JP6895861B2 - Lubricating oil composition for internal combustion engine - Google Patents

Description

The present invention relates to a lubricating oil composition for an internal combustion engine. In particular, it relates to a lubricating oil composition for an automobile engine (particularly a diesel engine). More specifically, the present invention relates to a lubricating oil composition for an internal combustion engine, which is excellent in fuel efficiency, oil consumption suppression, and cleanliness.

The problem with crankcase lubricating oil is that the so-called blow-by gas makes it easier for the lubricating oil to escape from the crankcase. Blow-by gas, or such a gas / lubricating oil mixture, is preferably recirculated to the engine rather than discharged to the atmosphere. In some engines, such recirculation is performed by injecting blow-by gas into the engine's air intake system so that the lubricating oil burns in the piston chamber. While blow-by gas recirculation solves the problem of emissions, it can also cause problems such as the formation of deposits in the air intake system. For example, if deposits form on an air compressor, such a compressor will not work well and will be vulnerable to damage. Also, for example, if there is an air cooler between the compressor and the cylinder block-crankcase, the air cooler may be contaminated. It has been desired to provide a diesel engine system that prevents or further reduces the formation of such deposits. (Patent Document 1)

On the other hand, low fuel consumption performance is required. In order to achieve low fuel consumption performance, use a friction modifier that contributes to friction reduction performance, reduce stirring resistance, have low viscosity at low temperatures, and improve the viscosity index to secure an oil film at high temperatures. It has been studied to prepare a composition having appropriate viscosity characteristics by using an agent. (Patent Document 2)

Japanese Patent No. 5501620 Japanese Unexamined Patent Publication No. 2014-210844 Japanese Unexamined Patent Publication No. 2017-1197887

However, it has not been sufficiently satisfactory to suppress the formation of deposits, show fuel-saving performance, and maintain the performance for a long period of time. In addition, it is expected that downsizing and high supercharging will continue to increase in commercial vehicles equipped with diesel engines in the future, and the heat load on engine oil is expected to increase. , There were problems such as not being able to obtain excellent evaporability.

As a result of diligent research by the present inventors, it has been found that the above problem can be solved by blending a GTL base oil and a comb-shaped polymethacrylate viscosity index improver, and this has already been filed (Patent Documents). 3).

The present invention is a further improvement of the invention according to Patent Document 3, and has a higher viscosity index and oil film retention that can cope with the ever-increasing downsizing and high supercharging, and lubrication for internal combustion engines that is also excellent in high-temperature cleanliness. It is an object of the present invention to provide an oil composition.

As a result of diligent research by the present inventors, it is possible to solve the above-mentioned problems by making specific adjustments to the base oil composition in the composition containing the GTL base oil and the comb-shaped polymethacrylate viscosity index improver. And completed the present invention.

That is, the present invention
A base oil composition containing GTL base oil as a main component, having a% Cn of 14 to 25% and an aniline point of 120 to 126 ° C.
A comb-shaped polymethacrylate-based viscosity index improver having a weight average molecular weight (Mw) of 400,000 or more,
A lubricating oil composition for an internal combustion engine containing
The present invention relates to a lubricating oil composition for an internal combustion engine in which the sulfur content of the lubricating oil composition is 0.3% by mass or less based on the total weight of the lubricating oil composition.

The kinematic viscosity of the base oil composition at 100 ° C. ^{may be 3.5 to 8 mm 2} / s.

The lubricating oil composition may have a SAE viscosity grade of 0W-20 or 5W-20 and a viscosity index of 180 or higher, or a SAE viscosity grade of 5W-30 and a viscosity index of 220 or higher.

The viscosity index of the base oil composition may be 120 or more.

According to the present invention, it is possible to provide a lubricating oil composition for an internal combustion engine (particularly an automobile engine) having excellent oil film retention, engine cleaning performance and fuel saving performance. Become.

Hereinafter, the components (components), composition (contents of components), and properties of the lubricating oil composition for an internal combustion engine of the present invention will be described in detail, but the present invention is not limited thereto.

≪Ingredients≫
The lubricating oil composition of the present invention contains a base oil composition containing a GTL base oil, a comb-shaped PMA-based viscosity index improver, and, if necessary, other components.

(Base oil composition)
In the present invention, a base oil composition containing only GTL base oil or a mixed base oil composition containing GTL base oil as a main component is used as the base oil.
Here, "the base oil composition contains GTL base oil as a main component" means that the content of GTL base oil in the total amount of the base oil composition is 50% by mass or more, 60% by mass or more, 70% by mass or more, 80. It means that it is mass% or more or 90 mass% or more. The upper limit is not particularly limited and is 100% by mass or less.

The kinematic viscosity of the base oil composition according to the present invention at 100 ° C. is not particularly limited, but is preferably ^{3.5 to 8.0 mm 2 / s.} More specifically, 3.5 mm ² / s or more, 4.0 mm ² / s or more, 4.5 mm ² / s or more, 5.0 mm ² / s or more, 5.5 mm ² / s or more, 6.0 mm ² / s More than or equal to or 6.5 mm ² / s or more is preferable. On the other hand, 8.0 mm ² / s or less, 7.5 mm ² / s or less, 7.0 mm ² / s or less or 6.5 mm ² / s or less is preferable. Good oil film retention can be obtained by setting the kinematic viscosity of the base oil composition at 100 ° C. to the above lower limit or more. Further, good fuel efficiency can be obtained by setting the kinematic viscosity of the base oil composition at 100 ° C. to the above upper limit or less.

The kinematic viscosity at 40 ° C. and the kinematic viscosity and viscosity index at 100 ° C. in the present invention are the kinematic viscosity at 40 ° C. and the kinematic viscosity and viscosity index at 100 ° C. measured according to JIS K 2283-1993, respectively. Means.

The% Cn of the base oil composition according to the present invention is 14 to 25. More specifically, 14 or more, 15 or more, or 16 or more is preferable. On the other hand, 25 or less, 24 or less, 23 or less, 22 or less or 21 or less are preferable.
By setting% Cn of the base oil composition within the above range, it is possible to obtain a lubricating oil composition having a good viscosity index, oil film retention and seal compatibility by blending the comb-shaped PMA. If the% Cn of the base oil composition is less than the lower limit, not only a good viscosity index cannot be obtained, but also the viscosity of the lubricating oil composition under high pressure may become excessively low, which is not preferable. On the other hand, if% Cn of the base oil composition exceeds the upper limit value, not only a good viscosity index cannot be obtained, but also the seal compatibility of the lubricating oil composition may be deteriorated, which is not preferable.

There is no particular limitation on% Ca of the base oil composition according to the present invention. However, from the viewpoint of oxidative stability, 10 or less, 5 or less, 3 or less, 2 or less, 1 or less, 0.5 or less, 0.3 or less, 0.1 or less, or substantially 0 is preferable.
In the present invention, "substantially 0" means not only exactly zero but also a case where only a trace amount below the measurement limit is contained.

The% Cp of the base oil composition according to the present invention is not particularly limited, and is the balance of% Cn and% Ca described above. Specifically,% Cp is 86 or less, 85 or less, or 80 or less. On the other hand,% Cp is 65 or more, 70 or more or 75 or more.

In the present invention,% Cn,% Ca, and% Cp are the percentage of the total number of naphthen carbons and the number of aromatic carbons, which are obtained by a method (nd-M ring analysis) based on ASTM D 3238-85, respectively. Means the percentage of the total carbon number of, and the percentage of the paraffin carbon number to the total carbon number.

The aniline point of the base oil composition according to the present invention is 120 to 126 ° C. The aniline point in the present invention is measured by a method based on ASTM D611 and JIS K2256.

There is no particular limitation on the viscosity index of the base oil composition according to the present invention. However, it is preferable to have a high viscosity index because there is a social demand for low viscosity at low temperatures for fuel efficiency. Therefore, the viscosity index of the base oil composition is preferably 110 or more, 115 or more, 120 or more, or 125 or more. The upper limit is not particularly limited, but is usually 200 or less.

The sulfur content of the base oil composition according to the present invention is not particularly limited. However, if the base oil composition has a high sulfur content, it may adversely affect the high-temperature cleanliness, oxidation stability and thermal stability of the lubricating oil composition. It is preferably 0.5% by mass or less, 0.3% by mass or less, 0.2% by mass or less, 0.1% by mass or less, or substantially 0% by mass.
In the present invention, "substantially 0% by mass" means not only exactly zero but also a case where only a trace amount below the measurement limit is contained.

(GTL base oil)
As the base oil of the lubricating oil composition according to the present invention, GTL (Gas to Liquid) oil synthesized by the Fisher Tropush method of the liquid fuel conversion technology of natural gas is used as a main component. By using such a base oil as a main component, in the system of the present invention, it is possible to improve the oxidative stability and reduce the evaporation loss.

When a comb polymer is used, the temporary shear viscosity at 100 ° C. is increased by using the GTL base oil, especially in the system of the present invention, as compared with the mineral oil-based base oil (particularly the group III base oil derived from the mineral oil). It can contribute to the improvement of fuel efficiency by reducing it.

The kinematic viscosity of the GTL base oil in the present invention at 100 ° C. is not particularly limited. Typically, it is 3.5 to 8.0 mm ² / s. If the 100 ° C. kinematic viscosity of the GTL base oil, which is the main component, is within this range, there is an advantage that the 100 ° C. kinematic viscosity of the base oil composition can be easily adjusted to the above range.

Here, in order to kinematic viscosity at 100 ° C. to obtain a GTL base oil is 3.5~8.0mm ² / s, the kinematic viscosity at 100 ° C. is 3.5~8.0mm ² / s single GTL base oil may be used. Alternatively, two or more GTL base oils may be mixed and prepared so that the kinematic viscosity at 100 ° C. is within this range. When prepared from two or more GTL base oils, GTL base oil (a1) having a kinematic viscosity at 100 ° C. of 2.5 to 6.0 mm ² / s and GTL base oil (a1) having a kinematic viscosity at 100 ° C. of 7.0 to 13 mm ² / s. It is preferable to mix the two types of GTL base oil (a2) which is s. If the kinematic viscosity of the low-viscosity base oil component (a1) at 100 ° C. ^{is less than 2.5 mm 2} / s, the amount of evaporation increases and it becomes difficult to maintain the viscosity of the composition for a long period of time. Further, if a high-viscosity base oil component (a2) having a kinematic viscosity at 100 ° C. ^{exceeding 13 mm 2} / s is used, the viscosity at a low temperature of −40 ° C. becomes high and the startability at a low temperature becomes poor. Further, in this case, the viscosity index of the mixed GTL base oil is preferably 120 to 180, and more preferably 120 to 150.

These GTL base oils usually have a total sulfur content of less than 10 mass ppm, more preferably a total nitrogen content of less than 1 mass ppm. An example of such a GTL base oil product is SHELL XHVI®.

(Base oil other than GTL base oil)
As long as the above-mentioned properties are satisfied, the base oil composition according to the present invention may contain a base oil other than the GTL base oil. Alternatively, it may be adjusted to satisfy the above properties by blending another base oil. As other base oils, either mineral oils or synthetic oils can be used, and any of groups I to V, which are classified as base oils in API, can be used. A mixture of these can also be used.

In the present invention, it is preferable that the base oil composition contains a base oil belonging to Group II. Group II base oils are mineral oil-based base oils having a saturated hydrocarbon (ASTM D2007) of 90% by volume or more, a sulfur content (ASTM D1552) of 0.03% by mass or less, and a viscosity index (ASTM D2270) of 80 to 120. ..
The group II base oil has a small unsaturated carbon content and sulfur content, has sufficient oxidative stability and cleanliness, and has a certain percentage of Cn. By blending the base oil of Group II,% Cn of the base oil composition can be easily adjusted within the above range without impairing the properties of the lubricating oil composition.

That is, in the present invention, a base oil composition containing or consisting of a GTL base oil and a base oil belonging to Group II in the API classification and satisfying the above-mentioned properties is used. Is preferable. In other words, the group II base oil is blended with the GTL base oil so that the% Cn of the base oil composition is within the above range (particularly, the above lower limit value so that the% Cn of the base oil composition is within the above range). It is preferable to use a base oil composition obtained by blending a Group II base oil having the above% Cn with a GTL base oil having a% Cn less than the above lower limit value).

When the base oil composition contains a GTL base oil and a group II base oil, the content of the group II base oil is not particularly limited as long as the base oil composition satisfies the above properties. Typically, it is 1% by mass or more, 3% by mass or more, 5% by mass or more, or 10% by mass or more. On the other hand, it is 50% by mass or less, 45% by mass or less, 40% by mass or less, 35 quality 30% by mass or less, 25% by mass or less, or 20% by mass or less.

(Viscosity index improver)
The lubricating oil composition of the present invention contains a comb-shaped polymethacrylate-based viscosity index improver (hereinafter, also referred to as comb-shaped PMA). The comb-shaped polymer represents a polymer having a plurality of extended side chains with respect to the polymer main chain in a comb shape. Among these comb-shaped polymers, the viscosity index improver according to the present invention contains a comb-shaped polymethacrylate-based polymer as a viscosity index improver.
In the present invention, the "viscosity index improver" refers to a polymer having a weight average molecular weight (Mw) of 50,000 or more.

The weight average molecular weight (Mw) is determined by using, for example, Shodex GPC-101 of High Performance Liquid Chromatography manufactured by Showa Denko KK. More specifically, the temperature is 40 ° C., the detector is a differential refractive index detector (RI), the carrier flow rate is THF-1.0 ml / min (Ref 0.3 ml / min), the sample injection volume is 100 μl, and the column is. {KF-G (Shodex) x 1, KF-805L (Shodex x 2)}, and analyze (calculate) the weight average molecular weight (weight average molecular weight in terms of polystyrene) using the range corresponding to the peak molecular weight. can do.

As the comb-shaped polymethacrylate-based viscosity index improver according to the present invention, for example, the polymer described in JP-A-2010-532805 may be appropriately used. Further, the manufacturing method thereof is not particularly limited.

The comb-shaped polymethacrylate-based viscosity index improver according to the present invention preferably has a weight average molecular weight of 400,000 to 600,000, more preferably 400,000 to 500,000, and more preferably 400,000 to 450,000. Is the most suitable.

The PSSI (Permanent Shear Stability Index: Permanent Shear Stability Index) of the comb-shaped polymethacrylate-based viscosity index improver according to the present invention is preferably 10 or less.
The PSSI of a polymer as used in the present invention means a permanent shear stability index of a polymer calculated based on the data measured by ASTM D 6278-02 in accordance with ASTM D 6022-01.

Specific examples of such a comb-shaped polymethacrylate-based viscosity index improver include Viscoplex 3-201 (registered trademark) and Viscoplex 3-220 (registered trademark).

Further, the lubricating oil composition of the present invention may contain a viscosity index improver other than the comb-shaped polymethacrylate-based viscosity index improver. An example of such a viscosity index improver is one or more polymers selected from the group consisting of non-combed PMA (polymethacrylate), OCP (olefin copolymer) and SCP (styrene diene copolymer).

The non-comb PMA (polymethacrylate) -based viscosity index improver is not particularly limited, and known agents can be used. Those having a weight average molecular weight of 100,000 to 400,000 are preferable. Specific examples of such PMAs include those described in Japanese Patent Application Laid-Open No. 2014-125569.

The OCP (olefin copolymer) -based viscosity index improver is not particularly limited, and known ones can be used. Those having a weight average molecular weight of 50,000 to 300,000 are preferable. Specific examples of such OCPs include those described in Japanese Patent Application Laid-Open No. 2014-125569.

The SCP (styrene diene copolymer) -based viscosity index improver is not particularly limited, and known ones can be used. Those having a weight average molecular weight of 200,000 to 1,000,000 are preferable. Specific examples of such an SCP include Infinium (registered trademark), SV150, and the like.

In addition, such a viscosity index improver (a polymer having a weight average molecular weight of 50,000 or more) is generally blended in a liquid medium in a state of being appropriately diluted in order to facilitate handling. Also in the present invention, it may be blended in a diluted state in a liquid medium, and since the amount of the liquid medium is sufficiently small with respect to the base oil composition, the influence of the liquid medium can be ignored. The liquid solvent is not particularly limited, but is typically a carrier oil which is a group II base oil or a group III base oil.

The present invention has found that when the above-mentioned comb-shaped PMA is contained in a GTL base oil-containing base oil composition in which% Cn is within a predetermined range, the viscosity index of the lubricating oil composition is extremely improved. In general, the viscosity index of a base oil composition containing a large amount of naphthene (that is, having a large% Cn) is relatively small. The present inventors have also confirmed that the viscosity index of the base oil composition tends to decrease as the% Cn of the base oil composition increases. Surprisingly, however, the base oil composition having% Cn equal to or higher than the lower limit has a smaller viscosity index than the base oil composition having% Cn less than the lower limit. When the same amount of comb-shaped PMA was added to these, it was found that the viscosity index of the lubricating oil composition was larger for that derived from the former base oil composition. As a result, fuel economy can be improved by blending the same amount of comb-shaped PMA, or fuel economy can be maintained even if the blending amount of comb-shaped PMA is reduced. Reducing the comb-shaped PMA content also leads to suppression of sludge production.

(Other ingredients)
The lubricating oil composition of the present invention may contain components other than those described above depending on the intended use. Other components include, for example, cleaning agents, dispersants, abrasion resistant agents, metal deactivators, antioxidants, antifoaming agents and the like.

(Cleaning agent)
The lubricating oil composition of the present invention may contain a boron-containing cleaning agent as a cleaning agent. The boron-containing cleaning agent is not particularly limited, and examples thereof include boric acid-containing alkaline earth metal salts. More specifically, an alkaline earth metal booxide alkyl salicylate cleaning agent and an alkaline earth metal booxide alkyl toluene sulfonate cleaning agent can be mentioned. Of these, calcium borate alkyl toluene sulfonate is particularly suitable.
As such a boron-containing cleaning agent, a known one may be used (for example, an alkaline earth metal booxide alkyltoluene sulfonate cleaning agent can be produced according to the method described in JP-A-2008-297547. ).

Examples of the cleaning agent other than the boron-containing cleaning agent (boron-free cleaning agent) include a metal-based cleaning agent. Examples of the metal-based cleaning agent include alkaline earth metal sulfonate, alkaline earth metal phenate, alkaline earth metal salicylate, alkaline earth metal naphthenate and the like.
Examples of this alkaline earth metal include calcium and magnesium. These can be used alone or in combination of two or more. Usually, calcium or magnesium sulfonates, phenates and salicylates are preferably used.

Examples of the alkaline earth metal sulfonate include alkaline earth metal salts of alkyl aromatic sulfonic acids having linear or branched alkyl groups having 1 to 30 carbon atoms, preferably 6 to 18 carbon atoms, particularly magnesium salts and calcium salts. Can be mentioned. The production method is arbitrary, but it can be obtained, for example, by sulfonation of the alkyl aromatic compound having an alkyl group.
The alkaline earth metal phenate includes an alkylphenol having a linear or branched alkyl group having 4 to 30 carbon atoms, preferably 6 to 18 carbon atoms, an alkylphenol sulfate, and an alkaline earth metal salt of a Mannich reaction product of the alkylphenol, particularly calcium. Salt is preferably used.
As the alkaline earth salicylate, an alkaline earth metal salt of alkylsartylic acid having a linear or branched alkyl group having 1 to 30 carbon atoms, preferably 6 to 18 carbon atoms, particularly preferably a magnesium salt and / or a calcium salt is used. It is preferably used.
These base values can be arbitrarily selected depending on the type and purpose of the lubricating oil to which the lubricating oil is applied.

(Dispersant)
The lubricating oil composition of the present invention may contain an ashless dispersant or a boron-containing dispersant as the dispersant. The ashless dispersant or boron-containing dispersant is, for example, a dispersant such as polybutenyl succinimide-based, polybutenyl succinimide-based, benzylamine-based, or succinic acid ester-based dispersant, or a boronized product thereof. ..

Polybuteneyl succinate imide is obtained from polybutene obtained by polymerizing high-purity isobutene or a mixture of 1-butene and isobutene with a boron trifluoride catalyst or an aluminum chloride catalyst, and has a vinylidene structure at the end of the polybutene. It usually contains 5 to 100 mol%.
The polyalkylene polyamine chain preferably contains 2 to 5 nitrogen atoms, particularly 3 to 4 nitrogen atoms, from the viewpoint of obtaining an excellent sludge suppressing effect. As the derivative of polybutenyl succinate imide, a borate compound such as boric acid or an oxygen-containing organic compound such as alcohol, aldehyde, ketone, alkylphenol, cyclic carbonate, or organic acid may be added to the polybutenyl succinate imide. It can be used as a so-called modified succinate imide in which a part or all of the remaining amino group and / or imino group is neutralized or amidated by acting.

(Abrasion resistant agent)
Examples of the abrasion resistant agent that imparts abrasion resistance and extreme pressure resistance that can be used in the lubricating oil composition of the present invention include zinc dithiophosphate (ZnDTP). Examples of ZnDTP are generally zinc dialkyl dithiophosphate, zinc diaryl dithiophosphate, zinc arylalkyl dithiophosphate and the like.
These alkyl groups may be linear or branched. For example, the alkyl group of zinc dialkyl dithiophosphate may be a primary or secondary alkyl group having 3 to 22 carbon atoms or a zinc dialkyl dithiophosphate having an alkylaryl group substituted with an alkyl group having 3 to 18 carbon atoms. used.
Specific examples of zinc dialkyl dithiophosphate include zinc dipropyl dithiophosphate, zinc dibutyl dithiophosphate, zinc dipentyl dithiophosphate, zinc dihexyl dithiophosphate, zinc diisopentyl dithiophosphate, zinc diethylhexyl dithiophosphate, zinc dioctyl dithiophosphate, and dioxyl dithiophosphate. Zinc nonyldithiophosphate, zinc didecyldithiophosphate, zinc didodecyldithiophosphate, zinc dipropylphenyldithiophosphate, zinc dipentylphenyldithiophosphate, zinc dipropylmethylphenyldithiophosphate, zinc dinonylphenyldithiophosphate, didodecylphenyldithiophosphate Examples thereof include zinc and zinc didodecylphenyl dithiophosphate.

(Metal deactivator)
Examples of the metal inactivator that can be used in the lubricating oil composition of the present invention include benzotriazole derivatives such as benzotriazole and alkyl-tortriazoles, and benzimidazole derivatives such as benzimidazoles and toluimidazoles. Further, indazole derivatives such as toluindazoles, benzothiazoles, benzothiazole derivatives such as tolzothiazoles and the like are exemplified. Further, benzoxazole derivative, thiadiazole derivative, triazole derivative and the like can be mentioned.

(Antioxidant)
Examples of the antioxidants that can be used in the lubricating oil composition of the present invention include amine-based antioxidants and phenol-based antioxidants.
Examples of amine-based antioxidants include p, p'-dioctyl-diphenylamine (manufactured by Seiko Kagaku Co., Ltd .: non-flex OD-3), p, p'-di-α-methylbenzyl-diphenylamine, and N-p-butylphenyl-. Dialkyl-diphenylamines such as N-p'-octylphenylamine, monoalkyldiphenylamines such as mono-t-butyldiphenylamine and monooctyldiphenylamine, di (2,4-diethylphenyl) amine, di (2-ethyl-4). Bis (dialkylphenyl) amines such as −nonylphenyl) amine, alkylphenyl-1-naphthylamines such as octylphenyl-1-naphthylamine, Nt-dodecylphenyl-1-naphthylamine, 1-naphthylamine, phenyl-1- Aryl-naphthylamines such as naphthylamine, phenyl-2-naphthylamine, N-hexylphenyl-2-naphthylamine, N-octylphenyl-2-naphthylamine, N, N'-diisopropyl-p-phenylenediamine, N, N'-diphenyl Examples thereof include phenylenediamines such as −p-phenylenediamine, phenothiazine (manufactured by Hodoya Chemical Co., Ltd .: Phenothiazine), and phenothiazines such as 3,7-dioctylphenothiazine.
Examples of the phenolic antioxidant include 2-t-butylphenol, 2-t-butyl-4-methylphenol, 2-t-butyl-5-methylphenol, 2,4-di-t-butylphenol, and 2,4-. Dimethyl-6-t-butylphenol, 2-t-butyl-4-methoxyphenol, 3-t-butyl-4-methoxyphenol, 2,5-di-t-butylhydroquinone (Kawaguchi Chemical Co., Ltd .: Antage DBH), 2,6-di-t-butyl such as 2,6-di-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-4-ethylphenol, etc. 2,6-di-t-butyl-4-alkoxy such as -4-alkylphenols, 2,6-di-t-butyl-4-methoxyphenol, 2,6-di-t-butyl-4-ethoxyphenol, etc. There are phenols. In addition, 3,5-di-t-butyl-4-hydroxybenzyl mercapto-octyl acetate, n-octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (manufactured by Yoshitomi Pharmaceutical Co., Ltd .: Yoshinox SS), n-dodecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2'-ethylhexyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) ) Propionate, benzenepropanoic acid 3,5-bis (1,1-dimethyl-ethyl) -4-hydroxy-C7 to C9 side chain alkyl ester (manufactured by Ciba Specialty Chemicals: IrganoxL135), etc. 3,5-Di-t-Butyl-4-hydroxyphenyl) propionates, 2,6-di-t-butyl-α-dimethylamino-p-cresol, 2,2'-methylenebis (4-methyl-6-) t-Butylphenol) (manufactured by Kawaguchi Chemical Co., Ltd .: Antage W-400), 2,2'-methylenebis (4-ethyl-6-t-butylphenol) (manufactured by Kawaguchi Chemical Co., Ltd .: Antage W-500), etc. 2,2' -Methylenebis (4-alkyl-6-t-butylphenol) are available. Furthermore, 4,4'-butylidenebis (3-methyl-6-t-butylphenol) (manufactured by Kawaguchi Chemical Co., Ltd .: Antage W-300), 4,4'-methylenebis (2,6-di-t-butylphenol) (shell). -Japan: Ionox220AH), 4,4'-bis (2,6-di-t-butylphenol), 2,2- (di-p-hydroxyphenyl) propane (Shell Japan: bisphenol A), 2,2-bis (3,5-di-t-butyl-4-hydroxyphenyl) propane, 4,4'-cyclohexylidenebis (2,6-t-butylphenol), hexamethylene glycol bis [3- ( 3,5-Di-t-butyl-4-hydroxyphenyl) propionate] (Ciba Specialty Chemicals, Inc .: IrganoxL109), triethylene glycol bis [3- (3-t-butyl-4-hydroxy-5-methyl) Phenyl) propionate] (manufactured by Yoshitomi Pharmaceutical Co., Ltd .: Tominox 917), 2,2'-thio- [diethyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (Ciba Specialty. Chemicals: Irganox L115), 3,9-bis {1,1-dimethyl-2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl} 2,4,8 , 10-Tetraoxaspiro [5,5] Undecane (Sumitomo Chemical: Sumilyzer GA80), 4,4'-thiobis (3-methyl-6-t-butylphenol) (Kawaguchi Chemical Co., Ltd .: Antage RC), 2,2 There are bisphenols such as'-thiobis (4,6-di-t-butyl-resorcin). Then, tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane (manufactured by Ciba Specialty Chemicals: IrganoxL101), 1,1,3-tris (2-methyl). -4-Hydroxy-5-t-butylphenyl) butane (manufactured by Yoshitomi Pharmaceutical Co., Ltd .: Yoshinox 930), 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4) -Hydroxybenzyl) benzene (Shell Japan: Ionox330), bis- [3,3'-bis- (4'-hydroxy-3'-t-butylphenyl) butyric acid] glycol ester, 2- (3) ', 5'-di-t-butyl-4-hydroxyphenyl) Methyl-4- (2 ", 4" -di-t-butyl-3 "-hydroxyphenyl) Methyl-6-t-butylphenol, 2,6 -Bis (2'-hydroxy-3'-t-butyl-5'-methyl-benzyl) -Polyphenols such as 4-methylphenol, condensate of pt-butylphenol and formaldehyde, pt-butylphenol and acetaldehyde Examples thereof include a phenol aldehyde condensate such as a condensate of the above.

(Defoamer)
Examples of the defoaming agent that can be used in the lubricating oil composition of the present invention include organosilicates such as dimethylpolysiloxane, diethylsilicate and fluorosilicone, and non-silicone defoaming agents such as polyalkylacrylate.

≪Composition≫
(Content of base oil composition)
The content of the base oil is preferably 60 to 90% by mass, more preferably 65 to 90% by mass, and 70 to 85% by mass, based on the total mass of the lubricating oil composition. It is more preferable that the range is.

(Content of viscosity index improver)
The content of the viscosity index improver (total content of the viscosity index improver) is not particularly limited and can be changed as appropriate. For example, 0.05 to 20% by mass based on the total mass of the lubricating oil composition. And so on. Hereinafter, the suitable content of each viscosity index improver will be described in detail.

・ Comb-shaped PMA
The content of the comb-shaped PMA is not particularly limited, but is preferably 1.0 to 10% by mass, preferably 1.5 to 9.0% by mass, based on the total mass of the lubricating oil composition. It is more preferable, and more preferably in the range of 2.0 to 8.0% by mass.
In particular, when the SAE viscosity grade of the lubricating oil composition is 0W-20 or 5W-20, 2.0 to 7.0% by mass, 2.0 to 6.0% by mass, 2.0 to 5.0. It is preferably in the range of mass%, 3.0 to 4.0 mass%. On the other hand, when the SAE viscosity grade of the lubricating oil composition is 5W-30, 3.0 to 8.0% by mass, 4.0 to 8.0% by mass, 5.0 to 8.0% by mass, It is preferably in the range of 6.0 to 8.0% by mass.

・ Non-comb-shaped PMA
The content of non-comb PMA is not particularly limited, but the ratio of the non-comb PMA content to the total viscosity index improver content (non-comb PMA content / total viscosity index improver content) is 0.7 or less. Is preferable.

・ OCP
The content of OCP is not particularly limited, but it is preferable that the ratio of the OCP content to the total content of the viscosity index improver (OCP content / the content of the total viscosity index improver) is 0.2 or less. is there.

・ SCP
The content of SCP is not particularly limited, but it is preferable that the ratio of the SCP content to the total content of the viscosity index improver (SCP content / total content of the viscosity index improver) is 0.3 or less. is there.

Viscosity index improvers include non-comb PMA (polymethacrylate), SCP (styrene diene copolymer) and / or OCP (olefin copolymer), and these include at least one (preferably all) of the above ranges. When the condition is satisfied, in the system of the present invention, it is possible to reduce the manufacturing cost while achieving the effect of the present invention.

(Contents of other ingredients)
The suitable content of other components that may be added to the lubricating oil composition of the present invention will be described.

-Boron-containing detergent and boron-containing dispersant The preferable total amount (total) of the boron-containing detergent and the boron-containing dispersant is, for example, a boron-containing conversion value (total value) as a reference for the total amount of the composition. , 0.025% by mass or more. On the other hand, the upper limit is, for example, 0.1% by mass or less and 0.050% by mass or less.

-Metal-based cleaning agent The preferable content of the metal-based cleaning agent is, for example, 0.05 to 0.3% by mass, more preferably 0.05 to 0.3% by mass, based on the total mass of the lubricating oil composition, either alone or in combination. It is 0.1 to 0.2% by mass.

-Ashes-free dispersant The preferable content of the ash-free dispersant is an amount that provides, for example, 0.01 to 0.3% by mass of nitrogen based on the total mass of the lubricating oil composition, either alone or in combination. is there.

-Abrasion resistant agent The suitable content of the abrasion resistant agent (for example, ZnDTP) is, for example, 0.01 to 0.10 mass as the amount of phosphorus (P) based on the total mass of the lubricating oil composition, either alone or in combination. %, More preferably in the range of 0.05 to 0.08% by mass.

-Metal inactivating agent The preferable content of the metal inactivating agent is in the range of 0.01 to 0.5% by mass based on the total mass of the lubricating oil composition, either alone or in combination of two or more.

-Antioxidant The preferable content of the antioxidant is in the range of 0.01 to 2% by mass based on the total mass of the lubricating oil composition, either alone or in combination of two or more.

-Defoaming agent The preferable content of the defoaming agent is, for example, in the range of 0.0001 to 0.01% by mass based on the total mass of the lubricating oil composition, either alone or in combination of two or more.

<< Properties of lubricating oil composition >>
The lubricating oil composition according to the present invention containing the above components in the above composition can naturally satisfy the following properties, or can be easily adjusted to satisfy the following properties.

The sulfur content of the lubricating oil composition is 0.3% by mass or less, 0.28% by mass or less, 0.26% by mass based on the total weight of the lubricating oil composition from the viewpoint of high temperature cleanliness, oxidation stability and thermal stability. % Or less, or 0.25% by mass or less.

The viscosity of the lubricating oil composition is not particularly limited. However, the SAE viscosity grade is preferably adjusted to be compatible with 0W-20, 5W-20 or 5W-30. In order to correspond to the SAE viscosity grade, it is preferable to adjust the kinematic viscosity of the lubricating oil composition at 100 ° C. to be 5.6 mm ² / s or more ^{and less than 12.5 mm 2 / s.}

The viscosity index of the lubricating oil composition is not particularly limited. However, it is preferable to have a high viscosity index because there is a social demand for low viscosity at low temperatures for fuel efficiency. Therefore, the viscosity index of the lubricating oil composition is preferably 180 or more. The upper limit is not particularly limited, but is usually 300 or less. When the SAE viscosity grade is 5W-30, the viscosity index of the lubricating oil composition is preferably 220 or more.

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these examples.

≪Raw materials≫
The raw materials used in this example are as follows. The properties of each base oil are shown in Table 1.

(Base oil)
Base oil-1: XHVI-4RL (GTL oil)
Base oil-2: XHVI-8RL (GTL oil)
Base oil-3: Kixx 150N (Group II base oil)
Base oil-4: Kixx 600N (Group II base oil)
Base oil-5: HVI 60 (Group I base oil)
Base oil-6: HVI 160S (Group I base oil)

(Viscosity index improver)
Viscosity index improver solution: A solution containing a comb-shaped PMA-based viscosity index improver having a weight average molecular weight of 400,000 (comb-shaped PMA concentration 60% by mass)

(Other additives)
Defoamer solution: Solution additive package containing dimethylpolysiloxane with a concentration of 3% by mass: Additive package equivalent to JASO DL-1 in which the sulfated ash content is 0.46% by mass when 11.7% is added.

The base oil is blended at the mass ratio shown in Table 1 below (adjusted so that the kinematic viscosity at 100 ° C. of the base oil composition is about 6.0 mm ² / s) to obtain a base oil composition, and various additives are further added. By blending, the lubricating oil compositions according to Examples 1 to 4 and Comparative Examples 1 to 5 were obtained. The kinematic viscosity, viscosity index,% Cp,% Cn,% Ca, and aniline points of each prepared base oil composition at 100 ° C. are also shown in Table 1.

≪Evaluation≫
Next, the following evaluation tests were conducted on the lubricating oil compositions according to these Examples and Comparative Examples.

(Oil film thickness)
The oil film thickness was measured using an EHD2 oil film thickness measuring instrument manufactured by PCS. Under the conditions of an oil temperature of 120 ° C., a slip ratio of 20%, and a load of 20 N, the oil film thickness (nm) was measured at a rotation speed of 20 mm / s by rotating from a rotation speed of 3000 mm / s to 10 mm / s. The larger the value, the thicker the oil film and the better the lubricity.

(Cleanliness)
Cleanliness was evaluated by a panel caulking test based on FED No.791 Rev.B Test Method 3462. Under the conditions of an oil temperature of 100 ° C. and an aluminum panel temperature of 300 ° C., the operation of splashing the lubricating oil composition with the blades rotating in a cycle of "rotating at a speed of 1000 rpm for 15 seconds and then stopping for 45 seconds" was continued for 3 hours. After 3 hours, the mass (mg) of the deposit adhering to the aluminum panel was measured. The smaller the value, the better the cleanliness.

The kinematic viscosity at 40 ° C. (Vk40 ° C.), the kinematic viscosity at 100 ° C. (Vk100 ° C.), the viscosity index (VI), and the CCS viscosity at -30 ° C. (CCS-30 ° C.) of the lubricating oil compositions according to each Example and Comparative Example. ) Was measured. In addition, the contents of calcium, magnesium, zinc, phosphorus, molybdenum, boron, nitrogen, sulfur, and sulfated ash were calculated. The results of the evaluation test described above are summarized in Table 2 below.

As is clear from Tables 1 and 2, the compositions according to the examples satisfying the provisions of the present application are good in all of the viscosity index, the oil film thickness, and the high temperature cleanliness, while the comparative examples not satisfying the provisions of the present application have the viscosity index. , It was found that it was inferior in either oil film thickness or high temperature cleanliness.

Claims (4)

A base oil composition containing GTL base oil as a main component, having a% Cn of 14 to 25% and an aniline point of 120 to 126 ° C.
A comb-shaped polymethacrylate-based viscosity index improver having a weight average molecular weight (Mw) of 400,000 or more,
A lubricating oil composition for an internal combustion engine containing
A lubricating oil composition for an internal combustion engine having a sulfur content of 0.3% by mass or less based on the total weight of the lubricating oil composition. The lubricating oil composition for an internal combustion engine according to claim 1, wherein the kinematic viscosity of the base oil composition at 100 ° C. is 3.5 to 8 mm ^{2 / s.} According to claim 1 or 2, the SAE viscosity grade is 0W-20 or 5W-20 and the viscosity index is 180 or more, or the SAE viscosity grade is 5W-30 and the viscosity index is 220 or more. The lubricating oil composition for an internal combustion engine. The lubricating oil composition for an internal combustion engine according to any one of claims 1 to 3, wherein the base oil composition has a viscosity index of 120 or more.