JP2018100329A - Mineral oil-based base oil, lubricant composition, internal combustion, and method for lubricating internal combustion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mineral oil-based base oil that can be converted into engine oil which has good low temperature viscosity characteristics such as fuel saving property at low temperature and low temperature startability of engine, and is excellent in high temperature cleaning property of a piston.SOLUTION: A mineral oil-based base oil satisfies the following requirements (I) to (V): Requirement (I): dynamic viscosity at 100°C of 2 mm/s or more and less than 7 mm/s; Requirement (II): viscosity index of 100 or more; Requirement (III): temperature gradient Δ|η*| of complex viscosity between two points of -10°C and -25°C measured on conditions of angular speed of 6.3 rad/s and strain amount of 0.1-100% using a rotation type rheometer of 60 Pa s/°C or less; Requirement (IV): content ratio [R1/R2] of monocyclic cycloparaffin (R1) content to di- to hexa-cyclic cycloparaffin content (R2) measured according to ASTM D 2786 of 0.70 or less in a volume ratio; and Requirement (V): %Cof less than 1.0.SELECTED DRAWING: None

Description

  The present invention relates to a mineral oil base oil, a lubricating oil composition using the mineral oil base oil, an internal combustion engine using the lubricating oil composition, and a lubricating method for the internal combustion engine.

In recent years, hybrid vehicles and vehicles equipped with an idling stop mechanism are increasing, but in these vehicles, the temperature of the engine oil is difficult to increase. Therefore, engine oils used in these vehicles are particularly required to further improve low-temperature viscosity characteristics such as fuel efficiency at low temperatures and low-temperature startability of engines.
Engine oil is also required to have not only such low-temperature viscosity characteristics but also good viscosity-temperature characteristics and low evaporation properties.

As an engine oil that has improved these various properties in a well-balanced manner, a lubricant base oil used as an engine oil that can meet the required performance of such an engine oil has been actively developed.
Patent Documents 1 to 4 disclose lubricating base oils in which specific physical property values are adjusted within a predetermined range.

JP 2008-274237 A JP 2012-153906 A JP 2007-016172 A JP 2006-241436 A

By the way, in order to improve low-temperature viscosity characteristics, it is common to improve the low-temperature viscosity characteristics of engine oil by blending a polymer component as a pour point depressant or viscosity index improver with a lubricating base oil. Has been done.
However, the presence of a polymer component blended as a pour point depressant or a viscosity index improver also becomes a factor of reducing the high temperature cleanliness of the piston of engine oil.
The engine oil using the lubricating base oil described in Patent Documents 1 to 4 has a problem in the high temperature cleanliness of the piston, and there is room for further improvement in the low temperature viscosity characteristics.
Therefore, there is a need for a lubricating oil composition that can be used as an engine oil with improved low-temperature viscosity characteristics and high-temperature cleanliness of the piston in a well-balanced manner.

  The present invention uses a mineral base oil and a mineral oil base oil that have good low-temperature viscosity characteristics such as fuel efficiency at low temperatures and low-temperature startability of the engine, and can be an engine oil excellent in high-temperature cleanliness of the piston. It is an object of the present invention to provide a lubricating oil composition, an internal combustion engine using the lubricating oil composition, and a method for lubricating the internal combustion engine.

  The present inventor has found that a mineral base oil prepared so as to satisfy specific requirements can solve the above-mentioned problems. The present invention has been completed based on this finding.

That is, the present invention provides the following [1] to [4].
[1] A mineral oil base oil that satisfies the following requirements (I) to (V).
· Requirement (I): kinematic viscosity at 100 ° C. is less than ^{2 mm} 2 / s or more ^{7 mm} 2 / s.
Requirement (II): Viscosity index is 100 or more.
Requirement (III): Complex viscosity between two points of −10 ° C. and −25 ° C. measured under the conditions of an angular velocity of 6.3 rad / s and a strain of 0.1 to 100% using a rotary rheometer. The temperature gradient Δ | η * | is 60 Pa · s / ° C. or less.
Requirement (IV): The content ratio [R1 / R2] of the monocyclic cycloparaffin content (R1) and the 2-6 cyclic cycloparaffin content (R2) measured in accordance with ASTM D 2786 is a volume ratio. And 0.70 or less.
- Requirements (V):% _{C A} is less than 1.0.
[2] A lubricating oil composition comprising the mineral oil base oil according to [1] above.
[3] An internal combustion engine having a sliding mechanism including a piston ring and a liner, and including the lubricating oil composition according to the above [2].
[4] A method for lubricating an internal combustion engine having a sliding mechanism including a piston ring and a liner, wherein the piston ring and the liner are lubricated using the lubricating oil composition according to the above [2]. Lubrication method.

  By using the mineral base oil of the present invention, a lubricating oil composition having excellent low-temperature viscosity characteristics such as low fuel consumption at low temperatures and low-temperature startability of an engine, and excellent high-temperature cleanliness of a piston can be easily prepared. can do.

Regarding the mineral oil base oil (2) of Example 2, the mineral oil base oil (a) of Comparative Example 1, and the mineral oil base oil (b) of Comparative Example 2, the relationship between temperature and complex viscosity η * was shown. It is a graph. It is a schematic diagram which shows the outline of a structure of the sliding mechanism provided with the piston ring and the liner.

In the present specification, the kinematic viscosity and the viscosity index at a predetermined temperature mean values measured according to JIS K2283: 2000.
In the present specification, the complex viscosity η * at a predetermined temperature is a value measured using a rotary rheometer under conditions of an angular velocity of 6.3 rad / s and a strain of 0.1 to 100%. Means a value measured by the method described in Examples. The “strain amount” is a measurement condition parameter that is appropriately set in accordance with the measurement temperature in the range of 0.1 to 100%.
In the present specification, the mass average molecular weight (Mw) and the number average molecular weight (Mn) of each component are values in terms of standard polystyrene measured by a gel permeation chromatography (GPC) method, specifically examples. Means a value measured by the method described in 1.
In the present specification, the CCS viscosity (low temperature viscosity) at −35 ° C. means a value measured in accordance with JIS K2010: 1993 (ASTM D 2602).
In the present specification, the naphthene content (% C _N ) and aromatic content (% C _A ) of the mineral base oil were measured by ASTM D-3238 ring analysis (ndM method). And the ratio (percentage) of the aromatic content.

[Mineral oil base oil]
Examples of the mineral base oil of the present invention include atmospheric residual oil obtained by atmospheric distillation of crude oil such as paraffinic mineral oil, intermediate mineral oil, and naphthenic mineral oil; obtained by vacuum distillation of the atmospheric residual oil. Distilled oil produced; The distillate was subjected to one or more treatments such as solvent degassing, solvent extraction, hydrofinishing, solvent dewaxing, catalytic dewaxing, isomerization dewaxing, and vacuum distillation. Mineral oil or wax (GTL wax etc.); etc. are mentioned.
These mineral oils may be used alone or in combination of two or more.

The mineral base oil of the present invention satisfies the following requirements (I) to (V).
· Requirement (I): kinematic viscosity at 100 ° C. is less than ^{2 mm} 2 / s or more ^{7 mm} 2 / s.
Requirement (II): Viscosity index is 100 or more.
Requirement (III): Complex viscosity between two points of −10 ° C. and −25 ° C. measured under the conditions of an angular velocity of 6.3 rad / s and a strain of 0.1 to 100% using a rotary rheometer. The temperature gradient Δ | η * | is 60 Pa · s / ° C. or less.
Requirement (IV): The content ratio [R1 / R2] of the monocyclic cycloparaffin content (R1) and the 2-6 cyclic cycloparaffin content (R2) measured in accordance with ASTM D 2786 is a volume ratio. And 0.70 or less.
- Requirements (V):% _{C A} is less than 1.0.

Moreover, it is preferable that the mineral oil base oil of one embodiment of the present invention further satisfies the following requirement (VI).
Requirement (VI): Using a rotary rheometer, the complex viscosity η * at −35 ° C. measured at an angular velocity of 6.3 rad / s and a strain of 0.1% is 60,000 Pa · s or less. is there.
In addition, when the mineral base oil of 1 aspect of this invention is a mixed oil which combined 2 or more types of mineral oil, the said mixed oil should just satisfy | fill the said requirements.
Hereinafter, said requirements (I)-(VI) are demonstrated.

<Requirement (I)>
The requirement (I) defines the balance between the evaporation loss of the mineral oil base oil and the fuel efficiency improvement effect.
That is, it is not preferable that the kinematic viscosity at 100 ° C. of the mineral base oil of the present invention is less than 2 mm ² / s because evaporation loss increases. On the other hand, if the kinematic viscosity at 100 ° C. is 7 mm ² / s or more, the power loss due to the viscous resistance becomes large, and there is a problem in terms of the fuel efficiency improvement effect.
The kinematic viscosity at 100 ° C. of the mineral base oil of one embodiment of the present invention is preferably 2.1 mm ² / s or more, more preferably 2.2 mm ² / s from the viewpoint of reducing the evaporation loss of the mineral oil base oil. Above, more preferably 2.5 mm ² / s or more, from the viewpoint of improving the fuel efficiency improvement effect of the mineral oil-based base oil, preferably 6 mm ² / s or less, more preferably 5.5 mm ² / s or less, still more preferably the ^{5 mm} 2 / s or less, even more preferably at most 4.7 mm ² / s.

<Requirement (II)>
Requirement (II) is a rule for making the mineral-oil base oil having good viscosity-temperature characteristics and fuel economy.
That is, when the viscosity index of the mineral base oil of the present invention is less than 100, the viscosity-temperature characteristics and fuel economy are significantly reduced, and the lubricating oil composition using the mineral oil base oil has fuel efficiency. Have problems in terms of.
From this viewpoint, the viscosity index of the mineral base oil of one embodiment of the present invention is preferably 105 or more, more preferably 110 or more.

Further, since the mineral base oil of the present invention satisfies the requirement (III) described later, even if the viscosity index is not relatively high, low temperature viscosity characteristics such as low fuel consumption and low temperature startability of the engine. It is possible to provide a lubricating oil composition in which
Therefore, the viscosity index of the mineral oil-based base oil of one embodiment of the present invention is preferably 145 or less, more preferably 140 or less, still more preferably 135 or less, and still more preferably less than 130.

<Requirement (III)>
The mineral base oil of the present invention was measured at −10 ° C. under the conditions of an angular velocity of 6.3 rad / s and a strain of 0.1 to 100% using a rotary rheometer as specified in requirement (III). And a temperature gradient Δ | η * | of the complex viscosity between two points of −25 ° C. (hereinafter, also referred to as “complex viscosity temperature gradient Δ | η * |” unless otherwise specified) is 60 Pa · s / ° C. The following is required.
The value of the “strain amount” in the requirement (III) is appropriately set in accordance with the temperature in the range of 0.1 to 100%.
The above-mentioned “temperature gradient Δ | η * | of the complex viscosity” indicates that the value of the complex viscosity η * at −10 ° C. and the value of the complex viscosity η * at −25 ° C. are independently or −10 ° C. To −25 ° C. or from −25 ° C. to −10 ° C. while continuously changing the temperature, and when the value is on the coordinate plane of the temperature-complex viscosity, it is between two points of −10 ° C. and −25 ° C. It is a value indicating the amount of change per unit of complex viscosity (absolute value of the slope). More specifically, it means a value calculated from the following calculation formula (f1).
Calculation formula (f1): temperature gradient Δ | η * | = | ([complex viscosity η * at −25 ° C.] − [Complex viscosity η *] at −10 ° C.) / (− 25 − (− 10) )) ｜

  The present inventor can obtain the effect of excellent low temperature viscosity characteristics such as fuel efficiency at low temperature and low temperature startability of the engine, and piston cleanliness by giving a specific relationship between the complex viscosity and temperature of the mineral oil base oil. In addition, it has been found that the component, composition, state, production conditions, etc. of the mineral oil base oil have a great influence on the relationship between the complex viscosity and the temperature.

FIG. 1 shows the temperature and complex viscosity η * for mineral oil base oil (2) of Example 2 described later, mineral oil base oil (a) of Comparative Example 1 and mineral oil base oil (b) of Comparative Example 2. It is the graph which showed the relationship.
Here, “temperature gradient Δ | η * | of complex viscosity” is the amount of change in complex viscosity in the temperature range of −25 ° C. to −10 ° C., that is, the slope of the graph shown in FIG.
In general, a “pour point”, which is a temperature immediately before solidification of a mineral oil base oil, is used as one evaluation index for low-temperature viscosity characteristics.
The present inventor has found that the temperature at which the complex viscosity suddenly increases and the “pour point” substantially coincide with each other, and even if the mineral oil has an approximate “pour point” as shown in the graph of FIG. It was found that the increase or decrease in complex viscosity is different in a low temperature environment where the temperature is lowered.
Based on this viewpoint, the present inventors have improved the low-temperature viscosity characteristics by considering a specific relationship between the complex viscosity and the temperature of the mineral base oil in a low-temperature environment where the temperature is further lowered from the pour point. Therefore, the present invention was completed.

In addition, as another method for evaluating low-temperature viscosity characteristics, there are cases where various viscosity values such as CCS viscosity and BF viscosity are used. In these evaluation methods, the low temperature environment of a mineral oil base oil is used. It cannot be said that the low-temperature viscosity characteristics are necessarily specified accurately.
That is, the mineral oil base oil contains a wax component, and forms a gel-like structure when the wax component precipitates in a low temperature environment below the pour point. This gel-like structure is fragile and its viscosity changes due to mechanical action. Therefore, even in the evaluation method of the low-temperature viscosity characteristic by the CCS viscosity, it is only a low-temperature apparent viscosity under a predetermined condition and is not a physical property that can sufficiently express the viscosity characteristic in a low-temperature environment.

  In addition, in order to prepare so as to satisfy the requirement (IV) described later, for example, mineral oil base oil obtained by refining raw material oil including bottom oil is a measurement that evaluates some low-temperature viscosity characteristics (for example, (Measurement of BF viscosity, etc.) may have an effect that the measured value tends to be unstable, and in such a case, the low-temperature viscosity characteristics cannot be accurately evaluated.

  Therefore, as a result of various investigations, the present inventors have focused on the above-mentioned “temperature gradient Δ | η * | of the complex viscosity”, and in mineral oil base oils that cannot be grasped by CCS viscosity, BF viscosity, or the like. The mineral oil base oil with improved low-temperature viscosity characteristics, taking into account the change in the coefficient of friction associated with the precipitation of the wax component, in consideration of the precipitation rate of the wax component contained in the oil was found, and the present invention was completed. Is.

  According to the study by the present inventors, the mineral oil base oil in which the temperature gradient Δ | η * | of the above complex viscosity exceeds 60 Pa · s / ° C. has a high precipitation rate of the wax and causes an increase in the friction coefficient. Cheap. As a result, the lubricating oil composition using the mineral oil base oil was found to have inferior fuel-saving performance in a low temperature environment.

Furthermore, the present inventors have developed a lubricating oil composition (engine oil) that improves the high-temperature cleanliness of the piston in each stage by using a mineral base oil having a small complex viscosity temperature gradient Δ | η * |. It has also been found that it can be prepared.
That is, as also shown in the examples described later, a lubricating oil composition using a mineral base oil having a complex viscosity temperature gradient Δ | η * | of 60 Pa · s / ° C. or less is high-temperature cleanliness of the piston. Was found to be good. Also, a lubricating oil composition comprising a mineral oil base oil having a complex viscosity temperature gradient Δ | η * | of 60 Pa · s / ° C. or less and a polymer component such as a pour point depressant that may cause deposits. Even in this case, the lubricating oil composition has a small increase in deposit, and the piston cleanliness is good.

From the above viewpoint, in the mineral base oil of one embodiment of the present invention, the temperature gradient Δ | η * | of the complex viscosity specified in the requirement (III) is preferably 50 Pa · s / ° C. or less, more preferably 20 Pa · s. / Pauses or less, more preferably 15 Pa · s / ° C or less, even more preferably 10 Pa · s / ° C or less, and particularly preferably 5 Pa · s / ° C or less.
In the mineral base oil of one embodiment of the present invention, the temperature gradient Δ | η * | of the complex viscosity specified in the requirement (III) is not particularly limited, but is preferably 0.001 Pa · s. / ° C. or higher, more preferably 0.01 Pa · s / ° C. or higher.

<Requirement (IV)>
The mineral base oil of the present invention has a content ratio [R1 / R2] of a monocyclic cycloparaffin (R1) and a 2-6 cycloparaffin (R2) measured in accordance with ASTM D 2786. The volume ratio needs to be 0.70 or less.
The cyclic paraffin component is also referred to as “naphthene component”, and corresponds to a monocyclic cycloparaffin component such as cyclopentane or cyclohexane, or a combination of two or more rings or one condensed cycloparaffin component.
The cyclic paraffin component includes those in which a hydrogen atom bonded to a ring-forming carbon atom forming a cyclic structure is substituted with various substituents.
The cyclic paraffin component includes unsaturated alicyclic compounds such as cyclopentene and cyclohexene having a double bond in the cyclic structure, but does not include aromatic compounds.

Generally, it is known that the cyclic paraffin content (naphthene content) contained in the mineral oil base oil causes a decrease in the viscosity index.
For this reason, mineral base oils used in engine oils are required to have good viscosity characteristics over a wide temperature range, and therefore have low cyclic paraffin content (naphthene content) (specifically,% _CN is less than 15) Base oil).

According to the study by the present inventors, it was found that the cause of the decrease in the viscosity index is due to the presence of “2-6 ring cycloparaffin (R2)”.
On the other hand, it was also found that the presence of 2-6 ring cycloparaffins (R2) contributes to the improvement of cleanliness.
The inventors of the present invention have repeatedly studied a mineral base oil that suppresses the lowering of the viscosity index, has good low-temperature viscosity characteristics, and can further improve cleanliness.
And while preparing so that the said requirements (III) may be satisfy | filled, as prescribed | regulated by the said requirements (IV), content ratio of 1 ring cycloparaffin part (R1) and 2-6 ring cycloparaffin parts (R2) If [R1 / R2] is a mineral base oil having a volume ratio of 0.70 or less, a high viscosity index can be maintained, low-temperature viscosity characteristics can be improved, and cleanliness can be further improved. Found out to get.

  In view of the above, in the mineral base oil of one embodiment of the present invention, the content of the monocyclic cycloparaffin (R1) and the 2-6 cyclic cycloparaffin (R2) as measured in accordance with ASTM D 2786 The ratio [R1 / R2] is preferably 0.66 or less, more preferably 0.62 or less, still more preferably 0.60 or less, and usually 0.01 or more in volume ratio.

  In the mineral base oil of one aspect of the present invention, from the viewpoint of improving low temperature viscosity characteristics and cleanliness, the total amount of paraffin in the mineral oil base oil measured according to ASTM D 2786 is 100% by volume, As content of 2-6 ring cycloparaffin (R2), Preferably it is 15-70 volume%, More preferably, it is 17-60 volume%, More preferably, it is 20-50 volume%, More preferably, it is 23-40 % By volume.

  In the mineral base oil of one aspect of the present invention, the content of monocyclic cycloparaffin (R1) relative to 100% by volume of the total amount of paraffin in the mineral oil base oil, measured in accordance with ASTM D 2786 Is preferably 3 to 29% by volume, more preferably 5 to 25% by volume, still more preferably 7 to 20% by volume, and still more preferably 10 to 18% by volume.

  In the mineral base oil of one aspect of the present invention, the non-paraffin content (R0) content relative to 100% by volume of the total amount of paraffin in the mineral oil base oil, measured according to ASTM D 2786, The amount is preferably 1 to 80% by volume, more preferably 10 to 75% by volume, still more preferably 20 to 70% by volume, and still more preferably 30 to 65% by volume.

In the present specification, the above-mentioned “contents of components (R0) to (R2) with respect to 100% by volume of the total amount of paraffin in the mineral oil base oil” are values calculated as follows.
Procedure (1): The contents of components (R0) to (R2) are determined in accordance with ASTM D2786.
Procedure (2): “Total content of components (R0), (R1) and (R2) obtained in procedure (1)” is defined as “total amount of paraffin”.
Procedure (3): Calculate the contents of components (R0) to (R2) with respect to 100% by volume of the total content (total amount of paraffin) of components (R0), (R1) and (R2).

In addition, according to the study by the present inventors, coking that can occur in a high-temperature environment by preparing a larger amount of cyclic paraffin (naphthene) in the mineral base oil satisfying the above requirement (III). It has also been found that the action of dissolving the is more expressed.
Therefore, by using the mineral base oil of the present invention, it is possible to produce a lubricating oil composition that further improves the high temperature cleanliness of the piston.

  From the above viewpoint, in the mineral oil base oil of one embodiment of the present invention, the monocyclic cycloparaffin content (R1) relative to 100% by volume of the total paraffin content in the mineral oil base oil measured according to ASTM D 2786 And the total content of 2-6 ring cycloparaffins (R2) is preferably 20% by volume or more, more preferably 25% by volume or more, still more preferably 30% by volume or more, and still more preferably 35% by volume or more. In particular, it is 40% by volume or more, and usually less than 100% by volume, preferably 99% by volume or less, more preferably 90% by volume or less, still more preferably 80% by volume or less, still more preferably 70% by volume or less. It is.

From the above viewpoint, the naphthene content (% C _N ) of the mineral base oil of one embodiment of the present invention is preferably 15 to 30, more preferably 16 to 30, still more preferably 18 to 30, and still more preferably. Is 20-30.

<Requirement (V)>
The mineral oil base oil of the present invention is required to have an aromatic content (% C _A ) of less than 1.0 as specified in the requirement (V). _A lubricating oil composition containing a mineral oil base oil having an aromatic content (% C _A ) adjusted to less than 1.0 can be excellent in high-temperature cleanliness of the piston.
From the above viewpoint, the aromatic content (% C _A ) of the mineral base oil of one embodiment of the present invention is preferably 0.1 or less, more preferably 0.01 or less.

In addition, from the viewpoint of a mineral base oil that can produce a lubricating oil composition having excellent high-temperature cleanliness of the piston, the mineral base oil of one aspect of the present invention satisfies the requirement (V) and has a sulfur content. The smaller the content, the better.
Specifically, the sulfur content of the mineral base oil of one embodiment of the present invention is preferably less than 500 ppm by mass, more preferably less than 100 ppm by mass.
In the present specification, the sulfur content of mineral oil base oil is a value measured according to JIS K2541-6: 2003 “Crude oil and petroleum products—Sulfur content test method”.

<Requirement (VI)>
Requirement (VI) is one of the indicators showing the low temperature viscosity characteristics of mineral oil base oils in a low temperature environment, independent of requirement (III).
A mineral oil base oil having a low complex viscosity η * at −35 ° C. specified in the requirement (VI) tends to have a low paraffin content. Therefore, by using the mineral oil base oil, it is possible to produce a lubricating oil composition having good low temperature viscosity characteristics such as fuel efficiency at low temperatures and low temperature startability of the engine, and improved high temperature cleanliness of the piston. .

From the above viewpoint, in the mineral base oil of one embodiment of the present invention, the complex viscosity η * at −35 ° C. defined by the requirement (VI) is preferably 60,000 Pa · s or less, more preferably 40 1,000 Pa · s or less, more preferably 10,000 Pa · s or less, still more preferably 6,000 Pa · s or less, still more preferably 2,000 Pa · s or less, and particularly preferably 500 Pa · s or less.
Further, the complex viscosity η * at −35 ° C. defined in the requirement (VI) is not particularly limited, but is preferably 0.1 Pa · s or more, more preferably 1 Pa · s or more, and further preferably 2 Pa. -It is more than s.

<Preparation example of mineral base oil satisfying requirements (I) to (VI)>
A mineral base oil that satisfies the above requirements (I) to (VI), particularly the above requirements (III) and (VI) can be easily prepared, for example, by appropriately considering the following matters. In addition, the following matters are examples of the preparation method, and the preparation can be performed by considering other matters.

(1) Preparation of Mass Average Molecular Weight of Mineral Oil Base Oil The mass average molecular weight (Mw) of the mineral oil base oil is the property defined in the above requirements (I) to (VI) (in particular, the above requirements (III) and (IV ) Is a physical property that affects the specified properties).
The mass average molecular weight (Mw) of the mineral oil base oil of one embodiment of the present invention is a mineral oil base oil satisfying the above requirements (I) to (VI), particularly the requirements (I), (III) and (IV). From the viewpoint, it is preferably 450 or less, and preferably 150 or more.

(2) Selection of raw material oil used as raw material of mineral oil base oil The mineral oil base oil of one embodiment of the present invention is preferably obtained by refining a raw material oil.
From the viewpoint of making the mineral oil base oil satisfying the above requirements (I) to (VI), in particular, the requirements (III), (IV) and (VI), the raw oil includes raw oils containing petroleum-derived waxes, and A raw material oil including a petroleum-derived wax and a bottom oil is preferable. Moreover, you may use raw material oil containing solvent dewaxing oil.

In the case of using a raw material oil including petroleum-derived wax and bottom oil, the content ratio [wax / bottom oil] of the wax and bottom oil in the raw material oil includes requirements (III), (IV) and (VI) From the viewpoint of making the mineral oil base oil satisfying, it is preferably 30/70 to 95/5, more preferably 55/45 to 95/5, still more preferably 70/30 to 95/5, and still more preferably in mass ratio. Is 80 / 20-95 / 5.
As the ratio of the bottom oil in the feedstock increases, the value of the temperature gradient Δ | η * | of the complex viscosity specified in requirement (III) tends to increase, and it is specified in requirement (VI). The value of complex viscosity η * at −35 ° C. is also likely to increase.
On the other hand, since the bottom oil contains a large amount of cyclic paraffin (naphthene) (particularly, 2 to 6-ring cycloparaffin (R2)), the requirement (IV) can be satisfied by using the raw oil containing the bottom oil. It becomes easy to prepare a mineral oil base oil to be filled. At the same time, a mineral oil base oil having a high cyclic paraffin content (naphthene content) can be prepared, and the resulting lubricating oil composition using the mineral oil base oil can improve the high-temperature cleanliness of the piston.

  As bottom oil, oil containing heavy fuel oil obtained from vacuum distillation equipment is hydrocracked in the normal fuel oil production process using crude oil as raw material, and remains after separating and removing naphtha and kerosene oil. A bottom fraction is mentioned.

  As wax, in addition to wax separated from the bottom fraction by solvent removal, crude oil such as paraffinic mineral oil, intermediate mineral oil, naphthenic mineral oil, etc. is distilled at atmospheric pressure to separate and remove naphtha and light oil. A wax obtained by dewaxing the atmospheric residue remaining after the solvent; a wax obtained by dewaxing the distillate obtained by subjecting the atmospheric residue to distillation under reduced pressure; and removing the distillate from the solvent; Examples include wax obtained by solvent dewaxing after solvent extraction and hydrogenation finish; GTL wax obtained by Fischer-Tropsch synthesis, and the like.

  On the other hand, examples of the solvent dewaxing oil include residual oil after the above bottom fraction and the like are dewaxed and the wax is separated and removed. The solvent dewaxing oil has been subjected to a solvent dewaxing refining process and is different from the above-described bottom oil.

As a method for obtaining wax by solvent dewaxing, for example, a method is preferred in which the bottom fraction is mixed with a mixed solvent of methylethylkenton and toluene, and the precipitate is removed while stirring in a low temperature region.
In addition, from the viewpoint of making the mineral base oil satisfying the requirements (III) and (VI), the specific temperature in the low temperature environment in the solvent dewaxing is lower than the temperature in general solvent dewaxing. Specifically, it is preferably −25 ° C. or lower, more preferably −30 ° C. or lower.

  The oil content of the raw material oil is preferably 5 to 55% by mass, more preferably 7 to 45% by mass, and still more preferably from the viewpoint of a mineral oil base oil that satisfies the requirements (III), (IV) and (VI). It is 10-35 mass%, More preferably, it is 15-32 mass%, Most preferably, it is 21-30 mass%.

The kinematic viscosity at 100 ° C. in the feedstock, from the viewpoint of the mineral base oil satisfying the requirement (I), preferably 2.0~7.0mm ² / s, more preferably 2.3～6.5Mm ² / S, more preferably 2.5 to 6.0 mm ² / s.
The viscosity index of the raw material oil is preferably 100 or more, more preferably 110 or more, and still more preferably 120 or more, from the viewpoint of a mineral oil base oil that satisfies the requirement (II).

(3) Setting of refining conditions for raw material oil It is preferable to prepare a mineral base oil satisfying the above requirements (I) to (VI) by subjecting the raw material oil to a refining treatment.
The purification treatment preferably includes at least one of hydroisomerization dewaxing treatment and hydrotreatment. In addition, it is preferable that the kind of refinement | purification process and refinement | purification conditions are set suitably according to the kind of feedstock to be used.

More specifically, from the viewpoint of obtaining a mineral oil base oil that satisfies the requirements (III) to (VI), it is preferable to select the refining treatment as follows according to the type of raw material oil to be used.
-When using raw material oil (α) containing the above-mentioned content ratio of petroleum-derived wax and bottom oil, both hydroisomerization dewaxing treatment and hydroprocessing are performed on the raw material oil (α). It is preferable to carry out a purification treatment.
-When using the raw material oil ((beta)) containing solvent dewaxing oil, it is preferable to perform the refinement | purification process including a hydrogenation process with respect to the said raw material oil ((beta)), without performing a hydroisomerization dewaxing process.

Since the above-mentioned raw material oil (α) includes a bottom oil, the aromatic content, sulfur content, and nitrogen content tend to increase. The presence of aromatic content, sulfur content, and nitrogen content causes a deposit when the lubricating oil composition is formed, and causes a decrease in high-temperature detergency of the piston.
By the hydroisomerization dewaxing treatment, the aromatic content, sulfur content, and nitrogen content can be removed, and the content thereof can be reduced.
In the hydroisomerization dewaxing treatment, the mineral oil base oil satisfying the requirements (III) and (VI) can be obtained by converting the linear paraffin in the wax into a branched isoparaffin.
In addition, since the aromatic component is ring-opened and converted to a paraffin component in accordance with the hydroisomerization dewaxing treatment, the aromatic component (% C _A ) can be reduced, and the mineral oil system that satisfies the requirement (V) Can be base oil.

  On the other hand, although the above-mentioned raw material oil (β) contains a wax, linear paraffin is precipitated and separated and removed in a low temperature environment by solvent dewaxing treatment. Therefore, it is specified in requirements (III) and (VI). The content of linear paraffin that affects the value of complex viscosity is low. Therefore, the necessity for performing “hydroisomerization dewaxing treatment” is low.

(Hydroisomerization dewaxing treatment)
As described above, hydroisomerization dewaxing treatment involves isomerization of straight-chain paraffin contained in the feed oil into branched-chain isoparaffin, ring-opening of aromatic components, conversion of paraffin components, sulfur content and nitrogen This is a purification process performed for the purpose of removing impurities such as fractions.
In particular, the presence of linear paraffin is one of the factors that increase the value of the temperature gradient Δ | η * | of the complex viscosity specified in requirement (III). The temperature gradient Δ | η * | of the complex viscosity is adjusted low.

The hydroisomerization dewaxing treatment is preferably performed in the presence of a hydroisomerization dewaxing catalyst.
As the hydroisomerization dewaxing catalyst, for example, a support such as silica aluminophosphate (SAPO) or zeolite, nickel (Ni) / tungsten (W), nickel (Ni) / molybdenum (Mo), cobalt (Co) / Catalysts supporting metal oxides such as molybdenum (Mo) and noble metals such as platinum (Pt) and lead (Pd).

  The hydrogen partial pressure in the hydroisomerization dewaxing treatment is preferably 2.0 from the viewpoint of a mineral base oil satisfying the requirements (III) to (VI) (particularly, the requirements (III) and (VI)). It is -220MPa, More preferably, it is 2.5-100MPa, More preferably, it is 3.0-50MPa, More preferably, it is 3.5-25MPa.

The reaction temperature in the hydroisomerization dewaxing treatment is a general hydroisomerization from the viewpoint of making the mineral base oil satisfying the requirements (III) to (VI) (particularly, the requirements (III) and (VI)). It is preferably set higher than the reaction temperature in the dewaxing treatment, specifically, preferably 320 to 480 ° C, more preferably 325 to 420 ° C, still more preferably 330 to 400 ° C, and still more preferably. Is 340-370 ° C.
Since the reaction temperature is high, isomerization of linear paraffin present in the feedstock can be promoted to branched isoparaffin, and requirements (III) to (VI) (especially, requirements (III) and Preparation of mineral oil base oil satisfying (VI)) becomes easy.

Moreover, as a liquid hourly space velocity (LHSV) in hydroisomerization dewaxing treatment, from the viewpoint of making a mineral oil base oil satisfying requirements (III) to (VI) (particularly, requirements (III) and (VI)). , Preferably 5.0 hr ⁻¹ or less, more preferably 2.0 hr ⁻¹ or less, further preferably 1.0 hr ⁻¹ or less, and even more preferably 0.6 hr ⁻¹ or less.
Further, from the viewpoint of improving productivity, LHSV in the hydroisomerization dewaxing treatment is preferably 0.1 hr ⁻¹ or more, more preferably 0.2 hr ⁻¹ or more.

The feed rate of the hydrogen gas in the hydroisomerization dewaxing process, the raw material Oil 1 kiloliter supplied, preferably 100 to 1000 nm ^3, more preferably 200 to 800 nm ^3, more preferably at 250～650Nm ³ is there.
In addition, in order to remove a light fraction, you may perform vacuum distillation with respect to the product oil performed to the hydroisomerization dewaxing process.

(Hydrogenation treatment)
The hydrogenation treatment is a purification treatment performed for the purpose of complete saturation of aromatics contained in the raw material oil and removal of impurities such as sulfur and nitrogen.
The hydrogenation treatment is preferably performed in the presence of a hydrogenation catalyst.
Examples of the hydrogenation catalyst include amorphous carriers such as silica / alumina and alumina, and crystalline carriers such as zeolite, nickel (Ni) / tungsten (W), nickel (Ni) / molybdenum (Mo), cobalt (Co ) / Metal oxide such as molybdenum (Mo), and a catalyst supporting a noble metal such as platinum (Pt) or lead (Pd).

  The hydrogen partial pressure in hydrotreating is the pressure in general hydrotreating from the viewpoint of making the mineral base oil satisfying requirements (III) to (VI) (particularly, requirements (III) and (VI)). It is preferably set higher than that, specifically, preferably 16 MPa or more, more preferably 17 MPa or more, still more preferably 20 MPa or more, and preferably 30 MPa or less, more preferably 22 MPa or less.

  The reaction temperature in the hydrotreatment is preferably 200 to 400 ° C., more preferably from the viewpoint of a mineral oil base oil that satisfies the requirements (III) to (VI) (particularly, the requirements (III) and (VI)). It is 250-350 degreeC, More preferably, it is 280-330 degreeC.

The liquid hourly space velocity (LHSV) in the hydrotreating is preferably 5.0 hr from the viewpoint of a mineral oil base oil that satisfies the requirements (III) to (VI) (particularly, the requirements (III) and (VI)). ^-1 or less, more preferably 2.0 hr ^-1 or less, more preferably not more 1.0 hr ^-1 or less, from the viewpoint of productivity, preferably 0.1 hr ^-1 or more, more preferably 0.2 hr ^{- 1} or more, more preferably 0.3 hr ⁻¹ or more.

The feed rate of the hydrogen gas in the hydrotreating, the supply Oil 1 kiloliter to be processed, preferably 100 to 1000 nm ^3, more preferably 200 to 800 nm ^3, more preferably 250~650Nm ^3.

  In addition, in order to remove a light fraction with respect to the product oil which performed the hydrogenation process, you may perform vacuum distillation. Various conditions (pressure, temperature, time, etc.) of the vacuum distillation are appropriately adjusted so that the kinematic viscosity of the mineral base oil at 100 ° C. falls within a desired range.

<Various physical properties of mineral oil base oil>
The CCS viscosity (low temperature viscosity) at −35 ° C. of the mineral base oil of one embodiment of the present invention is preferably 5,000 mPa · s or less, more preferably 4,000 mPa · s or less, and still more preferably 3,000 mPa · s. s or less, more preferably 2,500 mPa · s or less.

The mineral base oil of one embodiment of the present invention preferably satisfies the following requirement (P-1).
Requirement (P-1): Using the mineral oil base oil as a sample, it flows into the mineral base oil with respect to the deposit amount (W ₀ ) measured based on the panel coking test under the conditions described in the examples. The increase rate P of the deposit amount (W) measured based on the same panel coking test using a lubricating oil composition containing 0.1% by mass of a point depressant as a sample is 12% or less.
The increase rate P of the mass (W) of the deposit can also be expressed as “P (unit:%) = (W−W ₀ ) / W ₀ × 100”.
Since the mineral base oil of the present invention satisfies the requirement (III), it can not only provide a lubricating oil composition with good low-temperature viscosity characteristics, but also a factor of deterioration in cleanliness along with the mineral base oil. Even when the lubricating oil composition is blended with the polymer component, the high temperature cleanliness of the piston of the lubricating oil composition can be kept good.
The increase rate P specified in the above requirement (P-1) is an index of the high-temperature cleanliness of the piston of the resulting lubricating oil composition when the target mineral oil base oil is blended together with the polymer component. Is preferably as low as possible.
The increase rate P (%) of the deposit amount (W) is preferably 10% or less, more preferably 8.5% or less, and further preferably 7% or less.

[Lubricating oil composition]
The lubricating oil composition of the present invention contains at least the mineral oil base oil of the present invention described above, but may contain a synthetic oil together with the mineral oil base oil of the present invention.
Examples of the synthetic oil include poly α-olefin (PAO), ester compounds, ether compounds, polyglycols, alkylbenzenes, and alkylnaphthalenes.
These synthetic oils may be used alone or in combination of two or more.

  The content of the synthetic oil in the lubricating oil composition of the present invention is preferably 0 to 30 parts by mass, more preferably 100 parts by mass of the total amount of the mineral oil base oil of the present invention in the lubricating oil composition. It is 0-20 mass parts, More preferably, it is 0-15 mass parts, More preferably, it is 0-10 mass parts, Most preferably, it is 0-5 mass parts.

  The content of the mineral base oil of the present invention contained in the lubricating oil composition of one embodiment of the present invention is usually 50% by mass or more based on the total amount (100% by mass) of the lubricating oil composition, preferably 55% by mass or more, more preferably 60% by mass or more, still more preferably 65% by mass or more, still more preferably 70% by mass or more, and preferably 100% by mass or less, more preferably 99% by mass or less, Preferably it is 95 mass% or less.

In addition, the lubricating oil composition of the present invention may further contain a lubricating oil additive that is generally used as necessary, as long as the effects of the present invention are not impaired.
Examples of such lubricant additives include pour point depressants, viscosity index improvers, metal detergents, dispersants, antiwear agents, extreme pressure agents, antioxidants, antifoaming agents, and friction modifiers. , Rust preventives, metal deactivators and the like.
As the lubricant additive, a commercially available additive package containing a plurality of additives that conforms to the API / ILSAC SN / GF-5 standard or the like may be used.
Moreover, you may use the compound (For example, the compound which has a function as an antiwear agent and an extreme pressure agent) which has two or more functions as said additive.
Furthermore, each additive for lubricating oil 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 30% by mass based on the total amount of the lubricating oil composition (100% by mass). More preferably, it is 0-25 mass%, More preferably, it is 0-20 mass%, More preferably, it is 0-15 mass%.

(Pour point depressant)
Examples of the pour point depressant include ethylene-vinyl acetate copolymer, condensate of chlorinated paraffin and naphthalene, condensate of chlorinated paraffin and phenol, polymethacrylate, polyalkylstyrene, and the like. Is preferably used.

(Viscosity index improver)
Examples of the viscosity index improver include non-dispersed polymethacrylates, dispersed polymethacrylates, olefin copolymers (for example, ethylene-propylene copolymers), dispersed olefin copolymers, styrene copolymers. (For example, styrene-diene copolymer, styrene-isoprene copolymer, etc.).

The mass average molecular weight (Mw) of these viscosity index improvers is usually 500 to 1,000,000, preferably 5,000 to 800,000, more preferably 10,000 to 600,000. It is set appropriately according to the type of coalescence.
The non-dispersed and dispersed polymethacrylates used as viscosity index improvers are preferably 5,000 to 1,000,000, more preferably 10,000 to 800,000, still more preferably 20,000 to 500. , 000.
Moreover, in the olefin type copolymer used as a viscosity index improver, Preferably it is 800-1,000,000, More preferably, it is 1,000-800,000, More preferably, it is 10,000-600,000.

(Metal-based detergent)
Examples of the metal detergent include organic acid metal salt compounds containing a metal atom selected from alkali metals and alkaline earth metals, specifically, metal atoms selected from alkali metals and alkaline earth metals. Metal salicylate, metal phenate, metal sulfonate, and the like.
In the present specification, “alkali metal” refers to lithium, sodium, potassium, rubidium, cesium, and francium.
The “alkaline earth metal” refers to beryllium, magnesium, calcium, strontium, and barium.
As a metal atom contained in the metal-based detergent, sodium, calcium, magnesium, or barium is preferable, and calcium is more preferable from the viewpoint of improving cleanliness at high temperatures.

  As the metal salicylate, a compound represented by the following general formula (1) is preferable. As the metal phenate, a compound represented by the following general formula (2) is preferable. As the metal sulfonate, the following general formula (3 ) Is preferred.

In the general formulas (1) to (3), M is a metal atom selected from an alkali metal and an alkaline earth metal, preferably sodium, calcium, magnesium, or barium, and more preferably calcium. M ′ is an alkaline earth metal, preferably calcium, magnesium, or barium, and more preferably calcium. p is the valence of M and is 1 or 2. R is a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms. q is an integer of 0 or more, preferably an integer of 0 to 3.
Examples of the hydrocarbon group that can be selected as R include an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 18 ring carbon atoms, and 6 to 18 ring carbon atoms. Aryl groups having 7 to 18 carbon atoms, arylalkyl groups having 7 to 18 carbon atoms, and the like.

In one embodiment of the present invention, these metal detergents may be used alone or in combination of two or more.
Among these, it is preferable that it is 1 or more types chosen from a calcium salicylate, a calcium phenate, and a calcium sulfonate from a viewpoint of the improvement of the cleanliness at high temperature, and a soluble viewpoint to base oil.

In one embodiment of the present invention, the metal detergent may be any of a neutral salt, a basic salt, an overbased salt, and a mixture thereof.
The total base number of the metal detergent is preferably 0 to 600 mgKOH / g.
In one embodiment of the present invention, when the metal detergent is a basic salt or an overbased salt, the total base number of the metal detergent is preferably 10 to 600 mgKOH / g, more preferably Is 20-500 mg KOH / g.
In the present specification, the “base number” is the same as that in JIS K2501 “Petroleum products and lubricating oils—neutralization number test method”. Means the base number measured by the perchloric acid method according to the above.

(Dispersant)
Examples of the dispersant include succinimide, benzylamine, succinic acid ester, and boron-modified products thereof.
Examples of the succinimide include succinic acid having a polyalkenyl group such as polybutenyl group having a number average molecular weight of 300 to 4,000, and polyethylene such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine. Examples thereof include monoimide or bisimide of polyamine, or boron-modified products thereof; Mannich reaction product of phenol, formaldehyde and polyethylene polyamine having a polyalkenyl group.

(Antiwear agent)
Examples of the antiwear agent include zinc dialkyldithiophosphate (ZnDTP), zinc phosphate, zinc dithiocarbamate, molybdenum dithiocarbamate, molybdenum dithiophosphate, disulfides, sulfurized olefins, sulfurized fats and oils, sulfurized esters, and thiocarbonates. Sulfur-containing compounds such as thiocarbamates and polysulfides; phosphorus-containing compounds such as phosphites, phosphate esters, phosphonates, and amine salts or metal salts thereof; thiophosphites, Sulfur and phosphorus containing antiwear agents such as thiophosphates, thiophosphonates, and their amine or metal salts.
Among these, zinc dialkyldithiophosphate (ZnDTP) is preferable, and it is more preferable to use primary alkyl-type zinc dialkyldithiophosphate and zinc secondary alkyl-type dialkyldithiophosphate in combination.

(Extreme pressure agent)
Examples of extreme pressure agents include sulfur-based extreme pressure agents such as sulfides, sulfoxides, sulfones, thiophosphinates, halogen-based extreme pressure agents such as chlorinated hydrocarbons, and organometallic extreme pressure agents. It is done. Moreover, the compound which has a function as an extreme pressure agent among the above-mentioned antiwear agents can also be used.
In one embodiment of the present invention, these extreme pressure agents may be used alone or in combination of two or more.

(Antioxidant)
As the antioxidant, any one of known antioxidants conventionally used as an antioxidant for lubricating oils can be appropriately selected and used. For example, an amine-based antioxidant, a phenol-based antioxidant, and the like Antioxidants, molybdenum-based antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants and the like can be mentioned.
Examples of the amine-based antioxidant include diphenylamine and diphenylamine-based antioxidants such as alkylated diphenylamine having an alkyl group having 3 to 20 carbon atoms; α-naphthylamine, phenyl-α-naphthylamine, and alkyl having 3 to 20 carbon atoms. And naphthylamine-based antioxidants such as substituted phenyl-α-naphthylamine having a group;
Examples of phenolic antioxidants include 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, Monophenolic antioxidants such as isooctyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate Agents; Diphenolic antioxidants such as 4,4′-methylenebis (2,6-di-tert-butylphenol), 2,2′-methylenebis (4-ethyl-6-tert-butylphenol); hindered phenolic An antioxidant; and the like.
Examples of the molybdenum-based antioxidant include molybdenum amine complex formed by reacting molybdenum trioxide and / or molybdic acid with an amine compound.
Examples of the sulfur-based antioxidant include dilauryl-3,3′-thiodipropionate.
Examples of phosphorus antioxidants include phosphites.
In one embodiment of the present invention, these antioxidants may be used alone or in combination of two or more, but it is preferable to use in combination of two or more.

(Defoamer)
Examples of the antifoaming agent include silicone oil, fluorosilicone oil, and fluoroalkyl ether.

(Friction modifier)
Examples of the friction modifier include molybdenum-based friction modifiers such as molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (MoDTP), and amine salts of molybthenic acid; an alkyl group or alkenyl group having 6 to 30 carbon atoms in the molecule. Ashless friction modifiers such as aliphatic amines, fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols, aliphatic ethers, etc .; oils and fats, amines, amides, sulfurized esters, phosphate esters, phosphites And phosphate ester amine salts.

(Rust inhibitor)
Examples of the rust inhibitor include fatty acid, alkenyl succinic acid half ester, fatty acid soap, alkyl sulfonate, polyhydric alcohol fatty acid ester, fatty acid amine, oxidized paraffin, alkyl polyoxyethylene ether and the like.

(Metal deactivator)
Examples of the metal deactivator include benzotriazole compounds, tolyltriazole compounds, thiadiazole compounds, imidazole compounds, pyrimidine compounds, and the like.
In one embodiment of the present invention, these metal deactivators may be used alone or in combination of two or more.

<Aspect of Lubricating Oil Composition of the Present Invention>
The lubricating oil composition of one aspect of the present invention contains a base oil containing the mineral base oil of the present invention described above, and the content of the additive for lubricating oil comprising a polymer component is 10% by mass or less. Lubricating oil composition (X-1) is mentioned.
The polymer component contained as an additive for lubricating oil is a component that causes coking that causes a decrease in high temperature cleanliness of the piston, and means a compound having at least one repeating unit.
However, since the lubricating oil composition (X-1) uses a mineral base oil that satisfies the above requirement (III) as the base oil, even if coking occurs from the polymer component, the coking is dissolved. The high temperature cleanliness of the piston can be kept good.

Examples of the polymer component that causes the occurrence of coking include a viscosity index improver and a pour point depressant, and in particular, polymethacrylate contained as a viscosity index improver and a pour point depressant.
Further, the mass average molecular weight of the polymer component that causes the occurrence of coking is usually 100,000 or less.
In the lubricating oil composition (X-1), the content of the polymer component that causes such coking is adjusted.

  In addition, as a specific aspect of lubricating oil composition (X-1), content of a lubricating oil composition (X-11) whose content of a pour point depressant is 10 mass% or less, and a viscosity index improver Oil composition (X-12) having a content of 10% by mass or less, lubricating oil composition (X-13) having a polymethacrylate content of 10% by mass or less, and a polymer component having a mass average molecular weight of 100,000 or less The lubricating oil composition (X-14) having a content of 10% by mass or less is included.

  In the lubricating oil composition (X-1), the content of the additive for lubricating oil composed of a polymer component is preferably based on the total amount (100% by mass) of the lubricating oil composition (X-1). It is 0.01-10 mass%, More preferably, it is 0.03-7 mass%, More preferably, it is 0.05-5 mass%, More preferably, it is 0.1-3 mass%.

Moreover, as a lubricating oil composition of another aspect of the present invention, a lubricating oil composition containing a base oil containing the above-described mineral oil-based base oil of the present invention and substantially free of the above-described polymer component (Y- 1).
Here, “substantially free of polymer component” means that the content of the polymer component is less than 0.01% by mass (preferably based on the total amount (100% by mass) of the lubricating oil composition (B)). Means less than 0.001% by mass, more preferably 0% by mass (not detected).

Since the lubricating oil composition (Y-1) does not substantially contain the above-described polymer component that causes a decrease in the high temperature cleanliness of the piston, it has excellent piston cleanliness.
In addition, as a specific aspect of lubricating oil composition (Y-1), lubricating oil composition (Y-11) which does not contain a pour point depressant substantially, lubrication which does not contain a viscosity index improver substantially. Oil composition (Y-12), lubricating oil composition substantially free of polymethacrylate (Y-13), lubricating oil composition substantially free of polymer component having a weight average molecular weight of 100,000 or less (Y -14).

<Method for producing lubricating oil composition>
Although there is no restriction | limiting in particular as a manufacturing method of the lubricating oil composition of this invention, The base oil containing the mineral base oil of this invention is used as a manufacturing method of the lubricating oil composition containing the above-mentioned additive for lubricating oil. In addition, the method preferably includes a step of blending the additive for lubricating oil.
In addition, in the said process, the suitable compound of each additive for lubricating oil to mix | blend and content of each component are as above-mentioned.

It is preferable to add the lubricant additive to the base oil containing the mineral base oil of the present invention and then uniformly stir the lubricant additive in the base oil by stirring by a known method.
In addition, from the viewpoint of uniformly dispersing the additive for lubricating oil, the base oil containing the mineral base oil of the present invention is heated to 40 to 70 ° C., and then the additive for lubricating oil is blended and stirred uniformly. More preferably, it is dispersed.

  In addition, after blending the additive for lubricating oil with the base oil containing the mineral base oil of the present invention, a part of the base oil or the additive for lubricating oil is modified, or the two components react with each other, and another component is added. When produced, the resulting lubricating oil composition corresponds to the lubricating oil composition obtained by the method for producing a lubricating oil composition of the present invention, and belongs to the technical scope of the present invention.

<Various physical 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 4 mm ² / s or more, more preferably 5 mm ² / s or more, still more preferably 6 mm ² / s or more, and even more preferably 7 mm. ² / s or more, preferably less than 15 mm ² / s, more preferably less than 12.5 mm ² / s, still more preferably less than 11 mm ² / s, and still more preferably less than 10 mm ² / s.

  The viscosity index of the lubricating oil composition of one embodiment of the present invention is preferably 140 or more, more preferably 150 or more, and still more preferably 160 or more.

As the temperature gradient Δ | η * | of the complex viscosity between two points of −10 ° C. and −25 ° C., which is defined in the same manner as the requirement (III) of the lubricating oil composition of one embodiment of the present invention, Is 60 Pa · s / ° C. or less, more preferably 20 Pa · s / ° C. or less, further preferably 15 Pa · s / ° C. or less, still more preferably 10 Pa · s / ° C. or less, particularly preferably 5 Pa · s / ° C. or less. .
In the lubricating oil composition of one embodiment of the present invention, the temperature gradient Δ | η * | of the complex viscosity defined in the same manner as the requirement (III) described above is not particularly limited, but is preferably Is 0.001 Pa · s / ° C. or more, more preferably 0.01 Pa · s / ° C. or more.

The complex viscosity η * at −35 ° C. defined in the same manner as the above-mentioned requirement (IV) of the lubricating oil composition of one embodiment of the present invention is preferably 45,000 Pa · s or less, more preferably 35,000 Pa. · S or less, more preferably 6,000 Pa · s or less, still more preferably 2,000 Pa · s or less, and particularly preferably 500 Pa · s or less.
Further, in the lubricating oil composition of one embodiment of the present invention, the complex viscosity η * at −35 ° C. defined in the same manner as the above requirement (IV) is not particularly limited, but is preferably 0. 1 Pa · s or more, more preferably 1 Pa · s or more, and further preferably 2 Pa · s or more.

  The CCS viscosity (low temperature viscosity) at −35 ° C. of the lubricating oil composition of one embodiment of the present invention is preferably 9,000 mPa · s or less from the viewpoint of a lubricating oil composition having good low temperature viscosity characteristics. It is preferably 8,600 mPa · s or less, more preferably 7,500 mPa · s or less, and still more preferably 7,000 mPa · s or less.

The HTHS viscosity (high temperature and high shear viscosity) at 150 ° C. of the lubricating oil composition of one embodiment of the present invention is preferably 1.4 mPa · s or more and less than 3.5 mPa · s, more preferably 1.6 mPa · s or more and 3 or more. Less than 2 mPa · s, more preferably 1.7 mPa · s to less than 3.0 mPa · s, and still more preferably 2.0 mPa · s to less than 2.8 mPa · s.
If the HTHS viscosity at 150 ° C. is 1.4 mPa · s or more, a lubricating oil composition having good lubricating performance can be obtained. On the other hand, if the HTHS viscosity at 150 ° C. is less than 3.5 mPa · s, a decrease in viscosity characteristics at low temperatures can be suppressed, and a lubricating oil composition having good fuel economy can be obtained.
The HTHS viscosity at 150 ° C. can also be assumed as a viscosity under a high temperature region during high-speed operation of the engine. In other words, if the HTHS viscosity at 150 ° C. of the lubricating oil composition falls within the above range, the lubricating oil composition has good properties such as viscosity under a high temperature range assuming high speed operation of the engine. I can say that.
In addition, the HTHS viscosity at 150 ° C. of the above lubricating oil composition is a value measured according to ASTM D4741, and more specifically means a value measured by the method described in Examples.

In one embodiment of the present invention, a lubricating oil composition having a kinematic viscosity at 100 ° C. of less than 12.5 mm ² / s and an HTHS viscosity at 150 ° C. of less than 3.5 mPa · s is preferred.
By satisfying the above requirements, the lubricating oil composition can reduce fluid friction and improve fuel saving performance.

The density at 15 ° C. of the lubricating oil composition of one embodiment of the present invention is preferably 0.80 to 0.90 g / cm ³ , more preferably 0.82 to 0.87 g / cm ³ .
In addition, the density in 15 degreeC of said lubricating oil composition means the value measured based on JISK2249: 2011.

  In the lubricating oil composition of one embodiment of the present invention, the amount of deposit measured by a panel coking test under the conditions described in the examples is preferably less than 100 mg, more preferably less than 90 mg, still more preferably less than 85 mg, Even more preferably, it is less than 80 mg.

<Use of lubricating oil composition>
The lubricating oil composition of the present invention has good low-temperature viscosity characteristics such as fuel efficiency at low temperatures and low-temperature startability of the engine, and even when a polymer component is blended as an additive, it results from the polymer component. Excellent in suppressing the deterioration of the high temperature cleanliness of the piston.
Therefore, examples of the engine filled with the lubricating oil composition of the present invention include engines for vehicles such as automobiles, trains, airplanes, etc., but engines for automobiles are preferable, and engines for automobiles equipped with a hybrid mechanism or an idling stop mechanism are included. Is more preferable.
The lubricating oil composition of one embodiment of the present invention is suitable for use as a lubricating oil composition for internal combustion engines (engine oil for internal combustion engines) used in vehicles such as automobiles, trains, and aircrafts. It can be applied to other uses.
Other possible uses for the lubricating oil composition of one aspect of the present invention include, for example, power steering oil, automatic transmission oil (ATF), continuously variable transmission oil (CVTF), hydraulic fluid, turbine oil, compressor oil, Examples include machine tool lubricating oil, cutting oil, gear oil, fluid bearing oil, rolling bearing oil, and the like.

The lubricating oil composition of the present invention comprises a piston ring and a sliding mechanism provided with a liner in a device having a sliding mechanism provided with a piston ring and a liner, particularly a piston ring in an internal combustion engine (preferably an automobile internal combustion engine) and It is suitable for lubrication of a sliding mechanism provided with a liner.
There is no restriction | limiting in particular about the formation material of the piston ring and cylinder liner to which the lubricating oil composition of this invention is applied. Examples of the material for forming the cylinder liner include aluminum alloys and cast iron alloys.
Examples of the material for forming the piston ring include Si-Cr steel and martensitic stainless steel containing 11 to 17% by mass of chromium. In addition, it is preferable that the piston ring is further subjected to a base treatment according to a chromium plating treatment, a chromium nitride treatment, a nitridation treatment, or a combination thereof on such a forming material.

[Internal combustion engine]
The present invention also provides an internal combustion engine having a sliding mechanism including a piston ring and a liner, and including the above-described lubricating oil composition of the present invention.
In one aspect of the present invention, an internal combustion engine in which the lubricating oil composition of the present invention is applied to the sliding portion of the sliding mechanism is preferable.
In addition, about the sliding mechanism provided with the lubricating oil composition of this embodiment, the piston ring, and the liner, it is as above-mentioned, As a structure of a specific sliding mechanism, what is shown in FIG. 2 is mentioned.

2 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, a piston 4 housed in the liner 12, It is sandwiched between a piston ring 6 fitted on the piston 4, a crankshaft 10 housed in the crankshaft housing 2b, a connecting rod 9 connecting the crankshaft 10 and the piston 4, and a liner 12 and the piston motion path 2a. Have a structured.
The crankshaft 10 is rotationally driven by a motor (not shown) and can reciprocate the piston 4 via a connecting rod 9.
In the sliding mechanism 1 configured as described above, the lubricating oil composition 20 of the present invention is higher in the crankshaft housing 2b 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 the liquid level is reached. 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.

[Lubrication method of internal combustion engine]
The present invention is a method of lubricating an internal combustion engine that lubricates a device having a sliding mechanism including a piston ring and a liner, and the piston ring and the liner are lubricated using the above-described lubricating oil composition of the present invention. An internal combustion engine lubrication method is also provided.
The sliding mechanism provided with the lubricating oil composition, piston ring and liner of the present embodiment is as described above.
In the lubricating method of the internal combustion engine of the present invention, the lubricating oil composition of the present embodiment is used as a lubricating oil in the sliding portion between the piston ring and the cylinder liner, so that both in fluid lubrication and mixed lubrication, This friction can be greatly reduced, contributing to improved fuel economy.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples. In addition, the measuring method or evaluation method of various physical properties is as follows.

<Measuring method of various physical properties of mineral oil base oil or lubricating oil composition>
(1) Kinematic viscosity at 40 ° C. and 100 ° C. Measured according to JIS K2283: 2000.
(2) Viscosity index Measured according to JIS K2283: 2000.
(3) CCS viscosity at −35 ° C. Measured according to JIS K2010: 1993 (ASTM D 2602).
(4) Complex viscosity η * at −25 ° C., −10 ° C., and −35 ° C.
Using a rheometer “Physica MCR 301” manufactured by Anton Paar, the following procedure was used.
First, a mineral base oil or lubricating oil composition to be measured is inserted into a cone plate (diameter 50 mm, inclination angle 1 °) adjusted to any one of −25 ° C., −10 ° C., and −35 ° C. And held at the same temperature for 10 minutes. At this time, attention was paid not to give distortion to the inserted solution.
Then, at a predetermined measurement temperature, an angular velocity of 6.3 rad / s and a strain amount of 0.1 to 100% in a vibration mode under the conditions of values appropriately set according to the measurement temperature. The complex viscosity η * was measured. In the measurement of the complex viscosity η * at −35 ° C., the strain amount was “0.1%”.
Then, from the value of the complex viscosity η * at −25 ° C. and −10 ° C., “temperature gradient Δ | η * | of the complex viscosity” was calculated from the calculation formula (f1).
(5) Mass average molecular weight (Mw), number average molecular weight (Mn)
Using a gel permeation chromatograph device (manufactured by Agilent, “1260 HPLC”), the measurement was performed under the following conditions, and values measured in terms of standard polystyrene were used.
(Measurement condition)
Column: Two “Shodex LF404” connected in sequence.
-Column temperature: 35 ° C
・ Developing solvent: Chloroform ・ Flow rate: 0.3 mL / min

<Methods for measuring various physical properties of mineral oil base oil>
(6) Aromatic content (% C _A ), naphthene content (% C _N )
Measured by ASTM D-3238 ring analysis (ndM method).
(7) Sulfur content It measured based on JISK2541-6: 2003.
(8) Nitrogen content JIS K2609: 1998 Measured according to

(9) Type analysis of paraffin content (content per component)
Based on ASTM D2786, the contents of the acyclic paraffin and the 1-6 ring cycloparaffins in the mineral base oil were determined.
In addition, the content of the acyclic paraffin content (R0) and the content of the 1-ring cycloparaffin content (R1) with respect to 100% by volume of the total amount of the paraffin content consisting of the acyclic paraffin content and the 1-6 ring cycloparaffin content, And the content of 2-6 ring cycloparaffins (R2) was calculated, respectively. Further, the content ratio [R1 / R2] (volume ratio) of the monocyclic cycloparaffin (R1) and the 2-6 cyclic cycloparaffin (R2) was also calculated.

<Methods for measuring various physical properties of lubricating oil composition>
(10) HTHS viscosity at 150 ° C. (high temperature high shear viscosity)
Based on ASTM D4741, the viscosity after shearing the lubricating oil composition to be measured at 150 ° C. at a shear rate of 10 ⁶ / s was measured.

  The production methods of “bottom oil” and “slack wax” used in Examples and Comparative Examples are as follows.

Production Example 1 (Manufacture of bottom oil)
In a normal fuel oil production process, oil containing heavy fuel oil obtained from a vacuum distillation apparatus was hydrocracked, and the bottom fraction remaining after separating and removing naphtha and kerosene oil was taken out. The bottom fraction was used as the “bottom oil” in the following production.
The bottom oil had an oil content of 75% by mass, a sulfur content of 82 mass ppm, a nitrogen content of 2 mass ppm, a kinematic viscosity at 100 ° C. of 4.1 mm ² / s, and a viscosity index of 134.

Production Example 2 (Production of solvent dewaxed oil and slack wax)
The bottom oil obtained as described above was subjected to solvent dewaxing in a low temperature region of −35 ° C. to −30 ° C. using a mixed solvent of methyl ethyl ketone and toluene to separate the wax to obtain “solvent dewaxed oil”. . The separated wax was designated as “slack wax”.
The solvent dewaxed oil had an oil content of 100 mass%, a sulfur content of 70 mass ppm, a nitrogen content of 2 mass ppm, a kinematic viscosity at 100 ° C. of 4.1 mm ² / s, and a viscosity index of 121. It was.
The slack wax had an oil content of 15% by mass, a sulfur content of 12 ppm by mass, a nitrogen content of less than 1 ppm by mass, a kinematic viscosity at 100 ° C. of 4.2 mm ² / s, and a viscosity index of 169. .

Example 1 (Production of mineral oil base oil (1))
The solvent dewaxed oil obtained in Production Example 2 was used as the raw material oil (i).
The raw material oil (i) was subjected to hydrogenation using a nickel tungsten catalyst under the conditions of a hydrogen partial pressure of 20 MPa, a reaction temperature of 280 to 320 ° C., and LHSV 1.0 hr ⁻¹ .
The hydrotreated oil was distilled under reduced pressure, and a fraction having a kinematic viscosity at 100 ° C. in the range of 4.2 to 4.4 mm ² / s was recovered to obtain a mineral oil base oil (1).
For the mineral oil base oil (1), the aromatic content (% C _A ) = 0.0, the naphthene content (% C _N ) = 26.5, the sulfur content = less than 100 ppm by mass, and the mass average molecular weight = 150 to 450 there were.

Example 2 (Production of mineral oil base oil (2))
A mixture of 75 parts by mass of slack wax obtained in Production Example 2 and 25 parts by mass of bottom oil obtained in Production Example 1 was used as raw material oil (ii). The raw material oil (ii) has an oil content of 30% by mass, a sulfur content of 30 ppm by mass, a nitrogen content of less than 1 ppm by mass, a kinematic viscosity at 100 ° C. of 4.2 mm ² / s, and a viscosity index of 160. Met.
The above raw material oil (ii) was subjected to hydroisomerization dewaxing using a hydroisomerization dewaxing catalyst under conditions of a hydrogen partial pressure of 4 MPa, a reaction temperature of 335 ° C., and LHSV of 1.0 hr ⁻¹ .
Next, the hydroisomerized and dewaxed product oil was hydrotreated using a nickel tungsten catalyst under the conditions of a hydrogen partial pressure of 20 MPa, a reaction temperature of 280 to 320 ° C., and LHSV of 1.0 hr ⁻¹ .
The hydrotreated oil was distilled under reduced pressure, and a fraction having a kinematic viscosity at 100 ° C. in the range of 4.2 to 4.4 mm ² / s was recovered to obtain a mineral oil base oil (2).
For mineral oil base oil (2), aromatic content (% C _A ) = 0.0, naphthene content (% C _N ) = 18.3, sulfur content = less than 100 ppm by mass, mass average molecular weight = 150 to 450 there were.

Example 3 (Production of mineral oil base oil (3))
In the production method of Example 2, the hydrogenated product oil was distilled under reduced pressure, and a fraction having a kinematic viscosity at 100 ° C. in the range of 2.5 to 3.0 mm ² / s was collected. In the same manner as in Example 2, mineral oil base oil (3) was obtained.
For the mineral oil base oil (3), the aromatic content (% C _A ) = 0.1, the naphthene content (% C _N ) = 20.2, the sulfur content = less than 100 mass ppm, and the mass average molecular weight = 150 to 450 there were.

Comparative Example 1 (Production of mineral oil base oil (a))
A heavy fuel oil obtained from a vacuum distillation apparatus in a normal fuel oil production process was subjected to solvent extraction under a solvent ratio of 1.0 to 2.0 using a furfural solvent to obtain a raffinate.
The raffinate was hydroisomerized and dewaxed using a hydroisomerization dewaxing catalyst under the conditions of a hydrogen partial pressure of 4 MPa, a reaction temperature of 260 to 280 ° C., and LHSV of 1.0 hr ⁻¹ .
Next, the hydroisomerized and dewaxed product oil was hydrotreated using a nickel tungsten catalyst under conditions of a hydrogen partial pressure of 4 to 5 MPa, a reaction temperature of 280 to 320 ° C., and LHSV of 1.0 hr ⁻¹ . .
The hydrogenated product oil was distilled under reduced pressure, and a fraction having a kinematic viscosity at 100 ° C. in the range of 4.0 to 4.5 mm ² / s was recovered to obtain a mineral oil base oil (a).
Regarding the mineral oil base oil (a), the aromatic content (% C _A ) = 2.8, the naphthene content (% C _N ) = 27.3, the sulfur content = 1000 mass ppm, and the mass average molecular weight = 150 to 450. It was.

Comparative Example 2 (Production of mineral oil-based base oil (b))
In the production method of Comparative Example 1, the hydrotreated oil was distilled under reduced pressure, and a fraction having a kinematic viscosity at 100 ° C. in the range of 2.0 to 3.0 mm ² / s was collected. A mineral oil base oil (b) was obtained in the same manner as in Example 1.
Regarding the mineral oil base oil (b), the aromatic content (% C _A ) = 4.7, the naphthene content (% C _N ) = 28.7, the sulfur content = 2000 mass ppm, and the mass average molecular weight = 150 to 450. It was.

Comparative Example 3 (Production of mineral oil base oil (c))
A mixture of 20 parts by mass of slack wax obtained in Production Example 2 and 80 parts by mass of bottom oil obtained in Production Example 1 was used as the raw material oil (iv). The raw material oil (iv) has an oil content of 62.5 mass%, a sulfur content of 68 mass ppm, a nitrogen content of 2 mass ppm, a kinematic viscosity at 100 ° C. of 4.1 mm ² / s, and a viscosity index. 141.
And in the manufacturing method of Example 2, it replaces with raw material oil (ii) as raw material oil, the above-mentioned raw material oil (iv) is used, the hydrogenated product oil is distilled under reduced pressure, and the operation | movement in 100 degreeC is carried out. A mineral base oil (c) was obtained in the same manner as in Example 2, except that the fraction having a viscosity in the range of 6.0 to 7.0 mm ² / s was collected.
Regarding the mineral oil base oil (c), the aromatic content (% C _A ) = 0.0, the naphthene content (% C _N ) = 21.4, the sulfur content = less than 100 ppm by mass, and the mass average molecular weight = over 450. It was.

Table 1 shows various properties of the mineral base oils produced in the examples and comparative examples. Moreover, about the mineral oil base oil (2) of Example 2, the mineral oil base oil (a) of the comparative example 1, and the mineral oil base oil (b) of the comparative example 2, the relationship between temperature and complex viscosity (eta) * is shown. The graph shown is shown in FIG.

Examples 4-7, Comparative Examples 4-8
Using the mineral oil base oils (1) to (3) and (a) to (c) produced in the examples and comparative examples of the types shown in Table 2, the types and blending amounts shown in Table 2 are used. Lubricating oil compositions (i) to (iv) and (A) to (E) were prepared by blending oil additives.

The details of the lubricant additive in Table 2 are as follows.
-Viscosity index improver: Olefin copolymer having Mw of 500,000.
Metal-based detergent (1): overbased calcium salicylate, base number (perchloric acid method) = 225 mg KOH / g, calcium atom content 7.8% by mass.
Antiwear agent (1): secondary alkyl type zinc dialkyldithiophosphate, zinc content = 9.0 mass%, phosphorus atom content = 8.2 mass%.
Antioxidant (1): An amine antioxidant.
-Antioxidant (2): Phenolic antioxidant.
Dispersant (1): polybutenyl succinic acid bisimide, Mn of polybutenyl group = 2000, base number (perchloric acid method) = 11.9 mgKOH / g, nitrogen atom content = 0.99 mass%.
Dispersant (2): polybutenyl succinic acid monoimide borate, Mn of polybutenyl group = 1000, base number (perchloric acid method) = 25 mgKOH / g, nitrogen atom content = 1.23 mass%, boron atom Content = 1.3% by mass.
-Rust preventive, antifoaming agent, pour point depressant: polymethacrylate with Mw of 69,000.

  And about the prepared lubricating oil composition (i)-(iv) and (A)-(E), various properties were measured according to the above-mentioned measuring method. In addition, based on the method shown below, a panel coking test is conducted to measure the deposit amount. For lubricating oil compositions (iv), (D) and (E) containing pour point depressants, the deposit amount is increased. The rate P was also calculated. The results are shown in Table 2.

[Panel coking test]
(1) Measurement of deposit amount 300 mL of the prepared lubricating oil composition was placed in a heating tank and heated to 100 ° C. Then, the operation of splashing the lubricating oil composition heated to 100 ° C. with the wings continuously rotated at a speed of 1000 rpm on the aluminum plate heated to 300 ° C. installed in the upper part of the heating tank is 1 The cycle lasted for 3 hours as "rotating the wings for 15 seconds and then stopping for 45 seconds". The mass (deposit amount) of the deposit adhered to the aluminum plate after 3 hours was measured.
(2) Calculation of deposit rate increase rate P Based on the deposit amount calculated in (1) above, with respect to the deposit amount (W ₀ ) of the lubricating oil composition (I) of Example 4 not containing the pour point depressant, The increasing rate P of the deposit amount (W) of the lubricating oil composition (iv) of Example 7 containing the pour point depressant was calculated based on the following calculation formula (f2).
Formula (f2): P (unit:%) = (W−W ₀ ) / W ₀ × 100
Similarly, the lubricating oil composition (D) of Comparative Example 7 containing the pour point depressant with respect to the deposit amount (W ₀ ) of the lubricating oil composition (A) of Comparative Example 4 not containing the pour point depressant. Lubricating oil composition of Comparative Example 8 containing a pour point depressant with respect to the rate of increase P of the deposit amount (W) and the deposit amount (W ₀ ) of the lubricating oil composition of Comparative Example 5 containing no pour point depressant. The increase rate P of the deposit amount (W) of (E) was also calculated from the above calculation formula (f2).

The lubricating oil compositions (i) to (iv) of Examples 4 to 7 using the mineral base oils (1) to (3) obtained in Examples 1 to 3 have good low-temperature viscosity characteristics, Moreover, the deposit amount by the panel caulking test was also low, and the result was excellent in the high temperature cleanliness of the piston.
On the other hand, the lubricating oil compositions (A), (C), and (D) of Comparative Examples 4, 6, and 7 using the mineral base oils (a) and (c) obtained in Comparative Examples 1 and 3 were: The low temperature viscosity characteristic was inferior. Further, the lubricating oil compositions (A) to (E) of Comparative Examples 4 to 8 using the mineral base oils (a) to (c) obtained in Comparative Examples 1 to 3 have a high deposit amount, and the piston There is a problem with high temperature cleanliness.
In addition, when the value of the increase rate P of the deposit amount of the lubricating oil composition (iv) of Example 7 and the lubricating oil compositions (D) and (E) of Comparative Examples 7 and 8 is compared, the mineral oil of the present invention By using the base oil, it can be seen that even when a pour point depressant is contained, the deposit generation suppressing effect is high.

1: Sliding mechanism 2: Block 2a: Piston motion path 2b: Crankshaft housing part 4: Piston 6, 8: Piston ring 9: Connecting rod 10: Crankshaft 12: Liner 20: Lubricating oil composition

Claims (17)

A mineral base oil that satisfies the following requirements (I) to (V).
· Requirement (I): kinematic viscosity at 100 ° C. is less than ^{2 mm} 2 / s or more ^{7 mm} 2 / s.
Requirement (II): Viscosity index is 100 or more.
Requirement (III): Complex viscosity between two points of −10 ° C. and −25 ° C. measured under the conditions of an angular velocity of 6.3 rad / s and a strain of 0.1 to 100% using a rotary rheometer. The temperature gradient Δ | η * | is 60 Pa · s / ° C. or less.
Requirement (IV): The content ratio [R1 / R2] of the monocyclic cycloparaffin content (R1) and the 2-6 cyclic cycloparaffin content (R2) measured in accordance with ASTM D 2786 is a volume ratio. And 0.70 or less.
- Requirements (V):% _{C A} is less than 1.0.   Total content of 1-ring cycloparaffins (R1) and 2-6-rings cycloparaffins (R2) with respect to 100% by volume of the total amount of paraffins in the mineral oil base oil measured according to ASTM D 2786 The mineral base oil according to claim 1, wherein the amount is 20% by volume or more.   The content of 2 to 6 cycloparaffins (R2) is 15 to 70% by volume relative to 100% by volume of the total amount of paraffins in the mineral oil base oil, measured according to ASTM D 2786. The mineral oil-based base oil according to claim 1 or 2.   The complex viscosity η * at −35 ° C. measured at a angular velocity of 6.3 rad / s and a strain amount of 0.1% using a rotary rheometer is 60,000 Pa · s or less. 4. The mineral oil base oil according to any one of 3 above. The mineral base oil according to any one of claims 1 to 4, wherein the naphthene content (% C _N ) is 15 to 30.   The mineral oil base oil according to any one of claims 1 to 5, wherein the viscosity index is 145 or less.   The mineral oil-based base oil according to any one of claims 1 to 6, wherein the sulfur content is less than 100 ppm by mass.   The mineral oil-based base oil according to any one of claims 1 to 7, having a mass average molecular weight of 450 or less.   The mineral oil base oil according to any one of claims 1 to 8, which is obtained by refining a raw material oil containing a petroleum-derived wax.   The mineral oil-based base oil according to any one of claims 1 to 9, which is obtained by refining raw material oil containing petroleum-derived wax and bottom oil.   The mineral oil base oil according to claim 10, wherein a content ratio [wax / bottom oil] between the petroleum-derived wax and the bottom oil is 30/70 to 95/5 in terms of mass ratio.   The lubricating oil composition containing the mineral oil base oil of any one of Claims 1-11.   The lubricating oil composition according to claim 12, wherein the content of the lubricating oil additive comprising a polymer component is 10% by mass or less based on the total amount of the lubricating oil composition. The lubricating oil composition according to claim 12 or 13, wherein the kinematic viscosity at 100 ° C is 4 mm ² / s or more and less than 15 mm ² / s, and the viscosity index is 140 or more. The dynamic viscosity at 100 ° C. is less than 12.5 mm ² / s, and the high-temperature high shear viscosity (HTHS viscosity) at 150 ° C. is less than 3.5 mPa · s. The lubricating oil composition described.   An internal combustion engine having a sliding mechanism including a piston ring and a liner and including the lubricating oil composition according to any one of claims 12 to 15.   A method for lubricating an internal combustion engine having a sliding mechanism including a piston ring and a liner, wherein the piston ring and the liner are lubricated using the lubricating oil composition according to any one of claims 12 to 15. A method for lubricating an internal combustion engine.