Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic compound containing boron
Reexamination Certificate
2001-01-30
2003-09-30
Medley, Margaret (Department: 1714)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic compound containing boron
C508S363000, C508S364000, C508S365000
Reexamination Certificate
active
06627583
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an engine oil composition, and more particularly to an engine oil composition useful as a lubricating oil for gasoline engines, diesel engines, and the like.
2. Description of the Related Art
Because of increased concern regarding the energy-saving measures to counter oil shocks, the research for a fuel-saving internal combustion engine lubricating oil has been recently intensified. As measures for fuel-saving by use of lubricating oil to meet such a situation, the following measures are now under review among business circles: (a) lowering viscosity of lubricating oil with the intention of reducing engine friction loss under hydrodynamic lubricating conditions, and (b) addition of friction reducers with the intention of reducing engine friction loss under mixed and boundary lubrication.
Addition of friction modifiers to lubricating oil is indispensable especially in the latest fuel-saving lubricating oil, and many compounds have heretofore been found to be useful. However, it has been observed that even though these compound possess a high fuel-saving effect on the fresh lubricating oil, they gradually lose said effect in the aged lubricating oil due to degradation during engine operation. While many antioxidants have widely been used heretofore and proved to be effective to some extent for preventing the degradation, they could not necessarily provide satisfactory results in view of their lubricating performance.
For example, an engine oil composition comprising over-based borated metal salts are known from U.S. Pat. No. 4,539,126 corresponding to Japanese Patent Laid-open Publication No. 60-116688. This publication discloses that an antiwear such as zinc dithiophosphates or an antioxidant such as amine type or phenol type antioxidant may be added into this composition. However, even if an antioxidant and/or zinc dithiophosphate, which are given as an optional additive in this patent, are combined and employed, the friction coefficient of the engine oil is insufficiently high for the purpose. In general, an antiwear is an additive having a function of preventing wear of sliding surfaces. On the contrary, a friction modifier is an additive having a function of decreasing a friction coefficient of sliding surfaces, and thus its function is quite different from that of an antiwear.
Furthermore, over-based borated metal salts are known from U.S. Pat. No. 4,683,126 corresponding to Japanese Patent Laid-open Publication No. 61-204298, however, the friction coefficient of the engine oil when employing only such an additive is insufficiently high.
In addition, engine oil compositions comprising sulfur-phosphorus type additive and molybdenum dithiophosphates are known from U.S. Pat. No. 3,925,213, however, the friction coefficient of the engine oil employing such an additive is insufficiently high after oxidative degradation, and thus fuel-saving effect may be very low.
The present invention is based on a discovery that excellent fuel-saving effect can be attained employing an overbasic metallic detergent prepared by use of an alkaline earth metal borate as an additional component of an engine oil composition containing at least one molybdenum dithiocarbamate and an antioxidant.
The present invention provides an engine oil composition having a specific combination of lubricating additives and excellent fuel-saving effect over a long period of time.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a fuel-saving engine oil composition comprising a major amount of lubricating base oil and as essential components, on the basis of the total weight of that composition,
(a) 0.01 to 30% by weight of an overbasic oil-soluble metal salt which is the reaction product of an oil-soluble metal salt with an alkaline earth metal oxide or hydroxide in the presence of boric acid or boric acid anhydride,
(b) 0.01 to 5% by weight of a molybdenum dithiocarbamate, and
(c) 0.01 to 5% by weight of an antioxidant selected from the group consisting of phenolic, amino, sulfur, zinc thiophosphate and phenothiazine type antioxidants.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Either mineral oils or synthetic oils may be used as the lubricating base oils of the present invention. Any paraffinic or naphthenic lubricating base oils may be acceptable wherein said base oils are manufactured by a process consisting mainly of topping crude oil followed by vacuum distillation to give a lubricating oil fraction, and refining said lubricating fraction by at least one process selected from the group consisting of solvent deasphalting, solvent extraction, hydro-cracking, solvent dewaxing, catalytic dewaxing, hydro-refining, sulfuric acid treating, and clay treating.
The synthetic oils of the present invention include, &agr;-olefin polymers (polybutenes, octene1 oligomers, decene-1 oligomers and the like) or hydrogenated derivatives thereof, alkylbenzenes, alkylnaphthalenes, diesters (ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecy adipate, ditridecyl adipate, di-3-ethylhexyl sebacate, and the like), polyol esters (trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate, and the like), polyoxyalkylene glycol, polyphenyl ether, silicon oils, perfluoroalkyl esters, and mixtures thereof.
Preferred kinematic viscosity of these lubricating base oils is in a range of 3 to 20 cSt at 100° C.
The overbasic oil-soluble metal salts (a) of the present invention are prepared by a reaction of an oil-soluble metal salt such as an oil-soluble alkaline-earth metal sulfonate, oil-soluble alkaline-earth metal salicylate, oil-soluble alkaline-earth metal phenate, oil-soluble alkaline-earth metal phenate, oil-soluble alkaline-earth metal phosphate with an oxide or hydroxide of an alkaline-metal in the presence of boric acid or boric acid anhydride. Among alkaline-earth metal, magnesium, calcium and barium are appropriately used, and calcium is most appropriate. Among oil-soluble metal salts, oil-soluble alkaline-earth metal salicylates are most appropriate. The overbasic oil-soluble metal salt is a dispersion where a produced alkaline-earth metal borate is dispersed by assist of oil-soluble metal salt. Generally, the overbasic oil-soluble metal salts (a) of the present invention have a total base number (so-called “TBN”) of a lower limit of 100, and preferably 170, and of an upper limit of 400, and preferably 300. A particle size of the alkaline-earth metal borate in the overbasic oil-soluble metal salt is less than 0.1 &mgr;m, and preferably less than 0.05 &mgr;m.
Any methods for preparing the overbasic metal salts may be acceptable. For example, a method has been known which comprises reacting an oil-soluble metal salt aforesaid, a hydroxide or an oxide of alkaline-earth metal, and boric acid or boric acid anhydride in the presence of water, an alcohol such as methanol, ethanol, propanol, or butanol, and a diluent such as benzene, toluene or xylene at a temperature of 20 to 200° C. for 2 to 8 hours, heating the mixture at 100 to 200° C. to remove water, followed by removing the alcohol and the diluent if necessary, to give an overbasic metal salt. The reaction conditions may be employed suitably depending on raw material type, the amount of reactants and the like. Typical of such prior art practices are those disclosed in Japanese Patent Publication No. 61-204298 corresponding to U.S. Pat. No. 4,683,126 and the disclosures of which are incorporated herein by reference.
The content of the overbasic metal salt prepared by use of an alkaline-earth metal borate of the present invention is in an amount of a lower limit of 0.01, and preferably 0.05% by weight and of an upper limit of 30% by weight, and preferable 5% by weight, on the basis of the total amount of the composition.
The content of less than the lower limit is not preferable because of the insufficient display of the fuel-saving effect of the overbasic metal salt wherein the effect can not be mainta
Hirata Masakuni
Igarashi Jinichi
Inoue Kiyoshi
Ishimaru Mituaki
Kagaya Mineo
Medley Margaret
Nippon Mitsubishi Oil Corporation
Ostrolenk Faber Gerb & Soffen, LLP
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