US2253585A - Lubricating oil composition - Google Patents

Description

Patented Aug. 26, 1941 LUBRICATING on. COMPOSITION John E. Schott, New York, N. Y., and Leonard B. Churchill, Cranford, N. 1., assignors to Tide Water Associated Oil Company, New York, N. Y., a corporation of Delaware No Drawing. Application April 12, 1938,

Serial No. 201,510

4 Claims. (01. 252-57) This inventionrelates to the lubrication of internal combustion engines; and is particularly directed, although not restricted, to satisfactory and improved lubrication in the Diesel type of engine wherein extreme service conditions of temperature and pressure are encountered. To the attainment of these and other ends, the invention provides and encompasses compounded liquid petroleum compositions consisting essentially of motor lubricating oil with an aluminum soap of a saturated fatty acid and. an alkylolamine as compounding ingredients. The compounded products retain substantially the viscosity and flow characteristics of an oil, and thereby distinguish from other compounded lubricants of the plastic flow type such as greases and so-called liquid greases.

This application is a continuation-impart of our copending application Serial No. 200,072, filed April 5, 1938. 5

Modern engine design has made lubrication of internal combustion engines an increasingly difficult and specific problem. In high speed units and especially in Diesel engines lubrication is required under service conditions of such severity as to approach the limit of safe and efllcient operation with straight mineral oils. High temperatures and pressures, tithe catalytic effect of hot metallic surfaces continuously contacted under these conditions, accumulating concentration of oxidizing agents, and autocatalytic effect developing as deterioration progresses all contribute to lubricant degradation. The lubricating capacity of the oil is rapidly diminished by chemical and thermal deterioration, and the products of deterioration create serious operating problems. Gummy or lacquer-like products, sludges, as-

phaltenes and coke are formed and the accumulation of such material has a naturally harmful effect upon engine parts and operation. Ring sticking, ineffective cylinder lubrication, increased wear, scoring of cylinder walls and like trouble results, and frequent shutdown for cleaning, overhauling and often replacing of engine parts may be necessary.

According to the present invention, the foregoing difllculties are obviated by lubricating internal combustion engines with a compounded lubricant comprising hydrocarbon lubricating oil, an aluminum soap of a saturated fatty acid and an alkylolamine.

There is evidence that an alkylolamine reacts with or modifies an aluminum soap of a saturated fatty acid; and we believe that our compounded lubricating composition containsa modifled aluminum soap of a saturated fatty acid or an aluminum soap-alkylolamine complex along with which may be some proportion of the respective compounding ingredients as added. It is to be understood, therefore, that such expressions as "lubricating composition comprising hydrocarbon lubricating oil, an aluminum soap of a saturated fatty acid and an alkylolamine, hydrocarbon lubricating oil compounded with an aluminum soap of a saturated fatty acid and an alkylolamine, or the like are intended to designate and embrace any liquid hydrocarbon lubricating oil composition in which an aluminum soap of a saturated fatty acid and an alkylolamine have been incorporated regardless of what complex compound or mixture may actually exist in the compounded product.

The exact chemical mechanism, of mineral oil J deterioration in internal combustion engine service is not clear although authorities have reasonably concluded that such phenomena as polymerization, oxidation and thermal decomposition are predominant factors. It-is not intended, however, to limit or attempt an explanation of results attending lubrication of internal combustion engines with the compounded oil of the invention on the basis of these or other theories. Results marking a distinction between success and failure in engine performance and lubrication are sufficient evidence that the compounding of an aluminum soap of a saturatedv fattyacid and an alkylolamine with hydrocarbon lubricating oil performs a novel and highlyuseful function.

Engine .tests are to be preferred forthe comparative evaluation of motor oils, especially when intended for service in the lubrication of Diesel engines, although the well known Indiana oxidation test or a modification thereof in which the test is carried out in the presence of a weighed quantity of steel wool may serve to provide an index. Sludge values do not seem to have particular signiiicancebut the character of the oxidation products at the end of a 70 hour run at 341 F. is an indication of conditions that may be expected in engine service. Good Diesel engine lubrlcantsgenerally give a clean tube without resinous or gummy products adhering to the walls. If the sludge is sticky, gummy and unfilterable, the probability is that the oil will cause ring sticking'in engine service. In the modified Indiana test there is usually a slight decrease in 1 weight of'the steel wool with promising oils and the steel wool when washed clean with hot kerosene'followed by naphtha has a bright ap- A pearance. In thecase of unsuitable oils the steel wool shows a definite increase in weight after the '70 hour test run.

. For demonstrating the operative significance of compounded lubricantsaccording to the present invention,actua1 lubrication of engines both of the spark ignition and of the compression ignition type was relied upon as the significant criterion. Collateral indications were obtained with the Indiana oxidation test and with the modified form of this in which the test is carried out in the presence of a weighed quantity of steel wool. In all test operations, comparison waswith blank runs in which straight mineral oil as used in the compounding of a given lubricant according to the invention supplied the lubrication.

The compounding of an aluminum soap of a saturated fatty acid and an alkylolamine with a hydrocarbon motor oil intended for service in the lubrication of internal combustion engines gave consistently improved results in all tests.

-In both automotive and Diesel engine service at the termination of thetests. In comparative test runs, straight mineral oils were markedly inferior, especially in Diesel engine service where relatively short runs resulted in badly stuck rings, inadequate lubrication and poor general engine condition at shutdown.

The invention has general utility in the art of motor oil preparation and use. The base stock which is compounded as.disclosed herein may comprise any hydrocarbon lubricating oil and is not restricted to particular crude petroleum sources or to particular degrees of refining. For example, an aluminum soap of a saturated fatty acid and analkylolamine have been compounded with motor oil from Pennsylvania crude and with motor oil from an asphaltic-naphthenic California crude. In each case like benefit in the way of improved lubrication and elimination of ring sticking or like engine trouble ensued. This is a particularly advantageous feature of the invention. Many compounds proposed for addition to petroleum oils are, as is well known, effectiveor compatible only with certain specific oils of prescribed crude origin.

In general it is preferred that the base stock used in preparing lubricating compositions as herein be a motor oil which has had a good or superior degree of refining in the course of production. In the case of naphthenic or asphaltic base 'stocks a refining treatment with sulfuric acid or a combination of solvent extraction and acid treatment is recommended. With Pennsylvania and like parailinic base stocks less rigorous refining treatment is necessary. One reason for the stated preference is the conventional desirability of goodor quality lubricating oil simply from the viewpoint of superior capacity as a lubricant. In a more pertinent aspect, however, we believe that our compounded lubricating composition has greater general utility in internal combustion engine service and gives better overall performance when well refined base stock is used.

In one embodiment, the lubricating compositions of the invention may be prepared by introducing suitable proportions of an aluminum soap of a saturated fatty acid (for example, 1% by weight based on the oil) into a selected motor oil at ordinary temperature, agitating thoroughly for sufllcient time to obtain a well disseminated mixture of soap in oil, adding suitable proportions of analkylolamine' (for example, 0.1% by weight based on the oil) to the still agitated mixture, applying heat suflicient to raise the temperature to about 270 F.-300 F., and maintaining the mixture at such temperature for approximately one-half hour, agitation being continued throughout the treatment. Aluminum soaps of saturated fatty acids are but sparingly soluble in mineral oil of lubricating oil viscosity, and when added at room temperatures tend to agglomerate-hence the desirability of thoroughly stirring the soap-oil mixture prior to the allwlolamine addition. If the soap-oil mixture is heated prior to an alkylolamine addition, viscosity builds up and at about 190 F.-220 F. there is a marked gelling effect which offers considerable resistance to agitation at this temperature stage. Asheating is continued, the gel thins out some what and the mixture may be stirred without excessive power consumption. If desired, this procedure may of course be used and an alkylolamine added after the mixture has been raised to elevated temperature.

It is far more desirable, however, to introduce an alkylolamine to an agitated soap-oil mixture before applying heat to the latter since in this procedure no abnormal viscosity increase or gel formation occurs during the heat treatment and a fully fluid mixture is maintained throughout. Apparently some reaction between the compounding agents or ingredients is initiated immediately upon admixture, and this progresses as heat is .applied.

As indicated above, themixture of oil and both compounding ingredients is heated at elevated temperature preferably 270 F.-300 F. for about one-half hour which is usually suflicient to complete reaction of the allwlolamine. If the heat treatment has been insufilcient for necessary completeness of reaction, the oil upon cooling to room temperature will be turbid and some further heating is required. Ordinarily, however, the indicated temperature and time of heating suffices to prepare a clear oil solution comprising the improved motor oil of the invention. Additional heating not unduly prolonged does no harm.

With most oils an upper temperature limit of about 340 F. might be used if care is exercised but this isnot regarded as particularly desirable since the objectives of the invention are satisfactorily attained with greater certainty and economy when the temperature does not exceed 300 F. Temperatures somewhat below 270 F. may be used successfully but with lower temperatures a longer period of heat treatment naturally is required. I

Aluminum soap of high purity is desired in the practice of the invention. Some such soaps, for example the commercial aluminum stearates,

contain small amounts on the order of 0.5% to of inorganic salts such as sodium sulfate. This is not especially objectionable, although with some oils th'e'higher proportions of inorganic impurity may occasion a small degree of diiiicultly removable sedimentation upon storageof the compounded lubricating composition. This does not. however, seem to have any par-. ticularly deleterious effect in engine service although the oil naturally is inferior in appearance to compounded oils which are clear solutions as are usually obtained in the preparation of lubricating compositions according to the invention.

As indicated hereinbefore, the acid radical of the soap herein is of the saturated type and the higher fatty acids are preferred. Commonly available or naturally occurring fatty acids have carbon atoms within the range of 12 to 22 in number, and aluminum soap for the purposes of the invention advantageously may be derived from saturated acids in this group. 'Aluminum stearates and aluminum palmitates may be mentioned by way of specific example. aluminum soaps of saturated fatty acids may be used.

The mono-, di-, and tri-soaps of aluminum are available or may be readily prepared by methods well known in the art. In each instance it is probable that the product contains some impurity percentage of one or both of the other forms with possibly some free acid as well. exploratory practice of the invention we have used the di-soap, for example aluminum distearate, and this is the present preferred embodiment, but the mono-soaps and tri-soaps likewise have utility in the preparation of compounded lubricating oils as herein. The ash content, of course, differs with the three forms and when motor oil specifications include a maximum allowable ash, this must be given consideration in selecting the proportion of a particular aluminum soap to be used in the preparation of the compounded oil. For, example, the mono-' In most of our olamine to be used as compounding ingredients Mixtures of generally, the viscosity of the compounded product may be regarded as a limiting factor. Beyond about 2% or 3% of aluminum soap, the viscosity is increased by the soap to some degree independently of the alkylolamine. 1

Relative to each other, the proportion of alkylolamine must be sufficient to avoid more than moderate increase in viscosity due to theaddition of aluminum soap but must be below a pro-,

portion effective to impart turbidity to the commodifying agents according to the invention may I practice of the invention. As other illustrative hydroxy amines may be mentioned di-ethyl ethanolamine, phenyl ethanolamine, phenyl diethanolamine, tri-propanolamine, tri-isopropanolamine, ethyl phenyl ethanolamine, and ethyl di-ethanolamine. Mixtures of these or other allgylolamines or substituted aliwlolamines may be used to modify aluminum soaps in the compounding of lubricating oil compositions according to the present invention.

The lubricating compositions of the invention havea higher viscosity and viscosity index than the motor oil used as a base stock. If the increase in viscosity is reasonably limited, this is a distinct advantage, but the necessity of avoiding too great a deviation from given specifications for different grades of motor oil makes it undesirable to have excessive viscosity increase in the compounded product. We have found that advantages in the way of improved lubrication and engine operation are readily and consistently obtained with lubricating compositions of the invention when the viscosity of the compounded product is increased only to a reasonable and desirable degree.

' optimum relative proportions of compounding in- Proportions oi' aluminum soap and of alkylpounded oil.

By way of example, we have foundas a general proposition that with good quality commercial aluminum di-stearate efi'ective and suitable proportions of triethanolamine fall in the range of about 5% to about 20%, and preferably about 8%- to about 15%, of the soap. In many experiments .using a well refined Pennsylvania base motor oil .ent motor oils comprise the base stock; and likewise will vary to some extent depending upon the amount of soap. With larger proportionsof soap the triethanolamine proportion generally should be larger. We believe that motor oils compounded with about 1.0%-1.5% by weight of aluminum stearate and proportions by weight of triethanolamine equal to about 840% of the soap will provide lubricating compositions according to the invention which are entirely satisfactory for the majority of contemplated services.

With soaps other than aluminum di-stearate or with alkylolamines other than triethanolamine,

gredients will vary somewhat but the general relation of the two components will be substantially in line with the data of the foregoing example. In any given instance, however, the desired proportions of materials may be readily determined by simple experiment, and specific illustrative disclosures herein are not intended in a limitative sense.

We claim:

1. Substantially liquid and non-stringy lubricating oil for internal combustion engines operat; ing at high sustained speeds and under extremeservice conditions of temperature and pressure such as may be encountered in Diesel engine lubrlcation, which comprises a hydrocarbon motor oil of suitable viscosity for the intended service which has been compounded and heated with ap-'- proximately 1% by weight of aluminum stearate and a quantity of an alkylolamine, in the range of about 5% to about 20% by weight of said aluminum stearate, suificient to improve the lubricating emciency of the 011, said compounded oil having substantially the viscosity and fluidity characteristics of the uncompounded oil.

2. Substantially liquid and non-stringy lubricating oil for internal combustion engines operating at high sustained speeds and under extreme service conditions of temperature and pressure such as may be encountered in Diesel engine lubrication, which comprises a hydrocarbon lubricating oil of suitable nominal viscosity for an intended service compounded and heated with small amounts of aluminum stearate and an allwlolamine in proportions such that the normal viscosity of the oil is not increased beyond a reasonable and desirable degree for its intended service, the aluminum stearate being introduced in an amount not less than one per cent.

3. Method of preparing motor oil composition suitable for the lubricating of internal combus tion engines, which comprises compounding hydrocarbon lubricating oil of suitable viscosity for the intended service with approximately 1% by weight of the aluminum stearate and a quantity of an alkylolamine, in the range of about 5% to about 20% by weight of said aluminum stearate, sufllcient to improve the lubricating efliciency of the oil, and then subjecting the resulting mixture to a period 01 heat treatment at a temperature'not substantially lower than 270 F.

4. Substantially liquid and non-stringy lubricating oil for internal combustion engines operating at high sustained speeds and under extreme service conditions of temperature and pressure such as may be encountered in Diesel engine lubrication, which comprises a hydrocarbon lubricating oil of suitable nominal viscosity 20 one per cent.

JOHN E. BCHOTT. LEONARD R. CHURCHILL.