US2628195A

US2628195A - Lubricating grease

Info

Publication number: US2628195A
Application number: US185368A
Authority: US
Inventors: John R Allison; William L Blalock
Original assignee: LEFFINGWELL CHEMICAL Co
Current assignee: LEFFINGWELL CHEMICAL Co
Priority date: 1949-09-23
Filing date: 1950-09-18
Publication date: 1953-02-10
Anticipated expiration: 1970-02-10

Description

Feb. 10, 1953 J. R. ALLIsoN E-r/II.-

LUBRICATING GREASE Original Filed Sept. 23, 1949 O O N AU, NouvalI-mad A FTORNEY Patented Feb. l0, 1953 LUBRICATIN G GREASE .lohn R. Ailison and William L. Blalock, Whittier,

Calif., assignors to Leflingwell Chemical Company, Whittier, Calif., a corporation of California Original application September 23, 1949, Serial N o. 117,434. Divided and this application September 18, 1950, Serial No. 185,368

3 Claims.

This application is a division of our copending application Serial No. 117,434, led September 23, 1%9. and entitled Soaps Useful for Making Lubricating Greases.

This invention relates to water-insoluble and oil-soluble fatty acid soaps of the type used for the manufacture of lubricating greases and as bodying agents in oil paints.

The purpose of the invention is to so modify the properties of the oil-soluble soaps of commercial stearic acids, consisting principally of saturated fatty acids having from 16 to 22 carbon atoms as materially to increase their utility for these uses.

The oil-soluble soaps to which the invention applies are the salts of these acids, of which stearic acid is typical, with aluminum and with the group II metals having atomic weights greater than 24 and less than 138.

The use of aluminum stearate and of the stearates of magnesium, calcium, zinc and barium in the manufacture of lubricating greases is well known. The stearates of strontium and cadmium have likewise been used, though to a lesser extent because of their cost.

In general terms, the soap is heated and agitated with a more or less viscous mineral oil until it dissolves (or disperses) yielding a clear solution. On cooling under suitable conditions, the

resultant mass has a buttery or gelatinous conl sistency, the product having a wide variety of uses in situations in which a liquid lubricant cannot be retained in place between the engaging surfaces.

The stearates` of aluminum and, to a less extent, of the other metals named, have found considerable use also as additives in small quantities tooil paints, in which they function as suspending agents for the solid pigments, tending to prevent settlement in storage.

We have discovered that the usefulness of the oil-soluble soaps of stearic and other fatty acids is materially increased by compounding wlth them a relatively small proportion of the salt of the same metal, or of another metal of the same group, with the -carbon compound Z-ethyl hexanoic acid, also known as octoic acid.- u For convenience, the briefer term will be used throughout this specification, it being understood that the terms octoic acid and octoate, as used herein, refer to the branched chain Z-ethyl hexanoic acid and its metallic salts and not to caprylic acid H H nv E n H H ol Ho-o-C-.Qfc-cfC-o-OH n H H H H Hw-H or its metallic salts, the latter being wholly unsuited to our purposes.

We have also discovered that the properties of the above named soaps are still further modified, in a desirable manner, by what we term coprecipitation of the soaps, meaning thereby the production of a mixed oil-soluble soap by acting on an aqueous solutionvo a mixture of the alkalimetal soaps of the two acids .with an aqueous solution of a salt of the desired metal or metals.

In producing the individual soaps to be later vcompounded we work in the Awet way: for vexam- Nple, an aqueous-solution ofV sodiumv stearate or sodium octoate is blended with an-aqueous solution of an aluminum salt such as the sulfate or the chloride; the precipitate is Water-washed until substantially free from soluble salts and is then filtered, dried and pulverized.

In producing the coprecipitated soaps the sodium soaps, for example, of stearic acid and octoic acid are mixed in desired proportions in aqueous solution, or the acids themselves may be mixed and dissolved in an aqueous solution of sodium hydroxide or carbonate. The two soaps are then precipitated simultaneously bythe addition of an aqueous solution of a suitable salt, such as aluminum sulfate or one of the water-soluble salts of barium, calcium, magnesium, strontium or zinc.

It is also possible, and often desirable, to form the soaps in situ in a grease-making oil such as a 50 viscosity red oil. In this procedure we rst dissolve the two acids in the oil, which is preferably reduced in viscosity by heating. The carbonate or hydroxide of the desired metal is then added, together with a small quantity of water to promote reaction, and the mass heated with agitation and at a temperature below the boiling point of water until reaction is completed and the soaps formed. Finally, thev temperature' is raised and the Water driven off. It is preferable to use the hydroxide of aluminum, barium, calcium or strontium or the carbonate of magnesium or zinc.

It is also possible, and in some cases may be desirable, to coprecipitate the-soaps ofthe two acids with salts of more than oneme-tal, as for example with a mixture of compatible salts, such as the chlorides of acetatesof aluminum, barium, calcium, magnesium, strontium or zinc; This formation of the soaps with'two. or more metals may be produced by either ofthe manipulations above described.

3 The titer test of mixtures of the two acids is substantially a straight line function, as may be seen from the following gures:

The effect of small additions of aluminum octoate to aluminum stearate is to lower the melting point of the soap, though not to a marked degree. In the following table, showing four comparisons based on commercial aluminum stearates, with and without admixture of aluminum octoate, the rst column shows the melting point of the stearate alone, the second the melting point of a blend of the stearate with aluminum octoate, and the third the ratio of stearate to octoate in the blend.

i A Melting Peints .t

Ratio- Steal-ate stearato Stcorate Octoatc only l- Octoate f Degrees l Degrees i l S l 155 95:5 168 163 92:8 16S 162 92:8 149 M3 921s i i The addition of aluminum octoate to aluminum stearate used in grease making has a tendency to harden the grease, to decrease the extent to which penetration rises when the grease is worked and, usually, to increase the extent to which hardness recovers after working.

The ve pairs of experiments recorded in the table below were made with different samples of aluminum stearate, though in each pair the same stearate was used and the same procedure followed.

An oil of seconds viscosity was used in all the tests. The rst column in the table shows the total quantity of soap used in the test; the

second the ratio of stearate to octoate in the n Q Batio l eilcti ation., Stearate: Octoate Tcisl Soap Added Initial 217 194 247 213 los ses isz 172 172 isi The comparisons of the above table are shown graphically in Figs. 1 to 5 inclusive of the at-` g, so

the broken line representing the grease containing octoate.

The following are examples of coprecipitated soaps of certain metals other than aluminum, the soaps of the remaining metals named abve being formed in the same general manner.

Zinc soap grams stearic acid and 3.2 grams octoic acid were dissolved in an aqueous solution of 13 grams sodium hydroxide. The oil-soluble soaps were precipitated from this solution by intermixture with an aqueous solution of 45.26 grams crystalline zinc sulfate, Zn(SO4) .6I-120. The curdy precipitate was washed free from sodium sulfate, ltered and dried. The yield is theoretical.

llfagnesz'um-aluminum soap 160 grams stearic acid and 5.3 grams octoic acid were dissolved in an aqueous solution of 27.6 grams sodium hydroxide. 5.8 grams aluminum sulfate, A126003 and 80 grams magnesium sulfate, Mg SO4l .7H2O were simultaneously dissolved in water and the soaps were precipitated by mixing the two solutions. rIhis is an example of a soap of two acids with two metals.

Barium soap 80 grams stearic acid and 9.3 grams octoic acid were saponied with 16 grams sodium hydroxide in aqueous solution and precipitated with an aqueous solution of 46.3 grams barium chloride.

Strontiwn soap 40 grams stearic acid and 4.5 grams ootoic acid were dissolved in 700 grams 50 viscosity red oil at F. l0 grams water and 29.3 grams strontium hydroxide, Sr(OH)2.8H2O were then added with vigorous stirring and the temperature raised, as fast as frothing would permit, to about 260 F. at which point it was held until frothing ceased and a clear solution of the strontium soap in oil was produced. This solution was viscous while hot and set to firm grease on cooling.

These soaps are highly similar physically and may be substituted for cach other in desired proportions in the grease formula. The effects produced vary slightly as one metal is substituted for another, as is the case in the use of the stearates alone.

The useful effects produced by the addition of even small quantities of an octoic soap to a stearic or other oil-soluble soap used in grease making include the following:

Y (a) The temperature at which the grease inverts, with separation of the soap from the oil, is materially raised, lessening the risk of destruction of the lubricating lm by overheating of a bearing;

(b) The wearing property ofthe grease is improved, possibly by reason of its better retention in the bearing;

(c) A smooth, buttery consistency is developed which renders the grease irm without excessive hardness;

(d) The production of a clear grease having an attractive appearance is much facilitated and. ordinarily, the working temperaturev is somewhat lowered, with the result that the color oi the grease is improved;

(e) The grease is rendered considerably more adherent to the surfaces to be lubricated;

(f) A degree of cohesiveness is developed which, so far as we are aware, cannot even be approached in any other manner. This striking and surprising effect may be carried to any desired extent, as is illustrated by the results of the following experiment.

Three batches of grease were prepared by the incorporation of 7% of soap in a mineral oil. the same oil and the same procedure being used in each. The soap used in the rst batch was aluminum stearate; that used in the second batch was a blend of the same stearate with aluminum octoate in the ratio 95 stearate 5 octoate; that used in the third batch was a blend of the same stearate with the same octoate in the ratio 70 stearate 30 octoate.

The product of the first batch, when cold, had a soft consistency, just short of flowing when the container was inverted, and had only slight cohesiveness, the string formed on dipping a rod into the mass and withdrawing it being but a small fraction of an inch in length. The second batch was firmer and somewhat elastic and could be pulled into strings two or three inches long. rIhe third batch, containing a larger proportion of the octoate, was highly elastic, resembling raw rubber in this respect, and could be pulled into strings a foot or more in length which, on breaking, snapped back into the mass from which they Were drawn.

This property of stringiness, which was further developed in the third batch than it would be in a commercial grease, is highly valuable. Greases having this property may be made soft enough to be readily injected into close bearings While at the same time they are highly adhesive to metal surfaces and are strongly retained in relatively loose bearings such as spring shackles.

Another surprising and very useful property of the octoates is that of increasing the viscosity of oil solutions of the stearates. This property is diincult to measure in the viscous oils and in the concentrations used in grease making, but may readily be measured in solution in an aromatic solvent such as xylene.

The figures in the following table show the viscosity, in centipoises, of 2 per cent xylene solutions of two blends of aluminum stearate with aluminum octoate, one of these being a mechanical mixture and the other coprecipitated, and of one blend of aluminum stearate with aluminum caprylate, this blend being coprecipitated.

These figures, Which are shown graphically in Fig. 6 of the attached drawings, show how the viscosity of the solution increases with the addition of increasing proportions of the octoate. while it decreases when the caprylic acid soap is substituted for the octoate. They also illustrate the more rapid rise of viscosity when the two soaps are simultaneously precipitated.

The relation of octoate to stearate in the compound soap may vary over a Wide range, depending on the use to which the soap is to beput and the characteristics desired in the product in which it is to be used. Thus, in the manufacture of a lubricating grease, the proportion of soap in the grease may be from 4% to 10% of the total weight and will ordinarily be from 5% to 7%, while the proportion of octoate in the soap itself may be as small as 1% and as large as 35% of the weight of soap, with the ordinarily preferred range from about 2% to about 10%.

For use as an additive to oil paints, the total soap in the paint must be restricted to prevent livering of the paint and Will be within the range from 1/2% to about 3% of the total Weight. On the other hand, the proportion of octoate in the soap used for this purpose may be greater, as for example from 1% to 50% of the weight of the soap, with the ordinarily preferred range from about 20% to about 30% of the soap weight.

We claim as our invention:

l. |The method of producing a compound soap of stearic acid and 2-ethyl hexanoic acid in situ in a lubricating grease formulation which consists in bringing said acids into joint solution in a mineral lubricating oil, mixing with said solution a small proportion of water and a base selected from the group consisting of the hydroxides and carbonates of aluminum, barium, calcium, magnesium, strontium and zinc, and heating the mixture to a temperature above the boiling point of water to bring the resultant soaps into solution in said oil and to drive off any water contained therein; the proportions in which said acids are used being so controlled that the soap of 2-ethyl hexanoic acid represents from 1% to 35% of the Weight of said compound soap.

2. A lubricating grease containing a mineral lubricating oil and a compound soap of stearic acid and 2-ethyl hexanoic acid with at least one metal selected from the group consisting of aluminum, barium, calcium, magnesium, strontium and zinc, in which said compound soap represents from 2% to 10% of the weight of said grease and the soap of Z-ethyl hexanoic acid represents from 1% to 35% of the weight of said compound soap.

3. A lubricating grease containing a mineral lubricating oil and a compound soap of stearic acid and 2-ethyl hexanoic acid With at least one metal selected from the group consisting of aluminum. barium, calcium, magnesium, strontium and zinc, in which said compound soap represents from 5% to 7% of the weight of said grease and the soap of 2-ethyl hexanoic acid represents from 2% to 10% of the weight of said compound soap.

JOHN R. ALLISON. WILLIAM L. BLALOCK.

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

UNITED STATES PATENTS Number Name Date 2,274,675 Earle Mar. 3, 1942 2,390,609 Minich Dec. 11, 1945 2,417,071 Gebhart et al Mar. 11, 1947 2,447,064 Gebhart et al Aug. 17, 1948

Claims

1. THE METHOD OF PRODUCING A COMPOUND SOAP OF STEARIC ACID AND 2-ETHYL HEXANOIC ACID IN SITU IN A LUBRICATING GREASE FORMULATION WHICH CONSISTS IN BRINGING SAID ACIDS INTO JOINT SOLUTION IN A MINERAL LUBRICATING OIL, MIXING WITH SAID SOLUTION A SMALL PROPORTION OF WATER AND A BASE SELECTED FROM THE GROUP CONSISTING OF THE HYDROXIDES AND CARBONATES OF ALUMINM, BARIUUM, CALCIUM, MAGNESIUM, STRONTIUM AND ZINC, AND HEATING THE MIXTURE TO A TEMPERATURE ABOVE THE BOILING POINT OF WATER TO BRING THE RESULTANT SOAPS INTO SOLUTION IN SAID OIL AND TO DRIVE OFF ANY WATER CONTAINED THEREIN; THE PROPORTIONS IN WHICH SAID ACIDS ARE USED BEING SO CONTROLLED THAT THE SOAP OF 2-ETHYL HEXANOIC ACID REPRESENTS FROM 1% TO 35% OF THE WEIGHT OF SAID COMPOUND SOAP.