US2789091A - Traction motor gear lubricant - Google Patents

Description

2,789,091 TRACTION Moron GEAR LUBRICANT Fred T. Crookshank, William E. Jordan, Gordon S. Bright, and Roy F. Nelson, Port Arthur, Tex., assignors to The Texas Company, New York, N. L, a corporation of Delaware No Drawing. Application August 25, 1955, Serial No. 530,642

6 Claims. 01. 252-42 This invention relates to a new traction motor gear lubricant characterized by improved low temperature performance and freedom from thickening in service.

The traction motor gears of diesel electric motors have been lubricated very successfully for many years by a product comprising 35 to 65 percent residual oil and 65 to 35 percent of an asphalt derived by air-blowing of an asphaltic residuum. These asphalt-thickened residual oils have given excellent protection against gear wear but have had two major deficiencies, namely thickening caused by poor oxidation resistance and a tendency to set up at low temperatures. These deficiencies have limited the use of asphalt-thickened residual lubricants in the so-called tight gear cases of the EMD diesels and in winter lubrication of traction motors in general in northern areas.

This invention is concerned with the development of a superior traction motor gear lubricant which retains the excellent protection against gear 'wear of the previous asphalt-thickened lubricant and at the same time exhibits good low temperature performance and freedom from oxidative thickening in service.

The traction motor gear lubricant of this invention comprises more than 90% by' Weight of an oxidate derived from deasphalted, dewaxed paralfin base residuum and 1 to by weight of alkali metal soap derived from a fat. The lubricant of the invention also usually contains l to 5% by weight of a residual oil which is used as a carrier for the introduction of the soap into the oxidate component which has a Neut. No. less than 3 and a Sap. No. less than 30 and is derived by oxidizing a deasphalted, dewaxed paraflin base residuum with air non-catalytically at atmospheric pressure and a temperature between 450 F. and 520 F.

The desired low temperature properties and freedom fromthickening as a result of oxidation are only obtained with oxidates derived from deasphalted' and de waxed parafiin base residuums. The gear lubricants formulated with oxidates derived from mixed naphtheneparalfin base residuums, from dewaxed but asphalt-contaming parafiin base residuum and from a deasphalted but wax-containing parafiin base residuum do not possess comparable low temperature performance and set up in storage. Even though the oxidates were all obtained under similar processing conditions, the only gear lubricant which gave the desird'low temperature performance and freedom from oxidatfv'e thickening was the one containing' an'ox'idat'e' from the deasphal'ted and dewaxed parafiin base residuum.

The alkalim'etal soap component of the gear lubricant of the invention can be derived from animal fats and vegetable oils, from the fatty acid components of these glycerides or' from their monoe'sters. Tallow, lard, castor oil, hydrogenated castor oil, fish oils, soybean oil, stearic acid; oleic acid, l2=hydroxystearie acid, and palmitic acid are examples of materials that can be used to form the alkali metal soap. Sodium and? lithium soaps can be used but sodium soaps are" generally employed because ited States Pat falls between 1 and 5 weight percent of the gear lubricant and usually between 2 and 4 weight percent. An alkali metal soap content of about 2.5 weight percent has been found to give excellent thickening properties to the gear lubricant.

The residual oil employed as a carrier for the introduction of the alkali metal soap into the oxidate also constitutes l and 5 weight percent of the lubricant composition. Since it is convenient to use the residuum carrier in an amount equal to that of the alkali metal soap, a 50-50 blend of alkali metal soap and residual oil in an amount equivalent to 5 weightpercent of the total gear lubricant has generally been employed.

The composition of the residual oil carrier is also not critical. Unrefined parafiin base, naphthene base and mixed base residua are used. An unrefined mixed parafiin-naphthene base residuum has been extensively used as a carrier oil in the gear lubricants described hereafter. The deasphalting and dewaxing procedures which are necessary to obtain a necessary charge material to the oxidation step are conventional in the art. The deasphal'ting procedure is the conventional propane deasphalting procedure which involves contacting the residual oil propane under pressure with the resulting precipitation of vantageously effected by use of a centrifuge. In this so;

called centrifuge dewaxing, the residual oil' is cut back with naphtha and subjected to centrifuging whereby the waxy components are separated from the residualfrac tion. After the centrifuging operation, the naphtha is flashed from the dewaxed residuum. v

The typical tests on a deasphalted, dewaxed parafiin base residuum are a pour of +15 F., a flash. of 570, F. and an sUs viscosity at 210 F. of 198. It will be noticed that a deasphalted, dewaxed paraflin base residuum has a relatively low pour as contrasted with the typical residual oils whose pours range from 30 to F.

Oxidation of the deasphalted, dewaxed parafiln base residuum is effected non-catalytically at atmosphericpressure and a temperature of 450 to 520 F. and at an air rate between 0.2' and 2.0 cubic feet per hour per pound of residuum and at oxidation periods of 6 to 20 hours.

Preferred oxidation conditions are at temperatures be tween 480 and 500 F., air rates of about 0.4 to 1 .5 cubic feet per hour per pound of residuum, atmospheric pressure and an oxidation period of 6 to 15 hours.

The oxidates obtained from the deasphalted, dewaxed parafiin base residuum under the afore-described condi% tions usually have properties falling within the follow Typical properties obtained by oxidation of a propane deasphalted, centrifuge dewaxed parafiin base residuum having an SUS viscosity at 210 F. of 198, a flash of 575 F. and a pour of +15 F. are shown in Table I. In the laboratory run, 100 lbs. of residuum were oxidized at 480 F., atmospheric pressure and an air rate of 1.22 cubic feet per pound of oxidate per hour for about 8 hours. In the plant run, 8,500 lbs. of the same residuum were oxidized at an average temperature of about 495 F., atmospheric pressure and an air rate of 0.47 cubic foot per pound per hour for a period of 14 /2 hours.

The data in the foregoing table clearly indicate that oxidates of similar properties are obtained in laboratory and plant operation. Since the plant unit was not equipped with a cooling coil, the air rates were lowered and the reaction time increased in the plant run to maintain the temperature at the desired 490 to 500 F. level.

The three most important properties of a traction motor gear. lubricant are low temperature performance, resistance to thickening by oxidation, and, ofprirnary importance, an ability to prevent gear wear. The ability of the gear lubricant to prevent gear wear is measured by the modified four-gram Timken test which measures film strength. Low temperature performance properties are measured by the simulated TMG torque test while resistance to oxidation thickening is measured by the modified U. S. Steel Corporation gear oil thickening test, the oxidation thickening test and the ASTM bomb oxidation tit. A brief description of these tests is presented herea er.

The modified four-gram Timken test is run on the Timken machine by a procedure involving lubricating the ring by spreading four grams of lubricant evenly on its surface, applying a 30 1b. load and running the machine until ,the ring scores. The time required for scoring is noted and reported.

The simulated TMG torque test, which evaluates the low temperature starting characteristics of the lubricant, is run in a washing machine transmission, the test unit and lubricant are cooled to test temperature and the power requirement for starting the unit is determined by means of a recording watt meter. The test is considered a failure when the starting power exceeds 4,000 watts, when the electric motor smokes on starting or when the motor is on starting windings for 7 seconds or longer.

The oxidation thickening test, also called a static oven heating test, involves measurement of penetration before and after heating in an oven for prescribed periods of time. In this test the penetration is initially determined, the lubricant placed in a 210 F. electrically heated natural convection oven for a thousand or a hundred hour period. At the end of the period, the penetration is again measured and the degree of change is calculated on the basis of the initial test.

The modified U. S..Steel Corporation gear oil thickening test involves passing 10 liters of dry air through 300 ml. of test oil, which is maintained at a temperature of 203 F. during the 312 hour period in which the air is passed through the test oil. At the end of this period the percent decrease in penetration is measured. A small percentage change in unworked penetration indicates a lubricant which is stable to oxidation thickening.

The ASTM bomb oxidation test is well known in the TABLE II Lubricant of Asphaitic Example 1 Base Lubricant ASTM Penetration, 77 F- Unworked 327 Y 320 Worked 354 Too Stifl ASTM Bomb Oxidation Test, p. s. 1. g. 21 20 Drop/100 Hr...- Mod. 4 Gr. Timken Test, 30# Load, Minutes to Fail 22 18 Simulated TMG Torque Test:

Temp., F so 20 77 50 Starting Load, Max. Watts 3,500 8, 700 1,800 4, 000+ Time on Starting windings, Sec--. 3 7 1 7 Mod. U. S. Steel Gear Lube Thickening Test:

Airblown 312 Hr. at 203 F., Penetration Decrease, Percent, 77 F.-

Unworked 12. 4 67 Worked 8. 5 Too Stifl Stggg; Stability, ASTM Penetration, 0 After 6 Mo.

Unworked 307 Worked. 358 Appearance.... OK

The data in the above table indicate that the product of this invention is about equivalent to the prior art' 4 art and involves measuring the pressure drop in p. s. i. g. obtained after a hour period during which the test lubricant is subjected to oxidation in a bomb at prescribed temperature conditions.

A traction motor gear lubricant was prepared by adding to the oxidate of deasphalted, dewaxed paraflin base residuum obtained in plane manufacture, a 50-50 mixture of sodium tallowate and a raw mixed parafiin-naphthene base residuum. The details of the preparation of this product are set forth in Example 1.

Example 1 A mixture of sodium tallowate and unrefined mixed parafiin base residuum was prepared by saponification of 24 pounds of hog tallow with 8 pounds of 49% caustic in the presence of 10 pounds of water and 12 pounds of raw mixed parafiin-naphthene base residuum at a temperature of to F. An additional 13 pounds of unrefined mixed paraflin-naphthene base residuum was added during dehydration of the saponified soap at a temperature between 260 and 300 F. .To the resulting mixture comprising 22.22 pounds of sodium tallowate and 22.22 pounds of raw mixed paraffin-naphthene base residuum, 849 pounds of plant manufactured oxidate was added at a temperature about 130 to 300 F. with stirring.

After addition of all the oxidate, which took about 15 hours, the product was pumped through a 60 mesh screen into drums. The resulting product, having an approximate composition of 95% oxidate, 2.5% sodium tallowate and 2.5% residuum, was a tacky semi-fluid grease. The properties of this grease are shown in Table H.

The properties of a commercially available traction motor gear lubricant which has large volume sale and which comprises 58 percent by volume of an unrefined residuum and 42 percent by volume of an asphaltic material obtained by air blowing of a residuum are also shown in Table II.

product in anti-wear properties as measured by the modified four-gram Timken test. However, the low temperature properties of the product of this invention, as measured by the simulated TMG torque test, are substantially better than those of the asphaltic base prior art lubricant.- The superiority of the product of this invention to the prior art product is demonstrated in the modified U; S. Steel Corporation gear lube thickening test, which is considered to be the most applicable for determining.

thickening resistance since it compares more directly with the dynamicoxi'dation conditions encountered a churning gear case during use. In this test, the worked penetration of the prior art product could not be determined and the unworked penetration decreased 67% while the product of the invention showed a 12.4% decrease in unworked penetration and only a 3.5 decrease in worked penetration.

The necessity of formulating the traction motor gear lubricant from an oxidate derived trom a deasphalted dewaxed residuum is shown in Table III. In this table traction motor gear lubricants containing as their major components oxidates derived from other residua are compared with the product of this invention containing an oxidate derived from a deasphalted, dewaxed paraflin base residuum.

The oxidates were obtained from the difierent residua 6 from a blend of a partially deasphalted mixed naphtheneparafiin base residuum containing a portion of unrefined naphthene base residuum. The blend from which the oxidate was derived had an SUS viscosity at 210 F. of 160, a flash of 540 F., and a pour of +70 F.

For comparison purposes, the lubricant composition of this invention is designated as lubricant E and is also included in Table ill. This product comprises 2.5 percent sodium tallowate, 2.5 percent unrefined mixed naphthene-paraflin base residuum and 95 percent of the laboratory oxidate obtained from deasphalted, dewaxed paraiiin base residuum; the properties of this oxida'te are shown in Table i.

All of the above products were prepared by a procedure similar to that used in Example 1. The properties of these gear lubricants are shown in Table III.

TABLE III Test Results A B G D E ASTM Penetration, 77 F.:

Unworked 282 170 226 169 325 'Wor rerl 373 329 385 337 :354 ASTM Bomb OxidatiouTest, p Drop/100 Hr 26, 26 16, 16 11, 11 16, 17 17, 17 Mod. 4 Gram Tirnkeu Test, 30 Load, Minutes to Fail. 7, 7, 14 24, 13, 12 7, 10 14, 13 Simulated Tl G Torque Test: v 317113., F .5. 5O 40 40 4 0 30 30 20 Starting Load, Max. Watts 8, 400 3, 600 3, 500 3, 700 3, 300 3. 700 3, 300 3, 700 3, 600 3, 700 Time on Starting Winding, Sec 1 7 2 4 3 7 4 7 Oven Oxidation Test, 210 F;

ASTM Penetration, 77 F., Percent Decrease After 1,500 Hr.- V I Unworked 13. 5 -l2. 3 22. 0 5. 0 20 (1,000 Hr.) Worked 0.5 5.8 1.4 1.7 --l.9

Appearance Light skin (1,000 Hr.)

Mass hardened, but wor red down O K Storage Stability:

After Six Months- Unworked 325 159 168 167 307 Worked. 379 338 302 339 358 Appearance OK Muss hardened, but worked down OK at similar conditions of temperature, pressure, air rate and time. The reaction conditions were those used in the laboratory preparation of the oxidate shown in Table I, namely a temperature of 480 F., an air rate of 1.22 cubic feet per pound per hour, atmospheric pressure, and an oxidation period of 8 hours.

The compositions of the various lubricants compared in Table Hi were as follows:

Lubricant A comprises 2.0% sodium tallowate, 2.0% unrefined mixed parafr'in-naphthene base residuum and 96% of an oxidate derived from the same unrefined mixed naphthene-paraiiin base residuum used as a carrier for the soap. The properties of the residuum prior to oxidation are an SUS viscosity at 210 F. of 725, a flash of 630 F., and a pour of +50 F.

Lubricant B comprises 1.5% sodium tallowate, 1.5% of an unrefined mixed naphthene-base paraffin-base residuum (the same as used in lubricant A), and 97% of an oxidate obtained from a mixture of 60% propane deasphalted paraffin base residuum and 40% of a propane deasphalted parafin base residuum which has been subjected to centrifuge dewaxing. The residuum blend from which the oxidate was derived was only 40% dewaxed and had an SUS viscosity at 210 F. of 176, a flash of 575 F., and a pour of 85 F.

Lubricant C comprises 2.5 percent sodium tallowate, 2.5% unrefined mixed naphthene-parafiin base residuum (same as used in lubricant A), and 95% of an oxidate obtained from propane deasphalted paraffin base crude residuum having an SUS viscosity at 210 F. of 272, a flash of 625 5., and a pour of +70 F.

Lubricant D comprises 2.5% sodium tallowate, 2.5% unrefined m'med naphthene-paraffin base residuum (same as used in lubricant A), and 95 of an oxidate obtained The data in the foregoing table clearly indicate the importance of using an oxidate derived from deasphalted, dewaxed residuum in order to produce a product having the desired low temperature properties and resistance to oxidation hardening. Examination of the ASTM penetration data indicates that the products derived from the residua oils other than a deasphalted, dewaxed parafiin base residuum set up appreciably on the unworked penetration basis. These products, particularly lubricants B, C and D are also poor in storage stability. In addition, all of the products, particularly lubricant A, are inferior to the lubricant composition of this invention in low temperature properties as measured in the simulated TMG torque test. Lubricants B, C and D give results 10 to 20 degrees higher than that of lubricant E, whereas lubricant A gives a result 30 degrees higher than lubricant E. In addition, lubricant A also devel oped a light skin in the oven oxidation test while lubricants B, C and D hardened in this test.

The results in the above test on lubricants A, B, C and D were so poor they were not subjected to the modi fied U. S. Steel Corporation gear lubricant thickening test which is the most severe of all the oxidation hardening tests.

In addition to the above screening tests, the traction motor gear lubricant of this invention has been in service in four diesel locomotives for periods from 7 months to over a year. Three of the tests are being carried out with the traction motor gear lubricant of the invention shown in Table II in an Alco 660 H. P. switch diesel locomotive and the fourth is being used in a new EMD-TR6 diesel electric switch locomotive of 600 H. P. The extensive nature of these service trials of the lubricant is shown in Table IV.

The trial of locomotive B was interrupted about midway during its service trial and a sample was removed from the case. Test results on the lubricant removed were as follows:

ASTM penetration, 75 F.:

Unworked 318 Worked 35;

The simulated TMG torque test was passed at 30 F. and readings of 27and 35 minutes to failure were obtained on check runs in the modified four-gram Timken test" with a 30115. load. Inspection of the gears showed that there was no wear.

Obviously, many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof and, therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

'1. A "gear lubricant comprising 1 to 5 percent alkali metal soap, 1 to 5 percent residual oil and more than 90 percent of an oxidate obtained by air oxidation of dewaxed, deasphalted parafiin base residuum, said oxidate having a Neut. No. of 0.8 to 3 and a Sap. No. of 15 to 30 and an SUS viscosity at 210 F. of 950 to 1350.

2. A gear lubricant according to claim l in which saidoxidate isob'taiiied--bynon -catalytic air oxidation of-the-s'aid deasphalted, dewaxed parafiin base residuum at atmospheric pressure, at a temperature of 450 to 520' 5 F. and an air rate betw'een 0.2 and 2.0 cubic feet per hour per pound of residuum.

3. A gear lubricant according to claim 1 comprising 1 to 5 percent sodium tallowate and 1 to 5 percent unrefined mixed naphthene-parafiin' base residuum. I

4. A gear lubricant according to claim 1 comprising 93 to 97 percent oxidate, 2 to 4 percent alkali metal soap and 2 to 4'percent residual oil.

5. A gear lubricant comprising 2.5 percent sodium tallowate, 2.5 percent unrefined mixed naphthene-parafiin base residual oil and 95 percent oxidate having a Neut. No. of about 1.1, a Sap. No. of about 20, an SUS viscosity at 210 F. of about 1,080, said oxidate having been derived by non-catalytic air oxidation of a dewaxed, deasphalted paratfin base residuum at atmospheric pressure and a temperature about 495 F. 1

6. A gear lubricant comprising 2.5 percent lithium I tallowate, 2.5 percent unrefined mixed naphthene-parafi'ln base residual oil and percent oxidate having a Neut. No. of about 1.1, a Sap. No. of about 20, an SUS viscosity at 210 F. of about 1,080, said oxidate having been derived by non-catalytic air oxidation of a dewaxed, deasphalted paraflin base residuum at atmospheric pressure and a temperature about 495 F.

References Cited in the tile of this patent UNITED STATES PATENTS

Claims (1)

1. A GEAR LIBRICANT COMPRISING 1 TO 5 PERCENT ALKALI METAL SOAP, 1 TO 5 PERCENT RESIDUAL OIL AND MORE THAN 90 PERCENT OF AN OXIDATE OBTAINED BY AIR OXIDATION OF DEWAXED, DEASPHALTED PARAFFIN BASE RESIDUUM, SAID OXIDATE HAVING A NEUT. NO. OF 0.8 TO 3 AND A SAP. NO. OF 15 TO 30 AND AN SUS VISCOSITY AT 210*F. OF 950 TO 1350.