US3009878A - Lubricating greases prepared from epoxy fatty acid materials - Google Patents

Description

Unite States atent O No Drawing. Filed July 12, D54, Ser. No. 442,910 14 Claims. (Cl. 252-41) The present invention relates to lubricating greases containing soaps of epoxy fatty acids.

I have found that saponifiable epoxy fatty acid materials may be employed very successfully in the preparation of lubricating greases, either as the sole sapon'ifiable material or in admixture with other saponifiable materials of conventional types, and that lubricating greases may be prepared in this manner having very superior shear resistance and other special properties.

The saponifiable epoxy fatty acid materials which are employed in accordance with this invention are obtained by treating unsaturated fatty materials comprising unsaturated high molecular weight fatty acids or the esters thereof with certain oxidizing agents such as perbenzoic and peracetic acids, which results in the addition of an oxygen atom at the olefinic double bonds, forming the oxirane ring t a I I The reaction product contains one or more oxirane rings per molecule, depending upon the degree of unsaturation of the starting material, and in addition some hydroxy groups may be introduced by an opening of some of the oxirane rings during the reaction, particularly when an unsaturated oil containing more than one olefinic double bond per molecule is employed as the starting material. Suitable starting materials for the epoxidation reaction are unsaturated fatty acids containing at least 12 carbon atoms, such as from 12 to about 32 carbon atoms per molecule, and one or more olefinic double bonds, usually from 1 to about 3 olefinic double bonds, per molecule, and the glycerides or other esters of such acids. They may be employed either in relatively pure form or in naturally occurring mixtures with each other and with "minor proportions of saturated fatty acids and their esters derived from animal, vegetable or marine oils, such as, for example, lard oil, cottonseed oil, linseed oil, castor oil, menhaden oil, whale oil, etc. The preferred starting materials are those consisting of at least a predominant proportion of unsaturated fatty acids containing from about 16 to about 24 carbon atoms and either 1 or 2 olefinic double bonds per molecule, such as, for example, oleic acid, palmitolenic acid, lauroleic acid, palmitolic acids, petroselic acid, linoleic acid, eicosylenic acid, erucic acid and ricinoleic acid, and the esters of such acids.

The saponifying agent employed may be a hydroxide or other suitable compound of any of the metals ordinarily employed as the metal component of soaps in grease making, such as sodium, lithium, potassium, cal- 3,009,878 Patented Nov. 21, 196i "ice 2 and hydroxy fatty acids of the types which have been employed heretofore in grease ma ing, in a ratio of from about 1 to 3 to about 3 to l by weight, may be employed as the thickening agents.

Examples of preferred epoxy fatty acid soaps and mixtures thereof with other soaps of conventional types which may be employed include the following: lithium 9,10- epoxystearate, sodium 9,10-epoxystearate, potassium '9, IO-epoxystearate, calcium 9,1-0-epoxystearate, calcium 8, 9-epoxy-l0 hydroxystearate, aluminum 9,10-epoxystearate, lead 9,10-epoxystearate, lithium 8,9-epoxystearate, lithium 7,8-epoxystearate, sodium 4,5-epoxystearate, calcium 11,12-epoxystearate, calcium diepoxystearate, sodium 6,7-epoxymyristate, lithium 6,7-epoxymyristate, calcium 7,8-epoxymyristate, sodium 7,8-epoxypalmitate, magnesium 7,8-epoxypalmitate, lead 13,14-epoxybehenate, sodium 16,17-epoxymelissate, barium 14,15-epoxycerotate, lithium 9,10-epoxystearate and lithium stearate, lithium diepoxystearate and lithium stearate, lithium 9,10-epoxystearate and lithium IZ-hydroxystearate, lithium 9,10- epoxystearate and sodium myristate, lithium 9,10-epoxystearate and calcium stearate, calcium 9,10-epoxystearate and lithium stearate, calcium 9,10-epoxystearate and lithium 12-hydroxystearate, sodium 9,1-0-epoxystearate and calcium 9,10-epoxystearate, barium 9,l0-epoxystearate and barium stearate, barium 9,10-epoxystearate and sodium stearate, calcium 9,10-epoxyst'earate and calcium oleate, sodium 9,10-epoxystearate and lead oleate, lead 9,l0epoxystearate and lead oleate, calcium soap of 9,10- epoxystearic acid andstearic acid, calcium soap of 9,10 epoxystearic acid and 12-hydroxystea'ric acid, barium soap of 9,10-epoxystearic acid and palmitic acid, and aluminum soap of 7,8-ep'oxymyristic acid andmelissic acid.

The oleaginous liquids employed in these greases may be any suitable oils of lubricating characteristics, including the conventional mineral lubricating oils, synthetic o'ils obtained by various refinery processes such as cracking and polymerization, and other synthetic o'leaginous compounds such as high molecular weight ethers and esters. The dicarboxylic acid esters, such as di-Z-ethyl hexyl sebacate, di(secondary amyl) sebacate, di-2-ethyl hexyl azelate, di-isoctyl adipate, etc., are a particularly suitable class of synthetic oils, and may be employed as the sole oleaginous component of the grease or in combination with other synthetic oils or mineral oils. Suit 1 able mineral oils are those having viscosities in the range from about 100 to about 2,000 seconds Saybolt Universal --at 100 F., and may be either naphthenic or parafi'inic V intype, or blends ofthe two. i

The greases may also"contain various additives of the usual type such as corrosion inhibitors, oxidation inhibitors, antiwear agents, and so forth. Preferably, they contain an oxidation inhibitor which may suitably be an oxidation'inhibitorof the amine -type, such as diphenyl- 5 amine,aphenyl naphthylamine or tetramethyl diamino cium, barium, magnesium, zinc, cobalt, manganese, aluminum, lead, etc., as well as mixtures of two or more metals. It is preferably an oxide, hydroxide or carbonate -'of an alkali metal or alkaline earth metal, or a mixture of two or more such compounds or different metals selected from these groups. i The lubricating greases of this invention may suitably contain from-about 5 to about 5 0 percent by weight of an epoxy fatty acid-soap as described above, either alone or in conjunction with other thickening agents such as different fatty acid soaps. With particular advantage, soap mixtures or mixed soaps of epoxy fatty acids and of difierent fatty acids such as unsubstituted fatty acids diphenyl methane. The preparation of these greases may be carried out by any suitable grease making procedure. They are preferably prepared by the method involving saponification in situ, wherein the saponification of an epoxy fatty material or a mixture of such material with other saponifiable fatty material, as described above, is carried out [in a portion of the lubricating oil employed as the liquid base. The oil employed in the saponification is preferably a mineral oil or other oil which is not hydrolyzed under the saponification conditions. Following the saponitication, the saponification mass is heated at a higher ter'nperature to'idehydratepand the main portion of the f oleagin ous liquid base and any additives employed are -mixed in while themixture is allowed to cool.

The saponifiable epoxy fatty acid material may be prepared as described by Findley et al., I. Am. Chem. Soc.,

67, 412 (1945), by reacting a saponifiable unsaturated fatty acid material with peracetic acid in glacial acetic acid at room temperature and then diluting the reaction mixture with water. The reaction may also be carried out employing an aqueous acetic acid solution of peracetic acid, as described by Terry et al. in US. 2,458,484.

A particularly valuable application of this invention is found in the manufacture of lithium base greases, wherein it afiords both an improved product and a more convenient and economical method of preparation. Lithium soap greases of the conventional type, prepared from lithium soaps of ordinary fatty acids such as stearic acid, have certain very desirable properties such as the combination of high dropping points and good water resistance, but they are deficient in shear resistance and therefore tend to soften to an objectionable degree upon working. They have the further disadvantage that a high temperature method of manufacture'is required, wherein the lithium soap and the lubricating oil base are heated together to a high temperature above the melting point of the soap, such as about 360-500 F., and the solution then allowed to cool in open pans. This method is very undesirable because of the high temperature of operation, the special equipment required, and the lack of control over the consistency and yield of the final product.

By employing a saponifiable material comprising at least about one-third by weight of an epoxy fatty acid material as described above, the preparation may be readily carried out by the low temperature process, wherein the soap in prepared in situ in a portion of the lubricating oil base, with saponification and dehydration at temperatures below the melting point of the soap, and additional lubricating oil is added sufiicient to produce a grease of the desired consistency while the mixture is cooled down in the kettle with stirring or other agitation means. In addition, the greases obtained have excellent shear stability, in marked contrast to the conventional lithium soap greases. By employing a saponifiable material consisting of a saponifiable epoxy fatty acid material and an ordinary saponifiable fatty acid material in a ratio from about 1 to 3 to about 3 to 1, and preferably in a ratio of about 2 to 1, the preparation may be carried out by the low temperature method without difficulty, and greases are obtained having excellent shear stability as well as the desirable properties of lithium soap greases generally, including equivalent dropping points and water resistance.

A series of greases representative of this preferred embodiment was prepared employing 9,10-epoxystearic acid in the saponification.

The 9,10-epoxystearic acid employed in these preparations was obtained by the epoxidation of oleic acid with a commercial 40 percent solution of peracetic acid (Cl grade), which had been treated with 3.5 percent of sodium acetate to neutralize the small amount of sulfuric acid present. The reaction was carried out in acetic acid solution at a temperature of about 25 C. for about 4 to 6 hours, the reaction mixture then poured into an equal volume of ice water and the solid product isolated by filtration, washed thoroughly with cold water, dried, and crystallized from precipitation naphtha. A product was obtained having a melting point of about 50-57 C., .a saponification number of 187-191 and a neutralization number of 182-188. In a typical preparation, 1130 g. of oleic acid were added slowly to a solution of 775 g. of 40 percent'peracetic acid in 750 cc.

of acetic acid, while the temperature was maintained below 25 C. and the stirring and temperature control then continued until the reaction had subsided, as evidenced by the lack of heat evolution,,requiring 6 hours total reaction time. 'A product melting at 3.5-55 C. and having a saponification number of about 189 and a neutralization number of about 188 was obtained in a 47 percent yield. p

.The following examples are illustrative of the lithium base greases prepared in accordance with this invention.

Dynamic water resistance, percent loss 4 EXAMPLE 1 A grease was prepared having the following composition in percent by weight:

The mineral lubricating oil was a refined naphthene base distillate oil having an API gravity of 20.7, a flash point, COC, of 375 F., a Saybolt Universal viscosity of 312 seconds at F. and a pour point of -20 F.

The lithium soap was prepared from a 9,10-epoxystearic acid having a melting point of 53 C., a saponification number of 191 and a neutralization number of 184, obtained as described above.

The grease preparation was carried out in the following manner: A laboratory pestle-stirred grease kettle was charged with 250 g. of the 9 ,10-epoxystearic acid, 255 g. of the mineral lubricating oil, 205, g. of an aqueous 10 percent LiOH solution and 200 g. of water. This mixture was heated for 3 hours at 210 F., until the saponification was completed, and then at 310 F. for an additional hour to dehydrate, An additional 250 g. of the mineral lubricating oil was added to the saponification mass while it was at 310 F., and 250 g. more of the oil and 10 g. of phenylalphanaphthylamine were added gradu-ally while it was allowed to cool. The grease was finally drawn at 225 F.

The product obtained as described above was a smooth, buttery light brown grease. The following tests were obtained thereon:

Penetration at 77 F. worked 303 Dropping point, F 246 2 EXAMPLE H A grease was prepared having the following composition in percent by weight:

Lithium 9,10-epoxystearate 16.7

The mineral lubricating oil was the same as that described in Example I.

The lithium soaps were prepared from a mixture of 9,10 epoxystearic acid having a melting point of 54 C., a saponification number of 189 and a neutralization number of 188, prepared as described above, and a commercial stearic acid having a neutralization number of 194, a saponification number of 200 and an iodine number of 4. i

The grease preparation was carried out as described in Example I, except that the charge to the kettle consisted of 166 g. of 9,10-epoxystearic acid, 84 g. of stearic acid, 255 g. of mineral oil, 210 g. of 10 percent lithium hydroxide and 200 g. of water.

A light brown slightly stringy grease was obtained, which gave the following tests:

A grease was prepared having the following composition in percent by weight:

Lithium 9,10-epoxystearate 12.5 Lithium stearate 12.5 Mineral lubricating oil 74.0 Phenylalphanaphthylamine, 1.0

The mineral lubricating oil was the same as that described in Example I.

The lithium soaps were prepared from a mixture of Penetration at 77 F. worked 255 Dropping point, F 380 Free alkali (as LiOH) 0.53

Free fatty acid (as oleic) 0.04

Dynamic water resistance, percent loss 10 EXAMPLE IV A grease was prepared having the following composition in percent by weight:

Lithium 9,10-epoxystearate 16.4 Lithium stcarate 8.5 Mineral lubricating oil 18.6 Synthetic ester- 55.7 Phenylalphanaphthylamine 1.0

The mineral lubricating oil was a refined parafiin base distillate oil having an API gravity of 28.8, a flash point, COC, of 355 F., a Saybolt Universal viscosity of 104.5 seconds at 100 F. and a pour point of 25 F.

The synthetic ester was di-Z-ethylhexyl sebacate, sold commercially as Plexol-201. This material had a flash point, COC, of 410 F., a kinematic viscosity at 100 F.

of 1.83 centistokes, and a pour point below -65 F.

The lithium soaps were prepared from the 9,10-epoxystearic acid and stearic acid described in Example II.

The grease preparation was carried out in substantially the same manner as in the foregoing examples except that the saponification was carried out at 210 F. for 2 hours and the dehydration at 310 F. for 2 hours, and product drawn at 200 F. The charge to the kettle consisted of 158 g. of epoxystearic acid, 80 g. of stearic acid, 182 g. of mineral oil, 187 g. of 10 percent lithium hydroxide and 243 g. of water. The synthetic ester was added following the dehydration, 200 g. being added at 310 F. and the remainder (346 g.) added gradually during the cooling down process.

A uniform, buttery, slightly fibrous grease was obtained, which gave the following tests:

Penetration at 77 F. worked 273 Dropping point, F 353 Dynamic water resistance, percent loss 5 Norma-Hoffman oxidation (100 hrs. at 210 F.),

pounds pressure drop 1 The structural stability of the above greases under severe mechanical working is shown by the test results given in the following table.

Table I SHEAR STABILITY TESTS 1 Miniature penetration, by the method described in Ind. Eng. Chem., Analytical Ed, vol. 11, page 108, February 15, 1939.

Z ASTM at 77 F. (converted from size ASTM cone penetrations).

The ASTM worker test of the above table was carried out by working the grease in a standard ASTM grease worker for 100,000 strokes. The values obtained are given comparatively with the ordinary ASTM worked penetrations (60 strokes) of the greases.

The dynamic shear test measures the tendency of a grease to break down under conditions of severe working stress at elevated temperatures for prolonged periods. It is carried out at 225 F. in a test machine consisting of a perforated piston reciprocating in a closed cylinder at 49 strokes per minute for 8 hours, as described in US. 2,450,219, column 5, lines 6-19.

As shown by Table I, all of the greases of this inven tion were very stable and resistant to shear breakdown under the severe conditions of the above tests. This is in marked contrast to the experience with conventional lithium stearate greases, which ordinarily break down in these tests into liquid or semi-liquid products.

The superior stability and other lubricating properties of the greases of this invention have also been demonstrated by bearing lubrication tests, as shown by the following table.

Table II TORQUE BREAKDOWN MACHINE TEST Miniature Penetration Grease leakage, Rating percent Grease (over-all) Original from bearing Grease No. II 0 139 j 138 Good. Grease N0. III 0 72 135 Good.

The torque breakdown machine test of the above table was carried out employing a standard Federal Precision Ball Bearing No. 1211 rotated upon a motor driven shaft within a housing provided with temperature control means. The bearing was packed with about 32 g. of the test grease, weighed, and assembled upon the shaft, which was then rotated at 1750 rpm. for 3' hours, the temperature being raised gradually during the first hour from the initial temperature of F. to 250 F. and then maintained at 250 F. for the remaining two hours. Grease leakage was determined as the ditference between the original weight of the grease in the bearing and the combined weight of the grease in the bearing and in the housing at the end of the test.

As shown by the table, both of the greases representative of the invention were very satisfactory in the above test, and maintained good lubrication with no leakage and without objectionable softening, grease No. II, containing lithium epoxystearate and lithium stearate in a 2:1 ratio, being substantially unchanged in texture at the end of the test.

As an example of an epoxystearate grease of a diiferent type, a grease was prepared which consisted of 14.8 percent barium 9,10-epoxystearate, 0.6 percent phenylalphanaphthylamine and the remainder mineral lubricating oil. The preparation was carried out as described in Example I, by saponification at 210 F., dehydration at 310 F. and addition of the remainder of the oil while dropping the temperature to 200 F., employing a 9,10- epoxystearic acid and a mineral lubricating oil of the same type. The product after milling was a dark brown smooth grease having an ASTM worked penetration of 332.

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

I claim:

1. A lubricating grease composition comprising a lubricating oil thickened by a metal soap of an epoxy fatty acid.

2. The composition of claim 1 wherein the said soap is an alkali metal soap.

3. The composition of claim 1 wherein the said soap is lithium 9,10-epoxystearate.

4. A lubricating grease composition consisting essentially of a lubricating oil thickened to a grease consistency by about to 40 percent by weight of an alkali metal soap of a high molecular weight epoxy fatty acid.

5. A lubricating grease composition consisting essentially of a lubricating oil thickened to a grease consistency by a mixture of an epoxy fatty acid soap. and a fatty 'acid soap selected from the group consisting of hydroxy fatty acid soaps and unsubstituted fatty acid soaps in a proportion of from about 1 to 3 to about 3 to 1 by weight.

6. The composition of claim 5 wherein the said epoxy fatty acid soap is an alkali metal soap.

7. A lubricating grease composition consisting essentially of a lubricating oil thickened to a grease consistency by from about 5 to 40 percent by weight of a mixture of an alkali metal soap of a high molecular weight epoxy fatty acid and an alkali metal soap of a high molecular weight unsubstituted fatty acid in a proportion of from about 1 to 3 to about 3 to 1 by weight.

8. The composition of claim 7 wherein the said epoxy fatty acid is 9,10-epoxystearic acid.

9. The composition of claim 7 wherein the said alkali metal soap of a high molecular weight epoxy fatty acid is lithium 9,10-epoxystearate.

10. A lubricating grease composition consisting essentially of a lubricating oil thickened to a grease consistency by from about 5 to 40 percent by weight of a mixture of lithium 9,10-epoxystearate and lithium stearate in a proportion of about 2 to 1 by weight.

11. The method of grease preparation which comprises saponifying with a basic metal compound a saponifiable material comprising at least a substantial proportion of a high molecular weight epoxy fatty acid material in the presence of at least a portion of the mineral lubricating oil employed in the grease, dehydrating and adding any remaining lubricating oil employed in the grease.

References Cited in the file of this patent UNITED STATES PATENTS 901,905 Imbert Oct. 20, 1908 2,062,652 Hermann et al. Dec. 1, 1936 2,397,956 Fraser Apr. 9, 1946 2,434,539 Beerbower et al. Jan. 13, 1948 2,450,222 Ashburn et al. Sept. 28, 1948 2,612,473 Morway et al Sept. 30, 1952 2,629,695 Matthews et al. Feb. 24, 1953 2,651,616 Matthews et al. Sept. 8, 1953 2,690,429 Morway et a1 Sept. 28, 1954 2,712,527 Mikeska et a1. July 5, 1955 OTHER REFERENCES Oxygenated Fatty Acids, Swern, reprinted from Progress in the Chemistry of Fats and other Lipids, (1955), Pergamon Press Ltd., London, pages 217, 224 and Epoxidatiou and Hydroxylation (1955), Electrochemical Dept. E. I. du Pont de Nemours & Co., Wilmington 98, Del., 11 pages.

Fatty Acids and Their Derivatives, Ralston, Wiley and Sons, Inc., NY. (1948), p. 450.

Swern: J.A.C.S., (1948), pages 1236 and 1238. Ellis: Biochemical Journal, vol. 30, 1936, page 761. Hackhs Chemical Dictionary, 3rd. ed., page 219. The Condensed Chemical Dictionary, 5th ed., page 39, ReinholdPub. Corp, New York (1956).

Claims (1)

1. A LUBRICATING GREASE COMPOSITION COMPRISING A LUBRICATING OIL THICKENED BY A METAL SOAP OF AN EPOXY FATTY ACID.