US2400492A - Art of lubrication - Google Patents

Description

Patented May 21,1946

' ART OF LUBRICATION Willard L. Finley, Sparta, Ill., and James H..Kirk, Hammond, Ind., assignors to Sinclair Refining Company, New York, N. Y., a corporation of Maine No Drawing. Original application August 19,

1941, Serial No. 407,440. Divided and this application July 23, 1943, Serial No. 495,890

3 Claims.

from 4 to 6 carbon atoms and iso alkyl esters of.

salicylic acid of which the alkyl group contains from 6 to 18 carbon' atoms. In compounded lubricating oils containing these-mixed salts, the mixed salts are advantageously incorporated in amounts insufllcient materially to alter the normally liquid character of the petroleum lubricating oil base. This application is a division of our copending application Serial No. 407,440, filed August 19, 1941, upon which Patent No. 2,348,461 was granted May 9, 1944. The trend of development in internal combustion engines has imposed increasing burdens upon the oils used for their lubrication, particularly with rspect to the operating temperatures and pressures. Extreme requirements in both of these respects are represented by the Diesel type of engines and supercharged aircraft engines. The useful operating life of a lubricating oil, in such severe services, is determined in large measure by its thermal stability and by its physical capacity to continue iunctioning as a lubricant at the high temperatures and pressures encountered. The use of special alloy bearing metals, to permit the use of increased bearing pressures and consequently smaller bearing surfaces, adds to these burdens both in that such metals, in contact with the oil, frequently tend to accelerate degradation of the petroleum lubricating oil base and in that lubricating oils and lubricating oil compositions which have the requisite properties in other respects frequently tend to be corrosive with respect to such metals. One measure of thermal stability is resistance to oxidation. Oxidation promotes either the formation of sludge or the formation. of acids corrosive to bearing metals, or both. To have any real meaning, this measure of thermal stability must be-applied under conditions of service since, for example,-bearing metals may promote oxidation. In another aspect, thermal stability is determined not only by the extent of oxidation or decomposition but also by the character of the products of such decomposition or oxidation and by the extent salts ofand location, within the engine, of deposits of such products, sludge, coke andresinous varnishlike materials, for example.

In previous applications, Serial No. 368,992, filed December 7, 1940, and Serial No. 407,002, filed August 15, 1941, by Willard L. Finley, one of the co-applicants herein, the compounding of etroleum lubricating oils with calcium salts of alkyl esters of salicylic acid including the'normal alkyl esters andthe iso alkyl esters has been described. The addends described in those applications function as strong anti-oxidants effective to inhibit, over prolonged induction periods, the rate of oxygen absorption at elevated temperatures and thus to limit any corrosive tendencies of the lubricating oil compositions with respect to bearing metals, to render deposits of sludge and carbon within the engine soft and friable rather than hard and coherent, and to act as a solvent 0 for sludge formed and thus to disintegrate and remove any deposits of sludge'and carbon as an incident of normal engine operation.

' These valuable properties of the calcium salts of alkyl esters of salicylic acid, however, are

rapidly impaired or even destroyed by thepresence in the lubricating oil composition, under service conditions, of metallic soaps such as those formed by corrosion of bearing metals through reaction with acid oxidation products of the lubricating oil composition. The use of alkyl phenol sulfides, including polymers and polysulfides, as addends in the compounding of petroleum lubricants has been described. Such addends have little if any direct effect as anti-oxidants, and

85 they tend to accelerate sludge formation, but they do function to protect metals with respect to corrosion, to inhibit the solution of metals in the lubricating oil composition, to precipitate or otherwise to deactivate any dissolved metal and particularly to minimize the pro-oxidant eiiect of any dissolved metal. We have now combined the desirable functions of these two types of addends to secure new advantages from the combination and to avoid the disadvantages and limitations of either used alone.

We have found that such alkyl phenol sulfides and such alkyl esters of salicylic acid can be combined with lime to form mixed salts, the compositions of our invention, which are powerful anti-oxidants, which inhibit corrosion or solution of metals, which deactivate dissolved metals, which are powerful detergent-dispersion agents, which inhibit viscosity rise and which contribute tothe film strength of compounded petroleum lubricating oils in which they are incorporated.

. The octyl ester of salicylic acid, for example, may

be represented by the following formula:

The amyl phenol polysulfide, for example, may be represented by the following formula:

(IHI (illl ClsUu (351111 which may be' represented by the following formula:

4 oC lluC-aOOCO I Q O I I C5111 Ctllu The mixed salts illustrated by the foregoing type formulas are the compositions of our present ine vention. These mixed salts can be formed by reaction between the alkyl phenol sulfide and either the neutral or the basic calcium salt of the alkyl ester of salicylic acid. If the reaction is between the basic salt and the alkyl phenol sulfide, water is liberated; if the reaction is between the neutral salt and the alkyl phenol sullide, an alkyl ester is liberated. Or, these mixed salts can be formed directly by reacting lime with a mixture of the alkyl ester of salicylic acid and the alkyl phenol sulfide. The reaction is with advantage carried out in a solvent, and lubricating oil compatible with the compounded lubricating oil in which the mixed salt may ultimately be incorporated is an advantageous reaction medium. The reaction is with advantage carried out with a sufficient excess of the alkyl ester of salicylic acid so that the addend composition, and the petroleum lubricating oil composition in which it is incorporated, will include a proportion of the calcium salt of. the alkyl ester of salicylic acid somewhat larger than the proportion of the mixed calcium salt of the alkyl phenol sulfide and the alkyl ester of salicylic acid. The excess of the calcium salt of the alkyl ester of salicylic acid maybe in the form of the neutral salt or a mixture ofthe neutral and basic salts. The reaction is with advantage carried out at a temperature below that at which substantial conversion of the compound in which the calcium replaces phenolic hydrogen to compound in which the calcium replaces carboxylic hydrogenor alkyl groups takes place. At maximum temperatures of about 280 F. this conversion is negligible but at temperatures upwards of about 300 F. it proceeds with increasing rapidity. Thetotal proportion of calcium salts of the alkyl esters of salicylic acid in a compounded lubricating oil containing the compositions of our invention may approximate, with advantage, from about 1% to about 5% .by weight on the compounded lubrieating oil, and of this the mixed calcium salts of the alkyl esters of salicylic acid and the alkyl phenol sulfides may, with advantage, approximate a proportion equivalent to from about 0.2% to about 0.5% of the alkyl phenol sulfide.

While the mixed calcium salts of our invention can be prepared as a separate product, for example, in solvents such as benzene or toluene or petroleum hydrocarbons, we have found it advantageous to produce these compositions by reaction in the petroleum lubricating oil base of the compounded lubricating oil in which it is to be incorporated. For example, we add 1%, 2%, 3% or somewhat more of the neutral calcium salt of the alkyl ester of salicylic acid, or of a mixture of the neutral and basic calcium salt of the alkyl ester of salicylic acid, to the petroleum lubricating oil base, or a portion of it, then add from about 0.2% to about 0.5% of the alkyl phenol sulfide to this mixture and then dehydrate the composite at a temperature not exceeding about 280 F. under a vacuum if necessary. Or, for example, we add the equivalent proportions of the alkyl ester of salicylic acid and of the alkyl phenol sulfide and the reacting proportion, or somewhat more, of lime as calcium hydroxide to the petroleum lubricating oil base, or a portion of it. and then dehydrate the composite in the same manner. The following compounded lubricating oils containing the composition of our invention as addends will illustrate the application of the invention:

I II III Gravity, API 18.4 26.8 27.0 Flash, "F 420 430 430 Fire, F 480 490 490 Viscosity at F 1666 565.4 600. 2 Viscosity at 210 F 80. 9 07. 7 39. 5 Viscosity indcx... 09. 3 09. l lour, "F 0 5 0 Carbon residue (ash-free), percent..." .00 1.19 1.26 sh 0.67 0.59 0. 61 Color NPA 7(4} 5) 7(4}) In the foregoing compounded lubricating oils, the addends embodying the compositions of our invention consisted of the reaction product .of a mixture of the neutral and basic calcium salts of the iso octyl ester of salicylic acid in which the basic salt comprised from about one-fifth to about one-half of the mixture and tertiary amyl phenol sulfide in polymerized form and containing polysulfide sulfur. In Example I, the reaction product of 4% of the calcium salt of the iso octyl ester of salicylic acid and 0.25% of the tertiary amyl phenol sulfide wasincorporated in a pale oil blend derived from a South Texas crude. Examples 11 and III were a Pennsylvania motor oil (SAE 30) containing the reaction products, respectively, of 4% 0f the calcium salt and 0.5% of the sulfide and 4% of the calcium salt and 0.25% of the sulfide. All of the compounded lubricating oils of the foregoing examples were basic in reaction.

compounded as just described, lubricating oil compositions, after addition of 0.01% FezOa as ing from nothing up to 0.005 gram under test conditions (the "Underwood oxidation test") such that the loss from the same lubricating oil base, without the addends but with the addition of the same proportion of the same pro-oxidant. ranged from 1.454 grams to 1.894 grams with cadmium silver bearing metal. Similar comparisons, based on identical tests, have shown that our improved results are not secured with either the calcium salt of the alkyl ester of salicylic acid 01' the alkyl phenol sulfide used alone, uncombined. Petroleum lubricating compositions containing the mixed calcium salts of our invention also exhibit a marked increase in sludging time as indicated by the Indiana oxidation test." For-example, with a petroleum 011 base such'as that of Example I,

the sludging timewas increased from 22.5 hours to 35 hours by incorporating the reaction products of 1% of the calcium salt and 0.5% of the sulfide and to 60 hours by incorporating the reaction products of 3.5% of the calcium salt and 0.5% of the sulfide. Similarly, with a petroleum oil base such as that of Example 11 and III, the

sludging time was increased from 200 hours to I 365 hours by incorporating the reaction products illustrated by the following tabulated results of identical comparative tests (the "Underwood oxidation test) applied to Sample A, an uncompounded oil of the type used in the previous Example I, and to Sample 13, the same base oil containing the reaction products of 3.5% of the calcium salt and 0.5% of the sulfide. To each sample 0.01% or FezOa as iron naphthenate was added as a pro-oxidant.

Sample A Sample B Oil tests before oxidation:

Carbon residue, percent 0. l2 1. 39 Vlscosi at 210 F 79 84 Neutral tion No. method A-.-" 0. M6 Alkaline Oil tests after 5 hours:

Carbon residue, percent l. 38 1. 41 Visooei at 210 F 103 86 Neutral etion No. method A-.-" 2.46 0. 20 Neutralization No. method B-.. 2. 76 0. Beeringrcorroei n Cd-Ag), fms" 0. 622 0. 001

A. 8. M. nap the inso uble,

fiercent l. 46 0. 02 C Ch insoluble, percent 4 0. 08 0. 01 Oil tests alter 10 hours:

Carbon residue, percent 2. 84 1. 51 Viscosit at 210 F 137 88 Neutral nation No. method A".-. 6.03 0.80 Neutralization No. method B..-.- 6.00 0. 85 Bearinfi corrosion (Cd-Ag), gms-- 1.464 0.001 A. S. M. naphtha insoluble,

eroent 3. 52 0. 08 C Ch insoluble, percent 0.09 0. (I) l The high solvent, or detergent-dispersion, capacity of the compositions of our invention when incorporated in a compounded petroleum lubrieating oil, moreover, imparts to the lubricating oil' a marked capacity to suppress ring sticking and excessive piston deposits and consequently to minimize ring and cylinder wall wear and to reduce any tendency toward scufllng of'pistons,

in the presence of the bearing metals under severe,

mixed calcium salts of the present invention in compounded lubricating oils, with respect to diminished carbon or like deposits within the cylinders of internal combustion engines and bearing corrosion losses, are illustrated by the .following tabulated results of comparative tests (Bus engine sludging test) wherein the oil is subjected to conditions closely approximating those encountered in actual use. The apparatus used in these tests consists of a metal box or sump adapted to hold a pool of oil which is heated by an oil bath in which the box is suspended. The box is provided with a cover heated by a lead bath. A rotary paddle wheel is supported within the box so that inrotating the blades thereof dip into the oil pool and throw the oil onto the sides and cover of the box and also onto an alloy bearing sus-- pended in the box abovethe surface of the pool of oil. The cover and upper portion of the sides of the box are partially shielded from the oil thrown from the paddle wheel by a screen of 30- mesh iron screen wire.

In carrying outthis test, the temperature of the oil in the sump is maintained at 250 F., and the temperature of the lead bath is maintained at500 F. The paddle wheel is rotated at 750 R. P. M. and air i blown through the chamber at a rate of 1 cubic foot per minute. The test is divided into 2 periods of 150 hours each. In

' starting the test, 2 liters of oil are placed in the sump. At the end of the first period, the oil is drained from the sump and new oil added together with 10% of the oil used in the first period of the test. At the end of each period the amount of corrosion of the bearing was determined by the Sample 0 Sample D Condition at end 01300 hour test:

Deposit on cover, 65.9----'. 0.4.

was.

Appearance oicover. Covered with coke.. Essential! clear.

Condition of sump-. Walls varnished.. o v

Condition atoll--." Bright and viscous" Bright and not vis- Beeringlose mga: I

15o hour's... no 10.

300 hours- 67 13.

The stability of a petroleum lubricating oil as represented by the oxygen absorption test is great- 1y improved by the incorporation in the oil of the mixed salts of the present invention. This i illustrated by the following tabulations of comparative results in which Sample E is an uncompounded Pennsylvania motor oil (SAE 30) of the type used in Examples 11 and III and Sample F is the same oil having compounded therewith the reaction products of, 1% of the calcium salt and 0.25% of the sulfide. The results of the tests are reported in terms of number or minutes required for the absorption oi" the indicated cubic centimeters of oxygen at normal temperature, and pressure per grams of oil. Eachsample was tested in the presence of copper-lead alloy bearing and under comparable conditions.

0. c. of oxygen/100 grams of oil Sample E Sample F Min. Mim

ing oil, consisting of a pale oil blend derived from a South Texas crude, containing the reaction.

products of 4% of the calcium salt and 0.25% of the sulfide, has satisfactorily lubricated the Diesel engine of a large streamline locomotive for a distance upwardsof- 65,000 miles without change of crankcase oil.

We claim:

1. The mixed calcium salts of alkvl phenol sulfides of which the alkyl groups contain from four to six carbon atoms and alkyl esters of salicylic acid of which the alkyl groups contain from six I to eighteen carbon atoms.

2. The mixed calcium salts of tertiar alkyl phenol sulfides of which the alkyl groups contain from four to six carbon atoms and iso alkyl esters of salicylic acid of which the alkyl groups contain from six to eighteen carbon atoms.

3. A mixed calcium salt of tertiary amyl phenol sulfide and iso-octyl ester of salicylic acid.