US2929782A - Physical combination of calcium and lithium hydroxy stearates for forming greases - Google Patents

Description

March 22, 1960 WORKED PENETRATION L. W. SPROULE ET AL PHYSICAL COMBINATION OF CALCIUM AND LITHIUM HYDROXY STEARATES FOR FORMING GREASES Filed July 17,- 1957 MIXTURE PREPARED BY CO-SAPONIFICATION LITHIUM SOAP CALCIUM SOAP Lorne W. Sproule Warren C. Poflenden B fa.M

IOO

Inventors Attorney ilnited rates PHYSICAL COMBINATIUN 6F CALCIUM AND LITHIUM HYDROXY STEARATES FOR FORM- ING GREASES Lorne W. Sproule, Sarnia, Lamhton, Ontario, and Warren C. Pattenden, Courtright, Lambton, Ontario, (1am ada, assignors to Essa Research and Engineering Com pany, a corporation of Delaware Application July 17, 1957, Serial No. 672,432 3 Claims. Cl. 252- The present invention is concerned with improved lubricating greases based on the use of a thickening amount of a novel physical combination of calcium and lithium 12-hydroxy stearates.

This application is a continuation-impart of Serial No. 316,302, Calcium-Lithium Hydroxy Fatty Acid Soap Greases, filed October 22, 1952, bythe present inventors and now abandoned.

In brief compass, this invention proposes a lubricating grease composition comprising a lubricating oil thickened with a grease thickener formed at a temperature in the range of 275 to 315 F. by saponification of 12-hydroxy stearic acid with a base comprising about 20% lithium hydroxide and 80% calcium hydroxide, so that the calcium and lithium soaps are simultaneously formed in a proper ratio to obtain a novel physical combination of the two soaps having properties unexpectedly different from the known properties of the individual soaps. This new physical combination of the soaps is an excellent grease thickener in itself, but it can also be combined with other conventional grease thickening soaps, especially with additional amounts of lithium l2-hydroxy stearate.

As the art of grease manufacturing has become more sophisticated, it has been realized that greases having greatly improved properties over the simple soap greases could be prepared by judicious combinations of dilferent basic materials, different soaps of perhaps different chain lengths, configuration and substituent groups, and/or salts, either inorganic salts or salts of low molecular weight carboxylic acids. Quite often it has been found that such combinations of materials unexpectedly result in new types of thickeners, usually broadly termed complexes, which account for the improved properties of the grease products. These complexes often have properties, such as X-ray diifraction patterns, inconsistent with a mere physical blend of the components and can be of many types. It is believed, for example, that the complex formed between a C or higher carboxylic acid soap and calcium acetate at a temperature above 425 F. is of the ionic type, and results in a new crystalline soap structure. Chemical complexes of various natures are believed to be formed between low molecular weight dicar'boxylic acid salts and soaps.

The art of grease manufacture has not evolved to a point where these complexes are so well known that the tailor making of a product involves the simple selection of known ingredients. Extensive experimentation and development are still called for, and quite often unexpected results are obtained.

Mixed calcium and lithium stearate greases have been known to the art. In order to make a satisfactory grease, the lithium component must be present in the thickener in an amount in excess of about wt. percent, which makes the grease excessively expensive. These greases also are deficient in their mechanical stability and oxidation resistance.

These greases are valued for their high dropping points. Their water resistance leaves something to be desired, the conventional calcium greases usually giving better service in the presence of water. In order to use a minimum amount of thickener in a grease the lithium soaps must be prepared at a temperature above 400 F.

Ca l2-hydroxy stearate greases have also been disclosed in the art, and are valued because they do not have to be plasticized with water. Their dropping points, however, do not exceed 290 F., and they must be prepared at relatively low temperatures in the order of 275 F. It has also been found, and this is believed to be un-' appreciative by the art, that calcium 12-hydroxy stearate greases are very water sensitive. They will breakdown and fiuidize in the presence of more than 0.4 wt. percent water when worked at temperatures above about 190 F. This is objectionable, for example, in equipment such as food can closing units wherein the grease must lubricate at 200 F. in the presence of condensed steam.

From this knowledge of the art, it is believed that in the present invention, it is unexpected that a superior grease thickener comprising lithium and calcium soaps in a novel physical combination could be prepared at a relatively low temperature using only 20 Wt. percent lithium through the use of l2-hydroxy stearic acid in" place of the unsubstituted acids. It has also been found that this novel physical combination permits a lesser amount of total soap to be used in forming the grease. This use of such a minor amount of lithium in the thickerror, the use of less thickener, and the lower manufacturing temperature, are very important from an economic standpoint, as will be appreciated by those skilled in the art.

One unexpected feature of this invention is that the water sensitivity of the calcium 12-hydroxy stearate grease is completely overcome by modifying it by physically combining it with a minor amount of the lithium soap. It would have been expected that the lithium soap would not improve the water sensitivity of the calcium soap, because the latter is generally considered to be superior in water resistance. For example, lithium oleate will practically dissolve in water, while calcium oleate will not.

Another unexpected feature of this invention is that this novel physical combination can be prepared at mod erate temperatures in the range of 275-315 F. This is above the maximum temperature permissible in the manufacture of the calcium soaps, and well below thehigh temperatures, 400 F. necessary to form the lithium soaps. It would have been expected that, at this lower temperature, the lithium soap molecules would not have been sufiiciently mobile to enter into a physical combination.

It must be appreciated that this new physical combina tion of the soaps cannot be arrived at by simple blending of the individual soaps, whether or not this is followed by heating. An unsatisfactory product is obtained by simply blending the components. The two soaps must be simultaneously formed by a co-saponification of the 12-l1ydroxy stearic acid at a temperature in the range of 275-315 F. in order to achieve the desired physical combination. The two saponifying agents can be added simultaneously to the acid solution, or one can be added after the other, so as the saponification because of the first added agent is substantially complete. The

Lithium l2-hydroxy stearate greases have also been 0 known to the art, but are also excessively expensive.

'two saponifying agents are preferably blended in plant scale operations with the acid solution within 10 minutes of each other.

lithium soap content, although to permit a little latitude this is given as being in the range of 18 to 22% in the attached claims. Greater amounts of lithium soap do' not cause the formation of further amounts of the physical combination and the thickener partakes of the properties of a blend between the 20% lithium/ 80% calcium physical combination, and the remaining lithium soap that is present. If a lesser amount of lithium soap is used, say 15 wt. percent, the calcium 12-hydroxy stearate is not modified sufficiently to overcome the above described water sensitivity.

This invention will become clear from the following examples and description with reference to the drawing attached to and forming a part of this specification.

The drawing is a graphical presentation of the relation ship between the calcium and lithium ratio of the soap and the worked penetration of the grease product, at a total soap content of wt. percent. This graph demonstrates the formation of thenovel physical combination of snaps of this invention.

Greases in accordance with the present invention can be prepared as follows: IZ-hydroxy stearic acid or an equivalent material is charged to a grease kettle and heated therein to about 180 -200 F., preferably in the presence of an equal weight of lubricating oil, while stirring. The lime is then added, preferably in the form of a water slurry while heating and mixing are continued. After about 1 3-10 minutes, the lithium hydroxide is added, usually as an aqueous solution. The mixture is then further heated at about 275 to 315 5., preferably 300-310 F., until dehydration is complete, which can require about 3-6 hours. If desired, further lubricating oil is added as the. grease thickens in the course of the dehydration process.

After dehydration is complete, the kettle contents are cooled while stirring. Oil is added while cooling progresses until the desired soap content is reached. It has been found that this soap content need not exceed wt. percent and is usually below 10 wt. percent for a grease based on the novel physical combination of soaps alone.

After oiling the grease back, the grease can be finished by working or milling, as in a Manton-Gaulin homogenizer or Morehouse mill. After or during milling, further oil can be added, if desired, to bring the worked penetration up to the final desired value.

As mentioned before, the new physical combination of the calcium and lithium 12-hydroxy stearates can be used in combinations with other conventional grease thickeners. These can be simply blended with the novel grease thickener of this invention, followed by heating if desired. It is especially preferred to blend thecombination snaps of this invention with additional amounts, in the range of 15 to wt. percent, of lithium 12-hydroxy stearate to obtain a grease especially suitable for the lubrication of railroad car wheel roller bearings. This additional amount of lithium soap in the blend can conveniently be provided by using an excess of the lithium saponifying agent during the co-saponification step, or by blending the physical combination of soaps of this invention with additional lithium soap.

EXAMPLE 1 A grease containing less than 12 wt. percent of mixed lithium-calcium 12-hydroxy stearate soap thickener having a lithium to calcium soap ratio of 20:80 was prepared a slurry in pounds of water. About 5 minutes later the 4 was checked for free alkali and found to be 0.2%. This was considered satisfactory. After heating at 290-300 F. for about 5 hours, the steam was turned oit and the kettle contents allowed to cool. A test on the grease for water content at this stage was negative. While cooling from 300 F. to about 200 F'., 1181 pounds of mineral oil were slowly added, along with 10 pounds of phenylalpha-naphthylamine dissolved in 10 pounds of oil. The finished grease was drawn from the mixer into containers at 190 F. This grease required no milling. The composition and properties of the grease are summarized in "Table I.

Table I Formula, percent by weight:

12-hydroxy stearic acid 10.8 Lithium hydroxide monohydrate 0.36 Hydrated lime 1.26 Mineral oil 1 87.08 Phenyl-alpha-naphthylamine 0.5

Inspections:

Percent soap:

As Li IZ-hydroxy stearate 2.3 As Ca 12-hydroxy stearate Q; i 9.3 Free acid, percent oleic 0.28 Excess alkali, percent LiOHl-I O 0.1 Worked penetration, 77 F 275 Mechanical stability, penetration after 10,000

strokes in fine hole Worker 295/ F. Water absorption (mixer method) at F.: No. of ccs. of water absorbed 11 (Consistency good) ASTM dropping point, F. 318 Wheel hearing test, 6 hrs. at 220 F. and

60 mph:

Gms. of grease leakage 1.4 Over-all rating Good Spindle test, hrs. at 250 F. and 10,000 rpm. 1100 App. viscosity at 100 SPC. 1Z

Shear (Strokes):

77 F. 180 130 F 68 F. 38 200 F. 30 225 F. 23 250 F. 24 275 F. 27

300 F. 9.5 Bleeding-percent 'oil loss after 100 hrs. at 225 Viscosity 60 SUS at 210 F., and a. viscosity index or 50.

It will be noted that this grease, in spite of its low total soap content and very low lithium soap content, has a satisfactory dropping point above 300 F.', excellent working properties, very high water resistance and excellent bearing performance.

t... EXAMPLE 2 Four additional greases were prepared besides grease A of Example 1. The three lithium containing greases, B, C, and D were prepared in a manner similar to that of Example 1 at a saponification and dehydration temperature of about 300-310 F. Grease E, a 100% calcium grease, was prepared by melting the acid in four times its weight of mineral oil at 180 F. A water slurry of the lime was added in sight excess, and the mixture was then stirred and dehydrated at about 270 F., the maximum permissible temperature. This required about 14 hours.

when dehydration was complete, further oil was added to adjust the soap content. The oil used for these greases 6 ing properties. When the calcium 12-hydroxy stearate 1s modified, however, in accordance with this invention,

Table H the properties of the new crystalline structure are such as to yield fibers having good properties. Grease B o D A n 5 EXAMPLE 3 Percent Lithium soap in thick Nine additional greases were prepared having a total ener 100 40 20 0 Percent mp after oiling back and 4 soap content of 10 wt. percent, 1n a base oil similar to w i g g 153 M3 12 5 1L6 that of Example 1. Products F and G, consisting mostor e pene ra iona 77 328 280 280 275 ASTM Dropping Point o F u 331 318 318 1y of the calcium soap, were of necess1ty prepared at a ASF mi ig somewhat lower temperature. Table III gives the results 0 greaseconta ing5wt.percent watermixed atmm tempew and inspections of the grease products F through N. Ag?? E 3 The attached drawing graphically illustrates by the i. icro-pene ration at"" F. after heating at Fund'r 50 1 dashed line the relat1onsh1p between the llthlllm calcium lbs/sq. in. nitrogen pressure: 9 ratio of the greases, and the worked penetration of these After 31mm gg Fluid grease products. The solid line on the graph illustrates Aiterfihours as the worked penetration of greases having comparable lithium-calcium ratios, but prepared by simple blending The data of Table II show the efiect of substituting of the two soaps rather than by co-saponification.

Table III In oo'n' I]; K L M N Percent of Soap which is lithiumG) 0 5 12 20 23 40 60 80 100 Worked Penetration 280 284 274 279 281 318 336 373 400 Dropping Point 290 292 288 318 320 327 342 364 373 Percent Change in Penetration after 16 hours at 200 F. under 5) lbs. nitrogen pressure (grease mixed with 5% water)- 168 128 71 0 1 F prepared at 265 F.; G prepared at 280 F.; all other products made at 300310 F. 9 Balance is calcium.

a minor portion of lithium for the al ium in the hy- Table III and the drawing clearly illustrate thatthere droxy stearate greases. Grease B requires substantially more than 15.3% soap in order to obtain a grease having a worked penetration of about 280. The amount of soap necessary would be less if grease B had been prepared at a higher temperature of about 400 F.

Greases A and D illustrate the novel physical combination of soaps of this invention, and show that only 12.5 Wt. percent or less soap is needed to achieve the desired penetration. Grease C illustrates this physical combination of soaps with an additional 20% thickener comprising of lithium 12-hydroxy stearate.

For comparison, a grease prepared with stearic acid, rather than the hydroxy acid, having a lithium-calcium ratio of /60 and a total soap content of 15 wt. per cent, has a worked penetration of 395. Stearic acid is, therefore, not a suitable ingredient in this type of grease prepared at 275 315 F.

The last two inspections of Table II give the results of testing the water sensitivity of the, greases. Grease A was substantially unaffected by the water, while the 100% calcium grease rapidly fluidized.

A calcium 12-hydroxy stearic grease hardens as the water content decreases during the dehydration step. Thus, a calcium 12-hydroxy stearic grease containing 20 wt. percent soap and 0.5 wt. percent water, while being dehydrated at 260 F., is semi-fluid. When the water content is reduced to 0.05%, the Work penetration is 142. The effect of the Water in the ea in iZ-hydror-iy stearic grease is reversible about 190-200 F. For eX- ample, if water is mixed With a calcium IZ-hydroxy stearic grease at 200 F., it reverts to a fluid product. When, however, 20% of the total soap of the grease is formed from lithium 12-hydroxy stearate by cosaponification in the manner of this invention, the grease product does not becomefluid when heated in the presence of water above 200 F. While the reason for this is not certain, it is believed that above 200 F. calcium l2-hydroxy stearate exists as a monohydrate. The geometry of this monohydrate crystal is probably such as to form poor fibers having inferior grease thickenis a new type of structure, or new physical combination, formed by the lithium and calcium 12-hydroxy stearic soaps when they are in the ratio of 20% lithiumiand calcium, and when they are prepared by co-saponification.

The graph shows the sharp change in the worked penetration of the grease products that occurs when the lithium content reaches about 20%. This is indicative of the formation of the novel physical combination of soaps of this invention.

Examples 2 and 3 together show the remarkable water insensitivity imparted to the calcium 12-hydroxy stearate by properly physically combining it with about 20% of the lithium soap, and also clearly show that the full benefits of this invention are, not obtained by using less than about 20% of the lithiumsoap.

EXAMPLE 4 Table IV Grease.. L M

Worked penetration at 77 F 290 295 Drawing Point, "F 288 288 ASTM Micro-penetration at 77 F. of grease containing 5% water, percent increase 17 16 The attached drawing illustrates the results obtained by blending different amounts of the soaps to obtain several more greases. Comparison ofthe two lines shows that a product having different physical properties is pre pared by 'cos'aponificationl .Thisexample shows that the novel physical combination of soaps, according to this invention, cannot be obtained by simple blending of the components,but that it must be formed by co-sapouification at 275 3l5 F.

EXAMPLE .5

When the amount of lithium saponifying agent used is in excess of the natural ratio of 20%, the excess lithium soap is simply blended with physical combination of soaps. This is illustrated by the following: Two greases were prepared at 300 F., similar to greases F and N of Table 111, each having a total soap content of wt. percent. These twogreases, one having 100% lithium soap and the other lithium and 80% calcium soaps, were then blended at about 100 F. to achieve a grease wherein the thickener comprised 40% lithium soap and 60% calcium soaps. This blend contained 10 wt. percent of total soap and had a dropping point of 332 F. and a worked penetration at 77 F. of 293. Itcan then be seen that this blend had properties substantially equivalent or slightly superior to the 'cosaponified greases, grease C of Table II and grease K of Table III.

This example shows that grease products containing the new physical combination of soaps of this invention, but containing more than 20% lithium, can be prepared by either cosaponification of the acid using a base containing the desired ratio of lithium to calcium, or by blending the desired additional amount of lithium soap with the physical combination of soaps after it has been formed by co-saponification.

EXAMPLE 6 Pounds l2-hydroxy stearic acid 237 Mineral oil charged to mixer with .fatty acid 360 Lime 28 Lithium hydroxide 8 Balance of mineral oil 2089 At 170 F., the following materials were added to impart extreme pressure characteristics to the grease:

Pounds Chlorinated paraflin wax containing 40% chlorine- I 60 Sulfurized sperm oil 180 Lead naphthenate (containing about 30% lead as PbO) 37.5

The mineral oil used was a mixture of two low cold test mineral oil distillates blended to give a viscosity at 210 F. of 110 SUS. One oil in the blend had a viscosity at 210 F. of 170/190 SUS, while the other oil had a viscosity at 210 F. of 53/57 SUS. The composition and characteristics of this grease are summarized below.

Composition, percent by weight:

IZ-hydroxyv stearic acid 7,90 Lithium hydroxide 0.27 Hydrated lime 0.94 Distillate 170/190 57.00 Distillate 53/57 24.64 Chlorinated wax (40% Cl) 2.00 Lead naphthenate 1.25

Sulfurizcd sperm oil 6.00

' invention.

Inspections:

Mineral oil viscosity at 210 F., SUS Worked penetration 305 Dropping point, F. "i 312 Timken O.K. load (lbs) 43 Bleeding testl: percent oil loss-100 hrs. at

225 F. 3.9 Water wash test at FF: percent grease loss 12 1 grams of grease in a 28 mesh galvanized cone. 2 AN-G. 15 specification.

Conventional animal, vegetable, mineral or synthetic oils can be used to form the grease compositions of this Examples of the latter are di2-ethyl hexyl sebacate, silicone oils, phosphonates, and complex synthetic esters formed from alcohols, dicarboxylic acids and glycols. referably the oils used have a viscosity in the range of 10 to 200 SSU at 210 F. and a viscosity index in the range of 30 to 140. It is preferred to use 12- hydroxy stearic acid as an initial ingredient, but equivalent materials that yield the acid under the saponification conditions can also be used. For example, esters of the acid that yield alcohols boiling above 315 F. can be used as a source of the acid. The total soap content of the greases of this invention can range from 5 to 15 wt. percent, and the physical combination of soaps can cornprise from 75 to 100% of the grease thickener. The preferred grease compositions of this invention have a dropping point above 320 F. and a worked penetration in the range of 300 to 360.

Having described this invention, what is sought to be protected by Letters Patent is succinctly set forth in the following claims. 7

What is claimed is:

1. A lubricating grease comprising a major amount of mineral lubricating oil'and a grease thickening amount of a mixed-metal thickener prepared by co-saponifying in said lubricating oil 12-hydroxy stearic acid with lithium base and calcium base, heating to a temperature of 275 to 315 F. to dehydrate, and cooling to form said grease, wherein the proportion of lithium to calcium base is such that said mixed-metal thickener consists of 18 to 22 wt. percent lithium 12-hydroxy stearate and 82 to 78 Wt. percent of calcium 12-hydroxy stearate.

2. A lubricating grease comprising a major amount of mineral lubricating oil and a grease thickening amount of a soap thickener to forma final grease wherein 15 to 25% of the total soap present is lithium 12-hydroxy stearate and the remainder of said soap is mixed lithiumcalcium 12-hydroxy stearate which is prepared by cosaponifying in a mineral lubricating oil IZ-hydroxy stearic acid with lithium and calcium hydroxide, heating to a temperature of 275 to 315 F. to dehydrate to thereby form a mixed calcium-lithium 12-hydroxy stearate grease, the proportion of lithium hydroxide to calcium hydroxide being such that said mixed calcium-lithium 12-hydroxy stearate consists of 18 to 22 whpercent lithium 12-hydroxy stearate and 82 to 78 wt. percent of calcium 12- hydroxy stearate, mixing with said calcium-lithium 12- hydroxy stcarate grease a second grease comprising mineral lubricating oil thickened to a grease consistency with lithium 12-hydroxy stearate.

3. A lubricating grease prepared by co-saponifying in mineral lubricating oil lZ-hydroxy stearic acid with a lithium base and calcium base, heating to a temperature within the range of 275 to 315 F. to dehydrate, and cooling to form said grease, wherein said lubricating oil has a viscosity of 10 to 200 SSU at 210 F. and a viscosity index of 30 to 140, wherein the amount of lithium to calcium base is such as to result in a thickener consisting of 20% lithium 12-hydroxy stearate and 80% calcium l2-hydroxy stearate, said lubricating grease having 1 2,929,782 9 10 a dropping point above 320 F. and a work penetration 2,607,735 Sproule et a1. Aug. 19, 1952 at 77 F. of 300 to 360 mm./10. 1

OTHER REFERENCES References Cited m the me of thls patent The Manufacture and Application of Lubricating UNITED STATES PATENTS 5 Greases, Boner, Reinhold Pub. Corp., New York, 1954, 2,397,956 Fraser Apr. 9, 1946 pp. 599 and 600. 2,542,159 Stevens- Feb. 20, 1951

Claims (1)

1. A LUBRICATING GREASE COMPRISING A MAJOR AMOUNT OF MINERAL LUBRICATING OIL AND GREASE THICKENING AMOUNT OF A MIXED-METAL THICKENER PREPARED BY A CO-SAPONIFYING IN SAID LUBRICATING OIL 12-HYDROXY STEARIC ACID WITH LITHIUM BASE AND CALCIUUM BASE, HEATING TO A TEMPERATURE OF 275* TO 315*F. TO DEHYDRATE, AND COOLING TO FORM SAID GREASE, WHEREIN THE PORPORTION OF LITHIUM TO CALCIUM BASE IS SUCH THAT SAID MIXED-METAL THICKENER CONSISTS OF 18 TO 22 WT. PERCENT LITHIUM 2-HYDROXY STEARATE AND 82 TO 78 WT. PERCENT OF CALCIUM 12-HYDROXY STERATE.

Images