Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic -co- compound
Reexamination Certificate
1996-06-05
2003-12-02
Medley, Margaret (Department: 1714)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic -co- compound
Reexamination Certificate
active
06656888
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to two-cycle engine oil compositions and to ester base stocks which are components thereof. These two-cycle engine oil compositions require no miscibility-enhancing solvents and are readily biodegradable.
The present invention further relates to grease formulations and to ester base stocks which are components thereof. These grease formulations are largely biodegradable.
2. Description of the Related Art
Great efforts have been made in recent years to develop and employ more and more products and technologies that are compatible with the environment. This trend began with a search for biodegradable oils for outboard engines and biodegradable oils for chain saws. Likewise, there has been a search for a new generation of lubricating greases in agriculture, the central lubrication of truck chassis, in wastewater purification plants, in hydro-electric power plants and for the lubrication of rails, wheel flanges and switches on the railways.
The two-cycle (two stroke) engine has gained considerable popularity as a power source for such devices as outboard motors, snow mobiles, mopeds and a variety of landscaping equipment, e.g., lawnmowers, chain saws, string trimmers and blowers. The widespread use of two-cycle engines is due primarily to their simple design and lightweight construction, their ability to provide high power output with quick starts at low temperature and their relatively low cost.
Two-cycle engines are operated using a mixture of gasoline and a lubricant in prescribed proportions. The lubricant must provide satisfactory performance characteristics under severe operating conditions. Lubricants for two-cycle engines are generally composed of a mineral oil or synthetic base fluid, performance additive(s) and a solvent, ordinarily a relatively low boiling petroleum distillate, to enhance gasoline/lubricant miscibility.
The technologies developed to date for reducing exhaust emissions from four-cycle car and truck engines have not been successfully adapted to two-cycle engines. Hence, there is growing public concern over the high levels of hydrocarbon emissions from these small engines, as hydrocarbons do not readily biodegrade.
The hydrocarbon emissions are a consequence of the basic design of the engine. Specifically, in the power stroke of a typical two-cycle engine, air, oil and fuel are drawn into the crank case as the combined charge is compressed in the space above the piston. In the exhaust stroke, the burnt gases are discharged through exhaust ports, and a fresh combustible charge is transferred from the crank case to the space above the piston. Because the exhaust ports open before and close after transfer of the fresh combustible charge occurs, as much as 20% of the fresh charge will be discharged unburnt with the exhaust. Consequently, hydrocarbon emissions far exceed the level of emissions from a comparable four-cycle engine.
Water-cooled outboard motors exhaust directly into the water, giving rise to water pollution, whereas the other devices mentioned above, which are equipped with air-cooled two-cycle engines, produce emissions that pose a serious air pollution problem. For example, the California Air Research Board has determined that many two-cycle engines produce up to fifty times the pollution of truck engines per horsepower hour.
The above-noted pollution problems are exacerbated by the presence of volatile organic solvents in the lubricant. Moreover, some of the solvents used as miscibility enhancers, such as Stoddard solvent, have relatively low flash points, thus creating a potential fire risk, which is of particular concern in connection with the storage and transportation of such products.
Thus, a need exists for a two-cycle engine oil composition which is formulated so as to prevent pollution by protecting against emission of harmful hydrocarbons into the environment, and to reduce the hazard potential of the solvent-containing lubricants, especially in storage and in transit. These objectives must be obtained, however, while simultaneously satisfying stringent performance standards, e.g., good lubricity and detergency, particularly on piston rings, superior anti-seizure properties and high gel/floc resistance, and providing optimum miscibility of lubricant and fuel over the applicable range of operating conditions.
A grease may be made from oil that is thickened with a gelling agent, as for example, a soap. The common gelling agents (thickeners) used to make greases are the fatty-acid soaps of lithium, calcium, sodium, aluminum and barium, in concentrations of 3-25 wt %.
Chemical additives similar to those used in lubricating oils also may be added to grease to improve the properties of the grease as, for example, oxidation resistance, rust protection, and extreme-pressure (EP) properties.
Up until recently, very few synthetic oils have been used extensively in the formulation of lubricating greases. This reflects the ability of greases based on the natural oils derived from petroleum and its products to satisfy the market. Up until now, it has not been generally recognized that suitable greases can be made using certain biodegradable synthetic materials.
CEC-L-33-T-82 identifies a test method developed by the Coordinating European Council (CEC) and is reported by the CEC in “Biodegradability of Two-Stroke Cycle Outboard Engine Oils in Water: Tentative Test Method,” pp. 1-8, which is incorporated herein by reference. Using this test method, mineral oils are 15%-30% biodegradable, and natural vegetable oils are 70% to 95% biodegradable. Esters are up to 95% biodegradable, depending on chemical structure. Generally, a material that is classified by the CEC test as >70% is “rapidly biodegradable”; see the paper of Dr. Dirk Loderer of Kluber Lubrication, Munich, Germany, presented at the National Lubricating Grease Institute in October, 1994. That terminology is adopted in describing the present invention. In addition, the term “readily biodegradable” is used to refer to a material that is ≧80% biodegradable.
The descriptions of grease formulations in the patent literature are generally silent with respect to biodegradability. The grease formulations made according to the examples that follow have been shown to be rapidly biodegradable. Typical of some of the prior art lubricating greases in the literature are those described in U.S. Pat. Nos. 3,622,512 and 4,879,054, described below, both of which patents are incorporated herein by reference.
SUMMARY OF THE INVENTION
The present invention provides a novel grease formulation that is based on the use of a base stock which is an ester of a C
12
-C
20
monocarboxylic acid. The greases that comprise these specially selected polyol esters are not only reliable but are also rapidly biodegradable.
The base stock in the inventive grease formulations preferably comprise polyol ester which has as its reactive components neopentyl polyol and a C
12
-C
20
monocarboxylic acid. Particularly suitable acids to use are C
12
-C
20
branched chain saturated monocarboxylic acids.
The improved rapidly biodegradable grease is provided which performs well at normal temperatures and ambient conditions as well as at more extreme temperatures.
In one embodiment, a grease composition of the invention comprises (a) ester base stock and (b) thickener, wherein the ester base stock comprises a polyol ester of C
12
-C
20
monocarboxylic acid or wherein the ester base stock comprises a blend of two polyol esters where the first of the two polyol esters forms the major component of the blend and is a polyol ester of C
12
-C
20
monocarboxylic acid and the second of the two polyol esters is a minor component of the blend and is a polyol ester of simple C
5
-C
10
carboxylic acid (i.e., C
5
-C
10
monocarboxylic acid), C
5
-C
10
polycarboxylic acids (i.e., C
5
-C
10
dicarboxylic acids) or mixtures thereof.
In another embodiment, the rapidly biodegradable grease composition of the invention comprises (a) ester base stock and (b) thickener,
Cognis Corporation
Drach John E.
Medley Margaret
LandOfFree
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