US 2932618 A
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United States Patent ENGINE DEPOSIT REMOVAL Paul E. Oberdorfer, Jr., Clayrnont, Del., assignor to Sun Oil Company, Philadelphia, Pa., a corporation of New Jersey No Drawing. Application November 15, 1956 Serial No. 622,256
4 Claims. (Cl. 252143) This invention relates to a process for removing deposits from the combustion chambers of internal combustion engines, and to compositions of matter suitable for use in such a process.
It is well known to the art that during the operation of an initially clean internal combustion engine, deposits form and accumulate on surfaces within and adjacent to the combustion zone, such as on the cylinder head, spark plugs, piston tops, and valves. These deposits have a number of adverse effects on engine operation, for example, they cause an increase in the octane requirement of the engine, and also contribute to preignition with con-,
sequent roughness of operation. The problem of engine deposits is particularly acute when tetraethyl lead is contained in the fuel, since the deposits in this case contain an appreciable amount of lead compounds which adhere firmly to the surfaces on which they are deposited, and which contribute to shorting of the spark plugs, with consequent loss of power.
It is an object of this invention to provide a series of solvent formulations which are highly efiective, when brought into contact with engine deposits containing lead, to soften and loosen the deposits to a degree such that, on starting the engine after such contacting, the deposits will break off the surfaces to which they are attached and will be blown out the exhaust, leaving the surfaces in the combustion zone essentially free of deposits.
In my application, United States Serial No. 595,055, filed July 2, 1956, of which the present application is a continuation-in-part, I disclosed that cyclic carbonate inner esters having the formula:
RgC-O 9 RgC-O were effective in removing engine deposits. In that application, I disclosed a preferred solvent formulation comprising propylene carbonate, ethyl acetate, and ethylene glycol monoethyl ether. This solvent is highly effective in removing gummy deposits from relatively cool surfaces, such as surfaces of a carburetor, and is also effective to a degree in removing deposits from surfaces in the combustion zone of an engine.
I have now found that if aqueous acetic acid is included as a component of the solvent formulation, superior results may be obtained in removing deposits from the combustion chambers of internal combustion engines which have been operated with a leaded gasoline. The reason why the acetic acid contributes to the effectiveness of the solvent formulation is not definitely known, but it may be that it converts the lead compounds in the deposits to soluble lead acetates, which dissolve during the power stroke of the piston, so that they no longer stick tenaciously to the surfaces to which they are attached, and may be easily removed in conjunction with the carbon deposits loosened by the carbonate inner ester component of the solvent.
The preferred compositions of the present invention comprise from about 10% to about 70% of a cyclic carbonate inner ester, from about 10% to about 30% of a low-boiling polar solvent such as acetone, dimethyl acetal, methylal, methanol, methyl ethyl ketone, ethanol, isopropanol, ethyl acetate, and the like, and from about 20% to about 60% aqueous acetic acid, which may range in strength from about 25% to about. Alternatively, a compound which yields acetic acid when exposed to the conditions obtained in the cylinders of an engine under operation, such as aceto-acetic ester, benzal diacetate, acetone diacetate, etc., may be used in place of the acetic acid. The cyclic carbonate inner ester has the formula:
in which R may be hydrogen or a hydrocarbon radical. Typical of such esters are ethylene carbonate:
HzC-O C=O H2C"0/ propylene carbonate:
H 05H1-C-0 C=O and its isomers HzC-O and higher homologues of the above compounds. While in the compounds specifically shown above the hydrocarbon substituents are alkyl, they may also be aryl, alkenyl, or alkaryl, for example, suitable compounds would include phenylethylene carbonate, methyl phenylethylene carbonate, or vinylethylene carbonate. I prefer to use carbonates which have a boiling point sufficiently high that they do not immediately vaporize upon introduction into the cylinders of an idling engine, since in order to make effective contact with the engine deposits, it is necessary that the carbonate be introduced into the cylinder as a mist which condenses on he surfaces to be treated as a liquid film, in order to effect proper penetration of the deposits. I prefer to use propylene carbonate or higher molecular weight carbonates. If, however, the carbonate is of very high molecular weight, since its solvent power depends on the cyclic ester group, it is obvious that much larger quantities must be used in order to introduce into the engine the same number of cyclic ester groups as when using lower molecular weight esters. For this reason, I prefer that there be not more than about six to nine carbon atoms in the substituent hydrocarbon groups, although for special applications, such as when lubricity in the cleaning composition isdesired, higher molecular weight esters may be used. The low-boling polar solvent component of my new compositions is used chiefly to control their viscosity, but it is thought that it FORMULA 1 Percent Propylene carbonate Acetone 25 50% acetic acid 50 FORMULA H Butylene carbonates -1 40 Methyl ethyl ketone 75% acetic acid 30 FORMULA III Amylene carbonate 50 Methanol 15 60% acetic acid FORMULA IV Propylene carbonate 25 Acetone 25 Acetoacetic ester 25 Water 25 In order to illustrate the effectiveness of my new compositions in cleaning deposits from the cylinders of internal combustion engines, the following examples are given:
Example I A freshly cleaned 1956 Oldsmobile engine was tested at 2000 rpm. and was found to have a power output of 102.1 HP. and an octane requirement of 87. The engirls was run for 120 hours on a leaded gasoline. On retesting it was found that the power output had dropped to 80.3, and the octane requirement had increased to 95. The spark plugs were then removed and replaced with new plugs, and the engine was retested. It was found that the power output increased to 100.1, but the octane requirement remained fairly constant at 93. This indicated that spark plug fouling had been the cause of the loss of power, but other deposits in the cylinders were responsible for the increase in octane requirement. The new plugs were then taken out and the old dirty ones replaced without cleaning.
'The engine was then restarted, brought to full operating temperature and throttled to a fast idling speed. The air cleaner was then removed, and about one and onequarter pints of Formulation I were dripped into the carburetor air intake at the maximum rate which would just prevent engine stalling. A final quarter pint was then added as a slug to stall the engine. Following a soaking period of about one hour, the engine was restarted and was run for about 20 minutes to blow out loosened deposits. It was then retested and found to have a power output of 97.8 HP. and an octane requirement of 88, which was virtually the same as that of the engine when freshly cleaned. The engine was then taken apart and visually inspected. The surfaces in the combustion zones were found to be essentially free of deposits.
Example II The same procedure as in Example I was followed in cleaning out a number of late model cars which had accumulated engine deposits in normal driving use. Significant reduction in octane requirement was obtained in all cases, as indicated in the following table.
Octane Number Requirement Car Before After Cleaning Cleaning 1956 Ford Fairlane 90 84. 5 1955 Buick Super 96.4 94 1956 Mercury 96. 4 93.5 1954 Oldsmobile 88 93.2 90. 6 1954 Oldsmobile 98 93.8 89.6
1. The method of removing deposits from an internal combustion engine which comprises contacting the deposits with a composition comprising from about 10 to about volume percent of. a cyclic carbonate inner ester selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate and amylene carbonate, from about 10 to about30 volume percent of an organic polar solvent selected from the group consisting of acetone, dimethyl acetal, methylal, methanol, methyl ethyl ketone, ethanol and isopropanol, and mixtures thereof, and from about 20 to about 60 volume percent of an aqueous solution of a compound selected from the group consisting of acetic acid and compounds capable of yielding acetic acid by thermal decomposition.
2. The method according to claim 1 in which the cor. position comprises about 25 volumes of'propylene carbonate, about 25 volumes of acetone, and about 50 volumes of fifty percent aqueous acetic acid solution.
3. A solvent formulation for the removal of engine deposits which comprises from about 10 to about 70 volume percent of a cyclic carbonate inner ester selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate and amylene carbonate, from about-10 to about 30 volume percent of an organic polar solvent selected from the group consisting of acetone, dimethyl acetal, methylal, methanol, methyl ethyl ketone, ethanol, and isopropanol, and mixtures thereof, and from about 20 to about 60 volume percent of an aqueous solution selected from the group consisting of acetic acid and compounds capable of yielding acetic acid by thermal decomposition.
4. A solvent formulation for the removal of engine deposits which comprises about 25 volumes of propylene carbonate, about 25 volumes of acetone, and about 50 volumes of 50% aqueous acetic acid solution.
References Cited in the file of this patent UNITED STATES. PATENTS OTHER REFERENCES Allpress et al.: J. Chem. Soc., vol. 125, pp. 2259-2264 (1924).
Condensed Chemical Dictionary, 5th Ed., pp. 454 and 909 (1956), pub. by Reinhold Pub. Corp., N.Y.