Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic compound containing boron
Reexamination Certificate
1994-04-04
2003-03-11
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
C508S373000, C508S375000, C508S376000, C508S378000
Reexamination Certificate
active
06531428
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to improved lubricating oils, especially internal combustion engine lubricating oils, and additives and additives mixtures employable for the preparation of such lubricating oils.
Automobile spark ignition and diesel engines have valve train systems, including valves, cams and rocker arms which present special lubrication concerns. It is extremely important that the lubricant, i.e. the engine oil, protects these parts from wear. Further, it is important for engine oils to suppress the production of deposits in the engines. Such deposits are produced from non-combustibles and incomplete combustibles of hydrocarbon fuels (e.g., gasoline, diesel fuel oil) and by the deterioration of the engine oil employed.
Engine oils use a mineral oil or a synthetic oil as a base oil. However, simple base oils alone do not provide the necessary properties to provide the necessary wear protection, deposit control, etc. required to protect internal combustion engines. Thus, base oils are formulated with various additives, for imparting auxiliary functions, such as ashless dispersants, metallic detergents (i.e., metal-containing detergents), antiwear agents, antioxidants (i.e., oxidation inhibitors), viscosity index improvers and the like to give a compounded oil (i.e., a lubricating oil composition).
A number of such engine oil additives are known and employed in practice. Zinc dialkyldithiophosphates are, for example, because of their favorable characteristics as an antiwear agent and performance as an oxidation inhibitor, contained in most all of the commercially available internal composition engine oils, especially those used for automobiles.
However, a problem has arisen with respect to the use of zinc dialkyldithiophosphate, because phosphorous derivatives poison catalyst components of catalytic converters. This is a major concern, because effective catalytic converters are needed to reduce pollution and to meet governmental regulation designed to reduce toxic gases, such as hydrocarbons, carbon monoxide, and nitrogen oxides, in internal combustion engine exhaust emission. Such catalytic converters generally use a combination of catalytic metals, such as platinum or variations, and metal oxides and are installed in the exhaust streams, e.g., the exhaust pipes of automobiles, to convert the toxic gases to nontoxic gases. As before mentioned these catalyst components are poisoned by the phosphorous component, or the phosphorous decomposition products of the zinc dialkyldithiophosphate; and accordingly, the use of engine oils containing phosphorous additives may substantially reduce the life and effectiveness of catalytic converters. Therefore, it would be desirable to reduce the phosphorous content in the engine oils so as to maintain the activity and extend the life of the catalytic converter.
There is also governmental and automotive industry pressure towards reducing phosphorous content; for example, United States Military Standards MIL-L-46152E and the ILSAC Standards defined by the Japanese and United States Automobile Industry Association require engine oils to have phosphorous content below 0.12 wt. %. The phosphorous content in most high grade engine oils containing zinc dialkyldithiophosphate is approximately 0.1 wt. %, and thus meet the 0.12 wt % requirement. Nevertheless, it would be desirable to decrease the amount of zinc dialkyldithiophosphate in lubricating oils still further, thus reducing catalyst deactivation and hence increasing the life and effectiveness of catalytic converters. However, simply decreasing the amount of zinc dialkyldithiophosphate presents problems because this necessarily lowers the antiwear properties and oxidation inhibition properties of the lubricating oil. Therefore, it is necessary to find a way to reduce phosphorous content while still retaining the antiwear and oxidation or corrosion inhibiting properties of the higher phosphorous content engine oils.
In order to compensate for lowering the amount of zinc dialkyldithiosphate, the use of other oxidation inhibitors such as phenol derivatives and amine derivatives have been studied. However, the use of such known oxidation inhibitors in place of zinc dialkyldithiophosphate at best only marginally satisfies the required levels of antiwear and oxidation inhibition. The use of magnesium sulfonate detergents which are also effective to enhance the antiwear properties in valve train systems has also been studied and, in fact, some commercially available engine oils use a magnesium sulfonate detergent. However, engine oils containing a magnesium sulfonate detergent have drawbacks in that crystalline precipitates are sometimes produced when these engine oils are stored under humid or variable temperature conditions for a long period of time. Such precipitates may cause plugging of the filter which is installed in the engine oil circulating system. Such plugging is more likely to occur when a large amount of the magnesium sulfonate detergent is used so as to enhance the desired antiwear properties. Thus, the use of magnesium sulfonate detergents is not a satisfactory solution.
At the present time, demand for further decrease of phosphorous content is very high from the viewpoint of the aforementioned problems. For instance, it is sometimes desired to decrease the phosphorous content to levels below the regulated upper limit and the 0.1 wt. % phosphorous level of today's better engine oil. This reduction cannot be satisfied by the present measures in practice and still meet the severe antiwear and corrosion inhibiting properties required of today's engine oils.
Thus, it would be desirable to develop lubricating oils, and additives and additive packages therefore, having low levels of phosphorous but which still provide the needed wear protection and corrosion protection now provided by lubricating oils having higher levels of zinc dialkyldithiophosphate, but which do not suffer from the disadvantages of the low phosphorous level lubricants discussed above.
U.S. Pat. No. 3,876,550 (issued 1975) discloses lubricating compositions containing an alkylene bis(dithiocarbamate), as an antioxidant, and a substituted succinic acid as a rust inhibitor. The alkylene dithiocarbamate is represented in the patent by the formula R
1
R
2
N—C(S)—S-alkylene-S—C(S)—NR
3
R
4
. Example 5 of the patent describes a crankcase lubricant containing a VI improver, an ashless dispersant and methylene bis(dibutyldithiocarbamate). The patent further teaches that the composition may also contain various other additives, for example, detergents, dispersants, VI improvers, extreme pressure agents, antiwear additives, etc., as well as other oxidation inhibitors and corrosion inhibitors (Col. 7, lines 35-55) and cites an extensive list of extreme pressure agents, corrosion inhibitors and antioxidants, including zinc salts of phosphorodithoic acid (Col. 8, lines 1-22).
The use of methylene bis(dibutyldithiocarbamate) as an oxidation inhibitor in lubricating oils, in combination with other ingredients, is also disclosed in U.S. Pat. Nos. 4,125,479 (1978) and 4,880,551 (1989).
U.S. Pat. No. 4,879,054 (1989) is directed to cold temperature greases and teaches using dithiocarbamates such as Vanlube 7723, i.e., 4,4′-methylene bis(dithiocarbamate), in such greases to provide extreme pressure antiwear properties (Col. 6, lines 18-28). Examples 13-18 (Col. 14, lines 26-32) describe using Vanlube 7723 and triarylphosphate as replacements for lead naphthenate and zinc dithiophosphate. The use of dithiocarbamates as extreme pressure antiwear additives is also taught by U.S. Pat. No. 4,859,352, and U.S. Pat. No. 4,648,985 teaches that the combination of dithiocarbamates with zinc dithiophosphate and copper salts of carboxylic acid provide lubricants with extreme pressure properties.
SUMMARY OF THE INVENTION
The present invention provides lubricating oil compositions which provide high antiwear protection and oxidation-corrosion protection, but which have only low levels of phosphorous, less
Magarifuchi Jiro
Mochizuki Akihiro
Nakazato Morikuni
Tanabe Hiroshi
Chevron Oronite Company LLC
Lee Steven G. K.
Medley Margaret
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