JP2008024845A - Engine oil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide engine oil having excellent fuel cost-decreasing effect. <P>SOLUTION: This engine oil has (A) ≥1.5 and <2.9 mPa s shear viscosity at 150°C temperature and 1×10<SP>6</SP>sec<SP>-1</SP>shear speed, and (B) <4.5 mPa s shear viscosity at 150°C temperature and 6×10<SP>4</SP>to 9×10<SP>4</SP>sec<SP>-1</SP>shear speed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an engine oil having an excellent fuel consumption reduction effect.

  In recent years, as a response to environmental problems such as global warming, an effect of reducing fuel consumption has been demanded for engine oil. As a technique for solving this problem, a low-viscosity oil that contains an organic molybdenum compound and has a reduced coefficient of friction in the boundary lubrication region has been found (see, for example, Patent Document 1). Moreover, in addition to reducing the friction coefficient in the boundary lubrication region by the organic molybdenum compound, a low-viscosity oil that has a fuel-saving effect in the fluid lubrication region by blending a specific ester-based lubricant base oil has been found ( Patent Document 2).

Furthermore, by combining a specific antioxidant, a low-viscosity oil having an excellent fuel saving effect without compounding an organic molybdenum compound has been found (see Patent Document 3). Commercially available engine oils include low-viscosity oils such as API viscosity grades 5W-30, 5W-20, and 0W-20, and low-viscosity oils blended with organic molybdenum compounds as fuel-saving oils.

However, in order to further improve the fuel efficiency of the engine, it is important to further reduce the friction between the boundary lubrication region and the fluid lubrication region. In particular, despite all shear rates occurring in the engine, conventional engine oils have a 150 ° C. HTHS (High
Only the high-temperature viscosity was noted.

JP-A-8-302378 Japanese Patent Laid-Open No. 2005-41998 JP-A-2005-42070

An object of the present invention is to provide an engine oil having an excellent fuel consumption reduction effect.

  As a result of diligent studies to achieve the above object, the present inventor exhibits a friction reduction effect in the fluid lubrication region by making the shear viscosity in a specific shear rate region a specific range, and is excellent. Based on this finding, the present invention has been completed.

That is, the present invention has (A) a temperature of 150 ° C., a shear viscosity in the vicinity of 1 × 10 ⁶ sec ^{−1 of} 1.5 mPa · s or more and less than 2.9 mPa · s, and (B) a temperature of 150 ° C. An engine oil having a shear viscosity of less than 4.5 mPa · s at a shear rate of 6 × 10 ^{4 to} 9 × 10 ⁴ sec ⁻¹ is provided.

Further, the present invention provides the above engine oil containing an organic molybdenum compound, having a molybdenum concentration in the engine oil of 200 to 1000 ppm, a phosphorus concentration of 0.1% by mass or less, or a sulfur concentration of 0.4% by mass or less. It provides engine oil. Thus, the present invention provides an engine oil that exhibits a further excellent fuel saving effect by having a friction reducing effect in the boundary lubrication region.

Further, the present invention provides an engine oil that is advantageous to an exhaust gas purification catalyst by controlling the NOACK evaporation amount of the engine oil to 15% by mass or less in the engine oil, thereby suppressing the oil consumption. is there. Furthermore, the present invention provides an engine oil having a viscosity characteristic in which the SAE viscosity grade is 0W-20, 5W-20 or less in the engine oil.
Viscosity characteristics below these are kinematic viscosities at 100 ° C. (kinematic viscosity in ASTM D 445 of 5.6 or less) lower than viscosity grade 20 of SAE J300, or HTHS viscosities (viscosity in ASTM D 4683 is less than 2.6). Say to show.

The engine oil of the present invention has excellent fuel economy performance. The engine oil of the present invention can maintain the fuel saving effect in the fluid lubrication region over a long period of time.
Furthermore, the engine oil of the present invention can obtain an excellent fuel saving effect in the boundary lubrication region and achieve both fuel saving performance in the boundary lubrication region and the fluid lubrication region by using a friction modifier such as an organic molybdenum compound. it can. The organomolybdenum compound is 200 to 1000 ppm as the amount of molybdenum in the engine oil, and the phosphorus concentration is 0.1% by mass or less, or the sulfur concentration is 0.4% by mass or less. Further, by suppressing the NOACK evaporation amount to 15% by mass or less, poisoning given to the exhaust gas purification catalyst can be reduced.

The engine oil of the present invention has (A) a shear viscosity at a temperature of 150 ° C. and a shear rate of about 1 × 10 ⁶ sec ^{−1 of} 1.5 mPa · s or more and less than 2.9 mPa · s, preferably 1.6 mPa · s. s or more and less than 2.9 mPa · s, more preferably 1.7 mPa · s or more and less than 2.9 mPa · s. This shear viscosity is a shear viscosity around 1 × 10 ⁶ sec ⁻¹ obtained by ASTM D4683 or ASTM D5481. In the case of ASTM D4683, the vicinity means preferably within ± 3%, more preferably within ± 2.5%, and in the case of ASTM D5481, preferably 1.35 × 10 ^It means ^{6 to} 1.45 × 10 ⁶ sec ⁻¹ , more preferably 1.38 × 10 ^{6 to} 1.42 × 10 ⁶ sec ⁻¹ . In particular, in an engine oil having SAE viscosity grades having viscosity characteristics of 0 W-20 and less than 5 W-20, 1.7 mPa · s or more and less than 2.5 mPa · s are preferable, and 1.8 mPa · s or more and 2. Less than 4 mPa · s is preferable.

Further, the engine oil of the present invention (B) needs to have a shear viscosity of less than 4.5 mPa · s in the range of (B) temperature 150 ° C. and shear rate 6 × 10 ^{4 to} 9 × 10 ⁴ sec ⁻¹ . , Preferably 2.5 mPa · s or more and less than 4.5 mPa · s, particularly preferably 3.0 mPa · s or more and less than 4.5 mPa · s. (B) The shear viscosity at a temperature of 150 ° C. and a shear rate of 6 × 10 ^{4 to} 9 × 10 ⁴ sec ⁻¹ can be measured using, for example, a Multicell Capillary Viscometer according to ASTM D5481. In particular, in an engine oil having SAE viscosity grades with viscosity characteristics of 0W-20 and less than 5W-20, 3.0 mPa · s or more and less than 4.0 mPa · s are preferable, and 3.3 mPa · s or more and 4. Less than 0 mPa · s is preferable.

γ = 4V / tπr ³ (1)

The shear rate can be determined by equation (1), where γ is the shear rate (sec ⁻¹ ), V is the sample volume (cm ³ ), t is the time for the total amount of sample to pass through the capillary tube (sec), π represents a circular ratio, and r represents a capillary tube radius (cm). For example, when the sample volume V is 8.8235 cm ³ and the capillary tube radius r is 0.0075 cm, the shear rate is 6 × 10 ^{4 to} 9 by adjusting the pressure of the tester so that t is 296 to 444 sec. The shear viscosity in the range of × 10 ⁴ sec ⁻¹ can be determined. The shear rate needs to be in the range of 6 × 10 ^{4 to} 9 × 10 ⁴ sec ⁻¹ , and preferably 6 × 10 ⁴ to 8 × 10 ⁴ sec ⁻¹ .

μ = 9.8 × 10 ⁷ × rP / 2Lγ (2)

The shear viscosity can be determined by the equation (2), μ is the shear viscosity (mPa · s), r is the capillary tube radius (cm), P is the pressure (kg / cm ² ), L is the capillary tube length (cm), γ represents the shear rate (sec ⁻¹ ) given by equation (1). For example, using a sample volume V of 8.8235 cm ³ , a capillary tube radius r of 0.0075 cm, a capillary tube length L of 1.72 (cm), and measuring the shear viscosity at a pressure P of 1.5 kg / cm ² , When the time t when the total amount of the sample passes through the capillary tube is 380 (sec), the shear rate is 7.0 × 10 ⁴ sec ⁻¹ from the equation (1), and the shear viscosity is 4.57 mPa from the equation (2). Calculated as s.

The shear viscosity need not be in the range of less than 4.5 mPa · s at all points of the shear rate in the range of 6 × 10 ^{4 to} 9 × 10 ⁴ sec ^−1. Any one of the speeds may be less than 4.5 mPa · s. This also applies to the shear viscosity of (A).
What is important is that at a temperature of 150 ° C., the shear viscosity at a shear rate of about 1 × 10 ⁶ sec ⁻¹ is 1.5 mPa · s or more and less than 2.9 mPa · s, and the shear rate is 6 × 10 ^{4 to} 9. It is important that the shear viscosity at × 10 ⁴ sec ⁻¹ is less than 4.5 mPa · s. Outside these ranges, there is a risk of increased friction in the fluid lubrication region and the boundary fluid region in the engine, and the excellent fuel saving effect of the present invention cannot be realized.

  The above-described method for achieving the present invention minimizes the increase in viscosity due to various additives added to the base oil in order to ensure the practical performance of the engine oil, and falls within the range of (A) and (B) of the present invention. The viscosity index improver may be adjusted according to the added amount of the viscosity index and the viscosity of the base oil.

The viscosity index improver is not particularly limited. For example, various known viscosity index improvers such as polymethacrylate, ethylene propylene copolymer, styrene-isoprene copolymer, hydride of styrene-isoprene copolymer, or polyisobutylene. May be used singly or in combination of two or more. The addition amount of the viscosity index improver and the viscosity of the base oil can be adjusted as appropriate to fall within the scope of the present invention. The addition amount of the viscosity index improver is preferably 0 to 20 parts by mass, particularly preferably 0 to 15 parts by mass with respect to 100 parts by mass of the base oil. The weight average molecular weight of the viscosity index improver is preferably 30,000 to 800,000, more preferably 50,000 to 600,000, and particularly preferably 100,000 to 500,000. The weight average molecular weight is as follows: device: TOSOH HLC-8020, column: TSKgel GMHHR-M, detector: suggested refraction detector, mobile phase: THF, flow rate: 1 ml / min, sample concentration: about 1.0 mass % / Vol%
It is a polystyrene conversion value measured by THF, injection amount: 50 μl.
A preferable viscosity index as an engine oil is 120 to 250, and more preferably 130 to 240.

  The engine oil of the present invention preferably has a sulfur concentration (JPI-5S-38-2003) of 0.4% by mass or less, more preferably 0.01% by mass or more and 0.4% by mass or less. Especially preferably, it is 0.05 mass% or more and 0.35 mass% or less, More preferably, it is 0.1 mass% or more-0.3 mass% or less. Moreover, it is preferable that phosphorus concentration (JPI-5S-38-2003) is 0.1 mass% or less, More preferably, it is 0.01 mass% or more and 0.1 mass% or less. If the phosphorus concentration or sulfur concentration is low, the amount of a sulfur-based additive such as zinc dialkyldithiophosphate that functions as an abrasion resistance improver is limited, and there is a concern about a decrease in abrasion resistance. Further, when the phosphorus concentration or sulfur concentration is high, the sulfur oxide derived from engine oil in the exhaust gas increases, and there is a concern about an adverse effect on the exhaust gas purification catalyst.

As a suitable method for bringing the engine oil of the present invention into the above-mentioned preferable phosphorus concentration and sulfur concentration ranges, for example, zinc dialkyldithiophosphate is limited to an appropriate amount that ensures wear resistance, and a base oil with low sulfur content, for example, Base oil and GTL (Gas) classified into Group II, Group III, Group IV and Group V in the base oil category defined by the American Petroleum Institute
to Liquid) or the like, or a combination of two or more.

Moreover, even if it is a base oil with a high sulfur content such as Group I, the above-mentioned preferable sulfur can be obtained by using it in combination with one or more of Group II, Group III, Group IV and Group V or GTL base oil. Can be in the minute range.
In addition, it is preferable to select a base oil so as to suppress NOACK (ASTM D 5800) evaporation to 15% by mass or less in order to suppress as much as possible the amount of phosphorus and sulfur that are poisoned to the exhaust gas catalyst. . In order to suppress the amount of NOACK evaporation, it is possible to make the appropriate range by selecting one or two or more of Group II, Group III, Group IV, Group V and GTL base oil.

In order to achieve both the friction reduction effect in the boundary lubrication region in the engine oil of the present invention, an organic molybdenum compound is preferable, and there are molybdendithiophosphate, molybtendithiocarbamate, molybdate amine compound, molybdenum long chain aliphatic amine, and the like. . It is preferable to use it so that the molybdenum concentration in the engine oil is 200 mass ppm or more and 1000 mass ppm or less. More preferably, it is 400 mass ppm or more and 1000 mass ppm or less. If it is small, a sufficient friction reducing effect cannot be expected, and if it is too large, there is a concern that it adversely affects engine cleanliness. In order to reduce friction, a friction modifier containing no metal such as a long-chain aliphatic acid, a long-chain aliphatic acid ester, or a long-chain aliphatic alcohol can also be used.

The viscosity of the base oil is such that the kinematic viscosity at 40 ° C. (JIS-K-2283-5) is usually 5 to 100 mm ² / s, preferably 10 to 80 mm ² / s, particularly preferably. It is 12-50 mm < ² > / s. Further, the kinematic viscosity at 100 ° C. (JIS-K-2283-5) is preferably ^{2 to} 8 mm ² / s, more preferably 3 to 7 mm ² / s, and particularly preferably 3.5 to ⁶ mm ² / s. s. The viscosity index (JIS-K-2283-6) of the base oil is preferably 80 to 250, particularly preferably 90 to 180.

As the base oil, it is possible to use various mineral oil base oils having the above kinematic viscosity and viscosity index, synthetic base oils, or base oils made of a mixture thereof.
The SAE viscosity grade in the present invention is a classification defined in SAE J300, and is preferably 0W-20 or 5W-20 in order to exert an excellent fuel saving effect even when the oil temperature is low. Further, it may be 2.6 or less, which is outside the regulation of SAW J300 0W-20 and 5W-20 HTHS.

The kinematic viscosity as an engine oil may be a kinematic viscosity at 40 ° C. (JIS-K-2283-5), usually 10 to 55 mm ² / s, preferably 15 to 50 mm ² / s. Preferably it is 18-50 mm < ² > / s. Further, the kinematic viscosity at 100 ° C. (JIS-K-2283-5) is preferably 3 to 10 mm ² / s, more preferably 3.5 to 9.5 mm ² / s, and particularly preferably 4 to 9. .3 mm ² / s. The viscosity index (JIS-K-2283-6) as engine oil is preferably 100 to 250, and particularly preferably 120 to 250.

  The engine oil of the present invention is not limited to a gasoline engine engine, a diesel engine engine, and a gas engine engine, but preferably a gasoline engine engine is suitable.

  In the engine oil of the present invention, various known additives such as alkaline earth metal sulfonates, alkaline earth metal phenates, alkaline earth metal salicylates, alkalines are used as necessary, as long as the object of the present invention is not impaired. Metal detergents such as earth metal phosphonates; Other ashless dispersants such as alkenyl succinimides, benzylamines, alkylpolyamines, ester compounds, viscosity index improvers with polar groups; Phosphorus, sulfur, amines Various antiwear agents such as esters, alkylphenols such as 2,6-di-tert-butyl-p-cresol, bisphenols such as 4,4′-methylenebis- (2,6-di-t-butylphenol) N-octadecyl-3- (4′-hydroxy-3 ′, 5′-di-tert-butylphenol) propio Various antioxidants such as phenolic compounds such as carbonates, aromatic amine compounds such as naphthylamines and dialkyldiphenylamines, organic molybdenum compounds such as amine molybdates; sulfurized olefins, sulfurized fats and oils, methyltrichlorostearate, chlorinated naphthalene, Extreme pressure agents such as benzyl iodide, fluoroalkylpolysiloxane, lead naphthenate; carboxylic acids including stearic acid, dicarboxylic acids, metal soaps, carboxylic acid amine salts, heavy sulfonic acid metal salts, polyhydric alcohols Various rust inhibitors such as carboxylic acid partial esters and phosphate esters; various corrosion inhibitors such as benzotriazole, benzimidazole and thiadiazole polysulfide; various antifoaming agents such as silicone oil, etc., alone or in combination of two or more Mix as appropriate It is possible.

The amount of other additives other than the viscosity index improver is preferably as small as possible, and is preferably 20% by mass or less. More preferably, it is 15% by mass or less.
In the method for preparing the engine oil of the present invention, the base oil and the various additives added as necessary may be appropriately mixed, and the order of mixing is not particularly limited.

Next, the present invention will be described in more detail with reference to examples and comparative examples. However, the present invention is not limited in any way by these examples.
Evaluation test methods used in Examples and Comparative Examples are as follows.
(1) Shear viscosity at a temperature of 150 ° C. and a shear rate of 1 × 10 ⁶ sec ⁻¹ The shear viscosity was measured by ASTM D4683.

(2) Shear viscosity at a temperature of 150 ° C. and a shear rate of 6 × 10 ^{4 to} 9 × 10 ⁴ sec ⁻¹ Measured using a Multicell Capillary Viscometer according to ASTM D5481. The capillary cell used has a sample volume of 8.8235 cm ³ , a capillary tube radius of 0.0075 cm, a capillary tube length of 1.72 cm, and a shear rate of 6 × 10 ^{4 to} 9 × 10 ⁴ sec ⁻¹ . The pressure was adjusted so that the time t during which the total amount of the sample passed through the capillary tube was in the range of 296 to 444 sec so as to fall within the range. The shear rate and the shear viscosity were calculated by the above-described equations (1) and (2), respectively.

(3) Sulfur concentration It was measured by JPI-5S-38-2003.
(4) Phosphorus concentration Measured according to JPI-5S-38-2003.
(5) Molybdenum concentration It measured by JPI-5S-38-2003.
(6) NOACK evaporation amount Measured according to ASTM D 5800.
(7) Judged according to the classification defined in SAE viscosity grade SAE J300.

(8) Fuel consumption test A 660cc engine in Japan was used. The following test conditions were used. Condition 1 was an engine speed of 2100 rpm, an oil temperature of 80 ° C., and an engine torque of 2 N · m. Condition 2 was an engine speed of 2600 rpm, an oil temperature of 85 ° C., and an engine torque of 33 N · m. Condition 3 was an engine speed of 2900 rpm, an oil temperature of 85 ° C., and an engine torque of 13 N · m. The fuel consumption reduction rate (%) was obtained by comparison with the fuel consumption rate of the reference oil under each test condition. Furthermore, the average value was calculated from the fuel consumption reduction rate under each test condition.

(Examples 1-5)
As the base oil, it has a kinematic viscosity of 40 ° C., a kinematic viscosity of 100 ° C., and a viscosity index shown in Table 2, and the base oil is blended with the amount shown in Table 2 in addition to the viscosity index improver. Additives (Ca-based detergent, alkenyl succinimide-based dispersant, zinc dialkyldithiophosphate as a wear resistance improver, organic molybdenum compound, antioxidant, etc.) in the amounts shown in Table 2, Oil was produced.
The viscosity index improver was adjusted by polymethacrylate in Example 1, and Examples 2, 3, 4 and 5 were prepared by mixing types of polymethacrylate and ethylene propylene copolymer.

(Comparative Examples 1-3)
As the base oil, it has a kinematic viscosity of 40 ° C., a kinematic viscosity of 100 ° C. and a viscosity index shown in Table 3, and the base oil is blended with the amount shown in Table 3 in addition to the viscosity index improver. Additives (Ca-based detergent, alkenyl succinimide-based dispersant, zinc dialkyldithiophosphate as a wear resistance improver, organic molybdenum compound, antioxidant, etc.) in the amounts shown in Table 3 Oil was produced. Comparative Example 2 is an engine oil that passes the commercially available API / ILSAC standard SL / GF-3.
The viscosity index improvers of Comparative Examples 1 and 3 were adjusted according to the mixed type of polymethacrylate and ethylene propylene copolymer.
Tables 2 and 3 show the composition, properties, and test results of the engine oils of the examples and comparative examples of the present invention. In the fuel consumption test, the fuel consumption reduction rate was obtained using Comparative Example 3 as a reference oil.

As is clear from Tables 2 and 3, the engine oils of Examples 1 to 5 are more fuel efficient under all fuel economy test conditions of Conditions 1 to 3 than the engine oil of Comparative Example 3 which is a reference oil. It turns out that it is excellent. On the other hand, like the engine oil of Comparative Example 1 and Comparative Example 2, the shear viscosity at a shear rate of 1 × 10 ⁶ sec ⁻¹ and 6 × 10 ^{4 to} 9 × 10 ⁴ sec ⁻¹ at a temperature of 150 ° C. If it is out of the range, a large fuel saving effect as shown in Examples 1 to 5 cannot be found. It turns out that it is inferior to Examples 1-5 also in the average of conditions 1-3.
As described above, an excellent fuel saving effect can be realized only when the present invention is satisfied.

Claims (4)

(A) Temperature is 150 ° C., shear viscosity in the vicinity of 1 × 10 ⁶ sec ⁻¹ is 1.5 mPa · s or more and less than 2.9 mPa · s, and (B) Temperature is 150 ° C. and shear rate is 6 × 10. Engine oil having a shear viscosity of less than 4.5 mPa · s at ^{4 to} 9 × 10 ⁴ sec ⁻¹ . The engine oil according to claim 1, wherein the engine oil has a phosphorus concentration of 0.1 mass% or less, or a sulfur concentration of 0.4 mass% or less, further contains an organic molybdenum compound, and has a molybdenum concentration of 200 to 1000 ppm. . The engine oil according to claim 1 or 2, wherein the NOACK evaporation amount of the engine oil is adjusted to 15 mass% or less. The engine oil according to any one of claims 1 to 3, wherein the SAE viscosity grade of the engine oil has a viscosity characteristic of 0W-20, 5W-20, or less.