US2245702A - Grease composition - Google Patents

Description

latented June 17, 1941 GREASE comosrrron Arnold J. Morway, Roselle, N. .L, assignor to Standard Oil Development Company, a. corporation of Delaware No Drawing. Application November 24, 1937, Serial No. 17 6,222

3 Claims.

The present invention relates to an improved grease composition which has a smooth structure and which is stable both in respect to its structure and to oxidation characteristics. The methd of preparing the grease and its composition will be fully understood from the following description.

Industrial greases are prepared by dissolving certain metallic soaps in lubricating oils, and many different soaps have been used. In addition, certain mixed base greases which contain mixtures of different soaps have been known in the art and by suitable mixtures it is possible to obtain propertieswhich are not obtained by the use of any single soap. Soda soaps are used to make hard greases which while desirable for many purposes are not suitable for others. Such greases often contain glycerine and are characterized by a markedly fibrous, structure. Barium .soap greases, on the other hand, are soft, buttery and without fibre, but such greases must contain water and in consequence are non-reversible; that is to say they lose their structure on heat- F. in order to accomplish this. The hydroxides of the metals are then added, preferably in aqueous solution. It has been found best to add barium hydroxide first while maintaining a temperature of from 130 to 180 F. The mixing is continued for about an hour at this temperature and thereafter caustic soda is added preferably in an aqueous solution. The mixture is then thoroughly stirred and heated up to about 350 F. or higher, at which temperature thegrease becomes smooth but ropey, and steam is allowed to escape so that the final product will be substantially anhydrous. The mixture is then cooled to about ISO-200 F. and is worked at this temperature for about one hour. Under' such conditions, very little, if any basic barium soap is produced. g

The amount of soap in the present composition may vary, say from 10% to 40%, depending on the particular type of grease desired,,its penetration and other qualities, and the balance of the composition is a mineral lubricating oil. 'Any I particular type of lubricating oil may be used,

ing and do not regain it on subsequent cooling because of the loss of Water.

It is desirable to make a grease for use in the lubrication of small gears; for example, in the use of household appliances such as mixers, kneaders, and for timing gears and the like.

Such a grease should be buttery, soft, without but those having viscosities from say 90 to 350 seconds Saybolt at 100 F. are preferred. The ratio in which the two soaps are used may also vary'considerably, but the amount of soda soap should not be more than about ten ,times the fibre, reversible and capable of maintaining its structure up to temperatures of about 200 F. or somewhat higher.

be used also in anti-friction bearings and the like; I Y 1 "It has been found that an excellent grease of the type desired can be prepared from the mixed soaps of soda and baryta, which are free from the difiiculties found in greases containing either the one or the'other of such soaps alone. The present grease is made from a fatty acid such as stearic acid and the hydroxide of the two metals barium and sodium. It is preferred to use the acids rather than fats. It will be understood that other acids may be employed, for example oleic acid, but a saturated acid is preferred; also Such a grease is not limited to the particular uses mentioned above, but may 0 amount of the barium "soap, so as to prevent the product from becoming too hard and grainy.

, Similarly, it is preferred that the amount of soda I1 soap should not be less than the amount of barispecific uses.

' um soap, as such materials aretoo soft and become too fluid, at elevated temperatures. The preferred ratio falls within the range between 2 r to land 8 to 1 parts of the sodium soap per part by weight of the barium soap, and by varying this ratio slightly between the limits given, the properties may be gradually changed as desired for The finished grease preferably contains no glycerinev or water and has a preferred free-a1- kali content of between 0.05 and 0.3% but not mixed acids such as are obtained from commercial fats, lard, tallow and the like can be used as well as acids prepared by oxidation of hydro carbon oils and waxes.

In the manufacture of the grease, the acid is over 0.5% and is for this reason of a non-fibrous, smooth, buttery structure; It is reversible and has an A. S. T. M. penetration between about 200 and 300 at 77 F., and a melting point in the neighborhoodof 360 F.; it keeps'its body up to temperatures close to the melting point tending to become semi-fibrous around 230-240 F.

"As an example of the manufacture of the grease, the following may be considered:

425.0 parts by weight of stearic acid and 500 parts by weight of a mineral lubricating oil having a viscosity of 200 seconds Saybolt at F.

additions. When saponification is completed and water has been substantially, completely elimihated, the product is cooled to about 200 F. while stirring and is worked at that temperature for two to three hours. The grease has the following composition:

Percent Barium stearate 2.75 Sodium stearate 21.25 Mineral 011-- 76.00

The product made according to the above procedure and having the above mentioned composition was found to have an A.- S. T. M. penetration test of 250-270 at 77 F.

The material was then tested in the Mechanical stability testing machine of the Bearing Engineers Committee. The machine and the test method was described by C. R. Gillette, at a meeting of the National Association of Grease Manufacturers, Inc., at Chicago, Ill., October 12-13, 1936, the following is quoted from his paper: I

The machine consists of a base, a vertical column, a constant speed 3450 R. P. M. motor and an extension to the motor spindle, upon which is mounted a plate shielded, Conrad type, size 204 S. A. E. bearing. This bearing is mounted in a grease cup which is free to turn with the hearing. A, flexible cord connecting this cup withthe torque scale spring, provides a means is then assembled on the bearing and the grease,

in the cup leveled ofi.

The oil bath is raised to the stop on them]- umn, with the damping vane-on the grease cup:

in front.

The flexible cord from the torque spring is attached to the cup by means of the slot provided.

For the start of the initial test,- the oil tem- Rating Poor perature is adjusted to -85 F. The motor is i started and the starting torque is observed. .The running torque is recorded at intervals throughout the test. The test is continued for twenty Temperature of test ao s5 F. F. 220F.

Starting torque 25 Avg. running torque 8 4 Rating Good Good Good The grease did not become fibrous, aerate, or materially change its consistency. There was no tendency to leak through the bearing.

For comparison a similar series of tests were made on a typical soda lime grease made from animal fat such as is now used commercially. The ratio of soda to lime was about 5 to 1. Temperature of test--- 80-85 F. 150 F. 220 F. Starting torque 25 Avg. running torque--- Poor Poor Thisgrease became quite fibrous during the 150 and 220 F. tests, began to climb the shaft and was partly thrown out of the bearing. It had also become much harder after the tests.

In preparing these greases it has been found that excellent products may be prepared when the ratio of sodium to barium soap is in the range of from 2:1 to 3 21 or from 5:1 to 10:1 and although suitable products have likewise been obtained with intermediate ratios, it is felt that the best products have ratios within one or the other of these ratios.

It will be understood that while the grease is preferably made up as indicated above, the soaps may be made in the absence of the oil and may then be admixed in the desired proportions, or

each soap may be made up in a separate portion -of the oil and the solutions mixed as desired.

In every case, however, it is necessary to thor-' oughly mix the product, preferably at an elevated temperature.

The present invention is not to be limited to any theory of the eifect of either of the ingredients, nor to any particular proportions thereof, I claim:

1. An'improved substantially anhydrous lu bricating grease consisting of mineral oil, from 10 to 40% of a soda soap and barium soap mixture,

the said soaps being in a proportion of from to 40% of sodium and neutral barium soaps, the

latter ingredients being in relative proportions from about 2:1 to El /2:1.

3. An improved substantially anhydrous grease composition comprising mineral oil and from 10 minutes, atwhich time the torque approaches a to 40%of sodium and neutral barium soaps, the

latter ingredients being in relative proportion from 5:1 to 10:1.

' ARNOLDJ. MORWAY.