JP4964014B2 - Engine oil composition - Google Patents

Description

The present invention relates to an engine oil composition, and more particularly, to an engine oil composition having a low sulfated ash content, a low sulfur content, and a low phosphorus content and having excellent wear prevention performance.

  Currently, two methods for commercial vehicle exhaust gas purification have been put to practical use. One method suppresses the generation of nitrogen oxides by improving combustion, and removes particulate matter using a diesel particulate filter and an oxidation catalyst. The other method suppresses the generation of particulate matter by high-temperature combustion. Then, nitrogen oxides are reduced and removed by the urea selective reduction method.

  As for passenger cars, cars that comply with exhaust gas regulations have not yet been released in Japan, but there is a possibility that cars corresponding to this will be released after 2009 when exhaust gas regulations become more stringent. Mounting devices expected for exhaust gas purification include a diesel particulate filter and an oxidation catalyst for removing particulate matter, and an occlusion reduction catalyst or a urea reduction catalyst for nitrogen oxide removal.

Among these, for diesel particulate filters, metal components such as calcium and zinc contained in engine oil may become ash and cause clogging of the filter. It is required to be ash.
On the other hand, since the storage reduction catalyst used for removing nitrogen oxides is poisoned by sulfur, it is necessary to reduce the sulfur content in the engine oil as much as possible. In addition, it is said that the urea reduction catalyst has a catalyst activity that is reduced by adsorption of phosphorus on the surface, and it is necessary to reduce phosphorus in engine oil as well as sulfur.

Thus, engine oils are required to reduce metal content (ie, ash content), sulfur content, and phosphorus content. As one of the countermeasures, it has been studied to reduce the amount of zinc dialkyldithiophosphate containing zinc, sulfur and phosphorus in the molecule. However, when the amount of zinc dialkyldithiophosphate is reduced, the anti-wear performance decreases. Therefore, for example, a technique of using a zinc dialkyldithiophosphate having a short-chain alkyl group having a higher wear-preventing effect or a technique of using another antiwear agent in combination with reducing the zinc dialkyldithiophosphate is proposed ( For example, see Patent Document 1).

JP 2004-155881 A

When a zinc dialkyldithiophosphate having a short-chain alkyl group is blended, the anti-wear performance is very good at a normal blending amount, that is, about 1.0% by mass, but at a half blending amount, a certain amount Although a wear prevention effect can be obtained, in the JASO valve wear test having a sliding type valve system, the amount of cam wear increases, and the wear surface becomes rough (pitching) (see Comparative Example 5 described later). There is.

For this reason, in engine oils with low ash content, low sulfur content, and low phosphorus content, it is required to consider wear prevention properties such as suppression of cam wear and anti-pitting performance. That is, in addition to a zinc dialkyldithiophosphate having a short-chain alkyl group, it is desirable to add an additive having a cam wear-inhibiting amount and a pitching prevention performance.

  As a result of intensive studies in view of the above situation, the present inventor has obtained a short-chain alkyl group having a high antiwear property, that is, a dialkyldithiophosphoric acid having an alkyl group having 3 to 5 carbon atoms, in an engine oil containing a base oil. Formulated with zinc dialkyldithiophosphate by using zinc as a low ash, low sulfur and low phosphorus engine oil that combines molybdenum dithiocarbamate, glycerin fatty acid partial ester and alkyl alkanolamide in specific proportions The present invention has been completed by finding that the amount of the engine oil can be reduced and the engine oil can be excellent in wear prevention performance.

That is, the present invention is a base oil and (A) molybdenum dithiocarbamate of formula (1), wherein R ^{1 to} R ⁴ are alkyl groups having 8 to 13 carbon atoms , and at least ^one of R ^{1 to} R ⁴ One is an alkyl group having 13 carbon atoms, and at least one of R ^{1 to} R ⁴ is an alkyl group having 8 to 12 carbon atoms , molybdenum dithiocarbamate is 50 to 400 mass ppm in terms of molybdenum, (B) glycerol mono 0.5 to 0.9 % by mass of isostearate , (C) an alkanolamide of the formula (2), wherein R ⁵ is a saturated aliphatic hydrocarbon group having 10 to 16 carbon atoms, R ⁶ , R ⁷ is an alkyl alkanolamide which is a saturated aliphatic hydrocarbon group having 2 to 3 carbon atoms , 0.1 to 2.0% by mass, and (D) having an alkyl group having 3 to 5 carbon atoms of formula (3) Dialkyldithiophosphoric acid A lead, as a whole collection of each molecule content of zinc dialkyldithiophosphate of the secondary alkyl group having 3 carbon atoms, 25 mol% or more of the total alkyl groups, and 3 carbon atoms is 60 mol% or less Containing 0.5 to 0.6% by mass of a zinc dialkyldithiophosphate having an alkyl group of ˜5, a sulfated ash content of 1.1% by mass or less, a sulfur content of 0.2% by mass or less, and phosphorus of 0.05% by mass. An engine oil composition characterized by being less than or equal to mass% is provided.

  The engine oil composition of the present invention can prevent clogging of a diesel particulate filter and poisoning of a nitrogen oxide reduction catalyst, and is excellent in wear prevention performance, in particular, can suppress cam wear and prevent pitting of the wear surface. be able to.

In the engine oil composition of the present invention, the base oil is one or more base oils selected from mineral oil base oils and synthetic lubricant base oils.
Examples of mineral oil base oils include those obtained by refining crude oil lubricating oil fractions in appropriate combinations such as solvent refining, hydrorefining, hydrocracking refining, and isomerization.
Examples of synthetic lubricating base oils include α-olefin oligomers, dialkyl diesters, polyols, alkyl benzenes, polyglycols, phenyl ethers, and the like.

In order to further reduce the sulfur content in the composition of the engine oil, it is preferable that the sulfur content of the base oil is smaller in order to reduce the sulfur content derived from the base oil. However, in the present invention, as an additive blended for preventing wear, the components (A) to (D) are particularly selected and the blending ratio is optimized, while maintaining the wear preventing effect sufficiently. Since the amount of sulfur content derived from the additive to the engine oil is kept to a minimum, an engine oil composition having a low sulfur content can be obtained. For example, when the sulfur content in the base oil is less than 0.05% by mass, the sulfur content of the engine oil of the present invention can be easily adjusted to 0.2% by mass or less.

In addition, the sulfur content of this base oil is a sulfur content after mixing all the base oil components when using a plurality of base oil components. Therefore, according to the present invention, an inexpensive base oil having a relatively high sulfur content (for example, a base oil classified as Group I in the API base oil classification), a base oil having a low sulfur content but a high price ( For example, in the case of using a base oil mixed with a base oil classified into groups II and III in the base oil classification of API, there is an advantage that a large amount of the former base oil having a high sulfur content can be used.

（式中、Ｒ^１〜Ｒ^４は炭素数８〜１３のアルキル基であり、Ｒ ^１ 〜Ｒ ^４ の少なくとも１つは炭素数１３のアルキル基であり、Ｒ ^１ 〜Ｒ ^４ の少なくとも１つは炭素数８〜１２のアルキル基であり、Ｘ及びＹは、硫黄原子又は酸素原子を示す。） (A) component of the molybdenum dithiocarbamate is Ru der a structure of the following formula (1).

^(Wherein, R 1 to R ⁴ is an alkyl group having 8 to 13 carbon atoms, at least one of ^R 1 to R ⁴ is an alkyl group of 13 carbon ^atoms, at least one of R 1 to R ⁴ is (It is a C8-12 alkyl group, and X and Y show a sulfur atom or an oxygen atom.)

  Although the content rate of molybdenum dithiocarbamate is 50-400 mass ppm in conversion of molybdenum, Preferably it is 100-300 mass ppm, Most preferably, it is 150-250 mass ppm. If it is less than 50 ppm by mass, it is impossible to sufficiently compensate for the wear resistance reduced due to the reduction of zinc dialkyldithiophosphate, and a sufficient wear prevention effect cannot be obtained. Then, pitching on the wear surface is likely to occur. On the other hand, even if it exceeds 400 ppm by mass, there is no inconvenience in terms of the complementary effect of the anti-wear property reduced by the reduction of zinc dialkyldithiophosphate, but the sulfur content in the engine oil composition increases due to the sulfur contained in the molecule. Therefore, it is difficult to adjust the low-sulfur engine oil composition. In addition, the sulfur content in the engine oil composition is the sum of the sulfur content derived from the additive and the sulfur content derived from the base oil. The proportion of the Group I base oil with a high sulfur content is limited, which is economically disadvantageous.

Component (B), Ru glycerol monoisostearate der.

The content ratio of glycerol monoisostearate is 0.5 to 0.9% by mass. If it is less than 0.3% by mass, a sufficient wear prevention effect, particularly a sufficient cam wear suppression effect cannot be obtained. Moreover, even if it mixes exceeding 2.0 mass%, the effect corresponding to a mixing | blending ratio will not be acquired.

(C) alkyl alkanolamide ingredients, Ru der those of the formula (2) below.

In the formula (2), R ⁵ is a saturated aliphatic hydrocarbon group having 10 to 16 carbon atoms, and may be linear or branched . R ⁶ and R ⁷ are saturated aliphatic hydrocarbon groups having 2 to 3 carbon atoms, which may be linear or branched, and may be different or the same, but preferably both Have the same structure and 2 to 3 carbon atoms. Further, the position at which the hydroxyl group is coordinated to R ⁶ and R ⁷ may be the terminal or not.
The content of the alkyl alkanolamide is 0.1 to 2.0% by mass, preferably 0.2 to 1.5% by mass, and particularly preferably 0.3 to 1.0% by mass. If it is less than 0.2% by mass, a sufficient wear preventing effect, particularly a sufficient cam wear suppressing effect cannot be obtained. Moreover, even if it mixes exceeding 2.0 mass%, the effect corresponding to a mixing | blending ratio will not be acquired.

(D) zinc dialkyldithiophosphate components, Ru der those of the formula (3) below.

In formula (3), R ^{8 to} R ¹¹ are alkyl groups having 3 to 5 carbon atoms, and may be primary alkyl groups or secondary alkyl groups.
When the carbon number of R ^{8 to} R ¹¹ is 3 to 5, the decomposability of the zinc dialkyldithiophosphate molecule is increased, and a chemical film is easily formed on the metal surface serving as the wear surface. In order to obtain a higher anti-wear effect is preferably at least one of secondary alkyl groups R ⁸ to R ^11, and even more at least one secondary alkyl of 3 carbon atoms R ⁸ to R ¹¹ It is preferably a group . The content ratio of the secondary alkyl group having 3 carbon atoms in the zinc dialkyldithiophosphate is 25 mol% or more of the total alkyl groups as a whole as an aggregate of each molecule of the zinc dialkyldithiophosphate, more preferably 30 mol. der least% is, can exhibit particularly good anti-wear properties. The upper limit of the content of the secondary alkyl group having 3 carbon atoms in the zinc dialkyl dithiophosphate is less 60 mole% of the total alkyl groups.

The content ratio of zinc dialkyldithiophosphate is 0.3 to 0.6% by mass, preferably 0.4 to 0.6% by mass, and particularly preferably 0.45 to 0.55% by mass. When the content ratio exceeds 0.6% by mass, the sulfur content and phosphorus in the engine oil composition may exceed the range of the present invention, which is not preferable. On the other hand, when the content ratio is less than 0.3% by mass, a chemical film derived from zinc dialkyldithiophosphate cannot be formed on the metal surface, and good wear prevention performance cannot be obtained.

A metal type detergent can be mix | blended with the engine oil composition of this invention.
As the metallic detergent, calcium salicylate, calcium phenate, calcium sulfonate, or the like can be used.
As the calcium salicylate, those having a base number measured by the perchloric acid method of JIS K2501 (hereinafter sometimes simply referred to as “base number”) of 60 mgKOH / g or more are preferably used. Particularly preferred is 230 mg KOH / g.

The calcium phenate preferably has a base number of 150 mgKOH / g or more, and particularly preferably has a base number of 200 to 300 mgKOH / g.
From the viewpoint of extending the life of engine oil, calcium salicylate having a base number of 170 mgKOH / g or more may be used as the calcium detergent. In addition, calcium phenate having a base number of 250 mgKOH / g or more is used in combination, and the blending amount of calcium salicylate is preferably 50% to 90% of the total base number of calcium salicylate and calcium phenate in terms of base number. Since calcium salicylate has a high basification retention ability, the reduction of the base number can be maintained over a long period of time by setting it to 50% or more. On the other hand, by making the calcium salicylate 90% or less, that is, by making the calcium phenate 10% or more, the effect of the calcium phenate with excellent dispersibility of soot makes the filter blockage and dirt on each part of the engine more effective. Can be suppressed.

Since calcium sulfonate has poor base number retention, a low ash oil is not preferable because the oil life is shortened.
The blending amount of the detergent is 1.0 to 11.0% by mass of salicylate having a base number of 60 mgKOH / g or more. Moreover, it converts from 1.1 mass% or less of sulfated ash, and 0.24 mass% or less is preferable as calcium conversion.

The sulfated ash content in the engine oil composition of the present invention is preferably 1.1% by mass or less from the viewpoint of preventing clogging of the diesel particulate filter for a long period of time. Here, the sulfated ash is measured according to JIS K2272.
The sulfur content in the engine oil composition of the present invention is preferably 0.2% by mass or less from the viewpoint of preventing poisoning of the nitrogen oxide reduction catalyst, and the phosphorus content is used to prevent poisoning of the urea reduction catalyst. From the viewpoint, it is preferably 0.05% by mass or less.

Various additives can be further blended into the engine oil composition of the present invention as desired. As various additives, additives that are effective for imparting engine oil performance such as dispersants, ashless antioxidants, pour point depressants, viscosity index improvers, and antifoaming agents are blended as necessary. be able to.
Specific examples of the dispersant include alkenyl succinimides and boron compound derivatives of alkenyl succinimides.
Ashless antioxidants include phenolic antioxidants, amine antioxidants, polymethacrylates as pour point depressants, viscosity index improvers such as polymethacrylates, olefin copolymers, and chemical blends of polymethacrylates and olefin copolymers. Can be mentioned.

Next, this invention is demonstrated based on an Example and a comparative example. In addition, this invention is not restrict | limited at all by these examples.
Example 1
The components described in Table 1 were mixed at the content ratio to obtain a composition. The evaluation result of the obtained composition is shown in the lower part of Table 1. In Table 1, the unit of the blending amount is mass%.
(Comparative Examples 1-5)
The components described in Table 1 were mixed at the content ratio to obtain a composition. The evaluation results of the obtained composition are shown in the lower part of Table 1.

The numbers in parentheses in Table 1 are shown below.
1) Base oil: A base oil obtained by mixing a Group I base oil having a sulfur content of 0.1% by mass, a Group II base oil having a sulfur content of 0.01% by mass, and a Group III base oil having a sulfur content of 0.0001% by mass. .
2) Molybdenum dithiocarbamate: Molybdenum dithiocarbamate in which R ^{1 to} R ^{4 in} formula (1) are an alkyl group having 8 and 13 carbon atoms and having a Mo content of 4% by mass was used. In Example 1, the molybdenum dithiocarbamate content in terms of molybdenum is 200 ppm by mass.
3) Alkylalkanolamide: In the formula (3), R ⁵ is an alkyl group having 10 carbon atoms, R ⁶ and R ⁷ are alkyl groups having 2 carbon atoms, and a hydroxyl group is bonded to the terminal.
4) Zinc dialkyldithiophosphate: 30 mol% of a secondary alkyl group having 3 carbon atoms, 30 mol% of a primary alkyl group having 4 carbon atoms, and 40 mol% of a primary alkyl group having 5 carbon atoms.

5) Cleaner: Formulated with calcium salicylate with a perchloric acid method base number of 170 mgKOH / g and calcium phenate with a perchloric acid method base number of 250 mgKOH / g. The compounding amount of calcium salicylate is 80% of the total base number of calcium salicylate and calcium phenate in terms of perchloric acid base number. 6) Succinimide: 1300 in terms of PIB mass.
7) B-containing succinimide: 2100 in terms of PIB mass was used.

8) The maximum non-seizure load (N) was determined by a modified method of JPI-5S-40-93 “Testing method for load resistance of lubricating oil (shell four-ball type)”.
Testing machine: Shell four-ball load capacity tester
Test conditions: Rotate for 60 seconds at 1800 rpm. 9) JASO M354 “Automotive diesel engine lubricating oil – valve train wear test method”
The mixing ratio of each base oil in 4D34T4 engine manufactured by Mitsubishi Motors Corporation, 160 hour test Example 1 and Comparative Examples 1 to 5 is shown in Table 2 in volume%.

In the friction modifier composition, amide alone (Comparative Example 3) and molybdenum dithiocarbamate (Comparative Example 4) alone showed low values of maximum non-seizure load. Glycerol monostearate alone (Comparative Example 1), a combination of glycerol monoisostearate and alkyl diethanolamide (Comparative Example 2) and a combination of molybdenum dithiocarbamate, glycerol monoisostearate and alkyl diethanolamide of the present invention (implementation) In all cases, the maximum non-seizure load was high.
When compositions having a high maximum non-seizure load were evaluated by the JASO valve system wear test, the average cam wear amount satisfied DH-2 and DL-1 standards of 95 μm or less. However, other than the present invention (Comparative Examples 1 to 5), pitting occurred on the surface of the cam, and the overall evaluation was a failure.

Claims (2)

Base oil and (A) molybdenum dithiocarbamate of formula (1), wherein R ^{1 to} R ⁴ are alkyl groups having 8 to 13 carbon atoms, and at least one of R ^{1 to} R ⁴ has 13 carbon atoms And at least one of R ^{1 to} R ⁴ is molybdenum dithiocarbamate, which is an alkyl group having 8 to 12 carbon atoms, in an amount of 50 to 400 ppm by mass in terms of molybdenum, and (B) glycerol monoisostearate is 0. 5 to 0.9 % by mass, (C) an alkanolamide of the formula (2), wherein R ⁵ is a saturated aliphatic hydrocarbon group having 10 to 16 carbon atoms, and R ⁶ and R ⁷ are 2 to 2 carbon atoms. 3 is a dialkyldithiophosphate zinc having 0.1 to 2.0% by mass of an alkylalkanolamide which is a saturated aliphatic hydrocarbon group 3 and (D) an alkyl group having 3 to 5 carbon atoms of the formula (3). Carbon number Content of secondary alkyl group as a whole collection of each molecule of zinc dialkyldithiophosphate, dialkyl having 25 mol% or more, and the alkyl group having 3 to 5 carbon atoms is 60 mol% or less of the total alkyl groups It contains 0.3 to 0.6% by mass of zinc dithiophosphate, sulfate ash content is 1.1% by mass or less, sulfur content is 0.2% by mass or less, and phosphorus is 0.05% by mass or less. An engine oil composition.

(In the formula, R ^{8 to} R ¹¹ are alkyl groups having 3 to 5 carbon atoms.) The zinc dialkyldithiophosphate is a zinc dialkyldithiophosphate having an alkyl group having 3 to 5 carbon atoms of the formula (3) of the component (D), and the content ratio of the secondary alkyl group having 3 carbon atoms is a dialkyldithiophosphate. 2. The engine according to claim 1, wherein the aggregate of each molecule of zinc is only a zinc dialkyldithiophosphate having an alkyl group having 3 to 5 carbon atoms that is 25 mol% or more and 60 mol% or less of all alkyl groups. Oil composition.