JP2023176318A - Lubricant composition - Google Patents

Abstract

[Problem] There is a need for a lubricating oil composition that has a high effect of suppressing the occurrence of coking and can be suitably used in internal combustion engines.
[Solution] Contains a base oil (A) with a NOACK value of 6% by mass or less as measured by a NOACK test conducted at 250°C for 1 hour in accordance with ASTM D5800, and has CCS at -25°C. A lubricating oil composition having a viscosity of 7000 mPa·s or less and an HTHS viscosity of 2.9 mPa·s or more at 150°C.
[Selection diagram] None

Description

The present invention relates to a lubricating oil composition and a method of lubricating an internal combustion engine.

There are various requirements for internal combustion engines used in automobiles, etc., such as miniaturization, high output, fuel efficiency, compliance with exhaust gas regulations, etc., and these requirements also apply to lubricating oil compositions used in internal combustion engines. Developments are underway to accommodate this.
For example, in Patent Document 1, for the purpose of providing a lubricating oil composition for internal combustion engines that can suppress the occurrence of coking and copper elution while suppressing a decrease in base number, a lubricating oil base oil and a predetermined amount in terms of boron are disclosed. A lubricating oil composition for an internal combustion engine, comprising a boron-containing alkenylsuccinimide and/or a boron-containing alkylsuccinimide, and a poly(meth)acrylate having a weight average molecular weight and an average carbon number of an alkyl group within a predetermined range. is disclosed.

Japanese Patent Application Publication No. 2015-196696

Under these circumstances, there is a need for a lubricating oil composition that is highly effective in suppressing the occurrence of coking in, for example, high-temperature environments and can be suitably used in internal combustion engines.

As a result of extensive studies, the present inventors have created a lubricating oil composition that uses a base oil with a NOACK value of a predetermined value and has a CCS viscosity at -25°C and an HTHS viscosity at 150°C adjusted to a predetermined range. We have found that the above problems can be solved by doing so. Specifically, the present invention discloses the following aspects.
[1] Contains a base oil (A) with a NOACK value of 6% by mass or less as measured by a NOACK test conducted at 250 ° C. for 1 hour in accordance with ASTM D5800,
CCS viscosity at -25°C is 7000 mPa・s or less,
The HTHS viscosity at 150°C is 2.9 mPa・s or more,
Lubricating oil composition.
[2] A method for lubricating an internal combustion engine, in which the lubricating oil composition according to [1] above is applied to lubricate an internal combustion engine.

A lubricating oil composition according to a preferred embodiment of the present invention has a high effect of suppressing the occurrence of coking in a high-temperature environment. Therefore, the lubricating oil composition of one embodiment of the present invention can be suitably used, for example, for lubricating an internal combustion engine.

Regarding the numerical ranges described in this specification, the upper and lower limits can be arbitrarily combined. For example, when a numerical range is described as "preferably 30 to 100, more preferably 40 to 80", the range of "30 to 80" and the range of "40 to 100" are also described in this specification. Included in the specified numerical range.
Also, for example, when the numerical range is described as "preferably 30 or more, more preferably 40 or more, and preferably 100 or less, more preferably 80 or less", "30 to 80" The range and the range "40 to 100" are also included in the numerical ranges described herein. That is, in defining the upper limit value and lower limit value described in this specification, the numerical range from the lower limit value to the upper limit value can be defined by appropriately selecting from each option and combining them arbitrarily.
Furthermore, as a numerical range described in this specification, for example, the description "60 to 100" means a range of "60 or more and 100 or less."
In addition, a plurality of the various requirements described as preferred embodiments described herein can be combined.

[Composition of lubricating oil composition]
The lubricating oil composition of one embodiment of the present invention contains a base oil (A) having a NOACK value of 6% by mass or less, and satisfies the following requirements (I) and (II).
-Requirement (I): CCS viscosity at -25°C is 7000 mPa·s or less.
- Requirement (II): HTHS viscosity at 150°C is 2.9 mPa·s or more.

By using a lubricating oil composition that satisfies requirement (I), engine startability at low temperatures is improved. A lubricating oil composition having a CCS viscosity of more than 7000 mPa·s at −25° C. tends to have insufficient engine startability in a low-temperature environment.
In this specification, the CCS viscosity at -25°C means a value measured at -25°C in accordance with ASTM D5293.

A lubricating oil composition that satisfies requirement (II) can easily maintain an oil film even at high temperatures and has good wear resistance. Lubricating oil compositions having an HTHS viscosity of less than 2.9 mPa·s at 150° C. tend to have poor wear resistance.
From the viewpoint of improving oil film retention in a high-temperature environment and providing a lubricating oil composition with excellent wear resistance, the HTHS viscosity at 150°C of the lubricating oil composition of one embodiment of the present invention is preferably 3.0 mPa.・s or more, more preferably 3.2 mPa·s or more.
In this specification, HTHS viscosity at 150°C means a value measured at 150°C in accordance with ASTM D4683.

The lubricating oil composition of one embodiment of the present invention may further contain a viscosity index improver (B).
The lubricating oil composition of one embodiment of the present invention may further contain other lubricating oil additives other than the above component (B) within a range that does not impair the effects of the present invention.

The details of each component contained in the lubricating oil composition of one embodiment of the present invention will be described below.

<Component (A): Base oil>
The base oil (A) used in one aspect of the present invention includes one or more selected from mineral oils and synthetic oils.
Mineral oils include, for example, atmospheric residual oils obtained by atmospheric distillation of crude oils such as paraffinic crude oil, intermediate crude oil, and naphthenic crude oil; Extracted oil; Refined oil obtained by subjecting the distillate to one or more refining treatments such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining; It will be done.

Examples of synthetic oils include polyα-olefins such as α-olefin homopolymers and α-olefin copolymers (for example, α-olefin copolymers having 8 to 14 carbon atoms such as ethylene-α-olefin copolymers). -Olefins; Isoparaffins; Polyalkylene glycols; Ester oils such as polyol esters, dibasic acid esters, and phosphoric acid esters; Ether oils such as polyphenyl ethers; Alkylbenzenes; Alkylnaphthalenes; Manufactured from natural gas by the Fischer-Tropsch method, etc. Examples include synthetic oil (GTL) obtained by isomerizing wax (GTL wax).

The NOACK value of the base oil (A) used in one aspect of the present invention is 6% by mass or less. By using the base oil (A) with a NOACK value of 6% by mass or less, even when used in a high-temperature environment, it is difficult to form into a mist, and the amount of coking derived from the mist-formed components can be suppressed. As a result, the lubricating oil composition can be highly effective in suppressing the occurrence of coking in high-temperature environments. On the other hand, if the NOACK value of the base oil (A) used is more than 6% by mass, the prepared lubricating oil composition tends to become a mist in a high-temperature environment and tends to cause coking.
From the viewpoint of providing a lubricating oil composition that further improves mist resistance and is more effective in suppressing the occurrence of coking, the NOACK value of the base oil (A) used in one embodiment of the present invention is 5% by mass or less, 5% by mass or less, and 5% by mass or less. It may be less than 4% by mass, 4% by mass or less, 3% by mass or less, or less than 3% by mass.

Note that the NOACK value of the base oil (A) can be adjusted by, for example, removing light fractions by distillation.
Further, in this specification, the NOACK value means a value measured at 250° C. for 1 hour in accordance with ASTM D5800.

The kinematic viscosity at 40°C of the base oil (A) used in one aspect of the present invention is preferably 32 to 120 mm ² /s, more preferably 34 to 100 mm ² /s, more preferably 35 to 80 mm ² /s, and further Preferably it is 35 to 60 mm ² /s.
In this specification, kinematic viscosity means a value measured in accordance with ASTM D445.

The viscosity index of the base oil (A) used in one aspect of the present invention is preferably 80 or more, more preferably 100 or more, even more preferably 110 or more, even more preferably 120 or more.
In this specification, the viscosity index means a value calculated in accordance with ASTM D2270.

Note that the base oil (A) used in one embodiment of the present invention may be a single type of base oil or a mixed oil that is a combination of two or more types of base oils. When using mixed oil, it is sufficient if the NOACK value of the mixed oil is within the above range. Therefore, the mixture may be a combination of base oils with a NOACK value of 6% by mass or less, or a combination of a base oil with a NOACK value of 6% by mass or less and a base oil with a NOACK value of more than 6% by mass. There may be.
Further, it is preferable that the kinematic viscosity and viscosity index of the mixed oil are within the above ranges.

In the lubricating oil composition of one aspect of the present invention, the content of the base oil (A) is 60% by mass or more, 65% by mass or more, 70% by mass, based on the total amount (100% by mass) of the lubricating oil composition. or more, 75% by mass or more, or 80% by mass or more, and 99.9% by mass or less, 99.5% by mass or less, 99.0% by mass or less, 97.0% by mass or less, 95.0% by mass % or less, 92.0% by mass or less, or 90.0% by mass or less.

<Component (B): Viscosity index improver>
The lubricating oil composition of one embodiment of the present invention may contain a viscosity index improver (B). By containing the viscosity index improver, a lubricating oil composition with good fuel efficiency can be obtained.
Note that the viscosity index improver (B) used in one embodiment of the present invention may be used alone or in combination of two or more kinds.

Examples of the viscosity index improver (B) used in one embodiment of the present invention include non-dispersed polymethacrylates, dispersed polymethacrylates, olefin copolymers (e.g., ethylene-propylene copolymers, etc.), and dispersed olefins. Examples include polymers such as styrene-based copolymers, styrene-based copolymers (eg, styrene-diene copolymers, styrene-isoprene copolymers, etc.).
The viscosity index improver (B) used in one embodiment of the present invention may be a comb-shaped polymer having a structure in which the main chain has many trifurcated branch points from which high-molecular-weight side chains are protruding. It may be a star-shaped polymer having a structure in which three or more chain polymers each having one atom are bonded to each other.

In the lubricating oil composition of one embodiment of the present invention, from the viewpoint of making the lubricating oil composition capable of suppressing the amount of coking, the content of the viscosity index improver (B) in terms of resin content is set in the lubricating oil composition. Based on the total amount (100% by mass) of the product, preferably 0.40% by mass or less, more preferably 0.35% by mass or less, even more preferably 0.30% by mass or less, and 0.01% by mass or more. , 0.03% by mass or more, or 0.05% by mass or more.

Note that the viscosity index improver, pour point depressant, and antifoaming agent used in one embodiment of the present invention are usually made of mineral oil, synthetic oil, etc. in consideration of handling properties and solubility with the base oil (A). It is often commercially available in the form of a solution dissolved in diluent oil. However, the above content of the viscosity index improver (B) means the content in terms of resin content (solid content) excluding diluent oil.

<Additives for lubricating oil>
The lubricating oil composition of one embodiment of the present invention may further contain other lubricating oil additives other than component (B), as necessary, within a range that does not impair the effects of the present invention.
Examples of such lubricating oil additives include metal detergents, pour point depressants, antioxidants, friction modifiers, antiwear agents, metal deactivators, ashless dispersants, and metal deactivators. , antifoaming agents, etc.
These lubricating oil additives may be used alone or in combination of two or more.

[Metal cleaning agent]
The lubricating oil composition of one embodiment of the present invention may further contain a metal-based detergent.
Metal-based detergents may be used alone or in combination of two or more.
Metal-based detergents used in one embodiment of the present invention include metal salts such as metal sulfonates, metal salicylates, and metal phenates. Furthermore, the metal atoms constituting the metal salt are preferably metal atoms selected from alkali metals and alkaline earth metals, and more preferably sodium, calcium, or magnesium.
Note that the metal-based detergent used in one embodiment of the present invention may be a neutral metal-based detergent or an overbased metal-based detergent.

[Pour point depressant]
The lubricating oil composition of one aspect of the present invention may further contain a pour point depressant. The pour point depressants may be used alone or in combination of two or more.
Pour point depressants used in one aspect of the present invention include, for example, polymethacrylates, alkylated aromatic compounds, copolymers of fumarate and vinyl acetate, copolymers of ethylene and vinyl acetate, and have weight average molecular weight Polymethacrylates having a molecular weight of 40,000 to 200,000 are preferred.

[Antioxidant]
The lubricating oil composition of one embodiment of the present invention may further contain an antioxidant. The antioxidants may be used alone or in combination of two or more.
Examples of the antioxidant used in one embodiment of the present invention include amine antioxidants such as alkylated diphenylamine, phenylnaphthylamine, and alkylated phenylnaphthylamine; 2,6-di-t-butylphenol, and 4,4'-methylenebis (2,6-di-t-butylphenol), isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, n-octadecyl-3-(3,5-di-t-butyl-4 Examples include phenolic antioxidants such as -hydroxyphenyl)propionate; sulfur-based antioxidants such as phenothiazine, dioctadecyl sulfide, dilauryl-3,3'-thiodipropionate, and 2-mercaptobenzimidazole; and the like.

[Friction modifier and anti-wear agent]
The lubricating oil composition of one embodiment of the present invention may further contain a friction modifier or an antiwear agent. The friction modifier or anti-wear agent may be used alone or in combination of two or more.
Examples of friction modifiers and antiwear agents used in one embodiment of the present invention include sulfur-based compounds such as sulfurized olefins, dialkyl polysulfides, diarylalkyl polysulfides, and diaryl polysulfides; Phosphorous compounds such as acid esters, thiophosphate esters, phosphite esters, alkyl hydrogen phosphites, phosphate ester amine salts, phosphite ester amine salts; molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (MoDTP), molybdenum Organic molybdenum compounds such as amine salts of acids; organic zinc compounds such as zinc dithiophosphate (ZnDTP) and zinc dithiocarbamate (ZnDTC); amine compounds, fatty acid esters, fatty acid amides, fatty acids, fatty alcohols, aliphatic ethers, Examples include ashless friction modifiers such as urea compounds and hydrazide compounds.

[Metal deactivator]
The lubricating oil composition of one embodiment of the present invention may further contain a metal deactivator. The metal deactivators may be used alone or in combination of two or more.
Examples of the metal deactivator used in one embodiment of the present invention include benzotriazole, triazole derivatives, benzotriazole derivatives, thiadiazole derivatives, and the like.

[Ashless dispersant]
The lubricating oil composition of one embodiment of the present invention may further contain an ashless dispersant from the viewpoint of improving dispersibility. The ashless dispersants may be used alone or in combination of two or more.
The ashless dispersant used in one aspect of the present invention is preferably an alkenylsuccinimide, such as alkenylsuccinimide represented by the following general formula (f-1), or alkenylsuccinimide represented by the following general formula (f-2). Examples include the alkenylsuccinic acid monoimides shown below.

In the above general formulas (f-1) and (f-2), R ^f1 , R ^f2 and R ^f3 are each independently an alkenyl group having a number average molecular weight (Mn) of 900 to 2,500.
Examples of the alkenyl group that can be selected as R ^f1 , R ^f2 and R ^f3 include a polybutenyl group, a polyisobutenyl group, and the like.
A ^f1 , A ^f2 and A ^f3 are each independently an alkylene group having 2 to 5 carbon atoms.
x1 is an integer from 2 to 6.
x2 is an integer from 2 to 6.

The compound represented by the general formula (f-1) or (f-2) is one or more selected from boron compounds, alcohols, aldehydes, ketones, alkylphenols, cyclic carbonates, epoxy compounds, organic acids, etc. It may also be a modified alkenylsuccinimide reacted with.

[Defoaming agent]
The lubricating oil composition of one embodiment of the present invention may further contain an antifoaming agent. Antifoaming agents may be used alone or in combination of two or more.
Examples of the antifoaming agent used in one embodiment of the present invention include alkyl silicone antifoaming agents, fluorosilicone antifoaming agents, fluoroalkyl ether antifoaming agents, and the like.

[Properties of lubricating oil composition]
The kinematic viscosity at 40°C of the lubricating oil composition of one aspect of the present invention is preferably 10 to 150 mm ² /s, more preferably 20 to 120 mm ² /s, more preferably 30 to 110 mm ² /s, even more preferably The speed is 40 to 100 mm ² /s, more preferably 50 to 90 mm ² /s, particularly preferably 55 to 85 mm ² /s.

The kinematic viscosity at 100° C. of the lubricating oil composition of one embodiment of the present invention is preferably 9.5 mm ² /s or more, and the upper limit is not particularly limited, but for example, less than 16.3 mm ² /s. There may be.

The viscosity index of the lubricating oil composition of one aspect of the present invention is preferably 80 or more, more preferably 100 or more, more preferably 110 or more, still more preferably 120 or more, and even more preferably 130 or more.

The mist formation rate of the lubricating oil composition of one embodiment of the present invention, measured and calculated based on the method described in the Examples below, is preferably 0.90% by mass or less, more preferably 0.80% by mass. % or less, more preferably 0.70% by mass or less, even more preferably 0.65% by mass or less, particularly preferably 0.60% by mass or less.

The lubricating oil composition of one embodiment of the present invention was prepared for 24 hours at an oil temperature of 90°C and a panel temperature of 300°C based on the method described in the Examples in accordance with Fed.TestMethodStd.791-3462. When performing the panel caulking test, the amount of caulking material adhering to the panel is preferably 150 mg or less, more preferably 110 mg or less, even more preferably 100 mg or less, particularly preferably 80 mg or less.

[Applications of lubricating oil composition]
The lubricating oil composition of one embodiment of the present invention has excellent mist resistance in a high-temperature environment and is highly effective in suppressing coking.
Therefore, the lubricating oil composition of one embodiment of the present invention can be applied to various devices that can exhibit the above characteristics, and can be suitably used for lubrication between various parts in an internal combustion engine. Among internal combustion engines, the present invention can be particularly suitably used for lubricating various parts in an internal combustion engine that is equipped with a turbotarger and operates using hydrogen as fuel (hereinafter also referred to as a "hydrogen fuel engine"). In a hydrogen fuel engine equipped with a turbotarger, since the fuel is hydrogen, the temperature inside the combustion chamber is extremely high, and the lubricating oil composition is in an environment where it is easy to turn into mist. The misted lubricating oil composition is discharged to the turbine wheel of the turbocharger installed on the exhaust passage side, but it sticks to the turbine wheel and causes coking. In contrast, the lubricating oil composition of one embodiment of the present invention has excellent mist resistance in high-temperature environments, so even when used in a hydrogen fuel engine equipped with a turbotarger, the lubricating oil composition adheres to the turbine wheel. By suppressing the amount of oil composition, it is possible to effectively suppress the occurrence of coking.

Furthermore, in consideration of the above-mentioned properties of the lubricating oil composition of one embodiment of the present invention, the present invention can also provide the following [I].
[I] A method for lubricating an internal combustion engine, in which the lubricating oil composition of one embodiment of the present invention described above is applied to lubricating the engine.
Examples of the internal combustion engine described in [I] above include a hydrogen fuel engine equipped with a turbotarger, and in particular, in a hydrogen fuel engine equipped with a turbine wheel installed on the exhaust passage side of the turbotarger, coking The occurrence of can be effectively suppressed.

As described above, the present invention discloses the following aspects.
[1] Contains a base oil (A) with a NOACK value of 6% by mass or less as measured by a NOACK test conducted at 250 ° C. for 1 hour in accordance with ASTM D5800,
CCS viscosity at -25°C is 7000 mPa・s or less,
The HTHS viscosity at 150°C is 2.9 mPa・s or more,
Lubricating oil composition.
[2] Further contains a viscosity index improver (B),
The lubricating oil composition according to [1] above, wherein the content of the viscosity index improver (B) in terms of resin content is 0.40% by mass or less based on the total amount of the lubricating oil composition.
[3] The lubricating oil composition according to [1] or [2] above, which is used in an internal combustion engine that is equipped with a turbotarger and operates using hydrogen as fuel.
[4] A method for lubricating an internal combustion engine, in which the lubricating oil composition according to [1] or [2] above is applied to lubricate an internal combustion engine.
[5] The method for lubricating an internal combustion engine according to [4] above, wherein the internal combustion engine is an internal combustion engine that is equipped with a turbotarger and operates using hydrogen as fuel.

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples in any way. The methods for measuring various physical properties are as follows.

(1) Kinematic viscosity Measured in accordance with ASTM D445.
(2) Viscosity index at 40°C and 100°C Calculated according to ASTM D2270.
(3) NOACK value Measured at 250° C. for 1 hour in accordance with ASTM D5800.
(4) CCS viscosity Measured at -25°C in accordance with ASTM D5293.
(5) HTHS viscosity (150°C)
Measured at 150°C according to ASTM D4683.

The base oil and various additives used in the following Examples and Comparative Examples are as follows.
<Base oil (A)>
The API (American Petroleum Institute) base oil category classification and properties of base oils (a1-1) to (a1-5) and base oils (a2-1) to (a2-5) used in Examples and Comparative Examples are shown below. It is shown in Table 1.

<Various additives>
- Viscosity index improver (1): A solution prepared by diluting a hydrogenated styrene-diene copolymer with a diluent oil classified into Group III of the API base oil category, resin concentration = 6.5% by mass.
- Viscosity index improver (2): A solution prepared by diluting a hydrogenated styrene-diene copolymer with a diluent oil classified into Group I of the API base oil category, resin concentration = 10.7% by mass.
・Pour point depressant: Polymethacrylate (VISCOPLEX 1-500 (manufactured by EVONIK))
- Additive mixture: JASO DH-2 additive package containing antioxidants, metal detergents, dispersants, antiwear agents, and antifoam agents.

Examples 1-6, Comparative Examples 1-2
The above-mentioned base oil and various additives were added in the amounts shown in Table 2 and thoroughly mixed to prepare lubricating oil compositions. Table 2 shows the properties of the base oil (mixed base oil) used and the properties of the lubricating oil composition prepared.
Further, the following tests were conducted using the prepared lubricating oil composition. These results are also shown in Table 2.

(1) Mist resistance test Under the following measurement conditions, each sample oil, which is a lubricating oil composition prepared, was mixed with compressed air and made into a mist, and the amount of oil made into a floating mist (mass of mist, unit: g) was measured.
(Measurement condition)
・Test device: TACO mist measuring device (model number: C3-0807)
・Air pressure: 0.2MPa
・Sample oil amount: 40g
Then, the mist formation rate was measured using the following formula (i).
・Formula (i): Mist conversion rate (mass%) = [Mist conversion mass (g)/mass of sample oil (=40g)] x 100
The lower the mist formation rate, the less floating mist and the better the mist resistance, and it can be said that the lubricating oil composition has suppressed the occurrence of coking. In this example, when the mist conversion rate was 0.90% by mass or less, it was determined that the lubricating oil composition had good mist resistance.

(2) Panel caulking test Measured in accordance with Fed.TestMethodStd.791-3462.
Specifically, 300 mL of sample oil is placed in a test container equipped with a splasher, an aluminum panel is attached to the top, the sample oil is heated to 90°C and the panel is heated to 300°C, and the splasher is rotated to continuously spray oil onto the panel. A 24-hour test was conducted by splashing water on the surface. After the test was completed, the amount of caulking material adhering to the panel was weighed (unit: mg).
It can be said that the smaller the amount of adhesion, the more excellent the lubricating oil composition is in coking resistance. In this example, when the amount of adhesion was 150 mg or less, it was determined that the lubricating oil composition had good coking resistance.

From Table 2, the lubricating oil compositions prepared in Examples 1 to 6 had better mist resistance than the lubricating oil compositions of Comparative Examples 1 to 2, and the occurrence of coking was effectively suppressed. This was the result.

Claims (5)

Contains a base oil (A) with a NOACK value of 6% by mass or less as measured by a NOACK test conducted at 250 ° C. for 1 hour in accordance with ASTM D5800,
CCS viscosity at -25°C is 7000 mPa・s or less,
The HTHS viscosity at 150°C is 2.9 mPa・s or more,
Lubricating oil composition. Furthermore, it contains a viscosity index improver (B),
The lubricating oil composition according to claim 1, wherein the content of the viscosity index improver (B) in terms of resin content is 0.40% by mass or less based on the total amount of the lubricating oil composition. The lubricating oil composition according to claim 1 or 2, which is used in an internal combustion engine equipped with a turbotarger and operated using hydrogen as fuel. A method for lubricating an internal combustion engine, comprising applying the lubricating oil composition according to claim 1 or 2 to lubrication of an internal combustion engine. The method for lubricating an internal combustion engine according to claim 4, wherein the internal combustion engine is an internal combustion engine that includes a turbotarger and operates using hydrogen as fuel.