US2350489A - Lubricating oil composition - Google Patents

Description

June 6, 1944. L. E. BEARE LUBRICATING OIL COMPOSITION Filed April 5, 1941 7 Sheets-Sheet 1 0 7. ow, 0 Z w WJ/ ,O .I W bwgg/f W n 6 1w 0 4 NQ AAAQS/ w 0 m m m m m W 0 ATTORNEYS June 6, 1944. L. E. BEARE LUBRICATING OIL COMPOSITION "r Sheets-Sheet 2 Filed April is, 1941 hw mb be sh sum! Liz W 242 $0; ogre/1 0 fiqzwag INVENTOR leeward f. Beare BY PW WmWMRm'VEJHW ATTORNEYS Jun 1944 E. BEARE 2,350,489

LUBRICATING OIL COMPOSITION I INVENTOR 22 7 e e) 4 9 160w; 558w June 6, 1944. L. E. BEARE 2,350,489

LUBRICATING' OIL COMPOSITION Filed April 5, 1941 7 Sheets-Sheet 4 fimfimfmm ATTORNEYS June 6, 1944. E. BEARE LUBRICATING OIL COMPOSITION Filed April 5, 1941 '7 Sheets-Sheet 5 WQR m MXQ ATTORNEYS June 6, 1944.

L. BEARE LUBRICATING OIL COMPOSITION 7 Sheets-Sheet 6 Filed April 5, 1941 sure/ :42 rm aqzbaaqj izqzwag '///V 7 l e onard 5 Bears ATTORNEYS June 6, 1944. 1.. E. BEARE LUBRICATING OIL COMPOSITION '7 Sheets-Sheet 7 Filed April 5, 1941 INVENTOR Zeonoraffiwe ATTORNEYS @umin,

Patented June 6, 1944 I UNITED STATES PATENT OFFICE LUBBICATING OIL COMPOSITION Application April 5, 1941, Serial No. 387,014

12 Claims.

- Thisinventlon relates t improvements in lubricating oil compositions. It relates more particularly to compounded petroleum lubricating oils containing one or more addition agents which impart corrosiveness to the compounded oils but wherein the corrosiveness of the compounded oil is substantially inhibited by the addition thereto of relatively small proportions of alizarin or of the fatty acid stars of alizarin or mixtures thereof.

The trend of. development in modern machinery, notably in Diesel and other internal combustion engines. has imposed increasing burdens on the oil used-for their lubrication, particularly with respect to operating temperatures and pressures. The useful operating lifeof a lubricating oil in such service is determined in large measure by its thermal stability and by its physical capacity to continue functioning as a lubricant at the high temperatures and pressures encountered.

One of the measures of thermal stability is resistance to oxidation and a consequent tendency to form sludge but in another aspect the effect of thermal instability is determined not only by the extent of oxidation or decomposition but also by the character of the products of such decomposition and oxidation and by the extent and location within the engine or the like of the deposits of such products.

In the Diesel type of engine, for example, the high temperature to which the lubricating oil is subjected, particularly at the top of the stroke, frequently causes deposition of sludge and carbon in the groove before and behind one or more of the piston rings. consequent sticking of the rings rapidly deprives the engine and cylinder wall of proper lubrication, inducing excessive wear and frequently scoring of the cylinder wall. For satisfactory lubrication, it is essential that this condition be avoided.

Another essential characteristic of lubricatin oil to be used under severe conditions is the ability to maintain a satisfactory lubricating film between the bearing surfaces at the high temperatures and pressures encountered. This property of the lubricant is usually characterized as film strength.

The operating conditions in certain types of machinery are so severe that the natural characteristics of petroleum lubricating oils have been found inadequate for the satisfactory lubrication of these machines over extended periods. In such instances it has been necessary to supplement or alter the natural characteristics of the lubricating oil by the addition of one or more agents, commonly referred to as addition agents.

Various metal soaps, notably soaps of aromatic stearlc acids such as phenyl stearic acid or mixtures comprising such soaps. have been found to be particularly effective addition agents.

. For instance, the remarkable advantages derived from the. addition of relatively small amounts of certain metal phenyl stearates or mixtures of such phenyl stearates with phenyl stearic acid or stearlc acid or metal stearates to petroleum lubricating oils have been related in United States Letters Patent No. 2,081,075, 2,095,538 and 2,180,- 697 to Arnold C. Vobach.

Lubricating oils compounded with such material, as described in said patents have a high solvent capacity for sludge of a character formed by oxidation or decomposition of petroleum lubricating oils and render deposits of sludge and carbon within the engine soft and friable rather than 16 hard and coherent and appear to disintegrate and remove such deposits as are formed so that the formation on the piston of carbon deposits hard enough and coherent enough to involve sticking of the rings is materially retarded, if not avoided. 20 However. lubricating oil compositions containme such addition agents have been found to be decidedly corrosive toward some of the alloy bearings, notably copper-lead and cadmium-silver alloy bearings, commonly used in internal combustion engines.

I have discovered that the corrosive action of such lubricating oil compositions is substantially inhibited by the addition thereto of relatively small proportions of alizarin or the fatty acid esters of alizarin; for example, alizarin stearates, such as alizarin monostearate and alizarin distearate.

Not only are the bearings or the like protected from destructive corrosion, in accordance with my invention, but other desirable characteristics of the lubricating oil compound are materially improved, as will appear from the following detailed description thereof.

As previously noted, certain metal phenyl stearates and mixtures thereof have proven to be very effective addition agents in lubricating oils. The advantages derived from the use of and the method of preparing calcium phenyl stearate or mixtures of calcium phenyl stearate and unsaponified 45 phenyl stearic acid or calcium stearate or both and the method of compounding these addition agents in lubricating oils are fully described in the previously referred to Patent No. 2,081,075.

Also, in the above-referred-to Patent No. 2,095,- 59 538, there are described the advantages derived from the use of and the method of preparing and compounding with lubricating oils, calcium phenyl stearate or mixtures of calcium phenyl stearate and calcium stearate modified by the inclusion 55 of the equivalent of 7-20% stearlc or palmitic acid or mixtures thereof.

A further advantageous type of calcium phenyl stearate addition agent is one containing an amount of calcium greater than that correspond- 60 ing to the neutral soap. It may be prepared, for

of the type referred to above.

example, by neutralizing phenyl stearic acid with such an excess of lime as results in the production ofga soap mixture consisting of one part of basic calcium phenyl stearate to four parts of neutral calcium phenyl stearate. This mixture of neutral and basic soap is herein designated basic calcium phenylstearatefl 1 The calcium phenyl stearate addition agen wherein the phenyl stearic acid or mixture of phenyl stearic acid and fatty acid are completely neutralized, no excess of lime over that corresponding to the neutral soap being present, is herein designated neutral calcium phenyl stearate. That in which the phenyl stearic acid or mixture of phenyl stearic acid and fatty acid are not completely neutralizedbut contain an equivalent of 7-20% excess phenyl stearic acid or palmitic or stearic acid are herein designated acidcalcium phenyi stearate.

. References herein to phenyl stearic acid or to calcium phenyl 'stearate are to be interpreted as meaning the material or materials so designated in the above-referred-to'patents to Vobach. 4'

Each of these calcium phenyl stearate addition agents, i. e. acid, neutral and basic, has been found to be very effective with respect to carbon deposition, as above noted. However, lubricating oil compounded with eitherhas a decided In accordance withmy present invention, the corrosive action of such lubricating oil compounds is substantially retarded or even eliminated without destroying the desirable characteristics imparted to the compound by the corrosion-inducing addition agents. This is accomplished by in-.

corporating in the lubricating oil composition relatively small proportions of one or more of the previously named corrosion-inhibiting compounds. Alizarin is relatively insoluble in a mineral oil at normal temperatures, its solubility under such stearate compounds, respectively, both with. and.

conditions ranging from about .02% in highly parailinic oil to about .05% in naphthenic oils.

Alizarin stearates are more soluble and for this reason their use is in some cases preferable to .alizarin. However, other conditions may influence the choice of one over the other as the characteristics of the resulting lubricating pounds difler in some respects.

e The alizarin under some conditions appears to be more effective than the alizarin stearatesin inhibiting corrosion but in the presence of calcioil comum phenyl stearates there is a tendency for the alizarin to precipitate out of the oil, probably as calcium 'ali za'rate. .Alizarin stearates are more stable under such'conditions.

Also, alizarin 'stearates appear to have the-add.- ed'function of an anti-oxidant in calcium phenyl stearate' lubricating oil compounds. However,

they do not appear to have this function in imcompounded 0115, though alizarin does Further, though alizarin definitely inhibits corrosion in assess-c appear to function as an anti oxidant such compound.

The invention will be runner (released by spe- 'cinc illustration of applications of the principles thereof and of. the beneficial results soobtained.

The elect-of the addition of alizarin stearate to acid and basic calcium phenyl stearate-lubrieating oil compounds is illustrated by the following Tables I and II inwhich are recorded the results ottests of acid and basic calcium phenyl without the addition of alizarin stearate. The mineral oil constituent of each such compound testedwasasouth'l'exaspaleoil (fromaGuif Coast crude) having a viscosity of about 500 seconds at 100 F. Baybolt Universal and boiling 10% up to 700* F. and up to 900 F. approxi-v mately.

As to each sample referred to in Table I, 1.33%

of acid calcium phenyl stearate was compounded with the mineraloil and as to each of those reterred to in Table II, 1.38% of basic calcium phenyl stearate was compounded with the mineral oil. Alizarin monostearate .was included in these'compounds in the proportions indicated.

Table] SampleNc.

"percent" None 0.75 0 oxygen as grams 0 compounded oil..." 435..-"; -.-.co.- 3.502 2'! Bearing metal loss, coppeolead -.-..--milligrams 23. 8 3.0

new 11,

BamplcNo. 5

sum-m monostearate.-.per cent None 0J0 0.2) 0.75 Total oxygen abmrbed Res gramsoi'oom edo --.cc.. 2,560 1,350 12 87 Bearlngmetal Osacoppenhad;

' milligrams" 26.5 15.6 6.0 2.0

The amount of oxygen absorption recorded in the above tables is at normal temperature and pressure and was determined by the true oxidation test-the bearing metal, in this case copperlead alloy, being present in the oil during the test. The test was in each case conducted at .a temperature of 300 F, and the duration of the test was minutes. The bearing metal losses shown in the above tables were determined from the weight of the pieces of bearing metal present in the true oxidation test ,before and. after the test.

The. alizarin monostearate used in ccmpounriing these samples was prepared. by refluxing 5 parts of dry powdered alizarin in 50 parts of toluene and adding 6 -parts of' steai'yl' chloride drop by drop over a period of ten hours. The extremely slow addition of the latter was an extra precaution against the possible formation of alizarin distearate,'but is not believed to be The alizarin went completely into solution soon after all of the stearyl chloride had been added. This was assumed to indicate the substantial completion of the reaction as only a small fraction of alizarin issoluble in the toluene. The mixture was refluxed for an additional ten hours phenyl stearate compounds, itdoes not 75 88 8 p 'fi flllfi n gainst any 1 mm l mflinillg imdissolved and the toluene then distilled off to the point at which foaming occurred. The product was then air-dried at 150-200 F. until free from any odor of toluene. The yield was 104 parts of alizarin stearate which is substantially the theoretical yield.

The alizari stearate product was a brown, brittle waxy solid, melting at about 150-160" F. Its analysis showed a trace of chlorine (0.08%) and a small amount of sulfur (0.12%).

The effect of the presence oi. varying proportions of alizarin monostearate on the rate of oxygen absorption by the calcium phenyl stearate compounded oils, Samples 1 to 6, inclusive, under the above-described conditions, is graphically illustrated by Figure I of the. drawings in which the amount of oxygen absorbed in cubic centi meters, measured at normal temperature and pressure conditions, per hundred grams of the compounded oil, is plotted against time expressed in minutes. From this chart it will be observed that the addition of 0.1% of alizarin monostearate to the basic calcium phenyl stearate compounded oil considerably prolonged the period within which oxygen absorption was relatively inactive. In other words, it substantially inhibited oxidation for a considerable period of time. For example, within the first hour of the test, less than 100 cubic centimeters of oxygen were absorbed. The addition of larger proportions of alizarin stearate still further increased the period of relative inactivity, 0.2% being even more effective than 0.75%. Such period of relative inactivity oi the compounded lubricating oil, with respect to oxidation or corrosion, is herein referred to as the induction period.

The effect of the addition of alizarin monostearate to calcium phenyl stearate compounded oils is further illustrated by Table III wherein there is tabulated data concerning tests in which varying proportions of the alizarin stearate were added to acid calcium phenyl stearate compounded oils of the type and composition previously described.

Table III Sample No.

Calcium phenyl stearate.. ...per cent. 1.33 1.33 1.33 Alizarin mouostearate do None 0. 75 0. Indiana sludging time... hours 27 25 26 lj, A. S. '1. M.-naphtha insoluble .(io. 43 0 42 lsoosity at 210 F.cud of 50 hours 79 70 73 Viscosity rise at 210 F. in 50 hours 22.1 14. 3 1 17 100 milligram induction period:

Copper-lead alloy. ...hours 1 14.5 Cadmium-silver alloy -.do... .5 25

1 Approximate.

The Indiana sludging time noted in Table III and elsewhere herein is expressed in terms of the time required to form milligrams of sludge per 10 grams of material tested in a glass cantainer at 341 F. by the Indiana oxidation test described in the Society of Automotive Engineers Journal 34, page 173 (1934). The 1% A. S. T. M. naphtha insoluble figure is the time required to produce, under the same conditions, 1% of material which is insoluble in A. S. T. M. naphtha. The viscosity figures are in seconds Saybolt Universal and were taken after a period of treatment by the said Indiana oxidation test.

The 100 milligram induction period is the t'me required for a loss of 100 milligrams in weight oi the particular alloy bearing in contact with the compounded lubricating oil maintained at 250 1". as determined by the Chrysler bearing corrosive test-machine.

Similar data, but with respect to neutral calcium phenyl stearate compounded oils containing different proportions of neutral calcium phenyl stearate and alizarin monostearate. is presented in Table IV:

Table IV Sample No.

Calcium phenyl stearate; per cent. 1.31 1.33 0.67 Alizarln monostearate i do None 0. 76 0.5 Indiana sluding time.... hours 30 24 15 1% A. B. '1. M.naphtha insoluble.. do 44 65 40 Viscosity at 210 F.end of hours.. 74 72 Visooslt rlseat 210 F. in50hours....... 13.7 11.6 mill gram induction period:

Copper-lead alloy hours 3.5 42.0 35.5

Cadmium-silver alloy. do .5 62.0 39.5

Data corresponding to that presented in the foregoing tables, but with respect to basic cal- Table V Sample N 0 l3 14 15 i 16 l 17 18 Calcium phenyl stearate l percent. 1.33 1.33 1.33 0.67 1.0 2.0 Allzarin monostearate per cent .Noue 0.75 0.5 0.5 0.68 0.68 Indiana sludging time hours 36.5 30.0 32.5 0.0 25.0 40.0 1% A. S. T. M. naphtha ins0l uble hours 49.0 47.0 45.0 39.0 60.0 60.0 Viscosity at 210 F.eud

oi50h0urs... 73.8 60.0 71.01680 05.0 65.0 Viscosity rise at 210 F. in l I -50h0l1l'S........ 17.0 13.2 17.7 15.0 11.0 11.0 100 milligram induction period:

Copper-lead alloy hours. 4.0 30.5 24.5 31.5 I 51.0 20.0 Cadmium-silver alloy hours. 0.5 41.5 365,510 31.0

Thus, it appears that by the inclusion of various proportions of alizarin stearate in calcium phenyl stearate lubricat'ng oil compositions, comprising either acid, neutral or basic calcium phenyl stearate, the induction period, i. e. the time required for the initial loss of 100 milligrams of bearing metal by corrosion, is markedly increased without in most instances greatly affecting detrimentally the sludging characteristics of the compounded oil.

In each instance the Indiana sludging time was somewhat reduced and in some cases the 1% naphtha insoluble time was slightly reduced while in others, notably Samples 11. 17 and 18, the latter was materially increased. However, in every instance, except Sample 15, there was a decided reduction in viscosity rise during the 50 hour test period.

Corrosion is also inhibited by the addition of alizarin to the calcium phenyl stearate compounded oils. Where 0.2% alizarin was compounded with a basic calcium phenyl stearate compounded oil, such as described above, comprising 1.33% basic calcium phenyl stearate, the 100 milligram induction period with copper-lead I greater than 0.75%

bearings was increased to 11 hours and, with cadmium-silver, was increased to 30 hours. Alizariml as previously noted, is only slightly soluble in uncompounded naphthenic base oil. However, it is soluble to the extent of about .2% in these compounded oils containing 1.33% calcium phenyl stearate, though it is relatively less stable therein than is alizarin stearate and has a tendency to form a precipitate at temperatures in the range from 250 to 350 F.

The advantages with respect to inhibition of bearing corrosion derived from the incorporation of relatively small proportions of alizarin stearate in calcium phenyl stearate lubricating oil compounds is graphically illustrated by Figs. II to IV, inclusive, of the drawings whereon bearing corrosion loss in milligrams, as determined by the Chrysler bearing corrosion test machine, is

plotted against time in hours. These tests were conducted at 2540 R. P. M., 250 F. oil feed temperature and 2700 pounds load.

on Fig. II is shown the rate of bearing corrosion losses of copper-lead and cadmium-silver alloy bearings when using acid, basic and neutral calcium phenyl stearate compounded oils, respectively, and the decided decrease in corrosion rate in each where alizarin stearate' is incorporated in the compounded oil. It will be observed that the induction period was in each instance materially prolonged by the addition of alizarin monostearate to the lubricating oil composition.

The corrosion-inhibition obtained by the incorporation of various proportions of alizarin stearate or alizarin in basic calcium phenyl stearate compounded oils containing 1.33% basic calcium phenyl stearate is shown on Fig. 111 of the drawings. The effect of varying the proportions of calcium phenyl stearate and alizarin monostearate in the basic calcium phenyl stearate compound is similarly shown on Fig. IV of the drawings.

It was observed that at relative concentrations 7 alizarin monostearate to 1.33% calcium phenyl stearate a dark red precipitate started to form at temperatures above 450 F. but that below this ratio no precipitate compound to which 0.75% alizarin monostearate was added showed no perceptible bearing corrosion loss. Samples 14 and 16 above, when subjected to this test under more severe conditions (the hot box test), showed, respectively, 190 and 50 milligrams bearing corrosion loss. Comparable piston conditions with respect to'carbon deposition atthe end of the test were obtained in each case.

It is sometimes desirable to include in the lubricating oil compound of my invention relatively 'ployed is generally in the range or approximately 0.5 to 1.0% by weight.

I have discovered that alizarin distearate is generally more stable in lubricating oil compounds containing calciumsoaps than is alizarin or the mondstearate of alizarin. The distearate appears to equal the monostearate in corrosioninhibitin power but has the advantage over the monostearate that there is a higher critical ra@ 1:10 of the distearate to calcium phenyl stearate permissible before precipitation occurs on heating. Similarly, alizarin alone, in concentrations up to 0.2% in'a lubricating oil compounded with basic calcium phenyl stearate, does not cause a precipitate to form on heating. However, on

heating a calcium phenyl stearate compounded oil containing both alizarin and alizarin distearate, a. slight precipitate may occur.

Illustrations of specific proportions of calcium phenyl stearate, lauryl alcohol and alizarin or alizarin stearates which have been found to-give particularly advantageous results when compounded with the previously described lubricating oil-appear in the following Table VI in which. Sample No. 21, which contains no alizarin or alizarin stearate, is included for comparison:

Table VI Sample No.

Calcium phenylstearate percent.. 1.33 0.67 1.33 0. 67 1.33 1.33 Lauryl alcohol. do 1.0 None 0.5 0.5 1.0 1.0 Alizarln monostearate t 0 75 0 N N per cen .5 one 0.375 one None Alizarin distearate do' None None None None 0.75 None Aliqann do.--. None None None None None 0.2 Indiana sludgmg time hours 28 15 36.5 26 1% A. S. T. M. naphtha insoluble h 5-. 40 49 39 Viscosity at 210 F-end 50 ours 72 73.8 69 Viscosity rise at 210 F. in

50hours 17.3 17.6 17.6 14.2 100 milligram induction period:

Copper-lead allo ours-- 45 56+ 4 36 11 Cadmium-silver alloy hours 7 56-]- 0.5 41.5 3015 In compounding the above-referred-to samples designated No. 19 and No. 20, the neutral calcium phenyl stearate was used while Samples Nos. 21 to 24, inclusive, were compounded with basic calcium phenyl stearate.

The corrosive characteristics of various compounds included in Table VI, determined as in the tests previously described, are graphically illustrated on Figs. V and VI of the drawings with respect to copper-lead and cadmium-silver alloy 7 bearings, respectivelyincluding for ready com- ,parison the curve for Sample 8 previously'idenarin distearate increases the tendency to form a precipitate over that present when the distearate small proportions of a solubilizer such as lauryl alcohol. The lauryl alcohol has a stabilizing iniiuence on mineral oil compounds comprising calis used alone, this tendency is not particularly objectionable in most cases. Further, the presence of alizarin appears to have an activating eiTect upon the alizarin distearate-which increases the corrosion-inhibiting ability of the distearate. For example, a compounded oil consisting oi 1.33% basic calcium phenyl stearate, 1% lauryl alcohol and 1% alizarin distearate in the above mentioned South Texas pale oil, when subjected to the hot box test in a standard one-cylinder Diesel Caterpillar test engine, resulted in a copper-lead alloy bearing corrosion loss of 105 milligrams. In a similar compounded oil wherein the alizarin distearate proportion was reduced to 0.75% and 0.1% of alizarin added. the copp lead alloy bearing corrosion loss was only 50 milligrams. In both cases the piston and ring condition was excellent with respect to carbon deposition. However, when the proportion of alizarin distearate in this compound was reduced to only 0.5%. the bearingcorrosion loss increased decidediy.

In the regular Caterpillar one-cylinder engine test, the copper-lead alloy hearing corrosion losses, using the alizarinfree Samples No. 7 and No. 13, were, respectively, 11,900 milligrams and 2860 milligrams while that for Sample No. 8. which contained alizarin monostearate. was 420 milligrams. In the more severe hot-box Caterpillar engine test, these losses for compounded oils containing alizarin or alizarin stearate were as follows:

70 milligrams for Sample No. 19 40 milligrams for Sample No. 20 I 65 milligrams for Sample No. 22 170 milligrams for Sample No. 23 100 milligrams for Sample No. 24

For the purpose of more clearly illustrating the advantages derived from my invention, the base lubricating oil used in the foregoing specific examples has in each case been a South Texas pale oil such as previously identified. However, it will be understood that my invention is not limited to a particular lubricating oil but is applicable to lubricating oils generally.

For example, a mixture of 62.5% phenolsolvent-treated neutral oil and 37.5% slightly solvent-treated bright stock from a Pennsylvania crude compounded with 1.33% neutral calcium phenyl stearate, 0.75% alizarin distearate and 0.1% alizarin caused a copper-lead alloy bearing corrosion loss in the above-mentioned hot box Caterpillar en e test of only 60 milligrams. Its Indiana sludging time was 108 hours; its 1% A. S. T. M. naphtha insoluble was 127 hours; and its viscosity rise at 210 F. for 50 hours and 100 hours was, respectively, 4.9 and 24.7 seconds. Similarly a mixture of 75% of the previously mentioned Texas pale oil and 25% of an acidtreated high sulfur lubricating oil fraction compounded with 1.33% basic calcium phenyl stearate, 1.0% lauryl alcohol, 0.75% alizarin dlstearate and 0.1% alizarin, when tested on a four cylinder Caterpillar test engine (hot box test) resulted in an average copper-lead alloy bearing corrosion loss of only 43 milligrams. In this test, the piston skirt was clean. the rings were free and there was only a very light carbon deposit in the top groove. Its 100 milligram induction period with copper-lead alloy .bearings was 40 hours. 7

Nor is the utility of my invention limited to calcium phenyl stearate lubricating oil compounds. I have found it of decided advantage where the calcium phenyl stearate is supplemented by still further addition agents and also where the calcium phenyl stearate is replaced by other corrosion-inducing addition agents. For

. example, decidedly beneficial results have been obtained by compounding with the previously referred to South Texas pale oil 1.33% basic calalloy hearings of 47 hours. On a four-cylinder Caterpillar test engine (hot box test) the average copper-lead alloy bearing corrosion loss was 117 milligrams and the piston condition with respect to carbon deposit was good.

similarly, a compound consisting of South Texas pale oil, 4% of a solution in mineral oil of the calcium soap of oxidized mineral oil about equal in calcium content to 1.33% of calcium phenyl stearate, 0.75% alizarin distearate, 0.1% alizarin and 2% sulfurized sperm oil was found to have a 100 milligram copper-lead alloy bearing induction period in excess of 51 hours. In a four-cylinder Caterpillar test engine hot box test, '15 using this latter compound, the copper-lead alloy bearing corrosion loss was 55 milligrams and the piston condition with respect to carbon deposition was excellent.

I will further illustrate my invention with rem spect to lubricating oil compounds wherein aluminum phenyl stearate or phenyl stearic acid is substituted for the calcium phenyl stearate previously referred to. With aluminum phenyl stearate, the above-mentioned tendency for the formation of a precipitate under certain conditions is substantially reduced and a more stable composition under such conditions is obtained. The application of my invention with respect to the inhibition of oxidation and corrosion by the addition of alizarin to aluminum phenyl stearate or free phenyl stearic acid lubricating oil compounds is illustrated by the following Table VII. In the compounded oils illustrated, the lubricating oil constituent was the previously mentioned South Texas pale oil. Tests of samples containing no alizarin are included for comparison:

Also, a compounded oil consisting of the South Texas pale oil with 1% aluminum phenyl stearate and 0.5% alizarin showed no appreciable signs of corrosion of copper-lead alloy bearings by the Chrysler bearing corrosion test.

Though alizarin is only slightly soluble in lubricating oil at room temperatures, it was in complete solution at the temperatures of these tests.

Lubricating oil compounds containing aluminum phenyl stearate or phenyl stearic acid are normally decidedly corrosive but, as appears from the above-tabulated results, the inclusion of very small proportions of alizarin materially inhibits corrosion. It appears that the alizarin acts as a true corrosion-inhibitor in such compounded oils. However, alizarin does not appear to act as an anti-oxidant in the compounds of Table VII as the oxidation rate was reduced by the addition of alizarin only to about that of the base oil without the bearing metal present. m instance, a

further test of the compounded oil containing 1.0% phenyl stearic acid but no alizarin showed a metal loss of 49.8. milligrams due'to corrosion and a total oxygen absorption of about'640 c. 0.

metal present. Also', Sample 81 above had a reduced oxidation rate during the first part of the test, but closely approximated that of the alizariniree compound during the latter part of the oxidation period.

. While'I do not predicate my invention upon any theory of the action of alizarin, it would appear that allzarin protects the metal from the corro- 'sive action of the addition agent. I have observed.

that metal which has previously been subjected to the action oi. compounded oils containing alisarin is much more resistant to corrosion than bearings which have not been so treated For example, the same copper-lead alloy bearing used:

in the above test of Sample 30 was subsequently tested with Sample 28 and the resulting. bearing corrosion loss was only 18 milligrams as compared with.49.8 milligrams loss of the bearing not so treated.

The corrosion-inhibiting power of alizarin with respect to normally corrosive compounded oils containing aluminum phenyl stearate. is graphically illustrated by Figure VII of the drawings as to copper-lead and cadmium-silver. alloy bear- .ings. The curves for the alizarin-jfree oils are also included for ready comparison. a 7

In addition to the advantages" derived from my invention with respect to corrosiomithe lubricating oil compound is frequently also improved with respect to its sludging and film-strength characteristica' Forinstance, the addition of 0.5% of alizarin monostearate to a compounded oil consisting of a highly refined steam-distilled double-solvent-treated residual oil from a Pennsylvania c'rude, having a viscosity of approximately 126 seconds .at 210 F. Saybolt Universal'and 1.25% of the methyl ester of a fatty acid produced by the oxidation of mineral oil, was found to improve materially the sludging characteristics,

of said compounded oil and substantially to decrease the viscosity rise of thecompounded oil when subjected to the Indiana sludging test.

The fllm strength of Sample 13, for instance, 7

'stearate.

was 418 pounds as determined by th Timken breakdown test. The addition oi 0.2% v aliz arin increased this breakdown. load to 22 pounds and the addition of 0.75% alizarin stearate, together with 0.2% alizarin. further increased the breakdown load to 24 pounds. Similarly, Sample 24 which contained 0.2% alizarin had a Timken breakdown load of 22 pounds as compared with 18 pounds for Samplelii. v 1

Iclaim: a

, 1. An improved lubricating oil compound com;

prising a petroleum lubricatingv oil, ametal soap of an aromatic fatty acid in an amount suilicient to impart corrosiveness to said lubricating oil com- I pound and a compound of the groupconsisting of prising a petroleum lubricating oil, phenyl stearic acid in an amount sufiicient to impart corrosiveness to said lubricating oil compound and a compound of the group consisting of alizarin and 1:5 fatty acid esters thereof in an amount suillcient as compared with 90 c. c. for the oil without the to inhibit said corrosiveness.

4. An improved lubricating oil compound comprising a petroleum lubricating oil, calcium phenyl stearate in an amount suficient to impart l corrosiveness to said lubricating oil compound and a compound of the group consisting of all:- arin and fatty acid esters thereof in an amount sumcl'ent to inhibit said corrosiveness.

5. An improved lubricating oil compound'com is prising a petroleum lubricating oil, calcium phenyi steal-ate in an amount sumcient to impart corrosiveness to said lubricating oil compound and a compound oi the group consisting of aiizarin. alizarin monostearate and alizarin distearate in an amount suficient to inhibit said corrosiveness.

6. An improved lubricating oil compound comprising a petroleum lubricating oil, aluminum phenyl stearate in an amount suflicient to impartborrosiveness to said lubricating oil compound and a compound of the group consisting :of alizarin, alizarin monostearate and aliz'arin diistearate in an amount suiiicient to inhibit said. corrosiveness. j Q

a I. An improved lubricating'oil compound comprising a petroleum lubricating 011. DherLvl stearic acid in an amount suflicient to impart'corrosiveness to said lubricating .oil compound and seem: pound of the group consisting of alizarin, alizarin monostearate and alizarin distearate inv an 5 amount suillcient to inhibit said corrosiveness.

8. An improved lubricating oil compound comprising a petroleum lubricating oil, calcium phenyl stearate in an amount suillcient to impart corrosiveness to said lubricating oil compound. a solu- 40 bilizer and a compound of the group consisting of alizarin, alizarin monostearate and alizarin distearate in an amount sufllcient to inhibit said corrosiveness.

9. An improved lubricating oil compound comis prising a. petroleum lubricating oil and an addition agent which imparts corrosiveness to said lubricatingo'il compound, the corrosiveness of the compounded oil beingsubstantially inhibited by the addition of an effective amount of 10. An improved lubricating oil compound comprising a petroleum lubricating oil andanaddition'agent which imparts corrosiveness to said lubricating oil compound. the corrosiveness of so the compounded oil being substantially inhibited by the addition of eflective amounts of ,aliza anda fatty acid ester of alizarin. i 11.'An improved lubricating compound comprising a petroleum lubricating oil, a metal soap go of an aromatic fatty acid in an amount suflicient to impart corrosiveness to said lubricating oil compound, the corrosiveness of the compounded oil being substantially inhibitedby the addition of an eifective' amount of an alizarin stearate.

.65 12. An improved lubricating oil compound comprising a petroleum lubricating oil, andaimetal soap of an aromatic fatty acid in an amount su'ill-' I cient to impart corrosiveness to said lubricating oil compound, the corrosiveness oi the com-'- pounded oil-being substantially inhibited births addition of effective amounts of alizarln anda fattyacidesterofalizarin.

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