US2347546A - Lubricating oil composition - Google Patents

Description

April 25, 1944. w. L.. FlNLl-:Y

LUBRICATING OIL COMPOSITON Filed Dec. 7, 1940 s Sheets-sheet 1 INVENTOR QQ $4 mk QS um@ uw @w ab S uw bm. \W\ SM w n SSM w/MfM ATTORNEYS April 25, 1944. w. L. FlNLl-:Y

LBRICATING OIL COMPOSITION Filed Dec. v"l, 1940 3 Sheets-Sheet 3 INVENTOR 'Y M W Y F. Mm R A Mm Patented Apr. 2s, 1944 UNITED STATES PATENT OFFICE 2,347,546 LUBRICATING OILV COMPOSITION Willard L. Finley, Chicago, Ill., assigner to Sinclair Benning Company, New York, N. Y., a.

corporation of Maine Application December 7,1940, Serial No. 368,992

6 Claims.

GOOR GOOR where R. is an alkyl chain of say 8 to 18 carbon atoms. They may be less accurately but more conveniently described as calcium alkyl salicylates. For convenience they will hereinafter be so described, it being understood that the term calcium octyl salicylate for example is intended to define the calcium salt of the octyl ester of salicylic acid.

The trend of development in internal combustion engines has imposed increasing burdens upon the oils used for their lubrication, particularly with respect to the operating temperatures and pressures. Extreme requirements in both of these respects are represented by the Diesel type of engine 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 functioning asa lubricant at the high temperatures and pressures encountered. One measure of thermal stability is resistance to oxidation, Oxidation promotes either the formation of sludge or the formation of acids corrosiveV to bearing metals, or both. However, in another aspect theeiiect of 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 and location, within the engine, of deposits of such products.

The improved lubricating oil compositions of my, invention have, in addition to the lubricating properties of the petroleum oils of which they are compounded, a high solvent capacity for sludge of the character formed by oxidation of petroleum lubricating oils, and, perhaps of even greater importance, the property of rendering soft and friable rather than hard and coherent and of disintegrating and removing such deposits as an incident of the normal operation of the engine. In engines 'of this type the high temperature to which lubricating oil is subjected, particularly at ,the top of the stroke, frequently causes deposition of sludge and carbonization in *the groove for and behind one or more of the piston rings. Consequent sticking of the rings rapidly deprives the piston and cylinder wall of proper lubrication inducing excessive wear and,

frequently, scoring of the cylinder wall.- The formation of such carbon deposits, hard enough and coherent enough to involve sticking of the rings is materially retarded, if not avoided, by the use of the improved lubricating oil compositions of my invention.

In the lubricating oil compositions of my in- 'vention the calcium alkyl salicylates function not only to inhibit sludge formation and to modify the character of the carbon" deposits, but they also function as strong anti-oxidants effective to inhibit, at least over a prolonged induction period, the rate of oxygen absorption at elevated temperatures, thus rendering such lubricating oil compositions non-corrosive, or less corrosive, to alloy bearing metals.

The calcium salts of the alkyl esters of salicylic acid may advantageously be prepared by rst esterifying salicylic acid with the appropriate alcohol, using concentrated sulphuric acid as the catalyst, then replacing the hydrogen of the hydroxyl group by a metal such as sodium by reaction with sodium hydroxide, and nally reacting the resulting product with calcium chloride to form the calcium soap by double decomposition. The following example will serve to illustrate this method in the preparation of the calcium salt of the octyl ester of salicylic acid. 1380 grams (10 mols) of salicylic acid were placed in a 5 -1iter flask with 1820 grams (14 mols) of octyl alcohol. 10 ml. `of concentrated sulphuric acid and 300 ml. oftoluene were added. The flask was heated thereby distilling toluene and water up into a Areux condenser equipped with a trap the bottom of which was arranged to allow the condensed water to be drawn oi and the toluene returned continuously to the flask.

deposits of sludge and carbon within the engine u After four and one-half hours the theoretical yield of water grams) was collected and the heating stopped. The product was then washed successively with water and with a sodium bicarbonate solution. It was thereafter washed four more times with water until all of the sodium salts were removed. The water and toluene were still heated in an oil bath, three overhead fractions being obtained. 'Ihese cuts. the boiling range and pressure at which they were obtained. their acid numbers and their saponiiication numbers are given in the following table:

ggf Boiling range Weight Acid No. Sap. No

Gram 1.....- m210 F. Bt 18 mm.- 374 l. 4 5. 1 (2.-... 21o-328 F. Bt 18 mm.. 33 3. 9 ll. 7 3----; 272-312e F. at 1 nlm.-- 2, 4% 3.0 206. 8 Still bottoms B11111088. 187

Either the third cut from the above distillation, having a saponiiication number closely approaching the theoretical saponiilcation number ofthe octyl ester of O-hydrobenzoic acid ,which is 224, or the crude undistilled ester product may be used in the preparation of the calcium salt useful in the composition of my invention. The calcium salt prepared from the undistilled ester is a somewhat more effective anti-oxidant than is the salt prepared from the ester of greater purity obtained from the distillation. In this instance the calcium salt was prepared from the distilled ester fraction obtained as above described by dissolving 2 mols of the ester in 1000 ml. of alcohol and 1000 ml. of benzol. A cold solution consisting of 2.3 mols of sodium hydroxide in 200 ml. of water was then stirred in. The resultant-solution was then mixed immediately with 1.2 mols of calcium chloride in 250 ml. of water. An additional 1000 ml. .of benzol was then added to dissolve the calcium octyl salicylate and suiiicient water was stirred into the solution to cause separation of the alcohol water layer. 'This layer was drawn olf and the .benzol solution washed twice with warm water. The benzol solution was then filtered using a filter aid and the benzol was then distilled oi under vacuum. 'I'he resulting calcium octyl salicylate had a calcium content of '1.85% as compared to a theoretical content of 7.43%.

Calcium octadecyl salicylate and calcium lauryl salicylate also were prepared by the procedure above described except that octadecyl alcohol and lauryl alcohol were used instead of the octyl alcohol in preparing the esters. The call cium contents of the octadecyl and of the lauryl salicylates thus prepared were found to be 5.08% and 6.10%, respectively, which closely approach the theoretical values of 4.89% and 6.15%.

.The lubricating oil compositions of my invention may also be prepared with advantage by first incorporating the appropriate alkyl ester in a portion of the oil base and then adding`lime to react directly with the ester.- The following example will serve to illustrate the application of this method in the preparation of a lubricating composition containing approximately 5.0% calcium n-butyl salicylate:

To 921.5 grams of a South Texas' pale oil having a Saybolt viscosity of about 500 seconds at 100 F. were added 48.3 grams of n-butyl salicylate, 18.5 grams of lime and 5 ml. of water. This mixture was digested with stirring for two hours during which the temperature was raised slowly to 280 F. The resulting product was then ill-- tered to remove excess calcium. The calcium content of the finished blend was 0.611% compared to 0.51% theoretical. The excess of calcium appears to be due to the presence of a con- ROOC.CeHAOCaOH When preparing the lubricating oil composi-V tions of my invention by neutralization of the ester in the oil as described, it is preferable to effect the neutralization in only a part of the oil eventually to be incorporated in the finished composition. That is, it is preferable first to prepare a concentrate-containing 10 to 25% of the desired calcium alkyl salicylate which may then be admixed with additional oil in order to obtain the composition desired in kthe final product.

The calcium salt of the octadecyl salicylate is a solid at room temperature while the corresponding salts of the lauryl and octyl esters are viscous liquids. At ordinary room temperature all are very soluble in benzene and in petroleum lubricating oils, even in highly'solvent-treated Pennsylvania lubricating oil stocks. However at l'ow temperatures the solubility of the salts prepared from the esters with the higher molecular weight organic radicalsy decreases appreciably particularly in lubricating oilsl prepared from Pennsylvania type stocks.

Incorporation of a calcium alkyl salicylate i a petroleum lubricating oil base causes a marked increase in the sludging time as indicated by the ,Indlana oxidation test. 'I'he extent of the increase in sludging time varies with the amount of the addition agent and is diiferent for different base-oils. For example the addition of 1.33% of calcium octadecyl salicylate to three base oils, derived respectively from a South Texas crude, a. Mid-Continent crude and. a Pennsylvania crude, caused increases in the Indiana sludging time as shown-in the following table:

v I. S. T. Vis. Vil. I. B.T. with 1.33% Bue oil at at V. I. blank cium 210 oil eoyl salicylate Houra Hou" South Texas 513. l 53. 6 14. 4 16 31 81. 0 77. 9 18 54 63. l 102. l 68 300 The effect of the proportion of the addition agent on the Indiana sludging time is shown by a comparison of the' effects produced by adding 1.33% in one instance and 2.00% in another instance of calcium octadecyl salicylate to the same baseoil, the base-oil in this instance being the Sallie Pennsylvania type lubricating oil ,as that used in the foregoing comparison. These effects are shown in the following table:

The length of the induction period, during which the rate of oxygen absorption is retarded,

' is iniiuenced both by the amount of the addition agent and by the particular addition agent 4 gen that may be absorbed before termination oi the induction period is in many instances almost directly proportional to the calcium content of the addition agent. For example, a twice solvent-treated Pennsylvania base-oil containing 2% of calcium lauryl salicylate can absorb almost exactly twice as much oxygen before termination of the induction period as can a blend of the same base oil containing yonly 1% of the same addition agent. At 400 F. the

i `lengths of the induction periods for the last- .mentioned blends, as determined by the true oxidation test, were 90 minutes for the blend containing 2% di the addition agent and 37 minutes for the blend containing 1% of the addition agent. The addition of 1% of calcium octadecyl salicylate, of 1% ofcalcium lauryl salicylate and of 1% of calcium octy1 salicylate respectively, to separate samples of the same base-oil, produced induction'periods of 35 minutes, 37 minutes and 42 minutes in the order named. Calcium Vsalts prepared from the unaistilled esters have a higher calcium content than those prepared from the distilled esters, due to the presence of small amounts of esters o1' the lower molecular weight alcohols in the undistiiled product. The observed greater antioxidant effect ofthe calcium salts prepared from trie undistilled esters appears to be at least in part due to this circumstance.

The chart appearing as Fig. l of the drawings l illustrates the relative effect of the octadecyl,

the lauryl and the octy1 salicylates respectivelyexcept that illustrated by curve e.

on the rate of oxygen absorption. The base-oil in each instance was a twice vsolvent-treated `Pennsylvania lubricating oil stock having a gravity of 28.2 A. P. I., a viscosity of 1445 at 100 F. and of 119.2 at 210 F. and a viscosity index of 107.3. The oxygen absorption tests were carried out at 400 F. Three of these blends i contained 1% of the addition agent. The others contained 2% of the addition agent. In Fig. 1 the rate of oxygen absorption for the blank oil is shown by curve a while the corresponding rates for blends including 1% of octadecy1,lauryl and octy1 salicylates are shown by curves b, c and d, respectively. The corresponding rate for a blend containing 2% of the lauryl salicylate is shown by curve e, while that for a blend containing 2% of the calcium salt prepared from the undistlled lauryl ester is shown by curve f. This chart clearly illustrates the strongly anti-oxidant eiect oi the calcium alkyl salicylates prior to termination of the inductionr period of blends containing them. It also illustrates the eiects of varying both the number of carbon atoms in the alkyl chain and the proportion of the addition agent. As a further illusblends of my invention possess the capability of v inhibiting the strongly pro-oxidant eiect of other addition agents such as calcium phenyl stearate, as well as the capability of inhibiting the pro-oxidant eiect exerted by the presence in the oil of4 copper-lead and cadmium-silver bearing metals. The chart appearing as Fig. 2'

of the drawings illustrates the inhibiting eiect of the calcium salt of the octadecyl ester of salicyclic acid both with respect to the pro-oxidant eiect of a copper-lead bearing metal and the pro-oxidant eect of calcium phenyl stearate.

The base-oil used in the oxygen absorption tests involved in the chart comprising Fig. 2 was a medium heavy Mid-Continent lubricating oil stock `having a gravity of 25 A. P.Y I., a viscosity of 525.9 at F. and a-viscosity index of 77.9.. All of the oxygen absorption tests involved in this chart were conducted at a temperature of 300 F. A copper-lead bearing metal was present in the oil in all of the oxidation tests Curve e shows the rate of oxygen absorption by the blank oil in the absence of the copper-lead bearing metal. Curve a shows the rate of oxyger'i absorption by the blank oil in the presence of the copper-lead bearing metal. Curve b shows the rate of oxygen absorption for a blend including 0.67% of calcium phenyl stearate as the addition agent. Curve c shows the rate of oxygen absorption for a blend containing 0.67% calcium octadecyl salicylate as the addition agent. Curve d shows the rate of oxygen absorption for a blend including as addition agents 0.67 of calcium phenyl stearate and 1.33% of calcium octadecyl salicylate. This chart strikingly illustrates the ability of the calcium salt of an alkyl ester of salicylic acid to inhibit the pro-oxidant effect of a copper-lead bearing metal as well as the strongly pro-oxidant effect of calcium phenyl stearate.

The capability of the addition a ent ployed in the lubricating oil compositigonssofey invention to inhibit the pro-oxidant effect of cadmium-silver bearings is shown by the results oi the Underwood oxidation tests which are given in the table below. The base oil in this instance was a blend having a gravity of 28.7 A. P. I.,'a viscosity of 453 at 100 F. and a viscosity index of 95.4. The blend consisted of 70% of a Mid-Continent solvent refined neutral having a viscosity of approximately 250 at 100 F. and 30% of a' lightly solvent' rened Pennsylvania bright stock having a viscosity of 136.7

-hour periods the neutralization number as determined by A. S. T. M. methods A and B, the bearmg losses and the contents of material insoluble in naphtha and in chloroform were also recorded. The resultsare given in the following table:

Base-oil plus Blank 1.33% 2.00% 3.00%

oil calcium calcium calcium octadecyl octadecyl lauryl salicylicylsalicylate ate ate Original Vis. at l30 m6 207 216 217 oil C. R 0. 35 0. 50 0.72 0.97 0- 05 (l) (l) (l) 351 212 218 224 2. 32 0. 89 0. 89 1. 21 4. 50 0. 38 0. 36 0. 2S hrs 4.60 0.40 0.40 0.30

4. 27 2. 71 1. 20 l. 25 5. 20 0. 00 0. 60 0. 70 c 5. e0 9. 25 0. 70 o. 40 l0 hrs. Bearing loss (0)-. 1. 894 0.792 0.025 0. 001

Naph. insol 0. 47 0. 0l 0. 0l 0.03 CHCII inS0l 0. 21 0. 01 0.01 0. 01 Copper baille (a) Result of test.- (l) (4) (l) (l) 1 Alk. I Slight tarnish. I O. K. l N. G.

Inspection of the data appearing in the above table clearly shows that in the case of the blends including 2% of calcium octadecyl salicylate and 3% of calcium lauryl salicylate, the pro-oxidant action of the iron naphthenate and cadmiumsilver bearing metal had been inhibited as is indicated by the low bearing loss, the low carbon residue. the low neutralization numbers, and by the' small amount of material insoluble in naphtha and in chloroform at the termination of the hour test period. The data also shows that the addition of only 1.33% of the calcium octadecyl salicylate is insuillcient to prolong the induction period of the blend to an extent enabling it to satisfactorily pass this test.

The addition agents embodied in the lubricating oil compositionsI of my invention do not materially increase the film strength of a base-oil in which they are incorporated. However, they are compatible with known nlm-strength agents such as chlorinated diphenyl, brominated diphenyl, sulphurized sperm oil, and the like. In lubricating oil blends including such lm strength agents, the addition agents of my invention effectively inhibit the pro-oxidant eilect that many of these known film-strength agents exert. In the general in such compositions the calcium alkyl salicylates reduce the rate of oxygen absorption and the tendency of the blend to become corrosive even though in some cases they are not capable of completely counteracting the tendency of certain nlm-strength agents to promote sludging. Thus the addition of 2% sulphurized sperm oil to a, Pennsylvania type baseoil containing 11/3% of calcium octadecyl salicylate reduces the I. S. T. to hours, whereas the Indiana sludging time for the same blend without the sulphurized sperm oil was 365 hours as compared to 68 hours for the blank base-oil. However, notwithstanding the adverse eiect of the sulphurized sperm oil on the sludging time, engine tests on these three lubricating oil compositions showed a ring rating of 100% free for y the blend including only calcium octadecyl salicylate and for the blend including sulphurized sperm oil in addition to the salicylate, whereas for the blank oil the ring rating was only 98.7% 1| free with correspondingly higher ring and ring groove deposits.

In service in a supercharged internal combustion engine a blend including only 1% of cal- 5 cium octadecyl salicylate in addition to the baseoil showed a marked superiority over the blank base-oil as is ilrustrated by the following examples. The base-oil used in these supercharged engine tests was a twice solvent-treated Pennlo sylvania .type base-oil. The physical characteristics of the blank base-oil and of the blend prepared therefrom are given in the following table:

Blend including Blank 1% calcium octadecy salicylatc 20 Gravity A. P. I 3.2 28.1 Flash 6m 525 Fire 600 585 Viscosity at 100 F 1445 1408 Viscosity at 210 F 119. 2 120. 4 Viscosit indian..- 107.3 107. 3 Pour, +5 10 Carbon residue 0. 614 0. 66 Ash 0. 00 0.114 Neutralization numbe (l) 1 0. 2 Saponiiication number.. 0. 0. 70 Indiana oxidation test:

S. T., hrs @.0 520.0 Vis. rise 120 F./50 hrs.. 8. 8 9. 0 30 vis. rise 210 F./1oo im; 21. 4 24. c

1 Neutral. 1 Basic.

Engine tests of 150 hours were conducted both on the blank oil and on the blend above described, the intake manifold boost pressuie in each test being maintained at 1.6" vacuum for the first ilve hours, 3.5 lb. gauge pressure for the second live hours, 5.7 lbs. for the third ve hours,

and 8 lbs. for the remainder of the test. Measurements of the cylinder wear and inspections of the piston and ring conditions were made at the end of 89 hours as well as at the end of the 150 hour test period. These inspections showed that both the ring wear and cylinder wear were l lower and that there was less scoring of the rings and cylinder walls for the blend than for the blank oil. Likewise the oil sump was considerably more free from sludge in the test on the blend than in the test on the blank oil. Both the condition of the piston skirt and of the ring belt were cleaner for the test on the blend than for the test on the blank oil. For the test on the blend all rings were 100% free both at the 89 as for the test on the blank oi1 the ring rating was 93.1% free at 89 hours, and only 92.1% free at the end of the test.

The average cylinder wear for the last-de-A scribed test on the blank oil and for the coiresponding test on the blend are shown in the chart appearing as Fig. 3 of the diawings. The values for the average cylinder wear in inches for the test on the blank oil being .00025 at 89 hours and .00046 at the end of the test and for the blend .000175 at 89 hours and .000231 at the end of the test. As is clearly shown by Fig. 3 the rate of cylinder wear in the test on the blank oil increased toward the end of the test, whereas for the blend the rate of cylinder wear, initially less than that for the blank oil, further decreased as the test was continued. The total ring wear loss, expressed in grams, was 1.71 for the test on the blank oil and 0.45 for the test on the blend. The total ring and ring groove dehour inspection and at the end of the test, whereposits for all pistons, expressed in grams, was prising a petroleum lubricating oil and the cal- 19.606 for the test on the blank oil and only cium salt oi the octyl ester of salicylic acid.

'1.968 for theblend. 4. A liquid lubricating oil composition com- I claim: prising a petroleum lubricating' oil and the cal- 1. A 1iquid lubricating oil composition corn- 5 cium salt of the lauryl ester of salicylic acid prising a petroleum lubricating oil and the cal- 5. A liquid lubricating oil composition comcium salt of an alkyl ester of salicylic acid. prising a petroleum lubricating oil and the cal- 2. A liquid lubricating oil compositioncomcium salt of the octadecyl ester of salicylic acid. prising apetroleum lubricating oil and 0.5-5.0% 6. A liquid lubricating oil composition comof the calcium salt of an alkyl ester of salicylic 10 prising a Pennsylvania type petroleum lubricatacid having from 8 to 18 carbon atomsV in the ing oil and a minor proportion of the calcium salt alkyl chain. H of an alkryl ester of salicylic acid.

3. A liquid lubricating oil composition com- WILLARD L. FINLEY.

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