US2360631A - Lubricant - Google Patents

Description

Patented Oct. 17, 1944 LUBRICANT John C. Zimmer, Union, and Arnold J. Morway, Clark'Township, Union County, N. J., assignors to Standard Oil Development Company, a

corporation of Delaware No- Drawing. Application December 9, 1942, Serial No, 468,422

8 Claims.

The present invention relates to improved stable lubricating compositions, particularly to lubricating greases stable at high temperatures. More particularly'the invention relates to grease compositions suitable for the lubrication of sealed anti-friction bearings, such as ball bearings and roller bearings.

It is known in the art to prepare various lubricating grease compositions adapted for particular uses. The uses in which grease compositions are employed present a wide variety of conditions and generally a grease prepared with a given set of conditions in mind is not suitable for use under a different set of conditions. The operation of mechanical mechanisms either at high temperatures or in the proximity of high temperatures offers a difl'icult lubrication problem particularly where greases are used as the lubricant. Al-

though not unique in this respect, small electrical generators, such as those attached to internal combustion engines provide a convenient example of the requirements in high temperature lubrication. In their construction these generators contain sealed and lubricated anti-friction bear= ings which it is contemplated will not need replacement during the life of the generator. When the motors 'to which these generators are attached are operated over an extended period of time, these generators due to heat radiation, conduction and other causes, attain temperatures which ordinary greases will not withstand.

High temperature greases such as the sodium soap greases containing excess alkali are known to the art. However, they are quite water-sob uble and readily disintegrate under humid conditions and unless properly made are not stable in storage. Thisinstability in storage is evidenced by'separation occuring between theoil and the soap. To overcome this instability in storage, large amounts ofhigh molecular weight sodium soaps, say 25% or more, have been used in compounding the grease. Although the conventional greases containing these large amounts vide a high temperature grease which is stable against bleeding during storage. further objects will be apparent to those skilled in the art from a reading of the following description.

The grease composition made in accordance with the present invention comprises essentially a lowpour point lubricating mineral oil distillate,

an alkali soap of an unsaturated fatty acid and a saturated fatty acid soap of an amphoteric metal.

It has now been found that it requires less of the soaps of the fatty acids obtained from rape seed oil or mustard seed oil which contain high percentages of erucic acid, to produce a grease which is stable in storage. Greases containing soaps of these acids, particularly those soaps having some excess alkali which is necessary to preserve the high heat resistance, do not possess desirable resistance to the action of water. It has further been discovered that by the use of small amounts of saturated fatty acid soaps of amphoteric metals, the compositions of the invention can be made to appear neutral or slightly acid to a hydrogen ion indicator such as phenol-phthalein, thus attaining the water-resistance of a neutral or acid grease while preserving the high heat resistivity of the slightly alkaline greases. lhe-greases of the present invention are especially advantageous in that stability during storage is obtained without at the same time producing a grease which becomes stifi'f and hard at temperatures above 200 F. The greases of the present invention do not lose their grease consistency or become thick and stiff at temperatures as high as 400 F. A small amount of an anti-oxidant such as say 0.2% of phenyl alpha naphthylamine, dyes or other addition agents may be added if desired, for example metal deactivatorsextreme pressure agents, etc.

Although any of the numerous types of low pour point lubricating oils may be used as the base for compositions made nearly in accordance with this invention, it is preferred to use a Coastal type oil having a viscosity in the range of from about 50 to 1000 seconds S. U. V. at F. and a cold test below 0 F.

For the formation of the soaps utilized in the production of the greases any fat or fatty acid, such as mustard oil or rapeseed oil, containing erucic acid, which is an unsaturated acid of 2 carbon atoms to the molecule, maybe used. For the production of the soaps of the amphoteric metals it is preferred to use stearic acid, although any of the other well-known saturated acids of high molecular weight such as the Other and oil may be used. The amphoteric metals which are well established and recognized in the art arelamply illustrated by zinc, aluminum, or iron. Instead of employing saturated fatty acid soaps of amphoteric metals, the naphthenates,

or salts of any acid having an iodine number ,saturated acids derived from hydrogenated fish Several drops of a .05% solution of phenolphthalein placed on a'film of the grease at room temperature showed no change of color after minutes.

Example II V Percent Fatty acids obtained from mustard oil or containing substantial amounts of erucic acid 13.00

' Zinc naphthenate 1 0.50 Aluminum stearate 0.50 NaOH 1.67 Lubricating oil (low pour Coastal oil).. 82.83

mixed with the oil by heat and agitation or 4 preferably the fat or fatty acids to be combined with the alkali may be dissolved in a portion of the lubricating oil by heating the oil sufliciently to dissolve the rat or acid in the oil, re-

acting the fat orfattyi acid with sodium hydroxide, or other alkali metal hydmxide such as lithium hydroxide, or alkaline earth metal hydroxide, such as calcium hydroxide, preferably dissolved in water, and then the remainder-of the lubricating oil having the soap of the amphoteric metal dispersedtherein' may be added after which the mixture is brought to a clear solution and the water driven ed by heating and stirring, the anti-oxidant added and the mixture permitted to cool. It is preferred to make the soap of the amphoteric metal separately and then dissolve it in a portion of the lubricating oil although it is quite possible to produce the -soap of the amphoteric metal in situ in the oil.

Greases of varying consistency to meet the demands of particular conditions may be secured by varying the soap content of the grease .within specified limits. The composition of the grease will be approximately as follows: The quantity of oil in the grease will range from about 74% to 89.75%, alkali soaps of fatty acids in which 10% to 25% and the soap of amphoteric metal will run from about 0.25% to 1% with varying amounts up to 0.5% of other additives such as oxidation inhibitors. The following examples will serve to illustrate specific embodiments of the invention.

parts by weight of the rapeseed oil were mixed with parts of the hydrocarbon lubricating oils. mixture was then heated while stirring until about 150 F., whereupon a 25% solution of caustic soda was added, the amount being about 3% of dry caustic soda. Heat was continued until all water was driven ofi (an analysis of the grease at this stage should show a free alkalinity of approximately 0.05 'to 0.15% as NaOH). The aluminum stea-rate dispersed in a small amount of the oil together with the balance of the oil was then added. The temperature was then raised to 400/450 F. at which temperature heating was discontinued: The grease was stirred until the temperaturehad dropped to 180 F. and then drawn off. 'The grease thus produced tested as follows:

Penetration 192 Worked penetration.-. 195

Melting point This grease prepared by the method'described in Example I showed the following characteristics:

. Penetration 276 Worked penetration 280 Melting point F 370 No effect on phenolphthalein solution.

What is claimed is:

1. An improved lubricating grease composition comprising a low pour point lubricating mineral oil distillate, 10-25% of an alkali soap containing excess alkali, a substantial portion of which is a soap of a mono carboxylic, mono olefinic aliphatic acid of twenty-two carbon atoms and 0.25-1% of a soap of an amphoteric metal and an acid having an iodine number under 30.

2. A composition as defined by claim 1 m which I the soap of an amphoteric metal and an acid haverucic acid predominates will range from about ing an iodine number under 30' is aluminum stearate.

3. A composition as defined by claim 1 in which the soap of an amphoteric metal and an acid having an iodine number under 30 is zinc naphthenate.

4. An improved lubricating grease composition comprising a low pour point lubricating mineral oil distillate, 1025% of the sodium soap of a mono carboxylic, mono olefinic aliphatic acid of 22 carbon atoms containing excess soda and 0.254% of a plurality of soaps of amphoteric metals and acids having an iodine number uh- V der 30. Y

5. Animproved lubricating grease composition comprising a low pour point lubricating mineral 011 distillate, of the sodium soap of erucic acid containing excess soda and from 0.25-1.0% aluminum stearate.

' 6. An improved lubricating grease composition comprising a low pour point lubricating mineral oil distillate, 10-25% of the sodium soap of erucic acid containing .05-.15% excess soda, 0.5% aluminum stearate and 0.5% zinc naphthenate.

'7. An improved lubricating grease composition comprising a low pour point lubricating mineral ofl distillate, 10-25% of the sodium soap of mono carboxylic acids derived. from rape seed oil containing .05.15% excess soda and .25-1',.% of a plurality of soaps of amphoteric metals and acids having an iodine number under 30.

8. An improved lubricating grease composition comprising a low pour point lubricating mineral oil distillate, 1025% of the sodium soap of mono carboxylic acids derived from mustard seed oil containing,.05-.15%,,ex&ss-.soda, 0.5% aluminum stearate and 0.5%"zinc naphthenate.

JOHN C. ZIMZMER. ARNOLD J. MORWAY.