Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Compound of indeterminate structure – prepared by reacting a...
Reexamination Certificate
1994-03-31
2001-10-09
Medley, Margaret (Department: 1714)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Compound of indeterminate structure, prepared by reacting a...
C508S232000, C508S233000, C508S241000, C508S452000, C508S466000, C508S507000
Reexamination Certificate
active
06300288
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to grease compositions which contain a functionalized polymer which serves as a thickener or rheology modifier.
Greases typically comprise a base oil and a thickener, which is normally an acid-containing material. In some instances polymers also have been added to grease compositions in an attempt to improve performance characteristics such as dropping points, cone penetration, water wash-off, or oil separation.
U.S. Pat. No. 3,591,499, Morway, Jul. 6, 1971, discloses a grease containing a metal salt of an &agr;,&ohgr;-dicarboxylic acid of molecular weight 500-2500. The metal can be an alkali metal or alkaline earth metal. The salts of the branched carboxy-terminated dicarboxylic acids are more shear stable than is polyisobutylene, yet are still capable of imparting adhesiveness and stringiness to a grease. At the same time, these salts per se are capable of thickening oil to a grease structure.
U.S. Pat. No. 3,476,532, Hartman, Nov. 4, 1969, discloses metal-containing complexes of oxidized polyethylene, containing functional oxygen groups e.g. carbonyl, carboxyl, hydroxy, etc. The material is useful in production of grease-like compositions. The composition is a mixture of the oxidized poly-ethylene and a complexing agent selected from metal salts, metal salts of fatty acids, the metals being at least divalent, and metal complexes.
U.S. Pat. No. 4,877,557, Kaneshige et al., Oct. 31, 1989, discloses a lubricating oil composition comprising a synthetic hydrocarbon lubricating oil, a load withstanding additive, and a liquid modified ethylene/&agr;-olefin random copolymer. The load withstanding additive is roughly divided into an oiliness agent and an extreme pressure agent. The oiliness agent can be higher fatty acids such as oleic acid and stearic acid. Extreme pressure agents include, for example, organic metal type extreme pressure agents. The load-withstanding additives can be used singly or in the form of a mixture of two or more of them. The liquid copolymer is prepared from an unmodified polymer with a number average molecular weight of 300 to 12,000.
Australian application 500,927, published in 1978 or 1979, discloses a lubricating grease comprising a paraffinic mineral oil, a calcium complex soap thickener, and an organic terpolymer of 65% ethylene, 5% ester comonomer, and 0.01-3% acid comonomer, melt index 0.5 to 200.
U.S. Pat. No. 5,275,747, Gutierrez et al., Jan. 4, 1994, discloses a derivatized ethylene alpha olefin polymer useful as a multifunctional viscosity index improver additive for oleaginous compositions. The alpha-olefin polymer is terminally unsaturated and has a number average molecular weight of above 20,000 to about 500,000. It is substituted with mono-or dicarboxylic acid-producing moieties; it can be reacted with metals to form salts. The additive has multifunctional viscosity index improver properties and can be used by incorporation and dissolution into an oleaginous material such as lubricating oils. Other additives may also be present; crankcase compositions can contain 2 to 8000 parts per million of calcium or magnesium, generally present as basic or neutral detergents.
In the present invention an acid-functionalized polymer is incorporated into a grease composition to provide thickening and improve the performance of the composition.
SUMMARY OF THE INVENTION
The present invention provides a composition comprising an oil of lubricating viscosity; a polyolefin having grafted acid functionality, said polyolefin having a number average molecular weight of at least about 50,000; a metallic species capable of interacting with the acid functionality of said polyolefin to cause association among the acid groups; and a co-thickening agent; said polyolefin being present in an amount sufficient to increase the viscosity of the composition. The invention also provides a composition comprising a gelled overbased material dispersed in an oleophilic liquid medium; and a polymer containing acid functionality, present in an amount sufficient to increase the viscosity of the composition. The invention further provides a concentrate consisting essentially of a polyolefin having grafted carboxylic acid functionality, said polyolefin having a number average molecular weight of at least about 50,000; a co-thickening agent; and a concentrate-forming amount of an oleophilic medium. Further, the present invention provides a method for preparing a grease, comprising combining an oil of lubricating viscosity; a polyolefin having grafted acid functionality, said polyolefin having a number average molecular weight of at least about 50,000; a metallic species capable of interacting with the acid functionality of said polyolefin to cause association among the acid groups; and a co-thickening agent.
DETAILED DESCRIPTION OF THE INVENTION
Greases are typically prepared by thickening an oil basestock. The greases of this invention are oil-based, that is, they comprise an oil which has been thickened with a thickener, also referred to as a thickening agent. Greases are generally distinguished from oils in that they exhibit a yield point (at room temperature or at the temperature of use) while oils do not. That is, below a certain level of applied stress, greases will generally not flow; whereas oils will flow under an arbitrarily small stress, if very slowly. In practice this often means that greases cannot be poured and appear to be a solid or semisolid, while oils can be poured and have the characteristics of a fluid, even if a very viscous fluid. Compositionally, greases are often heterogeneous compositions, comprising a suspension of one material, often a fibrous crystalline material, in another. Oils, on the other hand, are normally more uniform, at least on a macroscopic scale, often comprising an apparently homogeneous solution of materials. Oils often exhibit Newtonian flow behavior; greases do not.
The oil of lubricating viscosity.
The grease compositions of this invention employ an oil of lubricating viscosity, including natural or synthetic lubricating oils and mixtures thereof. Natural oils include animal oils, vegetable oils, mineral oils, solvent or acid treated mineral oils, and oils derived from coal or shale. Synthetic lubricating oils include hydrocarbon oils, halo-substituted hydrocarbon oils, alkylene oxide polymers, esters of carboxylic acids and polyols, esters of polycarboxylic acids and alcohols, esters of phosphorus-containing acids, polymeric tetrahydrofurans, silicone-based oils and mixtures thereof.
Specific examples of oils of lubricating viscosity are described in U.S. Pat. No. 4,326,972 and European Patent Publication 107,282. A basic, brief description of lubricant base oils appears in an article by D. V. Brock, “Lubricant Base Oils,”
Lubricant Engineering
volume 43, pages 184-185, March 1987. A description of oils of lubricating viscosity occurs in U.S. Pat. No. 4,582,618 (Davis) (column 2, line 37 through column 3, line 63, inclusive). Another source of information regarding oils used to prepare lubricating greases is
NLGI Lubricating Grease Guide
, National Lubricating Grease Institute, Kansas City, Mo. (1987), pp. 1.06-1.09.
The co-thickening agent.
Grease thickeners are well known in the art of grease formulation, and they comprise one of the major components of the present invention. In the context of the present invention, however, the thickener or thickening agent can be referred to as a co-thickener or co-thickening agent. This is because the co-thickener, when present, does not provide the sole or necessarily even the primary source of the thickening of the grease. A significant amount, and sometimes the major amount, of the thickening is provided rather by a polyolefin having grafted acid functionality. This polymer, described in detail below, is believed to provide thickening in part through its interaction with metallic species which are also present in the composition and which are capable of interacting with the acid functionality of the polyolefin.
Conventional grease thic
Scharf Curtis R.
Todd Patricia R.
Twining Steven R.
Esposito Michael F.
Medley Margaret
Shold David M.
The Lubrizol Corporation
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