United States Patent (19) 11 3,929,651 Murray et al. (45) Dec. 30, 1975 54 MODIFIED LITHIUM SOAP GREASE Primary Examiner-Delbert E. Gantz Assistant Examiner-I. Vaughn 75 Inventors: Donald W. Murray, Sarnia; Warren Attorney, Agent, or Firm-Byron O. Dimmick C. Pattenden, Mooretown, both of Canada (57) ABSTRACT 73 Assignee: Exxon Research & Engineering Co., A grease composition that combines good water resis Linden, N.J. tance, good mechanical stability and high oil retention (22 Filed: Sept. 25, 1974 with excellent oxidation stability and high dropping point is prepared by the use of a novel thickener sys (21) Appl. No.: 509,231 tem whose essential components include a combina Related U.S. Application Data tion of dilithium salt of a C-C dicarboxylic acid, e.g. 63 Continuation of Ser. No. 90,877, Nov. 18, 1970, dilithium azelate; a lithium soap of a 9-, 10-, or 12 abandoned. hydroxy C to C fatty acid, e.g. lithium 12-hydroxy stearate; and a lithium salt formed in situ in the grease 52 U.S. Cl...................................................... 252/41 from a second hydroxy carboxylic acid wherein the 51) Int. Cl.". C10M 1/24; C10M 3/18; C10M 5/14; OH group is attached to a carbon atom not more than ClOM 7/20 6 carbon atoms removed from the carboxyl group, and 58 Field of Search....................................... 252/41 wherein either of those groups may be attached to ei ther aliphatic or aromatic portions of a molecule. If 56 References Cited desired, sufficient lithium hydroxide can be added to UNITED STATES PATENTS form the dilithium salt of the latter acid through reac 2,951,808 9/1960 Norton et al......................... 252/41 tion of its hydroxyl group. 3,223,624 12/1965 Morway et al..... ... 252/4 3,223,633 12/1965 Morway et al..... ... 252/41 8 Claims, No Drawings 3,711 .407 l/1973 Plumstead............................. 252/41 3,929,651 1. 2 tendency of such greases to undergo surface hardening MODIFIED LITHIUM SOAP GREASE on standing. The hydroxy fatty acid employed in preparing the BACKGROUND OF THE INVENTION greases of this invention will have from about 12 to 24, This is a continuation of application Ser. No. 90,877, or more usually about 16 to 20 carbon atoms, and still filed Nov. 18, 1970 and now abandoned. preferably be a hydroxy-stearic acid, e.g. 9-hydroxy, This invention concerns a modified lithium soap 10-hydroxy, or 12-hydroxystearic acid, more prefera grease of premium quality with outstanding properties bly the latter. Ricinoleic acid, which is an unsaturated which include a high dropping point, excellent oxida form of 12-hydroxystearic acid, having a double bond tion stability, long lubrication life and water resistance. 10 in the 9-10 position, can also be used. Lithium greases have been known and widely used The dicarboxylic acid used in the greases of this in for many years. The lithium soaps that are used as the vention will have from 4 to 12 carbon atoms, preferably thickening agents for these greases are ordinarily pre 6 to 10 carbon atoms. Such acids include succinic, pared by reaction of lithium hydroxide or other suitable glutaric, adipic, suberic, pimelic, azelaic, dodecanedi lithium base with a conventional high molecular weight 15 oic, and sebacic acids. Sebacic acid and azelaic acid are acid or acids. The principal advantages of lithium preferred. greases have been high water resistance and ease of The hydroxy carboxylic acid forming the third acid dispersion of the soaps in all types of lubricating oil component of the grease of this invention is one having base stocks. Particularly useful have been greases pre an OH group attached to a carbon atom that is not pared from lithium hydroxystearate, since the soaps of 20 more than 6 carbon atoms removed from the carboxyl the hydroxystearic acids and related hydroxy fatty group. This acid has from 3 to 14 carbon atoms and can acids have been found to be more mechanically stable be either an aliphatic acid such as lactic acid, 6 than the corresponding soaps of the conventional fatty hydroxy decanoic acid, 3-hydroxybutanoic acid, 4 acids. hydroxybutanoic acid, etc. or an aromatic acid such as There are many fields of application of grease com 25 parahydroxybenzoic acid, salicylic acid, 2-hydroxy-4- positions where a high dropping point is required, as for hexylbenzoic acid, meta hydroxybenzoic acid, 2,5- example in the lubrication of traction motor bearings. dihydroxybenzoic acid (gentisic acid); 2,6-dihydrox Such traction motors are used to propel modern diesel ybenzoic acid (gamma resorcylic acid), 4-hydroxy-3- locomotives. The engines of the diesel locomotives methoxybenzoic acid, etc. or a hydroxyaromatic ali generate direct current which is then used to run trac 30 phatic acid such as orthohydroxyphenyl, metahydrox tion motors which are geared directly to the driving yphenyl, or parahydroxyphenyl acetic acid. A cycloali axle and wheel assemblies in each truck of the locomo phatic hydroxy acid such as hydroxy cyclopentyl car tive. A single traction motor may contribute 200 horse boxylic acid or hydroxynaphthenic acid could also be power, and constitute 1/10 or more of the total motor used. power of the locomotive. The bearings of these loco 35 In place of the free hydroxy acid of the latter type motives may be required to operate for periods of as when preparing the grease, one can use a lower alcohol much as three years without any maintenance, and ester, e.g. the methyl, ethyl, or propyl, isopropyl or temperatures as high as 250F. can be reached in such sec-butyl ester of the acid, e.g. methyl salicylate, to give bearings. a better dispersion when the salt is insoluble. The 40 amount of dilithium salt of the hydroxy acid will range DESCRIPTION OF THE INVENTION from about 0.1 to about 10 wt.% of the finished grease, In accordance with the present invention, a lithium or preferably from about 0.5 to about 5 wt.%. base grease having excellent oxidation and mechanical The total soap and salt content of the grease will be stability and a dropping point of 500F. or higher is in the range of from about 2 to 30 weight percent and prepared from a 9-hydroxy, 10-hydroxy, or 12-hydroxy 45 preferably about 5 to 20 weight %. The proportion of C1 to C2, preferably Cie to Cao, fatty acid, a C to C12 the C to Ca hydroxy fatty acid to the dicarboxylic dicarboxylic acid, and a second hydroxy carboxylic acid will be in the range of 0.5 to 15 parts by weight of acid of from 3 to 14 carbon atoms, wherein the hydroxy the former to one part by weight of the latter, and group is attached not more than 6 carbon atoms re preferably in the range of 1.5 to 5 parts by weight of the moved from the carboxyl group. 50 hydroxy fatty acid to one part by weight of the dicar It has already been taught in U.S. Pat. No. 2,940,930 boxylic acid. The proportion of the second hydroxycar that high dropping point greases (500F. or greater) boxylic acid to the dicarboxylic acid will be from about can be prepared from mixtures of monocarboxylic and 0.025 to 2.5 parts by weight of the former to one part dicarboxylic acids. However, in preparing the greases by weight of the latter, preferably 0.125 to 1.25 parts described in that patent, it was necessary to also in 55 by weight of the former per part by weight of the latter. clude a glycol. The presence of a glycol is undesirable The lubricating oil base that is used in preparing the because it renders the grease prone to oxidation and grease compositions of this invention can be any of the makes the water resistance of the grease undesirably conventionally used mineral oils, synthetic hydrocar low in some applications. The present invention makes bon oils, or synthetic ester oils, and will generally have possible the preparation of high dropping point greases 60 a viscosity within the range of about 35 to 200 SUS at from a combination of hydroxy fatty acid and dicarbox 210°F. Synthetic lubricating oils that can be used in ylic aliphatic acid without the necessity of incorporat clude esters of dibasic acids such as di-2-ethylhexyl ing a glycol. sebacate, esters of glycols such as the Cia Oxo acid While U.S. Pat. Nos. 3,223,633 and 3,223,624 teach diester of tetraethylene glycol, or complex esters such the preparation of high dropping point greases from a 65 as a complex ester formed by reacting one mole of 3-component mixture of acids, the presence of a C, to sebacic acid with two moles of tetraethylene glycol and C fatty acid salt, which is an essential component of two moles of 2-ethylhexanoic acid. Other synthetic oils those greases, is frequently undesirable because of the that can be used include synthetic hydrocarbons such H 3,929,651 3 4 as alkylbenzenes, e.g. alkylate bottoms from the alky TABLE I-continued lation of benzene with tetrapropylene, or the copoly Weight (1b) per 100 lb mers of ethylene and propylene; silicone oils, e.g. ethyl Ingredient Finished Base Grease phenyl polysiloxanes, methyl polysiloxanes, etc.; poly 104.500 glycol oils, e.g. those obtained by condensing butyl "Mixture of solvent refined and dewaxed paraffinic distiliates, hydrofinished, alcohol with propylene oxide; carbonate esters, e.g. the having a viscosity of 520 SUS at 100°F. and a V.I. of 93. product of reacting Cs Oxo alcohol with ethyl carbon '4.50 lb of water and methanol are formed through reaction of the base with the fatty acids and methyl salicylate.