US2915468A - Mixed base sodium calcium grease manufacture - Google Patents

Description

United States Patfifl MIXED BASE SODIUM CALCIUM MANUF GREASE ACTURE Francis E. Chamberlin, Steger, Ill., assignor to Sinclair Refining Company, New York, N.Y., a corporation of Maine No Drawing. Application January 10, 1955' Serial No. 481,010

3 Claims. (Cl. 252-40) This invention relates to mixed base sodium-calcium greases. In particular, the present invention is concernedwith a method of manufacturing mixed base sodiumcalcium greases whereby certaindesirable grease fibre structure is obtained.

In a study of the elemental structure of mixed base heterogeneous thin and narrow ribbon-like soap fibres.

with the larger fibres bent and intertwined is characterized by excellent mechanical stability under severe conditions of working and superior low temperature torque performance, whereas the same grease comp'os ition having flat short thick straight fibres will be undesirable asregards these particular properties.

By the present invention a method is provided whereby mixed base sodium-calcium greases can be prepared having heterogeneous thin and narrow ribbon-like fibres with the larger fibres' bent and intertwined. The present invention also provides a method whereby mixed sodiumcalciurn greases characterized by excellent mechanical stability under severe conditions of working and superior low temperature torque performance are produced. These and other advantages are obtained in accordance with the present invention by control of certain aspects of the dehydration step in preparing mixed base sodiumcalcium greases.

Soap fibres in mixed base sodium-calcium l2-hydroxy stearate greases are crystalline in nature and, therefore, difierences in fibre appearance reflect difierences in crystal formation or nucleation and growth of the soap fibres. Contrary to normal expectations, it has been discovered that the final fibres of the grease do not steadilygrow from nuclei formed in the saponification step. Instead, long after/the saponification reaction is completed, the fibres are nucleatedvand grow to the final form. These fibres of the final grease composition are to be distinguished from the small amounts of fibres that form at early stagesof'the soap makingprocess which are no' more than transitory phases possibly limited to localized.

spots throughout-the body of the grease.

In the present invention the natureof the fibres of the final grease composition is established by careful control of the rate of removal of water from the grease during the final nucleation to'form the end fibre structure. Generally, the final nucleation of fibres in sodium-calcium 12-hydroxy stearate greases occurs during removal of about the final 2.5 to 2.0 weight percent of water, on an oil-free basis, from. the grease during the dehydration;

Thus, it has been found that heterogeneous thin and narrow ribbon-like fibres and the larger fibres bent and twisted can be produced in a sodium-calcium 12-hydroxy stearate grease as the final fibre structure byremoving about the final 2.5, to 2.0 weight percent of the water content as rapidly as is consistent with the presence of fibres in the resulting product. Y While the present invention is not theory,

The solubility of soap in the oil phase is believedto be increased by. the presence of water and decreases as the. water is removed. If water is removed rapidly, many soap nuclei would form and grow into small fibres. If, however, water is removedslowly due, for example, to

diffusional problems in the reaction mass or refluxing'of water throughout the mass, then crystal growth would be slow resulting in large fiat fibres. That is, crystals would be growing for a longer period and would result in larger fibres. Thus, the essence of the present invention is to remove the remaining water rapidly during the final nucleation of fibres so that longer flat fibres will not result.

Rapid removalv of about the final 2.5 to 2.0 percentof the water content, can be accomplished in various ways. For example, by effecting'all of the dehydration of the grease at a sufiicie'ntly high temperature it is evident that all dehydration, and thus the final 2.5 to 2.0 weight percent, will be rapid. This method involves the temperature coefiicient of solubility of the soap in water-oil mixtures. By dehydrating at temperatures where the coefiicient of solubility is'high and large changes in solubility can be effected by small changes in temperature,

the rate of dehydration will'be sufliciently large. 'It'is important, however, that the removal of the final 2.5 to 2.0 percent of the water is not accomplished at a rate similar to flash dehydration 'because the resulting fiber structurewould notbe satisfactory. For this reason, the

removal of the final 2.5 to 2.0 percent of water is carried to be limited byit ,is believed that the ultimate grease structure can be explained in terms of a solubility phenomenon:

out at substantially constant pressure, and preferably the entire dehydration is accomplished at atmospheric pressure.

As discussed above, the present invention is effected in a manner whereby dehydration will be effected rapidly so that about the final 2.5 to 2.0 weight percent of the water will be removed at the necessary high rate. For certain greases, the removal of only the remaining 2.0 percent of water at the rate indicated will be sufiicient to obtain the described advantages. It is apparent therefore, that the rate of dehydration is of critical importance. It has been determined that as long as the grease is at a temperature above 300 F. during the removal of the final 2.5 to 2.0 percent of Water, the rate of dehydration is sufficient to result in a fibre structure characterized by heterogeneous thin and narrow ribbon-like fibres with the larger fibres bent and intertwined for grease batches up to about 15,000 pounds. While in this specification it is said that the final 2.5 to 2.0 weight percent of water is removed, it should be understood that an absolute anhydrous state is not essential. Thus as a practical matter, the water content is reduced at the described rate from a content of about 2.5 to 2.0 percent down to at least as low as 0.5 percent and preferably to below 0.1 percent. The upper temperature limit employed generally is determined by the amount of grease being handled and temperature stability of the soap fibres. Larger quantities of grease require higher temperatures, i.e., about 325 to 350 F. On the other hand, a temperature of 340 F. maintained for a long period of time will result in melting the fibres so it is incumbent upon the operator, when using temperatures of 335 F. and higher, to cool the grease (stop heating) substantially immediately upon completion of the dehydration.

Mixed base sodium-calcium greases which can be subjected to dehydration in accordance with the present invention contain sodium and calcium in a weight ratio of about 3 to 10 parts of sodium per part of calcium. These can be employed in any of the usual forms, for example, asoxides, hydroxides, hydrated oxides, carbonates, etc. In the preferred greases a 4 to 6:1 and particularly 5:1 ratio of flake caustic to hydrated lime is employed.

The fatty component employed can be substantially pure 12-hydroxy stearic acid or its glycerides', e.g'. hydrogenated castor oil. Particularly satisfactory greases are prepared when hydrogenated castor oil is saponified by the sodium component and 12-hydroxy stearic acid is saponified by the calcium. In such grease the fatty components are preferably employed in a weight ratio of hydrogenated castor oil to l2-hydroxystearic acid of about 3 to :1 and preferably 4 to 6: 1, particularly 5:1. The total soap content of the final grease compositions is normally about 10 to 25 weight percent and preferably to weight percent.

The oil component employed in preparing greases according to the present invention can be synthetic or mineral base and the oil can be highly refined and solventtreated if desired. Preferably a mineral base lubricating oil is saponified. Suitably, the oil has a viscosity of about 50 to 1500 SUS at 100 F, with about 100 to 150 SUS being the preferred range. Normally the final grease compositions analyze at about 75 to 90 weight percent oil with about 80 to 85 percent being average.

The critical rate of water removal during nucleation of the fibres of the final composition constituting the essence of this invention is applicable to mixed base sodium-calcium 12-hydroxy stearate greases however formed. However, the preferred procedure to be employed is the reverse saponification technique since apparent advantages in yield result as well as advantages regarding speed of dehydration. This technique involves saponifying hydrogenated castor oil in starting oil with the sodium component and then adding 12-hydroxy stearic acid to't'he mass and saponifying theac'id with the calcium component. This preaure is more fully dembns'trated 4 in Example I below. Other procedures can be used; for example, the greases can be made by blending finished sodium and calcium greases together in the desired proportions, by making the soap bases separately and then combining and finishing the grease by adding the soap bases as a mixture, by employing low or high temperature conditions for mixing, saponification and the like. In other words, the fibre structure of the finished grease normally cannot be affected permanently by the processing conditions so long as the critical dehydration step of this invention is employed. It should also be understood that additives, such as antioxidants, extreme pressure additives, and the like can be added in the usual amounts so long as they do not deleteriously affect the invention.

The invention will be described further in conjunction with the following specific example:

EXAMPLE I A blend composed of solvent refined Mid-Continent neutral oils was employed in preparing this grease. The blend had the following characteristics:

Gravity -API Flash, F. Fire, F. Viscosity:

SUS at F. 126.0

SUS at 210 F. 41.43 Viscosity index 96 Pour, -F. 10 Color, NPA 1 Five parts of the oil blend and 5.0 parts of hydrogenated castor oil are charged to a grease kettle. Heat is applied to the kettle and the temperature of the mixture is brought to 200 F. and held until all of the castor oil has melted whereupon a stoichiometric amount of caustic, as a 50 percent solution in water, is added. A temperature rise resulting from the heat of reaction occurs and is accompanied by foaming. After the foam subsides, 1.0 part dry 12-hydroxy stearic acid is added. Upon melting the acid, one part 'of a lime-oil slurry, containing lime to oil in the ratio of about 1:7, is added. The temperature is then promptly raised to about 345 F. and held for one hour after which the temperature is permitted to drop. When the kettle mixture reaches about 320 F., about 5 parts of finishing oil are added as the temperature continues to drop to 300 F. The bulk of the finishing oil, i.e. about 25 parts by weight, is added between about 280 and 300 F. The grease is permitted to cool further and is then homogenized in a colloid mill in the conventional manner.

Three commercial size batches, that is, two 5000 pound batches and one 12,000 pound batch, of mixed base sodium-calcium grease were made according to the procedure of Example I and tested to determine their suitability as Navy Specification M'ILL7711 greases. Of the tests on greases for this purpose, low temperature torque and worked stability are especially significant. The low temperature torque test procedure consists of packing a 204K Conrad type, 8-ball bearing with 3.0 grams of test grease. The packed bearing is mounted on a spindle and cooled to 40 F. After temperature equilibrium vis reached, a torque of 2000 gram-centimeters is applied and the time required for a complete revolution is measured. The specification allows a maximum of 10 seconds. The worked stability test consists of measuring the penctration with an ASTM apparatus after the grease has been worked 100,000 double strokes in an ASTM mechanical worker using a plunger plate with 270 holes of 6 inch diameter rather than the conventional plunger plate used in the ASTM method. The specification permits a maximum penetration of 375 at the end of 100,000 strokes. The results obtained for all of the tests appear in the following table;

T able l Batch N o Soap Content, Percent Dehydration Temp., F Milling Temp., "F Mill Clearance, IllPllOs MIL-L-7711 Specification Tests Specification Requirement 1,000 Hrs. at 250 F Max. 375 +30 from Worked Penetratiom Unifo .10 .11 Worker Test, 100,000 Strokes .12 Storage Stability 3,13 Workmanship--- 3.14 Rubber Swell Unworked Penetration 3.1 Materials Smooth, homogeneous, etc 3.2 Odor No rancidity or perfume. t 3.3 Dropping Point, F Min. 300 F 3.4 Worked Penetration 60 Strokes 205-340 (ASTM). 3.5 Cu Corrosion l\ o p1ttingmin. discoloration 3.6 Dirt Max;

7,500/ec. of 25 microns 1,600/cc. of 75 microns None of 125 microns 3.7 Bomb Oxidation Max. PSI Drop-100 Hr 3.8 Water Resistanoe Max. 50% oss 3.9 Low Temp. Torque Max. Sec.Each Direction. 3 High Temp. Performance Min 3 3 rm Not over value on high swell reference Bleed (ANG-lO), Percent IBG 1297 BG1358 BG 79 Pass Pass Pass Pass Pass Pass 328 317 321 313 313 307 Pass Pass Pass 5043 1414 3321 61 61 246 0 0 0 3 1 4 5. 65 9. 19 6. 36 6. 2 6. 7 7. 6 1021 1 573 1 236 355 351 349 I: Pass Pass Pass Pass Pass Pass 1 Tests still in progress.

The suitability of greases prepared by a method employing the critical dehydration procedure of the present invention for the purposes of Navy Specifications MIL-L7711 is shown in the above table. While the greases are shown to be eminently satisfactory in all respects, the large measure by which the greases passed tests 3.9 and 3.11 is considered especially significant. Greases prepared in commercial size batches while em.- ploying substantially identical quantities and qualities of sodium, calcium, fatty components and oil which were dehydrated at the materially lower rate normally employed prior to the present invention consistently failed to meet specification tests 3.9 and 3.11 in addition to being undesirable in other respects, such as having a grainy appearance.

What is claimed is:

1. In the manufacture of substantially anhydrous mixed base sodium-calcium greases wherein a mineral lubricating oil is thickened to a grease consistency with mixed sodium and calcium 12-hydroxy stearates, where the quantity of sodium employed is about 3 to 10 parts per part of calcium, and the resulting grease is dehydrated, the step of removing the water present during the final nucleation of the fibres at a temperature of at least 300 F. and insufiicient to melt the fibres and at substantially constant pressure to remove water rapidly and form the fibre structure of the final composition.

2. In the manufacture of substantially anhydrous mixed base sodium-calcium greases wherein a mineral lubricating oil is thickened to a grease consistency with sodium and calcium l2-hydroxy stearates, where the quantity of sodium employed is about 3 to 10 parts per part of calcium, and the resulting grease is dehydrated, the step of removing about the final 2.5 to 2.0 weight percent of water present during the final nucleation of the 0 fibres at a temperature of about 300 to 350 F. and insufiicient to melt the fibres and at substantially constant pressure to remove water rapidly and form the fibre structure of the final composition.

3. In the preparation of mixed base sodium-calcium greases wherein a mineral lubricating oil is thickened to a grease consistency with sodium and calcium 12-hydroxy stearates, where the quantity of sodium employed is about 3 to 10 parts per part of calcium, and the resulting grease is dehydrated, the steps of saponifying hydrogenated castor oil in the presence of mineral lubricating oil with an aqueous solution containing sodium, adding 12- hydroxy stearic acid to the reaction mass and saponifying said acid with calcium, raising the temperature of the reaction mass to about 300 F. and insuificient to melt the fibres to remove about the final 2.0 weight percent of water present rapidly during the nucleation of the fibres which form the final fibre structure and at substantially constant pressure.

References Cited in the file of this patent OTHER REFERENCES Boner: Lubricating Greases, 1954, Rheinhold Pub. Co., New York, N.Y., pp. 585-588.

UNITED STATES PATENT OFFICE v CERTIFICATE OF CORRECTION- Patent No. 2,915,468 December l 1959 Francis. E. Chamberlin s in the printed specification It is hereby certified that error appear tion and that the said Letters of the above numbered patent requiring correc Patent should read as corrected below.

Column 3, line 59, for saponified' read employed columns 5 and 6 Table I, under the heading "BG 129'?" and opposite "Mill Clearance, Inches", for .'0.0004-:" read 0,004 column 6 line 43 for "about" read above e,

Signed and sealed this 9th day of August 1960.

SEAL) Attest:

KARL H. AXLINE Attesting Oflicer ROBERT c. WATSON Commissioner of Patents

Claims (1)

1. IN THE MANUFACTURE OF SUBSTANTIALLY ANHYDROUS MIXED BASE SODIUM-CALCIUM GREASES WHEREIN A MINERAL LUBRICATING OIL IS THICKENED TO A GREASE CONSISTENCY WITH MIXED SODIUM AND CALCIUM 12-HYDROXY STEARATES, WHERE THE QUANTITY OF SODIUM EMPLOYED IS ABOUT 3 TO 10 PARTS PER PART OF CALCIUM, AND THE RESULTING GREASE IS DEHYDRATED THE STEP OF REMOVING THE WATER PRESENT DURING THE FINAL NUCLEATION OF THE FIBRES AT A TEMPERATURE OF AT LEAST 300* F. AND INSUFFICIENT TO MELT THE FIBRES AND AT SUBSTANTIALLY CONSTANT PRESSURE TO REMOVE WATER RAPIDLY AND FORM THE FIBRE STRUCTURE OF THE FINAL COMPOSITION.