JP2018062632A - Base oil for lubricant and lubricant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base oil for a lubricant and a lubricant having viscosity suppressed to increase, having an excellent evaporation resistance in high temperature environment and having a fluidity available in a wide temperature range from low to high.SOLUTION: A base oil for a lubricant comprising a specific ester compound having an ester linkage can suppress an elevation of viscosity thereof while maintaining evaporation resistance and satisfy a low pour point.SELECTED DRAWING: None

Description

  The present invention relates to a lubricating base oil and lubricating oil.

  In recent years, from the viewpoint of environmental problems, factories, transportation companies, and the like are required to reduce power consumption and fuel consumption more than ever. Therefore, power saving and fuel saving effects are also demanded as effects caused by lubricating oil used in various industrial machines, automobiles and the like. Means for enhancing the power saving and fuel saving effects of various industrial machines, automobiles, etc. include a method of reducing friction by adding a friction modifier to the lubricating oil, and using a low viscosity base oil. Further, various machines used in a low temperature environment such as a cold region in winter are desired to have good startability (hereinafter also referred to as “low temperature startability”) in a low temperature environment. It is effective to use a low-viscosity base oil as a means for improving the low-temperature startability.

  In recent years, the use of lubricating oil in a high temperature environment has been increasing with the improvement in performance and reduction in size and weight of various machines. When lubricating oil is used in a high temperature environment, the base oil in the lubricating oil tends to evaporate. Therefore, an improvement in characteristics for suppressing the evaporation of the base oil (hereinafter also referred to as “low evaporation”) is required.

  For example, as a lubricating oil or a lubricating oil base oil having a low viscosity and a low evaporation property, a lubricating oil containing an aliphatic monocarboxylic acid ester and a lubricating oil base oil containing a succinic diester are disclosed, respectively ( For example, see Patent Documents 1 and 2). Further, as a technique for imparting good temperature characteristics and life while maintaining the viscosity of the lubricating oil composition, a lubricating base oil containing a specific ether bond-containing ester compound is disclosed (for example, Patent Document 3). reference). Further, as a bearing lubricant that can be used in a wide temperature range, an ester compound comprising 2-ethyl-2-methyl-1,3-propanediol and a carboxylic acid having 5 to 12 carbon atoms, A bearing lubricant containing a base oil is disclosed (for example, see Patent Document 4).

JP 2002-146374 A JP 2003-34795 A Japanese Patent Laid-Open No. 2006-74816 JP 2010-138316 A

  In recent years, there has been a tendency to improve the performance and size of various machines, and with the power saving and fuel saving effects, there is a need for a base oil that is further excellent in viscosity characteristics and excellent in low evaporation. ing. By the way, generally, when trying to improve the low evaporation property of the base oil, the kinematic viscosity tends to increase. On the other hand, in order to improve the base oil in order to obtain power saving, fuel saving effect or low temperature startability, the kinematic viscosity of the base oil tends to be lowered. That is, there is a need for a base oil that is used for a lubricating oil that is low evaporative, has a low viscosity, and can be used for a long period of time in a wide temperature range from low temperature to high temperature.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have suppressed the increase in viscosity while maintaining a low evaporation property of the base oil for lubricating oil by the specific ester compound having an ether bond, and It has been found that a low pour point can be realized.

  The present invention has been made in view of the above, and has a fluidity that suppresses the increase in viscosity, is excellent in low evaporation under a high temperature environment, and has fluidity that can be used in a wide temperature range from low temperature to high temperature. Providing oil base oils and lubricating oils.

<1> A lubricating oil which is at least one compound selected from the group consisting of a compound represented by the following general formula (1), a compound represented by the general formula (2), a compound (3) and a compound (4) Base oil for use.

  In general formula (1), n represents the integer of 5-11.

  In general formula (2), n represents the integer of 5-11.

<2> A lubricating oil containing the lubricating base oil according to <1>.

<3> Furthermore, it contains at least one antioxidant selected from the group consisting of a diphenylamine compound, an alkylated phenyl-α-naphthylamine, a hindered phenol compound, and a phosphite, and the content of the antioxidant is lubricating. Lubricating oil as described in <2> which is 0.05 mass%-2 mass% with respect to the total mass of oil.

  According to the present invention, there is provided a base oil for lubricating oil and a lubricating oil that are prevented from increasing in viscosity, are excellent in low evaporation under a high temperature environment, and have fluidity that can be used in a wide temperature range from low temperature to high temperature. Can be provided.

Hereinafter, embodiments for carrying out the present invention will be described in detail.
In addition, in this specification, "-" showing a numerical range represents the range containing the numerical value each described as the upper limit and the minimum. In addition, when only the upper limit value is described in the numerical range represented by “to”, it means that the lower limit value is also the same unit.

<Base oil for lubricating oil>
The base oil for lubricating oil of the present invention is at least one selected from the group consisting of a compound represented by the following general formula (1), a compound represented by the general formula (2), a compound (3) and a compound (4). It is a kind of compound (hereinafter also referred to as a specific ester compound). The specific ester compound is an ester compound having at least one ether bond in one molecule. The total carbon number of the specific ester compound is in the range of 25-37. When the base oil for lubricating oil is a specific ester compound, even when the lubricating oil is used in a high temperature environment, the increase in viscosity is suppressed, and the low evaporation property in the high temperature environment is excellent and good. It is possible to maintain a good fluidity.

Generally, in order to improve evaporability, it is required to increase the molecular weight of the ester compound and reduce the number of branched chains in one molecule. However, when the molecular weight is increased and the number of branched chains is decreased, the ester compound is likely to be crystallized, and good fluidity in a low temperature environment may not be maintained.
Since the specific ester compound contains an oxygen atom derived from an ester bond and an ether bond, repulsion between oxygen atoms is likely to occur, and there is a tendency that crystallization is difficult. Since the base oil for lubricating oil of the present invention is a specific ester compound, it is presumed that it is difficult to solidify even in a low temperature environment and can maintain good fluidity.

  In the present embodiment, the high temperature environment refers to an environment of 60 ° C. or higher. Moreover, low evaporation means that when the lubricating oil is used in a high temperature environment, the mass change rate of the lubricating oil before and after use is 0.35% or less.

  In general formula (1), n represents the integer of 5-11.

  In general formula (2), n represents the integer of 5-11.

  In this specification, the manufacturing method of a specific ester compound does not have a restriction | limiting in particular, The well-known method conventionally used generally can be used. The specific ester compound may be, for example, a reaction product obtained by an esterification reaction between a monovalent alcohol and a divalent carboxylic acid or an esterification reaction between a divalent alcohol and a monovalent carboxylic acid.

Moreover, the specific ester compound has at least one side chain in one molecule.
Here, the side chain in the specific ester compound means a branch portion branched from the main chain. The main chain means a chain having the largest number of carbon atoms constituting the specific ester compound. The number of carbon atoms in the side chain is not particularly limited, and the number of carbon atoms may be 1. A specific example of the side chain having 1 carbon atom is a methyl group.

  In the general formulas (1) and (2), n is an integer of 5 to 11, and n is from 5 to 9 from the viewpoint of suppressing the increase in viscosity, low evaporating property in a high temperature environment, and low pour point. An integer is preferable, 6 to 8 is more preferable, and 7 is still more preferable.

  Specific examples of the general formula (1) or the general formula (2) include the following exemplary compound (1-1) and exemplary compound (2-1).

<Lubricating oil>
The lubricating oil of the present invention contains a base oil for lubricating oil that is a specific ester compound. The lubricating oil of the present invention preferably contains an antioxidant.

  The content of the base oil for lubricating oil is preferably 90% by mass or more, more preferably 93% by mass or more, and further preferably 95% by mass or more, based on the total mass of the lubricating oil. preferable.

(Antioxidant)
The lubricating oil preferably contains the lubricating base oil and at least one antioxidant selected from the group consisting of a diphenylamine compound, an alkylated phenyl-α-naphthylamine, a hindered phenol compound, and a phosphite.

  As a diphenylamine compound, the compound represented by following General formula (5) is mentioned, for example.

In General Formula (5), R ₄ and R ₅ each independently represent a hydrogen atom or a linear or branched alkyl group having 1 to 16 carbon atoms.

R ₄ and R ₅ are each independently preferably a hydrogen atom or a linear or branched alkyl group having 3 to 9 carbon atoms, more preferably a hydrogen atom or a linear or branched chain having 4 to 8 carbon atoms. It is an alkyl group.

Specific examples of the linear or branched alkyl group represented by R ₄ and R ₅ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-pentyl group, 2-methylbutyl group, n-hexyl group, isohexyl group, 3-methylpentyl group, ethylbutyl group, n-heptyl group, 2-methylhexyl group, n-octyl group, 2-ethylhexyl group, 3-methylheptyl group, n -Nonyl group, methyl octyl group, ethyl heptyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tetradecyl group, etc. are mentioned.

  A diphenylamine compound may be used alone or in combination of two or more.

  Examples of the alkylated-α-naphthylamine include compounds represented by the following general formula (6).

In General Formula (6), R ₆ is a linear or branched alkyl group having 1 to 16 carbon atoms.
R ₆ in the general formula (6) is preferably a linear or branched alkyl group having 4 to 8 carbon atoms.

Specific examples of the linear or branched alkyl group represented by R ₆ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, and an n-pentyl group. , Isopentyl group, neopentyl group, tert-pentyl group, 2-methylbutyl group, n-hexyl group, isohexyl group, 3-methylpentyl group, ethylbutyl group, n-heptyl group, 2-methylhexyl group, n-octyl group, Examples include 2-ethylhexyl group, 3-methylheptyl group, n-nonyl group, methyloctyl group, ethylheptyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tetradecyl group and the like.
Alkylated-α-naphthylamine may be used alone or in combination of two or more.

  Examples of the hindered phenol compounds include compounds represented by the following general formula (7), general formula (8), or general formula (9).

In General Formula (7), R ₇ , R ₈ , R ₁₀ , and R ₁₁ each independently represent a hydrogen atom or a linear or branched alkyl group having 1 to 12 carbon atoms. R ₉ represents an alkylene group having 1 to 5 carbon atoms.

In General Formula (7), R ₇ , R ₈ , R ₁₀ , and R ₁₁ are each independently preferably a hydrogen atom or a linear or branched alkyl group having 4 to 8 carbon atoms.

Specific examples of the linear or branched alkyl group represented by R ₇ , R ₈ , R ₁₀ , and R ₁₁ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and isobutyl. Group, tert-butyl group, n-pentyl group, isopentyl group, neopentyl group, tert-pentyl group, 2-methylbutyl group, n-hexyl group, isohexyl group, 3-methylpentyl group, ethylbutyl group, n-heptyl group, 2-methylhexyl group, n-octyl group, 2-ethylhexyl group, 3-methylheptyl group, n-nonyl group, methyloctyl group, ethylheptyl group, n-decyl group, n-undecyl group, n-dodecyl group, etc. Is mentioned.

In the general formula (7), _{R 9} is an alkylene group having 1 to 5 carbon atoms, preferably an alkylene group having 1 to 4 carbon atoms.

Specific examples of the alkylene group represented by R ₉ include a methylene group, an ethylene group, a propylene group, a butylene group, and a pentylene group.

In the general formula _{(8), R 12} and _{R 13} each independently represents a linear or branched alkyl group having a hydrogen atom or 1 to 12 carbon atoms. n represents an integer of 1 to 4.

In the general formula (8), R ₁₂ and R ₁₃ are each independently preferably a hydrogen atom or a linear or branched alkyl group having 4 to 8 carbon atoms.

  In general formula (8), n is an integer of 1-4, Preferably it is an integer of 1-3.

Specific examples of the linear or branched alkyl group represented by R ₁₂ and R ₁₃ include the same alkyl groups as R ₇ , R ₈ , R ₁₀ , and R ₁₁ in the general formula (7). It is done.

In general formula (9), R <_14> , R <_15> and R < ₁₆ > represent a hydrogen atom or a C1-C12 linear or branched alkyl group each independently.

In the general formula (9), R ₁₄ and R ₁₅ are each independently preferably a hydrogen atom or a linear or branched alkyl group having 4 to 8 carbon atoms, and R ₁₆ is preferably a hydrogen atom or carbon. It is a linear or branched alkyl group of formulas 1-4.

Specific examples of the linear or branched alkyl group represented by R ₁₄ , R ₁₅ and R ₁₆ are the same as the alkyl groups in R ₇ , R ₈ , R ₁₀ and R ₁₁ in the general formula (7). Is mentioned.

  A hindered phenol compound may be used alone or in combination of two or more.

  Examples of the phosphite include a compound represented by the following general formula (10).

In General Formula (10), R ₁₇ and R ₁₈ each independently represent a linear or branched alkyl group having 1 to 20 carbon atoms.

In the general formula (10), R ₁₇ and R ₁₈ are each independently preferably a linear or branched alkyl group having 2 to 6 carbon atoms.

Specific examples of the linear or branched alkyl group represented by R ₁₇ and R ₁₈ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, n-pentyl group, isopentyl group, neopentyl group, tert-pentyl group, 2-methylbutyl group, n-hexyl group, isohexyl group, 3-methylpentyl group, ethylbutyl group, n-heptyl group, 2-methylhexyl group, n -Octyl group, 2-ethylhexyl group, 3-methylheptyl group, n-nonyl group, methyloctyl group, ethylheptyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tetradecyl group, etc. Can be mentioned.

  Phosphite may be used alone or in combination of two or more.

The content of the antioxidant is preferably 0.05% by mass to 2% by mass with respect to the total mass of the lubricating oil. When the content of the antioxidant is 0.05% by mass or more, the evaporability of the lubricating oil at a high temperature tends to be further suppressed.
From the above viewpoint, the content of the antioxidant is more preferably 0.25% by mass to 1.5% by mass, and further preferably 0.5% by mass to 1% by mass.
Antioxidants may be used singly or in combination of two or more. As for the content when two or more types are used in combination, the total amount is preferably within the above range.

<Other base oils>
The lubricating oil may further contain other base oils other than the specific ester compound as long as the objects and effects of the present invention are not impaired. Examples of other base oils include mineral base oils and synthetic base oils.
As base oils for mineral-based lubricating oils, hydrorefined oils, catalytic isomerized oils, etc. are highly refined paraffinic mineral oils and lubricating base oil raw materials that have been treated by solvent dewaxing or hydrodewaxing. Raffinate obtained by solvent purification using aromatic extraction solvents such as phenol and furfural, hydrotreated oil obtained by hydrotreating using hydrotreating catalyst such as cobalt and molybdenum using silica-alumina as a carrier, etc. Is mentioned.

Examples of base oils for synthetic lubricants include base oils synthesized by Fischer-Tropsch reaction using gas such as methane as raw materials, poly-α-olefin oligomers, polybutenes, alkylbenzenes, monoesters, polyol esters, polyglycols. Examples include esters, polyethylene propylenes, hindered esters, dibasic acid esters and the like.
Other base oils may be used alone or in combination of two or more. In addition, as for other base oils, a base oil for mineral lubricating oil and a base oil for synthetic lubricating oil may be mixed.

  When the lubricating oil contains other base oil, the content of the other base oil is preferably 80% by mass or less, more preferably 70% by mass or less, based on the total mass of the lubricating oil. More preferably, it is 50 mass% or less.

(Other additives)
The lubricating oil of the present invention may further contain general lubricating oil additives such as metal deactivators, rust inhibitors, antiwear agents, pour point depressants, viscosity index improvers, and hydrolysis inhibitors. Good.

<Kinematic viscosity, viscosity index and pour point of lubricating oil>
Lubricating oil is preferably a kinematic viscosity at 40 ° C. is ^{6mm 2} / ^s~20mm 2 / s. When the 40 ° C. kinematic viscosity is 6 mm ² / s or more, evaporation loss is suppressed and sufficient lubrication performance can be maintained. Moreover, when it is 20 mm < ² > / s or less, it will be suppressed that the viscous torque at the time of using for a precision instrument etc. becomes large, and low temperature startability falls. Therefore, low power consumption and evaporation loss, from the viewpoint of lubricating performance, and more preferably a kinematic viscosity at 40 ° C. is ^{6mm 2} / ^s~15mm 2 / ^s, is 7.5mm ² / s~13mm 2 / s More preferably.

The lubricating oil preferably has a viscosity index of 110 or more, more preferably 120 or more. When the viscosity index is 110 or more, a change in viscosity with respect to a change in temperature is suppressed, and an increase in viscosity torque at a low temperature is suppressed.
The 40 ° C. kinematic viscosity of the lubricating oil is a value measured by a method defined in JIS-K-2283: 2000 (ASTM D445). Moreover, the viscosity index of lubricating oil is a value measured by the method prescribed | regulated to JISK2283: 2000 (ASTM D2270).

  The pour point of the lubricating oil is preferably −20 ° C. or lower, more preferably −30 ° C. or lower, and still more preferably −35 ° C. or lower. When the pour point is −20 ° C. or lower, a predetermined low-temperature torque performance tends to be easily obtained. Here, the pour point is a value measured based on the JIS K 2269: 1987 pour point test method.

<Use of lubricating oil>
The lubricating oil of the present invention can be suitably used as a lubricating oil for bearings of motors such as various precision instruments, CD-Rs, DVD-Rs, HDDs, and watches.
In particular, by using it for the sliding part and the rotating part of the precision device described above, it is possible to achieve excellent lubricity stably for a long period of time by suppressing evaporation loss while ensuring low power consumption.

  Hereinafter, the contents of the present invention will be specifically described based on examples, but the present invention is not limited to these examples.

(Examples 1-4 and Comparative Examples 1 and 2)
The lubricating oils of Examples 1 to 4 and Comparative Examples 1 and 2 were prepared by blending each component at the ratio (mass%) shown in Table 1 below.
Each of the prepared lubricating oils was evaluated as follows. The evaluation results are shown in Table 1.

[Evaluation]
(1) Measurement of kinematic viscosity Based on the kinematic viscosity test method prescribed | regulated to JISK2283: 2000, kinematic viscosity (mm < ² > / s) was measured at 40 degreeC. The measurement results are shown in Table 1. If the 40 ° C. kinematic viscosity is 20 mm ² / s or less, it can be evaluated that the viscosity is low.

(2) Calculation of viscosity index The viscosity index was measured based on the method defined in JIS K 2283: 2000 (ASTM D2270). The measurement results are shown in Table 1. It can be evaluated that the viscosity temperature characteristic is secured when the viscosity index is 110 or more.

(3) Measurement of Evaporation Rate Each lubricating oil prepared above was stored in a constant temperature bath at 120 ° C. for 2,000 hours. The rate of change in the mass of the lubricating oil before and after storage was determined to evaluate the low evaporation. The evaluation results are shown in Table 1.
Rate of change (mass%) = (mass of lubricant before storage−mass of lubricant after storage) / mass of lubricant before storage × 100

(4) Measurement of pour point The pour point of each lubricating oil prepared above was measured based on the pour point test method defined in JIS K 2269: 1987. The results are shown in Table 1. If the pour point is −20 ° C. or lower, it can be evaluated that low temperature viscosity and lubricating properties are obtained.

  Each component in Table 1 is as follows. In Table 1, “-” means that the component is not included.

(Base oil)
Base oil A; the following exemplary compound (1-1) (compound represented by the general formula (1))

  Base oil B: Exemplified compound (2-1) shown below (compound represented by formula (2))

  Base oil C; compound (3)

  Base oil D; compound (4)

  Base oil E: The following exemplary compound (A)

Base oil F; DOS, di-2-ethylhexyl sebacate (C ₈ H ₁₆ (COOC ₈ H ₁₇ ) ₂ )

(Antioxidant)
Antioxidant A; alkylated phenyl-α-naphthylamine (N-phenyl-ar- (1,1,3,3-tetramethylbutyl) -1-naphthaleneamine)
Note that ar is an abbreviation for “aryl group”.
Antioxidant B: Phosphite (Tris (2,4-di-tert-butylphenyl) phosphite)
Antioxidant C: alkylated diphenylamine (reaction product of N-phenylbenzeneamine and 2,4,4-trimethylpentene)

(Other lubricant additives)
Metal deactivator; benzotriazole derivative rust inhibitor; succinic acid half ester antiwear agent; tetraoleic acid polyoxyethylene sorbite hydrolysis inhibitor; carbodiimide compound antistatic agent; lithium bis (trifluoromethanesulfonyl) imide

  As shown in Table 1, in the lubricating oils of Examples 1 to 4, the evaporation rate is suppressed and the low evaporation property is good as compared with Comparative Example 2 containing DOS. Moreover, it turns out that the lubricating oil of Examples 1-4 is a very low pour point compared with the lubricating oil of the comparative example 1 using the base oil containing the compound which does not have an ether group. Therefore, it can be seen that the lubricating oil of the present invention can be used in a wide temperature range from a low temperature to a high temperature as compared with Comparative Example 1.

Claims (3)

Base oil for lubricating oil, which is at least one compound selected from the group consisting of a compound represented by the following general formula (1), a compound represented by the general formula (2), a compound (3) and a compound (4) .

[In General Formula (1), n represents the integer of 5-11. ]

[In general formula (2), n represents the integer of 5-11. ]

  A lubricating oil comprising the lubricating base oil according to claim 1.   Further, it contains at least one antioxidant selected from the group consisting of a diphenylamine compound, an alkylated phenyl-α-naphthylamine, a hindered phenol compound, and a phosphite, and the content of the antioxidant is the total amount of the lubricating oil. The lubricating oil according to claim 2, which is 0.05% by mass to 2% by mass with respect to the mass.