US2738327A - Lithium-strontium soap greases from oxidized petroleum fractions - Google Patents

Description

the waxate soap.

United States Patent LITHIUM-STRONTIUM SOAPGREASES FROM OXIDIZED PETROLEUM FRACTIONS George W. Eckert, Glenllam, N. Y., assignor to The Texas Company, New, York, N. Y., a corporation of Delaware No Drawing. Application December-24, 1952, Serial No. 327,933:

3 Claims. ct. 252-40 This invention relates to improvedlubricating grease compositions and more particularly to lubricating greases containing mixed lithium and strontium soaps of oxidized petroleum fractions.

It is Well known in the art to employ oxidized petroleum fractions as the saponifiable material in grease making, and greases have been prepared-from such materials employing various metals as the metal component of However, these oxidates are considerably different in many respects from the natural fats and fatty acids in their grease making properties, and difficulties have been encountered in producing greases of the desired properties. from these materials. The chief difficulty, which has beenvfound ina greater or less extent with all greases of this typeof the prior .art, is the tendency. of these greases to harden, or set up, in storage. This hardening is very objectionable from the standpoint of marketability, and also seriously impairs the service characteristics of the'greases for many purposes.

In accordance with this invention, very superior lubricating greases, having both excellent lubricating prop-j erties and storage characteristics, are obtained by employing as the essential thickening agent a mixed lithium-strontium soapof a-saponifiable materialresulting from the oxidation of a petroleum fraction, the mixed lithium-strontium soap comprisingsubstantial proportions of each metal soap. The soap may suitably. comprise lithium and strontium oxidatesoaps in, aproportion, of about 1 to 4 to about ,4 to 1 by weighuandpreferably in a proportion of aboutl to 1 to about 4 to l by weight. This mixed base soap is employed in a suitable oleaginous vehicle in varying amounts to produce greases for various purposes ranging from semi-fluid to very stiff. Ordinarily, the soap content of the grease will be from about to about 45 per cent by Weight.

The oxidates employed in preparing the greases of this invention are oxidized petroleum fractions containing considerable proportions of saponifiable materials, or separated saponifiable fractions of such oxidized;

petroleum fractions such as have been employed hereto fore in grease making. They are obtained by oxidizing a petroleum fraction such as a lubricating oil fraction,

crude or refined wax, slack Wax, or petrolatum attelevated:

The mixed lithium-strontium soaps are prepared from.

the petroleum oxidates by any of the conventional methods employed for obtaining mixed base, soaps, such as by coprecipitation or by mixing separately prepared lithium and strontium soaps. They are most conveniently prepared by the coprecipitation method, that is, by

saponification of the oxidate with lithium and strontium. hydroxides or other suitable compounds to' producedirectly a mixed soap of the desired ratio of lithium grease.

andstrontium soaps. An excess of lithium or strontium hydroxide, or of both lithium and strontium hydroxides, beyond the amounts required to react with all of the saponifiable matter is employed in the saponification, Preferably, an excess of lithium or strontium hydroxide is added suificient to give a free alkalinity ofabout 0.01 per cent to about 10 per cent-by weight; of the finished In addition to these special soaps, the greases of this invention may contain any of the usual additives such as, for example, oxidation and'corrosioninhibitors, extreme pressure agents, oiliness agents andso forth, as well as small amounts of additional thickening agents such as polymeric materials and solid lubricants such as carbon black. These greases. may also be mixed; or blended with greases of other types if desired toproduce greases of special properties.

The oleaginous vehicle employed in the grease may be any suitable oil of lubricatingcharacteristics, which may be of mineral, vegetable, animal or synthetic origin, such as have been employed heretoforein, lubricating greases. Suitable mineral oils include both distillate and residualfractions from parafiinic, napth enic or mixed base crude, ranging frorn fairly low to fairly. high ViSr cosities, such as from about 50 to about 1500 seconds Saybolt Universal viscosity at F. These oils may be obtained by, any of theusual refining methodssuch as acid treating, solvent extraction, andso forth. For certain purposes, such as for example the production of lowtemperature greases, various synthetic oils may be employed with particular advantage. As examples of suitable oils of this type may be mentioned high molecular weight aliphatic ethers, such as normal hexyl ether, the alkyl esters of benzoic and phthalic acids, and the aliphatic dicarboxylic acid di-esters, such as di;2-ethyl hexyl sebacate, di (secondary amyl) sebacate, di-Z-ethyl hexyl azelate, di-isooctyl adipate, etc.

Thegrease preparation is suitably carriedout by charging a quantity ofoxidate together with lithium and strontiumhydroxides in proportionate amounts to a-con ventional grease making kettle, where the mixture is maintained at elevated 1 temperature below about 220 'F; with stirring, air blowing or other mechanical agitation untii the saponification'is complete. The temperature is thenincreasedto about 270 F. or higher and main? tained at this increased temperature-for 'a time-sufii'cient to accomplish dehydration. The-lubricating oilincluded in the grease is preferably added to the initial charge also, or only a small amount of the oil may be added to the. initial charge andladditional' oil added during the saponification or after the dehydration to obtain a grease of the desired consistency. Other. saponifiable materials such as the natural fats and oils commonly employed in grease making may also-be addedwhere it isdesiredto obtain a mixed grease.

Greases preparedfrom mixed lithium-strontiumoxidate soaps as described above have-been found; to ,havevery different storage characteristics from, the other. petroleum oxidate greases of the prior art, in additiorrto, generally excellent lubricating characteristics .equivaientfto those obtainable with the very, expensive highly-refiuednatural fats and fatty acids, It is particularly surprising that oxidate greases of excellent lubricating characteristics are obtained employing this combination of: metals, since attempts to produce greases employing both 'litghium oxidate soaps and strontium oxidate soaps separately have given veryainpromising results, the greases produced being gel-like and unsatisfactory in texture and softening to an objectionable degree upon working, For example, a grease comprising 20 per cent'of-lithiumoxid e; soap in a .naphtl1ene. base lubricatin il hay n 174 and a worked penetration of 274. A grease comprising 20 per cent of strontium oxidate soap in a lubricating oil of the same type had an original unworked penetration of 217 and a worked penetration of 312, and in addition it had a very low dropping point of only 222 F. However, greases prepared according to this invention by employing both lithium and strontium oxidate soaps in combination have been characterized by excellent texture, and have tended to harden slightly rather than to soften upon working. In addition, these greases very unexpectedly showed no hardening upon storage even for long periods of time.

The following example is given as illustrative of the greases of this invention.

EXAMPLE A lubricating grease was prepared from the following materials:

Grams Wax oxidate 3,304 Mineral lubricating oil 5,600 LiOH (10%) (aqueous solution) 8,000 S1(OH)2.8H2O 900 The wax oxidate employed had a neutralization number of 250, a saponification number of 390 and contained 14.0 per cent of unsaponifiables. It was obtained by oxidizing a paratfin wax obtained from a pressed distillate of SAE 10 grade. The oxidation was carried out at a temperature of 270 F., a pressure of p. s. i. g. and an air rate of 20 cubic feet per hour per pound of charge.

The mineral lubricating oil was a refined naphthenc base distillate oil having a Saybolt Universal viscosity at 100 F. of about 300 seconds.

The grease preparation was carried out by charging the above materials in the amounts given above to a steamheated grease kettle and heating for two hours at 200 F., with continuous stirring, until the saponification was substantially complete. The temperature was then increased to 300 F., and the mass held at this temperature for two hours to dehydrate, after which the temperature was allowed to fall and the grease finally drawn at 216 F. A smooth, buttery grease was obtained. The following table shows the storage characteristics of this grease (Grease No. 7 of the table) as compared with those of greases prepared from the same mineral oil and oxidates of the same type, but containing ditferent metals in place of lithium-strontium combination.

The above table shows the striking difference in storage characteristics between the lithium-strontium oxidate grease and those of the other metal oxidate greases representative of the oxidate greases of the prior art. As shown by the table, the lithium-strontium grease showed substantially no change in penetration on either the worked or the unworked basis during a six months storage test. On the other hand, all of the other oxidate greases hardened continuously during storage on the basis of their unworked penetrations, with very large decreases in penetration occurring after only two days of storage. The lithium-strontium grease was also very resistant to change upon working, as shown by the small spread between the values found for the unworked and the worked penetrations during the test, and the change which occurred was a slight hardening instead of the softening which is a general characteristic of other oxidate greases in this test.

in addition to its excellent storage properties as discussed above, the lithium-strontium oxidate grease of the example had all of the lubricating properties required of a very superior ball and roller bearing grease, as shown by the standard tests, including a dropping point of 407 F., a high mean Hertz load, without E. P. additives of 31, excellent water resistance, as shown by a loss of only 4 per cent in the dynamic water resistance test, and satisfactory rust resistance for an uninhibited grease. In addition, the Navy gear wear test (MIL-G-3278) on this grease was as follows: 0.4 gram Weight loss, brass on steel, 5 pounds load, 1000 cycles; and 2.2 grams weight loss, brass on steel, 10 pounds load, 1000 cycles. These values are equivalent to those obtainable with good grade com mercial ball and roller bearing greases. Very good results were also obtained with this grease in the torque breakdown machine test with a Federal ball bearing at 250 F., run continuously for 168 hours. The machine was shut down for observation at the end of this time with no failure. No grease leakage had occurred and the hearing condition was satisfactory.

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.

I claim:

1. A lubricating grease comprising essentially an oleaginous vehicle as the chief constituent thickened to a grease consistency with a mixed lithium-strontium soap Mineral oil, percent Penetration, ASTM, 77 F.:

Unworked basis:

Original grease. After 2 days After days After 6 months Worked basis: Original grease 298 331 316 24a After 2 days 201 310 291 263 After 14 days.

After 30 days.

After 90 day After 6 month 1 Sample containing 0.5% of PSF-M, a commercial amine-type oxidation inhibitor.

of a saponifiable material obtained by the oxidation of a petroleum wax having a saponification number in the range from about 175 to about 450, said mixed lithiumstrontium soap consisting of lithium and strontium soaps in a proportion by weight from about 1 to 4 to about 4 to 1, and containing free alkalinity in an amount equal to about 0.01 to about 10 per cent by weight of the grease,

2. Claim 1 wherein the soap consists of lithium and strontium soaps in about a 3 to 2 proportion by Weight.

3. A lubricating grease comprising essentially a naphthene base distillate lubricating oil having a Saybolt Universal viscosity of about 100-400 seconds at 100 F. as the chief constituent, thickened with about 25-45 per cent by weight of a mixed lithium-strontium soap of a saponifiable material having a saponification number in the References Cited in the file of this patent UNITED STATES PATENTS 2,409,950 Meyer Oct. 22, 1946 2,417,428 MeLennan Mar. 18, 1947 2,417,429 McLennan Mar. 18, 1947 2,669,543 Hirsch Feb. 16, 1954

Claims (1)

1. A LUBRICATING GREASE COMPRISING ESSENTIALLY AN OLEAGINOUS VEHICLE AS THE CHIEF CONSTITUENT THICKENED TO A GREASE CONSISTENCY WITH A MIXED LITHIUM-STRONTIUM SOAP OF A SAPONIFIABLE MATERIAL OBTAINED BY THE OXIDATION OF A PETROLEUM WAX HAVING A SAPONIFICATION NUMBER IN THE RANGE FROM ABOUT 175 TO ABOUT 450, SAID MIXED LITHIUMSTRONTIUM SOAP CONSISTING OF LITHIUM AND STRONTIUM SOAPS IN A PROPORTION BY WEIGHT FROM ABOUT 1 TO 4 TO ABOUT 4 TO 1, AND CONTAINING FREE ALKALINITY IN AN AMOUNT EQUAL TO ABOUT 0.01 TO ABOUT 10 PER CENT BY WEIGHT OF THE GREASE.