 19.8 to 50.6 mm 2} / s was recovered to prepare a low-viscosity base oil (AL) -3.
The conditions for the hydrogenation isomerization dewax treatment are as follows.
^{-Hydrogen gas supply ratio: 300-400 Nm 3} for 1 kiloliter of raw material oil to be supplied
・ Hydrogen partial pressure: 10 to 15 MPa
-Liquid spatiotemporal velocity (LHSV): 0.5 to 1.0 hr ^-1
-Reaction temperature: 300-350 ° C
The various properties of the obtained low-viscosity base oil (AL) -3 were as follows.
-Distillation temperature at a distillation amount of 2.0% by volume: 451.0 ° C.
-Distillation temperature with a distillation amount of 5.0% by volume: 464.0 ° C.
-Temperature gradient Δ | Dt | = 4.3 ° C / volume%
The distillation temperature at the distillation amounts of 2.0% by volume and 5.0% by volume was measured by distillation gas chromatography in accordance with ASTM D6352.
(Other base oil (AZ))
-Ester oil: Ester of trimethylolpropane and isostearic acid (molar ratio 1: 2), 40 ° C. kinematic viscosity = 106.7 mm ² / s, viscosity index = 124

<Silicone defoamer (B)>
A silicone-based defoaming agent having an active ingredient concentration of 0.2% by mass was used.
The active ingredient is polydimethylsiloxane, and the silicon atom content of polydimethylsiloxane is 0.081% by mass based on the total amount of the silicone-based defoaming agent.
The silicone-based antifoaming agent (B) was diluted with light oil to obtain a diluted product, and then blended with the base oil (A). Tables 1 and 2 show the content of the silicone-based defoamer (B) in the diluted product of the silicone-based defoamer (B) (based on the total amount of the lubricating oil composition) and the silicone-based defoamer (B). The content of the light oil used for dilution (based on the total amount of the lubricating oil composition) is shown.

<Additives for lubricating oil>
-Phenolic antioxidant: octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate.
-Amine-based antioxidant: monobutylphenyl monooctylphenylamine.
Dihydrocarbyl sulfide: a mixture of di-tert-butyl disulfide and di-tert-butyl trisulfide, S content = 38.5%.
-Alkylthiophosphate: Tris [2,4-isoalkyl (C ₉ , C ₁₀ ) phenyl] thiophosphate.
-Alkylthiocarbamate: Methylenebis (dibutyldithiocarbamate), S content = 30.3%.
-Alkylbenzotriazole: N-dialkylaminomethylbenzotriazole (N = 14.6%).
-Acid phosphate: Isodecyl acid phosphate.
-Alkylamine: Trioctylamine.
EO-PO copolymer: xylene solution of EO-PO block copolymer (10%)
-Iconide alkenyl succinimide: A mixture of 50% imide polybutenyl succinimide, 20% polybutene and 30% mineral oil (base value; 37 mgKOH / g).
-OCP: Ethylene propylene oligomer.

[evaluation]
The following tests were performed on the prepared lubricating oil compositions.

<Evaluation of foaming>
Air blowing was started at 60 ° C. by a method according to JIS K 2518: 2003, and the volume of bubbles was measured after 1 day (1440 minutes) and 2 days (2880 minutes), respectively.
In the foaming test, those having a foaming amount of 50 mL or less after 1440 minutes and 2880 minutes were accepted as (A), and those having at least one of the foaming amounts of more than 50 mL after 1440 minutes and 2880 minutes were rejected. It was designated as (F).

<Cleanliness evaluation>
The cleanliness of the lubricating oil composition was evaluated using the pollution degree code according to ISO4406: 1999.
Specifically, the sampled lubricating oil composition was measured with a particle counter to obtain a contamination degree code. The pollution degree code divides the number of particles of the sampled lubricating oil composition into a particle size range of 4 μm or more, 6 μm or more, and 14 μm or more, and the scale number (0 to 28) assigned from the number of particles in 1 mL is shaded. Classified by (/), "scale number of 4 μm or more particles (in 1 mL)" / "scale number of 6 μm or more particles (in 1 mL)" / "scale number of 14 μm or more particles (in 1 mL)" I got. The larger the contamination code, the larger the number of particles and the lower the cleanliness.
In this embodiment, the "scale number of the number of particles of 6 μm or more (in 1 mL)" is 15 or less (the number of particles: 320 counts / 1 mL or less), and the "scale number of the number of particles of 14 μm or more (in 1 mL)". The lubricating oil composition having a value of 12 or less (number of particles: 40 counts / 1 mL or less) was regarded as acceptable (A).
In addition, the "scale number of the number of particles of 6 μm or more (in 1 mL)" is 16 or more (number of particles: 320 counts / more than 1 mL), or the "scale number of the number of particles of 14 μm or more (in 1 mL)" is , 13 or more (number of particles: 40 counts / more than 1 mL) was rejected (F).

The evaluation results are shown in Tables 1 and 2.
The "silicon atom content in the lubricating oil composition" in Tables 1 and 2 is a value obtained by calculation based on the silicon atom content in the silicone-based defoaming agent (B).

From Table 1, the following can be seen.
In Examples 1 to 3 in which the silicon atom content in the lubricating oil composition is in the range of 50 mass ppb to 4,000 mass ppb, it can be seen that both long-term defoaming performance and cleanliness are compatible.
On the other hand, in Comparative Example 1 in which the silicon atom content in the lubricating oil composition is less than 50 mass ppb, it can be seen that the long-term defoaming performance cannot be ensured.
Further, it can be seen that the cleanliness cannot be ensured in Comparative Example 2 in which the silicon atom content in the lubricating oil composition is more than 4,000 mass ppb.

Further, the same as above can be seen from the evaluation results of Table 2 in which an additive for lubricating oil other than the silicone-based defoaming agent (B) is also blended in the lubricating oil composition.
That is, in Example 4 in which the silicon atom content in the lubricating oil composition is in the range of 50 mass ppb to 4,000 mass ppb, it can be seen that both long-term defoaming performance and cleanliness are compatible.
On the other hand, in Comparative Example 3 in which the silicon atom content in the lubricating oil composition is less than 50 mass ppb, it can be seen that the long-term defoaming performance cannot be ensured.
Further, it can be seen that the cleanliness cannot be ensured in Comparative Example 4 in which the silicon atom content in the lubricating oil composition is more than 4,000 mass ppb.

Claims

A lubricating oil composition containing a base oil (A) and a silicone-based defoaming agent (B).
A lubricating oil composition having a silicon atom content of 50 mass ppb to 4,000 mass ppb based on the total amount of the lubricating oil composition.
The lubricating oil composition according to claim 1, wherein the base oil (A) is at least one selected from the group consisting of synthetic oils (A1) and mineral oils (A2).
The lubricating oil composition according to claim 1, wherein the base oil (A) is two or more kinds selected from the group consisting of synthetic oil (A1) and mineral oil (A2).
The lubricating oil composition according to claim 1, wherein the base oil (A) is selected from the group consisting of a synthetic oil (A1) and a mineral oil (A2), and has two or more kinds having different kinematic viscosities at 40 ° C. ..
Claims 1 to 4 indicate that the total content of the base oil (A) and the silicone-based defoaming agent (B) is 75% by mass or more and 94.9% by mass or less based on the total amount of the lubricating oil composition. The lubricating oil composition according to any one of the above items.
The lubricating oil composition according to any one of claims 1 to 5, wherein the silicone-based defoaming agent (B) contains at least one selected from the group consisting of polydimethylsiloxane and fluorinated polysiloxane.
Further, it is selected from the group consisting of antioxidants, extreme pressure agents, anti-emulsifiers, rust inhibitors, viscosity index improvers, flow point lowering agents, metal deactivators, ashless cleaning dispersants, and friction modifiers. The lubricating oil composition according to any one of claims 1 to 6, which comprises one or more kinds of additives for lubricating oil.
Claims 1 to 7 used as an accelerator oil for a wind turbine, a hydraulic hydraulic oil, a compressor oil, a gear oil, a cutting oil, a machine tool oil, a refrigerating machine oil, a turbine oil, an internal combustion engine oil, a transmission oil, or an automobile axle unit oil. The lubricating oil composition according to any one of the above items.