JP5170637B2 - Long-life fuel-saving engine oil composition - Google Patents

Description

  The present invention relates to a long-life fuel-saving engine oil that has excellent oxidation stability at high temperatures and low friction for a long time and has excellent high-temperature oxidation stability.

In recent years, there has been a great demand for improving the fuel efficiency of automobiles and suppressing CO ₂ emissions to prevent global warming. Engine efficiency is important for improving the fuel efficiency of automobiles, and lean burn and direct injection technologies are used in gasoline engines. On the other hand, reducing the friction of the engine can also contribute to the improvement of fuel efficiency, so the use of low-friction materials for sliding parts and the adoption of fuel-saving engine oil are being attempted.

  In order to produce fuel-saving engine oil, an additive (friction) that reduces friction and reduces the viscosity to 5W-20 or 0W-20 according to the viscosity classification stipulated in SAE (American Automobile Engineering Association) J300. It is known that it is effective to blend an organic molybdenum-based FM such as molybdenum dithiocarbamate (MoDTC) as a regulator (hereinafter also referred to as FM) (see Non-Patent Document 1).

Because lean burn and direct injection engines are more efficient than conventional engines, the combustion temperature tends to rise, and pistons are exposed to higher temperatures, so it is necessary to improve the high-temperature oxidation stability of engine oil. is there. That is, future fuel-saving engine oils will require fuel-saving engine oils that are superior to conventional ones due to high-temperature oxidation stability.
On the other hand, MoDTC deteriorates with use and disappears from the oil. Therefore, the fuel saving effect by MoDTC deteriorates with use, and the improvement of the sustainability of this fuel saving effect is also an important issue.
Japanese Patent Laid-Open No. 10-17883 K. Hoshino et al, Fuel Efficiency of SAE 5W-20 Friction Modifired GasolineEngine Oil, SAE Technical Paper 982506 (1998)

  In view of the above situation, an object of the present invention is to provide an engine oil that is excellent in high-temperature oxidation stability and further excellent in fuel-saving sustainability.

  As a result of diligent research to solve the above-mentioned problems, the present inventors have formulated a specific ratio of a combination of a specific antioxidant and a mineral oil and / or a synthetic base oil, and a MoDTC of a certain amount or more. It has been found that the composition obtained by blending is useful as a long-life fuel-saving engine oil having good high-temperature oxidation stability. The present invention has been made based on such findings.

That is, the present invention contains a mineral oil and / or synthetic base oil containing 1.2 mass% or more of an amine antioxidant and a phenolic antioxidant in total, and the nitrogen content of the amine antioxidant ( N) to the oxygen content (O) of the phenolic antioxidant (mass: N / O) is 0.20 to 0.50, and molybdenum dithiocarbamate (MoDTC) is 0.5% molybdenum (Mo). It is an engine oil composition containing 055% by mass or more.
In particular, the total amount of amine antioxidant and phenolic antioxidant is 1.5% by mass or more, and the nitrogen content of amine antioxidant (N) and the oxygen content of phenolic antioxidant (O ) (Mass: N / O) is 0.20 to 0.35, and molybdenum dithiocarbamate (MoDTC) is preferably contained in molybdenum (Mo) at 0.055% by mass or more.

  Since the long-life fuel-saving engine oil composition of the present invention has the above-described configuration, it is excellent in high-temperature oxidation stability, has little viscosity increase even when used for a long period of time, and maintains low friction for a long period of time. It is a long-life, fuel-saving engine oil that exhibits exceptional effects. Therefore, it can be suitably used for an internal combustion engine, particularly a gasoline engine engine such as lean burn or direct injection, and exhibits a special effect that fuel efficiency is improved and that it lasts for a long time.

As the base oil used in the engine oil composition of the present invention, any of mineral oil, synthetic base oil, and mixtures thereof can be used. The kinematic viscosity at 100 ° C. is preferably 3.5 to 5.0 mm ² / s, particularly 4.0 to 4.5 mm ² / s. As a viscosity index, 110-160, especially 120-140 are preferable. As the mineral oil, a high viscosity index lubricating base oil having a viscosity index of 120 or more is desirable. A high viscosity index lubricating base oil having a viscosity index of 120 or more can be obtained by solvent dewaxing or hydrodewaxing a product oil obtained by hydroisomerization of wax or hydrocracking of heavy oil. . One example of these production methods will be described more specifically below.

The hydroisomerization of wax is from wax having a boiling range of 300 to 600 ° C. and a carbon number of 20 to 70, such as slack wax obtained in a solvent dewaxing step of mineral oil-based lubricating oil, hydrocarbon gas, etc. Using a wax obtained by Fischer-Tropsch synthesis for synthesizing a liquid fuel as a raw material, a hydroisomerization catalyst, for example, a group 8 metal such as nickel and cobalt on an alumina or silica-alumina carrier, and 6A such as molybdenum and tungsten. A catalyst supporting one or more of group metals, a zeolite catalyst, or a catalyst supporting platinum or the like on a zeolite-containing carrier, a temperature of 300 to 450 ° C. in the presence of hydrogen at a hydrogen partial pressure of 5 to 14 MPa, 0.1 to 0.1 It can be performed by contacting at 2 hr ⁻¹ LHSV (liquid space velocity). At this time, it is preferable that the conversion rate of the linear paraffin is 80% or more and the conversion rate to the light fraction is 40% or less.

On the other hand, in the hydrocracking, if necessary, hydrodesulfurization and denitrogenation are performed at a normal pressure distillate, a vacuum distillate or bright stock having a boiling point in the range of 300 to 600 ° C. 350 to 450 in the presence of hydrogen having a hydrogen partial pressure of 7 to 14 MPa, a catalyst supporting one or more of group 8 metals such as nickel and cobalt and one or more of group 6A metals such as molybdenum and tungsten on an alumina support. At a temperature of 0.1 ° C. and an LHSV (liquid hourly space velocity) of 0.1 to 2 hr ⁻¹ , and the decomposition rate (mass% reduced in the fraction of 360 ° C. or higher in the product) is 40 to 90 % Is preferable.

Lubricating oil fraction can be obtained by distilling off the light fraction from the hydroisomerized product oil or hydrocracked product oil obtained by the above method, but this fraction generally has a high pour point and viscosity. and the viscosity index is not high enough, perform dewaxing treatment, to remove the wax fraction, n-d-M ring analysis% C _P is 80 or more, a pour point viscosity index at -10 ° C. or less More than 120 lubricating base oils can be obtained.

  When removing the wax by solvent dewaxing, the light fraction is distilled off using a precision distillation apparatus, and the fraction having a boiling point of 371 ° C. or higher and lower than 491 ° C. by gas chromatography distillation is previously used. Is preferably 70% by mass or more in order to perform the solvent dewaxing process more efficiently. In this solvent dewaxing treatment, for example, methyl ethyl ketone / toluene (volume ratio 1/1) is used as a dewaxing solvent, and the solvent / oil ratio is in the range of 2/1 to 4/1. It is good to do.

On the other hand, when the wax content is removed by hydrodewaxing, distilling the light fractions should not hinder hydrodewaxing, and after hydrodewaxing, they are separated by distillation using a precision distillation apparatus. It is efficient and preferable that the fraction having a boiling point of 371 ° C. or higher and lower than 491 ° C. is 70% by mass or higher by gas chromatography distillation. This hydrodewaxing is carried out by contacting the zeolite catalyst with hydrogen at a partial pressure of 3 to 15 MPa at a temperature of 320 to 430 ° C. and a LHSV (liquid space velocity) of 0.2 to 4 hr ^−1. The pour point in the lubricating base oil should be −10 ° C. or lower.

  A lubricating base oil having a viscosity index of 120 or more can be obtained by the method as described above, but solvent purification or hydrorefining can be further performed as desired.

Synthetic oils include α-olefin oligomers, diesters synthesized from dibasic acids such as adipic acid and monohydric alcohols, polyhydric alcohols such as neopentyl glycol, trimethylolpropane, pentaerythritol, and monobasic acids. Polyol esters synthesized from the above, and mixtures thereof.
Furthermore, a mixed oil combining an appropriate mineral oil and a synthetic oil can also be used as the base oil of the engine oil.

式中、Ｒ^１〜Ｒ^４は、炭素数４〜１８個を有する直鎖及び／又は分岐のアルキル基及び／又はアルケニル基を表し、Ｘは酸素原子又は硫黄原子を表し、その酸素原子と硫黄原子との比は１／３〜３／１である。Ｒ^１〜Ｒ^４は、好ましくはアルキル基であり、特に好ましくは炭素数８〜１４の分岐のアルキル基であり、具体的にはブチル基、２−エチルヘキシル基、イソトリデシル基、ステアリル基等が挙げられる。１分子中に存在する４個のＲ^１〜Ｒ^４は、同一であってもよく、異なっていてもよい。また、Ｒ^１〜Ｒ^４の異なるＭｏＤＴＣを２種以上混合して用いることもできる。
ＭｏＤＴＣの含有量は、エンジン油全重量に対して、ＭｏＤＴＣに含まれるモリブデン（Ｍｏ）金属元素重量で０.０５５質量％以上であり、特には０.０５５〜０．１２質量％、さらには０.０６〜０．１０質量％が好ましい。MoDTC used for the engine oil of the present invention is represented by the following general formula (1).

In the formula, R ^{1 to} R ⁴ represent a linear and / or branched alkyl group and / or alkenyl group having 4 to 18 carbon atoms, X represents an oxygen atom or a sulfur atom, and the oxygen atom and sulfur The ratio with the atoms is 1/3 to 3/1. R ^{1 to} R ⁴ are preferably alkyl groups, particularly preferably branched alkyl groups having 8 to 14 carbon atoms, and specific examples include a butyl group, a 2-ethylhexyl group, an isotridecyl group, and a stearyl group. It is done. Four R < ¹ > -R < ⁴ > which exists in 1 molecule may be the same, and may differ. Also, two or more kinds of MoDTCs having different R ^{1 to} R ⁴ can be mixed and used.
The content of MoDTC is 0.055% by mass or more in terms of the weight of molybdenum (Mo) metal element contained in MoDTC with respect to the total weight of engine oil. 0.06 to 0.10% by mass is preferable.

式（２）において、Ｒ^５は、炭素数が３以上２０以下の炭化水素基が好ましく、特に好ましい炭化水素基としてはオクチル基、ステアリル基が挙げられる。As the antioxidant used in the engine oil of the present invention, both a phenolic antioxidant and an amine antioxidant are used.
As a phenolic antioxidant suitably used for the engine oil of the present invention, a phenolic compound having an antioxidant ability and having a substituent containing an ester bond can be used. Examples include compounds represented by the general formulas (2) and (3).

In Formula (2), R ⁵ is preferably a hydrocarbon group having 3 to 20 carbon atoms, and particularly preferred hydrocarbon groups include octyl and stearyl groups.

式（４）の化合物は、一般的には、Ｎ−フェニルベンゼンアミンとアルケンとを反応させて得られる化合物である。式（４）において、Ｒ^６、Ｒ^７は、炭化水素基であり、各ベンゼン環で５個ずつ、合計１０個置換しえるが、少なくとも１個以上置換しているものが好ましい。炭化水素基の炭素数は３以上２０以下が好ましく、Ｒ^６とＲ^７の合計が複数の場合、それぞれは同じ炭化水素基であっても異なっていてもよい。より好ましくは、ブチル基からノニル基までの直鎖又は分枝鎖のアルキル基が挙げられる。The amine-based antioxidant suitably used in the engine oil of the present invention is preferably diphenylamine and / or phenylnaphthylamine having antioxidant ability. Specifically, in the following general formulas (4) and (5) And the compounds represented.

The compound of the formula (4) is generally a compound obtained by reacting N-phenylbenzenamine with an alkene. In the formula (4), R ⁶ and R ⁷ are hydrocarbon groups, and each benzene ring can be substituted by five, for a total of ten, but at least one is preferably substituted. The number of carbon atoms of the hydrocarbon group is preferably 3 or more and 20 or less. When the sum of R ⁶ and R ⁷ is plural, each may be the same hydrocarbon group or different. More preferred is a linear or branched alkyl group from a butyl group to a nonyl group.

式（５）において、Ｒ^８〜Ｒ^９は、炭素数が３以上２０以下の炭化水素基であり、式（５）にはナフチル基及びフェニル基の両方に置換されているように記しているが、少なくともどちらか一方の基に１個以上置換されているものでも、両方の基にそれぞれ１個ずつ以上置換されているものでもよい。Ｒ^８〜Ｒ^９がそれぞれ複数個の場合、それぞれは同一であっても、異なっていてもよい。なお、Ｒ^８〜Ｒ^９は炭素数が６以上１２以下のアルキル基が好ましく、直鎖又は分枝鎖のオクチル基ないしノニル基で、ナフチル基又はフェニル基のどちらか一方に１個置換されているものが特に好ましい。
また、アミン系酸化防止剤としては、一般式（４）及び（５）で表される化合物を混合して用いることができる。

In the formula (5), R ^{8 to} R ⁹ are hydrocarbon groups having 3 to 20 carbon atoms, and the formula (5) is described as being substituted with both a naphthyl group and a phenyl group. However, at least one group may be substituted by one or more, or both groups may be substituted by one or more. When there are a plurality of R ^{8 to} R ⁹ , each may be the same or different. R ^{8 to} R ⁹ are preferably an alkyl group having 6 or more and 12 or less carbon atoms, and is a linear or branched octyl group or nonyl group, one of which is substituted on either the naphthyl group or the phenyl group. It is particularly preferable.
Moreover, as an amine antioxidant, the compound represented by General formula (4) and (5) can be mixed and used.

  The total content of phenolic antioxidants and amine antioxidants is 1.5% by mass or more, and the nitrogen content (N) of the amine antioxidant and the oxygen content (O) of the phenolic antioxidant The mass ratio (N / O) is preferably from 0.20 to 0.35, particularly preferably from 0.25 to 0.30. The total content of the antioxidants is preferably 1.5% by mass or more, particularly preferably 1.5 to 3% by mass. If the total is less than 1.5% by mass, the target high-temperature oxidation stability cannot be obtained, for example, high-temperature oxidation stability of, for example, a viscosity increase rate of 150% or less, particularly 0 to 100% in the Sequence III G test. Further, if the ratio of the nitrogen mass of the amine antioxidant and the oxygen mass of the phenol antioxidant is less than 0.20, the target high-temperature oxidation stability cannot be obtained. On the other hand, if the ratio of the nitrogen mass of the amine-based antioxidant and the oxygen mass of the phenol-based antioxidant exceeds 0.35, the low friction life by the target MoDTC cannot be obtained.

  In the engine oil of the present invention, if desired, detergents such as zinc alkyldithiophosphate (ZnDTP), Ca, Mg, Ba and Na, sulfonates, phenates and salicylates, and ashless dispersants such as alkenyl succinimides In addition, additives such as viscosity index improvers, pour point depressants, metal deactivators, rust inhibitors and antifoaming agents can be added.

Next, the present invention will be described specifically by way of examples.
As the base oil, a mineral oil base oil (kinematic viscosity: 20.3 mm ² / s (40 ° C.)) obtained by hydrodewaxing a product oil obtained by hydrocracking heavy oil, and 4. 34 mm ² / s (100 ° C.), viscosity index 124) was used.

  Example 1 and Comparative Examples 1 to 1 were blended with the base oil in the proportions shown in Table 1 with phenolic antioxidant A, amine antioxidant B, MoDTC and other additives described below as additives. Three engine oils were prepared. Table 1 also shows the ratio (mass: N / O) of the nitrogen content (N) of the added amine antioxidant and the oxygen content (O) of the phenolic antioxidant and the Mo content. The other additive is an additive mixture consisting of zinc alkyldithiophosphate (ZnDTP), Ca sulfonate, alkenyl succinimide, viscosity index improver, pour point depressant and antifoaming agent, and all examples and comparative examples. The same amount was added in common.

Phenol-based antioxidant A: A phenol-based antioxidant (oxygen content 12.3 mass%) represented by the general formula (2) and having the substituent R ⁵ as an octyl group was used.
Amine-based oxidizing agent B: An amine-based antioxidant (nitrogen content 4.5% by mass), which is a reaction product of N-phenylbenzeneamine and 2,4,4-trimethylpentene, was used.
MoDTC: A compound represented by the general formula (1), in which R ^{1 to} R ⁴ are a mixture of a 2-ethylhexyl group and an isotridecyl group and the ratio of oxygen atom to sulfur atom is 1/1.

  About each of the engine oil of the Example of Table 1, and the comparative example, the Sequence III G test was implemented and engine oil performance was evaluated. Among them, there is an item for evaluating the high-temperature oxidation stability by the viscosity increase rate, and the viscosity increase rate of 150% or less is specified as an acceptance criterion (Suzuki, latest trend of gasoline engine oil standards, monthly tribology, 2003.5, Page 17). For each of the above test engine oils, the rate of increase in viscosity was determined by comparing the engine oil 100 hours after the engine test with the engine oil at the start of the engine test (0 hour) according to the Sequence III G test. The results are shown in Table 2.

  Further, for each of the test engine oils shown in Table 1, an engine test, which is a bench durability test, and an SRV friction test for measuring friction are performed under the following conditions, and the test time at which the friction coefficient of the engine oil becomes 0.070 And the sustainability of fuel consumption was evaluated by comparing with standard oil (test time of 165 hours when the friction coefficient becomes 0.070, travel distance corresponding to this time of 10,000 km). The results are shown in the lower part of Table 2 as the low friction durability life (km).

Engine test conditions -Engine: Displacement 2L Inline 6-cylinder gasoline engine-Oil pan capacity: 3.4L reduced to 2L (test severity was accelerated)
・ Oil pan oil temperature: 100 ℃
・ Test mode: AMA running mode (repeated)
・ Oil sampling: Every 24 hours (sample for SRV friction test)

SRV friction test conditions / contact conditions: cylinder on block ・ Sliding conditions: load 400N, frequency 50 Hz, amplitude 1.5 mm, temperature 120 ° C.
The test time until the friction coefficient of engine oil reaches 0.070 is obtained by interpolating the sampling times of two samples with a friction coefficient of 0.070 between samples sampled every 24 hours (used engine oil). It was. Based on the test time until the friction coefficient of 0.070 obtained is 0.070 and the standard oil friction coefficient of 0.070 (165 hours) and the running distance of 10,000 km, the low friction durability life ( Traveling distance, km) was determined.

  As is clear from the above results, the total amount of amine-based antioxidant and phenol-based antioxidant added to the mineral oil and / or synthetic base oil shown in the examples is 1.5% by mass or more, and the amine-based The ratio (N / O) of the nitrogen mass (N) of the antioxidant and the oxygen mass (O) of the phenolic antioxidant is 0.20 to 0.35, and further MoDTC is 0.3 by Mo content. An engine oil composition containing 055% by mass or more has a low viscosity increase rate of 83% in the Sequence III G test and is expected to have good high-temperature oxidation stability. Furthermore, since the MoDTC low friction sustaining life calculated from the SRV friction test of the oil used in the engine durability test is as long as 9000 km or more, it can be seen that the fuel saving sustainability is also excellent.

  On the other hand, the engine oil composition of Comparative Example 1 to which only the phenolic antioxidant is added has a long low friction life, but has a very large viscosity increase rate and is inferior in high-temperature oxidation stability. Further, Comparative Example 2 having a high ratio of nitrogen content of amine-based antioxidant and oxygen content of phenol-based antioxidant is excellent in oxidation stability but inferior in low friction life. Furthermore, it can be seen that Comparative Example 3 in which the blending amount of MoDTC is reduced is larger in viscosity increase rate and inferior in high-temperature oxidation stability than in Example 1, and inferior in low friction life.

Claims (1)

Mineral oil and / or synthetic base oil contains an amine antioxidant and a phenolic antioxidant represented by the following general formula (2) or (3) in a total amount of 1.5 % by mass or more, and is amine-based ratio of the oxygen content of the nitrogen content of the antioxidant (N) and the phenolic antioxidant (O) (weight: N / O) is from 0.20 to 0.35, further molybdenum dithiocarbamate car Pas mate ( A long-life fuel-saving engine oil composition characterized by containing 0.055% by mass or more of MoDTC) in molybdenum (Mo).

[In the formula (2), R ⁵ is a hydrocarbon group having 3 to 20 carbon atoms]