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  Viscosity modifiers for lubricant compositionsUSPTO Application #: 20070191242Title: Viscosity modifiers for lubricant compositions Abstract: A lubricant composition method of using the lubricant composition. The lubricant composition contains a base oil of lubricating viscosity and from about 5 to about 30 percent by weight of an additive comprising a shear stable olefin copolymer derived from a copolymer having a number average molecular weight ranging from about 50,000 to about 250,000. The shear stable olefin copolymer has a shear stability index of less than about 40, a polydispersity of not more than about 1.5, and a thickening efficiency of greater than about 1.8, and provides viscosity index improving properties to the lubricant composition. (end of abstract) Agent: New Market Services Corporation (formerly Ethyl Corporation) - Richmond, VA, US Inventors: Sanjay Srinivasan, Yoon Soo Song, Joseph Stephen Strukl, Peter Growcott, Paul G. Griffin, Akhilesh Duggal USPTO Applicaton #: 20070191242 - Class: 508591000 (USPTO) Related Patent Categories: Solid Anti-friction Devices, Materials Therefor, Lubricant Or Separant Compositions For Moving Solid Surfaces, And Miscellaneous Mineral Oil Compositions, Lubricants Or Separants For Moving Solid Surfaces And Miscellaneous Mineral Oil Compositions (e.g., Water Containing, Etc.), Solid Hydrocarbon Polymer The Patent Description & Claims data below is from USPTO Patent Application 20070191242. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD [0001] The following disclosure is directed to lubricants, lubricant compositions and additives, lubricated parts and engines, and methods for lubricating moving parts. BACKGROUND [0002] Lubricating oils used in gasoline and diesel crankcases include a natural and/or synthetic basestock and one or more additives to impart desired characteristics to the lubricant. Such additives typically include ashless dispersant, metal detergent, antioxidant and antiwear components, which may be combined in a package, sometimes referred to as a detergent inhibitor (or DI) package. [0003] Multigrade oils usually also contain one or more viscosity modifiers which are relatively long chain polymers. Such polymers may be functionalized to provide other properties when they are known as multifunctional viscosity modifiers, but primarily act to improve the viscosity characteristics of the oil over a desired operating temperature range. The viscosity modifier acts to increase viscosity at high temperature to provide more protection to the engine at high speeds, without unduly increasing viscosity at low temperatures which would otherwise make starting a cold engine difficult. High temperature performance is usually measured in terms of the kinematic viscosity (kV) at 100.degree. C. (ASTM D445), while low temperature performance is measured in terms of cold cranking simulator (CCS) viscosity (ASTM D5293, which is a revision of ASTM D2602)), mini-rotary viscometer (MRV; ASTM D4684), or scanning brookfield or gel index (ASTM D5133). [0004] Viscosity grades are defined by the SAE Classification system (SAE J300) according to the foregoing temperature measurements. Multigrade oils meet the requirements of both low temperature and high temperature performance and are thus referenced to both the relevant grades. [0005] Shear stability is a measure of the ability of an oil to resist permanent viscosity loss under high shear--the more shear stable an oil the smaller the viscosity loss when subjected to shear. Polymeric viscosity modifiers, which make a significant contribution to kV 100.degree. C., are not entirely shear stable. Such polymeric viscosity modifiers are characterized by a shear stability index (SSI). [0006] An oil or additive that exhibits relatively high shear stability will have an SSI that is relatively low. Typically, higher molecular weight polymers used in lubricating oil applications have poor shear stability (i.e., high SSI). However, viscosity modifiers with relatively low SSI require higher treat rates due to their relatively lower molecular weights and therefore lead to an increase in total formulation costs. Multigrade oils often have poor shear stability unless they use expensive viscosity modifiers having low SSI. Poor shear stability requires the oils to be blended to a higher initial kV 100.degree. C. which may result in poor fuel economy. Accordingly, there is a need for improved viscosity modifiers which are relatively shear stable and more cost effective to use in lubricant composition. SUMMARY OF THE EMBODIMENTS [0007] In one embodiment herein is presented a lubricated surface. The lubricated surface includes a thin film coating of a lubricant composition containing a base oil of lubricating viscosity and from about 5 to about 30 percent by weight of an additive comprising a shear stable olefin copolymer derived from a copolymer having a number average molecular weight ranging from about 50,000 to about 250,000. The shear stable olefin copolymer has a shear stability index of less than about 40, a polydispersity of not more than about 1.5, and a thickening efficiency of greater than about 1.8. [0008] In another embodiment, there is provided a vehicle having moving parts and containing a lubricant for lubricating the moving parts. The lubricant contains an oil of lubricating viscosity and from about 5 to about 30 percent by weight of an additive comprising a shear stable olefin copolymer derived from a copolymer having a number average molecular weight ranging from about 50,000 to about 250,000. The shear stable olefin copolymer has a shear stability index of less than about 40, a polydispersity of not more than about 1.5, and a thickening efficiency of greater than about 1.8. [0009] In yet another embodiment there is provided a method of lubricating moving parts. The method includes contacting the moving parts with a lubricant composition containing a lubricant additive. The lubricant additive includes a diluent or carrier oil and from about 5 to about 95 percent by weight of a shear stable olefin copolymer derived from a copolymer having a number average molecular weight ranging from about 50,000 to about 250,000. The shear stable olefin copolymer has a shear stability index of less than about 40, a polydispersity of not more than about 1.5, and a thickening efficiency of greater than about 1.8. The lubricant composition contains from about 5 to about 30 percent by weight of the additive based on a total weight of the lubricant composition. [0010] A further embodiment of the disclosure provides a method for improving the viscosity index of a lubricant composition. The method includes mixing with the lubricant composition from about 5 to about 30 percent by weight of an additive comprising a shear stable olefin copolymer derived from a copolymer having a number average molecular weight ranging from about 50,000 to about 250,000. The shear stable olefin copolymer has a shear stability index of less than about 40, a polydispersity of not more than about 1.5, and a thickening efficiency of greater than about 1.8. [0011] An advantage of the shear stable copolymer as described herein is that the polymer exhibits improved thickening efficient at a lower polymer loading. Another advantage of the shear stable copolymer is that it may be made using an amorphous lower ethylene containing copolymer, e.g., a copolymer having an ethylene content in the range of from about 40% to about 55% by weight. In addition to the shear stable olefin copolymers, the disclosure may also be applicable to shear stable star polymers based on styrene-isoprene chemistry. BRIEF DESCRIPTION OF THE DRAWINGS [0012] Further features and advantages of the embodiments will become apparent by reference to the detailed description of preferred embodiments when considered in conjunction with the following drawings, in which like reference numbers denote like elements throughout the several views, and wherein: [0013] FIG. 1 is a shear stability index profile of a mechanically sheared olefin copolymer according to the disclosure; [0014] FIG. 2 is a polydispersity profile for a mechanically sheared olefin copolymer according to the disclosure; [0015] FIG. 3 is a graphical representation of a viscosity profile for a mechanically sheared olefin copolymer according to the disclosure; [0016] FIG. 4 is a graphical representation of an olefin copolymer according to the disclosure in a process oil illustrating a change in viscosity during mechanical shearing compared to conventional olefin copolymers prepared under a high temperature extruder shearing and direct finishing process; and [0017] FIG. 5 is a thickening efficiency profile for a mechanically sheared olefin copolymer according to the disclosure compared to a thickening efficiency of conventional olefin copolymers prepared under a high temperature extruder shearing and direct finishing process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0018] As used herein, the term "hydrocarbyl substituent" or "hydrocarbyl group" is used in its ordinary sense, which is well-known to those skilled in the art. Specifically, it refers to a group having a carbon atom directly attached to the remainder of the molecule and having a predominantly hydrocarbon character. Examples of hydrocarbyl groups include: [0019] (1) hydrocarbon substituents, that is, aliphatic (e.g., alkyl or alkenyl), alicyclic (e.g., cycloalkyl, cycloalkenyl) substituents, and aromatic-, aliphatic-, and alicyclic-substituted aromatic substituents, as well as cyclic substituents wherein the ring is completed through another portion of the molecule (e.g., two substituents together form an alicyclic radical); Continue reading... 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