JP2014237854A - Lubricant composition for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide lubricant composition for internal combustion engine which is capable of sufficiently suppressing generation of liner lacquer, by which an oil (lubricant for internal combustion engine) consumption amount can be reduced.SOLUTION: There is provided lubricant composition for internal combustion engine containing lubricant base oil containing mineral oil and/or synthetic oil and metal-based cleaning agent (A). Nq coefficient shown in formula (1) of the lubricant composition is 0.004 or more, kinematic viscosity at 100°C is 9.3 mm/s or more and 21.9 mm/s or less, base number is 5 mgKOH/g or more and 80 mgKOH/g or less, and solubility of 1,4-naphthoquinone with respect to 100 g of the lubricant composition is 1.3 g or more. Nq coefficient=ΣNq(P)+ΣNq(N) (1)

Description

  The present invention relates to a lubricating oil composition for an internal combustion engine, and more particularly to a lubricating oil composition for an internal combustion engine that can reduce the formation of lacquer on a cylinder liner.

  From 1980 to 1985, in the European region, lacquer is generated on the cylinder liner and the surface of the cylinder liner is mirror-finished in marine medium and high speed 4 cycle diesel engines using low sulfur fuel. There has been a problem of sudden increase in consumption. Since then, the causes and countermeasures have been studied, but the problem has not been solved yet. In addition, as one of the measures to increase the output and efficiency of diesel engines, the introduction of common rail technology and controlling combustion by fuel multi-stage injection has also been studied. Problems have been reported to occur.

  Liner lacquer has been reported to be caused by unburned fuel degradants and excess metal additives. As a lubricating oil intended to prevent the formation of liner lacquer, a lubricating oil for internal combustion engines having a low base number (9 mgKOH / g) using a magnesium-based detergent is disclosed (Non-patent Document 1). Further, it has been reported that the main component of liner lacquer is quinones produced by partial oxidation of a heavy condensed ring aromatic component in fuel (Non-patent Document 2).

Satoshi Hanashima; Proceedings of the 38th Special Fund Lecture Meeting of the Marine Engineers Society, Hei 7-2, 40-51 J. et al. Barnes et. al. CIMAC Congress 2004 Kyoto (2004), Paper No .; 22

However, the lubricating oil for internal combustion engines of Non-Patent Document 1 is not sufficiently effective in suppressing the formation of liner lacquer, and there are concerns about the deterioration of cleanliness and water resistance.
Then, this invention makes it a subject to provide the lubricating oil composition for internal combustion engines which can fully suppress the production | generation of liner lacquer and can reduce oil (lubricating oil for internal combustion engines) consumption by this.

The present invention is a lubricating oil composition comprising a lubricating base oil composed of mineral oil and / or synthetic oil and (A) a metallic detergent, wherein the lubricating oil composition is represented by the following formula (1): shown Nq coefficient equal to or greater than 0.004, kinematic viscosity at 100 ℃ is 9.3 mm ² / s or more 21.9 mm ² / s or less, and the base value is not more than 5 mgKOH / g or higher 80 mg KOH / g, the lubricating oil composition The lubricating oil composition for an internal combustion engine has a solubility of 1,4-naphthoquinone per 100 g of 1.3 g / or more.
Nq coefficient = ΣNq (P) + ΣNq (N) (1)
In the formula (1), ΣNq (P) represents “(mass% of metal derived from alkaline earth metal phenate in lubricating oil composition) / (metal ratio of alkaline earth metal phenate) / 2A”, and ΣNq (N) Represents “(mass% of nitrogen derived from the ashless dispersant in the lubricating oil composition) /14.01”. A represents the atomic weight of the alkaline earth metal.

  In the present invention, (A) the metal-based detergent is preferably calcium phenate and / or calcium salicylate.

  The lubricating oil composition for an internal combustion engine of the present invention preferably further contains 2% by mass or more of (B) polybutenyl succinimide based on the total amount of the lubricating oil composition.

  The lubricating oil composition for an internal combustion engine of the present invention is suitably used for a direct injection diesel engine having an average effective pressure of 1.5 MPa or more.

  The lubricating oil composition for an internal combustion engine of the present invention is suitably used for a diesel engine having a common rail fuel injection format and injecting fuel in multiple stages.

  INDUSTRIAL APPLICABILITY The lubricating oil composition for an internal combustion engine of the present invention can suppress the formation of lacquer on the cylinder liner, and reduce the consumption of engine oil (lubricating oil composition for an internal combustion engine) resulting from the lacquer formation. Can do. The lubricating oil composition for internal combustion engines of the present invention is suitable as a lubricating oil for marine medium and high speed four-cycle diesel engines and a cylinder oil for marine low-speed two-cycle diesel engines using low-sulfur fuel, and is particularly effective for average. It is suitable for direct injection diesel engines with a pressure of 1.5 MPa or more, and for diesel engines that have a common rail type fuel injection type and that inject fuel in multiple stages. By using these internal combustion engines, oil consumption can be reduced. It can be effectively reduced. Moreover, the lubricating oil composition of the present invention can also be suitably used as various diesel engine oils other than marine diesel engine lubricating oils and cogeneration diesel engine oils.

Hereinafter, the present invention will be described in detail.
(Lubricant base oil)
The lubricating base oil in the lubricating oil composition for internal combustion engines of the present invention (hereinafter simply referred to as the composition of the present invention) is not particularly limited, and mineral oil and / or synthetic oil used for ordinary lubricating oil is used. it can.
As mineral oil, lube oil fraction obtained by distillation under reduced pressure of atmospheric residue obtained by atmospheric distillation of crude oil, solvent removal, solvent extraction, hydrocracking, solvent dewaxing, hydrorefining, etc. Examples of the lubricating base oil produced by the method of isomerizing GTL WAX (gas-tuly liquid wax) produced by one or more of the above-mentioned treatments or wax isomerized mineral oil, Fischer-Tropsch process, etc. .

  The total aromatic content of the mineral oil is not particularly limited, but is preferably 40% by mass or less, and more preferably 30% by mass or less. The total aromatic content may be 0% by mass, but is preferably 1% by mass or more, more preferably 5% by mass or more, further preferably 10% by mass or more, and particularly preferably 20% by mass or more in terms of the solubility of the additive. . When the total aromatic content of the base oil exceeds 40% by mass, the oxidation stability may be inferior.

  In addition, the said total aromatic content means the aromatic fraction (aromatic fraction) content measured based on ASTMD2549. Usually, this aromatic fraction includes alkylbenzene, alkylnaphthalene, anthracene, phenanthrene, alkylated products thereof, compounds in which four or more benzene rings are condensed, and heterogeneous compounds such as pyridines, quinolines, phenols, and naphthols. Compounds having aromatics are included.

  Although there is no restriction | limiting in particular in the sulfur content in mineral oil, 1 mass% or less is preferable and 0.5 mass% or less is more preferable. Although 0 mass% may be sufficient as a sulfur content, 0.1 mass% or more is preferable and 0.2 mass% or more is more preferable. By including a certain amount of sulfur in the mineral oil, the solubility of the additive can be sufficiently increased.

  Synthetic oils include, for example, polybutene or hydrides thereof; poly-α-olefins (PAO) such as 1-octene oligomers and 1-decene oligomers or hydrides thereof; ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl Diesters such as adipate, ditridecyl adipate, di-2-ethylhexyl sebacate; polyol esters such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate; maleic acid Examples include copolymers of dicarboxylic acids such as dibutyl and α-olefins having 2 to 30 carbon atoms; aromatic synthetic oils such as alkylnaphthalene, alkylbenzene, and aromatic esters, or mixtures thereof.

  In the present invention, the above-mentioned mineral oil and synthetic oil may be used alone or in combination of two or more as the lubricating base oil, or one or more mineral oils and one or more synthetic oils may be mixed. May be used.

The kinematic viscosity of the lubricating base oil is not particularly limited, the kinematic viscosity at 100 ° C., preferably ^{4 mm} 2 / s or more 40 mm ² / s or less, more preferably ^{6 mm} 2 / s or more 40 mm ² / s, 8 mm ² / s or more 35 mm ² / s or less is more preferred. When the kinematic viscosity at 100 ° C. of the lubricating base oil exceeds 40 mm ² / s, the low-temperature viscosity characteristics may be deteriorated. On the other hand, when the kinematic viscosity at 100 ° C. is less than 4 mm ² / s, the formation of an oil film at the lubrication site is insufficient, so that the lubricity is poor and the evaporation loss of the base oil may be increased. The kinematic viscosity at 100 ° C. here refers to the kinematic viscosity at 100 ° C. as defined in ASTM D-445.

The lubricating base oil in the present invention, kinematic viscosity at 100 ° C. ^{4 mm} 2 / s or more 17mm less than ² / s, and / or a kinematic viscosity at 100 ° C. 17mm ² / s or more 40 mm ² / s or less in It is preferable to contain a lubricating base oil. Examples of the lubricating base oil having a kinematic viscosity at 100 ° C. of 4 mm ² / s or more and less than 17 mm ² / s include mineral base oils such as SAE 10-40 and synthetic base oils. Its preferred kinematic viscosity (100 ° C.) the lower limit is more preferably 5.6 mm ² / s or more, even more preferably 9.3 mm ² / s or more, and the upper limit is more preferably 14 mm ² / s or less, more preferably 12 .5 mm ² / s or less. In addition, examples of the lubricating base oil having a kinematic viscosity at 100 ° C. of 17 mm ² / s to 40 mm ² / s include mineral base oils and synthetic base oils such as SAE50 and bright stock, and preferable dynamic base oils thereof. The lower limit of the viscosity (100 ° C.) is more preferably 20 mm ² / s or more, further preferably 25 mm ² / s or more, and the upper limit is more preferably 38 mm ² / s or less, still more preferably 35 mm ² / s or less.

In the present invention, a lubricant base oil having a kinematic viscosity at 100 ° C. of 4 mm ² / s or more and less than 17 mm ² / s as a main component, for example, 50% by mass or more based on the total amount of the lubricant base oil, more preferably 70% by mass. %, And if necessary, a lubricating base oil having a kinematic viscosity at 100 ° C. of 17 mm ² / s to 40 mm ² / s can be blended.

The evaporation loss amount of the lubricating base oil is preferably 20% by mass or less, more preferably 16% by mass or less, and particularly preferably 10% by mass or less in terms of NOACK evaporation. When the NOACK evaporation amount of the lubricating base oil exceeds 20% by mass, the evaporation loss in the lubricating oil composition is large, which may cause an increase in viscosity.
Here, the NOACK evaporation amount is a value obtained by measuring the evaporation amount of the lubricating oil measured in accordance with ASTM D 5800.

  The viscosity index of the lubricating base oil is not particularly limited, but the value is preferably 85 or higher, more preferably 90 or higher, and still more preferably 95 or higher so that excellent viscosity characteristics can be obtained from low temperature to high temperature. The upper limit of the viscosity index is not particularly limited, and is about 135 to 180, such as normal paraffin, slack wax, GTL wax, or isoparaffin mineral oil obtained by isomerizing these, complex ester base oil, HVI-PAO, etc. The thing of about 150-250 like a base oil can also be used. In view of the solubility and storage stability of the additive, the upper limit of the viscosity index is preferably 120 or less, and more preferably 110 or less.

(A) Metal-based detergent The lubricating oil composition of the present invention contains (A) a metal-based detergent (hereinafter sometimes referred to as component (A)) as an essential component. As the metal detergent, any compound usually used for lubricating oils can be used. For example, phenate detergent, sulfonate detergent, salicylate detergent, naphthenate detergent, etc. Two or more types can be used in combination. Among these, phenate detergents, sulfonate detergents, and salicylate detergents are preferred, and phenate detergents and salicylate detergents are more preferred.

  As the phenate detergent, an alkali metal salt, alkaline earth metal salt or (over) basic salt of alkylphenol sulfide having the structure represented by the formula (1) can be used. Examples of the alkali metal or alkaline earth metal include sodium, potassium, magnesium, barium, and calcium. Magnesium or calcium is preferable, and calcium is particularly preferable.

（式（１）中、Ｒは炭素数６〜２１を有する直鎖または分枝、飽和または不飽和のアルキル基；重合度ｍは１〜１０、Ｓは硫黄元素であり、ｘは硫黄元素数１〜３である。）

(In Formula (1), R is a linear or branched, saturated or unsaturated alkyl group having 6 to 21 carbon atoms; polymerization degree m is 1 to 10, S is a sulfur element, and x is the number of sulfur elements. 1 to 3)

  Carbon number of the alkyl group in Formula (1) is 6-21, Preferably it is C9-18, More preferably, it is C9-15. If the carbon number is shorter than 6, the solubility in the base oil may be inferior. If the carbon number is longer than 21, the production is difficult and the heat resistance may be inferior. Among the phenate-based metal detergents, those containing an alkylphenol sulfide metal salt having a polymerization degree m of 4 or more, particularly m of 4 to 5 shown in the formula (1) are preferable because of excellent heat resistance.

  Examples of the sulfonate detergent include alkali metal salts and alkaline earth metal salts of alkyl aromatic sulfonic acids obtained by sulfonating alkyl aromatic compounds having a weight average molecular weight of 1,300 to 1,500, preferably 400 to 700. Alternatively, (over) basic salts thereof can be used. Examples of the alkali metal or alkaline earth metal include sodium, potassium, magnesium, barium, and calcium. Magnesium or calcium is preferable, and calcium is particularly preferable.

  Examples of the alkyl aromatic sulfonic acid include so-called petroleum sulfonic acid and synthetic sulfonic acid. As the petroleum sulfonic acid here, generally used is a product obtained by sulfonating an alkyl aromatic compound of a lubricating oil fraction of mineral oil, or so-called mahoganic acid produced as a by-product when white oil is produced. As the synthetic sulfonic acid, for example, an alkylbenzene having a linear or branched alkyl group, which is produced as a by-product from an alkylbenzene production plant that is a raw material of a detergent or is obtained by alkylating a polyolefin with benzene, is sulfonated. Or sulfonated alkylnaphthalene such as dinonylnaphthalene is used. The sulfonating agent for sulfonating these alkyl aromatic compounds is not particularly limited, but usually fuming sulfuric acid or sulfuric anhydride is used.

  Examples of the salicylate detergent include an alkali metal having 1 hydrocarbon group having 1 to 19 carbon atoms, an alkaline earth metal salicylate or a (over) basic salt thereof, and 1 hydrocarbon group having 20 to 40 carbon atoms. Alkaline metal, alkaline earth metal salicylate or (over) basic salt thereof, alkali metal having 2 or more hydrocarbon groups having 1 to 40 carbon atoms, alkaline earth metal salicylate or (over) basic thereof Salt. These hydrocarbon groups may be the same or different. In these, it is preferable to use the alkali metal, alkaline-earth metal salicylate, or its (over) basic salt which has one C8-C19 hydrocarbon group at the point which is excellent in low-temperature fluidity | liquidity. Examples of the alkali metal or alkaline earth metal include sodium, potassium, magnesium, barium, and calcium. Magnesium and / or calcium are preferable, and calcium is particularly preferably used.

  The base number of component (A) is preferably in the range of 50 mgKOH / g to 500 mgKOH / g, more preferably in the range of 100 mgKOH / g to 450 mgKOH / g, and still more preferably in the range of 120 mgKOH / g to 400 mgKOH / g. If the base number is less than 50 mgKOH / g, corrosion wear may increase, and if it exceeds 500 mgKOH / g, there may be a problem in solubility. The base number referred to here is 7. 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.

  The metal ratio of the component (A) is not particularly limited, but the lower limit is preferably 1 or more, more preferably 2 or more, still more preferably 2.5 or more, and the upper limit is preferably 20 or less, more preferably 15 or less. More preferably, it is 10 or less. The metal ratio here is represented by the valence of the metal element in the component (A) × metal element content (mol%) / soap group content (mol%), and the metal elements are calcium and magnesium. Etc., a soap group means a sulfonic acid group, a phenol group, a salicylic acid group, and the like.

  In the present invention, the component (A) can be used alone or in combination of two or more. When used in combination, in particular, (1) overbased Ca phenate / overbased Ca sulfonate, (2) overbased Ca phenate / overbased Ca salicylate, (3) overbased Ca phenate / overbased Ca sulfonate / A combination of overbased Ca salicylate is preferable.

  In the composition of the present invention, the content ratio of the component (A) is preferably 3% by mass or more and 30% by mass or less, more preferably 6% by mass or more and 25% by mass or less, and still more preferably 8%, based on the total amount of the composition. The mass is 20% by mass or more. If the content is less than 3% by mass, the required cleanliness and acid neutralization may not be obtained, and if it exceeds 30% by mass, excessive metal components may be deposited on the piston.

(B) Ashless Dispersant The lubricating oil composition of the present invention can contain (B) an ashless dispersant (hereinafter sometimes referred to as component (B)).
As the component (B), any ashless dispersant used in lubricating oils can be used. For example, a linear or branched alkyl group or alkenyl group having 40 to 400 carbon atoms, preferably 60 to 350 carbon atoms in the molecule. And at least one nitrogen-containing compound or derivative thereof, a Mannich dispersant, or a modified product of alkenyl succinimide. In use, one kind or two or more kinds arbitrarily selected from these can be blended.

  In the case where the carbon number of the alkyl group or alkenyl group of the nitrogen-containing compound or derivative thereof is less than 40, the solubility in the lubricating oil base oil is reduced, whereas when the carbon number of the alkyl group or alkenyl group exceeds 400 The low-temperature fluidity of the lubricating oil composition may be deteriorated. The alkyl group or alkenyl group may be linear or branched, but is preferably a component derived from an olefin oligomer such as propylene, 1-butene, isobutylene, or a co-oligomer of ethylene and propylene. Examples thereof include a branched alkyl group and a branched alkenyl group.

Examples of the component (B) include one or more compounds selected from the following components (B-1) to (B-3).
(B-1) A succinimide having at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, or a derivative thereof,
(B-2) benzylamine having at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, or a derivative thereof,
(B-3) Polyamine having at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, or a derivative thereof.

  (B-1) As a component, the compound shown by Formula (2) or (3) can be illustrated.

In the formula (2), R ²⁰ represents an alkyl group or alkenyl group having 40 to 400 carbon atoms, preferably 60 to 350 carbon atoms, and particularly preferably a polybutenyl group. h represents an integer of 1 to 5, preferably 2 to 4. On the other hand, in formula (3), R ²¹ and R ²² each independently represent an alkyl group or alkenyl group having 40 to 400 carbon atoms, preferably 60 to 350 carbon atoms, and particularly preferably a polybutenyl group. I represents an integer of 0 to 4, preferably 1 to 3.

  The component (B-1) includes a so-called monotype succinimide represented by the formula (2) in which succinic anhydride is added to one end of the polyamine, and a formula (3 in which succinic anhydride is added to both ends of the polyamine. And so-called bis-type succinimides. Any of these or a mixture thereof can be used for the composition of the present invention, but bis-type succinimide is particularly preferable from the viewpoint of heat resistance.

There is no restriction | limiting in particular in the manufacturing method of the succinimide which is (B-1) component, For example, the compound which has a C40-C400 alkyl group or an alkenyl group is made to react with maleic anhydride at 100-200 degreeC. It can be obtained by reacting alkyl succinic acid or alkenyl succinic acid with a polyamine.
Specific examples of the polyamine include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine.

  (B-2) As a component, the compound represented by Formula (4) can be illustrated.

In the formula (4), R ²³ represents an alkyl group or alkenyl group having 40 to 400 carbon atoms, preferably 60 to 350, and j represents an integer of 1 to 5, preferably 2 to 4.
(B-2) The manufacturing method of the benzylamine which is a component is not particularly limited. For example, a polyolefin such as propylene oligomer, polybutene, or ethylene-α-olefin copolymer is reacted with phenol to obtain alkylphenol. It is obtained by reacting formaldehyde with a polyamine such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, or pentaethylenehexamine by a Mannich reaction.

(B-3) As a component, the compound represented by Formula (5) can be illustrated.
^{_{R 24 -NH- (CH 2 CH 2}} NH) k -H (5)
In the formula (5), R ²⁴ represents an alkyl group or alkenyl group having 40 to 400 carbon atoms, preferably 60 to 350 carbon atoms, and k represents an integer of 1 to 5, preferably 2 to 4.
(B-3) There is no restriction | limiting in particular in the manufacturing method of the polyamine which is a component, For example, after chlorinating polyolefin, such as a propylene oligomer, a polybutene, or an ethylene-alpha-olefin copolymer, this is ethylenediamine, a diethylenetriamine, a triethylene. It can be obtained by reacting a polyamine such as tetramine, tetraethylenepentamine, or pentaethylenehexamine.

  The nitrogen content in the above (B) ashless dispersant is preferably 0.5% by mass or more and 6.0% by mass or less, more preferably 0.8% by mass or more and 3.0% by mass or less. When the nitrogen content is less than 0.5% by mass, the dispersibility and solubility are insufficient. Conversely, when the nitrogen content exceeds 6.0% by mass, it may react with NOx in the combustion gas to generate sludge.

  Examples of the derivative of the nitrogen-containing compound mentioned as an example of the component (B) include, for example, monocarboxylic acids such as fatty acids, oxalic acid, phthalic acid, and trimellitic acid having 1 to 30 carbon atoms. Remaining amino by reacting polycarboxylic acids having 2 to 30 carbon atoms such as pyromellitic acid or their anhydrides or ester compounds, alkylene oxides having 2 to 6 carbon atoms, hydroxy (poly) oxyalkylene carbonate, etc. A modified compound by a so-called oxygen-containing organic compound obtained by neutralizing or amidating some or all of the group and / or imino group; boric acid is allowed to act on the above-mentioned nitrogen-containing compound, and the remaining amino group and / or A so-called boron-modified compound obtained by neutralizing or amidating part or all of the imino group; remaining by reacting the above-mentioned nitrogen-containing compound with phosphoric acid A so-called phosphoric acid-modified compound obtained by neutralizing or amidating part or all of an amino group and / or imino group; a sulfur-modified compound obtained by allowing a sulfur compound to act on the above-mentioned nitrogen-containing compound; and the above-mentioned nitrogen-containing compound And modified compounds in which two or more kinds of modifications selected from modification with oxygen-containing organic compounds, boron modification, phosphoric acid modification, and sulfur modification are combined.

  Among these derivatives of nitrogen-containing compounds, boron-modified ashless dispersant is most preferable. Among nitrogen-containing compounds, the use of a boron-modified ashless dispersant is preferred from the standpoint of seizure resistance, but the use of an ashless dispersant that does not contain boron from the viewpoint of sludge dispersibility, high-temperature cleanability, and economy. Is preferred.

  In the present invention, when a boron-containing ashless dispersant is used as the component (B), the boron content in the boron-containing ashless dispersant is 0.5% by mass or more, more preferably 1.0% by mass or more. More preferably, it is 1.5% by mass or more, and particularly preferably 1.8% by mass or more.

When a boron-containing ashless dispersant is used as the component (B), the mass ratio (B / N ratio) between the boron content and the nitrogen content is not particularly limited, but is preferably 0.5 to 1. Preferably it is 0.7-0.9. The higher the B / N ratio is, the easier it is to improve the wear prevention and seizure resistance.
The boron-containing ashless dispersant having a boron content of 0.5% by mass or more here is 10% by mass to 90% by mass, preferably 30% by mass to 70% by mass, for example, mineral oil, synthetic oil. Such a diluent oil may be contained, and the boron content usually means the boron content in a state containing the diluent oil.

The content ratio of the component (B) in the composition of the present invention is usually 0.005% by mass or more and 0.4% by mass or less, preferably 0.01% by mass or more and 0.2% by mass, as the nitrogen content, based on the total amount of the composition. It is 0.01 mass% or less, More preferably, it is 0.01 mass% or less.
In addition, when using a boron-containing ashless dispersant, the content ratio is not particularly limited, but the boron content is preferably 0.001% by mass to 0.1% by mass, more preferably, based on the total amount of the composition. It is 0.005 mass% or more and 0.05 mass% or less, More preferably, it is 0.01 mass% or more and 0.04 mass% or less.

(C) Zinc dithiophosphate (ZnDTP)
The lubricating oil composition of the present invention preferably contains (C) zinc dithiophosphate (ZnDTP) as an antiwear agent. Specifically, zinc dipropyldithiophosphate, zinc dibutyldithiophosphate, zinc dipentyldithiophosphate, zinc dihexyldithiophosphate, zinc diheptyldithiophosphate and zinc dioctyldithiophosphate, preferably 3 carbon atoms. Dialkyldithiophosphate zinc having from 10 to 10 linear or branched (primary, secondary or tertiary, preferably primary or secondary) alkyl groups; zinc diphenyldithiophosphate, and ditolyl Examples thereof include zinc di ((alkyl) aryl) dithiophosphates having an aryl group or alkylaryl group having 6 to 18 carbon atoms, preferably 6 to 10 carbon atoms, such as zinc dithiophosphate, and mixtures thereof.

  (C) The content of ZnDTP is 0.15% by mass or less, preferably 0.10% by mass or less, more preferably 0.08% by mass or less, in terms of phosphorus element, based on the total amount of the composition. Preferably, it is 0.05 mass% or less. When the content of the component (C) exceeds 0.15% by mass, the decomposition product of ZnDTP may cause metal corrosion or wear out the metal-based detergent and deteriorate the cleanliness, which is not preferable. .

(Other additives)
The lubricating oil composition of the present invention is an optional component commonly used in lubricating oils depending on its purpose in order to further improve its performance or to add other required performance in addition to the above configuration. The additive may be further contained. Examples of such additives include antioxidants, antiwear / extreme pressure agents other than ZnDTP, friction modifiers, viscosity index improvers, pour point depressants, corrosion inhibitors / metal deactivators, and rust inhibitors. , Demulsifiers, antifoaming agents, or coloring agents.

  Examples of the antioxidant include ashless antioxidants such as phenols and amines; and metal antioxidants such as copper and molybdenum. The ratio in the case of containing these is 0.1 mass% or more and 5 mass% or less normally on the composition whole quantity basis.

  As an anti-wear / extreme pressure agent other than ZnDTP, any extreme pressure agent and anti-wear agent used for lubricating oil can be used. For example, sulfur-based, phosphorus-based, sulfur-phosphorus extreme pressure agents and the like can be used. Specifically, phosphites, thiophosphites, dithiophosphites, trithiophosphites Esters, phosphate esters, thiophosphate esters, dithiophosphate esters, trithiophosphate esters, amine salts thereof, metal salts thereof, derivatives thereof, dithiocarbamate, zinc dithiocarbamate, molybdenum dithiocarbamate, disulfide , Polysulfides, sulfurized olefins, sulfurized fats and oils, and the like. The ratio in the case of containing these is 0.1 mass% or more and 5 mass% or less normally on the composition whole quantity basis.

  Friction modifier does not contain sulfur such as organic molybdenum compounds containing molybdenum such as molybdenum dithiophosphate and molybdenum dithiocarbamate, molybdenum-amine complexes, molybdenum-succinimide complexes, molybdenum salts of organic acids, molybdenum salts of alcohols, etc. Examples include ashless friction modifiers such as organic molybdenum compounds, fatty acid esters, aliphatic amines, and fatty acid amides. The ratio in the case of containing these is 0.1 mass% or more and 5 mass% or less normally on the composition whole quantity basis.

  Examples of the viscosity index improver include, for example, a polymethacrylate viscosity index improver, an olefin copolymer viscosity index improver, a styrene-diene copolymer viscosity index improver, and a styrene-maleic anhydride copolymer viscosity index improver. Or a polyalkyl styrene type viscosity index improver is mentioned. The weight average molecular weight of these viscosity index improvers is usually 800 to 500,000, preferably 5,000 to 250,000. When the viscosity index improver is contained, the content ratio is 2% by mass or more and 12% by mass or less based on the total amount of the composition.

  As the pour point depressant, for example, a polymethacrylate polymer compatible with the lubricating base oil to be used can be used.

  Examples of the corrosion inhibitor include benzotriazole, tolyltriazole, thiadiazole, and imidazole compounds.

  Examples of metal deactivators include imidazoline, pyrimidine derivatives, alkylthiadiazoles, mercaptobenzothiazoles, benzotriazoles or derivatives thereof, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5-bis. Examples thereof include dialkyldithiocarbamate, 2- (alkyldithio) benzimidazole, and β- (o-carboxybenzylthio) propiononitrile.

  Examples of the rust inhibitor include petroleum sulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenyl succinic acid ester, and polyhydric alcohol ester.

Examples of the demulsifier include polyalkylene glycol nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, and polyoxyethylene alkyl naphthyl ether.
As the defoaming agent, for example, kinematic viscosity at 25 ° C. is 0.1 mm ² / s or more 100 mm ² / s less than the silicone oil, and the like alkenyl succinic acid derivative.

  When these additives are contained in the composition of the present invention, the content is based on the total amount of the composition, and for pour point depressants, corrosion inhibitors, metal deactivators, rust inhibitors, and demulsifiers, respectively. It is usually selected from the range of 0.005 to 5% by mass, and the antifoaming agent is usually in the range of 0.0005 to 1% by mass.

(Nq coefficient)
The Nq coefficient of the composition of the present invention needs to be 0.004 or more, preferably 0.0045 or more, more preferably 0.005 or more. When the Nq coefficient is less than 0.004, the required 1,4-naphthoquinone solubility cannot be obtained, so that there is a possibility that lacquer formation on the cylinder liner increases. Here, the Nq coefficient is a parameter represented by the following formula (1), and ΣNq (P) means the number of moles of phenate soap group in 100 g of the lubricating oil composition.
Nq coefficient = ΣNq (P) + ΣNq (N) (1)
Here, ΣNq (P) represents “(mass% of metal derived from alkaline earth metal phenate in lubricating oil composition) / (metal ratio of alkaline earth metal phenate) / 2A”, and ΣNq (N) is “(Mass% nitrogen derived from ashless dispersant in lubricating oil composition) /14.01”. A is the atomic weight of the alkaline earth metal.

(Kinematic viscosity at 100 ° C)
Kinematic viscosity at 100 ° C. of the lubricating oil composition of the present invention is required to be less 9.3 mm ² / s or more 21.9 mm ² / s, vary depending preferred range applications, land-based diesel engine, For marine high-speed diesel engines and marine 4-cycle trunk piston engines, it is preferably 9.3 mm ² / s to 16.3 mm ² / s, and for marine 2-stroke crosshead engines, preferably 12.5 mm ² / s to 21. 9 mm ² / s or less. If the kinematic viscosity at 100 ° C. is less than 9.3 mm ² / s, the lubricity may be insufficient, and if it exceeds 21.9 mm ² / s, the friction loss may increase.

(Base number)
The base number of the composition of the present invention is required to be 5 mgKOH / g or more and 80 mgKOH / g or less, but it adds excellent high temperature cleanliness and acid neutralization performance even when using a high sulfur fuel. Therefore, Preferably they are 8 mgKOH / g or more and 77 mgKOH / g or less, More preferably, they are 10 mgKOH / g or more and 75 mgKOH / g or less, More preferably, they are 12 mgKOH / g or more and 72 mgKOH / g or less. If the base number is less than 5 mgKOH / g, acid neutralization and cleanliness may be insufficient. If it exceeds 80 mgKOH / g, excessive ash will accumulate on the piston top land, causing liner bore polishing and scuffing. Since it may generate | occur | produce, it is not preferable.

(Amount of metal)
In the lubricating oil composition of the present invention, the lower limit of the amount of metal is preferably 0.08% by mass or more, more preferably 0.2% by mass or more, still more preferably 0.4% by mass or more, and the upper limit is preferably 3%. .6% by mass or less, more preferably 3.2% by mass or less, and further preferably 2.9% by mass or less. When the metal content is less than 0.08% by mass, the neutralizing power of the acidic substance generated by combustion is not sufficient, and the high temperature cleanliness may not be sufficiently exhibited. On the other hand, when it exceeds 3.6 mass%, the ash after combustion adheres to a piston and there exists a possibility of increasing wear of a cylinder.

  In the composition of the present invention, the sulfated ash content is not particularly limited, but the lower limit is preferably 0.5% by mass or more, more preferably 0.9% by mass or more, particularly preferably 1.5% by mass or more, and the upper limit. Is preferably 20% by mass or less, more preferably 10% by mass or less. The sulfated ash here refers to 5. of JIS K2272. The value measured by the method specified in “Testing method for sulfated ash” is mainly attributable to the metal-containing additive.

(Use)
The lubricating oil composition for an internal combustion engine of the present invention is not only a marine medium / high-speed four-cycle diesel engine, but also a vehicle diesel engine, a construction machine diesel engine, a railway diesel engine, a marine and a cogeneration power generation four-cycle. It is suitably used for medium speed trunk piston engines and marine two-stroke crosshead engines. Among them, the present invention is particularly preferably used for a direct injection diesel engine having an average effective pressure of 1.5 MPa or more, or a diesel engine having a common rail type fuel injection type and performing multistage injection of fuel.

Hereinafter, the content of the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these.
<Examples 1-4 and Comparative Examples 1-5>
Lubricating oil compositions (Examples 1 to 4) in the present invention having the compositions shown in Table 1 and comparative lubricating oil compositions (Comparative Examples 1 to 5) were prepared. About the obtained composition, the liner lacquer production | generation test using a private power generation engine and the liner lacquer production | generation test using a caterpillar 1M-PC (1Y73) single cylinder engine were implemented. The solubility of 1,4-naphthoquinone was measured by the following method. The results are shown in Table 1, respectively. The base oils used here are SAE 30 and bright stock belonging to Group I (sulfur content of 0.03 mass% or more, saturation content of less than 90 mass%, viscosity index of 80 to 120). In addition, the lacquer production | generation test using an in-house power generation engine was done only with respect to the lubricating oil composition of Example 1 and Comparative Example 2.

(Lacquer generation test using in-house power generation engine)
Engine: V type 12 cylinder, bore 320mmφ, stroke 420mm, Pme (average effective pressure) 1.82MPa,
Fuel: Low sulfur heavy oil (sulfur content: 0.9% by mass),
Operating conditions: Rotation speed 600rpm, output 3,600kW, test time 3,000h,
Evaluation: The presence or absence of lacquer generation on the cylinder liner was visually evaluated.

(Lacquer generation test using Caterpillar 1M-PC (1Y73) single cylinder engine)
Engine: Caterpillar 1M-PC (1Y73) single cylinder engine, sub-chamber injection type 4-cycle turbocharged diesel engine, bore x stroke: 135 mmφ x 165 mm, output: 31 kW, Pme (average effective pressure): 0.95 MPa, unburned fuel In order to reach the liner and generate lacquer, the port diameter of the sub chamber was changed from the standard 7.5 mmφ to 9.5 mmφ,
Fuel: Commercial diesel oil,
Operating conditions: intake air temperature: 82 ° C., intake air pressure: 49 MPa, output: 31 kW, test time: 120 h,
Evaluation: The presence or absence of lacquer generation on the cylinder liner was visually evaluated. After the test, the liner was divided into two parts, and then a liner score according to JPI-5S-15-05 “Land Diesel Engine Piston Evaluation Method” was performed. A higher liner score is better with less lacquering.

(Solubility of 1,4-naphthoquinone)
The solubility of 1,4-naphthoquinone was measured by the following procedure.
(1) 1.0 g of 1,4-naphthoquinone (Tokyo Chemical Industry Reagent grade 1) was weighed into a 100 ml beaker, and the weight X ₀ g of the weighed 1,4-naphthoquinone was recorded.
(2) 50.0 g of the lubricating oil composition of the example or comparative example was poured into the beaker, and the weight Y ₀ g of the test oil was recorded.
(3) After putting a magnetic stirrer in a beaker, it was placed on a hot plate and heated at a rotation speed of the stirrer of 500 rpm.
(4) The solution temperature was controlled at 60 ° C. and stirred for 3 hours to dissolve 1,4-naphthoquinone.
(5) The solution was transferred to an ultracentrifuge bottle and allowed to stand for 48 hours.
(6) The bottle containing the solution was placed in an ultracentrifuge and centrifuged at 50,000 G for 30 minutes.
(7) After centrifugation, the supernatant was removed.
(8) The bottle was filled with n-hexane (special grade of Wako Pure Chemical Industries, Ltd.) and centrifuged at 50,000 G for 30 minutes.
(9) After centrifugation, the supernatant was removed, and the bottle was filled with n-hexane (special grade of Wako Pure Chemical Industries, Ltd.) and centrifuged at 50,000 G for 30 minutes.
(10) After centrifugation, the supernatant was removed, 1,4-naphthoquinone remaining in the bottle after air drying was weighed, and the weight X ₁ g of the weighed 1,4-naphthoquinone was recorded.
(11) The solubility of 1,4-naphthoquinone (the amount of 1,4-naphthoquinone dissolved per 100 g of oil) was calculated by the following equation.
Solubility of 1,4-naphthoquinone (g / 100 g) = (X ₀ −X ₁ ) × 100 / Y ₀

  The contents (mass%) of the base oils 1 and 2 are values based on the entire base oil. Moreover, content (in mass%) of (A) component-(C) component is a value on the basis of the whole lubricating oil composition.

  As is apparent from the results in Table 1, the lubricating oil for internal combustion engines of the present invention having an Nq coefficient of 0.004 or more and a 1,4-naphthoquinone solubility of 1.3 g / more with respect to 100 g of the lubricating oil composition. It was confirmed that the composition (Examples 1 to 4) produced less cylinder liner lacquer in the engine test.

  While the present invention has been described in connection with embodiments that are presently the most practical and preferred, the present invention is not limited to the embodiments disclosed herein. However, the lubricating oil composition for an internal combustion engine with such a change can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification. It must be understood as included.

Claims (5)

A lubricating oil composition comprising a lubricating base oil composed of mineral oil and / or synthetic oil, and (A) a metallic detergent,
Formula of the lubricating oil composition (1) Nq coefficients shown by 0.004 or more, a kinematic viscosity of 100 ° C. is 9.3 mm ² / s or more 21.9 mm ² / s or less, and the base value is 5 mgKOH / g or more 80mgKOH / G or less,
A lubricating oil composition for internal combustion engines, wherein the solubility of 1,4-naphthoquinone in 100 g of the lubricating oil composition is 1.3 g / or more.
Nq coefficient = ΣNq (P) + ΣNq (N) (1)
(In the formula (1), ΣNq (P) represents “(mass% of metal derived from alkaline earth metal phenate in lubricating oil composition) / (metal ratio of alkaline earth metal phenate) / 2A”, and ΣNq (N ) Represents “(mass% of nitrogen derived from the ashless dispersant in the lubricating oil composition) /14.01”, where A represents the atomic weight of the alkaline earth metal.)   The lubricating oil composition for an internal combustion engine according to claim 1, wherein (A) the metallic detergent is calcium phenate and / or calcium salicylate.   Furthermore, the lubricating oil composition for internal combustion engines of Claim 1 or 2 which contains 2 mass% or more of (B) polybutenyl succinimides on the basis of the lubricating oil composition whole quantity.   The lubricating oil composition for an internal combustion engine according to any one of claims 1 to 3, which is used for a direct injection diesel engine having an average effective pressure of 1.5 MPa or more.   The lubricating oil composition for an internal combustion engine according to any one of claims 1 to 3, which is used for a diesel engine having a common rail type fuel injection format and multistage injection of fuel.