US2522460A - Lubricating grease composition - Google Patents

Description

Sept. 12, 1950 Y 'A. J. MoRwAY ETAL l .'LUBRIcAT-ING GREASE COMPOSITION Filed Dec. 15, v194'? 5 w a om@ om@ 05.02. or@ 0mm oww 2N o2 o5 om;n o2 o: om oro m m m w 5 L o QN wa u@ om ww Ndjmd Z .l-O.. P( O 30 23N OP D D \rJ.rz.u u 0.? om e o o 01N. .la OH 0.o n a o fz a@ O w- "Plassula (Ls/me) JU/J0 2094.20 NY mw, ...idoknmmm um md Patented Sept. 12, 1950 Arnold J. Morway,

Clark Township,

Union County, N. J., and Alan Beerbower, Baltimore, Md., assignors to Standard Oil Development Company, a corporation of Delaware Application December 13, 1947, Serial No. 791,644

1 Claims.

This invention pertains to lubricating grease compositions and particularly to grease compositions Which are stabilized against oxidation.

Lubricating gre-ases normally consist largely of alkali and alkaline earth metal soaps dispersed in lubricating oil. The soaps are prepared by the neutralization of fatty acids or by the saponification of fats. Various types of fats and fatty acids are commonly used, among them hydrogenated materials, and the latter have been found to be more susceptible to oxidative deterioration probably as the result of destruction of natural inhibitors during hydrogenation. While most lubricating greases prepared from fatty acids and/or fats tend to oxidize to some extent those prepared from hydrogenated fats or fatty acids, as for example hydrogenated fish oil acids are particularly susceptible to oxidation. Aside from their tendencies toward oxid-ation these materials give excellent greases. In other respects these materials combine Well with mineral oil to produce good grease-type lubricants. They are compatible with various special additives such as extreme pressure agents, corrosion inhibitors and the like.

Because of the tendency of hydrogenated fatty materials toward oxidation and resultantl instability, these materials commonly deteriorate early in use. Such deterioration results first in forming peroxides, lactones, and other oxygen bearing materials. These materials catalyze further oxidation in the lubricant causing it to become rancid and foul smelling and they induce the separation or bleeding of oil in storage from the soap which forms the grease structure. A similar separation occurs in prepacked bearings either in storage or in service.

In addition, the acids which are formed as the result of oxidation frequently react chemically with materials in the bearings which are intended to be lubricated especially during storage or long periods of inactivity. The reaction products tend to clog the parts and prevent proper lubrication and may make it impossible to move them, requiring complete dismantling. The resulting corrosion may result not only in excessive Wear but it frequently causes the relatively movable parts to seize or to be locked and rapidly destroyed during use.

An object of our invention is to prevent deterioration of the type of composition mentioned above and We have found that this may be accomplished by use of certain kinds of carbon black in small quantities. In particular, we have found that certain non-toxic carbon blacks can be satisfactorily employed as oxidation inhibitors. Properly used, these materials will prevent the objectionable deterioration in the greases mentioned above over relatively long periods of time.

In addition to inhibiting oxidation, theparticular types of carbon black referred to above' have a very high absorptive power for mineral oil. They also tend to form stable colloidal or greaselike structures with the oil and because of certain The comparative structure index" properties of various carbon blacks Vare known in the art,'th`ev term structure index being dened by Sweitzer and Goodrich in an article published in Rubber Age for July, 1944, entitled ,The Carbon Spectrum for the RubberCompounder, beginning at page 469 and especially onpage 470. The structure index, which varies considerably with various carbon blacks, is a measure of their oil absorption capacities. Thus acetylene black has a strucy ture index lof 300, compared with ordinary chan-- nel black having an 'index of 100.

Carbon blacks of the type referred to above preferably have a small average particle size and are reticulate and branched in particle structure. The most suitable type have an average particle size ranging vbetween 25 and 50 millimicrons. These blacks have alkaline reactions,-their pH being over 7. Suitable examples are acetylene black which has a particularly high structureindex number as noted above and some of the ner particle channel carbon'blacks with structure in-v dices higher than average.l y y A modified channel black, well knownin the trade for its electrical conductive properties, is prepared by removal of the absorbed oxygen-ated compounds held 'to the surface of the carbon black particles during their preparation from natural gas. The carbon black last mentioned is particularly effective for the present purposes of inhibiting oxidation since it has a high pH value. approximately 9, and an abnormally high structure index of about 200. One example of such a carbon black is the product sold by the Columbian Carbon Company, New York, N. Y., under the brand name Conductex B. Some of its properties are listed in the aforesaid article in Rubber Age. Others of the carbon'v blacks mentioned above which have the requisitepropertiesof high pH, high structure index, etc., are also listed inr v said article.

Although various types of carbon blacks have been employed in greases-in the past including the channel or color blacks, the latter have been seriously objectionable to Workmen because of their extreme staining capacity. For this reason, it is preferred to use only small percentages of the fine particle black in soap thickened lubricants. Hence in the present invention the grease composition is thickened or given its grease structure With soap, the ne particle carbon content, useful for inhibiting oxidation, being kept to a minimum so as to avoid objections due to staining as far as practicable. While the quantities employed are sufficient to darken considerably the color of the grease, they do not cause the grease to become objectionable because of staining. In fact, in some instances the black color` imparted to the grease is desirable. Light colored greases in thin films are frequently almost invisible and this characteristic sometimes makes it dicult for operators of machinery to maintain proper lubrication. There is a tendency frequently to over-lubrication and Waste and the presence of color makes it easier to detect and prevent the use of excessive quantities. On the other hand, there may be danger of failure to lubricate because of the lack of contrast between the unlubricated bearing and one carrying a thin nlm of grease. The black grease film, on the other hand, is readily noticed on shiny bearing metals.

Another factor to be considered in the inhibition of tendencies of lubricants toward oxidation is toxicity. Certain common oxidation inhibitors are very toxic and frequently these toxic metals cause vdermatitis and skin eruptions of Various kinds, to those who handle greases. Carbon blacks of the type used herein are non-toxic and do not give rise to such difficulties.

The following examples show the effect of carbon blacks of the general character listed above as they affect the oxidation resistance of greases.

Example 1 A grease having the following formula was prepared:

15.00% hydrogenated fish oil of 54 titre and 57 C. melting point 5.00% hydrogenated fatty acids 2.40% NaOI-I 0.70% hydrated lime 77.86% phenol extracted low cold test mineral oil Bomb Life, Pressure Drop (in oxygen ab- Grease sorbed), in lbs./in.2

- Hrs Hrs Hrs. Hrs. Grease described 111 Example l 38 40 42 42 Same-i-lffo Carbon black 1 48 50 52 54 Same+2% Carbon black 1 128 172 232 268 Same+4% Carbon black l.. 110 182 252 318 Y I Moded channel black, with pH of about 9, structure index 200.

Eample 2 Another grease tested had the following composition:

15 %v lithium stearate 0.5% aluminum stearate 0.5% zinc naphthenate 84.0% di-2-ethy1 hexyl sebacate This grease was subjected to the standard Norma-Hoffman Bomb test in comparison with a similar compound to which Was added 4% of the ne particle carbon black described above as having a high pH (about 9) and high structure index (200). The results are indicated in the following table:

Bomb Life, Pressure Drop in lbs./in.'-

Hrs. Hrs. Hrs. Hrs. Grease ol Example 2 24 30 44 Same-l-4% Black 738+ Ezvample 3 A third example consisted of a standard commercially available mixed soda-calcium base grease employed for ball and roller bearing lubrication. This grease has approximately the following composition:

This grease was tested in comparison with the same compound having added thereto 4% of the carbon black of high pH value and high structure index (200) described above, and the Norma- Hoifman test results are indicated in the following table:

Bomb Life, Pressure Drop in lbs/ini Hrs. Hrs. H'rs H rs. Soda-calcium base grease 26 44 Same-|-4.0% Carbon black 50 106 124-!- The accompanying drawing shows the high temperature-pressure viscosity of the two lubricants just described. It v/ill be noted that the viscosity drops off much less rapidly at higher temperature in the case of the lubricant containing carbon black. On the other hand, at normal temperature the carbon black composition has a lower viscosity than the standard lubricant without the carbon black, an effect which is surprising. Both of these characteristics are highly desirable.

While we have referred specifically to the use of the particular modified channel carbon black having a pI-I of about 9 and a structure index of about 200, it will be understood that our invention is not limited. thereto.

In general, carbon blacks having a pH of more than 7.0, particle size between 20 to 100 millimicrons average, and higher than average structure index are suitable. Thus thev structure index should be above 100, preferably of the order of about 200 or even higher. The quantity of black used will be varied, depending upon the tendency of the grease towards oxidation. As a rule it will be at least 1.0% and not more than 10%, based on the weight of the finished lubricant, but in many cases a smaller quantity, such as 0.3% or 0.5% will be sufficient. Acetylene black is useful though not quite as eiective as the particular modified channel black mentioned above.

It will further be understood that various soap compounds may be used in lieu of the lime, sodium, lithium, aluminum, and zinc soaps specifically mentioned in the foregoing examples as Will be obvious to those skilled in the art. The soap content may vary within the usual limits, e. g. 5 to 30% by Weight, based on the total composition.

We claim:

A lubricating composition consisting essentially of 66 to 94% mineral lubricating oil, 5 to 30% of a metal soap selected from the group consisting of the soaps of fats and fatty acids, f y

and 2 to 4% of a modified channel kcarbon black having-a pH of about 9, a particle size from 20 to 100 millmicrons, and a structure 'index of about 200.

rARNOLD J. Mo-RWAY.

ALAN BEERBOWER.

REFERENCES CITED The following references are of record in the file of this patent: f

UNITED STATES PATENTS dian Chem. Met., vol. 17, May 1933, p. 95,.

Industrial Carbon, by Mantell, published by Van Nostrand Co., New York, 1928, p. 229.

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