US2281401A - Lubricating oil composition - Google Patents

Description

atented Apr.

LiTBRHCATENG @H- EJQPIEQSH'EION fflhester E. Wilson, San Pedro, Calif.

' No Drawing. Application November 21, 1939,

Serial N0. 3i5,195

17 Claims.

This invention relates to mineral lubricating oils which have been modified by the addition of constituents to impart to them special characteristics especially adapting them to severe service uses such. as are encountered in Diesel engines, high output aviation engines and the like. This application is a continuation-in-part of my copending application, Serial No. 277,677, entitled Modified lubricating oils.

In Diesel and similar engines the high temperatures developed in the cylinders tend to act upon lubricating oils to cause the deposition of resinous and varnish-like products on the pistons and elsewhere to produce lacquer-like coatings and carbonaceous materials, which tend to cause ring and valve sticking and interfere with engine operation. Furthermore, fuel residues from incomplete combustion of fuel contribute to the deposition of lacquer-like and carbonaceous materials in the engine. Previously in an effort to overcome these difiiculties various types of metal often given rise to hearing corrosion, such corrosion apparently being due tothe formation in the oil of corrosive materials of acidic character. The formation of these corrosive materials may even be catalyzed by the presence of such soaps in the oil. Also, some of the metal soaps added as detergents have required the use of free fatty acid and the like to act as a common solvent to promote solution of the soaps in the oil, and the presence of such free acidity has possibly contributed to the corrosion of alloy bearings of the type mentioned above. Primarily, the object of this invention is to produce for such severe service conditions as are encountered in Diesel engines, lubricating oils which will be non-corrosive to corrosion sensitive bearings of the copper-lead and cadmiumsilver type and which will also avoid the deposition of lacquer and varnish-like materials upon pistons and overcome carbon deposition behind the rings.

The present invention resides in mineral lubrieating oils containing small amounts in the order of about 0.5% or 0.75% up to 2% or 3% of oilsoluble metal salts of the weakly acidic non- I of reacting with acidic corrosive materials formed or present in the oil during use to form metal salts of such corrosion products and liberate free non-carboxylic acids which are sumciently weak to be non-corrosive to bearings of the copperhigh as 1 X 10-. It may also be possible, at least for some uses, to employ those weakly acidic materials having ionization constants up to about 5x10 but in no case so far as now known can about 5 l0- be exceeded; this limit safely excludes the carboxylic acids. Such compounds comprise the phenols, thiophenols, other enols, oximes, sulfonamides having an acidic hydrogen atom, and the like, detailed hereinafter,

Although any of the oil-soluble metal salts of the above mentioned groups of compounds will be effective in preventing the corrosion of bearings such as those of cadmium-silver and copper-lead alloys and will tend to prevent the deposition of carbonaceous materials in the engine, I particularly prefer to employ the oil-soluble metal salts of phenols.

By the term phenols it is meant to include not only the hydroxy aromatic ring compounds in which an hydroxyl group is directly attached to a carbocyclic aromatic ring, but also heterocyclic compounds in which the hydroxyl group is attached to a ring containing a. sulfur, oxygen, nitrogen or other atom and in which the hydrogen of the hydroxyl group so attached is sufficiently acidic to give the compound an ionization constant within the range defined above, said compound being capable of forming an oil-soluble metal salt. It is to be further understood that the term pheno includes not only monohydroxy but polyhydroxy compounds and those in which more than one ring is present, such as naphthols and the like. In addition to the hydroxyl group or groups, the ring is preferably substituted by one or more other substituents such as for example, an alkyl group or a sulfur atom linking two phenolic radicals together such as in di-para-tertiary-amyl diphenolsulflde, the

, upon piston rings, valves and the like.

only limits being that the compound must be non-carboxylic, and must contain at least one hydroxyl group of sufficient acidity to exhibit an ionization constant Within the limits described above, and must form an oil-soluble metal salt. For the sake of simplicity in the following specification and claims, these compounds will be referred to merely as the metal salts or metal compounds of phenols.

Although it is not definitely known why the metal salts oi phenols act to prevent corrosion of alloy bearings and I do not wish to be bound by the theory, it is presumed that this inhibiting power is at least in part connected with the ability of the salts to react with the corrosive acids formed or present in the lubricating oil, to form non-corrosive metal salts of the corrosive acids, thereby liberating the non-corrosive, weal;- ly acidic phenolic compounds. As an indication oi the manner in which the above mentioned compounds are presumed to react to neutralize corrosive acidity, thereby rendering the oil ncn= corrosive, the following exemplary equation may be given:

a hydrccarhon radical, 11 1 represents a metal, 2 represents acid radical of a corrosive acid, and Tel represents a replaceable or acidic hydrogen All oil-soluble metal salts oi phenols, dissolved in lubricating oil will tend to inhibit the corrosion of bearings of the cadsniuni silver and eopper lead type. These include, and I may e n= ploy, the oil-soluble Li, Na, K, Cu, Zn, Mg, Ca, Sr, Pb, ill, Co, Evin, Sr, Sn and Fe salts oi the phenolic compounds. particularly preifer to employ the alkaline earth salts, calcium, barium, magnesium strontium, and probably also the aluminum and zinc salts, of the phenolic com pounds because of their greater solubility oil. and their possibly lower catalytic activity.

My invention, therefore, resides also in a lubrieating oil containing a small amount of an oil= soluble metal compound oi a phenolic compound either alone or in combination with other constituents, for example, those adapted to the oilinesscr film strength or" the oil or even a neutral common solvent, such as the higher boiling alcohol ethers adapted to increase the solubility of the metal salt in the oil.

this equation 3. re resents The mineral lubricating oil employed may be a California or a naphthenic-type oil which ordinarily contains about 0.5% of organically combined' sulfur, but may contain as little as 0.15% of such sulfur. Higher sulfur content oils such as those derived from Santa Maria Valley (California), crude oil containing up to 4% or even 5%, for example, 2.75% of such sulfur, are sometimes very desirable. This sulfur also tends to inhibit bearing corrosion and the formation of the acid condition causing it, as elsewhere herein indicated. With metal salts of adequate oil solubility, as in the case of the calcium salts of phenolic compounds containing hydrocarbon side chains attached to the ring, as indicated below, the base may be a well refined paramnic-type oil.

Toe oil-soluble metal salts such as the calcium salts of the phenolic compounds are employed in Also, the invention includes the use of these compounds in lubricating oil in the indicated proportions, in combination with small amounts of other types of oil-soluble soaps having detergent properties in the engine in propor= tion suficient to overcome or greatly retard the deposition of resinous and varnish-like materials Such soaps may be used in amounts in the order of 0.5% to 1.0% as required to accomplish the re sult desired. Such soaps are produced from soa forming fatty acids and modified fatty acids such as the calcium and magnesium soaps of phenyl stearic acid and chloro stearic acids, and from naphthenic acids, rosin acids, modified rosin acids, and. synthetic petroleum acids formed by the oxidation of petroleum fractions such as highly solvent-treated parafiinic type lubricating oil fractions, parafin waxes, petrolatum and the like. Other metals may be used for soap production, as heretofore indicated, where sumciently oil soluble soaps are produced. 7

* in the benzene rings.

the lubricating oil in amounts up to about 3%, but in amounts less than that required to cause an undesirable thickening of the oil, the optimum apparently being from about 0.5% to 2.0%.

A specific usable phenolic material of which l have produced the calcium salt is ell-para tertiary-anlyl. diphenol sulfide, which apparently as formula:

CH3 CH3 (3 HO CH3 llliiyl hydrouyl phcnyl thio ethers of this type are described in the ltfilreslza et al. Patent No. 2,i3:2-,l66 and other similar compounds and their method or preparation are given in Milreslza et al. Patent No. 2,139,321.

A phenolic material believed to be kindred to that of the Mihesha et al. Patent No. 2,139,766, is present obtainable on the market under the trade-name Paranou" which is available from the Standard Oil Development Company. This material, apparently, is in general composed of mixed poly=allryl poly-phenol sulfides, that is, poly-allzyl substituted hydroxy phenyl thio ethers containing, for example, a thio ether oi butyl phenol which may be designated as Bis (2-hydroxy-l-butyl phenyl) sulfide. product apparently contains various materials oi the following general formulas:

diflerent for the different components of the mixture or may be diiierent for the two or more benzene nuclei in one oi? the components. It, 8 and OH may occupy any of the possible positions higher polymers such as indicated in the second formula above, and even more extensively poly mer ized materials.

The metal salts of the above described phenolic materials may properly be considered soaps because of an apparent detergent action. When about 1% or between about 0.5% and about 2.0% oi such a suitable oil-soluble compound such as This commercial The material may contain aasiaoi as an agent for preventing the corrosion of bearings such as those oi cadmium-silver and copperlead alloys.

' The invention, therefore, also includes the use of oil-soluble metal salts or compounds of the indicated phenolic type of sulfur-bearing acidic materials, particularly the calcium compounds. It also resides in the use of between about 0.5%

and about 3.0% or such soaps in mineral lubri- I eating oils and especially between about 1.0% and about 1.5% of the calcium compounds of the alkyl polyphenol sulfides or polysulfide materials described, especially where the lubricating oils are for use in Diesel engines or other severe service equipment.

In practicing this phase of the invention commercially, the compounds of suitable phenolic compounds such as the calcium compounds of di-. butyl or other alkyl or mixtures of alkyl phenol sulfides above indicated may be formed without particular diiliculty by any suitable procedure, as

' will be obvious to the skilled chemist. For example, the calcium salts of these compounds may be conveniently obtained by first adding the starting material to an approximately equal quantity or even greater quantity of a suitable lubricating oil such as a naphthenic base mineral oil having good solvent properties forthe phenolic material and for the salts to be produced. This all mixture is then commingled with hydrated calcium oxide and asmall proportion of water, followed by heating to about 300 F. with agitation for a time sufiicient to insure neutralization and dehydration. The resultant mixture is filtered to remove solids such as excess calcium oxide. The ash (calcium content) has been increased when desired by first heating only to about 200 F. to 210 F. for a time to insure complete admixture and partial neutralization, the mixture being then cooled to 150 F. to 170 F. a d a small quantity in the order of about 3% of 95% alcohol added, and the'temperature of the mix then raised to the previously mentioned temperature or 300 F. Another method employed has been to neutralize thealkyl phenol sulfides with sodium hydroxide and then by metathesis with calcium chloride or the like, convert the sodium salt to the calcium salt. In preparing for treatment of the Paranox described above as probably comprising a mixture of alkyl phenol solildes, about of the sulfides should appear in about 80% of lubricating oil having good solvent power ..-for the soap. Otherwise, a greater proportion of lubricating oil is added as its soapdissolvingpower decreases. The above described neutralization to produce the calcium salts thereof is more or less easily accomplished due to the fact that the pure phenolic material has been found to have an acid number of about 98. The other alkaline earth metal salts may also be readily-produced in a similar manner. In'pre paring soaps of other metals previously mentioned, the metathesis procedure just mentioned may be preferable as will be readily determined by the skilled chemist.

These salts are readily soluble in lubricating oils in the required proportions and yield alkaline solutions. Representative salts thus proformation of objectionable duced appear to have the following structural formulas:

and

5 to I Ca 5 is In preparing Diesel engine lubricating oil according to the or the compound-oil mixture, is stirred into an appropriate mineral lubricating oil and solution is efi'ected by agitation, a slight elevation of temperature being produced if desired to facilitate the solution operation. I

When the calcium compound is dissolved in the lubricating oil to yield in the final product a compound content in the order of about 1% to 1.5% or in amounts from about 0.5% up to about 3.0%, the detergent action of the resultant -lubri eating oil is sufllcient to overcome or prevent the deposition of the objectionable amounts of said resinous and varnish-lik materials above men-' tioned, and at the same time this quantity of compound is insufllcient to substantially increase the original viscosity of the base mineral lubrieating oil. Not only do the calcium compounds of these alkyl phenol thlo-ethers produce such detergency and thereby prevent sticking of rings and valves and the deposition of varnish-like coatings, but at the same time they prevent the corrosive acid conditions which attack materially the highly corrosion-sensitive alloy bearings of the copper-lead type.

In addition to the general functions of a compound which are imparted to the oil by this cal-' cium compound, the presence of the sulfur in the compound molecule tends to impart to a nonsuli'ur-contalning lubricating oil, extreme pressure characteristics, and the small percentage of actual sulfur present in the compound further acts to impart in itself some anti-corrosive properties.

In additional to the calcium"soaps of the phenol thio-ethers indicated, compounds of other metals of the alkylated phenol thio-ether may be employed such as those of barium and magnesium and also zinc, and aluminum, the important requirements being good solubility in the chosen mineral lubricating oil, detergent properties and freedom from appreciable viscosity increase when used in detergent quantities such as the indicated range from about 0.5 to 2.0%. Also, these metals appear to possess less undesirable catalytic activity than some of the heavier metals previously mentioned such as lead. Compounds of other phenol ethers such as alkyl-substituted phenol selenium or tellurium others or the like containing other suitable sulfur substitutes in the ether position are also within the scope of this invention for some uses where possessing suflicient solubility in oil and adequate detergent properties.

a invention the compound. I

I have also found that amyl phenol can be condensed with formaldehyde under appropriate conditions to form a viscous polymer in which free hydroxyl groups of the phenolic type are present. By dissolving this resinous phenolic material in nine volumes of lubricating oil and saponifying by heating with an excess of hydrated lime, followed by dehydration and filtration in the manner described above, I have been able to form the calcium salt of this phenolic resin. When about 1.5% of such a suitable oil-soluble calcium salts was dissolved in mineral lubricating oil it was found to possess the required detergency characteristics and, at the same time, acted to prevent the corrosion of bearings of the cadmium-silver and copper-lead. type.

Further, I have found that stearyl alcohol can be condensed with phenol (monohydroxy ben= acne) in the presence of concentrated sulfuric acid to form a compound believed to be parastearylphenoi. The calcium salt of this com pound has likewise been readilyformed in the manner described hereinabove and a lubricating oil possessing about 0.65% ofthe calcium salt of stearylpnenol has exhibited the desired detergent and corrosion-preventing properties.

In the foregoing disclosure, the oil-soluble metal compounds of phenolic compounds have been preferred, but it is to be understood that the oil-soluble metal compounds of other weakly acidic, non-carboxylic compounds having ioniza= tion constants within the range specified hereinabove are equally satisfactory and are within the scope of the present invention. As group ex amples oi other such weakly acidic, non-cam boxylic materials, the phenols, thiophencls, other enols, crimes, sulionamides and the like were previously mentioned.

following are specific examples in addition to those given above of suitable acidic materials from the classes just mentioned, and include and and a1 :yl substituted phenols and others of the classes mentioned.

In these instances the designation of the vari ous groups by m and 'n is to provide the respec= tive molecules with. sunlciently high molecular weights to yield compounds of good solubility in oil. Where the molecule has two rings, it appears that the molecular weight of a compound of good oil-solubility is around 350 or higher. There may be some instances where a compound of as low as 300 molecular weight will be sufflciently oil-= soluble, but such apparently is not true of all cases. In general the same lower limits of molecular weights has been taken as representative of compounds of suitable acidic materials of other chemical configuration. Varying values for m and it also indicate complexity in the molecules, which appears to be a desirable fea ture imparting greater oil-solubility. Branching appears to promote oil-solubility. Further, mix== tures of different molecules in which the allryl' groups vary appear to have better oil-solubility than materials representing a single molecule. Thus, these materials may contain alkyl groups (or aryl groups where indicated) in which n, or m and n combined, may be smaller when the molecules otherwise have relatively high molecular weights, and larger when the molecules otherwise have relatively lower molecular weights. In general it may be said that m and n will have values from zero to perhaps as high as 20 or possibly higher for molecules otherwise of low molecular weight, and from zero to perhaps about ill for molecules of otherwise higher molecular weight.

5 to avoid undesirably high molecular weights.

iii

The following examples of these materials are arranged according to groups above mentioned:

, i. Phenols (a) ll/ionohydrony phenols cannons a (CHQsCHt uoQwmm onlcncncnz CH3 uoOirnwnmQ-wnmcm (l2) l clyhyorouy phenols I Ca e C3156 emcee; car lon-n l ii l an i (31:1 i 4 l l --r l n E l at.

i CE:

I mm M I C a UM. QEQ

(condensation oi and icrmaldehyde.)

(3H2 noOomcnm-jawnnmm l o K (As in condensation of oleyl alcohol and phenol) R F l R UH LEO s ii. on.

(R mas represent groups from propyl to decyl for example.)

, on no on no Here, R represents either an eryl group, such or an alkvl group, such as amyl, butyl or other aeeneoi and the like appear in place of (c) Condensed ring phenols 1. Products of the type in (a) .and (b) above in which and the like appear in place of (d) Heterocyclic phenols 1. Compounds of the types in (a), (b), (c)

above, in which and the like appear in place of H. Thiophenols An OH group in the phenol compounds of Group I is replaced with SH.

III. Omimes (a) CH;(CH:).CH=NOH cmwnoflcwmnom NOH cmwmnnO NOE CHa(CHz)s-C CH=NOH IV. Sulfoncmides (a) v omwm) sommonmom cmwmwOsomH-Owm)on,

omwrmnOsomng VT. Imids (a) cm(om)..om-oo H om om),.om-oo HK Hz) /NH I 00 VI. Enols (a) crmcrn),o-o=cn-(om)..om i (b) cm(om moH=c -C -(om)...om-

Oil-soluble compounds or salts of these vari- 011s materials may be prepared in manners as outlined above and. added in indicated proportions to yield the type of product described and cod. Important requirements are good solubility of the compounds in oil in the proportions required, without substantial increase in the viscosity of the base oil, and low ionization constants as above defined with consequent freedom from development of corrosive conditions in the oil d :21; engine use which is presumed to be due to the indicated neutralizing character of the compounds which may be termed reserve alkalinity."

It will be understood that examples are given for purpose of illustration and not as necessarily limiting beyond the requirements of the prior art.

I claim:

1. A lubricant comprising mineral lubricating oil and a small quantity of an oil-soluble metal compound of a thiophenol having an ionization constant in the order about 1x10 to about 1x10- the oil containing also a small proportion of an oil-soluble detergent metal soap of a relatively strong saponifiable carboxylic acid.

2. A mineral lubricating oil for internal combustion engines containing a small proportion of oil-soluble corrosion-controlling metal compound of thiophenol not in itself corrosive to corrosionsensitive-alloy bearings, the compound being cap able of reacting with strong acidic materials of 3. A liquid lubricating oil for severe service.

internal combustion engines comprising mineral lubricating oil containing a small proportion of metal compound of a phenol thioether in quantity suiiicient to control development of corrosive conditions without imparting substantial viscosity increase to the base oil, the oil'contaifiing also a small proportion of an oil-soluble detergent soap of a saponifiable carboxylic acid.

4. A lubricating oil containing a small proportlon of oil-soluble metal compounds of a material from the class consisting of thioenols; the oil also containing a small proportion of an oilsoluble detergent metal soap or a saponlfiable organic acid.

5. A mineral lubricating oil for Diesel engines and the like comprising a minor proportion of an oil-soluble detergent metal soap of a saponiiiable carboxylic acid, and a minor proportion of an oil-soluble metal salt of an alkylated thio phenolic compound, the salt being capable of neutralizing corrosive conditions developing in an engine."

6. A mineral lubricating oil containing a small proportion between about 0.5% and 3% of an oil-soluble metal salt of an alkylated polyphenol sulfide, and a small proportion in the order of 1% of oil-soluble metal detergent soap of saponiflable organic acids.

7. A liquid mineral lubricating oil for internal combustion engines and the like which comprises a mineral lubricating oil containing in the order of 1% t oil-soluble corrosion-controlling metal salt of a. thiophenol having an ionization constant below about X and in the orderoi 1% of oil-soluble metal detergent soap of relatively stronger high molecular weight saponiflable carboxylic acid.

I a. A mineral lubricating oilcontaining a small proportion in the order of 1% of metal compound of alkylated phenol sulfide, and a small proportion in the order of 1% of a detergent soap of high molecular weight saponifiable carboxylic acid with a metal from the class consisting of alkali .metals and heavy metals.

9. A mineral lubricating oil for use in severe service internal combustion engines which contains in the order of 1% or an oil-soluble detergent soap of a saponifiable high molecular weight carboxylic organic acid of the metal or the class consisting of alkali and heavy metals, and be tween about 0.5% and 3% of a corrosion-connaphthenic acids, rosin and modified rosin acids.

and synthetic acids from the oxidation or petroleum Iractions.

13. An oil according to claim 6 wherein the soaps are alkaline earth metal compounds.

14. A freely fluid mineral lubricating oil containing a minor proportion of an oil-soluble metal salt of a phenol sulfide, the oil containing also a small proportion of an oil-soluble detergent metal soap of a relatively strong saponiflable carboxylic acid. 7

15. An oil according to claim 7 wherein the metal of the thiophenolic salt is from the class consisting of alkali metals and heavy metals.

16. An oil according to claim 14; wherein the metal of the salt of the phenol sulfide is from the class consisting of alkali metals and heavy metals.

1'7. An oil according to claim 4, wherein the metals of the additives are selected from the class consisting of alkali metals and heavy metals.

' CHESTER E. WI'ISON.