Lubricating oil composition for automobile engine

Abstract

To provide a new lubricating oil composition excellent in low-temperature characteristics.SOLUTION: An aspect of the present invention is an automobile engine lubricating oil composition comprising a Group III base oil having a main peak with a half-width of 5.00 or less in a carbon number distribution measured by gas chromatography distillation analysis.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a lubricating oil composition for automobile engines. [Background technology]

[0002] In recent years, hybrid vehicles, which have a low environmental impact when driven, have become popular from the perspective of environmental protection. Hybrid vehicles are automobiles powered by a combination of an electric motor and an internal combustion engine.

[0003] Since hybrid vehicles are operated by switching between running on an electric motor and running on an internal combustion engine, the engine needs to be cooled frequently, and therefore engine oils for hybrid vehicles are required to have low-temperature fluidity.

[0004] Patent Document 1 proposes a lubricating oil composition with excellent low-temperature fluidity, which comprises a lubricating base oil containing a synthetic base oil and having a traction coefficient of 0.007 or less at 25°C, and a pour point depressant having a weight-average molecular weight of 40,000 to 100,000, with the pour point depressant content being 0.1 to 1.0 mass% and with the sulfur content, phosphorus content, boron content, etc. in the lubricating oil composition being within predetermined ranges, thereby achieving excellent low-temperature fluidity and shear stability. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2015-098592 Summary of the Invention [Problem to be solved by the invention]

[0006] However, many of the lubricating oil compositions according to the prior art, such as the lubricating oil composition according to Patent Document 1, attempt to improve low-temperature properties by changing the type or content of pour point depressants, etc., and the effect of such attempts has been limited.

[0007] Therefore, an object of the present invention is to provide a novel lubricating oil composition that has excellent low-temperature properties. [Means for solving the problem]

[0008] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by using a specific base oil.

[0009] One aspect of the present invention is a lubricating oil composition comprising a Group III base oil having a half-height width of the main peak in the carbon number distribution measured by gas chromatography distillation analysis of 5.00 or less.

[0010] The lubricating oil composition is preferably for use in automobile engines. The lubricating oil composition preferably contains a viscosity index improver. The viscosity index improver preferably comprises PMA. The lubricating oil composition preferably contains a friction modifier. The friction modifier preferably contains an organic molybdenum compound. The peak position of the main peak is preferably within the range of 25 to 30 carbon atoms. The average carbon number of the Group III base oil is preferably 26.0 or more and 30.0 or less. Preferably, the Group III base oil is a reclaimed base oil. The lubricating oil composition is preferably for use in hybrid automobiles. [Effects of the Invention]

[0011] According to the present invention, a novel lubricating oil composition having excellent low-temperature properties is provided. DETAILED DESCRIPTION OF THE INVENTION

[0012] In this specification, when an upper limit value and a lower limit value are separately described, it is considered that a numerical range combining any upper limit value and any lower limit value is substantially disclosed.

[0013] Unless otherwise specified, all measurements are performed at room temperature (25°C).

[0014] The components, properties, manufacturing method, applications, etc. of the lubricating oil composition will be explained below, but the present invention is not limited thereto.

[0015] <<<Ingredients of lubricating oil composition>>> The lubricating oil composition contains a base oil. The lubricating oil composition may contain other components added depending on the desired properties. Each component will be described below.

[0016] <<Base oil>> The base oil includes a Group III base oil having a main peak half-width of 5.00 or less in the carbon number distribution measured by gas chromatography distillation analysis. Hereinafter, such a base oil will be referred to as a "specific Group III base oil." The half-width of this main peak is preferably 4.80 or less, 4.50 or less, or 4.20 or less. The lower limit of the half-width of this main peak is not particularly limited and may be, for example, 2.00, 2.50, 3.00, 3.50, or 3.80.

[0017] Gas chromatography distillation analysis is carried out, for example, in accordance with ASTM D6352.

[0018] The main peak refers to the peak with the highest intensity in a chart of carbon number distribution measured by gas chromatography distillation analysis.

[0019] In order to make the half-width of the main peak in the carbon number distribution of a Group III base oil 5.00 or less, it is necessary to carry out the Group III base oil refining process (processes for carrying out refining such as solvent refining, hydrotreating, vacuum distillation, and catalytic dewaxing) multiple times. For example, a specific Group III base oil can be obtained by carrying out the refining process of hydrotreating, vacuum distillation, and catalytic dewaxing 10 or more times on a commercially available Group III base oil. By carrying out such refining multiple times and using a specific Group III base oil whose half-width of the main peak in the carbon number distribution is 5.00 or less, the low-temperature properties (particularly low-temperature fluidity) of the lubricating oil composition tend to be improved.

[0020] The peak position of the main peak of the specific Group III base oil preferably has 25 or more carbon atoms, or 26 or more carbon atoms, and preferably has 30 or less carbon atoms, or 28 or less carbon atoms.

[0021] The average carbon number of the specific Group III base oil is preferably 26.0 or more, 26.5 or more, or 27.0 or more, and is preferably 30.0 or less, 29.5 or less, or 29.0 or less.

[0022] The standard deviation of the carbon number of the specific Group III base oil is preferably 3.0 or less, 2.8 or less, 2.6 or less, or 2.4 or less.

[0023] Hydroprocessing is a refining process carried out to completely saturate the aromatic compounds contained in the feedstock oil and to remove impurities such as sulfur and nitrogen. Vacuum distillation is a distillation process carried out under reduced pressure to lower the boiling point of high-boiling petroleum fractions obtained by atmospheric distillation. Catalytic dewaxing is a refining process carried out using a catalyst to remove wax from crude oil. These processes are commonly carried out in base oil refining, but as mentioned above, it has been discovered that specific Group III base oils can be obtained by repeating the process far more times than is normally performed.

[0024] The Group III base oil used to obtain the specific Group III base oil is not particularly limited. Examples of Group III base oils include paraffinic mineral oils produced by advanced hydrorefining of lubricating oil fractions obtained by atmospheric distillation of crude oil, base oils refined by the ISODEWAX process, in which wax produced in a dewaxing process is converted and dewaxed into isoparaffins, and GTL (gas-to-liquid) base oils synthesized by the Fischer-Tropsch process, a technology for converting natural gas into liquid fuel. The specific Group III base oil may also be a recycled base oil (a base oil) that has undergone the aforementioned refining process using appropriate waste oil or the like as a raw material.

[0025] The base oil may contain a base oil other than the specific Group III base oil. In other words, the base oil may be a mixed base oil. The content of the specific Group III base oil based on the entire lubricating oil composition is preferably 50 mass% or more, 60 mass% or more, 70 mass% or more, 80 mass% or more, 90 mass% or more, 95 mass% or more, or 99 mass% or more.

[0026] The content of the base oil based on the entire lubricating oil composition is not particularly limited, but is preferably 50 mass % or more, 60 mass % or more, 70 mass % or more, 80 mass % or more, or 90 mass % or more.

[0027] <<Other ingredients>> Other components include known additives such as friction modifiers, viscosity index improvers, metal detergents, anti-wear agents, dispersants, antifoaming agents, pour point depressants, metal deactivators, antioxidants, etc. These additives may be commercially available products such as packages containing multiple additives.

[0028] The lubricating oil composition preferably contains one or more selected from viscosity index improvers and friction modifiers. By combining such components with the specific Group III base oil, the performance (e.g., low-temperature properties) of the lubricating oil composition can be improved.

[0029] Viscosity index improvers are generally polymeric base materials that improve viscosity indexes. Examples of viscosity index improvers include poly(meth)acrylates and olefin copolymers such as ethylene / propylene copolymers and styrene / diene copolymers, as well as viscosity index improvers obtained by copolymerizing these with nitrogen-containing monomers. The viscosity index improver preferably contains PMA (polymethacrylate).

[0030] The viscosity index improver may be a comb polymer. A comb polymer is a polymer in which relatively long side chains are bonded to the polymer backbone to form a comb shape. Known comb polymers can be used. Specific examples of comb polymers include those containing, in the backbone, (1) repeating units derived from a polyolefin-based macromonomer and (2) repeating units derived from a low-molecular-weight monomer. Examples of low-molecular-weight monomers include styrene monomers having 8 to 17 carbon atoms, alkyl (meth)acrylates having 1 to 10 carbon atoms in the alcohol group, vinyl esters having 1 to 11 carbon atoms in the acyl group, vinyl ethers having 1 to 10 carbon atoms in the alcohol group, (di)alkyl fumarates having 1 to 10 carbon atoms in the alcohol group, (di)alkyl maleates having 1 to 10 carbon atoms in the alcohol group, and mixtures of these monomers. The viscosity index improver preferably contains a comb polymer, and more preferably contains a comb-shaped PMA.

[0031] The content of the viscosity index improver is not particularly limited and is adjusted according to the viscosity grade, etc. As an example, the content of the viscosity index improver is preferably 5.0 mass % or more and less than 15.0 mass %, more preferably 6.5 to 13.5 mass %, and even more preferably 8.0 to 12.0 mass %, based on the total mass of the lubricating oil composition.

[0032] Examples of the friction modifier include an organic molybdenum compound and an ashless friction modifier. Examples of the organic molybdenum compound include molybdenum dialkyldithiocarbamate (sometimes simply referred to as MoDTC etc.), a trinuclear molybdenum compound described in WO98 / 26030, molybdenum sulfide, molybdenum dithiophosphate, a molybdenum-amine complex, a molybdenum-succinimide complex, a molybdenum salt of an organic acid, a molybdenum salt of an alcohol, etc. The friction modifier is preferably an organic molybdenum compound, more preferably MoDTC or MoDTP.

[0033] The content of the friction modifier is not particularly limited and can be appropriately changed according to the type of the friction modifier, the use of the lubricating oil composition, etc. For example, when MoDTC is used as the friction modifier, the content of MoDTC is preferably 50 to 1,000 ppm as the molybdenum content based on the total mass of the lubricating oil composition.

[0034] <<<Physical properties / Properties of the lubricating oil composition>>> <<SAE viscosity grade>> The lubricating oil composition according to the present disclosure preferably has an SAE viscosity grade of 0W-8, 0W-12, 0W-16, 0W-20 or 5W-30.

[0035] <<MRV viscosity (-40°C)>> The lubricating oil composition according to the present disclosure preferably has an MRV viscosity measured at -40°C with a mini rotary viscometer according to ASTM D4684 of 20,000 mPa·s or less, 15,000 mPa·s or less, 14,000 mPa·s or less, or 12,000 mPa·s or less. The lower limit value of the MRV viscosity (-40°C) is not particularly limited, but for example, it is 8,000 mPa·s or 10,000 mPa·s. When the MRV viscosity (-40°C) is within such a range, it is preferably applicable as an engine oil for a hybrid vehicle.

[0036] <<CCS viscosity (-35°C)>> The lubricating oil composition according to the present disclosure preferably has a CCS viscosity (-35°C) measured according to ASTM D5293 of 6,000 mPa·s or less, 5,500 mPa·s or less, or 5,000 mPa·s or less. The lower limit of the CCS viscosity (-35°C) is not particularly limited, but is, for example, 2,000 mPa·s, 3,000 mPa·s, or 4,000 mPa·s. A CCS viscosity (-35°C) within this range is suitable for use as an engine oil for hybrid vehicles.

[0037] Pour point The lubricating oil composition according to the present disclosure preferably has a pour point of −35° C. or less, more preferably −40° C. or less, as measured in accordance with JIS K 2269. When the pour point satisfies this range, the composition can be preferably used as an engine oil for hybrid vehicles.

[0038] <<<Method of manufacturing lubricating oil composition>>> The lubricating oil composition can be produced by appropriately mixing the components, and there are no particular limitations on the order of mixing the components, the mixing conditions, etc. Other components (additives, etc.) may be added as a package product in which multiple types are mixed.

[0039] <<<Uses of lubricating oil compositions>>> The lubricating oil composition according to the present invention has excellent low-temperature properties (low-temperature fluidity), etc. Therefore, it can be used in a variety of applications, and is preferably used as a lubricating oil composition for automobile engines, and more preferably for hybrid automobiles (for automobile engines of hybrid automobiles). [Example]

[0040] The lubricating oil composition will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these in any way.

[0041] <<Raw materials>> <Base oil> Base oils 1 to 5 belonging to Group III were prepared as base oils. Base oils 1 to 3 were commercially available products, base oil 4 was a commercially available product that had been refined, and base oil 5 was a recycled base oil that had been refined from waste oil. The average carbon number, standard deviation of the carbon number, and half-width of the main peak of the carbon number for each base oil are shown in Table 1. The peak position of the main peak for each base oil was 27 carbon atoms.

[0042] <Other ingredients> The additive package (API SP-6 / ILSAC GF-6 DI additive) used included metal detergents, ashless dispersants, zinc dithiophosphate, rust inhibitors, corrosion inhibitors, antioxidants, friction modifiers (MoDTC), viscosity index improvers (comb-type PMA), etc. The additive package accounted for 21.7 mass % of the total lubricating oil composition.

[0043] <<Preparation of Lubricating Oil Composition>> The base oil and additive package were mixed to obtain lubricating oil compositions according to Examples 1-2 and Comparative Examples 1-3. The blending amounts of the base oil and additive package are as shown in Table 1. The viscosity grade of each lubricating oil composition is shown in Table 1.

[0044] <<Evaluation>> The pour point, CCS viscosity (-35°C), and MRV viscosity (-40°C) of each lubricating oil composition were measured. The measurement results are shown in Table 1.

[0045] [Table 1]

[0046] The above evaluation results show that using a Group III base oil with a carbon number distribution main peak half-width of 5.00 or less as the base oil can improve low-temperature fluidity (for example, the MRV viscosity (-40°C) can be reduced to 12,000 mPa s or less). Furthermore, because low-temperature fluidity is improved by the properties of the base oil, it is suggested that the use of additives such as pour point depressants in combination can produce lubricating oil compositions with even better low-temperature fluidity. [Industrial Applicability]

[0047] The lubricating oil composition according to the present invention has excellent low-temperature fluidity and is therefore preferably used in automobile engines (particularly in automobile engines of hybrid vehicles).

Claims

1. A lubricating oil composition for automobile engines comprising a Group III base oil having a main peak half-width of 5.00 or less in a carbon number distribution measured by gas chromatography distillation analysis.

2. Contains a viscosity index improver, 10. The automotive engine lubricating oil composition of claim 1, wherein said viscosity index improver comprises PMA.

3. Contains friction modifiers, 3. The automobile engine lubricating oil composition of claim 1, wherein the friction modifier comprises an organomolybdenum compound.

4. 3. The lubricating oil composition for automobile engines according to claim 1, wherein the peak position of the main peak is within the range of 25 to 30 carbon atoms.

5. 3. The lubricating oil composition for automobile engines according to claim 1, wherein the average carbon number of the Group III base oil is 26.0 or more and 30.0 or less.

6. 3. The automotive engine lubricating oil composition of claim 1, wherein the Group III base oil is a recycled base oil.

7. 3. The lubricating oil composition for automobile engines according to claim 1, which is for use in hybrid automobiles.

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