US3068173A

US3068173A - Process for preparing complex calcium salt-calcium soap grease

Info

Publication number: US3068173A
Application number: US835443A
Authority: US
Inventors: James R Roach; Terence B Jordan
Original assignee: Texaco Inc
Current assignee: Texaco Inc
Priority date: 1959-08-24
Filing date: 1959-08-24
Publication date: 1962-12-11
Anticipated expiration: 1979-12-11

Description

United States Patent 3,068,173 PROCESS FOR PREPARING COMPLEX CALCIUM SALT-CALCIUM SOAP GREASE James R. Roach, Beacon, and Terence B. Jordan, Fishkill,

N.Y., assignors to Texaco inc, New York, N.Y., a corporation of Delaware No Drawing. Filed Aug. 24, 1959, Ser. No. 335,443 Claims. (Cl. 252-39) This invention relates to complex calcium salt-calcium soap thickened greases, and is a continuation-in-part of our copending application Serial No. 700,984, filed December 6, 1957, now abandoned.

Calcium salts of low molecular weight fatty acids have been employed heretofore in calcium soap thickened greases, usually in small amounts as stabilizing agents. It has also been found, as disclosed for example in US. 2,846,392, that calcium base greases of improved load bearing and other properties are obtained by employing as the thickening agent a complex of a calcium soap with a high proportion of a calcium salt of a low molecular weight fatty acid, formed by heating together a mixture of calcium soap and calcium salt in a mol proportion of 1:7 to 1:40, respectively, at a temperature within a high temperature transition range above about 400 F., ordinarily occurring in about the range 450-550 F., during the grease making process.

We have now found very unexpectedly that improved calcium base greases are obtained by employing a large proportion of a calcium salt of a low molecular weight fatty acid in conjunction with a calcium soap in the grease preparation and carrying out a heat treating step upon the mixture within a low temperature transition range, above 250 F. but below the high temperature transition range. The calcium salt is employed in an amount preferably equal to at least about 13 percent by weight of the finished grease and in a mol ratio of at least about 6:1 with the calcium soap. Greases are obtained in this manner having very superior extreme pressure properties as compared with calcium soap greases of the prior art containing calcium salts, including such greases containing calcium salts in high proportions obtained by methods involving complexing the calcium soap and calcium salt at high temperatures. In addition, this method offers very substantial advantages in convenience and economy over the methods involving a high temperature heating step. The special object which is attained by our invention is the production of greases having the extreme pressure and other properties required to meet US. Steel Specification No. 355 for an extreme pressure steel mill grease in a convenient and reproducible manner. The heat treating step within the low temperature range and the amount and proportion of calcium salt employed are critical for obtaining this results by the method of our invention.

The manner in which the calcium soap and calcium salt are associated in these greases is not exactly known. A large amount of thickening occurs during the heat treating step which is greatly in excess of the separate thickening effects of the calcium soap and calcium salt, indicating that a complex of some type is formed. Also, the greases thus produced are highly water resistant, which would be very unexpected in a grease containing a large amount of uncombined Water soluble calcium salts. However, the typical X-ray diffraction patterns of the calcium salts do not disappear following the low temperature heat ice treating step, in contrast to the results obtained with the high temperature heating step as reported in the literature, and it therefore appears that a portion of the calcium salt may be uncombined or in the form of some purely physical combination with the calcium soap or calcium soap-salt complex.

The preferred procedure in accordance with this invention comprises employing in the grease mixture a small amount of an estolide of a high molecular weight hydroxy fatty acid, as disclosed-in our above-mentioned application Serial No. 700,984. Suitable materials of this character are obtained by the interesterification of C to C hydroxy fatty acids and have average molecular weights in the range from about 500 to about 2500. By employing these estolides in amounts from about 0.1 to about 2.5 percent by weight based on the weight of the finished grease, a large improvement in the grease yield is obtained, and the deterioration in grease yields resulting from the use of the large amounts of calcium salts in these greases can be thereby overcome to a very substantion extent. The estolide may be added at any stage in the grease making process, either before or after the heating step.

The greases of this invention comprise a lubricating oil as the chief component thickened to a grease consistency with a calcium lower fatty aicd salt and calcium higher fatty acid soap in a mol ratio between about 6:1 and about 40:1, respectively, most suitably between about 7:1 and 25:1, respectively, and preferably from about 7:1 to about 20:1 respectively. The calcium salt is very suitably present in an amount between about 13 percent and about 24 percent of the weight of the grease, and preferably in an amount between about 14 percent and about 22 percent of the weight of the grease. The calcium soap is very suitably present in an amount of about 4-10 percent by weight, preferably in an amount of about 4-8 percent by weight of the grease. The calcium salt and calcium soap are preferably employed in proportions such as to provide a concentration of the calcium saltcalcium soap complex in the range of about 1030 percent by weight in the grease composition. The grease may be substantially neutral, or it may contain either a small amount of free acid or free alkali. It is preferably slightly alkaline with about 0.1-1.5 percent by weight of free alkali, calculated as calcium hydroxide. Greases obtained in accordance with the preferred procedure wherein a small amount of estolide is employed in the grease mixture, also contain about 0.1-2.5 percent by weight of estolide or calcium salt thereof.

The lubricating oils forming the major constituent of these greases may be any oils of lubricating characteristics which are suitable for use in lubricating greases generally. Such oils include particularly the conventional mineral lubricating oils having Saybolt Universal viscosities in the range from about seconds at F. to about 225 seconds at 210 R, which may be either naphthenic or parafiinic in type or blends of different oils. The preferred mineral oils are those having Saybolt Universal viscosities in the range from about 300 seconds at 100 F. to about 100 seconds at 210 F., which may be blends of lighter and heavier oils in the lubricating oil viscosity range.

Synthetic lubricating oils, which may be preferred for obtaining greases having special properties required for certain types of lubricating service, include oils prepared by cracking and polymerizing products of the Fischer- Tropsch process and the like, as well as other synthetic oleaginous compounds such as diesters, polyesters, polyethers, etc., having viscosities within the lubricating oil viscosity range. Examples of suitable diesters include the aliphatic diearboxylic acid diesters, such as di-Z-ethylhexyl sebacate, di(secondary amyl) sebacate, di-Z-ethylhexyl azelate, di-iso-octyladipate, etc. A particularly suitable class of synthetic polyesters are those described in US. 2,628,974, obtained by reacting an aliphatic dicarboxylic acid with a glycol and a monofunctional aliphatic alcohol or acid. Examples of polyethers include particularly polyalkylene glycols such as polyethylene glycol and polypropylene glycol. The sulfur analogs of these diesters, polyesters and polyalkylene ethers are also suitable for use in the grease compositions of this invention. Examples of suitable compounds of this type include di-Z-ethylhexylthiosebacate, di-n-octylthioadipate, polyethylenethioglycol and the reaction product of adipic acid, thioglycol and 2-ethylhexyl mcrcaptan.

The calcium soap component of the grease is obtained by the saponification of high molecular weight substantially saturated fatty acids containing -22 carbon atoms. By substantially saturated is meant such acids having iodine numbers below about 40, and preferably below about 20. The acids may be either unsubstituted or hydroxy substituted acids, or mixtures thereof. Examples of suitable high molecular weight fatty acid materials which may be employed in the saponification include stearic acid, palmitic acid, myristic acid, lauric acid, 12- hydroxystearic acid, 9-hydroxystearic acid, 9,10-dihydroxystearic acid, S-hydroxypalmitic acid and the monoesters and glycerides of such acids. The preferred saponifiable materials contain a major proportion of unsubstituted fatty acid materials. Very advantageously, a mixture of acids of the character described containing a major proportion of unsubstituted fatty acids having from 12 to 16 carbon atoms per molecule, or the esters of such acids, is employed.

The calcium salt component of these greases is derived from low molecular weight saturated fatty acids containing 1-3 carbon atoms. The calcium salt can thus be calcium formate, calcium acetate, calcium propionate, or mixtures thereof. In further description of the invention, calcium acetate will be used to illustrate the calcium salt component of these greases, although it will be understood that calcium salts of formic and propionic acids may be substituted therefor.

In accordance with the method of this invention, a grease mixture comprising a calcium salt and calcium soap in the above indicated proportions together with lubricating oil constituting all or a portion of the lubricating oil contained in the finished grease is heated at an elevated temperature of at least about 250 F., preferably at least 255 F., but below about 400 F. until at least substantial thickening has occurred. The length of time required varies with the temperature, and may range from a few minutes at the higher temperatures to several hours at lower temperatures within the disclosed range. It is ordinarily from 0.25 to 4 hours. The heating is preferably carried out at a temperature of at least about 275 F., in order to obviate excessively long heating times, and not in excess of about 375 F., in order to avoid local overheating of the grease mixture to temperatures within the high temperature transition range. It is preferably carried out at a temperature below about 350 F., very suitably at a temperature in the range 260-325 F., and particularly in the range 260310 F., in order to obtain improved storage characteristics as disclosed in the above cited application Serial No. 700,984. Most advantageously, the heating step is carried out at a temperature in the range from about 290 F. to about 350 F. for a period from about 30 minutes to about 2 hours.

The grease mixture may be obtained by coneutralizing the high molecular weight fatty acid material and low molecular weight fatty acid material in situ by means of a suitable basically reacting calcium compound such as calcium oxide or calcium hydroxide, or by forming the calcium salt in the presence of the calcium soap. It may also be formed by employing a preformed acid salt of low molecular weight fatty acid, represented by the formula Ca(C H O- .(C H O for the acetate salt, wherein n is an integer having a value of 1-3. The preferred procedure comprises in situ saponification and neutralization under substantially anhydrous conditions, wherein the low molecular weight fatty acid material is added to the saponification mass after at least substantial saponification has occurred. This overcomes the problem of graininess of the product due to the formation of coarse crystals of calcium salt which tend to form when the low molecular weight acids are added to the mixture containing high proportions of unreacted calcium hydroxide.

In carrying out the grease preparation by the preferred procedure, the grease kettle is charged with the higher fatty acid material, the total amount of calcium hydroxide required and lubricating oil which is a substantially nonreactive under the saponification conditions, and the mixture stirred or otherwise agitated so as to form an intimate mixture. The kettle is then heated and lower molecular weight fatty acid material added gradually after at least substantial saponification has occurred and when the temperature of the mass is below the boiling point of the acid material, preferably below about 200 F. The grease mixture is heated at below about 200 F. for a sufficient time to complete the saponification and neutralization reactions and then at a higher temperature to dehydrate and form the salt-soap complex as described above. The grease mixture may be cooled in any convenient manner and is preferably finished by milling. Additional lubricating oil may be added at any stage of the process.

The following examples are given for the purpose of further disclosing the invention.

EXAMPLE I A series of greases comprising calcium acetate and calcium soap in a 7:1 mol ratio was prepared in accordance with this invention by the method involving forming the calcium salt of the low molecular weight acid in situ in the saponification mass and heating the grease mixture at a maximum temperature between about 275 F. and 375 F. The lubricating oil employed was a blend in a 2.3 ratio by weight respectively of a refined paraflinic distillate oil having a Saybolt Universal viscosity of about 185 at F. and a refined residuum from a mixed base crude having a Saybolt Universal viscosity of about 156 at 210 F. The calcium soap was obtained by saponification of commercial coconut oil fatty acids, having a saponification number of 253 and an iodine number of 12.2.

The following is a detailed description of the preparation of one of these greases: A grease kettle was charged with 25.7 pounds of mineral lubricating oil, 2.32 pounds of coconut oil fatty acids, and 3.68 pounds of lime, and the mixture heated With stirring and with circulation of the grease mixture through an outside recycle line containing a gear pump in order to obtain thorough mixing. When the temperature of the mixture had reached F 4.65 pounds of glacial acetic acid were added and the heating continued at 3l03l8 F. The temperature was maintained at 310-318 F. for 2 hours and the mixture then cooled to 250 F. at a rate of about 2 F. per minute, while adding an additional 30.8 pounds of mineral lubricating oil. Phenylalphanaphthylamine (0.175 pound) was then added and the grease finished by milling in a Manton-Gaulin homogenizer at 7000 p.s.i.g.

The greases obtained as described above were of good texture and appearance, having excellent lubricating properties including high extreme pressure properties represented by CK. loads in the Timken Test above 50, and generally above 60. Greases of this same composition which were prepared in substantially the same manner but with heating at temperatures above 400 F. had very markedly lower load bearing properties, and greases meeting the requirement of U.S. Steel Specification No. 355 for a minimum O.K. load of 40 in the Timken Test could not consistently be produced. Also, greases meeting the requirement of this specification for a 5 percent maximum loss in the Water Washout Test were not obtained when the grease mixture was heated at above 400 F.

The following table shows the extreme pressure and other properties of representative greases of the above series, and also comparatively for a representative grease prepared by the high temperature method. All of the grease preparations were carried out in substantially the same manner except for the dilference in the maximum temperature during the heat treating step, with milling or shearing so as to produce the maximum yield. Grease No. 2 of the table is that obtained in the preparation which is described in detail above. In the preparation of grease No. 3, the charge to the grease kettle also con tained 0.3 pound of an estolide of IZ-hydroxystearic acid having an average molecular weight of about 1600.

Table I Grease No 1 2 3 Composition, percent:

Ca acetate 15.0 17.2 15.0 Ca soap 6. 7. 2 6. 0 Excess Ca(OH)z 0. 5 1.0 1.0 Calcium soap at estol e of 12-hydroxystearic acid 0 0 0.5 Phenylalphanaphthylamina 0. 5 0. 5 0. 5 Mineral Oil Re- Re- Remainder mainder maiuder Ca acetate-Ca soap mol ratio- 7. 5:1 7. 3:1 7. 5 1 Preparation: T Maximum temperature, F. 500 318 357 ests:

ASTM Penetration at 77 Unworked 230 281 294 Worked, 00 strokes 298 388 346 Worked, 10,000 stro es 353 382 326 Dropping Point. F 500+ 500+ 500+ Timken Test, O.K. load, lbs. 45 75 7 Water Washout Test, D-1264,

Grease loss, percent 23. 5 3. 5 2. 5

While higher yields were obtained by the high tempera- 0 ture method, as shown by the data, this was overcome to a considerable extent in the greases of our invention by employing a small amount of estolide in the grease mixture, as shown by grease No. 3.

EXAMPLE II As an example of a grease of this invention containing a different calcium soap, a grease was prepared by the low temperature method wherein the calcium soap Was calcium 12-hydroxystearate. The lubricating oil employed in the grease was that described in Example I.

The grease preparation was carried out substantially as described in Example I, with formation of the calcium salt in situ in the saponification mass and with a heat treatment for two hours at 310320 F. following the dehydration.

The following table shows the properties of the above grease in comparison with those of a grease (grease No. 2) obtained in the same manner except that the grease mixture was heated to 500 F. The table also shows the properties of a grease prepared by the low heat procedure in the same manner except that an unsaturated fatty acid was employed as the saponifiable material (grease No. 3). The unsaturated fatty acid employed was oleic acid, having an iodine number of 86.

Table II Grease No 1 2 3 Composition:

Ca acetate 17. 5 15.0 17. 5 Ca soap 7. 2 6.0 7. 2 Excess Ca (OH); 0.8 1. 0 0. 8 Calcium soap 0! estolide of IZ-hydroxystearic acid 0.5 0.5 0. 5 Phenylalphanaphthylamine- 0.5 0. 55 0. 5 Mineral Oil Remainder Remainder Remainder Ca acetate-Ca soap mol ratio- 10:1 10:1 9:1 Preparation:

Maximum Temperature, F. 320 500 320 Tests:

ASIM Penetration at 77 F.

Unworked 202 368 246 Workerl, 60 strokes 279 373 341 Worked, 10,000 strokes. 299 294 352 Dropping Point, F 500+ 500+ 500+ Timkeu Test, 0.11. load, lbs" 40 33 As shown by the above data, the advantage 1n extreme pressure properties is also obtained by the method of this invention employing hydroxy fatty acids as the saponifiable materials, differently from the unsaturated fatty acids with which no such advantage is obtained. In addition to the excellent extreme pressure properties shown in the table, grease No. 1 met the other requirements of U5. Steel Specification No. 355, including the requirements for low water loss, good oxidation resistance and high shear stability.

In comparison with greases prepared by the method of this invention from unsubstituted fatty acids, greases prepared from hydroxy fatty acids are obtained in higher yields, but they absorb more water and undergo a larger amount of penetration change after water absorption, and they are therefore considered less desirable for use in the presence of water.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof and only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. The method of preparing an extreme pressure calcium base grease thickened with about 17-30 percent by weight of a calcium salt-calcium soap complex which comprises forming a mixture comprising a low molecular weight fatty acid material selected from the class consisting of saturated C fatty acids, their esters and calcium acid salts, and a high molecular weight fatty acid material selected from the class consisting of substantially saturated unsubstituted and hydroxy-substituted C fatty acids and C fatty acid mixtures, their esters and calcium salts, in at least a portion of the lubricating oil contained in the finished grease, adding to said mixture a basically reacting calcium compound in an amount sufiicient for converting all of the said fatty acid materials into their normal calcium salts, heating the reaction mixture for a sufficient time to complete all saponification and neutralization reactions, further heating it at an elevated temperature until at least substantial thickening has occurred, and thereafter cooling the said mixture and adding any additional lubricating oil required to obtain a grease of the desired grade, said low molecular weight fatty acid material being employed in the said reaction mixture in an amount sufficient to give a ratio of calcium low molecular weight fatty acid salt to calcium high molecular weight fatty acid soap of 7:1 to 25:1.

2. The method according to claim 1 wherein the said low molecular weight fatty acid salt is calcium acetate.

3. The method according to claim 1 wherein the said mixture is heated at a maximum temperature below about 375 F.

4. The method according to claim 1 wherein the said mixture is heated at a maximum temperature in about the range 260350 F.

5. The method according to claim 1 wherein an estolide of a hydroxy fatty acid containing -22 carbon atoms is added to the grease mixture before completion of the said saponification and neutralization reactions.

6. The method according to claim 1 wherein the said lubricating oil is a mineral lubricating oil.

7. The method of preparing an extreme pressure calcium base grease thickened with about 17-30 percent by weight of a calcium salt-calcium soap complex which comprises saponifying a high molecular weight fatty acid material selected from the class consisting of substantially saturated unsubstituted fatty acids and hydroxy substituted C fatty acids, C1248 fatty acid mixtures and esters thereof with a basically reacting calcium compound in the presence of at least a portion of the lubricating oil contained in the finished grease, adding a saturated C fatty acid and any additional basically reacting calcium compound required for the neutralization of the said C fatty acid to the saponification mixture after at least partial saponification of the said high molecular weight fatty acid material has occurred, dehydrating the grease mixture obtained, heating it at a temperature in about the range 260-350" F. until at least substantial thickening has occurred, and thereafter cooling the grease mixture and adding any additional lubricating oil required to give a grease of the desired grade, said C fatty acid being added to the saponification mixture in an amount sufficient to give a ratio of calcium low molecular weight fatty acid salt to calcium high molecular weight fatty acid soap of 7:1 to 25:1 in the grease.

8. The method according to claim 7 wherein an estolide of a hydroxy fatty acid containing 1022 carbon atoms is added to the grease mixture before completion of the said saponification and neutralization reactions.

9. A calcium base grease having superior extreme pressure properties represented by an OK. load in the Timken Test above 50, consisting essentially of a lubricating oil as the chief component thickened to a grease consistency with a complex mixture of 13-24 percent by weight, based on the weight of the grease, of calcium acetate and 4-10 percent by weight, based on the weight of the grease, of a calcium soap selected from the group consisting of calcium soaps of unsubstituted fatty acids and hydroxy substituted fatty acids containing 12-18 carbon atoms, and mixtures thereof, said calcium salt and said calcium soap being in a mol ratio between about 7:1 and 20:1 respectively, said grease being heated during the preparation thereof at an elevated temperature of at least 255 F. but below 400 F.

10. A lubricating grease according to claim 9 containing about 0.1-2.5 percent by weight of a material selected from the class consisting of calcium soaps of estolides of hydroxy fatty acids containing 10-22 carbon atoms.

11. A lubricating grease according to claim 9 which has been heated during the preparation thereof at a maximum temperature below about 350 F.

12. A lubricating grease according to claim 9 containing 14-22 percent by weight of said calcium salt and 4-8 percent by weight of said calcium soap.

13. A lubricating grease according to claim 9 wherein the said lubricating oil is a mineral oil.

14. A lubricating grease according to claim 9 wherein the said calcium salt and said calcium soap are present in a mol ratio between about 7:1 and about 20:1.

15. A process for preparing complex calcium salt-calcium soap thickened greases wherein the mol ratio of calcium salt to calcium soap is between 7:1 and :1 which comprises saponifying a mixture of coconut fatty acid, an estolide of the hydroxy fatty acid containing 10-24 carbon atoms and a compound selected from the group consisting of an aliphatic monocarboxylic acid containing l-3 carbon atoms and an acid salt thereof in a lubricating oil with a basic reacting calcium compound, subjecting the saponified reaction mixture to heat treatment at a temperature between 255 and 325 F. to effect dehydration of the reaction mixture and formation of the calcium salt-calcium soap complex and cooling said dehydrated reaction mixture to form a complex calcium saltcalcium soap thickened grease characterized by low wear, storage stability, shear stability and water resistance.

References Cited in the file of this patent UNITED STATES PATENTS 2,862,884 Dilworth et al Dec. 2, 1958 2,877,181 Dilworth et al. Mar. 10, 1959 2,898,297 Schott et al. Aug. 4, 1959 2,973,321 Morway et al. Feb. 28, 1961 FOREIGN PATENTS 785,509 Great Britain Oct. 30, 1957 789,855 Great Britain Jan. 29, 1958 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,068, 173 December 11 1962 James R. Roach et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column l line 55, for "results" read result column 2 lines 20 and 21, for "substantion" read substantial line 26, for "aicd" read acid column 5, Table I, under the heading "Grease N09", line 5, for "at" read of column 6, Table 11, under the heading "2" third line from the bottom for "294" read 394 column' 6, line 59, after "temperature" insert of at least 255 F, but below 400 F. B

Signed and sealed this 11th day of June 1963 (SEAL) Attest:

ERNEST w. SWIDER DAVID D Attesting Officer Commissioner of Patents UNITED STATESPATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3,068,173 December ll, 1962 James R. Roach et a1.

Column 1, line 55, for "results" read result column 2, lines 20 and 21, for "substantion" read substantial line 26, for "aicd" read acid column 5, Table I, under the heading Grease N06", line 5, for "at" read of column 6, Table II, under the heading "2", third line from the bottom, for "294" read 394 column' 6, line 59, after "temperature" insert of at least 255 IE, but below 400 F.

Signed and sealed this llth day of June 1963,,

(SEAL) Attest ERNEST w. SWIDER DAVID D Attesting Officer Commissioner of Patents

Claims

1. THE METHOD OF PREPARING AN EXTREME PRESSURE CALCIUM BASE GREASE THICKENED WITH ABOUT 17-30 PERCENT BY WEIGHT OF A CALCIUM SALT-CALCIUM SOAP COMPLEX WHICH COMPRISES FORMING A MIXTURE COMPRISING A LOW MOLECULAR WEIGHT FATTY ACID MATERIAL SELECTED FROM THE CLASS CONSISTING OF SATURATED C1-3 FATTY ACIDS, THEIR ESTERS AND CALCIUM ACID SALTS, AND A HIGH MOLECULAR WEIGHT FATTY ACID MATERIAL SELECTED FROM THE CLASS CONSISTING OF SUBSTANTIALLY SATURATED UNSUBSTITUTED AND HYDROXY-SUBSTITUTED C18 FATTY ACIDS AND C12-18 FATTY ACID MIXTURES, THEIR ESTERS AND CALCIUM SALTS, IN AT LEAST A PORTION OF THE LUBRICATING OIL CONTAINED IN THE FINISHED GREASE, ADDING TO SAID MIXTURE A BASICALLY REACTING CALCIUM COMPOUND IN AN AMOUNT SUFFICIENT FOR CONVERTING ALL OF THE SAID FATTY ACID MATERIALS INTO THEIR NORMAL CALCIUM SALTS, HEATING THE REACTION MIXTURE FOR A SUFFICIENT TIME TO COMPLETE ALL SAPONFICATION AND NEUTRALIZATION REACTIONS, FURTHER HEATING IT AT AN ELEVATED TEMPERATURE UNTIL AT LEAST SUBSTANTIAL THICKENING HAS OCCURED, AND THEREAFTER COOLING THE SAID MIXTURE AND ADDING ANY ADDITION AL LUBRICATING OIL REQUIRED TO OBTAIN A GREASE OF THE DESIRED GRADE, SAID LOW MOELCULAR WEIGHT FATTY ACID MATERIAL BEING EMPLOYED IN THE SAID REACTION MIXTURE IN AN AMOUNT SUFFICIENT TO GIVE A RATIO OF CALCIUM LOW MOLEUCLAR WEIGHT FATTY ACID SALT TO CALCIUM HIGH MOLECULAR WEIGHT FATTY ACID SOAP OF 7:1 TO 25:1.