US2342432A - Mineral oil lubricating composition and an improvement agent therefor and its methodof preparation - Google Patents

Description

MINERAL om Larca'rmc coMrosrrroN VENT AGENT THERE- ITS METEQD F PREPARATION Herschel G. Smith, Wford, and Troy L. Cantrell, Lansdoe, Pa assignors to Gulf Oil Corporation, Httsbnrgh, h a corporation of Pennsylvania No Drag. Application December 22, 1941, S N0. 424,086

This invention relates to improvement agents for lubricating oils and methods of making the same. In the lubrication of internal combustion engines of all types, particularly when severe operating conditions are encountered, plain mineral oils often prove unsatisfactory, due to the attendant deposition on the engine surfaces, such as cylinder walls, pistons and rings, of "varnish, gum, or sludge. This effect is particularly serious in modern engines operating under severe conditions, such as Diesel engines, aviation, truck and tank engines. The problem has become increasingly serious due to the trend toward higher efiiciency, or higher power output per unit weight per engine, reduction in. amount of all employed in the lubricatmg system of the engine, and other conditions which tend to accelerate the deteriorating influences on mineral lubricating oil.

Formation of so-called varnishes and sludges on engine surfaces is due to oxidation or polymerization efiects (or both) on thelubricatihg oils, as well as to like efiects on or from products of combustion of the fuels, which find their way by leakage into the engine crankcase and other parts of the engine.

The presence of these substances is disadvantageous for many reasons. In particular the oil and fuel oxidation products tend to increase ring sticking and production of deposits on piston surfaces and in iixed parts of the combustion chamber. Sludges are formed in the crankcase of the engine, and the rate of corrosion of hearing surfaces is increased, especially with bearing alloys of the types now in use.

Petroleum olls' intended for use under the severe conditions described are almost always compounded with a mixture of substances each intended to counteract one or more of the undesirable efiects noted. These "substances, which fall into a wide variety of chemical classifications, are known by the general term improvement agents or addition agents, Preparation of satisfactory compounded lubricants is a matter of considerable dimcultyr some of the agents are of low potency in that rather large amounts have to be added to achieve the desired result. Often two or more agents are more or less incompatible with each other; and their rather low solubility in general further adds to the difiiculties in preparing a useful lubricant.

One object of the present invention is the provision of an improvement agent for engine oils which can be incorporated in petroleum oils in efi'ective proportions and which imparts to the oil a plurality of functions hitherto obtainable only by use of two or more agents. Another object is the provision of such an agent which, in theform of a solution in petroleum lubricating oils, combines the functions of (1) acting as a negative catalyst to suppress the formation of deterioration or oxidation products, such as varnish, sludge and gum, (2) acting as a loosening or suspendingagent (detergent) to prevent ring sticking, varnishing or coating of metallic surfaces -by such reduced amounts of deterioration products'as may be formed, and (3). acting as a suspending or dispersing agent for retaining very small particles or solid particles of deterioration or contaminating materials in the oil; for example, particles of carbonaceous matter that find their way into the oil by passing the rings, which cannot possibly-be made absolutely tight. Another object is the provision of an improvement agent capable of increasing the solubility or dispersibility of other agents such as straight soaps or the like, when it is desired also to add such compounds to an oil.

According to the invention, agents capable of achievingtnese and other objects of the invention are prepared-by bringing into reaction sulfophospho-derlvatives of higher fatty alcohols, with lime (or other metal oxide or hydroxide), under conditions producmg a, complex metallic compound of such derivatives, of nature described in more detail below.

The compound in solution in a lubricating oil provides four functions, so to speak, in a single molecular structure. (1) By virtue of its combined metal (e. g. calc um) suspending and detergent properties are imparted and resistance to ring-sticking, (2) the combined phosphorus nrlparts anti-bearing-corrosion and anti-ring.- sticking properties, (3) the combined sulfur serves to give pressure-carrying properties to the oil and to retard corrosion of alloy bearings, and (i) by virtue of the organic nucleus, the highmolecular-weight fatty alcohol, the oil has good I anti-oxidant and oiliness properties and suspendvided a compound which dissolved in oil imparts thereto all the many desirable features which we wish to obtain. It is in a form which is so soluble in motor oils of all types and degrees of refinement that we can incorporate any desired proportions to form a stable clear solution in lubricating oils; even in the most highly refined and most paraffinic of the heavy aviation oils, such as are specified for the most severe and exacting aviation service. It is a. known fact that highly parafiinic oils, refined to the high degree desired to secure such properties as low carbon forming effects and the like as well as high viscosity index values (improved viscosity temperature relationships) that are preferred for such service, exhibit in use less solubility fordecomposition products encountered in use, while there is increased tendency to induce bearing corrosion, due to the fact that in such highly refined oils less protective effects are developed. In the invention, we attain the desired objective by the use of moderate amounts of the compounding agent having cumulatively all the desired properties, in the way ofready solubility in the oil and the other effects mentioned above. We can employ very highly refined parafiinic type aviation oils that have the desired superior physical characteristics as regards the oil proper, and, at the same time, avoid any undesirable effects whatever from the use of such heavily refined paraffin type oils. In other words, the addition of our compound which is soluble in all proportions in the heavy highly refined parafilnic oils enables us to secure all of the properties desired in the way of the oils of superior performance characteristics, as well as the effects of detergency, avoiding of ring sticking, varnish formation, sludge formation, and corrosion of alloy -bearings, that might otherwise be encountered, as Well as to secure the desired eifect of retarding oxidation due to the use of more highly refined oils of less tendency to oxidize combined with the use of a compound which actually retards oxidation.

Another important field of utility for the invention is in Diesel lubricating oils. Heretofore it has been considered best to use naphthene type oils, dosed heavily with less effective or less concentrated types of compounding agents which are not so readily soluble even in the more naphthenic type of Coastal oils. necessary to make a compromise, even for the Coastal oils of greater solubility effect for compounding agents, between the degree of refining, and the solubility efiect for the addition agents. It is quite unsatisfactory for most of these agents to use even a moderately refined parafiin type oil, as all or part of th addition agents will often separate from the oil upon standing. For these reasons Diesel lubricating ,oils hitherto prepared have been rather unsatisfactory in that they employ lower grade oils of less degree of resistance to oxidation than would,

compound in any desired proportion.

A convenient source for the principal reactant, the higher molecular weight monohydric alco- It has often been.

hols, is sperm oil, the alcohols being obtained therefrom in known ways. As is well known, sperm oil is a liquid wax, and not a fatty oil. It is composed largely of esters of high molecular weight monohydric alcohols, as distinguished from fatty oils which are esters of apolyhydric alcohol (glycerol). The sperm oil esters have the following general formula:

wherein R and R are aliphatic chains of high molecular weight each containing a double bond. The acids are mainly oleic acid and homologous acids of the oleic type and the alcohols are monohydric alcohols of the ethylene series-the series of alcohols corresponding to the oleic. series of acids. Sperm oil alcohols have the probable formula Gravity A. P. 1-- 36.0

Viscosity, s. U. v.,21o F 3*? Pour F Color, N. P. A 1 Neutralization N0 0.01 Iodine No., Mod. Hanus 55.5 Saponification No 0.6

Other high molecular weight monohydric alcohols such as oleyl alcohol and the like can be employed in lieu of sperm oil alcohols. Among other useful alcohols are those derived from wool fat or degras, C1oH19OH; and from lanolin or purified degras, C12H23OH; glutinol, C14H27OH from the wax of the elder leaves; vitol, C1'1H33OH occurring in grape leaves; and cerosine, C24H-l7OH recovered from sugar cane bagasse. This invention is not limited to the naturally occurring higher unsaturated type alcohols, but to the use of any higher unsaturated type alcohol regardless of origin. We can also employ high molecular weight saturated alcohols, such as lorol alcohol derived from coconut oil fatty acids.

While these high molecular weight alcohols are relatively inert, by the expedient of treating them with phosphorus pentasulfide, they can in effect be combined in stable form with a rather. large proportion of lime or other metal.

In proceeding in accordance with the invention, the sperm oil alcohols or their equivalents are brought into reaction with phosphorus pentasulfide (P285) in proportion about 10 to 35 parts, and parts of the alcohols, with maintenance of the reaction temperature at 300 to 460 F. When reaction is complete, hydrated lime is mixed in, in proportion between one and 15 parts, and heating is continued at a temperature of 300 to 320 F. for about one hour. The reaction mixture is filtered and is then ready for use.

even our is This product is of complex constitution, when but a single alcohol is employed.

given a probable structural formula for the hexa- It seems probable that similar or homologous compounds in our reaction product have vng proportions of the components (combined phosphorus, sulfur, etc.) but the average edect is what might be expected from a molecular structure as above. As a matter of fact, we vary the relative proportions of the reactants depending upon the particular properties desired. There is considerable flexibility in the proportion of calcium added for securing a range of degrees of detergency, anti-ring-sticking, or solid suspending efiects; or in the amount of combined phosphorus as required for anti-ring-sticlring and anti-corrosion effects; or in the amount of combined sulfur for varying the efiects as to the pressure carrying and corrosion retarding oralloy bearings. Although the structural formula, indicates a quantitative relationship between the various elements,

it must be understood that these various constituents can be varied at will; that is, the sulfur con= tent can be made greater or less than the phosphorus content, and the amount of metal can be made to vary over relatively wide limits.

The physical identifying characteristics or" our preparation generally fall within the ranges indicated below;

Gravity A. P. I-.. ill-20 In lieu of ordinary lime, dolomitic limes or magnesia or magnesium hydroxide can be employed; and other metallic oxides or hydroxides such as alumina or zinc oxide. i dono-, diand trivalent metal compounds and mixtures thereof are useful.

The optimum proportion of the agent to be put into lubricating oils depends on the severity oi the service conditions and the degree to which the oil itself tends to form gum and varnish. Ordinarily from 0.25 to 5.0 per cent is suitable.

Example 1.-ln a specific example illustrative of one good way of preparing the agents or the invention, 100 parts by weight of the sperm oil alcohols as described above are placed in a stir= ring still and heated to 250 it; while stirring at that temperature 17 .7 parts by weight or P255 are added, and the mixture is heated to 300 F., and agitated one-halt hour. A mixture of parts hydrated lime, Ca(OH) 2, and 1 part water is added slowly with agitation The mixture is heated to 300-320 F. for one hour, then filtered to re- The product Example 2.-An improved lubricating oil was prepared by dissolving 1.0 per cent of the preporation or maniple i in a high grade lubricating oil for use in Diesel engines.

Tests were run on the straight oil and the compounded oil to compare their behavior under service conditions. For this purpose a test onsine in the form of a standard Waukesha-CFR crankcase with special L-head type cylinder block was employed, coupled to a cradle-type electric dynamometer. This engine has a bore of 3% inches, a stroke of d /z inches, and a compression ratio of 4.7:1. The piston is of cast iron (except in testC below) with four compression rings and one oil-control ring, all located above the wrist pin. Three liters of the oil to be tested are placed in the crankcase. The engine is then run at a controlled speed, with the spark and the air-fuel ratio adjusted to give maximum power. and the coolant temperature is maintained at a fixed valus. At the end of the test the engine is stopped and dismantled and the piston is examined. The performance of the oil is then rated according to the condition of the piston, in keeping with the following scale, in which th rating number increases asthe piston condition becomes worse:

Piston condition performance rating No. l-No ring stuck, and no heavy hard deposit. 2--Topor oil ring (or both) stuck on a small part of circumferncej1.

3-Top or oil ring (or both) completely stuck.

d-Top or oil ring (or both) completely stuck,

end ring partly stucln; I

5Top, 2nd and oil rings completely-stuck.

Mondition No. 5 with 3rd and 5th rings partly stuck.

' but is run until the engine power output as measmod by the dynamometer is observed to drop; this being indicative or ring sticking. The test is reported in terms of the number of hours running time until the mwer output begins to fall acteristics, of the plain oil and the compounded oil.

. Oil con- Unmgiillbitcd tainipg 1% additive Gravity A. P. I. 28.9 28.9 \iscosi U.

100 l, 487 1. 489 210 F 117. 7 117.3 Viscosity index 104 104 Flash, 0. 540 525 Fire, 0. C 615 615 Pour 0 Color, N. P A 2. 75 2. 75 Carbon residue 0.25 0. 33 Falex Wear test:

500 lb. ga e load, min

car 22 0 Motor oil service test A:

Piston rating 4 1 Used oil (after hrs. use)- Gravity A. P. I 27.8 27.9 Viscosity, S U V 100 F. l. 666 1.678 124. 2 124. 2 "iscosity index 102 101. 5 Flash, 0. C F 525 535 Fire, 0. C. F 015 630 Pour F.. 0 0 Color, N. P. A. I 4. 25 l 5.0 Carbon residue .per cent. 0. 49 0. 62 Precipitation under centrifuging... Trace 'lrace Neutralization N o 0. (in 0. 56 Sludge .per cent. 0. U3 0. (l2 Falex wear test:

500 lb. gage load. 15 min.

Wear: No. of teeth l3 0 Motor service test B: Oil rating. hours 19 08 Motor service test C: Oil rating lo 22 58 Motor service test D: Oil rating... do 18 T2 An important advantage of the agents of the present invention is that, in addition to being highly oil soluble themselves, they are effective to disperse in mineral oils certain soaps which are of themselves difficultly soluble; for example calcium oleate and aluminum stearate. Sulfurized sperm oil soap is a desirable addition agent to oils, but its low solubility prevents incorporation of more than a rather small quantity into paraflin base oils. According to the present invention one per cent or more of such soap can be dispersed in oil, to form a stable and permanent dispersion, by including an equal amount of the new agent. While the improvement agent has been described in reference to compounding en-- gine lubricating oils for the purpose of preventing ring sticking, its field of usefulness is not confined to that application; it can be used in oils wherever its properties may be desired. Sometimes it is used for its dispersive powers on other agents, when its own antioxidant and detergent properties are not needed.

What we claim is:

1. A process of preparing an improvement agent for lubricating oils, from monohydric alcohols of the ethylene series, which comprises heating 100 parts of said alcohols with 10 to parts of phosphorus pentasulflde at temperatures between 300 and 460 F. until substantially all of the phosphorus pentasulfide has reacted and acid reaction products thereof are obtained, and then converting said acid reaction products into substantially neutral metal derivatives thereof by further heatingthe acid reaction products so obtained with a reactive metal compound of the class consisting of the oxides and hydroxides of a polyvalent metal, the amount of such polyvalent metal compound being in excess of that required to neutralize the acidity of said acid reaction products and the mixture being heated at temperatures between 300 and 320 F. until stable, substantially neutral metal derivatives thereof are obtained, and separating the unreacted metal'oxides and hydroxides and other insoluble compounds from the oil-soluble improvement agent so obtained.

2. A process of preparing an improvement agent for lubricating oils, from monohydric alcohols of the ethylene series, which comprises heating parts of at least one such alcohol and 10 to 35 parts of phosphorus pentasulfide at temperatures between 300 and 460 F. until substantially all of the phosphorus pentasulfide is reacted and acid reaction products thereof are obtained, adding to such acid reaction products a reactive metal compound of the class consisting of polyvalent metal oxides and hydroxides in proportions stoichiometrically equivalent to 1 to 15 parts of Ca(OH)2, maintaining this mixture at a temperature of 300 to 320 F. for approximately one hour and filtering the oil-soluble reaction products so obtained to remove unreacted metal oxides and hydroxides and other insoluble compounds.

3. The method of claim 1 wherein the metal compound is lime.

4. The method of claim 1 wherein the alcohols are sperm oil alcohols.

5. An improvement agent soluble in petroleum oils and capable of inhibiting formation of gum, varnish and sludge in engines and of dispersing such deposits when present, comprising the substantially neutral, stable, oil-soluble, metallo compounds obtained by the process of claim 1.

6. An improved lubricating composition comprising a major amount of a mineral lubricating oil and a smallproportion of the substantially neutral, stable, oil-soluble metallo compounds obtained by the process of claim 1, the amount of said improvement agent being suflicient to inhibit the formation of gum, varnish and sludge in engines and to disperse such deposits when present.

HERSCHEL G. SMITH. TROY L. CAN'IRELL.