Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic compound containing boron
Reexamination Certificate
2001-05-30
2003-05-27
Howard, Jacqueline V. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic compound containing boron
C508S291000, C508S375000, C508S378000, C508S460000, C508S574000
Reexamination Certificate
active
06569818
ABSTRACT:
This application claims priority from Japanese Patent Application Number 2000-166774, filed Jun. 2, 2000.
The present invention relates to a lubricating oil composition favorably employable for lubricating internal combustion engines such as diesel engines, gasoline engines, and gas engines. In particular, the invention relates to a lubricating oil composition having a low sulfated ash content, a low phosphorus content, and a low sulfur content, while showing good detergency at high temperatures.
BACKGROUND OF THE INVENTION
Diesel internal combustion engines mounted on motor-driven vehicles, constructions machines and power generators are generally driven using gas oil or heavy oil (which is a fuel having a sulfur content of approximately 0.05 wt. % or more). Most lubricating oils for the diesel engines have a sulfated ash content of approx. 1.3 to 2 wt. %, a sulfur content of approx. 0.3 to 0.7 wt. %, a phosphorus content of approx. 0.1 to 0.13 wt. %, and a chlorine content of 50 to 100 ppm (wt.) or more.
As for internal combustion engine-mounted vehicles, particularly, diesel engine-mounted vehicles, it is required to find ways of meeting problems to obviate environmental pollution caused by the exhaust gas components such as particulate and nitrous oxides (NO
x
). For obviating such environmental pollution, it is proposed to mount exhaust gas-clearing devices containing a particulate filter and oxidizing catalysts and/or NO
x
reducing catalysts on the vehicles. The combination of the particulate filter and oxidizing catalysts can trap the soot produced and then oxidize and burn the trapped soot. However, metal oxides, sulfates and carboxylates produced by burning of conventional lubricating oil are apt to plug the filter.
Sulfur contained in the fuel is also converted to sulfuric acid and sulfates which emigrate into exhaust gas. Sulfuric acid and sulfate lower activity of the oxidizing catalysts and/or NO
x
reducing catalysts in the exhaust gas-cleaning device. In turn, the sulfur content of fuel should be decreased. Accordingly, it is expected that requirements for decreasing the sulfur content of diesel fuel from the present value of approx. 0.05 wt. % to 0.01 wt. % or lower, and perhaps even further to approx. 0.001 wt. % or lower may be required.
As the sulfur content of fuel is decreased, the content of metal-containing detergent (which functions to neutralize the produced sulfuric acid) in the lubricating oil will also be decreased. The lubricating oil is employed for lubricating the engine parts, but a portion of the lubricating oil is burnt and emigrates into the exhaust gas. Therefore, the decrease in content of the metal-containing detergent, which means decrease of a metal content and a sulfur content, is favorable for decreasing environmental pollution. Moreover, it is preferred to decrease the phosphorus content in the lubricating oil so as to keep the oxidizing catalyst from deterioration. The content of chlorine in the lubricating oil should also be as low as possible, so as to decrease production of dioxins.
Japanese Patent No. 2,922,675 describes an ashless lubricating oil composition favorably employable for diesel engines in combination with fuels of a low sulfur content, which contains specific amounts of an alkylester of (3,5-di-t-butyl-4-hydroxyphenol)carboxylic acid, an ashless succinimide type dispersant, and an ashless amine type or phenol type oxidation inhibitor.
U.S. Pat. No. 5,102,566 describes a low sulfated ash lubricating oil composition which comprises a base oil, at least about 2 wt. % of an ashless nitrogen- or ester-containing dispersant, an oil-soluble antioxidant material, and an oil soluble dihydrocarbyl dithiophosphate anti-wear material, and which has a total sulfated ash (SASH) level of 0.01 to 0.6 wt. % and a weight ratio of SASH to dispersant in the range of 0.01:1 to 0.2:2.
Japanese Patent Provisional Publication No. 8-48989 describes a lubricating oil composition which has a low sulfated ash content and does not disturb functions of particulate traps and oxidizing catalysts, but shows good stability at high temperatures so that it can meet the anticipated exhaust gas regulations. The disclosed lubricating oil composition comprises at least 5 wt. % of a boron-containing ashless dispersant, 0.05 to 0.15 wt. % (in terms of phosphorus content) of zinc thiophosphate, and optionally 0.01 to 2 wt. % of an ashless oxidation inhibitor, under such conditions that the boron content in the composition is at least 0.1 wt. %, the boron content/phosphorus content ratio is at least 0.8, and the sulfated ash content is at most 1.0 wt. %.
SUMMARY OF THE INVENTION
The present invention provides a lubricating oil composition which has a low sulfur content, a low phosphorus content and a low sulfated ash content, and does not disturb functions of particulate traps and oxidizing catalysts and/or NO
x
reducing catalysts, while having stability at high temperatures so that it can meet the anticipated exhaust gas regulations.
It is well known to those skilled in the art that decreases of the sulfur content, phosphorus content, and sulfated ash content in the lubricating oil composition result in lowering of high temperature stability of the lubricating oil composition.
It has now been discovered that the lowering of the high temperature stability of the lubricating oil composition by the decreases of the sulfur content, phosphorus content, and sulfated ash content can be compensated using a small amount of a metal-containing detergent having a certain amount of soap content, namely, a content of an organic acid metal salt component is contained, in combination with an ashless dispersant, zinc dialkyldithiophosphate, and an oxidation inhibitor.
In its broadest aspect, the present invention resides in a lubricating oil composition having a sulfur content of 0.01 to 0.3 wt. % and a phosphorus content of 0.01 to 0.1 wt. %, and giving a sulfated ash in the range of 0.1 to 1 wt. %, which comprises
a) a major amount of a mineral base oil having a sulfur content of at most 0.1 wt. %;
b) an ashless dispersant comprising an alkenyl- or alkyl-succinimide or a derivative thereof in an amount of 0.01 to 0.3 wt. % in terms of a nitrogen atom content;
c) a metal-containing detergent containing an organic acid metal salt which is selected from the group consisting of a non-sulfurized alkali metal or alkaline earth metal salt of an alkylsalicylic acid having a TBN of 10 to 350 mg·KOH/g and a non-sulfurized alkali metal or alkaline earth metal salt of an alkylphenol derivative having a Mannich base structure, in an amount of 0.1 to 1 wt. % in terms of a sulfated ash content;
d) a zinc dialkyldithiophosphate in an amount of 0.01 to 0.1 wt. % in terms of a phosphorus content; and
e) an oxidation inhibitor selected from the group consisting of a phenol compound and an amine compound in an amount of 0.01 to 5 wt. %.
The lubricating oil composition of the present invention preferably has a sulfur content of 0.01 to 0.15 wt. %, a phosphorus content of 0.01 to 0.06 wt. %, and a chlorine content of at most 40 ppm (more preferably at most 30 ppm).
The ashless dispersant employed in the lubricating oil composition of the present invention preferably is a succinimide or a derivative thereof which is obtained by the reaction of a polybutenylsuccinic anhydride and a polyamine, the polybutenylsuccinic anhydride being produced from polybutene and maleic anhydride by a thermal reaction method using neither chlorine or a chlorine atom-containing compound.
The metal-containing detergent in the lubricating oil composition of the present invention preferably is a non-sulfurized alkali metal or alkaline earth metal salt of an alkylsalicylic acid having a TBN of 30 to 300 mg·KOH/g, more preferably 30 to 100 mg·KOH/g. The metal-containing detergent is chosen and incorporated into the lubricating oil composition under the condition that the organic acid metal salt (i.e., soap content) originating from the metal-containing detergent is in an amount of 0.2 to 7 wt. %, more preferably 0.5 to
Hirano Satoshi
Iwamoto Shigeru
Nakazato Morikuni
Chevron Oronite Company LLC
Howard Jacqueline V.
Lee S. G. K.
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