US2270577A - Compounded lubricating oil - Google Patents

Description

Patented eFan. 20, 1942 STES OFl

COMPOUNDED LUBRICATING OIL No Drawing. Application May 31, 1940,

Serial No. 338,238

12 Claims.

This invention relates to compounded mineral lubricating oils, and more particularly, deals with lubricating oils containing oil-soluble salts of polyvalent metals and certain hydrocarbon sulfonic acids, and in addition, certain oxidation inhibitors, which oils are substantially non-corrosive and possess the property of preventing sticking of piston rings in internal combustion engines when running these engines for long periods of time and under severe conditions of loading. It is known that in modern internal combustion engines, such as high speed Diesel engines and aviation gasoline engines, which, due to their high power output, operate at relatively high temperatures, piston rings have a tendency to become stuck in the grooves. Lacquer and/or carbon formation appear to be the principal reasons for this occurrence. The addition of small contents of certain oil-soluble carboxylic acid salts, such as polyvalent metal salts of fatty acids, naphthenic acids, etc., is known to reduce ringsticking tendency.

We have discovered that when adding oilsoluble salts combining polyvalent metals with petroleum sulfonic acids or other hydrocarbon sulfonic acids to mineral lubricating oils in suitable quantities, efiective anti-ringsticking lubricants are obtained. Metals suitable for our purpose are particularly the light-weight metals Mg, Ca, Sr, Ba and Al, and the heavier Zn. However, other polyvalent metals may be used, if desired, especially those having only one oxide, or one of several oxides which is much more stable than and is not. readily convertible to the others under ordinary lubrication conditions in internal combustion engines. For example, fair anti-ringsticking oils may be produced with Cd, Sn, Co, Ni, etc.

Oils containing our anti-ringsticking compounds in amounts sufficient effectively to suppress ringsticking ,are, however, corrosive, particularly to some of the newer types of bearing metals. The presence in lubricating oils of salts which combine certain of the metals with certain of the aryl sulfonic acids causes corrosiveness in freshly blended oils toward some of the newer type bearing metals, which corrosiveness is aggravated as the oil is used in internal combustion engines. Salts of other metals, particularly when combined with aryl sulfonic acids of relatively high molecular weights, may result in oils which when fresh and unused are non-corrosive and may even be anti-corrosive toward the same bearing metals. However, upon use as crank-case oils in internal combustion engines for more or less extended periods of time, these originally non-corrosive oils also become corros1ve.

The reason for this corrosiveness of the oils containing our active salts is not quite clear, since the sulfonates are substantially neutral compounds containing no easily hydrolyzable acids which might be set free and, being soluble in the oil, would render it corrosive as a matter of course. Moreover, the rapid increase in the corrosiveness upon use of the oil is difiicult to explain.

For convenience, we shall hereinafter refer to the corrosiveness exhibited by an unused oil as initial corrosiveness, and to the increase brought about by the use of the oil in internal combustion engines as induced corrosiveness."

Whatever the reason for the observed corrosiveness may be, we have discovered that the addition of oxidation inhibitors soluble in mineral oils to the extent of at least about .1%, inhibits at least initial corrosiveness, and many oxidation inhibitors prevent appearance of the induced corrosiveness as well.

For our purpose,' oxidation inhibitors may roughly be divided into two groups: the phenolic type and the aryl amine type. Of these two, we have found that the latter are in general more useful for our purpose. Especially valuable are those amines which contain at least one aromatic nucleus having two or more condensed aromatic rings. Thus, preferred anti-oxidants are, for example, the naphthylamines: primary, secondary or tertiary alkyl, aryl or arallgyl amine in which the alkyl, aryl or aralkyl radicals an attached to an aromatic nucleus or preferabl; to the nitrogen atom or both, such as phenyl alpha or beta naphthylamine, tetraline naphthylamine, alpha alpha, alpha beta, or beta beta dinaphthylamines, various phenanthryl, anthryl or picyl naphthylamines, xenyl naphthylamines, benzyl phenyl naphthylamines, diphenyl naphthylamines, phenyl xenyl naphthylamines, dixenyl naphthylamines; also various phenanthryl, anthryl or picyl phenyl amines, etc.

If desired, however, other oxidation inhibitors may be used as well, such as alkyl phenyl amines, diphenyl amines; or alkyl phenols, preferably containing at least two alkyl radicals in 2, 4 or 6 positions to the OH radical, at least two alkyl radicals being linked to the aromatic nucleus through a tertiary carbon atom; or alpha or beta naphthols, alkylated naphthols, phenols or naphthols containing ether, thio ether, etc., linkages, polyhydric alkyl benzenes or naphthalenes, such as alkylated catechol, etc. The latter type inhibitors successfully inhibit initial corrosiveness, but in general are less effective than the preferred amines in retarding or preventing induced 'corrosiveness, although there are some exceptions.

the inhibitors may also contain radicals comprising elements of the group consisting of S, P, or Cl, provided these radicals are attached in such a manner that they do not readily liberate corrosive compounds, such as frees, Cl, phosphoric acid, under conditions of lubrication to which crank-case oils are normally exposed. If desired, inhibitors may be employed containing both amino and hydroxy radicals. Also mixtures of different inhibitors are often very useful, for example, a mixture of a predominating amount of a preferred polycyclic amine and a smaller amount of'a hydroxy aromatic compound.

True corrosion inhibitors, such as aliphatic amino phosphates, do not in general inhibit either of the two types of corrosiveness, and in many instances greatly aggravate it.

However, small amounts of certain'of the corrosion inhibitors such as the high molecular weight polycarboxylic acids described in Moser U. S. Patents 2,124,628 and 2,133,734 may enhance the protective effect of the anti-oxidant. Moreover, the presence of small amounts up to about of so-called extreme pressure agents containing at least one of the elements selected from the group consisting of S, P and Cl attached in a manner so that no corrosive elements or compounds are liberated under the conditions to which lubricating oils are normally exposed during their useful life, frequently improve the effect of the oxidation inhibitors, particularly if the latter are free of these elements. As a general rule, the addition to the lubricating oil of a mixture of compounds, one of which is an antioxidant free from corrosive element and the other is an extreme pressure compound containing at least one of them, yields better results than a single compound which is both anti-oxidant and carrier for the corrosive elements.

Below are listed a few of the many known extreme pressure compounds which may meet the requirements of stability: sulfurized fatty oils, preferably of the drying or semi-drying type, such as cottonseed oil, soya bean oil, perilla oil, tung oil, sunflower oil, fish oil, sperm oil, etc.; sulfurized olefines, sulfurized dihydronaphthylene polymers; aromatic sulfides or disulfides; chlorinated wax, chlorinated terpenes, chlorinated fatty acid esters, chlorinated organic ring compounds as halowax oil, sulfur chlorinated fatty oils or hydrocarbons; esters of phosphorus acids as alkyl or aryl phosphites or phosphates; triaryl phosphides, triaryl methoxy phosphorus dichlorides; phosphorized sulfurized fatty oils or acids, etc.

It is known and understood that the stabilities of most of the above compounds vary a great deal with the methods of their manufacture and with the exact composition of the starting materials. Their ultimate suitability for use in my compounded lubricating oils lies entirely in their resistance to liberating corrosive compounds under lubricating conditions, rather than in their actual composition.

The amounts of the oxidation inhibitors to be added depend to some extent on the sulfonate salt in the oil. As a general rule, the content by weight of the anti-oxidant should not be less than /8 of the content of the sulfonates and should never be less than .1% of the oil.

Amounts as high as about 2% maybe used. In general, amounts from 25% to 1% are most desirable, larger quantities often tending to cause formation of considerable amounts of sludgelllre oxidation products of the inhibitors.

f'he contents of other supporting additives, such as' extreme pressure compounds or polycarboxylic acids described above, may vary over considerable limits. Polycarboxylic acids should be used in amounts less than half of the content of the sulfonate salt. However, it may be desirable to use an amount of extreme pressure compound greater than that of the salt, but below 10% and preferably not above 5% of the oil. There is no minimum requirement for these supporting additives because their presence, though often beneficial, is not essential.

The amounts of the hydrocarbon sulfonates which an anti-ringsticking oil should contain varies from about 25% to 5.0%, and preferably from 375% to 2.5%.

Petroleum sulfonic acids which may be used advantageously to produce the metal sulfonates of this invention are preferably of the oil-soluble type which are obtained, for example, in the treatment of relatively heavy mineral oils, preferably so-called parafllnic oils such as Pennsylvania or Mid-Continent gas oils or lubricating oils, with concentrated or preferably fuming sulfuric acid. In this kind of treatment, two types of sulfonic acids are produced-so-called green acids which are substantially oil-insoluble, and mahogany acids which are oil-soluble. It is the mahogany acids which we prefer to use for our purpose, although green acids may also yield certain oil-soluble salts which are applicable for our purpose. These acids constitute complicated mixtures of many different hydrocarbon sulfonic acids, many of which are believed to be of aromatic character, although others are probably of naphthenic and aliphatic origin. Some of them produce better anti-ringsticking salts than others. In order to isolate the most effective components, the oil-solubleacids or their salts may be subjected to a fractionation by countercurrent extraction with two mutually immiscible solvents, a hydrocarbon liquid such as toluene, benzene, xylene, naphtha, kerosene, etc., and a water-soluble organic solvent such as a lower alcohol, glycol, glycerine, the latter preferably containing some water. The active component of the mahogany acid is concentrated in the hydrocarbon solvent. This method of separation has been described by Retailliau in U. S. Patent 2,158,680.

If desired, lubricating oils containing the sulfonic acid salts may also be produced by heavy acid treatment with concentrated or fuming sulfuric acid of a suitable lubricating oil, separating precipitated and suspended sludge, and neutralizing dissolved sulfonic acid with lime or other oxide or hydroxide of a suitable polyvalent metal.

While in general we prefer the oil-soluble petroleum sulfonates produced from so-called paraflinic crudes, those obtained from naphthenic or asphaltic crudes may also be used.

Other oil-soluble hydrocarbon sulfonic acids suitable for our purpose may be produced by sulfonating alkyl aromatic hydrocarbons, such as alkyl benzenes, alkyl naphthalenes, alkyl anthracene, alkyl phenanthrenes, alkyl picenes, alkyl chrysenes, alkyl diphenyls, etc., provided the number of carbon atoms in the alkyl chain or chains is suilicient to render the resulting sulfonic acids and their salts soluble in hydrocarbon oil. It is desirable that at least one alkyl radical be relatively long, i. e., contain at least 8 or more carbon atoms, not only because of solubility in catalysts, sulfuric acid, P205, phosphoric acid, etc.

The hydrocarbon sulfonic acids may, if desired, contain substitution radicals such as hydroxyl, primary, secondary or tertiary amine, ether,

, sulfide hydrosulfide, disulfide, halogen, etc., radicals which may be attached to the ring or to side chains or both. For example, excellent for our purpose are paramn wax substituted naphthalene mono sulfonic acids which contain a sulfonic radical attached to one ring of the naphthalene nucleus and a hydroxyl or amino radical attached to the other ring.

It is of interest to note that in general corrosiveness which is caused or induced by the sulfonates of this invention is much more readily and more lastingly suppressed than the corrosiveness of the salts of the same metals with carboxylic acids, such as fatty, aromatic fatty, naphthenic, rosin, etc., acids, known to have outstanding anti-ringsticking properties.

Our sulfonates can be made soluble in any type of mineral lubricating oil ranging from the lowest to the highest V. I. This is in marked contrast to many of the commercial anti-ringsticking salts of carboxylic acids which are soluble only in low V. 1. oils. The importance of being able to produce both high V. I. and low V. I. oils having good anti-ringsticking properties cannot be overestimated, because in certain types of Diesel engines, low V. I. oils simply will not stand up, while in other types of Diesel engines, low V. I. oils give as good or better results than the oils of higher V. I.

Salts suitable for our purpose must be free of free acid, and may be normal or basic. In general, it is preferable to employ a mixture of normal and basic salts. that sulfate esters be absent, as they are liable to liberate sulfuric acid which may cause corrosion, or precipitation'of at least a portion of the metal component of the sulfonate, or both. If necessary, the sulfonic acids may be subjected to a hydrolyzing treatment before use in the compounded oil, to eliminate sulfate or other harmful esters which may be present. If desired, salts of two or more of metals may be employed.

The following examples further illustrate our invention:

Example I It is also highly desirable Example I! The induced corrosiveness of various oils containing the calcium petroleumsulfonate of Example I and different oxidation inhibitors was determined by a test which we call the inertiabearing test. This test is conducted as follows: Two automobile connecting rods are mounted on a shaft which is machined to give a throw of one-half inch (radius) to the connecting rods. One rod is fitted with a copper-lead and one with cadmium-silver bearing. An inertia load of steel discs is fastened to each connecting rod.- The small end of each connecting rod is connected to a hinged link. The shaft on which the bearings are mounted is driven by a synchronous electric motor. Two fly wheels are mounted on the shaft in order to reduce vibration. An open sump is steam jacketed to provide heat and an auxiliary electrical heater, with a variable resistance in series with the heater blade, provides additional heat and temperature control. A pump circulates the oil through the system. The sump is charged with one and three-fourths gallons of the oil to be tested. After the oil has beenbrought to 225 F., the pressure to the bearings is adjusted to 20 pounds per square inch and the machine brought up to the testing speed of 2450 R. P. M. which is maintained for 25 hours.

In the table below are given corrosion data in mg. loss of bearing/sq. cm. of bearing surface, obtained when testing by the above inertia-bearing test the crank case drainings of the several oils run for 20 hours in an International or a Caterpillar Diesel engine. All oils, with the exception of the one which contained no oxidation inhibitors, were initially non-corrosive.

, Drainings fromg Oxidation inhibitor International Caterpillar Cir-Pb Cd-Ag Cu-Pb Cd-Ag 30 None 13. 6 1. 3 30 25% phenyl alpha naphthy amine; 4. 3 1 30 .5% phenyl alpha naphthylamine 1. 3 2 30 .75% phenyl alpha naphthy amine 6 3 1. 3 2 1.0% henyl alpha naphthy amine 8 2 30 .5% diphenylamine 5. 5 21.9 30 .75% alpha naphthylamine 1. 1 5 55 .5% ditertiary butyl cresol 1. 1 3 55 .5% 2,4-dimethyl 6-terti- I ary butyl phenol l3. 8 2. 4

It will be noted from the above table that the crank-case drainingsfrom the Caterpillar engine containing diphenylamine or 2,4-dim'ethyl tertiary butyl phenol had already become corrosive. Both these oils had been altogether non-corrosive before running in the Diesel engines.

We claim as our invention:

l. Lubricating oil suitable for internal combustion engines containing dissolved from 25% to 5.0% of a sulfonate salt and an arylamine having anti-oxidant properties, in an amount between .25% to 2% and not less than one-sixth of the content of said salt, said sulfonate being oilsoluble, free of free acid and combining a petroleum sulfonic acid with a polyvalent metal which forms an oxide that is not readily converted to other oxides under conditions of crankcase lubrication. I r

2. The oil of claim 1 wherein the petroleum sulfcnic acid is an oil-soluble mahogany acid.

3. Lubricating oil suitable for internal combusoi said salt is basic. 7 7 7 7 V 5. The oil of claim 3 wherein said polyvalent metal is selected from the group consisting of Mg, Ca, Sr, Ba, Al and Zn- 6. The oil of claim 3 which is free from sulfate esters. I

7. The oil of claim 3 wherein the content of the suli'onate soap is from 375% to 2.5%.

8. The oil of claim 3 wherein the hydrocarbon sulfonic acid contains a substitution radical selected from the group consisting of hydroxvl, amino, ether, sulfide, hydrosulfide, disulfide and halogen radicals.

9. The oil of claim 3 wherein said amine is a diary! amine.

10; Lubricating oil suitable for internal combustion engines containing dissolved from 25% to 2.5% of a sulfonate salt and a ditertiary butyl cresol in an amount between .l% to 2% and not less than one-sixth of the content oi. said salt,

said sulfonate being'oil-soluble, free of free acid and combining ahydrocarbon sulfonlc acid with a polyvalent metal which forms an oxide that is not readily converted to other oxides under conditions of crank-case lubrication.

11. Lubricating oil suitable for internal combustion engines containing from .75% to 2.5% of oil-soluble calcium petroleum sulfonate free from free acid and from one-sixth of the content of said sulfonate to 2% of an alpha naphthylamine.

12. Lubricating oil suitable for internal combustion engines containing dissolved from 25% to 5.0% of a sulfonate salt and an arylamin having anti-oxidant properties, in an amount between .25% to 2% and not less than one-sixth oi the content of said salt and an amount not more than 10% of an extreme pressure compound containing an element selected from the group consisting of S, P and Cl, which element is attached so that it does not liberate corrosive compounds under normal lubricating conditions in internal combustion engines, said sulfonate being oil-=soluble, free of free acid and combining a hydrocarbon sulfonic acid with a polyvalent metal which forms an oxide that is not readily converted to other oxides under the conditions of crankcase lubrication.

ROLAND F. BERGSTROM. EARL EUGENE PHILLIPS.