CN112888769B

CN112888769B - Lubricating oil composition

Info

Publication number: CN112888769B
Application number: CN201980069747.3A
Authority: CN
Inventors: 星野耕治; 楠原慎太郎; 武藤明男; 松田裕充
Original assignee: Eneos Corp
Current assignee: Eneos Corp
Priority date: 2018-11-07
Filing date: 2019-11-06
Publication date: 2022-09-27
Anticipated expiration: 2039-11-06
Also published as: EP3878931A1; JP7320935B2; JP2020076004A; EP3878931B1; EP3878931A4; CN112888769A; WO2020095943A1

Abstract

The invention provides a lubricating oil composition for an engine with a supercharger, which can well balance coking resistance, LSPI inhibition capability and high-temperature cleaning performance. The lubricating oil composition for a supercharger-equipped engine of the present invention is characterized by comprising: (A) a lubricant base oil, (B) a calcium-based detergent having a calcium content of 1100 ppm by mass or more and 1900 ppm by mass or less based on the total amount of the lubricant composition, (C) a magnesium-based detergent, (D) a viscosity index improver comprising at least 1 selected from the group consisting of a styrene-diene copolymer and an ethylene- α -olefin copolymer, and (E) a nitrogen-containing dispersant; the nitrogen content is 700 ppm by mass or more based on the total amount of the lubricating oil composition.

Description

Lubricating oil composition

Technical Field

The present invention relates to a lubricating oil composition, and more particularly to a lubricating oil composition for an internal combustion engine, particularly a lubricating oil composition for an engine with a supercharger.

Background

In recent years, various demands have been made for automobile internal combustion engines, such as downsizing, high power output, fuel economy, and exhaust gas control, and many lubricating oil compositions for internal combustion engines have been studied for the purpose of fuel economy. In particular, for the purpose of reducing fuel consumption of an internal combustion engine for an automobile, it has been proposed to replace a conventional natural-intake gasoline engine with an engine (supercharged small engine) having a supercharger and a lower exhaust gas amount. In a supercharged and downsized engine, by providing a supercharger, the amount of exhaust gas can be reduced while maintaining the output, and fuel consumption can be reduced. On the other hand, in a supercharged small engine, if the torque is increased in a Low rotation region, a phenomenon (LSPI: Low Speed Pre-Ignition) may occur in which the Ignition in the cylinder is earlier than a predetermined time. If LSPI is generated, the energy loss increases, which not only restricts fuel efficiency and low-speed torque, but also causes damage to the engine.

In order to satisfy various performances of the lubricating oil composition for an internal combustion engine, various additives such as an antiwear agent, a metal detergent, an ashless dispersant, and an antioxidant are blended with a lubricating base oil (see patent document 1). Since the above-mentioned LSPI production is suspected to be an influence of the lubricating oil, a function of suppressing the LSPI production is required for the lubricating oil. However, for example, when the amount of the calcium-based detergent is reduced in order to reduce the frequency of LSPI generation, the detergency of the lubricating oil composition tends to be deteriorated.

Further, although additives containing molybdenum and phosphorus tend to reduce the frequency of LSPI generation, friction modifiers containing molybdenum and antiwear agents containing phosphorus are likely to decompose into deposits at high temperatures. Therefore, if the amounts of the friction modifier having molybdenum and the antiwear agent having phosphorus are increased in order to reduce the frequency of LSPI generation, there is a problem that the high-temperature detergency is lowered. That is, the technique of preventing LSPI and the technique of ensuring the performance required for the lubricating oil composition sometimes contradict each other, and it is necessary to achieve both of them. Therefore, in order to reduce the frequency of LSPI generation, a lubricating oil composition has been proposed in which the amounts of calcium, magnesium, molybdenum and phosphorus satisfy a predetermined relational expression, and the amounts of calcium and magnesium and the amount of nitrogen derived from an ashless dispersant satisfy a predetermined relational expression (see patent document 2).

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2003-155492

Patent document 2: japanese patent laid-open publication No. 2015-163673

Disclosure of Invention

In recent years, coking in a turbocharger has been regarded as a problem with the reduction in viscosity of a lubricating oil, and a turbocharger in a diesel engine is more likely to be exposed to high temperatures than a gasoline engine, and coking resistance (heat resistance) of a lubricating oil is more required.

However, the present inventors have studied the invention described in patent document 2 and found that in a lubricating oil composition using a combination of a calcium-based detergent and a magnesium-based detergent, the scorch resistance is insufficient when a poly (meth) acrylate is used as a viscosity index improver. The object of the invention is therefore: the invention provides a lubricating oil composition for an engine with a supercharger, which can well balance coking resistance, LSPI inhibition capability and high-temperature cleaning performance.

The present inventors have conducted extensive studies to solve the above problems, and as a result, have found that the above problems can be solved by using a predetermined polymer as a viscosity index improver and adjusting the nitrogen content to a predetermined range in a lubricating oil composition using a combination of a calcium-based detergent and a magnesium-based detergent, and have completed the present invention.

That is, according to the present invention, the following inventions are provided.

[1] A lubricating oil composition for an engine with a supercharger, comprising:

(A) a lubricant base oil,

(B) a calcium-based detergent containing calcium in an amount of 1100 to 1900 ppm by mass based on the total amount of the lubricating oil composition,

(C) a magnesium-based cleaning agent which is capable of removing magnesium,

(D) at least 1 viscosity index improver selected from the group consisting of styrene-diene copolymers and ethylene-alpha-olefin copolymers, and

(E) a nitrogen-containing dispersant;

the nitrogen content is 700 ppm by mass or more based on the total amount of the lubricating oil composition.

[2] The lubricating oil composition according to [1], wherein the calcium detergent (B) is calcium salicylate.

[3] The lubricating oil composition according to [1] or [2], wherein the magnesium-based detergent (C) is magnesium salicylate.

[4] The lubricating oil composition according to any one of [1] to [3], wherein the content of the magnesium-based detergent (C) is 100 mass ppm or more and 1000 mass ppm or less in terms of magnesium amount based on the total amount of the lubricating oil composition.

[5] The lubricating oil composition according to any one of [1] to [4], wherein the viscosity index improver (D) is a styrene-diene copolymer.

[6] The lubricating oil composition according to any one of [1] to [5], wherein the content of the viscosity index improver (D) is 0.1 to 20 mass% based on the total amount of the lubricating oil composition.

[7] The lubricating oil composition according to any one of [1] to [6], further comprising (F) an ashless friction modifier.

[8] The lubricating oil composition according to any one of [1] to [7], further comprising (G) a molybdenum-containing compound.

[9] The lubricating oil composition according to any one of [1] to [8], further comprising zinc alkyl phosphate as an (H) antiwear agent.

[10]According to [1]～[9]The lubricating oil composition as claimed in any one of the preceding claims, wherein the kinematic viscosity at 100 ℃ is 4.0mm ² More than second and less than 12.5mm ² In seconds.

[11] The lubricating oil composition according to any one of [1] to [10], wherein the HTHS viscosity at 150 ℃ is 1.7 mPas or more and less than 3.5 mPas.

[12] The lubricating oil composition according to any one of [1] to [11], wherein the viscosity index improver does not contain a poly (meth) acrylate.

[13] The lubricating oil composition according to any one of [1] to [12], wherein the nitrogen content is 1000 mass ppm or more based on the total amount of the composition.

[14] The lubricating oil composition according to any one of [1] to [13], wherein the lubricating oil composition is used for both gasoline and diesel engines.

[15] The lubricating oil composition according to any one of [1] to [13], wherein the lubricating oil composition is for a diesel engine.

The lubricating oil composition of the present invention has good balance among scorch resistance, LSPI inhibition ability, and high-temperature detergency. Such a lubricating oil composition can be suitably used for engine applications with a supercharger, which require high coking resistance.

Detailed Description

[ lubricating oil composition ]

The lubricating oil composition of the present invention comprises at least: (A) a lubricant base oil, (B) a calcium-based detergent, (C) a magnesium-based detergent, (D) a viscosity index improver, and (E) a nitrogen-containing dispersant, and may further contain (F) an ashless friction modifier, (G) a molybdenum-containing compound, and (H) an anti-wear agent. The lubricating oil composition of the present invention can be suitably used for an internal combustion engine, particularly an engine with a supercharger. In addition, the lubricating oil composition of the present invention can be used for both gasoline and diesel engines, as well as diesel engines. Hereinafter, each component constituting the lubricating oil composition of the present invention will be described in detail.

[ (A) lubricating base oil ]

The lubricant base oil is not particularly limited, and examples thereof include paraffinic base oils and normal paraffinic base oils, isoparaffinic base oils, and mixtures thereof, which are obtained by purifying a lubricant fraction obtained by atmospheric distillation and/or vacuum distillation of a crude oil by a combination of 1 or 2 or more kinds of purification treatments selected from solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrotreating, sulfuric acid washing, clay treatment, and the like.

Preferred examples of the lubricant base oil include base oils obtained by refining the feedstock oil and/or a lubricant fraction recovered from the feedstock oil by a predetermined refining method using the following base oils (1) to (8) as a raw material and recovering the lubricant fraction.

(1) Distillate oil obtained by atmospheric distillation of paraffinic crude oil and/or mixed crude oil

(2) Distillate oil (WVGO) obtained by atmospheric distillation of residue oil of paraffin crude oil and/or mixed crude oil under reduced pressure

(3) Waxes obtained by a lubricating oil dewaxing step (slack wax, etc.) and/or synthetic waxes obtained by a gas-to-liquids (GTL) process, etc. (Fischer-Tropsch wax, GTL wax, etc.)

(4) 1 or 2 or more kinds of mixed oils selected from the base oils (1) to (3) and/or a mild hydrocracked oil of the mixed oils

(5) 2 or more kinds of mixed oils selected from the base oils (1) to (4)

(6) Deasphalted oil (DAO) of base oil (1), (2), (3), (4) or (5)

(7) Light hydrocracking treated oil (MHC) of base oil (6)

(8) 2 or more kinds of mixed oils selected from the base oils (1) to (7).

The above-mentioned predetermined purification method is preferably hydropurification such as hydrocracking or hydrotreating; refining furfural by solvent extraction and other solvents; dewaxing such as solvent dewaxing and catalytic dewaxing; clay purification by acid clay, activated clay, or the like; chemical (acid or alkali) washing such as sulfuric acid washing and caustic soda washing. In the present invention, 1 of these purification methods may be carried out alone, or 2 or more of them may be combined. In the case of combining 2 or more purification methods, the order is not particularly limited and can be selected as appropriate.

Further, as the lubricant base oil, the following base oil (9) or (10) obtained by subjecting a base oil selected from the above base oils (1) to (8) or a lubricant fraction recovered from the base oil to a predetermined treatment is particularly preferable.

(9) A base oil selected from the base oils (1) to (8) or a lubricant fraction recovered from the base oil is subjected to hydrocracking, and the product thereof or the lubricant fraction recovered from the product thereof by distillation or the like is subjected to dewaxing treatment such as solvent dewaxing, catalytic dewaxing or the like, or is subjected to the dewaxing treatment and then to distillation to obtain a hydrocracked base oil.

(10) A base oil selected from the base oils (1) to (8) or a lubricant oil fraction recovered from the base oil is hydroisomerized, and the product thereof or the lubricant oil fraction recovered from the product thereof by distillation or the like is subjected to dewaxing treatment such as solvent dewaxing, catalytic dewaxing or the like, or is subjected to the dewaxing treatment and then distilled to obtain a hydroisomerized base oil. The dewaxing step is preferably a base oil produced through a catalytic dewaxing step.

In addition, when the lubricant base oil of the above (9) or (10) is obtained, a solvent refining treatment and/or a hydrotreating treatment step may be further performed at an appropriate stage as necessary.

The catalyst used for the hydrocracking and hydroisomerization is not particularly limited, but a hydrocracking catalyst in which a composite oxide having cracking activity (for example, aluminum silicate, alumina boron oxide, silica zirconia, or the like) or a product obtained by combining 1 or more of the composite oxides and binding with a binder is supported on a carrier and a metal having hydrogenation ability (for example, 1 or more of a metal of group VIa, a metal of group VIII in the periodic table) is supported on the carrier, or a hydroisomerization catalyst in which a metal having hydrogenation ability containing at least 1 or more of metals of group VIII is supported on a carrier containing zeolite (for example, ZSM-5, zeolite β, SAPO-11, or the like) is preferably used. The hydrocracking catalyst and the hydroisomerization catalyst may be used in combination by stacking, mixing, or the like.

The reaction conditions in hydrocracking and hydroisomerization are not particularly limited, but are preferably 0.1 to 20MPa in hydrogen partial pressure, 150 to 450 ℃ in average reaction temperature, and 0.1 to 3.0hr LHSV ^－1 And a hydrogen/oil ratio of 50 to 20000 scf/b.

The kinematic viscosity at 100 ℃ of the lubricant base oil is preferably 2.0mm ² A length of at least one second, more preferably 2.5mm ² At least one second, and more preferably 3.0mm ² At least one second, and more preferably 3.5mm ² At least one second, and preferably 8.0mm ² A second or less, more preferably 7.0mm ² A second or less, more preferably 6.0mm ² A second or less, and more preferably 5.0mm ² And less than second. When the kinematic viscosity at 100 ℃ of the lubricant base oil is within the above numerical range, sufficient fuel economy can be obtained, and oil film formation at the lubricated part is favorably performed, resulting in excellent lubricity. In the present specification, "kinematic viscosity at 100 ℃" means kinematic viscosity at 100 ℃ measured in accordance with ASTM D-445.

The kinematic viscosity at 40 ℃ of the lubricant base oil is preferably 6.0mm ² A length of at least one second, more preferably 8.0mm ² At least one second, more preferably 10mm ² At least one second, more preferably 15mm ² At least one second, preferably 40mm ² A second or less, more preferably 30mm ² A second or less, more preferably 25mm ² A second or less, and more preferably 20mm ² And less than second. When the kinematic viscosity at 40 ℃ of the lubricant base oil is within the above numerical range, sufficient fuel economy can be obtained, and oil film formation at the lubricated part is favorably performed, resulting in excellent lubricity. In the present specification, "kinematic viscosity at 40 ℃" means kinematic viscosity at 40 ℃ measured in accordance with ASTM D-445.

The viscosity index of the lubricant base oil is preferably 100 or more, more preferably 110 or more, and further preferably 120 or more. When the viscosity index is within the above numerical range, the lubricating oil composition is excellent in viscosity-temperature characteristics, thermal oxidation stability and volatilization prevention, and can be reduced in friction coefficient and improved in anti-wear properties. In the present specification, "viscosity index" refers to a viscosity index measured in accordance with JIS K2283-1993.

15 ℃ of lubricating base oilDensity (p) ₁₅ ) Preferably 0.860 or less, more preferably 0.850 or less, and still more preferably 0.840 or less. The density at 15 ℃ in the present specification means the density at 15 ℃ measured in accordance with JIS K2249-1995.

The pour point of the lubricant base oil is preferably-10 ℃ or lower, more preferably-12.5 ℃ or lower, and still more preferably-15 ℃ or lower. When the pour point is within the above numerical range, the low-temperature fluidity of the entire lubricating oil composition can be improved. In the present specification, "pour point" refers to a pour point measured in accordance with JIS K2269-1987.

The amount of sulfur in a lubricant base oil depends on the sulfur content of its feedstock. For example, when a raw material containing substantially no sulfur, such as a synthetic wax component obtained by a fischer-tropsch synthesis reaction or the like, is used, a lubricating base oil containing substantially no sulfur can be obtained. When a raw material containing sulfur, such as slack wax obtained in a refining process of a lubricant base oil or microcrystalline wax obtained in a refining process, is used, sulfur in the obtained lubricant base oil is usually 100 ppm by mass or more. The sulfur content in the lubricant base oil is preferably 100 mass ppm or less, more preferably 50 mass ppm or less, and still more preferably 10mass ppm or less, from the viewpoint of improving thermal oxidation stability and low vulcanization. In the present specification, "sulfur" refers to a pour point measured according to JIS K2541-2003.

% C of lubricating base oil _P Preferably 70 or more, more preferably 75 or more, and still more preferably 80 or more. If% C of the lubricating base oil _P When the amount is within the above range, the viscosity-temperature characteristics, thermal/oxidative stability and friction characteristics are good, and the solubility of the additive is good.

% C of lubricating base oil _N Preferably 30 or less, more preferably 25 or less, still more preferably 20 or less, and particularly preferably 15 or less. In addition,% C of lubricating base oil _N Preferably 1 or more, more preferably 4 or more. If% C of the lubricating base oil _N Within the above numerical range, viscosity-temperature characteristic heat oxidationThe stability and friction characteristics were good, and the solubility of the additive was good.

% C of lubricating base oil _A Preferably 2 or less, more preferably 1 or less, still more preferably 0.8 or less, and particularly preferably 0.5 or less. If% C of the lubricating base oil _A Within the above numerical range, the viscosity-temperature characteristics, thermal/oxidative stability and fuel economy are good.

In the present specification,% C _P 、％C _N And% C _A The percentages are the percentage of the number of paraffinic carbon atoms to the total number of carbon atoms, the percentage of the number of naphthenic carbon atoms to the total number of carbon atoms and the percentage of the number of aromatic carbon atoms to the total number of carbon atoms, respectively, which are determined by the method (n-D-M ring analysis) according to ASTM D3238-85. That is, the above% C _P 、％C _N And% C _A The preferable range of (C) is based on the value obtained by the above method, for example, the% C obtained by the above method even for a lubricant base oil containing no naphthenes _N Values exceeding 0 can also be displayed.

The content of the saturated component in the lubricant base oil is preferably 90 mass% or more, preferably 95 mass% or more, and more preferably 99 mass% or more, based on the total amount of the lubricant base oil. The proportion of the cyclic saturated component in the saturated component is preferably 40% by mass or less, preferably 35% by mass or less, preferably 30% by mass or less, more preferably 25% by mass or less, and still more preferably 21% by mass or less. The proportion of the cyclic saturated component in the saturated component is preferably 5% by mass or more, and more preferably 10% by mass or more. When the content of the saturated component and the ratio of the cyclic saturated component to the saturated component satisfy the above conditions, the viscosity-temperature characteristics and the thermal/oxidative stability can be improved, and when an additive is blended into the lubricant base oil, the additive can be dissolved and held in the lubricant base oil sufficiently and stably, and the function of the additive can be expressed at a higher level. Further, the friction characteristics of the lubricant base oil itself can be improved, and as a result, the friction reduction effect and, hence, the fuel economy can be improved. In the present specification, the saturation component refers to a value measured in accordance with ASTM D2007-93.

In addition, a similar method can be used to obtain the same result in the separation method of the saturated component or the composition analysis of the cyclic saturated component, the acyclic saturated component, and the like. For example, in addition to the method described in ASTM D2007-93, a method described in ASTM D2425-93, a method described in ASTM D2549-91, a method based on High Performance Liquid Chromatography (HPLC), a method in which these methods are improved, and the like can be given.

The aromatic component in the lubricant base oil is preferably 10% by mass or less, more preferably 5% by mass or less, further preferably 4% by mass or less, further more preferably 3% by mass or less, most preferably 2% by mass or less, and may be 0% by mass, based on the total amount of the lubricant base oil. When the aromatic component content is within the above numerical range, the viscosity-temperature characteristics, thermal/oxidative stability, and frictional characteristics, and further, the volatility prevention and low-temperature viscosity characteristics are good.

In the present specification, the aromatic component means a value measured in accordance with ASTM D2007-93. The aromatic component generally includes anthracene, phenanthrene, alkylated products thereof, compounds in which four or more benzene rings are condensed, aromatic compounds having hetero atoms such as pyridines, quinolines, phenols, and naphthols, in addition to alkylbenzene and alkylnaphthalene.

As the lubricant base oil, a group II base oil, a group III base oil, a group IV base oil, or a group V base oil of API base oil classification, or a mixed base oil thereof can be preferably used. The API group II base oil is a mineral oil base oil having 0.03 mass% or less of sulfur, 90 mass% or more of a saturated component, and a viscosity index of 80 or more and less than 120. The API group III base oil is a mineral oil base oil having 0.03 mass% or less of sulfur, 90 mass% or more of a saturated component, and a viscosity index of 120 or more. API group IV base oils are polyalphaolefin base oils. API group V base oils are ester based base oils.

As the lubricant base oil, synthetic base oil can be used. Examples of the synthetic base oil include polyalphaolefins and hydrogenated products thereof, isobutylene oligomers and hydrogenated products thereof, isoparaffins, alkylbenzenes, alkylnaphthalenes, diesters (ditridecyl glutarate, di (2-ethylhexyl) adipate, diisodecyl adipate, ditridecyl adipate, di (2-ethylhexyl) sebacate, etc.), polyol esters (trimethylolpropane octanoate, trimethylolpropane nonanoate, pentaerythritol 2-ethylhexanoate, pentaerythritol nonanoate, etc.), polyoxyalkylene glycols, dialkyl diphenyl ethers, polyphenylene ethers, and mixtures thereof, and among them, polyalphaolefins are preferable. Typically, the polyalphaolefin includes oligomers or cooligomers (e.g., 1-octene oligomers, decene oligomers, ethylene-propylene cooligomers, etc.) of an alpha-olefin having 2 to 32 carbon atoms, preferably 6 to 16 carbon atoms, and hydrogenated products thereof.

The method for producing the polyalphaolefin is not particularly limited, and for example, a method of polymerizing an alpha-olefin in the presence of a polymerization catalyst such as a catalyst comprising a complex of aluminum trichloride or boron trifluoride with water, an alcohol (ethanol, propanol, butanol, etc.), a carboxylic acid or an ester is exemplified.

The lubricant base oil may be composed of a single base oil component as the whole lubricant base oil, or may contain a plurality of base oil components.

When the lubricating oil composition is a multigrade oil, the content of the lubricating base oil in the lubricating oil composition is usually 70% by mass or more, preferably 75% by mass or more, more preferably 80% by mass or more, and usually 90% by mass or less, based on the total amount of the lubricating oil composition. When the lubricating oil composition is a single-grade oil, it is usually 80% by mass or more, preferably 85% by mass or more, more preferably 90% by mass or more, and usually 95% by mass or less, based on the total amount of the lubricating oil composition.

[ (B) calcium-based cleaning agent ]

Examples of the calcium-based detergent include a phenol-based detergent, a sulfonate-based detergent, and a salicylate-based detergent. In addition, these cleaning agents can be used alone or in combination of 2 or more.

As the phenate-based detergent, an overbased salt of a calcium salt of a compound having a structure represented by the following formula (1) can be preferably exemplified.

In the formula (1), R ¹ Represents a linear or branched, saturated or unsaturated alkyl or alkenyl group having 6 to 21 carbon atoms, m is a polymerization degree and represents an integer of 1 to 10, A represents a thioether (-S-) group or a methylene (-CH) ₂ -) group, x represents an integer of 1 to 3. In addition, R is ¹ Combinations of more than 2 different groups are also possible. R in the formula (1) ¹ The number of carbon atoms of (A) is preferably 9 to 18, more preferably 9 to 15. If R is ¹ When the number of carbon atoms of (b) is within the above numerical range, the solubility and heat resistance are good. The polymerization degree m in the formula (1) is preferably 1 to 4. When the polymerization degree m is within this range, the heat resistance can be improved.

As the sulfonate-based cleaning agent, calcium salts of alkyl aromatic sulfonic acids obtained by sulfonating alkyl aromatic compounds, or alkali salts or overbased salts thereof can be preferably exemplified. The alkyl aromatic compound preferably has a weight average molecular weight of 400 to 1500, more preferably 700 to 1300.

Examples of the alkyl aromatic sulfonic acid include so-called petroleum sulfonic acid and synthetic sulfonic acid. Examples of the petroleum sulfonic acid include a product obtained by sulfonating an alkyl aromatic compound in a lubricating oil fraction of a mineral oil, and so-called mahogany acid which is a by-product in the production of white oil. Examples of the synthetic sulfonic acid include a product obtained by sulfonating alkylbenzene having a linear or branched alkyl group, which is obtained by recovering a by-product from an alkylbenzene manufacturing plant or alkylating benzene with polyolefin, which is a raw material of a detergent. Another example of the synthetic sulfonic acid is one obtained by sulfonating alkylnaphthalenes such as dinonylnaphthalene. The sulfonating agent used in sulfonating these alkyl aromatic compounds is not particularly limited, and fuming sulfuric acid or sulfuric anhydride may be used, for example.

The salicylate-based detergent preferably includes calcium salicylate, and an alkaline salt or an overbased salt thereof. As calcium salicylate, a compound represented by the following formula (2) can be preferably exemplified.

In the above formula (2), R ² Each independently represents an alkyl group or an alkenyl group having 14 to 30 carbon atoms, and M represents calcium. n represents 1 or 2, preferably 1, but may be a mixture of a compound in which n ═ 1 and a compound in which n ═ 2. When n is 2, R is ² Combinations of different groups are also possible. A preferred embodiment of the salicylate-based detergent includes calcium salicylate represented by the general formula (2) above, wherein n is 1, and an alkaline salt or an overbased salt thereof.

The method for producing calcium salicylate is not particularly limited, and a known method for producing monoalkylsalicylate can be used. For example, calcium salicylate can be obtained by: monoalkylsalicylic acids obtained by alkylating phenol with an olefin and then carboxylating the product with carbon dioxide or the like, or monoalkylsalicylic acids obtained by alkylating salicylic acid with an equivalent amount of the olefin, are reacted with a calcium base such as an oxide or hydroxide of calcium, or these monoalkylsalicylic acids are once prepared into an alkali metal salt such as a sodium salt or a potassium salt and then metal-exchanged with a calcium salt.

The calcium-based detergent may be overbasing with carbonate (calcium carbonate) or overbasing with borate (calcium borate).

The method for obtaining a calcium-based detergent overbasing with a calcium carbonate is not particularly limited, and for example, a neutral salt of a calcium-based detergent (calcium phenate, calcium sulfonate, calcium salicylate, etc.) may be reacted with a calcium base (calcium hydroxide, calcium oxide, etc.) in the presence of carbon dioxide.

The method for obtaining a calcium-based detergent overbasing with a calcium borate is not particularly limited, and the calcium-based detergent can be obtained by reacting a neutral salt of a calcium-based detergent (calcium phenate, calcium sulfonate, calcium salicylate, etc.) with a calcium base (calcium hydroxide, oxide, etc.) in the presence of boric acid, boric anhydride, or a borate.

As the calcium-based detergent, calcium phenate, calcium sulfonate, calcium salicylate, or a combination thereof can be used, and calcium salicylate is preferably used.

The total base number of the calcium-based detergent is not particularly limited, but is preferably 20mgKOH/g or more, more preferably 50mgKOH/g or more, further preferably 100mgKOH/g or more, and further preferably 500mgKOH/g or less, more preferably 400mgKOH/g or less, further preferably 350mgKOH/g or less. When the total base number of the calcium-based detergent is within the above numerical range, the acid-neutralizing property required for the lubricating oil can be maintained, and the high-temperature detergency can be further improved. When 2 or more calcium detergents are mixed and used, the base number obtained by mixing is preferably within the above range. The total base number is a value measured by ASTM D2896.

The content of the calcium-based detergent in the lubricating oil composition is 1100 mass ppm or more and 1900 mass ppm or less, preferably 1150 mass ppm or more, more preferably 1200 mass ppm or more, and preferably 1850 mass ppm or less, more preferably 1800 mass ppm or less in terms of calcium content, based on the total amount of the lubricating oil composition. When the content of the calcium-based detergent is within the above numerical range, the high-temperature detergency can be improved while maintaining the scorch resistance and the LSPI inhibiting ability.

[ (C) magnesium-based cleaning agent ]

Examples of the magnesium-based detergent include a phenol-based detergent, a sulfonate-based detergent, and a salicylate-based detergent. These cleaning agents may be used alone or in combination of 2 or more.

As the phenol salt-based detergent, an overbased salt of a magnesium salt of a compound having a structure represented by the following formula (3) can be preferably exemplified.

In the formula (3), R ³ Represents a linear or branched, saturated or unsaturated alkyl or alkenyl group having 6 to 21 carbon atoms, m is a polymerization degree and represents an integer of 1 to 10, A represents a thioether (-S-) group or a methylene (-CH) ₂ -) group, x represents an integer of 1 to 3. In addition, R is ³ Combinations of 2 or more different groups are also possible. R in the formula (3) ³ The number of carbon atoms of (A) is preferably 9 to 18, more preferably 9 to 15. If R is ³ When the number of carbon atoms of (b) is within the above numerical range, the solubility and heat resistance are good. The polymerization degree m in the formula (3) is preferably 1 to 4. When the polymerization degree m is within this range, the heat resistance can be improved.

As the sulfonate-based cleaning agent, a magnesium salt of an alkyl aromatic sulfonic acid obtained by sulfonating an alkyl aromatic compound, or a basic salt or an overbased salt thereof can be preferably exemplified. The alkyl aromatic compound preferably has a weight average molecular weight of 400 to 1500, more preferably 700 to 1300.

Examples of the alkyl aromatic sulfonic acid include so-called petroleum sulfonic acid and synthetic sulfonic acid. Examples of the petroleum sulfonic acid include a product obtained by sulfonating an alkyl aromatic compound in a lubricating oil fraction of mineral oil, and so-called mahogany acid which is a by-product in the production of white oil. Examples of the synthetic sulfonic acid include those obtained by sulfonating alkylbenzene having a linear or branched alkyl group, which is obtained by recovering a by-product from an alkylbenzene manufacturing plant as a raw material of a detergent or by alkylating benzene with polyolefin. Another example of the synthetic sulfonic acid is one obtained by sulfonating alkylnaphthalenes such as dinonylnaphthalene. The sulfonating agent used in sulfonating these alkyl aromatic compounds is not particularly limited, and fuming sulfuric acid or sulfuric anhydride may be used, for example.

As the salicylate-based detergent, magnesium salicylate, and an alkaline salt or an overbased salt thereof can be preferably exemplified. As the magnesium salicylate, a compound represented by the following formula (4) can be preferably exemplified.

In the above formula (4), R ⁴ Each independently represents an alkyl group or an alkenyl group having 14 to 30 carbon atoms, and M represents magnesium. n represents 1 or 2, preferably 1, but may be a mixture of a compound in which n ═ 1 and a compound in which n ═ 2. When n is 2, R is ⁴ Combinations of different groups are also possible. A preferred embodiment of the salicylate-based detergent includes magnesium salicylate represented by the general formula (4) wherein n is 1, and an alkaline salt or an overbased salt thereof.

The method for producing magnesium salicylate is not particularly limited, and a known method for producing monoalkylsalicylate can be used. For example, calcium salicylate can be obtained by: monoalkylsalicylic acids obtained by alkylating phenol with an olefin and then carboxylating the product with carbon dioxide or the like, or monoalkylsalicylic acids obtained by alkylating salicylic acid with an equivalent amount of the olefin, are reacted with a magnesium base such as an oxide or hydroxide of magnesium, or these monoalkylsalicylic acids are once prepared into an alkali metal salt such as a sodium salt or a potassium salt and then metal-exchanged with a magnesium salt.

The magnesium-based detergent may be overbasing with carbonate (magnesium carbonate) or overbasing with borate (magnesium borate).

The method for obtaining a magnesium-based detergent overbasing with a magnesium carbonate is not particularly limited, and for example, a neutral salt of a magnesium-based detergent (magnesium phenate, magnesium sulfonate, magnesium salicylate, etc.) and a magnesium base (magnesium hydroxide, oxide, etc.) may be reacted in the presence of carbon dioxide.

The method for obtaining a magnesium-based detergent overbasing with a magnesium borate is not particularly limited, and the magnesium-based detergent can be obtained by reacting a neutral salt of a magnesium-based detergent (magnesium phenoxide, magnesium sulfonate, magnesium salicylate, etc.) with a magnesium base (magnesium hydroxide, magnesium oxide, etc.) in the presence of boric acid, boric anhydride or a borate.

As the magnesium-based detergent, magnesium phenate, magnesium sulfonate, magnesium salicylate, or a combination thereof can be used, and magnesium salicylate is preferably used.

The total base number of the magnesium-based cleaning agent is not particularly limited, but is preferably 20mgKOH/g or more, more preferably 50mgKOH/g or more, further preferably 100mgKOH/g or more, and further preferably 500mgKOH/g or less, more preferably 400mgKOH/g or less. When the total base number of the magnesium-based detergent is within the above numerical range, the acid-neutralizing property required for the lubricating oil can be maintained, and the high-temperature detergency can be further improved. When 2 or more magnesium-based detergents are mixed and used, the base number obtained by mixing is preferably within the above range. The total base number is a value measured by ASTM D2896.

The content of the magnesium-based detergent in the lubricating oil composition is preferably 100 mass ppm or more, more preferably 200 mass ppm or more, further preferably 300 mass ppm or more, and further preferably 1000 mass ppm or less, more preferably 900 mass ppm or less, further preferably 800 mass ppm or less in terms of magnesium based on the total amount of the lubricating oil composition. When the content of the magnesium-based detergent is within the above numerical range, the high-temperature detergency can be further improved while maintaining the scorch resistance and the LSPI suppression ability.

[ (D) viscosity index improver ]

Examples of the viscosity index improver include a styrene-diene copolymer and an ethylene- α -olefin copolymer, and a styrene-diene copolymer is preferably used. In addition, these viscosity index improvers can be used alone or in combination of 2 or more. By using these viscosity index improvers, the scorch resistance can be improved while maintaining the LSPI inhibiting ability and the high-temperature detergency.

The styrene-diene copolymer comprises 1 or 2 or more styrene monomers selected from styrene and a hydrogenated product thereof and 1 or 2 or more diene monomers selected from a diene and a hydrogenated product thereof as monomer units. Examples of the diene include butadiene and isoprene.

The styrene monomer unit content in the styrene-diene copolymer may be, for example, 1 to 30 mol% or 5 to 20 mol% based on the total monomer unit amount. The diene monomer unit content in the styrene-diene copolymer may be, for example, 70 to 99 mol% or 80 to 95 mol% based on the total monomer units

The ethylene-alpha-olefin copolymer contains ethylene and an alpha-olefin having 3 or more carbon atoms as monomer units. Examples of the α -olefin having 3 or more carbon atoms include propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, and 1-decene, and propylene is preferable.

The ethylene unit content in the ethylene- α -olefin copolymer may be, for example, 30 to 80 mol%, 35 to 75 mol%, or 40 to 70 mol% based on the total amount of the monomer units. The content of the α -olefin unit in the ethylene- α -olefin copolymer may be, for example, 20 to 70 mol%, 25 to 65 mol%, or 30 to 60 mol% based on the total amount of the monomer units.

The lubricating oil composition preferably does not comprise poly (meth) acrylates as viscosity index improvers. The scorch resistance can be further improved by the lubricating oil composition not containing a poly (meth) acrylate.

The PSSI (permanent shear stability index) of the diesel injector method using the viscosity index improver is preferably 40 or less, more preferably 35 or less, further preferably 30 or less, and usually more than 0. When the PSSI is within the above numerical range, the shear stability can be maintained, the fuel economy is good, and the kinematic viscosity and HTHS viscosity after use are maintained at a constant level or higher. In the present specification, "PSSI" refers to a Permanent Shear Stability Index (Permanent Shear Stability Index) of a Polymer calculated according to ASTM D6022-01 (Standard Practice for measuring Permanent Shear Stability Index) based on data measured by ASTM D6278-02 (Test Method for measuring Shear Stability of Polymer containment Fluids Using a European Diesel Fuel Injector Apparatus, Test Method for Shear Stability of fluid-Containing polymers).

The weight average molecular weight (Mw) of the viscosity index improver is, for example, preferably 10000 or more, more preferably 50000 or more, further preferably 100000 or more, further more preferably 200000 or more, and further preferably 1000000 or less, more preferably 700000 or less, further preferably 500000 or less. If the weight average molecular weight of the viscosity index improver is within the above numerical range, a sufficient viscosity index improving effect can be obtained, and excellent fuel economy is obtained, and further, an appropriate viscosity increasing effect, shear stability, solubility in a lubricant base oil, and storage stability are excellent.

The content of the viscosity index improver is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, further preferably 1.0% by mass or more, and further preferably 20.0% by mass or less, more preferably 15.0% by mass or less, further preferably 10.0% by mass or less, based on the total amount of the lubricating oil composition. When the content of the viscosity index improver is within the above numerical range, the scorch resistance can be further improved while the viscosity-temperature characteristics are excellent.

[ (E) Nitrogen-containing dispersant ]

The nitrogen-containing dispersant (hereinafter, sometimes referred to as "component (E)") is not particularly limited, and for example, 1 or more compounds selected from the following (E-1) to (E-3) may be used.

(E-1) a succinimide having at least one alkyl group or alkenyl group in the molecule or a derivative thereof (hereinafter, sometimes referred to as "component (E-1)"),

(E-2) benzylamine having at least one alkyl group or alkenyl group in the molecule or derivative thereof (hereinafter, sometimes referred to as "component (E-2)"),

(E-3) a polyamine having at least one alkyl group or alkenyl group in the molecule or a derivative thereof (hereinafter, may be referred to as "component (E-3)").

As the component (E), the component (E-1) can be particularly preferably used.

In the component (E-1), examples of the succinimide having at least one alkyl group or alkenyl group in the molecule thereof include compounds represented by the following formula (5) or (6).

In the formula (5), R ⁵ Represents an alkyl group or alkenyl group having 40 to 400 carbon atoms, and h represents an integer of 1 to 5, preferably 2 to 4. R ⁵ The number of carbon atoms of (b) is preferably 60 or more, and preferably 350 or less.

In the formula (6), R ⁶ And R ⁷ Each independently represents an alkyl group or an alkenyl group having 40 to 400 carbon atoms, or a combination of different groups. R ⁶ And R ⁷ Particularly preferred is a polybutenyl group. In addition, i represents an integer of 0 to 4, preferably 1 to 3. R is ⁶ And R ⁷ The number of carbon atoms of (b) is preferably 60 or more, and preferably 350 or less.

By R in the formulae (5) and (6) ⁵ ～R ⁷ The number of carbon atoms of (b) is not less than the above lower limit, and good solubility in the lubricant base oil can be obtained. On the other hand, by R ⁵ ～R ⁷ The number of carbon atoms of (b) is not more than the above upper limit, and the low temperature fluidity of the lubricating oil composition can be improved.

Alkyl or alkenyl (R) in the formula (5) and formula (6) ⁵ ～R ⁷ ) The alkyl group may be linear or branched, and preferable examples thereof include a branched alkyl group and a branched alkenyl group derived from an oligomer of an olefin such as propylene, 1-butene, or isobutylene, or a cooligomer of ethylene and propylene. Among them, a branched alkyl group or alkenyl group derived from an oligomer of isobutylene conventionally called polyisobutylene, or a polybutenyl group is most preferable.

Alkyl or alkenyl (R) in the formula (5) and formula (6) ⁵ ～R ⁷ ) The number average molecular weight of (2) is preferably 800 to 3500.

The succinimide having at least one alkyl group or alkenyl group in the molecule includes a so-called mono-type succinimide represented by formula (5) obtained by adding succinic anhydride to only one end of a polyamine chain, and a so-called di-type succinimide represented by formula (6) obtained by adding succinic anhydride to both ends of a polyamine chain. In the lubricating oil composition of the present invention, either one of the mono-type succinimide and the di-type succinimide may be contained, or both of them may be contained as a mixture.

The method for producing the succinimide having at least one alkyl group or alkenyl group in the molecule is not particularly limited, and for example, the succinimide can be produced by reacting a compound having an alkyl group or alkenyl group having 40 to 400 carbon atoms with maleic anhydride at 100 to 200 ℃ to obtain alkyl succinic acid or alkenyl succinic acid, and reacting the obtained alkyl succinic acid or alkenyl succinic acid with a polyamine. Examples of the polyamine include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine.

In the component (E-2), as benzylamine having at least one alkyl group or alkenyl group in the molecule, a compound represented by the following formula (7) can be exemplified.

In the formula (7), R ⁸ Represents an alkyl group or alkenyl group having 40 to 400 carbon atoms, and j represents an integer of 1 to 5, preferably 2 to 4. R is ⁸ The number of carbon atoms of (b) is preferably 60 or more, and more preferably 350 or less.

The method for producing the component (E-2) is not particularly limited. For example, there is a method of reacting a polyolefin such as a propylene oligomer, polybutene, or an ethylene- α -olefin copolymer with phenol to prepare an alkylphenol, and then reacting the alkylphenol with formaldehyde and a polyamine such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine by a mannich reaction.

In the component (E-3), as the polyamine having at least one alkyl group or alkenyl group in the molecule, a compound represented by the following formula (8) can be exemplified.

R ⁹ -NH-(CH ₂ CH ₂ NH) _k -H (8)

In the formula (8), R ⁹ Represents an alkyl group having 40 to 400 carbon atoms or lessOr an alkenyl group, k represents an integer of 1 to 5, preferably 2 to 4. R ⁹ The number of carbon atoms of (b) is preferably 60 or more, and more preferably 350 or less.

The method for producing the component (E-3) is not particularly limited. For example, a method of chlorinating a polyolefin such as a propylene oligomer, polybutene, or an ethylene- α -olefin copolymer, and then reacting the chlorinated polyolefin with a polyamine such as ammonia, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, or pentaethylenehexamine is exemplified.

Examples of the derivatives of the components (E-1) to (E-3) include (i) modified compounds based on oxygen-containing organic compounds obtained by reacting a monocarboxylic acid having 1 to 30 carbon atoms such as a fatty acid, a polycarboxylic acid having 2 to 30 carbon atoms (e.g., oxalic acid, phthalic acid, trimellitic acid, pyromellitic acid, etc.), an acid anhydride or ester compound thereof, an epoxide having 2 to 6 carbon atoms, or a hydroxy (poly) oxyalkylene carbonate with the above succinimide, benzylamine, or polyamine having at least one alkyl group or alkenyl group in the molecule (hereinafter referred to as "the above-mentioned nitrogen-containing compounds"), thereby neutralizing or amidating a part or all of the remaining amino groups and/or imino groups; (ii) a boron-modified compound obtained by reacting boric acid with the nitrogen-containing compound to neutralize or amidate a part or all of the remaining amino groups and/or imino groups; (iii) a phosphoric acid-modified compound obtained by reacting phosphoric acid with the nitrogen-containing compound to neutralize or amidate a part or all of the remaining amino groups and/or imino groups; (iv) a sulfur-modified compound obtained by allowing a sulfur compound to act on the nitrogen-containing compound; and (v) a modified compound obtained by combining 2 or more modifications selected from the group consisting of modifications based on an oxygen-containing organic compound, boron modifications, phosphoric acid modifications, and sulfur modifications and applying to the above-described nitrogen-containing compound.

(E) The molecular weight of the component (E-1) is not particularly limited, and the weight average molecular weight is preferably 1000 to 20000, more preferably 2000 to 10000.

The content of the component (E) is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, further preferably 1.0% by mass or more, and further preferably 10% by mass or less, more preferably 7% by mass or less, further preferably 5% by mass or less, based on the total amount of the lubricating oil composition. When the content of the component (E) is not less than the lower limit, the coking resistance of the lubricating oil composition can be sufficiently improved. Further, when the content of the component (E) is not more than the above upper limit, fuel economy can be improved.

[ (F) ashless friction modifier ]

The ashless friction modifier is not particularly limited, and a compound generally used as a friction modifier for lubricating oil can be used. Examples of the ashless friction modifier include compounds having 6 to 50 carbon atoms containing 1 or more hetero elements selected from an oxygen atom, a nitrogen atom and a sulfur atom in the molecule. More specifically, there may be mentioned ashless friction modifiers such as amine compounds having at least one alkyl or alkenyl group having 6 to 30 carbon atoms, particularly a straight-chain alkyl group, straight-chain alkenyl group, branched-chain alkyl group or branched-chain alkenyl group having 6 to 30 carbon atoms in the molecule, fatty acid esters, fatty acid amides, fatty acids, fatty alcohols, fatty ethers, urea compounds, hydrazide compounds, and the like.

The content of the ashless friction modifier is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, further preferably 0.2% by mass or more, and further preferably 2% by mass or less, more preferably 1% by mass or less, further preferably 0.8% by mass or less, based on the total amount of the lubricating oil composition. If the content of the ashless friction modifier is within the above numerical range, the friction reducing effect can be improved, and the solubility of the additive can be maintained without impairing the effects of the antiwear agent and the like.

[ (G) molybdenum-containing Compound ]

As the molybdenum-containing compound (hereinafter sometimes referred to as "component (G)"), for example, (G1) molybdenum dithiocarbamate (sulfurized molybdenum dithiocarbamate or sulfurized molybdenum oxide dithiocarbamate; hereinafter sometimes referred to as "component (G1)") can be used. In particular, as the component (G1), a compound represented by the following formula (9) can be used.

In the above general formula (9), R ¹⁰ ～R ¹³ The alkyl groups may be the same or different and each have 2 to 24 carbon atoms or 6 to 24 carbon atoms, preferably 4 to 13 carbon atoms or 10 to 15 carbon atoms. The alkyl group may be any of a primary alkyl group, a secondary alkyl group, and a tertiary alkyl group, and may be linear or branched. It should be noted that "(alkyl) aryl" means "aryl or alkylaryl". In the alkylaryl group, the substitution position of the alkyl group in the aromatic ring is arbitrary. Y is ¹ ～Y ⁴ Each independently being a sulfur atom or an oxygen atom, Y ¹ ～Y ⁴ At least one of which is a sulfur atom.

Examples of the molybdenum-containing compound other than the component (G1) include molybdenum dithiophosphate; a complex of a molybdenum compound (for example, molybdic acid such as molybdenum oxide such as molybdenum dioxide and molybdenum trioxide, molybdic acid such as orthomolybdic acid, paramolybdic acid, and (poly) molybdic sulfide, metal salts and ammonium salts of these molybdic acids, molybdenum sulfide such as molybdenum disulfide, molybdenum trisulfide, molybdenum pentasulfide, and molybdenum polysulfide, molybdic sulfide, metal salts or amine salts of molybdic sulfide, and molybdenum halide such as molybdenum chloride) with a sulfur-containing organic compound (for example, alkyl (thio) xanthate, thiadiazole, mercaptothiadiazole, thiocarbonate, tetraalkylthiuram disulfide, bis (di (thio) hydrocarbyl dithiophosphonate) disulfide, organic (poly) sulfide, sulfide ester, and the like), or another organic compound; and sulfur-containing molybdenum compounds such as complexes of sulfur-containing molybdenum compounds such as molybdenum sulfide and molybdic acid sulfide and alkenylsuccinimide. The molybdenum-containing compound may be a mononuclear molybdenum compound, or a polynuclear molybdenum compound such as a dinuclear molybdenum compound or a trinuclear molybdenum compound.

As the molybdenum-containing compound other than the (G1) component, a molybdenum-containing compound containing no sulfur as a constituent element may be used. Specific examples of the molybdenum-containing compound containing no sulfur as a constituent element include a molybdenum-amine complex, a molybdenum-succinimide complex, a molybdenum salt of an organic acid, and a molybdenum salt of an alcohol, and among them, a molybdenum-amine complex, a molybdenum salt of an organic acid, and a molybdenum salt of an alcohol are preferable.

The content of the component (G) is preferably 10mass ppm or more, preferably 100 mass ppm or more, and further preferably 2000 mass ppm or less, more preferably 1000 mass ppm or less, and further preferably 500 mass ppm or less in terms of molybdenum amount based on the total amount of the lubricating oil composition. If the content of the component (G) is within the above numerical range, the friction reducing effect can be improved and the LSPI suppressing ability can be further improved.

[ (H) antiwear agent ]

The antiwear agent is not particularly limited, and a compound generally used as an antiwear agent for lubricating oil can be used. As the anti-wear agent, for example, a sulfur-based, phosphorus-based, sulfur-phosphorus-based anti-wear agent, or the like can be used. Specifically, examples of the anti-wear agent include phosphites, thiophosphites, dithiophosphates, trithiophosphites, phosphates, thiophosphates, dithiophosphates, trithiophosphates, amine salts thereof, metal salts thereof, derivatives thereof, dithiocarbamates, zinc dithiocarbamates, disulfide ethers, polysulfide, olefin sulfides, and oil and fat sulfides.

Among these anti-wear agents, a phosphorus-based anti-wear agent is preferable, and zinc dialkyldithiophosphate (ZnDTP) represented by the following formula (10) is particularly preferable.

In the formula (10), R ¹⁴ ～R ¹⁷ Each independently represents a linear or branched alkyl group having 1 to 24 carbon atoms, and may be a combination of different groups. In addition, R ¹⁴ ～R ¹⁷ The number of carbon atoms of (b) is preferably 3 or more, more preferably 12 or less, and still more preferably 8 or less. In addition, R ¹⁴ ～R ¹⁷ The alkyl group may be any of a primary alkyl group, a secondary alkyl group and a tertiary alkyl group, preferably a primary alkyl group, a secondary alkyl group or a combination thereof, and more preferably a molar ratio of the primary alkyl group to the secondary alkyl group (primary alkyl group: secondary alkyl group) is 0: 100-30: 70. the ratio may be a combination ratio of alkyl chains within the molecule, or a mixture ratio of ZnDTP having only primary alkyl groups to ZnDTP having only secondary alkyl groups. The fuel economy can be improved by the use of a secondary alkyl group as the main component.

The method for producing the zinc dialkyldithiophosphate is not particularly limited. For example, by reacting a compound having a group with R ¹⁴ ～R ¹⁷ The corresponding alkyl alcohol reacts with phosphorus pentasulfide to synthesize dithiophosphoric acid, which is then neutralized with zinc oxide.

The content of the antiwear agent is preferably 0.1 mass% or more, more preferably 0.5 mass% or more, and further preferably 5.0 mass% or less, more preferably 3.0 mass% or less, based on the total amount of the lubricating oil composition. If the content of the anti-wear agent is within the above numerical range, a sufficient anti-wear effect can be obtained.

[ (I) antioxidant ]

The antioxidant is not particularly limited, and a compound generally used as an antioxidant for lubricating oil can be used. Examples of the antioxidant include amine-based antioxidants and phenol-based antioxidants, and amine-based antioxidants are preferred. As the amine-based antioxidant, for example, known amine-based antioxidants such as alkylated diphenylamine, alkylated phenyl- α -naphthylamine, and phenyl- β -naphthylamine can be used. As the phenolic antioxidant, for example, known phenolic antioxidants such as 2, 6-di-tert-butyl-4-methylphenol (DBPC) and 4, 4' -methylenebis (2, 6-di-tert-butylphenol) can be used.

The content of the antioxidant is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and further preferably 5% by mass or less, more preferably 3% by mass or less, based on the total amount of the lubricating oil composition. If the content of the antioxidant is within the above numerical range, a sufficient antioxidant effect can be obtained.

[ other ingredients ]

The lubricating oil composition may contain, in addition to the components (a) to (I), other components commonly used in lubricating oil compositions, such as rust inhibitors, pour point depressants, anti-emulsifiers, metal deactivators, and anti-foaming agents.

Examples of the rust inhibitor include petroleum sulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenyl succinate, and polyol ester. The content of the rust inhibitor is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, and further preferably 10 mass% or less, more preferably 5 mass% or less, based on the total amount of the lubricating oil composition.

As the pour point depressant, for example, a polymethacrylate-based polymer suitable for a lubricant base oil to be used, or the like can be used. The content of the pour point depressant is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, and further preferably 10 mass% or less, more preferably 5 mass% or less, based on the total amount of the lubricating oil composition.

Examples of the anti-emulsifier include polyalkylene glycol-based nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and polyoxyethylene alkyl naphthyl ethers. The content of the anti-emulsifier is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and further preferably 10% by mass or less, more preferably 5% by mass or less, based on the total amount of the lubricating oil composition.

Examples of the metal inactivator include imidazoline, pyrimidine derivatives, alkylthiadiazoles, mercaptobenzothiazole, benzotriazole or its derivatives, 1, 3, 4-thiadiazole polythioether, 1, 3, 4-thiadiazolyl-2, 5-dialkyldithiocarbamate, 2- (alkyldithio) benzimidazole, and β - (ortho-carboxybenzylthio) propionitrile. The content of the metal deactivator is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, and further preferably 10 mass% or less, more preferably 5 mass% or less, based on the total amount of the lubricating oil composition.

The defoaming agent may have a kinematic viscosity of 1000 to 100000mm at 25 ℃ ² Silicone oil per second, alkenyl succinic acid derivatives, esters of polyhydric aliphatic alcohols with long-chain fatty acids, methyl salicylate, o-hydroxybenzyl alcohol, and the like. The content of the defoaming agent is preferably 0.0 based on the total amount of the lubricating oil composition1 mass% or more, more preferably 0.05 mass% or more, and preferably 10 mass% or less, more preferably 5 mass% or less.

[ physical Properties of lubricating oil composition ]

The kinematic viscosity at 100 ℃ of the lubricating oil composition is preferably 4.0mm ² At least one second, more preferably 5.0mm ² At least one second, and more preferably 5.5mm ² At least one second, and more preferably 6.1mm ² More than one second, and less than 12.5mm ² Second, more preferably less than 11.5mm ² Second, further preferably less than 10.0mm ² Second, even more preferably less than 9.3mm ² In seconds. When the kinematic viscosity at 100 ℃ of the lubricating oil composition is within the above numerical range, the low-temperature viscosity characteristics are good, sufficient fuel economy can be obtained, and oil film formation at the lubricated part is well performed, resulting in excellent lubricity.

The kinematic viscosity at 40 ℃ of the lubricating oil composition is preferably 20.0mm ² At least one second, more preferably 25.0mm ² At least one second, and more preferably 30.0mm ² At least one second, and more preferably 35.0mm ² More than one second, and less than 80.0mm ² Second, more preferably less than 70.0mm ² Second, more preferably less than 60.0mm ² Second, even more preferably less than 55.0mm ² In seconds. When the kinematic viscosity at 40 ℃ of the lubricating oil composition is within the above numerical range, the low-temperature viscosity characteristics are good, sufficient fuel economy can be obtained, and oil film formation at the lubricated part is well performed, resulting in excellent lubricity.

The viscosity index of the lubricating oil composition is preferably 120 or more, more preferably 130 or more, further preferably 140 or more, and may be usually 300 or less. If the viscosity index of the lubricating oil composition is within the above numerical range, fuel economy can be improved while maintaining the viscosity of HTHS at 150 ℃.

The HTHS viscosity at 150 ℃ of the lubricating oil composition is preferably 1.7 mPas or more, more preferably 1.8 mPas or more, further preferably 1.9 mPas or more, further more preferably 2.0 mPas or more, and further preferably 3.5 mPas or less, more preferably 3.2 mPas or less, further preferably 2.9 mPas or less, and further more preferably 2.6 mPas or less. If the HTHS viscosity at 150 ℃ of the lubricating oil composition is within the above numerical range, the lubricating properties and fuel efficiency are good. In the present specification, "HTHS viscosity at 150 ℃" means high-temperature high-shear viscosity at 150 ℃ measured according to ASTM D-4683.

The content of sulfur in the lubricating oil composition is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, and still more preferably 0.3% by mass or less, based on the total amount of the lubricating oil composition. When the sulfur content in the lubricating oil composition is within the above numerical range, thermal oxidation stability can be improved.

The nitrogen content in the lubricating oil composition is 700 mass ppm or more, preferably 800 mass ppm or more, more preferably 900 mass ppm or more, further preferably 1000 mass ppm or more, and further preferably 3000 mass ppm or less, more preferably 2500 mass ppm or less, further preferably 2000 mass ppm or less, based on the total amount of the lubricating oil composition. If the nitrogen content in the lubricating oil composition is within the above numerical range, the fuel economy can be improved while maintaining the coking resistance.

The evaporation loss amount of the lubricating oil composition is preferably 15% by mass or less, more preferably 14% by mass or less, further preferably 13% by mass or less, and particularly preferably 12% by mass or less, based on the NOACK evaporation amount. By setting the NOACK evaporation amount of the lubricating oil composition to the upper limit value or less, the evaporation loss of the lubricating oil can be suppressed to a small level, and an increase in viscosity or the like can be suppressed. The NOACK evaporation amount referred to herein is a value measured on the evaporation amount of the lubricating oil measured in accordance with ASTM D5800.

Examples

The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[ preparation of lubricating oil composition ]

The lubricating oil compositions of the present invention (examples 1 to 10) and the lubricating oil compositions for comparison (comparative examples 1 to 6) were prepared using the lubricating base oils and various additives shown below in the formulations shown in tables 1 and 2, respectively. In tables 1 and 2, "% inmass" represents% by mass based on the total amount of the lubricating oil base oil, "% mass" represents% by mass based on the total amount of the lubricating oil composition, and "massppm" represents ppm by mass based on the total amount of the lubricating oil composition.

[ (A) lubricating base oil ]

A-1: hydrocracking base oil (Group III, Yubase (registered trademark) 4, manufactured by SK Lubricants, density (15 ℃ C.): 0.836, kinematic viscosity (40 ℃ C.): 19.6mm ² Second, kinematic viscosity (100 ℃): 4.2mm ² Second, viscosity index: 122, pour point: -15 ℃, sulfur: less than 10mass ppm,% C _P ：80.7，％C _N ：19.3，％C _A ：0)

The amount of the lubricant base oil is the remainder obtained by subtracting the additives, with the total amount of the lubricant composition being 100 mass%.

[ additives ]

[ (B) calcium-based cleaning agent ]

B-1: overbased calcium salicylate (alkyl chain length 14-18, Ca content: 8.0 mass%, total base number 220mgKOH/g)

[ (C) magnesium-based cleaning agent ]

C-1: overbased magnesium salicylate (alkyl chain length 14-18, Mg content: 7.6 mass%, total base number 340mgKOH/g)

[ (D) viscosity index improver ]

D-1: styrene-diene copolymer-based viscosity index improver (Mw 430000, PSSI 25)

D-2: ethylene-propylene copolymer-based viscosity index improver (Mw 400000, PSSI 24)

D-3: non-dispersible poly (meth) acrylate viscosity index improver (Mw 380000, PSSI 25)

[ (E) Nitrogen-containing dispersant ]

E-1: non-boric acid-modified polybutenyl succinic acid bisimide (Mw 5200, N content: 1.4 mass%)

[ (F) ashless Friction modifier ]

F-1: glycerol monooleate

[ (G) molybdenum-containing Compound ]

G-1: molybdenum amine (Mo content: 10 mass%, N content: 1.2 mass%)

[ (H) antiwear agent ]

H-1: zinc dialkyldithiophosphate (ZnDTP, secondary alkyl type, in the above formula (10), R ¹⁴ ～R ¹⁷ The number of carbon atoms of (a): both 6, Zn content: 9.3 mass%, P content: 8.5 mass%, S content: 18% by mass)

[ (I) antioxidant ]

I-1: diphenylamine

[ physical Properties of lubricating oil composition ]

Various physical properties of the lubricating oil compositions of examples 1 to 10 and comparative examples 1 to 6 were measured as follows. The results are shown in tables 1 and 2.

Kinematic viscosity (40 ℃, 100 ℃): measured according to ASTM D-445.

Viscosity index: measured according to JIS K2283-1993.

HTHS viscosity (150 ℃): measured according to ASTM D-4683.

Content of elements (B, Ca, K, Mg, Mo, Zn, P, Zn) in oil: measured according to JIS K0116-.

The content of sulfur: measured according to JIS K2541-2003.

Content of nitrogen: measured according to JIS K2609-1998.

[ evaluation of Performance of lubricating oil composition ]

The lubricating oil compositions of examples 1 to 10 and comparative examples 1 to 6 were subjected to the following performance evaluations. The evaluation results are shown in tables 3 and 4.

[ evaluation of coking resistance ]

(coking test panel)

The lubricating oil compositions were subjected to panel coking testing. The details of the test method are described below.

300mL of the lubricating oil composition was placed in a test container equipped with a splash guard, and an aluminum panel was attached. The sample oil and the face plate were heated to an oil temperature of 100 ℃ and a face plate temperature of 300 ℃. The splash was rotated at 1000rpm at the time the conditioned temperature was reached to splash the oil onto the panel. The sputtering was performed for a period of 15 seconds followed by 45 seconds of rest. After 3 hours, the mass (mg) of carbon or the like attached to the aluminum panel was measured.

As a result, the lower the value, the better the scorch resistance.

[ evaluation of inhibitory Activity of LSPI ]

To evaluate LSPI inhibition capacity, LSPI frequency index of the lubricating oil composition was calculated. This is a regression formula represented by the following formula (11) reported in SAE Paper 2014-01-2785.

LSPI frequency index 6.59 XCA-26.6 XP-5.12 XMO +1.69 (11)

(in the formula (11), Ca represents the calcium content (mass%) in the composition, P represents the phosphorus content (mass%) in the composition, and Mo represents the molybdenum content (mass%) in the composition.)

As a result, the lower the LSPI frequency index, the better the LSPI suppression ability.

[ evaluation of high-temperature detergency ]

(Heat pipe test)

Heat pipe tests were conducted on the lubricating oil compositions according to JPI-5S-55-99. The details of the test method are described below.

In a glass tube having an inner diameter of 2mm, the lubricating oil composition was allowed to continuously flow at 0.3 ml/hr and air at 10 ml/sec for 16 hours while keeping the temperature of the glass tube at 280 ℃. The paint adhered to the glass tube was compared with the color sample, and the case of transparency was rated at 10 points, and the case of black was rated at 0 points.

A higher score indicates better high temperature cleaning. When the score is 7.0 or more, the high-temperature cleaning property is good.

[ Table 4]

The lubricating oil compositions of examples 1 to 10 exhibited good results in terms of scorch resistance, LSPI inhibition ability, and high-temperature detergency.

On the other hand, the lubricating oil compositions of comparative examples 1 and 2, in which the same poly (meth) acrylate-based viscosity index improver as that of the conventional engine oil was used as the viscosity index improver, exhibited poor scorch resistance.

The lubricating oil composition of comparative example 3 having an excessively large calcium content was poor in LSPI inhibitory ability.

The lubricating oil composition of comparative example 4 containing too little calcium, the lubricating oil composition of comparative example 5 containing no magnesium, and the lubricating oil composition of comparative example 6 containing too little nitrogen were inferior in high-temperature detergency.

Claims

1. A lubricating oil composition for an engine with a supercharger, comprising:

(A) a lubricant base oil,

(B) a calcium-based detergent containing calcium in an amount of 1100-1900 ppm by mass based on the total amount of the lubricating oil composition,

(C) a magnesium-based cleaning agent which is capable of removing magnesium,

(E) a nitrogen-containing dispersant;

the nitrogen content is 1000 ppm by mass or more based on the total amount of the lubricating oil composition.

2. The lubricating oil composition according to claim 1, wherein the (B) calcium-based detergent is calcium salicylate.

3. The lubricating oil composition according to claim 1 or 2, wherein the (C) magnesium-based detergent is magnesium salicylate.

4. The lubricating oil composition according to claim 1 or 2, wherein the content of the (C) magnesium-based detergent is 100 mass ppm or more and 1000 mass ppm or less in terms of magnesium based on the total amount of the lubricating oil composition.

5. The lubricating oil composition according to claim 1 or 2, wherein the (D) viscosity index improver is a styrene-diene copolymer.

6. The lubricating oil composition according to claim 1 or 2, wherein the content of the (D) viscosity index improver is 0.1 to 20% by mass, based on the total amount of the lubricating oil composition.

7. The lubricating oil composition according to claim 1 or 2, further comprising (F) an ashless friction modifier.

8. The lubricating oil composition according to claim 1 or 2, further comprising (G) a molybdenum-containing compound.

9. The lubricating oil composition according to claim 1 or 2, further comprising zinc alkyl phosphate as (H) an antiwear agent.

10. Lubricating oil composition according to claim 1 or 2, wherein the kinematic viscosity at 100 ℃ is 4.0mm ² More than second and less than 12.5mm ² In seconds.

11. Lubricating oil composition according to claim 1 or 2, wherein the HTHS viscosity at 150 ℃ is 1.7 mPa-s or more and less than 3.5 mPa-s.

12. Lubricating oil composition according to claim 1 or 2, comprising no poly (meth) acrylate as viscosity index improver.

13. Lubricating oil composition according to claim 1 or 2, wherein the composition is used for both gasoline and diesel engines.

14. The lubricating oil composition according to claim 1 or 2, which is for a diesel engine.