TW202200769A - Lubricating oil composition - Google Patents

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 lubricating oil compositions.

Background technique Lubricating oil composition is responsible for friction reduction, sealing, rust/corrosion prevention, cooling and power transmission in various mechanical devices, and is widely used in various fields. However, the lubricating oil composition may foam due to air entrainment or the like when the mechanical device is in operation. Foaming of the lubricating oil composition leads to a decrease in lubricating performance, a decrease in sealing performance, accelerated oxidative deterioration, a decrease in cooling efficiency, a decrease in power transmission efficiency, and the like. Therefore, in order to prevent foaming, an antifoaming agent is prepared in the lubricating oil composition. As a representative example of the antifoaming agent formulated in a lubricating oil composition, a polysiloxane type antifoaming agent is known (for example, refer patent documents 1 and 2). prior art literature Patent Literature

[Patent Document 1] Japanese Patent Application Laid-Open No. 2020-026447 [Patent Document 2] Japanese Patent Laid-Open No. 2017-066220

Summary of Invention The problem to be solved by the invention However, as a result of studies conducted by the present inventors, it was found that the polysiloxane-based antifoaming agent can impart antifoaming performance to the lubricating oil composition for a long period of time, but it has a problem of causing deterioration of the cleanliness of the lubricating oil composition. Furthermore, in the present invention, the cleanliness of the lubricating oil composition refers to the cleanliness evaluated by the pollution degree code of ISO4406:1999.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide a lubricating oil composition which is excellent in both long-term defoaming performance and cleanliness even though a polysiloxane-based antifoaming agent is formulated. means of solving problems

As a result of repeated studies, the present inventors found that the above-mentioned problems can be solved by adjusting the silicon atom content of the lubricating oil composition prepared with the polysiloxane-based antifoaming agent within a specific range.

That is, the present invention relates to the following [1]. [1] A lubricating oil composition comprising a base oil (A) and a polysiloxane-based antifoaming agent (B), and based on the total amount of the lubricating oil composition, the content of silicon atoms is 50 mass ppb ~4,000 quality ppb. Invention effect

According to the present invention, it is possible to provide a lubricating oil composition which is excellent in both long-term defoaming performance and cleanliness even though a polysiloxane-based antifoaming agent is formulated.

Form for carrying out the invention In the present specification, the lower limit value and the upper limit value described in stages with respect to 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", "preferable lower limit value (10)" and "preferable upper limit value (60)" can be combined to obtain "10~60". In this specification, the numerical value of an Example is a numerical value which can be used as an upper limit value or a lower limit value. In this specification, unless otherwise specified, the numerical range represented by "AA~BB" means "AA or more and BB or less".

[Aspect of the lubricating oil composition of the present invention] The lubricating oil composition of the present invention contains a base oil (A) and a polysiloxane-based defoaming agent (B), and based on the total amount of the lubricating oil composition, the silicon atom content is 50 mass ppb to 4,000 mass ppb ppb.

The present inventors conducted research in order to provide a lubricating oil composition excellent in both the long-term defoaming performance and the cleanliness of a polysiloxane-based antifoaming agent. First, the present inventors conducted various studies on the reasons for the deterioration of the cleanliness of the lubricating oil composition containing the polysiloxane-based antifoaming agent. The results are clear: if the amount of polysiloxane-based antifoaming agent previously assumed to be necessary to maintain the defoaming performance (about 1% by mass based on the total amount of the lubricating oil composition, converted into The silicon atom is about 10 mass ppm), the cleanliness evaluated according to ISO4406:1999 deteriorates and does not satisfy this standard. The reasons for this were investigated in detail. As a result, it was found that in ISO4406:1999, the distribution of pollutants in the sample is calculated by calculating the fine particles in the sample. Therefore, it is likely that polysiloxane, which is an active ingredient of polysiloxane-based defoamer, is used. Oxygen particles were measured as fine particles, and as a result, the cleanliness evaluated according to ISO4406:1999 deteriorated, and the standard was not satisfied. Based on the above-mentioned problems, the present inventors conducted further studies, and as a result, unexpectedly found that long-term defoaming performance can be ensured even if the compounding amount of the polysiloxane-based antifoaming agent is greatly reduced. Furthermore, by greatly reducing the preparation amount of the polysiloxane-based defoamer, the number of polysiloxane particles is reduced and the cleanliness is also improved. Therefore, the present inventors investigated the content of the polysiloxane-based antifoaming agent, and as a result, found a range that can be used as a lubricating oil composition excellent in both growth-term defoaming performance and cleanliness, and finally completed the present invention.

In addition, in the following description, "base oil (A)" and "polysiloxane-based antifoaming agent (B)" are also called "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 may contain other components other than the component (A) and the component (B) within a range that does not impair the effects of the present invention. Element. In the lubricating oil composition of one aspect of the present invention, based on the total amount of the lubricating oil composition, the total content of component (A) and component (B) is preferably 75% by mass or more, preferably 80% by mass % or more, more preferably 85% by mass or more. Furthermore, the upper limit of the total content of components (A) and (B) can be adjusted in consideration of the balance with other components other than components (A) and (B), and the total amount of the lubricating oil composition is On a basis, it is preferably 94.9 mass % or less, more preferably 94 mass % or less, still more preferably 92 mass % or less, and particularly preferably 90 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), the base oil previously used as a lubricating oil base oil can be used without particular limitation, and, for example, at least one selected from the group consisting of mineral oil and synthetic oil can be used.

As for the mineral oil, for example, atmospheric residual oil obtained by subjecting crude oil such as paraffinic crude oil, intermediate base crude oil, or naphthenic crude oil to atmospheric distillation; such atmospheric residual oil obtained by vacuum distillation Distillate oil: Mineral oil obtained by subjecting the distillate to one or more refining treatments such as solvent deasphalting, solvent extraction, hydrolysis, solvent dewaxing, contact dewaxing, and hydrorefining. Mineral oils may be used alone or in combination of two or more.

The synthetic oil includes, for example, hydrocarbon oil, aromatic oil, ester oil, ether oil, and the temperature gradient Δ of the distillation temperature between two points in the distillation curve of 2.0% by volume and 5.0% by volume. |Dt| is a base oil of 6.8°C/vol % or less (preferably, the saturated content by the Clay-Gel method measured according to ASTM D-2007 is 90 mass % or more, and the sulfur content measured according to ASTM D1552 is 90% by mass or more 0.03 mass % or less, a base oil having a viscosity index of 120 or more according to ASTM D2270) and the like. In addition, in this specification, the temperature gradient Δ|Dt| of the distillation temperature between two points of the distillation curve of 2.0 vol % and 5.0 vol % means the value calculated by the following formula. ･Temperature gradient Δ|Dt|(℃/vol%)=|[distillation temperature at which the distillate of base oil is 5.0% by volume (℃)] - [distillation temperature at which the distillate of base oil is 2.0% by volume (℃) )]|/3.0 (vol%) The "distillation temperature at which the distillate of the base oil becomes 5.0% by volume and 2.0% by volume" in the above formula is the value measured by the method according to ASTM D6352, specifically The value measured by the method described in the Example. The temperature gradient Δ|Dt| is preferably 6.5°C/vol% or less, preferably 6.3°C/vol% or less, more preferably 6.0°C/vol% or less, and even more preferably 5.0°C/vol% or less. In addition, the above-mentioned temperature gradient Δ|Dt| is usually 0.1° C./volume % or more. The distillation temperature at 2.0 vol % of the distillate in the distillation curve is preferably 405 to 510°C, more preferably 410 to 500°C, still more preferably 415 to 490°C, and particularly preferably 430 to 480°C. The distillation temperature at 5.0% by volume of the distillate in the distillation curve is preferably 425 to 550°C, more preferably 430 to 520°C, still more preferably 434 to 500°C, and particularly preferably 450 to 490°C. In addition, the temperature gradient Δ|Dt| about the distillation temperature between the two points of the distillation curve of 2.0 vol% and 5.0 vol% is 6.8°C/vol% or less of the paraffin component (%C _P ), 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, particularly preferably 80 or more, and usually 99 or less. In addition, in this specification, the paraffin component (%C _P ) means the value measured according to ASTM D-3238 ring analysis (ndM method). Here, the temperature gradient specified in the above-mentioned requirements takes into account the state of the base oil such as the content of the light component and the structure of the wax component, which cannot be removed even by performing one or more of the above-mentioned purification steps. The parameter related to the flash point of the lubricating oil composition can be accurately determined because the variation of the distillation curve is stable when the distillate amount is 2.0 to 5.0% by volume, and it is in the temperature region where the light components also remain. The state of the light component and wax component of the base oil was evaluated. One type of synthetic oil may be used alone, or two or more types may be used in combination.

Furthermore, in the lubricating oil composition of one aspect of the present invention, the base oil (A) may be one selected from mineral oils, one selected from synthetic oils, or may be easily selected from among them. One of the sparkling mineral oils. Moreover, the base oil (A) may be a mixed base oil obtained by mixing two or more kinds selected from the group consisting of mineral oil and synthetic oil. The base oil used in the lubricating oil composition may be a mixed base oil obtained by mixing two or more kinds of base oils from the viewpoint of improving various properties 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. In the present invention, a lubricating oil composition excellent in both long-term defoaming performance and cleanliness can be provided even for such a mixed base oil which is particularly prone to foaming. Furthermore, the two or more base oils may be a combination of two or more base oils with different oil types, or may be two or more base oils with the same oil type but different physical properties (for example, kinematic viscosity at 40°C, etc.). combination of oils. Furthermore, a combination of two or more base oils having the same oil type but different physical properties (eg, kinematic viscosity at 40° C.), and one or more base oils different from the oil type and the base oil may be used.

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. In addition to the high-viscosity base oil (AH) and the low-viscosity base oil (AL), a mixed base oil in which other base oils (AZ) are further combined may be used. Hereinafter, high-viscosity base oil (AH), low-viscosity base oil (AL), and other base oils (AZ) will be described.

(High-viscosity base oil (AH)) High-viscosity base oil (AH) helps to improve the wear resistance and fatigue life of lubricating oil compositions by maintaining the kinematic viscosity of the base oil (A) at a high level. Here, the kinematic viscosity at 40°C (hereinafter also referred to as "40°C kinematic viscosity") of the high-viscosity base oil (AH) is preferable from the viewpoint of more easily improving the wear resistance and fatigue life of the lubricating oil composition. It is 1,000 mm ² /s or more, preferably 1,100 mm ² /s or more, and more preferably 1,200 mm ² /s or more. Further, the upper limit value 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, it is preferably 1,000 mm ² /s to 2,000 mm ² /s, more preferably 1,100 mm ² /s to 2,000 mm ² /s, and still more preferably 1,200 mm ² /s to 2,000 mm ² /s.

From the viewpoint of high-viscosity indexing of lubricating oil compositions, the high-viscosity base oil (AH) is preferably poly-alpha-olefin (hereinafter also referred to as "PAO"). As for PAO, for example, polybutene, polyisobutylene, 1-decene oligomer, ethylene-propylene copolymer, etc., and hydrogenated products of these are mentioned. PAO may be used alone or in combination of two or more.

In addition, from the viewpoint of further increasing the viscosity index of the lubricating oil composition, the high-viscosity base oil (AH) is more preferably a poly-α-olefin obtained by using a metallocene catalyst (hereinafter also referred to as "mPAO") as for the PAO. . As the raw material of mPAO, it is preferable to use one of α-olefins having 8 to 12 carbon atoms alone or in combination of two or more, and it is a poly-α-olefin obtained by producing (polymerizing) it in the presence of a metallocene catalyst. Alkenes or their hydrides. The α-olefin having 8 to 12 carbon atoms used as the raw material of mPAO may be linear or branched, but a linear α-olefin is preferably used, for example, 1-octene, 1-nonene , 1-decene, 1-undecene, 1-dodecene, preferably a decene oligomer obtained by polymerizing using 1-decene as a raw material. As a metallocene catalyst as a polymerization catalyst for producing mPAO, a complex compound having a five-membered ring with conjugated carbon containing an element of Group IV of the periodic table, that is, a metallocene complex and an oxygen-containing organoaluminum compound can be combined Use after combination. Regarding the elements of the fourth group of the periodic table in the aforementioned metallocene complex, titanium, zirconium and hafnium can be used, and zirconium is preferred. In addition, as a complex having a five-membered conjugated carbon ring, a complex having a substituted or unsubstituted cyclopentadienyl ligand is generally used. Examples of preferable metallocene complexes include bis(n-octadecylcyclopentadienyl)zirconium dichloride, bis(trimethylsilylcyclopentadienyl)zirconium dichloride, Bis(tetrahydroindenyl)zirconium dichloride, bis[(tert-butyldimethylsilyl)cyclopentadienyl]zirconium dichloride, bis(di-tert-butylcyclopentadienyl) Zirconium dichloride, (ethylene-bisindenyl)zirconium dichloride, biscyclopentadienylzirconium dichloride, ethylenebis(tetrahydroindenyl)zirconium dichloride and bis[3,3- (2-methyl-benzoindenyl)] dimethylsilanediyl zirconium dichloride, etc. These may be used individually by 1 type, and may be used in combination of 2 or more types. On the other hand, as for the said oxygen-containing organoaluminum compound, methylaluminoxane, ethylaluminoxane, isobutylaluminoxane, etc. are mentioned, for example. These may be used individually by 1 type, and may be used in combination of 2 or more types. Since mPAO has a higher viscosity index than PAO produced by using a non-metallocene catalyst (Ziegler catalyst, etc.), it has the effect of increasing the viscosity index of the lubricating oil composition. mPAO may be used alone or in combination of two or more.

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

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

In addition, the said kinematic viscosity and viscosity index are the values measured and calculated based on JIS K 2283:2000, and the pour point is the value measured based on JIS K 2269:1987.

In the lubricating oil composition of one aspect of the present invention, based on the total amount of the lubricating oil composition, the content of the high-viscosity base oil (AH) is preferably 35% by mass or more, preferably 38% by mass or more, More preferably, it is 40 mass % or more. Moreover, 75 mass % or less is preferable, 72 mass % or less is more preferable, and 70 mass % or less is still more preferable. 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 still more preferably 40% by mass to 70% by mass. When the content of the high-viscosity base oil (AH) is in the above range, the kinematic viscosity of the lubricating oil composition can be maintained high, and a lubricating oil composition excellent in wear resistance and fatigue life can be prepared.

The high-viscosity base oil (AH) can be used alone or in combination of two or more.

(Low-Viscosity Base Oil (AL)) Low-viscosity base oil (AL) helps ensure low-temperature properties of lubricating oil compositions. Here, from the viewpoint of improving the low-temperature characteristics of the lubricating oil composition, the kinematic viscosity at 40°C of the low-viscosity base oil (AL) is preferably 5.0 mm ² /s or more, preferably 6.0 mm ² /s or more, more preferably 7.0 mm ² /s or more, more preferably 8.0 mm ² /s or more. Moreover, it is preferably 110 mm ² /s or less, more preferably 90.0 mm ² /s or less, more preferably 80.0 mm ² /s or less, and still more preferably 75 mm ² /s or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 5.0mm ² /s to 110mm ² /s, preferably 6.0mm ² /s to 90.0mm ² /s, more preferably 7.0mm ² /s to 80.0mm ² /s, and still more preferably 8.0mm ² /s~75.0mm ² /s.

Here, the low-viscosity base oil helps to ensure the low-temperature characteristics of the lubricating oil composition, and the flash point of the base oil is relatively high, and the viscosity of the base oil is low, so that the flash point of the whole base oil is lowered, and the flash point of the lubricating oil composition is reduced. reason for the decrease. Therefore, for low-viscosity base oil (AL), the one with the higher flash point should be used among the low-viscosity base oils. From this point of view, low-viscosity base oil (AL) should use low-viscosity poly-alpha-olefin (also referred to as "PAO" hereinafter), mineral oil of group II or III in the API (American Petroleum Institute) base oil category, Base oil (preferably measured according to ASTM D-2007) with a temperature gradient Δ|Dt| of the distillation temperature between two points in the distillation curve of 2.0 vol% and 5.0 vol% of the distillation temperature below 6.8°C/vol% The saturated content by the Clay-Gel method is 90 mass % or more, the sulfur content measured according to ASTM D1552 is 0.03 mass % or less, and the viscosity index obtained according to ASTM D2270 is 120 or more. Base oil) and the like. Furthermore, as the PAO, one with a low viscosity among the above-mentioned ones can be used.

In the base oil where the temperature gradient Δ|Dt| of the distillation temperature between the two points of the distillation curve of 2.0 vol% and 5.0 vol% is 6.8°C/vol% or less, the temperature gradient Δ|Dt| is preferably 6.5°C/vol% or less, preferably 6.3°C/vol% or less, more preferably 6.0°C/vol% or less, still more preferably 5.0°C/vol% or less. In addition, the above-mentioned temperature gradient Δ|Dt| is usually 0.1° C./volume % or more. The distillation temperature at 2.0 vol % of the distillate in the distillation curve is preferably 405 to 510°C, more preferably 410 to 500°C, still more preferably 415 to 490°C, and particularly preferably 430 to 480°C. The distillation temperature at 5.0% by volume of the distillate in the distillation curve is preferably 425 to 550°C, more preferably 430 to 520°C, still more preferably 434 to 500°C, and particularly preferably 450 to 490°C. The temperature gradient Δ|Dt| of the distillation temperature between two points of the distillation curve of 2.0 vol % and 5.0 vol % is 6.8°C/vol % or less. The paraffin component (%CP) in the base oil 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, particularly preferably 80 or more, and usually 99 or less. In addition, in this specification, the paraffin component (%CP) means the value measured by ASTM D-3238 ring analysis (n-d-M method).

Furthermore, the viscosity index of the low-viscosity base oil (AL) is preferably 80 or more, preferably 90 or more, more preferably 100 or more, still more preferably 110 or more, still more preferably 120 or more, and its upper limit is not There is no particular limitation, for example, it is 200.

In the lubricating oil composition of one aspect of the present invention, from the viewpoint of easily ensuring the low-temperature characteristics of the lubricating oil composition and suppressing the reduction of the flash point of the lubricating oil composition, based on the total amount of the lubricating oil composition, The content of the low-viscosity base oil (AL) is preferably 10% by mass or more, preferably 15% by mass or more, and more preferably 20% by mass or more. Moreover, 60 mass % or less is preferable, 55 mass % or less is more preferable, and 50 mass % or less is still more preferable. 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 still more preferably 20% by mass to 50% by mass.

(Other Base Oils (AZ)) Other base oils (AZ) are not particularly limited, and various base oils other than high-viscosity base oils (AH) and low-viscosity base oils (AL) can be listed. For ester oil. As the ester oil, polyol ester is preferably used. The polyhydric alcohol ester may be a partial ester of a polyhydric alcohol or a complete ester, but from the viewpoint of sludge solubility, a partial ester of a polyhydric alcohol is preferably used.

The polyhydric alcohol used as the raw material of the polyhydric alcohol ester is not particularly limited, but is preferably an aliphatic polyhydric alcohol, for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propylene glycol, Diols such as 1,4-butanediol, neopentyl glycol; triols such as glycerol, trimethylolethane, trimethylolpropane; diglycerol, triglycerol, neopentylerythritol, dipivalo Tetrahydric alcohols such as tetraols, mannitol, and sorbitol.

The hydrocarbon group (hydrocarbyl) constituting the polyol ester is preferably an alkyl group or an alkenyl group having 6 to 30 carbon atoms, preferably an alkyl group or an alkenyl group having 12 to 24 carbon atoms. base, decyl, dodecyl, tetradecyl, hexadecyl, heptadecyl, octadecyl, hexenyl, octenyl, decenyl, dodecenyl, tetradecyl Carbenyl, hexadecenyl, octadecenyl, etc. The above-mentioned alkyl group and alkenyl group may be linear or branched.

Specific examples of the complete ester of the polyhydric alcohol include neopentyl glycol dilaurate, neopentyl glycol dimyristate, neopentyl glycol dipalmitate, and neopentyl glycol distearic acid Esters, Neopentyl Glycol Diisostearate, Trimethylolpropane Trilaurate, Trimethylolpropane Trimyristate, Trimethylolpropane Tripalmitate, Trimethylolpropane Tristearate Stearates, trimethylolpropane triisostearate, glyceryl trilaurate, glyceryl tristearate, glyceryl triisostearate, etc., but not limited to these.

The partial ester of the aforementioned polyhydric alcohol is not particularly limited as long as at least one hydroxyl group remains. Specific examples of the partial ester of the polyhydric alcohol include neopentyl glycol monolaurate, neopentyl glycol monomyristate, neopentyl glycol monopalmitate, and neopentyl glycol monostearic acid ester, neopentyl glycol monoisostearate, trimethylolpropane mono (or di) laurate, trimethylol propane mono (or di) myristate, trimethylol propane mono (or di) myristate Di) palmitate, trimethylolpropane mono (or di) stearate, trimethylol propane mono (or di) isostearate, glycerol mono (or di) laurate, glycerol mono (or di) Or di) stearate, glycerol mono (or di) isostearate, and the like, preferably trimethylolpropane mono (or di) isostearate, but not limited to these.

In the lubricating oil composition of one aspect of the present invention, the content of other base oils (AZ) is preferably 6 mass % or more based on the total amount of the lubricating oil composition from the viewpoint of further improving the solubility of sludge. Moreover, 15 mass % or less is preferable, 13 mass % or less is more preferable, and 11 mass % or less is still more preferable. 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 still more preferably 6% by mass to 11% by mass. In addition, other base oils (AZ) may be used individually by 1 type, and may be used in combination of 2 or more types.

Furthermore, 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, preferably 78% by mass or more, based on the total amount of the lubricating oil composition. More preferably, it is 80 mass % or more. Moreover, 99.9 mass % or less is preferable. 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 still more preferably 80% by mass to 99.9% by mass.

Furthermore, in the lubricating oil composition of one aspect of the present invention, when the base oil (A) includes a high-viscosity base oil (AH) and a low-viscosity base oil (AL), the total amount of the base oil (A) is used as the basis In total, the total content of the high-viscosity base oil (AH) and the low-viscosity base oil (AL) is preferably 75% by mass to 100% by mass, preferably 78% by mass to 100% by mass, and more preferably 80% by mass to 100% by mass. %.

Furthermore, in the lubricating oil composition of one aspect of the present invention, when the base oil (A) includes a high-viscosity base oil (AH) and a low-viscosity base oil (AL), the high-viscosity base oil (AH) and the low-viscosity base oil The content ratio [(AH)/(AL)] of (AL) is preferably 50/50 or more in terms of mass ratio. Moreover, 80/20 or less is preferable, 75/25 or less is more preferable, and 60/30 or less is still more preferable. 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 still more preferably 60/30 to 50/50.

Furthermore, in the lubricating oil composition of one aspect of the present invention, when the base oil (A) contains other base oil (AZ), the total content of the high-viscosity base oil (AH) and the low-viscosity base oil (AL) is the same as that of the other base oil (AZ). The ratio of the content of oil (AZ) [{(AH)+(AL)}/(AZ)] in terms of mass ratio, is preferably 6/1 or more, preferably 6.5/1 or more, more preferably 7/1 or more . Moreover, 10/1 or less is preferable, 9.5/1 or less is more preferable, and 9/1 or less is still more preferable. 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.

<Polysiloxane-based defoamer (B)> The lubricating oil composition of the present invention contains a polysiloxane-based defoamer (B). However, in the present invention, by greatly reducing the content of the polysiloxane-based antifoaming agent (B) compared with the content of the previous lubricating oil composition, it is possible to achieve both long-term defoaming performance and cleanliness. That is, even if the lubricating oil composition of the present invention contains the polysiloxane-based antifoaming agent (B), the content thereof is greatly reduced compared with the conventional lubricating oil composition.

Specifically, the lubricating oil composition of the present invention is adjusted 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. The polysiloxane-based defoamer (B) is added so that the content of silicon atoms in the lubricating oil composition satisfies this numerical range. In other words, the lubricating oil composition of this invention is added so that it may become 50 mass ppb - 4,000 mass ppb in conversion of a polysiloxane type antifoaming agent (B) into a silicon atom. Then, in the lubricating oil composition of one aspect of the present invention, from the viewpoint of more easily exerting the effect of the present invention, based on the total amount of the lubricating oil composition, the polysiloxane-based antifoaming agent converted into silicon atoms The content of (B) is added in such a manner that it is preferably 100 mass ppb or more, preferably 200 mass ppb or more, more preferably 250 mass ppb or more, still more preferably 300 mass ppb or more, still more preferably 350 mass ppb or more The mass ppb or more, more preferably 400 mass ppb or more, still more preferably 450 mass ppb or more, and still more preferably 500 mass ppb or more. Furthermore, it is added in the following manner: preferably 3,500 mass ppb or less, preferably 3,000 mass ppb or less, more preferably 2,500 mass ppb or less, still more preferably 2,200 mass ppb or less, still more preferably 2,000 mass ppb or less, and still more It is preferably 1,800 mass ppb or less, more preferably 1,600 mass ppb or less, and still more preferably 1,500 mass ppb or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 100 mass ppb to 3,500 mass ppb, preferably 200 mass ppb to 3,000 mass ppb, more preferably 250 mass ppb to 2,500 mass ppb, still more preferably 300 mass ppb to 2,200 mass ppb, and more It is preferably 350 mass ppb to 2,000 mass ppb, more preferably 400 mass ppb to 1,800 mass ppb, still more preferably 450 mass ppb to 1,600 mass ppb, and still more 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 polysiloxane-based antifoaming agent (B) is not particularly limited as long as it is a polymer that contains silicon atoms and exhibits antifoaming performance. Examples of such polymers include polydimethylsiloxane, fluorinated polysiloxane, and the like. These may be used individually by 1 type, and may be used in combination of 2 or more types.

Furthermore, the polysiloxane-based antifoaming agent (B) should be prepared in the form of a solution (dispersion) by adding diluent oil, etc., in the form of a solution (dispersion) and the base oil (A) in consideration of workability or solubility and dispersibility of the base oil (A). ), and stir to dissolve and disperse evenly.

<Additives for lubricating oils> The lubricating oil composition of one aspect of the present invention may contain other additives (hereinafter also referred to as "lubricating oil additives") other than the polysiloxane-based antifoaming agent (B) within the scope of not impairing the effects of the present invention. As additives for lubricating oils, for example, antioxidants, extreme pressure agents, deemulsifiers, rust inhibitors, viscosity index enhancers, pour point depressants, metal deactivators, ashless cleaning dispersants, friction modifiers, etc. . These additives for lubricating oil may be used individually by 1 type, and may be used in combination of 2 or more types.

In addition, in this specification, additives, such as a viscosity index improver, may be mixed with other components in the form of the solution melt|dissolved in a diluent oil in consideration of handleability and solubility to a base oil. At this time, in this specification, content of additives, such as a viscosity index improver, is the content of the active ingredient (converted to resin component) which does not contain diluent oil. Hereinafter, the details of each of the above-mentioned additives for lubricating oil will be described.

(Antioxidants) As antioxidants, amine-based antioxidants, phenol-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, and molybdenum-amine complex-based antioxidants that have been used in lubricating oil compositions can be used. These antioxidants may be used individually by 1 type, and may be used in combination of 2 or more types.

Examples of amine-based antioxidants include monoalkyldiphenylamine-based compounds such as monooctyldiphenylamine and monononyldiphenylamine; 4,4'-dibutyldiphenylamine, 4,4'-dipentyldiphenylamine, and the like. Aniline, 4,4'-dihexyldiphenylamine, 4,4'-diheptyldiphenylamine, 4,4'-dioctyldiphenylamine, 4,4'-dinonyldiphenylamine, monobutylphenyl Dialkyldiphenylamine compounds such as monooctylaniline; polyalkyldiphenylamine compounds such as tetrabutyldiphenylamine, tetrahexyldiphenylamine, tetraoctyldiphenylamine, tetranonyldiphenylamine; α-naphthylamine, benzene Base-α-naphthylamine, butylphenyl-α-naphthylamine, pentylphenyl-α-naphthylamine, hexylphenyl-α-naphthylamine, heptylphenyl-α-naphthylamine, octylphenyl -Naphthylamine-based compounds such as α-naphthylamine, nonylphenyl-α-naphthylamine, and the like.

The phenolic antioxidants include, for example, 2,6-di-tert-butyl-4-cresol, 2,6-di-tert-butyl-4-ethylphenol, octadecyl-3-( Monophenolic compounds such as 3,5-di-tert-butyl-4-hydroxyphenyl) propionate; 4,4'-methylenebis(2,6-di-tert-butylphenol), 2 , 2'-methylenebis(4-ethyl-6-tert-butylphenol) and other diphenol-based compounds.

As a phosphorus antioxidant, triphenyl phosphite etc. are mentioned. As sulfur-based antioxidants, for example, 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamino) ) thioterpene (thioterpene) based compounds such as phenol, phosphorus pentasulfide and pinene reactants. As a molybdenum amine complex 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 should only be added in the minimum amount necessary to maintain the oxidation stability, and based on the total amount of the lubricating oil composition, it is preferably 0.01% by mass to 1.5% by mass, preferably 0.1% by mass to 1% by mass .

(extreme pressure agent) As the extreme-pressure agent, organometallic extreme-pressure agents, sulfur-based extreme-pressure agents, phosphorus-based extreme-pressure agents, and sulfur-phosphorus-based extreme-pressure agents that have been conventionally used in lubricating oil compositions can be used. In this case, the extreme pressure agent may be used alone or in combination of two or more.

The organometallic extreme pressure agent includes, for example, organomolybdenum-based compounds such as molybdenum dialkyldithiocarbamate (MoDTC) and molybdenum dialkyldithiophosphate (MoDTP), and dialkyldithiomolybdenum-based compounds. Organozinc compounds such as zinc carbamate (ZnDTC) and zinc dialkyldithiophosphate (ZnDTP).

Examples of sulfur-based extreme pressure agents include sulfurized oils and fats, sulfurized fatty acids, sulfurized esters, sulfurized olefins, monosulfides, polysulfides, dihydrocarbyl sulfides, thiadiazole compounds, and alkylthioamines Carboxylic compounds, thiocarbamate compounds, thioterpene compounds and dialkylthiodipropionate compounds.

The phosphorus-based extreme pressure agent includes, for example, phosphoric acid esters such as aryl phosphate, alkyl phosphate, alkenyl phosphate, and alkylaryl phosphate; acid monoaryl phosphate, acid diaryl phosphate, Acidic phosphates such as acid monoalkyl phosphate, acid dialkyl phosphate, acid monoalkenyl phosphate, acid dienyl phosphate, etc.; aryl hydrogen phosphite, alkyl hydrogen phosphite, aryl phosphite phosphites such as esters, alkyl phosphites, alkenyl phosphites, aryl alkyl phosphites; acid monoalkyl phosphites, acid dialkyl phosphites, acid monoalkenyl phosphites, Acid phosphites such as acid dienyl phosphites; and amine salts of these.

The sulfur-phosphorus extreme pressure agent includes, for example, monoalkyl thiophosphate, dialkyl dithiophosphate, trialkyl trithiophosphate, and amine salts thereof, and dithiophosphoric acid. Dialkyl zinc (Zn-DTP).

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

(De-emulsifier) Examples of the deemulsifier include cationic surfactants such as quaternary ammonium salts and imidazolines; polyoxyalkylene block polymers (ethylene oxide (EO)-propylene oxide (PO) block polymers, etc.), polyoxyalkylene glycols and polyoxyalkylene polyglycols; alkylphenol-formaldehyde polycondensates of alkylene oxide adducts, etc. The content of the emulsifier is preferably 0.001 to 0.5% by mass, preferably 0.002 to 0.2% by mass, based on the total amount of the lubricating oil composition.

(Rust inhibitor) Examples of the rust inhibitor include metal sulfonates, alkylbenzenesulfonates, dinonylnaphthalenesulfonates, organic phosphites, organic phosphates, metal organic sulfonic acids, metal organic phosphates, alkenes succinates, polyol esters, benzotriazole-based compounds, and the like. The content of the rust inhibitor is preferably 0.01% by mass to 10.0% by mass, preferably 0.05% by mass to 5.0% by mass, based on the total amount of the lubricating oil composition.

(viscosity index enhancer) Examples of viscosity index improvers include polymethacrylates (PMA), dispersion-type polymethacrylates, olefin-based copolymers (olefin copolymers (OCP); for example, ethylene-propylene copolymers, etc.), dispersion-type Olefin-based copolymers, styrene-based copolymers (eg, styrene-diene hydrogenated copolymers, etc.), and the like. From the viewpoint of the addition effect, based on the total amount of the lubricating oil composition, the addition amount of these viscosity index enhancers is preferably 1% by mass to 10% by mass, preferably 2% by mass to 8% by mass. In addition, in the lubricating oil composition of one aspect of the present invention, the viscosity index enhancers preferably contain at least an olefin copolymer, and the content of the olefin copolymer is preferably based on the total amount of the lubricating oil composition. 1% by mass to 10% by mass, preferably 2% by mass to 8% by mass.

(Pour Point Depressant) Examples of pour point depressants include ethylene-vinyl acetate copolymers, condensates of chlorinated paraffins and naphthalene, condensates of chlorinated paraffins and phenol, polymers such as polymethacrylates and polyalkylstyrenes. . The weight average molecular weight (Mw) of these polymers is preferably 50,000 to 150,000. From the viewpoint of the addition effect, the content of the pour point depressant is preferably 0.01% by mass to 5.0% by mass, preferably 0.02% by mass to 2.0% by mass, based on the total amount of the lubricating oil composition.

(metal deactivator) As a metal deactivator, a benzotriazole type compound, a methyl benzotriazole type compound, a thiadiazole type compound, an imidazole type compound, a pyrimidine type compound etc. are mentioned, for example. From the viewpoint of the addition effect, the content of the metal deactivator is preferably 0.01% by mass to 5.0% by mass, preferably 0.02% by mass to 3.0% by mass, based on the total amount of the lubricating oil composition.

(ashless cleaning dispersant) As for the ashless cleaning and dispersing agents, for example, succinimides, boron-containing succinimides, benzylamines, boron-containing benzylamines, succinic acid esters, fatty acids or succinic acid are exemplified. Monovalent or divalent carboxamides, etc. From the viewpoint of the addition effect, the content of the ashless cleaning dispersant is preferably 0.01% by mass to 5.0% by mass, preferably 0.02% by mass to 3.0% by mass, based on the total amount of the lubricating oil composition.

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

[Properties of lubricating oil composition] <Silicon atom content> The lubricating oil composition of the present invention needs 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 content of silicon atoms is less than 50 mass ppb, long-term defoaming performance cannot be ensured. In addition, when the content of silicon atoms exceeds 4,000 mass ppb, cleanliness cannot be ensured. Here, in the lubricating oil composition of one aspect of the present invention, from the viewpoint of more easily exerting the effects of the present invention, based on the total amount of the lubricating oil composition, the content of silicon atoms is preferably 100 mass ppb or more, Preferably it is 200 mass ppb or more, 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 mass ppb or more, still more preferably 450 mass ppb More preferably, it is 500 mass ppb or more. Also, it is preferably 3,500 mass ppb or less, more preferably 3,000 mass ppb or less, more preferably 2,500 mass ppb or less, still more preferably 2,200 mass ppb or less, still more preferably 2,000 mass ppb or less, still more preferably 1,800 mass ppb or less, more preferably 1,600 mass ppb or less, particularly preferably 1,500 mass ppb or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 100 mass ppb to 3,500 mass ppb, preferably 200 mass ppb to 3,000 mass ppb, more preferably 250 mass ppb to 2,500 mass ppb, still more preferably 300 mass ppb to 2,200 mass ppb, and more It is preferably 350 mass ppb to 2,000 mass ppb, more preferably 400 mass ppb to 1,800 mass ppb, still more preferably 450 mass ppb to 1,600 mass ppb, and still more preferably 500 mass ppb to 1,500 mass ppb. Furthermore, the content of silicon atoms in the lubricating oil composition can be measured using an inductively coupled plasma luminescence analyzer (ICP). In addition, when there are no silicon atoms other than those derived from the polysiloxane-based antifoaming agent (B) in the lubricating oil composition, the content of silicon atoms in the lubricating oil composition can theoretically be defoamed by the polysiloxane-based antifoaming agent. The content of the agent (B) (converted into solid content) and the content of silicon atoms contained in the polysiloxane-based antifoaming agent (B) were calculated.

<Kinematic viscosity and viscosity index> The kinematic viscosity at 40°C of the lubricating oil composition of one aspect of the present invention is preferably 10mm ² /s~500mm ² /s, preferably 30mm ² /s~450mm ² /s, more Preferably, it is 50mm ² /s~400mm ² /s. The viscosity index of the lubricating oil composition of one aspect of the present invention is preferably 100 or more, preferably 110 or more, and more preferably 120 or more. Furthermore, in this specification, the kinematic viscosity and viscosity index at 40°C refer to the values measured and calculated according to JIS K2283:2000.

[Manufacturing method of lubricating oil composition] The manufacturing method of the lubricating oil composition of this invention is not specifically limited. For example, the method for producing a lubricating oil composition according to one aspect of the present invention includes the step of mixing the base oil (A) and the polysiloxane-based antifoaming agent (B), and is adjusted so that the total amount of the lubricating oil composition is The silicon atom content is 50 mass ppb to 4,000 mass ppb on a benchmark basis. There is no restriction|limiting in particular about the method of mixing the said each component, The method which has the process of mix|blending a polysiloxane-type antifoamer (B) with a base oil (A) is mentioned. Other additives (additives for lubricating oil) other than the polysiloxane-based antifoaming agent (B) can be prepared at the same time as the polysiloxane-based antifoaming agent (B) or separately. In addition, the polysiloxane-based antifoaming agent (B) and other additives (additives for lubricating oil) can be prepared in the form of a solution (dispersion) by adding diluent oil or the like. After mixing each component, it is preferable to stir it by a well-known method, and to disperse|distribute it uniformly.

[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 requiring long-term defoaming performance and cleanliness. For example, it can be suitably used as speed-increasing oil for windmills, hydraulic operating oil, compressor oil, gear oil, cutting oil, tool oil, refrigeration oil, turbine oil, internal combustion engine oil, transmission oil, or axle unit oil for automobiles. Accordingly, in one aspect of the present invention, the following method is provided. ･A method of use in which the lubricating oil composition of the present invention is used as speed-increasing oil for windmills, hydraulic operating oil, compressor oil, gear oil, cutting oil, tool oil, refrigeration oil, turbine oil, internal combustion engine oil, gear oil tank oil or axle unit oil for automobiles.

[An aspect provided by the present invention] In one aspect of the present invention, the following [1] to [8] are provided. [1] A lubricating oil composition comprising a base oil (A) and a polysiloxane-based antifoaming agent (B), and based on the total amount of the lubricating oil composition, the content of silicon atoms is 50 mass ppb ~4,000 quality ppb. [2] The lubricating oil composition according to [1], wherein the base oil (A) is at least one selected from the group consisting of synthetic oil (A1) and mineral oil (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 oil (A1) and mineral oil (A2). [4] The lubricating oil composition according to [1], wherein the base oil (A) is selected from the group consisting of synthetic oil (A1) and mineral oil (A2), and has a mutual kinematic viscosity at 40° C. 2 or more different. [5] The lubricating oil composition according to any one of [1] to [4], wherein the base oil (A) and the polysiloxane-based defoaming are based on the total amount of the lubricating oil composition. The total content of the agent (B) is 75% by mass or more and 94.9% by mass or less. [6] The lubricating oil composition according to any one of [1] to [5], wherein the polysiloxane-based antifoaming agent (B) contains a compound selected from the group consisting of polydimethylsiloxane and fluorinated polysiloxane. One or more of the group consisting of siloxanes. [7] The lubricating oil composition according to any one of [1] to [6], further comprising a composition selected from the group consisting of an antioxidant, an extreme pressure agent, a deemulsifier, a rust inhibitor, a viscosity index enhancer, a flow One or more lubricating oil additives in the group consisting of point drop agent, metal deactivator, ashless cleaning dispersant and friction modifier. [8] The lubricating oil composition according to any one of [1] to [7], which is used as speed-increasing oil for windmills, hydraulic operating oil, compressor oil, gear oil, cutting oil, tool oil, Refrigerant oil, turbine oil, internal combustion engine oil, transmission oil or axle unit oil for automobiles.

[Example] The present invention will be specifically described by the following examples, but the present invention is not limited to the following examples.

[Measurement methods of various physical property values] (1) The kinematic viscosity and viscosity index of the base oil and lubricating oil composition were measured and calculated according to JIS K2283:2000. (2) Paraffin component (%C _p ) It was calculated|required by ASTM D-3238 ring analysis (ndM method).

[Examples 1 to 4, Comparative Examples 1 to 4] The base oil (A) and polysiloxane-based antifoaming agent (B) shown below were sufficiently mixed according to the preparation amount (mass %) shown in Table 1 to prepare Examples 1 to 3 and Comparative Examples 1 to 2. Lubricating oil composition. In addition, the base oil (A) shown below, the polysiloxane-based antifoaming agent (B), and the additives for lubricating oil were sufficiently mixed in the amounts (mass %) shown in Table 2 to prepare Example 4 and comparison The lubricating oil compositions of Examples 3-4.

<Base oil (A)> (High viscosity base oil (AH)) ･High viscosity base oil (AH)-1: Polyα-olefin (PAO), 40°C kinematic viscosity=1,240mm ² /s, viscosity index=170 ･High viscosity base oil (AH)-2: Decene oligomer of 1-decene polymerized by metallocene catalyst (mPAO), kinematic viscosity at 40℃=1,616mm ² /s, viscosity index=202 (low viscosity base oil) Oil (AL)) ･Low viscosity base oil (AL)-1: C40-based polyalpha-olefin (PAO), 40℃ kinematic viscosity=28.8mm ² /s, viscosity index=136 ･Low viscosity base oil (AL) -2: Mineral oil classified as group II according to API classification, kinematic viscosity at 40°C = 30.6mm ² /s, viscosity index = 104 ･Low viscosity base oil (AL) -3: Measured according to ASTM D-2007 A base oil with a saturated content of 90 mass % or more by the Clay-Gel method, a sulfur content measured according to ASTM D1552 of 0.03 mass % or less, and a viscosity index obtained according to ASTM D2270 of 120 or more, 40 ℃ kinematic viscosity = 43.75 mm ² /s, viscosity index = 143, paraffin component (% C _P ) = 94.1 Furthermore, low viscosity base oil (AL)-3 is a base oil prepared by the following method. <Production method> The feedstock oil, which is a distillate oil of 200N (Neutral) or more, is subjected to hydroisomerization and dewaxing treatment, and further subjected to hydrotreating treatment, and then the 5 vol% fraction of the distillation curve is 460°C or higher. Distilled at the same distillation temperature, and recovered fractions with a kinematic viscosity in the range of 19.8-50.6 mm ² /s at 40° C. to prepare low-viscosity base oil (AL)-3. In addition, the conditions of the hydroisomerization dewaxing treatment are as follows. ･Hydrogen supply ratio: 300~400Nm ³ for 1 liter of feedstock oil ･Hydrogen partial pressure: 10~15MPa ･Liquid hourly space velocity (LHSV): 0.5~1.0hr ^-1 ･Reaction temperature: 300~350℃ Obtained The various properties of the low viscosity base oil (AL)-3 are shown below. ･Distillation temperature at 2.0 vol% distillate: 451.0°C ･Distillation temperature at 5.0 vol% distillate: 464.0°C ･Temperature gradient Δ|Dt|=4.3°C/vol% Furthermore, distillate 2.0 vol% and the distillation temperature at 5.0 vol% is determined by distillation gas chromatography according to ASTM D6352. (Other base oils (AZ)) ･Ester oil: ester of trimethylolpropane and isostearic acid (mol ratio 1:2), kinematic viscosity at 40°C=106.7mm ² /s, viscosity index=124

<Polysiloxane-based defoamer (B)> A polysiloxane-based defoamer with 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 polysiloxane-based defoamer. In addition, the polysiloxane-based antifoaming agent (B) is prepared into the base oil (A) after being diluted with light oil to obtain a diluted product. In Table 1 and Table 2, the content of the polysiloxane-based defoamer (B) in the diluted product of the polysiloxane-based defoamer (B) (based on the total amount of the lubricating oil composition) and its use are shown. The content of light oil in diluting polysiloxane-based defoamer (B) (based on the total amount of lubricating oil composition).

<Additive for lubricating oil> ･Phenolic antioxidant: octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate. ･Amine-based antioxidant: Monobutylphenylmonoctylaniline. ･Dihydrocarbyl sulfide: a mixture of di-tertiary butyl disulfide and di-tertiary butyl trisulfide, S component = 38.5%. ･Alkyl phosphorothioate: see [2,4-isoalkyl(C ₉ , C ₁₀ )phenyl] phosphorothioate. ･Alkyl thiocarbamate: methylene bis(dibutyl dithiocarbamate), S component = 30.3%. ･Alkylbenzotriazole: N-dialkylaminomethylbenzotriazole (N=14.6%). ･Acid Phosphate: Acidic isodecyl phosphate. ･Alkylamine: Trioctylamine. ･EO-PO copolymer: EO-PO block copolymer in xylene solution (10%) ･Alkenylsuccinimide: 50% polybutenylsuccinimide, 20% polybutene and 30 mineral oil % of the mixture (base number; 37 mgKOH/g). ･OCP: Ethylene propylene oligomer.

[Evaluation] The following tests were performed on the prepared lubricating oil compositions, respectively.

＜Evaluation of foaming＞ By the method according to JIS K 2518:2003, air blowing was started at 60°C, and the volume of the foam after 1 day (after 1440 minutes) and after 2 days (after 2880 minutes) was measured. In the foaming test, the amount of foaming after 1440 minutes and after 2880 minutes was both 50 mL or less as pass (A), and the amount of foaming after 1440 minutes and after 2880 minutes was regarded as not. Pass (F).

＜Evaluation of cleanliness＞ The cleanliness of the lubricating oil composition is evaluated using the pollution degree code according to ISO4406:1999. Specifically, the sampled lubricating oil composition is measured with a particle counter, and the pollution degree code is obtained. The pollution degree code is to classify the number of particles of the lubricating oil composition sampled into the particle size range of 4 μm or more, 6 μm or more, and 14 μm or more, and the numerical range number (0~28) classified according to the number of particles in 1mL is slashed. (/), and obtain "rank number of particles larger than 4 μm (in 1 mL)" / "rank number of particles larger than 6 μm (in 1 mL)" / "rank number of particles larger than 14 μm (in 1 mL)" . The larger the pollution degree code, the higher the number of particles and the lower the cleanliness. In this example, the "rank number of the number of particles of 6 μm or more (in 1 mL)" is 15 or less (the number of particles: 320 particles/1 mL or less), and the "rank number of the number of particles of 14 μm or more (in 1 mL)" is A lubricating oil composition of 12 or less (number of particles: 40 particles/1 mL or less) was set as pass (A). In addition, the "rank number of the number of particles of 6 μm or more (in 1 mL)" is 16 or more (number of particles: more than 320 particles/1 mL), or the "rank number of the number of particles of 14 μm or more (in 1 mL)" is 13 or more ( The number of particles: more than 40 particles/1 mL) of the lubricating oil composition was regarded as unacceptable (F).

The evaluation results are shown in Tables 1 and 2. In addition, "silicon atom content in lubricating oil composition" in Table 1 and Table 2 is the value calculated|required based on the silicon atom content in polysiloxane type defoaming agent (B).

[Table 1]

[Table 2]

From Table 1, the following contents are known. It can be seen that Examples 1 to 3 in which the content of silicon atoms in the lubricating oil composition is in the range of 50 mass ppb to 4,000 mass ppb have both long-term defoaming performance and cleanliness. On the other hand, it turns out that the comparative example 1 in which the silicon atom content in the lubricating oil composition is less than 50 mass ppb cannot ensure the long-term defoaming performance. Moreover, it turns out that the comparative example 2 in which the silicon atom content in a lubricating oil composition exceeds 4,000 mass ppb super cannot ensure cleanliness.

In addition, the same results as described above were also seen from the evaluation results in Table 2, which were examined when additives for lubricating oil other than the polysiloxane-based antifoaming agent (B) were also blended in the lubricating oil composition. That is, it can be seen that Example 4 in which the content of silicon atoms in the lubricating oil composition is in the range of 50 mass ppb to 4,000 mass ppb has both long-term defoaming performance and cleanliness. On the other hand, it was found that Comparative Example 3 in which the content of silicon atoms in the lubricating oil composition was less than 50 mass ppb could not ensure long-term defoaming performance. Moreover, it turns out that the comparative example 4 in which the silicon atom content in a lubricating oil composition exceeds 4,000 mass ppb cannot ensure cleanliness.

(none)

Claims (8)

A lubricating oil composition containing a base oil (A) and a polysiloxane-based defoamer (B), and based on the total amount of the aforementioned lubricating oil composition, the silicon atom content is 50 mass ppb to 4,000 mass ppb. The lubricating oil composition according to claim 1, wherein the base oil (A) is at least one 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 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 2 selected from the group consisting of synthetic oil (A1) and mineral oil (A2) and having mutually different kinematic viscosities at 40°C more than one species. The lubricating oil composition according to any one of claims 1 to 4, wherein the sum of the base oil (A) and the polysiloxane-based antifoaming agent (B) is based on the total amount of the lubricating oil composition. Content is 75 mass % or more and 94.9 mass % or less. The lubricating oil composition according to any one of claims 1 to 5, wherein the polysiloxane-based defoamer (B) comprises a group selected from the group consisting of polydimethylsiloxane and fluorinated polysiloxane 1 or more of the group. The lubricating oil composition according to any one of claims 1 to 6, further comprising a composition selected from the group consisting of antioxidants, extreme pressure agents, deemulsifiers, rust inhibitors, viscosity index enhancers, pour point depressants, metal depressants One or more lubricating oil additives in the group consisting of active agent, ashless cleaning dispersant and friction modifier. The lubricating oil composition according to any one of claims 1 to 7, which is used as speed-increasing oil for windmills, hydraulic operating oil, compressor oil, gear oil, cutting oil, tool oil, refrigerator oil, turbine oil, Internal combustion engine oil, transmission oil or axle unit oil for automobiles.