Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic compound containing boron
Reexamination Certificate
2001-12-06
2004-06-01
McAvoy, Ellen M (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic compound containing boron
C508S185000, C508S232000, C508S293000, C508S364000, C508S454000, C508S518000
Reexamination Certificate
active
06743757
ABSTRACT:
The present invention relates to dispersants for lubricating oil compositions and lubricating oil compositions that contain such dispersants. More particularly, the present invention relates to dispersants that provide excellent control of sludge/varnish formation and soot induced viscosity increase in lubricating oil compositions upon use, and which further provide improved piston cleanliness and ring-sticking performance.
BACKGROUND OF THE INVENTION
Additives have been commonly used to try to improve the performance of lubricating oils for gasoline and diesel engines. Additives, or additive packages, may be used for a number of purposes, such as to improve detergency, reduce engine wear, stabilize a lubricating oil against heat and oxidation, reduce oil consumption, inhibit corrosion and reduce friction loss. “Dispersants” are used to maintain in suspension, within the oil, insoluble materials formed by oxidation and other mechanisms during the use of the oil, and prevent sludge flocculation and the precipitation of insoluble materials. Another function of the dispersant is to prevent the agglomeration of soot particles, thus reducing increases in the viscosity of the lubricating oil upon use. Crankcase lubricants providing improved performance, including acceptable soot dispersing characteristics, have been continuously demanded.
In addition, users of crankcase lubricants, particularly original equipment manufacturers (OEM's) have required lubricants to meet ever more stringent performance criteria. One such performance criterion involves piston cleanliness. A severe test of piston cleanliness is the VW TDi test (VW-PV1452; CEC L-78-T-99). Another performance criterion measured by this test is “ring-sticking”, which refers to the sticking of piston rings during the operation of compression-ignited (diesel) internal combustion engines.
Most dispersants in use today are reaction products of (1) a polyalkenyl-substituted mono- or dicarboxylic acid, anhydride or ester (e.g., polyisobutenyl succinic anhydride), also commonly referred to as a carboxylic acid acylating agent; and (2) a nucleophilic reactant (e.g., an amine, alcohol, amino alcohol or polyol). The ratio of mono- or dicarboxylic acid producing moieties per polyalkenyl moieties can be referred to as the “functionality” of the acylating agent. In order to improve dispersant performance, the trend has been to increase the functionality of the dispersant backbone, and ultimately, increase the average number of nucleophilic moieties per dispersant molecule.
U.S. Pat. No. 4,234,435 describes acylating agents that are hydrocarbyl-substituted dicarboxylic acids derived from polyalkenes having a number average molecular weight of 1300 to 5000, and at least 1.3 (e.g., 1.3 to 4.5) dicarboxylic acid groups per polyalkene, wherein the molecular weight distribution (M
w
/M
n
) of the polyalkene moiety is in a range of from 1.5 to about 4.
It is also known that dispersants that are the reaction product of a carboxylic acid acylating agent and an amine, alcohol, amino alcohol or polyol can be further reacted with a boron compound in order to provide the dispersant with improved wear, corrosion and seal compatibility characteristics. Boration of nitrogen-containing dispersants is generally taught in U.S. Pat. Nos. 3,087,936 and 3,254,025. U.S. Pat. No. 4,234,435, discussed supra, discloses optional post-treatment, including the optional boration, of high functionality dispersants. U.S. Pat. No. 6,127,321 discloses a formulation containing a dispersant having a moderate succination ratio, which dispersant may be borated.
Lubricating compositions formulated to include a dispersant or dispersants with an average functionality of about 1.0 to 1.2 have been found to provide adequate piston cleanliness performance, but an insufficient level of dispersancy. The use of a dispersant or dispersants with higher functionality improves the level of dispersancy, but adversely impacts piston cleanliness performance. Thus, it would be advantageous to provide a dispersant, or dispersant mixture, that provides improved dispersing characteristics while simultaneously exhibiting excellent piston cleanliness. The present inventors have now found that by controlling simultaneously the functionality of the dispersant, and the molecular weight distribution of the polyalkenyl moiety of the dispersant, the ring-sticking and piston cleanliness performance of a lubricating oil (as measured by the VWTDi test) can be improved while maintaining excellent soot and sludge dispersing characteristics.
SUMMARY OF THE INVENTION
In accordance with a first aspect of the invention, there is provided an optimized dispersant composition that comprises one or more dispersants that are polyalkenyl-substituted mono- or dicarboxylic acid, anhydride or ester derivatized by reaction with a nucleophilic reactant, wherein at least one dispersant has a polyalkenyl moiety with a molecular weight distribution of from about 1.5 to about 2.0, and from greater than about 1.3 to less than about 1.7 mono- or dicarboxylic acid producing moieties per polyalkenyl moiety.
In a second aspect of the invention, there is provided a lubricating oil composition comprising a major amount of an oil of lubricating viscosity and a minor amount of a dispersant composition that comprises one or more dispersants that are polyalkenyl-substituted mono- or dicarboxylic acid, anhydride or ester derivatized by reaction with a nucleophilic reactant, wherein at least one dispersant has a polyalkenyl moiety with a molecular weight distribution of from about 1.5 to about 2.0, and from greater than about 1.3 to less than about 1.7 mono- or dicarboxylic acid producing moieties per polyalkenyl moiety.
In a third aspect of the invention, there is provided an additive concentrate comprising from about 20 to 90 wt. % of a normally liquid, substantially inert, organic solvent or diluent, and from about 10 to about 90 wt. % of a dispersant composition that comprises one or more dispersants that are polyalkenyl-substituted mono- or dicarboxylic acid, anhydride or ester derivatized by reaction with a nucleophilic reactant, wherein at least one dispersant has a polyalkenyl moiety with a molecular weight distribution of from about 1.5 to about 2.0, and from greater than about 1.3 to less than about 1.7 mono- or dicarboxylic acid producing moieties per polyalkenyl moiety.
The present invention also includes a method for improving the piston cleanliness and reducing the ring-sticking tendencies of a diesel internal combustion engine, which method comprises lubricating such an engine with a lubricating oil composition comprising a major amount of an oil of lubricating viscosity and a minor amount of a dispersant composition that comprises one or more dispersants that are polyalkenyl-substituted mono- or dicarboxylic acid, anhydride or ester derivatized by reaction with a nucleophilic reactant, wherein at least one dispersant has a polyalkenyl moiety with a molecular weight distribution of from about 1.5 to about 2.0, and from greater than about 1.3 to less than about 1.7 mono- or dicarboxylic acid producing moieties per polyalkenyl moiety.
A further aspect of the invention is directed to a dispersant composition, lubricant, lubricant concentrate or method, as described above, wherein the dispersant composition further contains boron, and a ratio of the wt. % of boron in the finished lubricant composition to wt. % of dispersant nitrogen (B/N) is from about 0.05 to about 0.24.
Other and further objects, advantages and features of the present invention will be understood by reference to the following specification.
DETAILED DESCRIPTION OF THE INVENTION
Dispersants useful in the context of the present invention include the range of nitrogen-containing, ashless (metal-free) dispersants known to be effective to reduce formation of deposits upon use in gasoline and diesel engines, when added to lubricating oils. The ashless, dispersants of the present invention comprise an oil soluble polymeric long chain backbone having functional
Bell Ian A. W.
Emert Jacob
Fellows Raymond
Gutierrez Antonio
Robson Robert
Infineum International Ltd.
McAvoy Ellen M
LandOfFree
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