US 3929651 A
A grease composition that combines good water resistance, good mechanical stability and high oil retention with excellent oxidation stability and high dropping point is prepared by the use of a novel thickener system whose essential components include a combination of dilithium salt of a C4-C12 dicarboxylic acid, e.g. dilithium azelate; a lithium soap of a 9-, 10-, or 12-hydroxy C12 to C24 fatty acid, e.g. lithium 12-hydroxy-stearate; and a lithium salt formed in situ in the grease from a second hydroxy carboxylic acid wherein the OH group is attached to a carbon atom not more than 6 carbon atoms removed from the carboxyl group, and wherein either of those groups may be attached to either aliphatic or aromatic portions of a molecule. If desired, sufficient lithium hydroxide can be added to form the dilithium salt of the latter acid through reaction of its hydroxyl group.
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Description (OCR text may contain errors)
United States Patent Murray et al.
[ Dec. 30, 1975  MODIFIED LITHIUM SOAP GREASE  Inventors: Donald W. Murray, Sarnia; Warren C. Pattenden, Mooretown, both of Canada  Assignee: Exxon Research & Engineering Co.,
221 Filed: Sept. 25, 1974  Appl. No.: 509,231
Related US. Application Data  Continuation of Ser. No. 90,877, Nov. 18, 1970,
abandoned  US. Cl ..252/41  Int. Cl C10M I/24;C10M 3/18;C10M 5/14; C10M 7/20  Field of Search 252/41  References Cited UNITED STATES PATENTS 2,951,808 9/1960 Norton et a1. 252/41 3,223,624 12/1965 Morway et al 252/41 3,223,633 12/1965 Morway et al 252/41 3,711,407 1/1973 Plumstead 252/41 Primary Examiner-Delbert E. Gantz Assistant Examiner-l. Vaughn Attorney, Agent, or Firm-Byron O. Dimmick  ABSTRACT A grease composition that combines good water resistance, good mechanical stability and high oil retention with excellent oxidation stability and high dropping point is prepared by the use of a novel thickener system whose essential components include a combination of dilithium salt of a C C dicarboxylic acid, eg dilithium azelate; a lithium soap of a 9-, 10-, or 12- hydroxy C to C fatty acid, e.g. lithium IZ-hydroxystearate; and a lithium salt formed in situ in the grease from a second hydroxy carboxylic acid wherein the OH group is attached to a carbon atom not more than 6 carbon atoms removed from the carboxyl group, and wherein either of those groups may be attached to either aliphatic or aromatic portions of a molecule. If desired, sufficient lithiumhydroxide can be added to form the dilithium salt of the latter acid through reaction of its hydroxyl group.
8 Claims, No Drawings MODIFIED LITHIUM SOAP GREASE BACKGROUND OF THE INVENTION 2 tendency of such greases to undergo surface hardening onstanding. i
The hydroxy 'fatty acid employed in preparing the greases of this invention will have from about 12 to 24, or more usually about 16 to carbon atoms, and still preferably be a hydroxy-stearic acid, e.g. 9-hydroxy, 10-hydroxy, or 12-hydroxystearic acid, more preferably the latter. Ricinoleic acid, which is an unsaturated form of l2-hydroxystearic acid, having a double bond in the 9-10 position, can also be used.
The dicarboxylic acid used in the greases of this invention will have from 4 to 12 carbon atoms, preferably 6 to 10 carbon atoms. Such acids include succinic, glutaric, adipic, suberic, pimelic, azelaic, dodecanedioic, and sebacic acids. Sebacic acid and azelaic acid are preferred.
greases have been high water resistance and ease of dispersion of the soaps in all types of lubricating oil base stocks. Particularly useful have been greases pre- 7 pared from lithium hydroxystearate, since the soaps of the hydroxystearic acids and related hydroxy fatty acids have been found to be more mechanically stable than the corresponding soaps of the conventional fatty acids.
There are many fields of application of grease compositions where a high dropping point is required, as for example in the lubrication of traction motor bearings. Such traction motors are used to propel modern diesel locomotives. The engines of the diesel locomotives generate direct current which is then used to run traction motors which are geared directly to the driving axle and wheel assemblies in each truck of the locomotive. A single traction motor may contribute 200 horsepower, and constitute 1/10 or more of the total motor power of the locomotive. The bearings of these locomotives may be required to operate for periods of as much as three years without any maintenance, and temperatures as high as 250F. can be reached in such bearings.
DESCRIPTION OF THE INVENTION In accordance with the present invention, a lithium base grease having excellent oxidation and mechanical stability and a dropping point of 500F. or higher is prepared from a 9-hydroxy, 10-hydroxy, or l2-hydroxy C to C preferably C to C fatty acid, a C to C dicarboxylic acid, and a second hydroxy carboxylic acid of from 3 to 14 carbon atoms, wherein the hydroxy group is attached not more than 6 carbon atoms removed from the carboxyl group.
It has already been taught in U.S. Pat. No. 2,940,930 that high droppingpoint greases (500F. or greater) can be prepared from mixturesof monocarboxylic and dicarboxylic acids. However, in preparing the greases described in that patent, it was necessary to also include a glycol. The presence of a glycol is undesirable because it renders the grease prone to oxidation and makes the water resistance of the grease undesirably low in some applications. The present invention makes possible the preparation of high dropping point greases from a combination of hydroxy fatty acid and dicarboxylic aliphatic acid without the necessity of incorporating a glycol.
While U.S. Pat. Nos; 3,223,633and 3,223,624 teach the preparation of high dropping point greases from a 3-compo'nent mixture of acids, the presence of a C, to C fatty acid salt, which is an essential component of those greases, is frequently undesirable because of the The hydroxy carboxylic acid forming the third acid component of the grease of this invention is one having an OH group attached to a carbon atom that is not more than 6 carbon atoms removed from the carboxyl group. This acid has from 3 to 14 carbon atoms and can be either an aliphatic acid such as lactic acid, 6- hydroxy decanoic acid, 3-hydroxybutanoic acid, 4- hydroxybutanoic acid, etc. or an aromatic acid such as parahydroxybenzoic acid, salicylic acid, 2-hydroxy-4- hexylbenzoic acid, meta hydroxybenzoic acid, 2,5- dihydroxybenzoic acid (gentisic acid); 2,6-dihydroxybenzoic acid (gamma resorcylic acid); 4-hydroxy-3- methoxybenzoic acid, etc. or a hydroxyaromatic aliphatic acid such as orthohydroxyphenyl, metahydroxyphenyl, or parahydroxyphenyl acetic acid. A cycloaliphatic hydroxy acid such as hydroxy cyclopentyl carboxylic acid or hydroxynaphthenic acid could also be used.
In place of the free hydroxy acid of the latter type when preparing the grease, one can use a lower alcohol ester, e.g. the methyl, ethyl, or propyl, isopropyl or sec-butyl ester of the acid, e. g. methyl salicylate, to give a better dispersion when the salt is insoluble. The
amount of dilithium salt of the hydroxy acid will range from about 0.1 to about 10 wt. of the finished grease, or preferably from about 0.5 to about5 wt.
The total soap and salt content of the grease will be in the range of from about 2 to 30 weight percent and preferably about 5 to 20 weight The proportion of the C to C hydroxy fatty acid to the dicarboxylic acid will be in the range of 0.5 to 15 parts by weight of the former to one part by weight of the latter, and preferably in the range of 1.5 to 5 parts by weight of the hydroxy fatty acid to one part by weight of the dicarboxylic acid. The proportion of the second hydroxycarboxylic acid to the dicarboxylic acid will be from about 0.025 to 2.5 parts by weight of the former to one part by weight of the latter, preferably 0.125 to 1.25 parts by weight of the former per part by weight of the latter.
The lubricating oil base that is used in preparing the grease compositions of this invention can be any of the conventionally used mineral oils, synthetic hydrocarbon oils, or synthetic ester oils, and will generally have a viscosity within the range of about 35 to 200 SUS at 210F. Synthetic lubricating oils that can be used include esters of dibasic acids such as di-2-ethylhexyl sebacate, esters of glycols such as the C Oxo acid diester of tetraethylene glycol, or complex esters such as a complex ester formed by reacting one mole of sebacic acid with two moles of tetraethylene glycol and two moles of 2-ethylhexanoic acid. Other synthetic oils thatcan be used include synthetic hydrocarbons such as alkyl benzenes, e.g. alkylate bottoms from. the alkylation of benzene with tetrapropylene, or the .copoly mers of ethylene and propylene; silicone oils,.e.g. ethyl phenyl polysiloxanes, methyl polysiloxanes, etc.; polyglycol oils, e.g. those obtained by condensing butyl alcohol with propylene oxide; carbonate esters, e.g. the product of reacting C Oxo alcohol with ethyl carbonate to form a half ester followed by reaction on the latter with tetraethylene glycol, etc. Other suitable synthetic oils include the polyphenyl ethers, e.g. those having from about 3 to 7 ether linkages and about 4 to 8 phenyl groups.'(See U.S. Pat. No; 3,424,678, column 3 The greasesof this invention can be formed in a number of different ways. One convenient way when the third acid is salicylic acid is to co-neutralize the hydroxy fatty acid and the dicarboxylic acid in at least a portion of the oil with lithium hydroxide. This neutralization will take place at a temperature in the range of about 180 to 220F. When the soap stock has thickened to a heavy consistency, the temperature is raised to about 260 to 300F. to bring about dehydration. The soap stock is then cooled to about 190 to 2l0F. and the ester of salicylic acid is added; then, additional lithium hydroxide is added gradually to convert the salicylate ester to the dilithium salicylate salt. Reaction is conducted at about 220 to 240F., preferably with agitation so as to facilitate the reaction. In this reaction, the alcohol is evolved, and dilithium salicylate forms. Dehydration is then completed at 300 to 320F. after which the grease is heated at 380390 F. for minutes to improve its yield and is then cooled while additional oil is added to obtain the desired consistency. Alternatively, the additional oil can be added to the soap'concentrate prior to the in situ-formation in the dilithium salicylate.
An alternative method is to co-neutralize all three types of acid used in making the grease, or to saponify a lower ester of the second type of hydroxy acid, e.g. methyl salicylate, simultaneously with the neutralization of the hydroxy'acid of the first type, e.g. hydroxystearic acid and the dicarboxylic acid. Still another alternative is to co-neutralize the hydroxy fatty acid and the ester of the second hydroxy acid, followed by neutralization of the dicarboxylic acid.
The following examples, which include a preferred embodiment, are presented to illustrate the preparation and various characteristics of greases manufactured according to this invention. Comparative examples are also included to show that adverse or inferior results are obtained if components outside the scope of the invention are used. I
EXAMPLE I This example illustrates the preparation of a grease of this invention on a plant scale in a 1000 lb. kettle. The
ingredients used and their proportions are given in the following Table l.
TABLE I Weight(lb) per 100 lb Finished Base Grease Lubricating Oil Weight (lb) per 100 lb Finished Base Grease Ingredient "Mixture of solvent refined and dewaxed paraffinic distillates, hydrofinished, having a viscosity of 520 SUS at I00F. and a V.l. of 93.
"450 lb of water and methanol are formed through reaction of the base with the fatty acids and methyl salicylate. These are lost during the dehydration cycle, leaving a net yield of 100 lb of finished base grease.
"This portion of the Li0H.H,O required to neutralize the lZ-hydroxystearic and azelaic acids only.
"l'his portion of the LiOl-l.H,O required to react with the methyl salicylate to produce dilithium salicylate.
The l2-hydroxystearic acid and the azelaic acid were charged to the kettle with about 55 weight of the baseoil, and the mixture was heated at l200F. until the carboxylic acids had dissolved. Then while the kettle temperature was maintained at 200 to 205F., a hot saturated aqueous solution containing sufficient lithium hydroxide to react with the hydroxystearic acid and the azelaic acid was added gradually over a period of one hour. When the soap stock had thickened to a heavy consistency, the temperature was raised to about 270F. as quickly as the dehydration process would permit. When dehydration was essentially complete, as indicated by a rapid increase in temperature to 300F., the soap stock was cooled to 200F. by circulating cold water through the jacket of the kettle; then the methyl salicylate was added and mixed with-the soap stock at 200F; Following this the remainder of the lithium hydroxide monohydrate (1.55 lbs per lbs of the finished grease) was added very gradually as a hot saturated solution. At this stage the heat input and mixing rate were increased to speed up the dehydration process (conducted at 212 275F.) and to avoid accumulation of free water in the kettle.- When all of the lithium hydroxide solution had been added and dehydration was complete as noted bya' rapid increase in temperature, the entire mass of grease was heated to a temperature of 385F. and maintained there for 15 minutes to improve the grease structure. The grease mixture was then rapidly cooled to about 300F. by circulating cold water through the jacket of the kettle and while adding a small amount of oil. .After the temperature had been reduced to less than 300F., the remaining oil was blended into the grease while it cooled gradually. After the base grease had been cooled to a temperature of between and 200F. it
was passed through a 100 mesh screen to complete its preparation. The product was a smooth uniform grease, beige in color, with an unworked penetration of 230 at 77F. The worked penetration of this base grease at 77F. was 230 after 60 strokes, 240 after 10,000 strokes and 251 after 100,000 strokes.
EXAMPLE 2 To prepare a grease suitable for lubrication of locomotive traction motor bearing the base grease of Examdilithium salicylate, identified as DLS grease. The conventional lithium hydroxystearate grease was a commercial product containing lithium l2-hydroxystearate as the only thickener. The grease DLS also had lithium l2-hydroxystearate as the only thickener but it additionally contained 3 weight percent of finely ground preformed dilithium salicylate powder as an antioxidant. See US. Pat. No. 2,951,808.
lower viscosity oil (90 V.I., 200 SUS at 100F.) with a calcium-lithium 12-hydr0xy stearate soap mixture. The comparison is shown in Table IV. Taking into account the viscosity of the oil used, the grease of Example 3 is considered to have excellent torque properties.
TABLE IV ASTM D-1478 TORQUE (g. cm. at 40F.)
l 0 Starting Running These three greases are compared in Table II, which Example 3 Grease 8300 2360 follows. Commercial Ca-Li Grease 10,400 3000 TABLE I1 COMPARISON OF PROPERTIES OF GREASES Conventional Example 2 Lithium Hydroxy- Product stearate Grease DLS Grease Oil Content, Wt.% 80.1 86 82.1 Oil Viscosity, SUS at 100F. 520 485 520 ASTM Worked Penetration, 77F., 60Strokes 248 253 234 5,000strokes 265 250 10,000Strokes 265 250 100,000Strokes 277 264 304 ASTM Roller, 100 Hr. at 160 rpm A ASTM Pen. (77F.)/Adhesion: 77F. +28/OK +38/OK +l/OK 150F. +53/OK Water Absorption in ASTM Roller H O Absorbed/A ASTM Pen. (77F.)/Adhesion: 77F. 54/+12/OK 66/+l08/OK 150F. 5 8/+44/OK 67l+76lOK 36/+92/OK ASTM Dropping Point, F. 500+ 394 370 ASTM Wheel Bearing, 6 Hr. at 200F. Leakage, g/Slump 1.1/Ni1 0.7/Nil 0.9/Nil Oil Separation, Hr. at 212F., Wt.% 1.9 1.1 3.9 NLGT Spindle Life, 10,000 rpm, 300F., Hr. 2.388 288 1,566 ASTM Bomb Oxidation, 210F. Pressure Loss, psig, after: 100 Hr. 1.5 5.0 2.5
500 Hr. 5.0 10.0 11.5 ASTM D 1743 Rust Test Pass Fail Copper Corrosion Test, 24 Hr. at 212F. Pass Fail Pass ASTM D-l263-53T It is to be noted that the grease of Example 2 had a dropping point of over 500F. as compared with 394F. for the conventional lithium hydroxystearate grease EXAMPLE 4 and 370F. for the grease into which powdered dilithium salicylate had been incorporated.
EXAMPLE 3 Using the procedure of Examples 1 and 2, a grease similar to that of Example 2, but using a lower viscosity oil (250 SUS at 100F. and 90 v.1. was prepared. The composition of this grease, on the basis of weight percent of reactants, is given in Table 111.
TABLE I11 Wt. Mineral Oil, 90 V.1., 250 SUS at 100F. 81.01 l2-Hydroxystearic acid 8.77 Azelaic acid 2.67 Methyl salicylate 1.09 Lithium hydroxide monohydrate 3.21 NaSul BSN (rust inhibitor) 1.75 Phenyl a-naphthylamine (oxidation) inhibitor) 0.50 Pour depressant 1.00
Oil concentrate, 20% active ingredient, of 2 parts wax-alkylated naphthalene and 1 part C.C,, alkyl methacrylate polymer.
(Base Grease Preparation) This example describes the preparation of a base grease using a mole ratio of 1 mole of hydroxystearic acid, and 0.75 mole of azelaic acid, first forming a soap concentrate and then a grease. Into 300 grams of v.1. mineral lubricating oil having a viscosity at F. of 550 SUS there were dispersed 92 grams of 12- hydrostearic acid and 43.2 grams of azelaic acid at a temperature of 200F. Then 31.7 grams of lithium hydroxide hydrate (LiOl-LH O) was added and the reaction was continued at 200240F., after which the reaction product was dehydrated by heating it to 300F. The free alkali content of the dehydrated product was 0.18%, which indicated that neutralization of all of the carboxyl groups was essentially complete. The temperature of the dehydrated product was raised to 390400F. for 30 minutes in order to improve the dispersion. The soap concentrate product was then cooled while additional oil was added to give the desired consistency. This product is identified as a base grease in the accompanying Table V.
EXAMPLE 5 identified in the accompanying Table V as Grease A.
8 except that the dilithium salicylate was added to the base grease as. a fine preformed powder (all particles less than 150 microns in size) rather than being formed in situ in the grease. The resulting comparative grease was of substantially the same consistency as Grease D (ASTM penetration 300) but it had a dropping point of only 374F and had a life of only 175 hours in the Static EXAMPLE 6 Oxidation Test.
TABLE V GR AS PROPERTIES OF LITHIUM HYDROXYSTEARATE-DILITHIUM AZELATE GREASES E E Composition, Parts by Weight Base Grease A D E Lithium l2-hydroxystearate 93.6 93.6 93.6 102.0 Dilithium Azelate 45.9 45.9 45.9 Mineral Oil, 90 V.l., 550 SUS at 100F. 917.0 830.5 917.0 885.0 Dilithium Salicylate (3%), made in situ 30.0 32.7 V 31.0 via methyl salicylate 1056.5 1000.0 1089.2 1018.0 DLS Particle Size None Fine Fine Coarse ASTM Penetration, 77F., mm/l0'. 60 Strokes 291 305 304 248 100,000 Strokes 335 ASTM Dropping Point, F. 390 525 500+ 385 Static Oxidation Test, 350F., hours to 80 280 295 35% weight loss Water Resistance in ASTM Roller, 150F. 78l+32 H O Absorbed/ASTM Penetration Change, 77F. Oil Separation, Federal Test method, hr. 2.7 2l2F., Wt. ASTM Wheel Bearings, 6 hr. at 220F., Leakage 0.6/Nil 1.6/Nil in grams/slump A second grease was prepared by starting with the base grease of Example 4 rather than with the soap concentrate. Methyl salicylate and lithium hydroxide monohydrate were reacted in the base grease at 220F. in the same manner as described for the preparation of Grease A, Example 5. The difference was that the methyl salicylate and lithium hydroxide were reacted in the finished base grease rather than in the soap concentrate. The product that was obtained was identified as Grease D.
COMPARATIVE EXAMPLE l The effect of omitting the dicarboxylic acid soaps from the grease was determined by preparing a grease similar to greases A and D omitting the dilithium azelate. The grease is identified as Grease E.
The properties of the base grease and of greases A, D and E are given in Table V which follows. Greases A and D both have a mole ratio of 1 mole of hydroxystearic acid, 0.75 mole of azelaic acid, and about 0.7 mole of salicylic acid. The data obtained with grease E show that the presence of the dicarboxylic acid soap is necessary in order to obtain a satisfactorily fine dilithium salicylate in the grease as well as to insure that the grease will have a dropping point of at least 500F.
COMPARATIVE EXAMPLE IA The formulation of Grease D was repeated, using the same amounts of each component as for that grease,
The static oxidation test for which-data are given in Table V was conducted in the following manner. Five grams of the grease being tested was packed into an open ball bearing of known weight which was then hung in an oven maintained at 350F. At periodic intervals the bearing was removed from the oven, and weighed again to determine weight loss of the grease. The results were reported in terms of the number of hours for a 35% weight loss.
EXAMPLE 7 Using the same general procedure as described in Example 1, several grease formulationswere made in which, in one instance, lower mole ratios of dibasic acid and methyl salicylate were used (Grease F), and in other instances a C or a C dibasic acid was used in place of azelaic acid (Greases G and H). The formulations of these greases and their properties are given in accompanying Table VI. An additional grease formulation (Grease I) wherein stearic acid was employed instead of hydroxystearic acid resulted in a fluid product containing undispersed soap rather than a grease. Formulation J shows that a high dropping point grease can also be obtained by forming dilithium salicylate in situ from salicylic acid instead of methyl salicylate.
The data for greases G and H show that sebacic acid can be satisfactorily used in place of azelaic acid but that a C acid (brassylic) did not produce a high dropping point grease.
TABLE VI PREPARATION OF LITHIUM HYDROXYSTEARATE DlLlTl-IIUM DICARBOXYLATE GREASES FORMULA Composition, Mole Ratio A F G H l J LiOl-l.l-l,0 3.83 3.10 3.94 3.83 3.35 3.0 Stearic Acid 1.0 l2-Hydroxystearic Acid 1.0 1.0 1.0 1.0 1.0 Azelaic Acid (C,) 0.75 0.55 0.75 0.55 Sebacic Acid (C 0.75 Dimethyl Brassylate (C 0.75 Methyl Salicylate 0.67 0.50 0.72 0.67 0.43 Salicylic Acid 0.50 Mineral Oil, V.l., 550 SUS at 83.1 84.9 84.0 81.0 77.4 84.5
TABLE VI-continued PREPARATION OF LITHIUM I-IYDROXYSTEARATE DILITHIUM DICARBOXYLATE GREASES FORMULA Composition, Mole Ratio A F G H I .I
ASTM Penetration, 77F. 60 Strokes, 305 317 300 317 Fluid 360 ASTM Dropping Point, F. 525 500+ 500+ 396 520l- COMPARATIVE EXAMPLE II Substituting 0.5 mole of lithium acetate for 0.5 mole of dilithium salicylate in Grease F gave a grease having a dropping point of only 420F.
COMPARATIVE EXAMPLE III A grease similar to Grease G was prepared from one mole of 12 hydroxy stearic acid, 0.75 mole of sebacic acid, and 0.80 of benzoic acid. The total amount of oil in the grease was 83.5%. The grease had an ASTM penetration of 336 at 77F. and a dropping point of 450F. This compares with a dropping point of more than 500F. for Grease G, showing that the substitution of a nonhydroxylated acid such as benzoic acid in place of a hydroxylated acid such as salicylic acid reduces the dropping point of the grease.
EXAMPLE 8 Using the procedure of Example 6 a grease was prepared in which the acids used had a mole ratio of 1 mole of l2-hydroxystearic acid, 0.75 mole of azelaic acid and 0.75 mole of parahydroxy benzoic acid. A portion of the base grease of Example 4 was heated to 180F. and then the benzoic acid was added along with sufficient lithium hydroxide to convert the acid to a dilithium salt. The mixture was then heated for one-half hour at 230F. and then dehydrated for 1 hour at 300F. The grease had a dropping point in excess of 500F. and had an ASTM penetration of 325 at 76F. (330 after 60 strokes). The total thickener content of this grease was 18.1 wt.
EXAMPLE 9 Following the procedure of Example 8, a grease was made using 0.75 mole of lactic acid instead of the parahydroxy benzoic acid. In this case, the base grease was made from an 87 V.I. oil having a viscosity of 600 SUS at 100F. rather than 550 SUS at 100F. and 90 VI The total thickener content of the grease as lithium salts was 15.3 wt. The dropping point of the grease was 515F. and the grease had a penetration of 82F. of 328 (332 after 60 strokes).
This invention is not to be limited to the specific examples given herein by way of illustration. Its scope is defined by the appended claims.
What is claimed is:
1. A lubricating grease composition of high dropping point and long oxidation life which comprises a major proportion of a lubricating oil and from about 2 to 30 weight of a thickener system whose essential components include a dilithium salt of a C.,C dicarboxylic acid, a lithium soap of a C to C hydroxy acid, and a lithium salt of a hydroxy aromatic carboxylic acid having a maximum of 14 carbon atoms, wherein the hydroxy group is attached to a carbon atom not more than 6 carbon atoms removed from the carboxyl group,
in a weight ratio of about 0.5 to 15 parts of hydroxy fatty acid per part of said dicarboxylic acid, and in a weight ratio of from about 0.025 to 2.5 parts of said hydroxy aromatic carboxylic acid per part of dicarboxylic acid, said lithium salt of hydroxy aromatic carboxylic acid having been prepared by reacting lithium base with hydroxy aromatic carboxylic acid or lower alcohol ester thereof in the presence of dilithium salt of dicarboxylic acid and lithium soap of hydroxy fatty acid.
2. Composition as defined by claim 1 wherein the proportion of C to C hdyroxy fatty acid is from about 1.5 to 5 parts by weight per part by weight of dicarboxylic acid.
3. Composition as defined by claim 1 wherein the proportion of hydroxy, aromatic carboxylic acid is from about 0.125 to 1.25 parts by weight per part by weight of dicarboxylic acid.
4. Grease composition as defined by claim 1 wherein said hydroxy aromatic carboxylic acid is salicylic acid.
5. Grease composition as defined by claim 1 wherein said hydroxy aromatic carboxylic acid is parahydroxy benzoic acid.
6. Grease composition as defined by claim 1 wherein said hydroxy fatty acid is l2-hydroxystearic acid.
7. Grease composition as defined by claim 1 wherein said dicarboxylic acid is az elaic acid.
8. Grease composition as defined by claim 1 wherein said dicarboxylic acid is sebacic acid.