US2453153A - Lubricating grease - Google Patents

Description

iNov. 9,'1948. A. J. MoRwAY ET Ax.

LUBRICATING GREASE Filed Deo. 6, 1947 APDAQENT wsosm-Y (Dmsas) Patented Nov; 9, 194,8

LUBRICATING GREASE Arnold J. Morway,

Clark Township,

Union County, and John C. Zimmer, Union, N. J., assignors to Standard Oil Development Company, a corporation of Delaware Application December 6, 1947, Serial No. 790,219

14 Claims.

This invention relates to lubricants, and in particular to highly Viscous lubricating compositions, specifically lubricating greases, having definite yield values. The accompanying drawing represents a lgraphical comparison of the relation of viscosity with temperature of two compositions having the same consistency (penetration) at 77 F., one composition, indicated at A, prepared according to the present invention and the other composition, indicated at B, being a prior art composition consisting essentially of a sodium soap and mineral oil. The comparative uniformityl of composition A over a Wide temperature range is readily apparent.

In lthe past, lubricating greases, solid and semi-solid, have usually been prepared by employing various metal soaps as thickeners, incorporating them in mineral oils either as pseudo solutions or as fine dispersions. These grease compositions have in general shown a thinning out or liquefaction or marked tendency toward 'liquefaction upon heating. At high temperatures, such compositions have shown the effect of the swelling of the soap in the oil, causing considerable thickening with unpredictable viscosity changes, varying with different soaps, untilthe melting point of the soap was reached, at which point the lubricant approached the Viscosity of the oil constituent.

In prior art grease compositions, where soap was used as the thickener, apparent viscosity was usually found to be dependent upon the viscosity of the mineral oil and consistency was dependent upon the amount and type of soap. It was generally found, moreover, that the viscosity of the grease decreased with increasing shear rates and at high rates of shear the viscosity approached that of the mineral oil base, even at moderate temperatures, and more so at higher temperatures. It has heretofore been diflicult or impossible to make a vsingle grease composi- 'tlon Which would be suitable for use over a relatively wide temperature range because of the unpredictable viscosity behavior. This problem has been an active one but until the present invention, no satisfactory solution appears to have been proposed. In grease compositions of the present invention, unique and desirable viscosity characteristics are obtained.

For many years, certain carbon blacks have been incorporated in mineral oils and other viscous oily materials for various purposes. It has been recognized that for most purposes the most desirable carbon blacks are those which impart 2 an intense black hue with a minimum thickening effect. Printing inks, which are essentially oily suspensions of carbon black demand a very intense color, as do other analogous compositions. In the present invention, acetylene black, which vhas a dull greyish appearance and therefore, undesirable for the above uses, has been found to have unexpected and pronounced thickening properties in rened mineral lubricating oils and to be particularly suitable for the preparation of lubricating grease compositions having excellent temperature-consistency properties. In the preparation of lubricating grease or grease-like compositions with acetylene black, from 3 to 20% by Weight of the black may be employed. Particularly desirable greases are 'prepared by incorporating 5 to 18% by Weight ofthe acetylene black in mineral oils of the lubricating oil range. The amounts of acetylene black required to prepare grease compositions of a given body and consistency are much smaller than the amounts necessary with other types of carbon black. For example, a grease containing only 11% acetylene black in mineral oil has the same consistency, i. e. resistance to penetration, as a grease composition prepared with 18% of ordinary channel black in the same oil. In addition, the other required properties of the grease are superior, in the case of that prepared from acetylene black. In these lubricating grease compositions, the mineral oil constituent may be derived from a paraffin, naphthene or mixed base crude and may have a viscosity ranging from that of a light mineral oil of about 50 Saybolt Universal seconds at F. to that of a heavy cylinder oil of viscosity of about v1000 Saybolt Universal seconds at 210 F.

In preparing the lubricating grease or greaselike compositions containing acetylene black and mineral oils, acetylene black has an additional practical advantage. It is only necessary to mix the acetylene black into the oil by ordinary stirring means. The compositions thus prepared from acetylene black and mineral oil have a smooth viscous consistency and a relatively uniform distribution of the black throughout the oil. In order to prepare lubricating compositions from other carbon blacks, such as channel black, a high degree of mechanical Working of the black in the oil is necessary, as for example, passage of the mixture through a paint mill. Furthermore, with the compositions prepared from these blacks, it is almost or quite kimpossible to obtain as uniform distribution of the black in the oil as in the case of 4acetylene black.

Acetylene black is also found to be an advantageous constituent of lubricating compositions on account of the relative ease of removal of the grease composition from hands and clothing. In contrast. to the channel blacks, for example, which have intense color and are very diicult to remove from skin and clothing, the acetylene black has an important and practical advantage.

Example 1 In the preparation of a lubricating composition containing 12% by Weight of acetylene black and 88% of a naphthene base lubricating oil having la viscosity of 'l0 Saybolt Universal seconds at 210 F. a small portion of the oilv Was initially added to a typical grease kettle equipped with side-scraping paddles and the acetylene bla-ck was added. The speed of the paddles Was controlled so as to Qbviateloss of" the added carbon. The balance of the y'oil' was added in small portions tothe mass undergoing agitation landwas worked gradually 'into-the mixture to prevent lumping of thefblac'k. The composition thus prepared had a smooth paste consistency and a iirmgrease-like appearance, an A. S. T. M. penetration (worked) at 77 of A300, and under the conditions-of test for the A.. S. T. M'. dropping point did not `show a melting point. 1

For purposes of comparison a sodium soap vgreasewas prepared' having the same consisten-cy as the above grease at 77F.'- This composition was prepared from the following ingredients:

Mineral lubricating oil (Coastal oil of .55

Say'fbolt seconds viscosity at.210 F.) 71.7.5 -Phenyl alpha naphthylamine 1 '11o prepare this grease, the rapeseedoil, sodium A"sni-lior1a-tes and ione-third Joi the-mineral .oil were placedin a grease kettle and heated to 150 F. The caustic soda was then thoroughly stirredin as` a '30% aqueous'solution and the mixture'was 'heatedfto 225 F. untilsubstantially all the Water had been removed. The balance lof the mineral oil was vadded and the temperature-.raised to 500 after Which the source of' heat was removed and-fthefg-rease was allowedto cool to 275 F. while being paddle stirred. The phenyl alpha naphthylaminewas then added and the grease was Worked and-cooled until its temperature Was lowered Ito 200ov Fr where it was then ltered and packaged. This grease had anA.-S. T. penetration of SOOandanYA. S. T. Mfdropping point of 440 F. i

.As suggested above, in the drawing the two compositions mentioned above are compared graphically as tothevariation of their apparent viscosities Vwith temperature at constant rate `of shear; graph A relating to the acetylene black `composition of Example 1 and graph B relating to thelsodium soap composition described above. In this graphical analysis, presented on 'a semi- 'logarithmic scale, apparent viscosity in poises is plotted against temperature. Apparent viscosity was measured by means vof a pressure viscosirneter.

Inspection of the graphs shows that over the `temperature range of 150 F. to 340 F. the apparent viscosity l:of the `grease composition of the from l5 to 10 poises, whereas over the same temperature range, the apparent viscosity of the sodium soap grease varies from 33 to a 10W point of about 8 poises and then increases to a high of about 80 poises.

The abrupt fluctuations occurring in the soap thickened .lubricant are considered toi be caused by solvation and swelling of the soap in oil With rising temperature resulting in a change in grease structure which in turn causes a sudden increase in apparent viscosity. In the composition of the present invention, no apparent changes occur in the grease structure with increasing temperature. Thus, the composition of the present invention is a smooth. uniform product with good lubricating properties. Changes in grease structure from a smooth vconsistency to a fibrous ropey material such .as occur with typical soap thickened greases result in lubrication failures and this is undesirable.

'f Example 2 Another composition fW-as preparedv generally similar to that of Example 1. In this -case ,,1 l% by weight of acetylene black. `was thoroughly mixed in 89% of a naphthene base lubricating oil having aviscosity oi Saybolt Universal seconds at 210 F. The composition thus prepared hadan A. S. Tali/l. penetration .(Worked). at '77 F., .of 286 and under the conditions for the A. S. T. Mi .dropping .point did not show a melting point. f

Example 3 1.8 %l ci a rcommonly available channel black-Was dispersed in the same napht'hene base lubricating oil as used in Example 2'. In dispersing thismaterial to obtain maximum body, itwlas necessary toA employ a paint mill, the mixture beingPaSSed severaltimes through the mill. The composition Vhad an A. S. T. M. penetration (Worked) Aat' 77 F..oi '292 and there was no Vapparent meltinglpoint.

To compare the oxidation stability of compositions thickened respectively with channelbl'aok and with acetylene black, prepared as described in vExamples Zand 3, portions of each were sub'- jectedlto the standard Norma-HohmanniBomb Oxidation Test.. In this test, vthe composition is subjected to oxygen under pressure ofll'ilbs. per sq. inch at l210" FklandA the time requiredifor'a five pound'drop in oxygen pressurei'snotedl "I'he following results were obtained:

polyhydric alcoholyparticularly of -a glycolmay be employed. The use of polybutene in'combi-n-'aition with a metliacrylic acidl ester poly-rnerfis particularlyl advantageous. These. thickening agents are usually incorporated in -the-lgrease'iby adding an oil solution of the*thickening agents to the grease and thoroughly mixing.- Rubber latex or swollen gum rubber, with yor without-a stabilizer v-oroxidationinhibitor Aorr an ioil solution of natural or synthetic rubber --mayf also be :employed in the composition. *The Vpolymers present in these compositions have little eiect in general on the Vconsistency but impart adhesiveness and stringiness to lubricants particularly desirable for lubricants employed in connection Vwith reciprocating or other such mechanisms .pressure lubrication purposes may be prepared by compounding mineral oils, acetylene black and extreme pressure additives of either the oilsolub-le or oil-insoluble type. Thuswhen 5% to 15% by weight of acetylene black is :blended with a mineral oil to give a grease-like structure, 0.5% to of any of the oil-insoluble, high temperature, extreme pressure additives such as phosphorus sesquisulphide, powdered lead', free sulfur, zinc oxide, titanium oxide and graphite may be incorporated in the mass to `prepare highly desirable extreme pressure lubricants. As an illustration in this connection the following example is presented. Rubber or other polymeric thickeners may be added, as suggested above.

Ercamplel 4 8 parts by weight of acetylene black was mixed yinto 92 parts by weight of a steam refined cylin- "deroil lof'Mid-continent'` origin of 180 Saybolt Universal seconds viscosity at 210 F. (lubricant A). The acetylene carbon black was dispersed in* the mineral oil by simple mixing in a grease lkettle to prepare a smooth, semi-fluid mass. To

'(P4`S3) and thoroughly mixed again in the grease kettle.' The resultant product (lubricant B) was a semi-uid, string?, cohesive and adhesive product. y This product had a small but definite yield value and under low shearing stresses was fluid, Abut upon removal of the stress the product reset y to a nonfluid mass. Under the conditions of the Almen test, the following data were obtained:

Thus, the extreme pressure additives, such as free sulfur, phosphorus sesqu'isuliide and molybdenum sulfide are eiective in smallerjconcentrations inl compositions prepared mainly from mineral oils and acetylene black than in compositions prepared mainly from mineral oils and soaps;

As ,additional examples of the invention,` the following may be cited:

Example 5 16 parts by weight .of acetylene black were vmixed with 84 parts of a high quality, paraflin base lubricating oil having a viscosity of about 80 S. S. U. at 210 F., and a viscosity index of 103. The resulting grease was of excellent texture,

vstable against oil separation and of firm solid consistency.

Eample 6 Example 7 For a general comparison between graphite `and acetylene black, 16 parts by'weight'of graphite were added to 84 parts by'weight of a lubricating oilidentical with that of Example 6. A suspension was produced by mixing but theigraphite rapidly settled out of the'oil, leavingV thepper three-fourths of the volume 'as afsubstantially clear liquid oil and the bottomfone-fourth a thick precipitate of graphite within a few minutes. The composition had no grease-like'structure or texture, although the freshly mixedcomposition was quite thick.

Example 8 To determine the utility ofacetylene blackmas Shock Loading Almen Test Lubricant Graduamoading Pin Conditionv Wtgflged Pin Condition v (pounds Gamed) (pounds carried) 1 A 4, 000 Sheared 2, 000 Sheared. :B 15,000 Excellent (like 15,000 EXCQII'QB (like i f. original). original).

Of the oil-soluble extreme pressure additives a thickener in oils of other than mineral' base lead oleate and lead naphthenate vare the most .commonly employed, and usually in amounts between 5% and 20% by weight. In order to impart a relatively high load-carrying ability, such other extreme pressure agents as the sulfurized, chlorinated or sulfo-chlorinated mineral oil, chlo- `rime-containing suldes, polysulfides, xanthates, "mercaptans, sulfurized or .sulfo-chlorinated fatty oil, esters, olens, diolens, chlorinated waxes or chlorinated aromatic hydrocarbons, and amines, may be blended in the mineral oil-carbon black composition.

In these/compositions the extreme pressure additives are mixed directly with the acetylene black and mineral oil. In the case of mineral oils thicken'ed with soaps, on the other hand, preliminary treatment of the :chemically active compounds employed as the extreme pressure additive is gen- -erally necessary to 'reduce chemical reaction vbetween the additive and the soap constituent. 75

origin, 16 parts by weight of acetylene .black were added to 84 parts of castor oil and thoroughly mixed. The resulting composition was `a soft but smooth and uniform grease of good.y appearance and good physical stability. No noticeabldoil separation occurred after standing for 30 days. The grease was considerably softer in consistency, however, than that of Example 5 .which vcontained the same amount of acetylene black.

Example 9 tially of 11% acetylene black dispersed in naph thenic lubricating oil of 70 Saybolt Universal seconds at 210 F. and 0.1 to 2% of polybutene.

12. A high temperature extreme pressure semisolid to solid lubricating quasi composition consisting essentially of lubricating oil thickened to a greasedike consistency and body with 5 to 15% by weight, based on the ltotal composition, of acetylene carbon black, said grease also contain ing about 0.5 to 10% by weight of an oil insoluble phosphorus sulfide finely dispersed therein as a high temperature extreme pressure agent.

13. Composition as in claim 12 wherein said phosphorus sulfide is phosphorus sesquisulde.

14. Composition as in claim 12 to which is added a small amount of a tacky relatively inert organic lpolymer ras a stringness agent.

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

UNITED STATES PATENTS Number Name Date 1,880,987 Silhavy Cot. 4, 1932 2,349,058 Swenson May 16, 1944 2,356,365 Wright Aug. 22, 1944 OTHER REFERENCES Uses and Applications of Chemicals and Related Materials, 1939, page 148, Thomas C'. Gregory, Reinhold-Pub. Corp., New York, N. Y. (Copy in Division 64.) n

Canadian Chem. & Met., Vol. 17, May 1933, Article entitled, Acetylene Carbon Black by Charles Kaufmann, pages 93 to 95.

Petroleum Rener, March 1944, Article entitled, Carbon Black by J. F. Gallie, page 106.'

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