Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic -co- compound
Reexamination Certificate
1995-05-17
2003-12-16
Medley, Margaret (Department: 1714)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic -co- compound
C508S496000
Reexamination Certificate
active
06664216
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. The compositions of the invention require no miscibility-enhancing solvents and are readily biodegradable.
2. Description of the Related Art
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.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a biodegradable ester base stock and a two-cycle engine oil composition containing same which is adapted for use in both water-cooled and air-cooled two-cycle engines. The oil composition of the invention is formulated so as to eliminate the need for a conventional solvent, thereby substantially reducing not only the pollution potential of two-cycle engines lubricated therewith, but the hazard risk inherent in solvent-containing formulations.
According to one embodiment of the present invention, there is provided an ester base stock for a two-cycle engine oil composition, which consists essentially of a blend of (a) a first polyol ester comprising, as its reactive components, a neopentylpolyol and a C
16
-C
20
branched chain, saturated monocarboxylic acid, and (b) a second polyol ester comprising, as its reactive components, a neopentyl polyol and a carboxylic acid selected from the group consisting of at least one C
5
-C
10
linear, saturated monocarboxylic acid, or at least one C
16
-C
20
linear or branched chain, unsaturated monocarboxylic acid.
According to another embodiment of this invention, there is provided an ester base stock for a two-cycle engine oil composition, which consists essentially of a blend of (a) a first polyol ester comprising, as its reactive components, a neopentyl polyol and a C
8
-C
10
linear, saturated monocarboxylic acid and (b) a second complex polyol ester comprising, as its reactive components, a neopentyl polyol, a C
6
-C
12
dicarboxylic acid and a C
5
-C
10
linear or branched chain, saturated monocarboxylic acid.
A solvent substitute, if desired, may optionally be incorporated in the ester base stocks of the invention. Suitable for this purpose are any of various relatively low molecular weight esters comprising as the reactive components thereof, a C
8
-C
13
linear or branched chain monohydric alcohol and a C
5
-C
12
linear or branched chain carboxylic acid.
The ester base stocks of the invention are characterized by their superior biodegradability, flash point and viscosity properties, as compared with two-cycle engine lubricant base stocks heretofore available. The biodegradability of the ester base stocks of the invention is greater than 80%, as determined by CEC-L-33-T-82. Each of the ester base stocks of the invention has a flash point of at least 175° C. The kinematic viscosity of the ester base stocks of the invention is less than 15 cSt at 100° C.
The two-cycle engine oil compositions of the invention are composed of the above-described base stocks and any of the performance additive packages known in the art, preferably ashless detergent/dispersant additives, e.g., reaction products of polyamines and relatively long chain fatty acids. In addition to having the desirable biodegradability, flash point and viscosity properties noted above, the two-cycle engine oil compositions of the invention have excellent miscibility with gasoline, in fuel/oil ratios between 16:1 to 100:1
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A. Ester Base Stocks
Preferred two-cycle engine oil base stocks of the invention are blends consisting essentially of a first polyol ester formed by the reaction of a neopentyl polyol and a C
16
-C
20
branched chain, saturated monocarboxylic acid and a second polyol ester formed by the reaction of a neopentyl polyol and a carboxylic acid selected from the group consisting of (i) at least one C
5
-C
10
straight chain, saturated monocarboxylic acid or (ii) at least one C
16
-C
20
straight or branched chain, unsaturated monocarboxylic acid.
Suitable neopentyl polyols for preparation of the ester blends described above include trimethylolethane, trimethylolpropane, ditrimethylolpropane, pentaerythritol, dipentaerythritol, neopentylglycol and mixtures of any two or more of such neopentyl polyols. Trimethylolpropane is particularly preferred as the neopentyl polyol reactant in both components of the preferred ester blend described immediately above.
The preferred acids which may be used to form the first polyol ester include the C
16
-C
18
“isoacids”, isostearic acid being particularly preferred. Isostearic acid is a readily available commercial product obtained as a by-product from the manufacture of polymer fatty acids by the polymerization of naturally-occurring, unsaturated C
18
fatty acids. It is obtainabl
Beimesch Bruce J.
Lakes Stephen C.
Stoeppel, II Henry G.
Cognis Corporation
Drach John E.
Medley Margaret
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