Lubricating oil composition for internal combustion engines

Abstract

To provide a lubricant for an internal combustion engine capable of improving fuel economy and suppressing consumption of oil droplets.SOLUTION: A lubricant composition for an internal combustion engine comprises: (A) a lubricant base oil that has a kinematic viscosity at 100°C of 2.0 mm2 / s or more to 6.0 mm2 / s or less; (B) a metallic detergent that has a metal amount derived from a metallic detergent of 100 mass.ppm or more to 3,500 mass.ppm or less based on a total amount of the lubricant composition; and (C) a high-molecular polymer as an oil consumption inhibitor that has a weight average molecular weight (Mw) of 1,500 or more to 350,000 or less, and 0.1 mass% or more to less than 10.0 mass% based on the total amount of the lubricant composition. A difference between a solubility parameter value of the oil consumption inhibitor and the solubility parameter value of the base oil is less than 1.0.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a lubricating oil composition for internal combustion engines, and more particularly to a lubricating oil composition for internal combustion engines that can improve fuel economy and suppress oil droplet consumption. [Background technology]

[0002] Since its invention, internal combustion engines have been the power source for various means of transportation for many years. In recent years, the fuel efficiency required for internal combustion engines has been increasing. To meet this demand, high fuel efficiency performance is also required for lubricating oils for internal combustion engines.

[0003] In order to improve fuel economy, engine oil viscosity is becoming lower. At the same time, in response to the strengthening of exhaust gas regulations, there is a demand for the suppression of oil consumption. Until now, volatility (NOACK) has been defined as an indicator of oil consumption. However, it is inevitable that the base oil will become lighter as the viscosity decreases, and therefore it is considered difficult to suppress consumption due to evaporation any more than at present. In addition, it is known that the proportion of droplet consumption is large in addition to evaporation consumption in actual oil consumption. Therefore, a formulation that can improve fuel economy while suppressing droplet consumption has been required. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2013-538930 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 discloses a lubricating composition capable of reducing intake valve deposits in direct injection engines. However, the lubricating composition described in Patent Document 1 may not be able to simultaneously improve fuel economy and suppress oil droplet consumption. [Means for solving the problem]

[0006] The present inventors have conducted extensive research into a lubricating oil composition for internal combustion engines that can improve fuel economy and suppress oil droplet consumption, and have confirmed that a lubricating oil for internal combustion engines that can improve fuel economy and suppress oil droplet consumption can be obtained by combining specific components, thereby completing the present invention.

[0007] The present invention has been made based on such findings and is as follows. <1> (A) Kinematic viscosity at 100°C is 2.0mm 2 / s or more 6.0mm 2 / s or less lubricating base oil; (B) a metallic detergent is contained in an amount of 100 ppm by mass or more and 3,500 ppm by mass or less, based on the total amount of the lubricating oil composition, in terms of the amount of metal derived from the metallic detergent; and (C) as an oil consumption inhibitor, a polymer having a weight average molecular weight (Mw) of 1,500 or more and 350,000 or less, in an amount of 0.1 mass % or more and less than 10.0 mass % based on the total amount of the lubricating oil composition; wherein the difference between the solubility parameter value of the oil consumption inhibitor and the solubility parameter value of the base oil is less than 1.0. <2> (D) a viscosity index improver in an amount of 20% by mass or less based on the total amount of the lubricating oil composition; <1> The lubricating oil composition for internal combustion engines according to claim 1. <3> (D) the viscosity index improver is a comb-type poly(meth)acrylate, and (C) the high molecular weight polymer used as the oil consumption inhibitor is not a comb-type poly(meth)acrylate; <2> The lubricating oil composition for internal combustion engines according to claim 1, The comb-shaped poly(meth)acrylate is a copolymer of a monomer represented by the following formula (5) and a monomer represented by the following formula (6), 15 The lubricating oil composition for internal combustion engines has a number average molecular weight (Mn) of 1,000 or more and 10,000 or less. [ka] (In formula (5), R 12 represents a hydrogen atom or a methyl group, and R 13 represents a linear or branched hydrocarbon group having 6 to 18 carbon atoms), and [ka] (In formula (6), R 14 represents a hydrogen atom or a methyl group, and R 15 represents a straight-chain or branched hydrocarbon group having 19 or more carbon atoms). <4> The weight average molecular weight (Mw) of the (D) viscosity index improver is greater than 350,000 and less than or equal to 1,000,000. <2> or <3> The lubricating oil composition for internal combustion engines according to claim 1. <5> (A) the lubricating base oil comprises one or more mineral base oils, and the solubility parameter of the base oil is 7.5 or more and 8.5 or less; <1> ~ <4> 2. The lubricating oil composition for internal combustion engines according to claim 1 . <6> The solubility parameter value of the (C) oil consumption inhibitor is 7.5 or more and less than 9.3; <1> ~ <5> 2. The lubricating oil composition for internal combustion engines according to claim 1 . <7> (C) the high molecular weight polymer used as the oil consumption inhibitor is at least one selected from the group consisting of polybutene, polyisobutene, and olefin copolymer; <6> The lubricating oil composition for internal combustion engines according to claim 1. <8> (E) a molybdenum-based friction modifier having a molybdenum content of 100 ppm by mass or more and 2,000 ppm by mass or less based on the total amount of the lubricating oil composition; <1> ~ <7> 2. The lubricating oil composition for internal combustion engines according to claim 1 . <9> (B) the lubricating oil composition contains a calcium-based detergent and a magnesium-based detergent as metal-based detergents, and the amount of calcium derived from the calcium-based detergent is 500 ppm by mass or more and 2500 ppm by mass or less based on the total amount of the lubricating oil composition, and the amount of magnesium derived from the magnesium-based detergent is 50 ppm by mass or more and 800 ppm by mass or less based on the total amount of the lubricating oil composition; <1> ~ <8> 2. The lubricating oil composition for internal combustion engines according to claim 1 . <10> The HTHS viscosity at 150°C is 1.7 mPa s or more and 2.9 mPa s or less. <1> ~ <9> 2. The lubricating oil composition for internal combustion engines according to claim 1 . <11> The HTHS viscosity at 150°C is 2.3 mPa s or more and 2.9 mPa s or less. <1> ~ <10> 2. The lubricating oil composition for internal combustion engines according to claim 1 . Effect of the Invention

[0008] The lubricating oil composition for internal combustion engines of the present invention can provide a lubricating oil for internal combustion engines that can improve fuel economy and suppress oil droplet consumption. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the lubricating oil composition of the present invention will be described. Hereinafter, "one embodiment of the lubricating oil composition of the present invention" may be simply referred to as "the present invention".

[0010] [A] Lubricant base oil The lubricating base oil used in the present invention may be either a mineral base oil or a synthetic base oil, and it is preferred to use a mineral base oil as the lubricating base oil in the present invention.

[0011] As the mineral oil-based base oil, a distillate oil obtained by distilling crude oil at atmospheric pressure can be used. In addition, a lubricating oil fraction obtained by further distilling the distillate oil under reduced pressure and refining the distillate oil by various refining processes can also be used. As the refining process, hydrorefining, solvent extraction, solvent dewaxing, hydrodewaxing, sulfuric acid washing, clay treatment, etc. can be appropriately combined. By combining and processing these refining processes in an appropriate order, a lubricating oil base oil that can be used in the present invention can be obtained. A mixture of multiple refined oils with different properties obtained by subjecting different crude oils or distillate oils to a combination of different refining processes can also be used.

[0012] The mineral base oil used in the present invention is preferably one belonging to API Group III base oil. API Group III base oil is a mineral base oil having a sulfur content of 0.03 mass% or less, a saturate content of 90 mass% or more, and a viscosity index of 120 or more. Multiple types of Group III base oils may be used, or only one type may be used. The mineral base oil used in the present invention may be one belonging to API Group II base oil. API Group II base oil is a mineral base oil having a sulfur content of 0.03 mass% or less, a saturate content of 90 mass% or more, and a viscosity index of 80 or more and less than 120. Multiple types of Group II base oils may be used, or only one type may be used. It is preferable to use a mixture of Group II base oil and Group III base oil.

[0013] In the present invention, the lubricant base oil may contain only mineral base oil, or may contain other lubricant base oil. Specifically, in the present invention, the content of mineral base oil may be, for example, 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 based on the lubricant base oil.

[0014] In the present invention, a synthetic base oil may be used as the lubricating base oil. As the synthetic base oil, an ester base oil is preferable. As the ester base oil, for example, an organic acid ester base oil, a phosphate ester base oil, a silicate ester base oil, etc. may be mentioned. As the synthetic base oil, in addition to ester base oils, polyα-olefins and their hydrogenated products, isobutene oligomers and their hydrogenated products, isoparaffins, alkylbenzenes, alkylnaphthalenes, polyoxyalkylene glycols, dialkyldiphenyl ethers, polyphenyl ethers, and mixtures thereof can be used.

[0015] In the present invention, the base oil is selected so that the difference between the solubility parameter value of the base oil and the solubility parameter value of the high molecular weight polymer used as the oil consumption suppressant described below is less than 1.0. By selecting the base oil and the oil consumption suppressant so that the difference in solubility parameters is less than 1.0, it is possible to improve fuel economy and suppress oil droplet consumption. The solubility parameter value of the base oil in the present invention is, for example, 7.5 or more and 9.5 or less, preferably 7.5 or more and 9.0 or less, more preferably 7.5 or more and 8.8 or less, even more preferably 7.5 or more and 8.5 or less, and most preferably 8.0 or more and 8.5 or less.

[0016] In this specification, the "solubility parameter" is also called the SP value. By definition, the solubility parameter can only be calculated for liquids whose boiling points can be measured, but it was derived from a method of measuring the solubility of polymers in known solvents for the purpose of applying it to polymer compounds. There are two methods for estimating the solubility parameter: a method of estimating from physical property values ​​(a method of determining from the latent heat of vaporization, a method using surface tension) and a method of estimating from molecular structure (Fedors' calculation method, Hansen's calculation method, Hoy's calculation method, etc.). In the present invention, the solubility parameter of the lubricating base oil and the solubility parameter of the high molecular polymer used as an oil consumption suppressant are each calculated based on the Fedors' calculation method. "Considerations on the solubility parameters of additives" Ueda et al., Research on Paints No. 152 Oct. 2010, details the calculation method of the SP value using the Fedors' calculation method. In the Fedors calculation method, both the cohesive energy density and the molar volume are considered to depend on the type and number of substituents. In the Fedors calculation method, the following formula (A) and the constants shown in Table 1 are used to measure the SP value σ. Formula (A) σ(cal / cm 3 )=[ΣEcoh(cal / mol) / ΣV(cm 3 / mol)] 1 / 2

[0017] [Table 1]

[0018] For example, if the base oil is a poly-α-olefin having one >CH-structure, eight -CH2-structures, and one CH3-structure, ΣEcoh (cal / mol) is approximately 10385, and ΣV (cm 3 / mol) is approximately 161.3. Therefore, [ΣEcoh(cal / mol) / ΣV(cm 3 / mol)] 1 / 2 ≒8.40(cal / cm 3In a similar manner, the solubility parameter of a polymer used as an oil consumption suppressant can also be calculated.

[0019] The lubricating base oil included in the present invention has a kinematic viscosity at 100°C of 2.0 mm 2 / s or more 6.0mm 2 The kinematic viscosity at 100° C. of the lubricating base oil included in the present invention is preferably 2.5 mm / s or less. 2 / s or more, preferably 3.0 mm 2 / s or more, and more preferably 3.5 mm 2 The upper limit is preferably 5.5 mm / s or more. 2 / s or less, preferably 5.0 mm 2 / s or less, more preferably 4.5 mm 2 / s or less. The specific range is preferably 2.5 mm 2 / s or more 5.5mm 2 / s or less, preferably 3.0 mm 2 / s or more 5.0mm 2 / s or less, more preferably 3.5 mm 2 / s or more 4.5mm 2 The kinetic viscosity of the lubricating base oil at 100°C is 6.0 mm 2 By having a kinematic viscosity of 2.0 mm / s or less at 100°C, sufficient fuel saving performance can be obtained. 2 / s or more, the formation of an oil film at the lubricated portion can be ensured, and the evaporation loss of the lubricating oil composition can also be reduced.

[0020] The kinematic viscosity at 100°C refers to the kinematic viscosity of all the lubricating base oils mixed together, i.e., the kinematic viscosity of the base oil as a whole, and does not refer to the kinematic viscosity of one specific lubricating base oil when multiple base oils are included. In this specification, the term "kinematic viscosity at 100°C" means the kinematic viscosity at 100°C measured in accordance with ASTM D-445.

[0021] In the present invention, the content of the lubricating base oil is, for example, 50 mass% or more and 95 mass% or less, preferably 60 mass% or more and 95 mass% or less, more preferably 60 mass% or more and 90 mass% or less, even more preferably 60 mass% or more and 85 mass% or less, and most preferably 60 mass% or more and 80 mass% or less, based on the total amount of the lubricating oil composition.

[0022] [B] Metallic detergent The present invention can include, as metal-based detergents, for example, calcium-based detergents, magnesium-based detergents, and / or barium-based detergents, which may be overbased with boric acid, borates, carbonic acid, or carbonates.

[0023] The present invention may contain a metal salicylate as the metal-based detergent. Examples of the metal salicylate include compounds represented by the following formula (1).

[0024] [ka]

[0025] In the formula (1), R 1 each independently represents an alkyl or alkenyl group having 14 to 30 carbon atoms, and n represents 1 or 2, preferably 1. When n=2, R 1 may be a combination of different groups. M represents a metal element, for example, Ca, Mg, or Ba.

[0026] The present invention may contain a metal sulfonate as the metal detergent. Examples of the metal sulfonate include compounds represented by the following formula (2).

[0027] [ka]

[0028] In the formula (2), R 2each independently represents an alkyl group or an alkenyl group having 10 to 80 carbon atoms, and n represents 1 or 2, preferably 1. When n=2, R 2 may be a combination of different groups. 2 It is preferable to use a metal sulfonate containing as a main component (e.g., 90 mol mass % or more based on the total amount of sulfonates in the metal sulfonate) each independently representing an alkyl group or alkenyl group having 10 to 40 carbon atoms. M represents a metal element, for example, Ca, Mg, or Ba.

[0029] The present invention may contain a metal phenate as the metal detergent. Examples of the metal phenate include compounds represented by the following formula (3).

[0030] [ka]

[0031] In formula (3), R 3 represents a linear or branched, saturated or unsaturated alkyl or alkenyl group having 6 to 21 carbon atoms, A represents a sulfide (-S-) group or a methylene (-CH2-) group, and n represents an integer of 1 to 3. 3 may be a combination of two or more different groups. M represents a metal element, for example, Ca, Mg, or Ba.

[0032] R in Equation (3) 3 The number of carbon atoms in R is preferably 9 to 18, and more preferably 9 to 15. 3 By making the carbon number of R equal to or more than the lower limit, the solubility in the base oil can be increased. 3 When the number of carbon atoms is equal to or less than the upper limit, production becomes easy.

[0033] The present invention preferably contains a combination of a calcium-based detergent and a magnesium-based detergent as the metal-based detergent, and most preferably contains calcium salicylate and magnesium sulfonate.

[0034] In the present invention, the content of the metallic detergent is 100 mass ppm or more and 3,500 mass ppm or less based on the total amount of the lubricating oil composition as the amount of metal derived from the metallic detergent. The specific range of the content of the metallic detergent is preferably 200 mass ppm or more and 3,200 mass ppm or less, more preferably 300 mass ppm or more and 3,000 mass ppm or less, and even more preferably 500 mass ppm or more and 2,500 mass ppm or less based on the total amount of the lubricating oil composition as the amount of metal derived from the metallic detergent. By having the content of the metallic detergent be 100 mass ppm or more, effective cleaning performance is expressed. Also, by having the content of the metallic detergent be 3,500 mass ppm or less, there is no adverse effect on fuel saving performance.

[0035] When the present invention includes a magnesium-based detergent, the specific range of the amount of magnesium derived from the magnesium-based detergent is preferably 50 mass ppm or more and 800 mass ppm or less, more preferably 100 mass ppm or more and 700 mass ppm or less, even more preferably 150 mass ppm or more and 600 mass ppm or less, and most preferably 150 mass ppm or more and 400 mass ppm or less, based on the total amount of the lubricating oil composition. By the amount of magnesium derived from the magnesium-based detergent being within the above range, effective cleaning performance can be exhibited and fuel saving performance can be maintained. In this specification, unless otherwise specified, the contents of calcium, magnesium, zinc, boron, phosphorus and molybdenum in oil are measured by inductively coupled plasma atomic emission spectrometry (intensity ratio method (internal standard method)) in accordance with JPI-5S-62.

[0036] When the present invention contains a calcium-based detergent, the specific range of the calcium content derived from the calcium-based detergent is preferably 500 mass ppm or more and 2,500 mass ppm or less, more preferably 1,000 mass ppm or more and 2,200 mass ppm or less, and even more preferably 1,500 mass ppm or more and 2,000 mass ppm or less, based on the total amount of the lubricating oil composition. By having the calcium content derived from the calcium-based detergent within the above range, effective cleaning performance can be exhibited and fuel saving performance can be maintained.

[0037] (Base Number) When the present invention includes a magnesium-based detergent, the base number of the magnesium-based detergent is preferably in the range of 200 mgKOH / g to 600 mgKOH / g, more preferably 250 mgKOH / g to 500 mgKOH / g, and further preferably 300 mgKOH / g to 450 mgKOH / g. In this specification, the base number of the metal-based detergent is a value measured according to JIS K 2501:2003, No. 9.

[0038] When the present invention contains a calcium-based detergent, the base number of the calcium-based detergent is preferably in the range of 140 mgKOH / g or more and 400 mgKOH / g or less, more preferably 160 mgKOH / g or more and 300 mgKOH / g or less.

[0039] [C] Oil consumption suppressant The present invention includes an oil consumption inhibitor. An oil consumption inhibitor is a polymer that, when added to a lubricating oil, prevents the lubricating oil from dispersing in mist. Examples of polymers that can be used as oil consumption inhibitors include polymers having a weight average molecular weight (Mw) of 1,500 to 350,000, such as polybutene (PB), polyisobutene (PIB), ethylene-propylene copolymer (EPC), olefin copolymer (OCP), poly(meth)acrylate (PMA), and styrene-diene copolymer (SDC). The polymer is preferably polybutene (PB), polyisobutene (PIB), or olefin copolymer (OCP), more preferably polybutene (PB) or polyisobutene (PIB), and most preferably polyisobutene (PIB). The type of the high molecular weight polymer can be appropriately selected in consideration of the solubility parameter value of the base oil. The high molecular weight polymer that can be used as the oil consumption suppressant can contain or not contain comb-type poly(meth)acrylate. "(Meth)acrylate" means acrylate and / or methacrylate, and "poly(meth)acrylate" means a polymer that includes acrylate and / or methacrylate monomeric units.

[0040] The lower limit of the weight average molecular weight of the high molecular weight polymer used as the oil consumption inhibitor can be 1,500 or more, 5,000 or more, 10,000 or more, 30,000 or more, 50,000 or more, 75,000 or more, 100,000 or more, 150,000 or more, 200,000 or more, or 250,000 or more. The upper limit can be 350,000 or less, 300,000 or less, 250,000 or less, 200,000 or less, 150,000 or less, 100,000 or less, 75,000 or less, or 50,000 or less. The weight average molecular weight of the high molecular weight polymer used as the oil consumption inhibitor can be 1,500 to 300,000, 1,500 to 200,000, 15,000 to 100,000, or 1,500 to 75,000. By making the weight average molecular weight of the high molecular weight polymer used as the oil consumption inhibitor 350,000 or less, fuel economy can be improved.

[0041] In the present invention, the difference between the solubility parameter value of the high molecular weight polymer used as the oil consumption suppressant and the solubility parameter value of the base oil is less than 1.0. Taking into consideration the solubility parameter value of the base oil, a high molecular weight polymer having a specific solubility parameter can be appropriately selected, and a high molecular weight polymer having a solubility parameter value of, for example, 6.5 to 10.5, preferably 7.0 to 10.0, more preferably 7.3 to 9.3, and even more preferably 7.5 to less than 9.3 can be used. The difference between the solubility parameter value of the high molecular weight polymer used as the oil consumption inhibitor and the solubility parameter value of the base oil can be less than 0.9, 0.8, or 0.7. The solubility parameter value of the high molecular weight polymer used as the oil consumption inhibitor and the solubility parameter value of the base oil may be the larger value. When the difference between the solubility parameter value of the high molecular weight polymer used as the oil consumption inhibitor and the solubility parameter value of the base oil is less than 1.0, the solubility of the high molecular weight polymer in the base oil is high, and the oil mist suppression effect is high.

[0042] In the present invention, the content of the oil consumption inhibitor is 0.1 mass% or more and less than 10.0 mass% based on the total amount of the lubricating oil composition. The content of the oil consumption inhibitor is preferably 0.2 mass% or more, more preferably 0.3 mass% or more, and even more preferably 0.5 mass% or more based on the total amount of the lubricating oil composition. The upper limit is preferably 8.0 mass% or less, more preferably 7.0 mass% or less, and even more preferably 5.0 mass% or less. The specific range is preferably 0.2 mass% or more and 8.0 mass% or less, more preferably 0.3 mass% or more and 7.0 mass% or less, and even more preferably 0.5 mass% or more and 5.0 mass% or less. By having the content of the oil consumption inhibitor within the above range, it is possible to maintain fuel saving performance while exhibiting the oil mist suppression effect.

[0043] [D] Viscosity index improver The present invention preferably contains a viscosity index improver. The viscosity index improver means a compound that, when added to a lubricating oil, has the function of reducing the viscosity change of the lubricating oil caused by a change in temperature. As the viscosity index improver, any viscosity index improver used in the field of lubricating oil compositions can be used without limit, as long as the effect of the present invention can be obtained. Examples of viscosity index improvers that can be used include polybutene (PB), polyisobutene (PIB), ethylene-propylene copolymer (EPC), olefin copolymer (OCP), poly(meth)acrylate (PMA), styrene-diene copolymer (SDC), etc. Poly(meth)acrylate (PMA) is preferred, and comb-type poly(meth)acrylate is more preferred.

[0044] An example of the poly(meth)acrylate is a poly(meth)acrylate in which the proportion of (meth)acrylate structural units represented by the following general formula (4) in all monomer units in the polymer is 10 to 90 mol %.

[0045] [ka] (In formula (4), R 10 represents hydrogen or a methyl group, and R 11represents a linear or branched hydrocarbon group having 1 to 5 carbon atoms.

[0046] When the proportion of the (meth)acrylate structural unit represented by the general formula (4) in all monomer units in the poly(meth)acrylate polymer exceeds 90 mol %, the solubility in the base oil, the effect of improving the viscosity-temperature characteristics, or the low-temperature viscosity characteristics may be inferior, whereas when it is less than 10 mol %, the effect of improving the viscosity-temperature characteristics may be inferior.

[0047] In this specification, the comb-type poly(meth)acrylate refers to a poly(meth)acrylate which is a copolymer of a monomer (M-1) represented by formula (5) and a monomer (M-2) represented by formula (6). 15 The number average molecular weight (Mn) of the macromonomer is 1,000 or more and 10,000 or less (preferably 1,500 or more and 8,500 or less, and more preferably 2,000 or more and 7,000 or less).

[0048] [ka] (In formula (5), R 12 represents a hydrogen atom or a methyl group, and R 13 represents a linear or branched hydrocarbon group having 6 to 18 carbon atoms.

[0049] [ka] (In formula (6), R 14 represents a hydrogen atom or a methyl group, and R 15 represents a linear or branched hydrocarbon group having 19 or more carbon atoms.

[0050] As comb-type poly(meth)acrylates, for example, macromonomers derived from hydrogenated polyolefins obtained by copolymerizing butadiene and isoprene can be used. In the poly(meth)acrylate used in the present invention, the (meth)acrylate structural unit corresponding to the monomer (M-2) represented by the general formula (6) in the polymer may be of only one type or of a combination of two or more types. The proportion of the structural unit corresponding to the monomer (M-2) represented by the general formula (6) in the total monomer units in the polymer is preferably 0.5 to 70 mol %.

[0051] The weight average molecular weight of the viscosity index improver can be from greater than 100,000 to less than 2,000,000, from greater than 150,000 to less than 1,800,000, from greater than 200,000 to less than 1,500,000, from greater than 250,000 to less than 1,200,000, from greater than 300,000 to less than 1,100,000, or from greater than 350,000 to less than 1,000,000.

[0052] When the present invention contains a viscosity index improver, the content thereof can be appropriately adjusted so that the viscosity index of the lubricating oil composition is preferably 160 or more and 310 or less, more preferably 170 or more and 290 or less. When the viscosity index improver is included in the present invention, its content is 0.1 mass% or more, preferably 1 mass% or more, more preferably 3 mass% or more, and even more preferably 5 mass% or more based on the total amount of the lubricating oil composition. The upper limit is 20 mass% or less, preferably 18 mass% or less, more preferably 16 mass% or less, and even more preferably 14 mass% or less. The specific range is 0.1 mass% or more and 20 mass% or less, preferably 1 mass% or more and 18 mass% or less, more preferably 3 mass% or more and 16 mass% or less, and even more preferably 5 mass% or more and 14 mass% or less.

[0053] In this specification, the weight average molecular weight and number average molecular weight of the oil consumption inhibitor and the viscosity index improver respectively refer to values ​​determined by gel permeation chromatography (GPC) (molecular weight obtained in terms of polystyrene). Note that the measurement conditions for determining Mw, Mn and Mw / Mn by GPC are as follows: Those skilled in the art can select the appropriate method from Condition 1 and Condition 2 depending on the type of oil consumption inhibitor or viscosity index improver to be measured and the weight average molecular weight or number average molecular weight. Although not limited to the following, in principle, high molecular weight polymers are measured under Condition 1, and low molecular weight polymers (e.g., weight average molecular weight of 10,000 or less) are measured under Condition 2.

[0054] [GPC measurement condition 1] Equipment: Waters Corporation ACQUITY (registered trademark) APC UV RI system Columns: From the upstream side, two Waters Corporation ACQUITY (registered trademark) APC XT900A (gel particle size 2.5 μm, column size (inner diameter x length) 4.6 mm x 150 mm) and one Waters Corporation ACQUITY (registered trademark) APC XT200A (gel particle size 2.5 μm, column size (inner diameter x length) 4.6 mm x 150 mm) were connected in series. Column temperature: 40℃ Sample solution: 1.0% sample concentration in tetrahydrofuran Flow rate: 0.8mL / min Detector: Differential refractive index detector Reference material: Standard polystyrene (Agilent EasiCal (registered trademark) PS-1, manufactured by Agilent Technologies) 8 points (molecular weight: 2698000, 660500, 325600, 128600, 69650, 30230, 9960, 2980)

[0055] [GPC measurement condition 2] Equipment: Waters Corporation ACQUITY (registered trademark) APC UV RI system Columns: From the upstream side, one Waters Corporation ACQUITY (registered trademark) APC XT125A (gel particle size 2.5 μm, column size (inner diameter x length) 4.6 mm x 150 mm) and two Waters Corporation ACQUITY (registered trademark) APC XT45A (gel particle size 1.7 μm, column size (inner diameter x length) 4.6 mm x 150 mm) were connected in series. Column temperature: 40℃ Sample solution: 1.0% sample concentration in tetrahydrofuran Flow rate: 0.7mL / min Detector: Differential refractive index detector Reference material: 10 standard polystyrenes (Agilent EasiCal (registered trademark) PS-1, manufactured by Agilent Technologies) (molecular weights: 30230, 9960, 2980, 890, 786, 682, 578, 474, 370, 266).

[0056] [E] Molybdenum-based friction modifier The present invention preferably further comprises a molybdenum-based friction modifier, and the molybdenum-based friction modifier is preferably molybdenum dithiocarbamate (MoDTC).

[0057] As MoDTC, for example, a compound represented by the following formula (7) can be used.

[0058] [ka]

[0059] In the formula (7), R 20 ~R 23may be the same or different, and are an alkyl group having 2 to 24 carbon atoms or an (alkyl)aryl group having 6 to 24 carbon atoms, preferably an alkyl group having 4 to 13 carbon atoms or an (alkyl)aryl group having 10 to 15 carbon atoms. The alkyl group may be a primary alkyl group, a secondary alkyl group, or a tertiary alkyl group, and may be linear or branched. In addition, "(alkyl)aryl group" means "aryl group or alkylaryl group." In the alkylaryl group, the alkyl group may be substituted at any position on the aromatic ring. X 1 ~X 4 are each independently a sulfur atom or an oxygen atom, and X 1 ~X 4 At least one of the is a sulfur atom.

[0060] Examples of molybdenum-based friction modifiers other than MoDTC include molybdenum dithiophosphate, molybdenum oxide, molybdic acid, molybdates such as ammonium salts, molybdenum disulfide, molybdenum sulfide, molybdic sulfide, and sulfur-containing organic molybdenum compounds.

[0061] When the present invention contains a molybdenum-based friction modifier, its content is, for example, 0.01 mass% or more and 10 mass% or less, preferably 0.1 mass% or more and 8 mass% or less, more preferably 0.5 mass% or more and 5 mass% or less, and even more preferably 0.5 mass% or more and 2 mass% or less, based on the total amount of the lubricating oil composition. By making the content of the molybdenum-based friction modifier equal to or more than the lower limit, the fuel saving performance can be further improved. In addition, by making the content of the molybdenum-based friction modifier equal to or less than the upper limit, the storage stability of the lubricating oil composition can be improved.

[0062] When the present invention contains a molybdenum-based friction modifier, the amount of molybdenum derived from the molybdenum-based friction modifier is preferably 100 mass ppm or more and 2,000 mass ppm or less, more preferably 500 mass ppm or more and 1,000 mass ppm or less, based on the total amount of the lubricating oil composition. By making the molybdenum content equal to or more than the lower limit, the fuel saving performance can be further improved. In addition, by making the amount of molybdenum equal to or less than the upper limit, the storage stability of the lubricating oil composition can be improved.

[0063] (Other additives) The present invention may further include ashless friction modifiers, antioxidants, and / or dispersants.

[0064] As the ashless friction modifier, it is preferable to add N-oleoyl sarcosine. When the lubricating oil composition of the present invention contains an ashless friction modifier, the content thereof is 3.0 mass% or less, preferably 2.0 mass% or less, and also preferably 0.1 mass% or more, more preferably 0.2 mass% or more, based on the total amount of the lubricating oil composition.

[0065] As the antioxidant, it is preferable to add zinc dialkyldithiophosphate (ZnDTP). For example, the zinc dialkyldithiophosphate may be a compound represented by the following general formula (8).

[0066] [ka]

[0067] R in the general formula (8) 30 ~R 33are each independently a straight-chain or branched alkyl group having 1 to 24 carbon atoms. This alkyl group may be primary, secondary, or tertiary. As the zinc dialkyldithiophosphate, zinc dithiophosphate having a primary alkyl group (primary ZnDTP) or zinc dithiophosphate containing a secondary alkyl group (secondary ZnDTP) is preferred, and in particular, those containing zinc dithiophosphate having a secondary alkyl group as the main component are preferred because they enhance abrasion resistance. In the present invention, these zinc dialkyldithiophosphates may be used alone or in combination of two or more.

[0068] When the present invention contains zinc dialkyldithiophosphate, the content thereof is, for example, 0.01 mass % or more and 20 mass % or less, preferably 0.1 mass % or more and 10 mass % or less, more preferably 0.2 mass % or more and 5 mass % or less, and even more preferably 0.5 mass % or more and 2 mass % or less, based on the total amount of the lubricating oil composition.

[0069] The amount of phosphorus derived from the zinc dialkyldithiophosphate contained in the present invention is, for example, from 100 ppm by mass to 2,000 ppm by mass, and preferably from 500 ppm by mass to 1,000 ppm by mass, based on the total amount of the lubricating oil composition.

[0070] As the antioxidant, known antioxidants such as amine-based antioxidants or molybdenum-based antioxidants can be used. Examples include amine-based antioxidants such as bis(nonan-1-ylphenyl)amine and molybdenum-based antioxidants such as dialkylamine molybdate. When the lubricating oil composition contains an antioxidant other than zinc dialkyldithiophosphate, the content thereof is usually 5.0 mass % or less, preferably 3.0 mass % or less, and also preferably 0.1 mass % or more, and more preferably 0.5 mass % or more, based on the total amount of the lubricating oil composition.

[0071] Dispersants include ashless dispersants such as succinimides or benzylamines. When the present invention contains a dispersant, the content thereof is usually 5.0 mass % or less, and preferably 0.1 mass % or more, based on the total amount of the lubricating oil composition.

[0072] The present invention can include other additives commonly used in lubricating oils for further improving its performance, depending on the purpose, such as anti-wear or extreme pressure agents, pour point depressants, corrosion inhibitors, rust inhibitors, metal deactivators, antifoam agents, etc.

[0073] (Lubricating oil composition for internal combustion engines) The HTHS viscosity at 150°C of the present invention is 1.7 mPa·s or more and 2.9 mPa·s or less, preferably 1.8 mPa·s or more and 2.9 mPa·s or less, more preferably 2.0 mPa·s or more and 2.9 mPa·s or less, and even more preferably 2.3 mPa·s or more and 2.9 mPa·s or less. By having an HTHS viscosity at 150°C of 2.9 mPa·s or less, good fuel saving performance can be obtained. By having an HTHS viscosity at 150°C of 1.7 mPa·s or more, good lubricity can be obtained. The HTHS viscosity at 150°C refers to the high temperature high shear viscosity at 150°C as specified in ASTM D 4683.

[0074] The HTHS viscosity at 100° C. of the present invention is 4.8 mPa·s or more and 6.0 mPa·s or less, preferably 4.9 mPa·s or more and 5.9 mPa·s or less, more preferably 5.0 mPa·s or more and 5.8 mPa·s or less, and even more preferably 5.0 mPa·s or more and 5.7 mPa·s or less. By having an HTHS viscosity at 100° C. of 4.8 mPa·s or more, good lubricity can be obtained, and by having an HTHS viscosity of 6.0 mPa·s or less, the necessary low-temperature viscosity and sufficient fuel-saving performance can be obtained. The HTHS viscosity at 100°C refers to the high temperature, high shear viscosity at 100°C as specified in ASTM D 4683.

[0075] The viscosity index of the present invention is preferably from 160 to 310, more preferably from 170 to 290. By having a viscosity index of 160 or more, it is possible to improve fuel economy performance while maintaining the HTHS viscosity at 150° C. In addition, if the viscosity index of the lubricating oil composition exceeds 290, there is a risk of volatility being deteriorated. In this specification, the viscosity index means a viscosity index measured in accordance with JIS K 2283-1993.

[0076] The lubricating oil composition of the present invention preferably has a kinematic viscosity at 40° C. of 14 mm 2 / s or more, preferably 18 mm 2 / s or more, more preferably 20 mm 2 / s or more, most preferably 22 mm 2 / s or more. The upper limit is preferably 40 mm 2 / s or less, preferably 36 mm 2 / s or less, and more preferably 33 mm 2 / s or less, most preferably 30 mm 2 / s or less. The specific range is preferably 14 mm 2 / s or more 40mm 2 / s or less, preferably 18 mm 2 / s or more 36mm 2 / s or less, more preferably 20 mm 2 / s or more 33mm 2 / s or less, most preferably 22 mm 2 / s or more 30mm 2 The lubricating oil composition has a kinetic viscosity of 40mm / s or less at 40°C. 2 When the kinematic viscosity of the lubricating oil composition at 40° C. is 14 mm / s or less, sufficient fuel saving performance can be obtained. 2 / s or more, the formation of an oil film at the lubricated portion can be ensured, and the evaporation loss of the lubricating oil composition can also be reduced. In this specification, the term "kinematic viscosity at 40°C" means the kinematic viscosity at 40°C measured in accordance with ASTM D-445.

[0077] The lubricating oil composition of the present invention preferably has a kinematic viscosity at 100°C of 4.0 mm 2 / s or more, preferably 6.0 mm 2 / s or more. The upper limit is preferably 10.0 mm 2 / s or less, preferably 9.0 mm 2 / s or less. The specific range is preferably 4.0 mm 2 / s or more 10.0mm 2 / s or less, preferably 6.0 mm 2 / s or more 9.0mm 2 / s or less.

[0078] The lubricating oil composition of the present invention has a density at 15° C. (ρ 15 ) is preferably 0.860 or less, more preferably 0.850 or less. In this specification, the density at 15°C means the density measured at 15°C in accordance with ASTM D4052. EXAMPLES

[0079] The present invention will be described below with reference to examples, but the present invention is not limited to the following embodiments.

[0080] <Lubricant blend> For each Example and Comparative Example, a test lubricating oil composition was prepared by blending the base oil and additives in the blending ratios shown in Tables 2 and 3. The test lubricating oil compositions obtained were evaluated as follows. The evaluation results are shown in Tables 4 and 5.

[0081] (A) Base oil Base oil 1: Group III base oil (hydrorefined mineral oil) kinematic viscosity 4.2mm 2 / s(100℃), viscosity index 125 Base oil 2: Group III base oil (hydrorefined mineral oil) kinematic viscosity 3.9mm 2 / s(100℃), viscosity index 144 Base oil 3: Group II base oil (hydrorefined mineral oil) kinematic viscosity 3.0mm 2 / s(100℃), viscosity index 106 Base oil 4: Poly-α-olefin, kinematic viscosity 5.2mm 2 / s(100℃), viscosity index 145 Base oil 5: Ester base oil, kinematic viscosity 3.0mm 2 / s(100℃), viscosity index 146 Base oil 6: Ester base oil, kinematic viscosity 4.4mm 2 / s(100℃), viscosity index 140 Lubricating base oils were prepared by mixing base oils in the mass ratios shown in Tables 2 and 3. In the tables, the values ​​of the base oils indicate mass ratios based on the total amount of the base oils.

[0082] Additives were added as shown in Tables 2 and 3. Details of the additives are as follows: The blending amount of the additives is based on the total amount of the lubricating oil composition. (B) Metallic detergents Metallic detergent 1: Calcium carbonate salicylate (calcium content 6.2% by mass, base number: 170 mgKOH / g) Metallic detergent 2: Calcium borate salicylate (calcium content 6.8% by mass, boron content 2.7% by mass, base number: 190 mg KOH / g) Metallic detergent 3: Magnesium carbonate sulfonate (magnesium content 9.1% by mass, base number: 405 mg KOH / g) (C) Viscosity index improver Viscosity index improver 1: Comb-type poly(meth)acrylate (weight average molecular weight 500,000, SP value 9.3) (D) Oil consumption suppressant Oil consumption inhibitor 1: Polyisobutene (weight average molecular weight 300,000, SP value 7.7) Oil consumption inhibitor 2: Olefin copolymer (weight average molecular weight 120,000, SP value 8.3) Oil consumption inhibitor 3: Olefin copolymer (weight average molecular weight 190,000, SP value 8.3) Oil consumption inhibitor 4: Poly(meth)acrylate (weight average molecular weight 100,000, SP value 9.3) Oil consumption inhibitor 5: Styrene-diene copolymer (weight average molecular weight 400,000, SP value 10.5) Oil consumption inhibitor 6: Polyisobutene (weight average molecular weight 500,000, SP value 7.7) Oil consumption inhibitor 7: Polybutene (weight average molecular weight 2,000, SP value 8.0) Oil consumption inhibitor 8: Polyisobutene (weight average molecular weight 49,000, SP value 7.7) Oil consumption inhibitor 9: Comb-type poly(meth)acrylate (weight average molecular weight 300,000, SP value 9.3) (E) Friction modifier Mo-based friction modifier 1: Molybdenum dithiocarbamate (molybdenum content 10.1% by mass) Ashless friction modifier 1: N-oleoyl sarcosinic acid (F) Dispersant Dispersant 1: Succinimide-based dispersant (nitrogen content 0.8% by mass, boron content 0.0% by mass) (G) Antioxidants Antioxidant 1: Amine-based ashless antioxidant (bis(nonan-1-ylphenyl)amine, nitrogen content 3.6% by mass) Antioxidant 2: Molybdenum-based antioxidant (molybdic acid dialkylamine salt, molybdenum content 10.0% by mass, nitrogen content 1.2% by mass) Antioxidant 3: Phosphorus-based antioxidant (zinc dialkyldithiophosphate, zinc content 9.3% by mass, phosphorus content 8.5% by mass, sulfur content 17.8% by mass, secondary ZnDTP) Antioxidant 4: Phosphorus-based antioxidant (zinc dialkyldithiophosphate, zinc content 7.8% by mass, phosphorus content 7.0% by mass, sulfur content 14.8% by mass, primary ZnDTP)

[0083] <Evaluation method> (1) HTHS viscosity and viscosity index The HTHS viscosities at 100° C. and 150° C. were measured according to the method specified in ASTM D 4683. The viscosity index was also measured in accordance with JIS K 2283-1993. Test lubricating oil compositions with an HTHS viscosity at 150°C of 1.7 mPa·s or more and 2.9 mPa·s or less were evaluated as having good fuel saving performance and good lubricity.

[0084] (2) Mist test (evaluation of oil droplet consumption) Compressed air was supplied to the lubricating oil, whose temperature was adjusted to 40°C inside the mist generator, to generate mist by the Venturi effect. The air pressure was adjusted to 0.07 MPa. The larger the oil mist particle size, the more likely it is to aggregate, and so it is trapped upstream in the system. The ease of generating oil mist was evaluated based on the amount of mist with the smallest particle size that was not aggregated or trapped in the test system (amount of stray mist). Test lubricating oil compositions with an amount of stray mist of 25.00 g / h or less were evaluated as having low droplet consumption.

[0085] The evaluation results of each test lubricating oil composition are shown in the following Tables 4 to 5. The density at 15° C. of each of the test lubricating oil compositions of Examples 1 to 6 and Comparative Examples 1 to 4 was 0.850 or less.

[0086] [Table 2]

[0087] [Table 3]

[0088] [Table 4]

[0089] [Table 5]

[0090] The test lubricating oil compositions of Examples 1 to 6, in which an oil consumption inhibitor with a weight average molecular weight of 1,500 or more and 350,000 or less was used as the oil consumption inhibitor and the difference between the solubility parameter value of the oil consumption inhibitor and the solubility parameter value of the base oil was less than 1.0, all had an HTHS viscosity at 150°C of 1.7 mPa·s or more and 2.9 mPa·s or less, and an amount of streaky mist of 25.00 g / h or less, and therefore showed good results. In Comparative Example 1, which did not contain an oil consumption inhibitor, the amount of Stream Mist exceeded 25.00 g / h. In Comparative Examples 2 and 3, in which the difference between the solubility parameter value of the oil consumption inhibitor and the solubility parameter value of the base oil was 1.0 or more, the amount of Stream Mist exceeded 25.00 g / h. In Comparative Example 4, in which an oil consumption inhibitor with a weight average molecular weight of 500,000 was used, the HTHS viscosity exceeded 2.9 mPa·s. [Industrial Applicability]

[0091] The lubricating oil composition for internal combustion engines of the present invention can provide a lubricating oil for internal combustion engines that can improve fuel economy and suppress oil droplet consumption.

Claims

1. (A) Kinematic viscosity at 100 ° C. is 2.0 mm ２ / s or more 6.0mm ２ / s or less lubricating base oil; (B) a metallic detergent is contained in an amount of 100 ppm by mass or more and 3,500 ppm by mass or less, based on the total amount of the lubricating oil composition, in terms of the amount of metal derived from the metallic detergent; and (C) an oil consumption inhibitor, a polymer having a weight average molecular weight (Mw) of 1,500 or more and 350,000 or less, in an amount of 0.1 mass % or more and less than 10.0 mass % based on the total amount of the lubricating oil composition; (D) a viscosity index improver is contained in an amount of 20 mass% or less based on the total amount of the lubricating oil composition, The difference between the solubility parameter value of the oil consumption inhibitor and the solubility parameter value of the base oil is less than 1.0; The viscosity index improver (D) is a comb-type poly(meth)acrylate, and the high molecular weight polymer used as the oil consumption inhibitor (C) is not a comb-type poly(meth)acrylate, The lubricating oil composition for internal combustion engines, wherein the comb-type poly(meth)acrylate is a copolymer of a monomer represented by the following formula (5) and a monomer represented by the following formula (6), and R 15 in formula (6) has a number average molecular weight (Mn) of 1,000 or more and 10,000 or less. 【Chemistry 5】 (In formula (5), R 12 represents a hydrogen atom or a methyl group, and R 13 represents a linear or branched hydrocarbon group having 6 to 18 carbon atoms), and 【Chemistry 6】 (In formula (6), R 14 represents a hydrogen atom or a methyl group, and R 15 represents a linear or branched hydrocarbon group having 19 or more carbon atoms).

2. 2. The lubricating oil composition for internal combustion engines according to claim 1, wherein the weight average molecular weight (Mw) of the viscosity index improver (D) is greater than 350,000 and not greater than 1,000,000.

3. 3. The lubricating oil composition for internal combustion engines according to claim 1 or 2, wherein the lubricating base oil (A) comprises one or more mineral base oils, and the solubility parameter of the base oil is 7.5 or more and 8.5 or less.

4. 4. A lubricating oil composition for internal combustion engines according to claim 1, wherein the solubility parameter of the oil consumption inhibitor (C) is 7.5 or more and less than 9.

3.

5. 5. The lubricating oil composition for internal combustion engines according to claim 4, wherein (C) the high molecular weight polymer used as the oil consumption inhibitor is at least one selected from the group consisting of polybutene, polyisobutene, and olefin copolymers.

6. The lubricating oil composition for internal combustion engines according to any one of claims 1 to 5, further comprising (E) a molybdenum-based friction modifier in an amount, in terms of molybdenum, of 100 ppm by mass or more and 2,000 ppm by mass or less, based on the total amount of the lubricating oil composition.

7. 7. A lubricating oil composition for internal combustion engines according to any one of claims 1 to 6, comprising as the metal-based detergents (B) a calcium-based detergent and a magnesium-based detergent, the amount of calcium derived from the calcium-based detergent being 500 ppm by mass or more and 2500 ppm by mass or less, based on the total amount of the lubricating oil composition, and the amount of magnesium derived from the magnesium-based detergent being 50 ppm by mass or more and 800 ppm by mass or less, based on the total amount of the lubricating oil composition.

8. 8. A lubricating oil composition for internal combustion engines according to claim 1, having a HTHS viscosity at 150° C. of 1.7 mPa·s or more and 2.9 mPa·s or less.

9. 9. A lubricating oil composition for internal combustion engines according to claim 1, having a HTHS viscosity at 150° C. of 2.3 mPa·s or more and 2.9 mPa·s or less.

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