JP2018062551A - Lubricant composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lubricant composition that is not limited in environments of usage such as temperature and pressure, and that can stably exhibit excellent friction reducing effect even when used between sliding members with a reduced surface roughness and at a clearance of several nanometers.SOLUTION: A lubricant composition contains a mineral oil (A) and an ashless-type friction modifier (B), and satisfies the following condition (I). The condition (I): x that satisfies the formula (i) (μ(0)×5≤μ(x)) is 5.0 [mN/m] or more when a sample oil (α) containing 1 mass% of ashless-type friction modifier (B) and 5 mass% of polybutenyl succinimide together with a mineral oil (A) is prepared and a viscosity coefficient value at a predetermined surface force is measured for the sample oil (α) in a resonance shear measuring apparatus (in the formula (i), μ(0) represents the viscosity coefficient value [Ns/m] at a surface force of 0 [mN/m], and μ(x) represents the viscosity coefficient value at a surface force of x [mN/m]).SELECTED DRAWING: None

Description

  The present invention relates to a lubricating oil composition.

As a countermeasure against global warming, reduction of friction loss of machine elements is required for the purpose of improving energy efficiency.
For example, in the case of automobiles, it is said that 16.5% of the energy generated in the engine is lost due to friction inside the engine and transmission, and it is also expected to improve automobile fuel efficiency by reducing friction loss. .
In recent years, countries that impose carbon dioxide emission regulations have emerged, and regulations for improving energy efficiency are steadily expanding both in quality and scope, and it is necessary to reduce friction loss of machine elements.

By the way, in order to reduce friction of machine elements, a friction modifier is often added to the lubricating oil composition. Generally, friction modifiers are roughly classified into metal friction modifiers such as molybdenum dialkyldithiocarbamate (MoDTC) and ashless friction modifiers that do not contain metal atoms.
For example, Patent Document 1 discloses a lubricating oil composition containing an organomolybdenum compound having a specific structure.
Patent Document 2 discloses a lubricating oil having at least one of an aliphatic amine having a hydrocarbon group having 12 to 20 carbon atoms and an ethylene oxide adduct thereof, which is an ashless friction modifier.

JP, 2015-010177, A International Publication No. 2011-0662282

However, the metal friction modifier such as an organic molybdenum compound used in the lubricating oil composition described in Patent Document 1 needs to have a certain temperature or pressure to form a reaction film on the friction surface. There is also a concern that corrosion may occur depending on the friction surface material.
On the other hand, ashless friction modifiers such as aliphatic amines used in the lubricating oil described in Patent Document 2 are relatively loose in restrictions that are concerned with the above metal friction modifiers. Compared to the system friction modifier, the friction reducing effect is low.

  In recent years, the sliding surfaces of engine members such as pistons and cylinder liners have been smoothed and coated to reduce surface roughness and prevent boundary lubrication and metal contact, thereby reducing friction between the two sliding members. It is illustrated. By reducing the surface roughness of the sliding surface, the clearance for the lubricating oil composition to enter between the two sliding members can be adjusted to several nm. Therefore, there is a demand for a lubricating oil composition that can exhibit a friction reducing effect even if the clearance between the two sliding members is about several nm.

Between the sliding members having a clearance of several nanometers, it is difficult for the lubricating oil composition to enter, and movement of components in the lubricating oil composition is limited.
According to the study by the present inventors, it has been found that there is a lubricating oil composition in which the viscosity increases and the friction increases when a weak load is applied when the clearance is several nm.

  The present invention has been made in view of the above circumstances, and there is no restriction on the use environment such as temperature and pressure, the surface roughness is reduced, and even when used between sliding members having a clearance of several nm, it is stable. An object of the present invention is to provide a lubricating oil composition that can exhibit an excellent friction reducing effect.

  The present inventors paid attention to the combination of mineral oil and ashless friction modifier contained in the lubricating oil composition. Then, a combination of mineral oils such that the surface force that gives a five times higher viscosity coefficient than the viscosity coefficient when the surface force is 0 [mN / m] measured using a resonance shear measuring device is equal to or greater than a predetermined value. The present inventors have found that a lubricating oil composition containing ashless friction modifier and the ashless friction modifier can solve the above problems.

That is, the present invention provides the following [1].
[1] A lubricating oil composition containing a mineral oil (A) and an ashless friction modifier (B) and satisfying the following condition (I).
Condition (I): A sample oil (α) containing 1% by mass of the ashless friction modifier (B) and 5% by mass of polybutenyl succinimide is prepared together with the mineral oil (A). In contrast, when the value of the viscosity coefficient at a predetermined surface force is measured by using a resonance shear measuring device, the following formula (i)
Formula (i): μ (0) × 5 = μ (x)
[In the above formula (i), μ (0) represents the value of the viscosity coefficient [Ns / m] at a surface force of 0 [mN / m]. μ (x) is the value of the viscosity coefficient at the surface force x [mN / m]. ]
X satisfying the condition is 5.0 [mN / m] or more.

  The lubricating oil composition of the present invention has no restriction on the usage environment such as temperature and pressure, the surface roughness is reduced, and the friction is stable and excellent even when used between sliding members having a clearance of several nanometers. A reduction effect can be exhibited.

It is a graph which shows the relationship between the distance between surfaces and surface force which each measured using the resonance shear measuring apparatus with respect to the sample oil ((alpha) 1), ((alpha) 4), and ((alpha) 6) prepared in the Example. It is a graph which shows the relationship between the surface force and the viscosity coefficient which measured using the resonance shear measuring apparatus with respect to the sample oil ((alpha) 1), ((alpha) 4), and ((alpha) 6) prepared in the Example, respectively. It is a schematic diagram which shows the outline of the floating liner testing machine which measures the friction energy between a piston ring and a liner.

[Lubricating oil composition]
The lubricating oil composition of the present invention contains a mineral oil (A) and an ashless friction modifier (B) and satisfies the following condition (I).
Condition (I): A sample oil (α) containing 1% by mass of the ashless friction modifier (B) and 5% by mass of polybutenyl succinimide is prepared together with the mineral oil (A). In contrast, when the value of the viscosity coefficient at a predetermined surface force is measured by using a resonance shear measuring device, the following formula (i)
Formula (i): μ (0) × 5 = μ (x)
[In the above formula (i), μ (0) represents the value of the viscosity coefficient [Ns / m] at a surface force of 0 [mN / m]. μ (x) is the value of the viscosity coefficient at the surface force x [mN / m]. ]
X satisfying the condition is 5.0 [mN / m] or more.

The above condition (I) is that when the viscosity of the sample oil (α) is increased when the sample oil (α) is supplied between the sliding members having a reduced surface roughness and a clearance of several nm. It defines the surface force.
The lubricating oil composition containing a combination of mineral oil (A) and ashless friction modifier (B), which is a constituent of sample oil (α) that satisfies the above condition (I), has a surface force of 5.0. Even when a low surface force (weak load) of less than [mN / m] is applied, it is considered that the phenomenon that viscosity increases is suppressed, and as a result, an excellent friction reducing effect can be maintained stably.

In the sample oil (α), the content of the ashless friction modifier (B) is a fixed amount of 1% by mass based on the total amount (100% by mass) of the sample oil (α). Depending on the type of the agent (B), there may be a difference in the dispersion state.
Therefore, in order to make the dispersion state in the mineral oil (A) of the fixed amount (1 part by mass) of the ashless friction modifier (B), “polybutenyl succinimide” is added to the sample oil (α). 5% by mass is added based on the total amount (100% by mass) of the sample oil (α).
That is, in the present invention, in order to more accurately evaluate the combination of components (A) and (B) when a certain amount of ashless friction modifier (B) is added to mineral oil (A), A predetermined amount of “polybutenyl succinimide” is blended in the oil (α) to keep the dispersion state of the component (B) constant.
In addition, the presence of this “polybutenyl succinimide” has an influence on the surface force and viscosity coefficient due to the difference in the combination of mineral oil (A) and ashless friction modifier (B). It is small compared.

When the distance between surfaces decreases to the nanometer level, liquids sandwiched between solid surfaces may exhibit properties that are significantly different from bulk, such as formation of ordered structures and dramatic increases in viscosity, due to confinement and interface effects. Are known.
The “resonance shear measuring device” described in condition (I) has a function as a surface force measuring device that measures the surface force (repulsive force / attractive force) generated in the direction perpendicular to two opposing surfaces simultaneously with the distance between the surfaces. In addition, the device has a function of evaluating the characteristics (structured behavior, viscosity, friction, lubrication, shear resistance) of the liquid sandwiched between the surfaces by the resonance shear response.

First, let us consider a change in surface force when using a resonance shear measuring device, sandwiching sample oil (α) between two opposing surfaces, and gradually reducing the distance between the surfaces when the surfaces are brought close to each other.
As shown in FIG. 1, the surface force does not fluctuate greatly in the range where the distance between the surfaces is large to some extent. However, when the distance between the surfaces is about 5 to 10 nm, the surface force tends to increase.
According to the study by the present inventors, it is considered that the distance between the surfaces at which the surface force increases is less affected by the types of mineral oil (A) and ashless friction modifier (B).

Next, as defined in condition (I), the viscosity for each surface force when the surface oil is changed by sandwiching the sample oil (α) between the two opposing surfaces using the resonance shear measuring device. When the change in the value of the coefficient was measured, it was found that there was a difference depending on the combination of the mineral oil (A) constituting the sample oil (α) and the ashless friction modifier (B).
For example, as shown in FIG. 2, in the sample oil (α6) composed of mineral oil and polybutenyl succinimide as a dispersant, the surface force is gradually increased from 0 [mN / m]. The viscosity coefficient increases remarkably at a minute surface force value, and the viscosity coefficient becomes substantially constant when the surface force exceeds a predetermined value. This indicates that when a surface force of a certain value or more is applied to the sample oil, the viscosity of the sample oil increases rapidly.
That is, in this sample oil, the surface force is a slight surface force before reaching 5.0 [mN / m], and is 5 times the value of the viscosity coefficient μ (0) when the surface force is 0. Therefore, the above condition (I) is not satisfied.
In addition, it was confirmed that the same tendency is seen also about what mix | blended the ashless type friction modifier with said sample oil which is used by patent document 2, for example.
In such sample oil, even if a small load is applied, the components constituting the mineral oil easily form a solid adhesive structure, so that the viscosity may increase rapidly.

However, according to the study by the present inventors, the sample oil (α1) prepared by combining a specific mineral oil (A) and the ashless friction modifier (B) is used as shown in FIG. As shown in the graph of), it was confirmed that even if the surface force was gradually increased, the viscosity coefficient did not increase sharply, but only a moderate increase.
That is, in the sample oil (α1) shown in FIG. 2, the surface force x reaching 5 times the value of the viscosity coefficient μ (0) when the surface force is 0 [mN / m] is at least 5. 0 [mN / m] or more, which satisfies the above condition (I).
In such sample oil (α), when a small load is applied, it is considered that the formation of a solid adhesive structure due to components in mineral oil is suppressed by the presence of a predetermined ashless friction modifier. It is done.

Whether the sample oil (α) satisfies the condition (I) is determined by the combination of the mineral oil (A) and the ashless friction modifier (B).
Hereinafter, the details of the mineral oil (A) and the ashless friction modifier (B) will be described from that viewpoint.

The lubricating oil composition of one embodiment of the present invention further contains one or more ashless dispersants (C) selected from alkenyl succinimide (C1) and boron-modified alkenyl succinimide (C2). It is preferable.
Moreover, the lubricating oil composition of one aspect of the present invention may contain a synthetic oil together with the mineral oil (A) as long as the effects of the present invention are not impaired, and other than the components (B) and (C) You may contain the additive for lubricating oil.

  In the lubricating oil composition of one embodiment of the present invention, the total content of the component (A) and the component (B) is preferably 60% by mass or more based on the total amount (100% by mass) of the lubricating oil composition. Preferably it is 65 mass% or more, More preferably, it is 70 mass% or more, More preferably, it is 75 mass% or more.

  In the lubricating oil composition of one embodiment of the present invention, the total content of the component (A), the component (B), and the component (C) is preferably based on the total amount (100% by mass) of the lubricating oil composition. 65 mass% or more, More preferably, it is 70 mass% or more, More preferably, it is 75 mass% or more, More preferably, it is 80 mass% or more.

<Mineral oil (A)>
Examples of the mineral oil (A) contained in the lubricating oil composition of the present invention include atmospheric residual oils obtained by atmospheric distillation of crude oil such as paraffinic mineral oil, intermediate-based mineral oil, and naphthenic mineral oil; Distilled oil obtained by distilling the pressure residue under reduced pressure; the distilled oil is subjected to one or more purification processes such as solvent deburring, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, etc. Mineral oil applied; mineral oil obtained by isomerizing wax produced by the Fischer-Tropsch method (GTL wax (Gas To Liquids WAX)), and the like.
These mineral oils may be used alone or in combination of two or more.

Among these, from the viewpoint of obtaining a lubricating oil composition that satisfies the above condition (I), it is preferable that the mineral oil meets at least one of the following requirements. In addition, it becomes easy to prepare the lubricating oil composition which satisfy | fills the said conditions (I), so that it is the mineral oil which satisfy | fills these requirements more than one.
(1) A mineral oil obtained by isomerizing mineral oil and GTL wax that have been subjected to one or more purification treatments such as solvent removal, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, etc. about.
(2) A mineral oil classified into Group 2 or Group 3 of the American Petroleum institute (API) base oil category, or a mineral oil obtained by isomerizing GTL wax. (More preferably, it is a mineral oil classified into Group 3 or a mineral oil obtained by isomerizing a GTL wax.)
(3) Paraffinic mineral oil. In the present specification, the paraffinic mineral oil means a mineral oil having a paraffin content (% C _P ) of 60 or more (more preferably 65 or more, still more preferably 70 or more).
(4) A mineral oil having a naphthene content (% C _N ) of 5 to 40 (more preferably 10 to 35, still more preferably 15 to 30).
(5) _A mineral oil having an aromatic content (% C _A ) of 1.0 or less (more preferably 0.5 or less, still more preferably 0.1 or less, and still more preferably 0).
The values of paraffin content (% C _P ), naphthene content (% C _N ), and aromatic content (% C _A ) were measured by ASTM D-3238 ring analysis (ndM method). , Paraffin content, naphthene content, and aromatic content (percentage).

The kinematic viscosity at 100 ° C. of the base oil (A) is preferably 2.0 to 20.0 mm ² / s, more preferably 2.0 to 15.0 mm ² / s, still more preferably 2.0 to 12. 0 mm ² / s, even more preferably from 2.0 to 5.0 mm ² / s.
If the kinematic viscosity at 100 ° C. of the base oil (A) is 2.0 mm ² / s or more, it is preferable because the evaporation loss is small. On the other hand, if the kinematic viscosity at 100 ° C. of the base oil (A) is 20.0 mm ² / s or less, power loss due to viscous resistance can be suppressed, and a fuel efficiency improvement effect can be obtained.

  The viscosity index of the base oil (A) is preferably 80 or more, more preferably 95 or more, and still more preferably 105 or more, from the viewpoint of suppressing the viscosity change due to temperature change and improving fuel economy.

In the present specification, “kinematic viscosity at 100 ° C.” and “viscosity index” mean values measured in accordance with JIS K 2283.
Moreover, when base oil (A) is 2 or more types of mixed oil chosen from mineral oil and synthetic oil, it is preferable that the kinematic viscosity and viscosity index of the said mixed oil are the said range.

  In the lubricating oil composition of one embodiment of the present invention, the content of the mineral oil (A) is preferably 55% by mass or more, more preferably 60% by mass or more, based on the total amount (100% by mass) of the lubricating oil composition. Furthermore, it is more preferably 65% by mass or more, still more preferably 70% by mass or more, preferably 99.9% by mass or less, more preferably 99% by mass or less, and still more preferably 95% by mass or less.

<Synthetic oil>
In the lubricating oil composition of one embodiment of the present invention, a synthetic oil may be contained together with the mineral oil (A) as long as the effects of the present invention are not impaired.
Examples of the synthetic oil include an α-olefin homopolymer or an α-olefin copolymer (for example, an α-olefin copolymer having 8 to 14 carbon atoms such as an ethylene-α-olefin copolymer). Examples include poly α-olefins; isoparaffins; various esters such as polyol esters and dibasic acid esters; various ethers such as polyphenyl ethers; polyalkylene glycols; alkyl benzenes;
These synthetic oils may be used alone or in combination of two or more.

However, from the viewpoint of obtaining a lubricating oil composition that satisfies the condition (I), it is preferable that the content of the synthetic oil is small, and it is more preferable that the synthetic oil is not contained.
Specifically, in the lubricating oil composition of one embodiment of the present invention, the synthetic oil content is preferably 0 with respect to 100 parts by mass of the total amount of mineral oil (A) contained in the lubricating oil composition. -60 mass parts, More preferably, it is 0-40 mass parts, More preferably, it is 0-20 mass parts, More preferably, it is 0-15 mass parts.

<Ashless friction modifier (B)>
The ashless friction modifier (B) contained in the lubricating oil composition of the present invention has a function as a friction modifier and has one or more atoms selected from an oxygen atom, a nitrogen atom, a sulfur atom, and a phosphorus atom. An ashless compound having a polar group containing and an oleophilic group is preferable. Specifically, amine compounds, fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols, aliphatic ethers, urea compounds, hydrazide compounds Etc.
In the lubricating oil composition of one embodiment of the present invention, the ashless friction modifier (B) may be used alone or in combination of two or more.

  In the lubricating oil composition of one embodiment of the present invention, the content of the ashless friction modifier (B) is preferably 0.01 to 10% by mass based on the total amount (100% by mass) of the lubricating oil composition. More preferably, it is 0.05-8 mass%, More preferably, it is 0.10-5 mass%, More preferably, it is 0.30-3 mass%.

From the viewpoint of obtaining a lubricating oil composition that satisfies the condition (I), the ashless friction modifier (B) is preferably a compound that meets at least one of the following requirements.
In addition, the more the ashless friction modifier (B) is a compound that satisfies these requirements, the easier it is to prepare a lubricating oil composition that satisfies the above condition (I).
(1) A compound having an unsubstituted alkyl group having 10 to 30 carbon atoms or an unsubstituted alkenyl group having 10 to 30 carbon atoms. In addition, More preferably, it is a compound which has a C10-30 unsubstituted linear alkyl group or a C10-30 unsubstituted linear alkenyl group, More preferably, it is C10-30. A compound having an unsubstituted linear alkenyl group.
(2) The compound has one or more hydroxyl groups. More preferably, it is a compound having two or more hydroxyl groups, and more preferably a compound having one or more hydroxyl groups in a polar group.
(3) The compound described in the above (1) and (2) is a compound selected from fatty acid esters, aliphatic amines, fatty acid amides, and aliphatic ethers, more preferably fatty acid esters or fatty acid amines, More preferably, it is a fatty acid ester.

The compound satisfying the above (1) to (3) is adsorbed on the solid surface via a hydroxyl group that is a polar group, and an unsubstituted alkyl group or an unsubstituted alkenyl group that is a lipophilic group is perpendicular to the solid surface. By orienting in the direction, the base oil is considered to flow. Here, some of the mineral oil may be changed into a solid state depending on the contact pressure, but the unsubstituted alkyl group or the unsubstituted alkenyl group that is a lipophilic group dissolves the mineral oil that is in the process of changing into a solid state, It is considered that the formation of a solid adhesive structure by mineral oil is suppressed.
For example, when an alkyl group or alkenyl group that is a lipophilic group has a hydroxyl group as a substituent, the hydroxyl group is adsorbed on the solid surface, and the alkyl group or alkenyl group that is a lipophilic group is solid surface. It is presumed that the effect of suppressing the solidification of the mineral oil due to the contact pressure is hindered because it cannot be oriented in the vertical direction.
In addition, as described in (1) above, a compound having an unsubstituted alkenyl group having 10 to 30 carbon atoms has a double bond, so it is easy to orient in the direction perpendicular to the solid surface, and mineral oil due to contact pressure Since it is thought that the solidification suppression effect improves, it is preferable.
Furthermore, as described in (2) above, it is preferable that the number of hydroxyl groups is 2 or more because the amount of adsorption to the solid surface increases and the fluidity of mineral oil is considered to improve.

  From the viewpoint of a lubricating oil composition satisfying the condition (I), a fatty acid ester, an aliphatic amine, suitable as an ashless friction modifier (B), comprising the items (1) to (3) above, The fatty acid amide and the aliphatic ether will be specifically described below.

(Fatty acid ester)
Suitable fatty acid esters as the ashless friction modifier (B) include partial ester compounds having one or more hydroxyl groups such as partial ester compounds obtained by reaction of fatty acids with aliphatic polyhydric alcohols.

The fatty acid constituting the fatty acid ester is preferably a fatty acid having an unsubstituted alkyl group having 10 to 30 carbon atoms or an unsubstituted alkenyl group, and an unsubstituted linear alkyl group having 10 to 30 carbon atoms or an unsubstituted straight chain. A fatty acid having a chain alkenyl group is more preferred.
As carbon number of the alkyl group and alkenyl group which the said fatty acid has, it is 10-30, Preferably it is 12-24, More preferably, it is 14-20.

  Specific fatty acids include, for example, saturated fatty acids such as caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, and lignoceric acid; myristoleic acid, palmitoleic acid , Unsaturated fatty acids such as oleic acid and linolenic acid.

The aliphatic polyhydric alcohol constituting the fatty acid ester is preferably a divalent to hexavalent polyhydric alcohol, and specific examples include ethylene glycol, glycerin, trimethylolpropane, pentaerythritol, sorbitol, and the like.
Among these, glycerin is preferable as the aliphatic polyhydric alcohol.

Fatty acid partial ester compounds (hereinafter also referred to as “glycerin ester compounds”) obtained by the reaction of glycerin with the above fatty acids include glycerin monomyristate, glycerin monopalmitoleate, glycerin monooleate. And monoesters such as glycerin dimyristate, glycerin dipalmitreate, and glycerin dioleate.
Among these, as a glycerol ester compound, a monoester is preferable and the compound represented by the following general formula (b-1) is more preferable.

In the general formula (b-1), R ¹¹ represents an unsubstituted alkyl group having 10 to 30 carbon atoms or an unsubstituted alkenyl group having 10 to 30 carbon atoms, and an unsubstituted straight chain having 10 to 30 carbon atoms. It is preferably an alkyl group or an unsubstituted linear alkenyl group having 10 to 30 carbon atoms.
It may be selected as R ^11, as the number of carbon atoms in the alkyl group and alkenyl group each independently a 10-30, preferably 12-24, more preferably 14-20.

Moreover, in said general formula (b-1), R < ¹² > -R < ¹⁶ > represents a hydrogen atom or a C1-C18 hydrocarbon group each independently.
The number of carbon atoms of the hydrocarbon group that can be selected as R ^{12 to} R ¹⁶ is independently 1 to 18, preferably 1 to 12, more preferably 1 to 8, still more preferably 1 to 6, More preferably, it is 1-3.
Examples of the hydrocarbon group that can be selected as R ^{12 to} R ¹⁶ include an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, and an alkylaryl group.
Among these, as R < ¹² > -R < ¹⁶ >, a hydrogen atom, an alkyl group, or an alkenyl group is preferable, a hydrogen atom or an alkyl group is more preferable, and it is still more preferable that all are hydrogen atoms.

(Aliphatic amine)
As the aliphatic amine suitable as the ashless friction modifier (B), a compound represented by the following general formula (b-2) is preferable.

In the general formula (b-2), R ²¹ represents an unsubstituted alkyl group having 10 to 30 carbon atoms or an unsubstituted alkenyl group having 10 to 30 carbon atoms, and an unsubstituted straight chain having 10 to 30 carbon atoms. It is preferably a chain alkyl group or an unsubstituted straight chain alkenyl group having 10 to 30 carbon atoms.
It may be selected as R ^21, as the number of carbon atoms in the alkyl group and alkenyl group each independently a 10-30, preferably 12-24, more preferably 14-20.

In the general formula (b-2), R ^{22 to} R ²⁹ each independently represent a hydrogen atom, a hydrocarbon group having 1 to 18 carbon atoms, or an oxygen-containing hydrocarbon group containing an ether bond or an ester bond. Represent.
a and b are each independently an integer of 1 to 20, preferably an integer of 1 to 10, more preferably an integer of 1 to 5, still more preferably 1 or 2, and even more preferably 1.

Note that when a is 2 or more, for example, but R ²² there are a plurality, a plurality of R ²² may be the same or may be different from each other. The same applies when there are a plurality of R ^{23 to} R ²⁹ other than R ²² .
Moreover, as a sum of a and b, Preferably it is 2-20, More preferably, it is 2-10, More preferably, it is 2-4, More preferably, it is 2.

The number of carbon atoms of the hydrocarbon group that can be selected as R ^{22 to} R ²⁹ is independently 1 to 18, preferably 1 to 12, more preferably 1 to 8, still more preferably 1 to 6, More preferably, it is 1-3.
Examples of the hydrocarbon group that can be selected as R ^{22 to} R ²⁹ include an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, and an alkylaryl group.

The number of carbon atoms of the oxygen-containing hydrocarbon group that can be selected as R ^{22 to} R ²⁹ is independently 1 to 18, preferably 1 to 12, more preferably 1 to 8, still more preferably 1 to 18. 6, more preferably 1-3.
Examples of the oxygen-containing hydrocarbon group that can be selected as R ^{22 to} R ²⁹ include methoxymethyl group, ethoxymethyl group, propoxymethyl group, isopropoxymethyl group, n-butoxymethyl group, t-butoxymethyl group, and hexyl. Oxymethyl, octyloxymethyl, 2-ethylhexyloxymethyl, decyloxymethyl, dodecyloxymethyl, 2-butyloctyloxymethyl, tetradecyloxymethyl, hexadecyloxymethyl, 2-hexyldecyl Oxymethyl group, allyloxymethyl group, phenoxy group, benzyloxy group, methoxyethyl group, methoxypropyl group, 1,1-bismethoxypropyl group, 1,2-bismethoxypropyl group, ethoxypropyl group, (2-methoxy Ethoxy) propyl group, (1- Tyl-2-methoxy) propyl group, acetyloxymethyl group, propanoyloxymethyl group, butanoyloxymethyl group, hexanoyloxymethyl group, octanoyloxymethyl group, 2-ethylhexanoyloxymethyl group, decanoyloxy Examples thereof include a methyl group, dodecanoyloxymethyl group, 2-butyloctanoyloxymethyl group, tetradecanoyloxymethyl group, hexadecanoyloxymethyl group, 2-hexyldodecanoyloxymethyl group, and benzoyloxymethyl group.

Among these, as R ^{22 to} R ²⁹ , a hydrogen atom or a hydrocarbon group is preferable, a hydrogen atom, an alkyl group, or an alkenyl group is more preferable, a hydrogen atom or an alkyl group is further preferable, and all are hydrogen atoms. It is even more preferable.

(Fatty acid amide)
As the fatty acid amide suitable as the ashless friction modifier (B), a compound represented by the following general formula (b-3) is preferable.

In the general formula (b-3), R ³¹ represents an unsubstituted alkyl group having 10 to 30 carbon atoms or an unsubstituted alkenyl group having 10 to 30 carbon atoms, and is an unsubstituted straight chain having 10 to 30 carbon atoms. It is preferably a chain alkyl group or an unsubstituted straight chain alkenyl group having 10 to 30 carbon atoms.
It may be selected as R ^31, as the number of carbon atoms in the alkyl group and alkenyl group each independently a 10-30, preferably 12-24, more preferably 14-20.

In the general formula (b-3), R ^{32 to} R ³⁹ each independently represents a hydrogen atom, a hydrocarbon group having 1 to 18 carbon atoms, or an oxygen-containing hydrocarbon group containing an ether bond or an ester bond. Represent.
c and d are each independently an integer of 1 to 20, preferably an integer of 1 to 10, more preferably an integer of 1 to 5, still more preferably 1 or 2, and even more preferably 1.

Note that when a is 2 or more, for example, but R ³² there are a plurality, a plurality of R ³² may be the same or may be different from each other. The same applies when there are a plurality of R ^{33 to} R ³⁹ other than R ³² .
Moreover, as a sum total of c and d, Preferably it is 2-20, More preferably, it is 2-10, More preferably, it is 2-4, More preferably, it is 2.

The number of carbon atoms of the hydrocarbon group that can be selected as R ^{32 to} R ³⁹ is independently 1 to 18, preferably 1 to 12, more preferably 1 to 8, still more preferably 1 to 6, More preferably, it is 1-3.
Examples of the hydrocarbon group that can be selected as R ^{32 to} R ³⁹ include the same hydrocarbon groups as those selected as R ^{22 to} R ²⁹ described above.

The number of carbon atoms of the oxygen-containing hydrocarbon group that can be selected as R ^{32 to} R ³⁹ is independently 1 to 18, preferably 1 to 12, more preferably 1 to 8, still more preferably 1 to 18. 6, more preferably 1-3.
Examples of the oxygen-containing hydrocarbon group that can be selected as R ^{32 to} R ³⁹ include the same oxygen-containing hydrocarbon groups that can be selected as R ^{22 to} R ²⁹ described above.

(Aliphatic ether)
The aliphatic ether suitable as the ashless friction modifier (B) is preferably a (poly) glycerin ether compound, and more preferably a compound represented by the following general formula (b-4).

In the general formula (b-4), R ⁴¹ represents an unsubstituted alkyl group having 10 to 30 carbon atoms or an unsubstituted alkenyl group having 10 to 30 carbon atoms, and is an unsubstituted straight chain having 10 to 30 carbon atoms. It is preferably a chain alkyl group or an unsubstituted straight chain alkenyl group having 10 to 30 carbon atoms.
It may be selected as R ^41, as the number of carbon atoms in the alkyl group and alkenyl group each independently a 10-30, preferably 12-24, more preferably 14-20.
Moreover, e is an integer of 0-10, Preferably it is an integer of 0-6, More preferably, it is an integer of 0-4.

<Ashless type dispersant (C)>
The lubricating oil composition of one embodiment of the present invention may further contain one or more ashless dispersants (C) selected from alkenyl succinimide (C1) and boron-modified alkenyl succinimide (C2). preferable.
By containing the ashless dispersant (C), the dispersibility of the ashless friction modifier (B) in the mineral oil (A) becomes good, and the friction reduction effect can be further improved.

  Examples of the alkenyl succinimide (C1) include an alkenyl succinic monoimide represented by the following general formula (c-1) or an alkenyl succinic bisimide represented by the following general formula (c-2).

In the general formulas (c-1) and (c-2), R ^A , R ^A1 and R ^A2 are each independently an alkenyl group having a mass average molecular weight (Mw) of 500 to 3000 (preferably 1000 to 3000). It is.
R ^B , R ^B1 and R ^B2 are each independently an alkylene group having 2 to 5 carbon atoms.
R ^C is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a group represented by — (AO) _n —H (where A is an alkylene group having 2 to 4 carbon atoms, and n is an integer of 1 to 10). Is shown.)
x1 is an integer of 1 to 10, preferably an integer of 2 to 5, more preferably 3 or 4.
x2 is an integer of 0 to 10, preferably an integer of 1 to 4, more preferably 2 or 3.

Examples of the alkenyl group that can be selected as R ^A , R ^A1, and R ^A2 include a polybutenyl group, a polyisobutenyl group, and an ethylene-propylene copolymer. Among these, a polybutenyl group or a polyisobutenyl group is preferable.

The alkenyl succinimide (C1) can be produced, for example, by reacting an alkenyl succinic anhydride obtained by a reaction between a polyolefin and maleic anhydride with a polyamine.
Examples of the polyolefin include a polymer obtained by polymerizing one or more selected from α-olefins having 2 to 8 carbon atoms, and a copolymer of isobutene and 1-butene is preferable.
Examples of the polyamine include single diamines such as ethylenediamine, propylenediamine, butylenediamine, and pentylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, di (methylethylene) triamine, and dibutylene. And polyalkylene polyamines such as triamine, tributylenetetramine, and pentapentylenehexamine; piperazine derivatives such as aminoethylpiperazine; and the like.
Further, as the alkenyl succinimide (D1), the compounds represented by the general formulas (1) and (2) were reacted with alcohol, aldehyde, ketone, alkylphenol, cyclic carbonate, epoxy compound, organic acid, and the like. Modified alkenyl succinimides can also be used.

  In the lubricating oil composition of one embodiment of the present invention, the content of the alkenyl succinimide compound (C1) in terms of nitrogen atom is preferably 10 to 10% based on the total amount (100% by mass) of the lubricating oil composition. It is 3000 mass ppm, More preferably, it is 50-2000 mass ppm, More preferably, it is 100-1400 mass ppm, More preferably, it is 200-1200 mass ppm.

Examples of the boron-modified alkenyl succinimide (C2) include boron-modified alkenyl succinimides represented by the following general formula (c-1) or (c-2).
The boron-modified alkenyl succinimide (C2) can be produced, for example, by reacting alkenyl succinic anhydride obtained by the reaction of the above-mentioned polyolefin with maleic anhydride with the above-mentioned polyamine and boron compound.
Examples of the boron compound include boron oxide, boron halide, boric acid, boric anhydride, boric acid ester, ammonium salt of boric acid, and the like.

  In one embodiment of the present invention, the ratio of boron atom and nitrogen atom constituting the boron-modified alkenyl succinimide (C2) [B / N] is preferably 0.5 or more from the viewpoint of improving cleanliness. Preferably it is 0.6 or more, More preferably, it is 0.8 or more, More preferably, it is 0.9 or more.

  In the lubricating oil composition of one embodiment of the present invention, the boron-modified alkenyl succinimide (C2) content in terms of boron atoms is preferably 10 to 10% based on the total amount (100% by mass) of the lubricating oil composition. 1000 mass ppm, More preferably, it is 30-700 mass ppm, More preferably, it is 50-500 mass ppm, More preferably, it is 100-400 mass ppm.

  Further, the content of the boron-modified alkenyl succinimide (C2) in terms of nitrogen atom is preferably 10 to 1000 ppm by mass, more preferably 30 to 700, based on the total amount (100% by mass) of the lubricating oil composition. It is mass ppm, More preferably, it is 50-500 mass ppm, More preferably, it is 100-400 mass ppm.

In the lubricating oil composition of one embodiment of the present invention, as the ashless dispersant (C), an ashless dispersant other than components (C1) and (C2) may be used.
Examples of such other ashless dispersants include benzylamines, boron-containing benzylamines, succinic acid esters, fatty acids or monovalent or divalent carboxylic acid amides represented by succinic acid.

  However, in the lubricating oil composition of one embodiment of the present invention, the total content of the components (C1) and (C2) in the ashless dispersant (C) is the ashless system included in the lubricating oil composition. Preferably it is 70-100 mass% with respect to the whole quantity (100 mass%) of a dispersing agent (C), More preferably, it is 80-100 mass%, More preferably, it is 90-100 mass%, More preferably, it is 95-100 mass. %.

  In the lubricating oil composition of one embodiment of the present invention, the total content of the components (C1) and (C2) in terms of nitrogen atoms is usually 10 based on the total amount (100% by mass) of the lubricating oil composition. It is -4000 mass ppm, Preferably it is 30-3000 mass ppm, More preferably, it is 50-2500 mass ppm, More preferably, it is 100-2000 mass ppm, More preferably, it is 150-1500 mass ppm.

  The content (blending amount) of the component (C) is preferably 0.01 to 10.0% by mass, more preferably 0.1 to 8.0% based on the total amount (100% by mass) of the lubricating oil composition. It is 0.5 mass%, More preferably, it is 0.5-6.0 mass%, More preferably, it is 0.8-4.0 mass%.

<Other lubricant additives>
The lubricating oil composition of one embodiment of the present invention may contain additives for lubricating oil other than the components (B) and (C) as long as the effects of the present invention are not impaired.
Examples of such additives for lubricating oil include extreme pressure agents, antiwear agents, antioxidants, metal detergents, metal deactivators, rust inhibitors, viscosity index improvers, pour point depressants. And antifoaming agents.
These lubricant additives may be used alone or in combination of two or more.

Each content of these additives for lubricating oil can be appropriately adjusted within a range not impairing the effects of the present invention, but is usually 0.001 based on the total amount (100% by mass) of the lubricating oil composition. -15 mass%, preferably 0.005-10 mass%, more preferably 0.01-8 mass%.
In the lubricating oil composition of one embodiment of the present invention, the total content of these lubricating oil additives is preferably 0 to 20% by mass, based on the total amount (100% by mass) of the lubricating oil composition. More preferably, it is 0-15 mass%, More preferably, it is 0-10 mass%.

[Various properties of lubricating oil composition]
The kinematic viscosity at 100 ° C. of the lubricating oil composition of one embodiment of the present invention is preferably 3.0 to ²⁰ mm ² / s, more preferably 3.5 to 15 mm ² / s, still more preferably 4.0 to ¹⁰ mm ^2. / S.

  The viscosity index of the lubricating oil composition of one embodiment of the present invention is preferably 80 or higher, more preferably 95 or higher, and still more preferably 105 or higher.

About the lubricating oil composition of one embodiment of the present invention, the frictional energy calculated using a floating liner tester under the measurement conditions of a liner temperature of 75 ° C. and a rotation speed of 900 rpm is preferably 5.0 J / rotation or less, More preferably, it is 4.8 J / rotation or less, More preferably, it is 4.5 J / rotation or less.
In this specification, the floating liner tester 1 having the configuration shown in FIG. 3 is exemplified as the floating liner tester used for the measurement of the friction energy. The specification conditions of the floating liner tester are as described in the examples.

A floating liner testing machine 1 shown in FIG. 3 includes a block 2 having a piston motion path 2a and a crankshaft housing portion 2b, a liner 12 disposed along the inner wall of the piston motion path 2a, and a piston 4 housed in the liner 12. A piston ring 6 fitted on the piston 4, a crankshaft 10 housed in the crankshaft housing portion 2b, a connecting rod 9 connecting the crankshaft 10 and the piston 4, and a liner 12 and the piston motion path 2a. It has a load measuring sensor 14 that is sandwiched and measures a frictional force applied between the piston ring 6 and the liner 12 by the reciprocating motion of the piston 4.
The crankshaft 10 is rotationally driven by a motor and reciprocates the piston 4 via a connecting rod 9.
The load measuring sensor 14 is fixed to the liner 12 via a fixing screw 18.
As shown in FIG. 3, the floating liner testing machine 1 may include a thermometer 16 for measuring the temperature of the liner 12.
In the floating liner testing machine 1, the friction force applied between the piston ring 6 and the liner 12 due to the movement of the piston 4 is measured by the load measuring sensor 14.
In the floating liner testing machine 1 having the above-described configuration, the lubricating oil composition 20 is liquid in the crankshaft housing 2b that is higher than the center of the center axis of the crankshaft 10 and lower than the uppermost end of the center axis. It is filled until it becomes. Then, the lubricating oil composition 20 in the crankshaft housing portion 2 b is supplied between the liner 12 and the piston ring 6 in a splashing manner by the rotating crankshaft 10.

[Use of lubricating oil composition]
Since the lubricating oil composition of one aspect of the present invention has the above-described effects, the two sliding surfaces in which the surface roughness of the sliding surface is reduced by smoothing, coating, etc., and the clearance is adjusted to about several nanometers. Suitable for lubrication between members. In the lubricating oil composition of the present invention, even when used between such two sliding members, an increase in viscosity is effectively suppressed, and a stable and excellent friction reducing effect can be expressed. .
As a more specific application, it has a sliding mechanism with a piston ring and a liner in which the surface roughness of the sliding surface is reduced by smoothing, coating, etc., and the clearance is adjusted to about several nanometers. It is suitable as a lubricating oil composition for a sliding mechanism having a piston ring and a liner in an apparatus, and more particularly as a lubricating oil composition for a sliding mechanism having a piston ring and a liner in an internal combustion engine. is there.
There are no particular limitations on the material of the piston ring and cylinder liner to which the lubricating oil composition of one aspect of the present invention is applied, and a cast iron alloy is usually employed as the material of the cylinder liner in addition to the aluminum alloy.
As a material for the piston ring, Si-Cr steel or 11 to 17% by mass Cr martensitic stainless steel is used. It is preferable that the piston ring is further subjected to a base treatment related to a chromium plating treatment, a chromium nitride treatment, a nitridation treatment, or a combination thereof on such a material.
In particular, from the viewpoint of excellent friction reducing effect, adhesion, and durability, the lubricating oil composition of one embodiment of the present invention is slid with a piston ring and a liner using a piston ring subjected to chromium nitride treatment. When applied to a mechanism, the effects of the present invention can be further increased.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples. In addition, each physical property value of each component used by the Example and the comparative example and the obtained lubricating oil composition was measured based on the method below.

<Kinematic viscosity at 40 ° C. and 100 ° C.>
The measurement was performed according to JIS K 2283.
<Viscosity index>
Calculation was performed according to JIS K 2283.

Examples 1-3, Comparative Examples 1-3
(1) Preparation of sample oils (α1) to (α6) Mineral oil, friction modifier, and polybutenyl succinimide of the types and blending amounts shown in Table 1 are added, and sample oils (α1) to (α6) are added. Each was prepared.
Details of the mineral oil, friction modifier, and polybutenyl succinimide used in the preparation of the sample oils (α1) to (α6) are as follows.
<Mineral oil>
“Mineral oil (1)”: 100 ° C. kinematic viscosity = 3.0 mm ² / s, viscosity index = 109, paraffinic mineral oil classified into group 2 of the API base oil category. % C _P = 77,% C _N = 23,% C _A = 0.
“Mineral oil (2)”: 100 ° C. kinematic viscosity = 4.0 mm ² / s, viscosity index = paraffinic mineral oil classified in group 1 of 107 API base oil category. % C _P = 72,% C _N = 27,% C _A = 4.
“Mineral oil (3)”: 100 ° C. kinematic viscosity = 11 mm ² / s, viscosity index = 109, paraffinic mineral oil classified into group 2 of the API base oil category. % C _P = 72,% C _N = 28,% C _A = 0.
<Friction modifier>
"Friction modifier (1)": fatty acid glyceride. In the general formula (b-1), a compound in which R ¹¹ is an oleyl group, and R ^{12 to} R ¹⁶ are hydrogen atoms.
"Friction modifier (2)": diethanolamine oleate. In the general formula (b-2), R ²¹ is a straight-chain alkenyl group having 17 carbon atoms represented by “CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₇ —”, and R ^{22 to} R ²⁹ are A compound that is a hydrogen atom.
"Friction modifier (3)": glyceryl ether. In the general formula (b-4), a compound wherein R 41 is a straight-chain alkenyl group having 18 carbon atoms represented by “C ₁₈ H ₃₅ —”, and e is an integer of 0 to 4.
"Friction modifier (4)": 1- [N- (2-hydroxyethyl) -N-methylamino] hexadecyl-2-ol. A compound represented by the following formula.

<Polybutenyl succinimide>
In the general formula (c-2), R ^A1 and R ^A2 are polybutenyl groups having a number average molecular weight of 2000, R ^B1 and R ^B2 are —CH ₂ CH ₂ —, and R ^C is — (CH ₂ CH ₂ O) _2. Compound which is —H, content of nitrogen atom = 0.99% by mass.

(2) Measurement of surface force The relationship between the surface force of the sample oil and the value of the viscosity coefficient was measured using a resonance shear measuring device (advance Riko Co., Ltd., product name “RSM-1”).
Specifically, based on the method described in Reference Document 1 below, using the above-described resonance shear measurement apparatus, at room temperature (25 ° C.), between two surfaces facing a clean and smooth mica cleavage plane, About 200 μl of any one of the sample oils (α1) to (α6) was dropped and contacted in a straight cylindrical form. The surface force was calculated by the spring only method by measuring the distance between the solid surfaces by the uniform color order interference fringe method, calculating the displacement amount of the leaf spring from the measured value of the distance between the solid surfaces.
As for the resonance shear response, a voltage U _in is applied to the resonance shear unit to generate horizontal vibration, the voltage U _out is measured with a capacitance meter, and the vibration intensity [U _out / U _in ]. By analyzing the obtained resonance shear response (vibration intensity [U _out / U _in ]) by the method described in Reference Document 1 below, the viscosity coefficient was calculated.
・ Reference 1: A new physical model for resonance shear measurement of confined liquids between solid surfaces, REVIEW OF SCIENTIFIC INSTRUMENTS 79, 113705 2008
And while graphing the change of the value of the viscosity coefficient accompanying the change of surface force, the surface force x [mN / m] which satisfy | fills said Formula (i) was computed. The results are shown in Table 1.

(3) Preparation of lubricating oil composition Mineral oil, friction modifier, polybutenyl succinimide, and various additives shown below were added in the types and blending amounts shown in Table 2, and the lubricating oil compositions were respectively prepared. Prepared.
The mineral oil, friction modifier, and polybutenyl succinimide used were the same as those described above, and various additives shown below were used.
ZnDTP (1): primary alkyl zinc dialkyldithiophosphate, zinc atom content = 8.9% by mass, phosphorus atom content = 7.4% by mass.
-Antioxidant (1): Amine-based antioxidant-Antioxidant (2): Phenol-based antioxidant-Metal-based detergent (1): Overbased calcium salicylate, base number (perchloric acid method) = 350 mgKOH / g, content of calcium atom; 12.1% by mass.
Other additives: metal deactivators and antifoaming agents.

The prepared lubricating oil composition was subjected to the following floating liner test, and the friction energy between the piston ring and the liner was measured. The results are shown in Table 2.
<Floating liner test>
Using the floating liner tester having the configuration shown in FIG. 3 and adjusted so that the clearance between the piston ring and the liner of the following specifications is several nanometers, under the measurement conditions shown below, between the piston ring and the liner The frictional energy per rotation (unit: J / rotation) measured from the frictional force was calculated.
(1) Specifications and test equipment of floating liner tester: Floating liner tester driven by electric motor. Displacement: 315cm ³ (single cylinder)
・ Ring material: Steel (surface treatment CrN coating)
-Liner material: FC250 cast iron (2) Measurement conditions of floating liner tester-Liner temperature: 75 ° C
・ Rotation speed: 900rpm

DESCRIPTION OF SYMBOLS 1 Floating liner test machine 2 Block 2a Piston motion path 2b Crankshaft accommodating part 4 Piston 6 Piston ring 8 Piston ring 9 Connecting rod 10 Crankshaft 12 Liner 14 Load measuring sensor 16 Thermometer 18 Fixing screw 20 Lubricating oil composition

Claims (5)

A lubricating oil composition comprising a mineral oil (A) and an ashless friction modifier (B) and satisfying the following condition (I).
Condition (I): A sample oil (α) containing 1% by mass of the ashless friction modifier (B) and 5% by mass of polybutenyl succinimide is prepared together with the mineral oil (A). In contrast, when the value of the viscosity coefficient at a predetermined surface force is measured by using a resonance shear measuring device, the following formula (i)
Formula (i): μ (0) × 5 ≦ μ (x)
[In the above formula (i), μ (0) represents the value of the viscosity coefficient [Ns / m] at a surface force of 0 [mN / m]. μ (x) is the value of the viscosity coefficient at the surface force x [mN / m]. ]
X satisfying the condition is 5.0 [mN / m] or more.   The lubricating oil composition according to claim 1, wherein the ashless friction modifier (B) is a compound having an unsubstituted alkyl group having 10 to 30 carbon atoms or an unsubstituted alkenyl group having 10 to 30 carbon atoms. .   The lubricating oil composition according to claim 1 or 2, wherein the ashless friction modifier (B) is a compound having one or more hydroxyl groups.   The lubricating oil composition according to any one of claims 1 to 3, wherein the content of the ashless friction modifier (B) is 0.01 to 10% by mass based on the total amount of the lubricating oil composition. object.   Furthermore, 1 or more types of ashless type | system | group dispersing agents (C) chosen from an alkenyl succinimide (C1) and a boron-modified alkenyl succinimide (C2) are contained, As described in any one of Claims 1-4. Lubricating oil composition.