US2878186A - Grease composition containing sodium and/or lithium soaps of low, intermediate and high molecular weight acids, together with glycerine or related hydroxy-compound - Google Patents

Description

United States Patent GREASE COMPOSITION CONTAINING SODIUM AND/ OR LITHIUM SOAPS OF LOW, INTERME- DIATE AND HIGH MOLECULAR WEIGHT ACIDS, TOGETHER WITH GLYCERINE OR RE- LATED HYDROXY-COMPOUND Clarence Liddy, New York, N. Y., assignor to Socony Mobil Oil Company, Inc., a corporation of New York No Drawing. Application April 29, 1955 Serial No. 505,064

12 Claims. (Cl. 252-42) This invention has to do with new grease compositions, particularly grease compositions characterized by a high order of effectiveness under a wide range of severe operating conditions. The novel greases contain balanced proportions of soaps of low, intermediate and high molecular weight fatty acids, together with glycerine or related hydroxy compounds.

It is well known that greases lose some or all of their effectiveness when subjected to severe operating conditions, and particularly when subjected to high temperature operations. In lubricating machine parts, for example, it is essential that a grease retain its structure during use; failure to do so results in a high consumption of the grease and frequent servicing. In general, available greases suffer from a marked tendency to change in character when used over a wide range of temperature. Some conventional greases are characterized by excessive softening when exposed to such high temperature operation, 7

thereby being extruded too rapidly from the area being lubricated to provide eflicient lubrication.

The action of water, whether salt or fresh water, may cause the grease to thin out into a liquid which leaks out from the lubricated surfaces. This is a prime consideration inasmuch as grease-lubricated machine parts are encountered in port installations, on deck of navy and marine vessels, in steel rolling mills, in water pumps of all kinds, in mining machinery, in oil-well drilling equipment, etc. In many of such instances, relatively high operating temperatures develop, such that even lime base greases, which are highly resistant to water, become unstable. While a number of modifying agents have been incorporated into various grease types to improve their stability, such modifying agents have generally been relatively expensive and some have depreciated one or more other desirable characteristics of the. grease.

It is an object of this invention, therefore, to provide greases capable of withstanding severe operating conditions. A further object is to provide greases which retain their original character over a wide range of operating conditions. Another object is the provision of greases which are stable in the presence of water, even when in contact with water at high temperature. Still another object is to tailor-make soaps to be compatible with a variety of vehicles having comparable performance levels. Other objects will be apparent from the following description.

This invention is predicated upon the discovery that greases of outstanding stability can be prepared from a combination of soaps and salts of fatty acids in balanced proportions. More specifically, it has been found that regulated proportions of certain low molecular weight acids having from one to six carbon atoms per molecule, particularly intermediate molecular weight acids having from seven to twelve carbon atoms per molecule and certain high molecular weight acids having from thirteen to thirty-six or more carbon atoms per molecule, can be incorporated, in the form of their corresponding sodium 2,878,185 Patented Mar. 17, 1959 "ice to form grease compositions.

Although minor amounts of low molecular weight fatty acids, having from one to six carbon atoms per molecule, have been used, in the form of their salts, in greases, it has been considered hitherto that such amounts had to be limited lest the grease structure be impaired. It has been recognized, too, that such acids could not generally be used as the sole acid component of grease. Illustrative of greases containing relatively small amounts of salts of low molecular weight acids are those described in U. S. Letters Patent 2,197,263 and 2,564,561. In contrast to such earlier grease compositions, the greases contemplated herein contain proportionally greater amounts of certain low molecular weight acids.

The outstanding stability of my superior grease composition appears to be largely due to the amount and type of soaps and salts present. I have discovered that it is necessary to control, not only the fatty acid portion of the soap and salt molecules, but the cation as Well. Of all the alkaline earth metals, only calcium will form soaps and salts that give the desired performance in the compositions described. On the other hand, when the cation of the soap and salt molecules is sodium or lithium, glycerine or a similar polyhydroxy compound such as diethylene glycol must be present in the grease composition. When glycerine is the only hydroxy component about to 5 percent by weight based on the total grease composition is generally suflicient.

It has been found that the sodium and/or lithium base greases should be formed from a combination of acids, which conform to the following relationship:

Typical of the low molecular weight straight chain saturated mouocarboxylic acids contemplated herein are acetic, propionic, butyric, valeric, and caproic. Of these, acetic acid is particularly desirable because it provides outstanding products.

Typical of the intermediate molecular weight saturated monocarboxylic acids which can be used herein are: heptanoic, caprylic, pelargonic, capric, undecylenic, lauric; and mixed unsubstituted C C and C acids having only methyl side chains obtained by the 0x0 process. Preferred of such acids are those having from seven to ten carbon atoms per molecule. Of these acids, caprylic, capric and pelargonic are particularly advantageous.

Illustrative of the high molecular weight monocarboxylic acids of the invention are: saturated aliphatic acids, such as myristic, palmitic, stearic, arachidic, behenic, lignoceric, cerotic; unsaturated aliphatic acids having a single unsaturated double bond, such as oleic; monohydroxy substituted monocarboxylic acids, such as 9-hydroxystearic, IO-hydroxystearic and 12-hydroxystearic; and their corresponding branched-chain isomers. Preferred again are the saturated acids, particularly stearic and palmitic acids.

use that quantity of a material which contains a quantity of high molecular weight acid coming within the critical range recited above.

It is to be understood, of course, that more than one acid of a given type can be used, so long as the balance recited above is maintained.

The mineral oil components of the greases of this invention can vary considerably in character. In general, such oils are characterized by a viscosity (S. U. V.) of greater than about 40 seconds at 100 F., preferably from about 60 to about 6000 seconds at 100 F. It has been found, however, that the character of mineral oil used materially influences the character of the grease compositions. For example, a naphthenic oil-750 seconds at 100 F.provides greases of more fibrous character; whereas, a paraffinic oil of the same viscosity provides greases of smoother texture. In place of all or part of the mineral oil component, other oils of lubricating viscosity can also be used. Such oils include synthetic vehicles comprising esters of aliphatic dibasic acids; silicones; silicate esters; esters of phosphorus-containing acids; fiuorocarbons; etc. Typical of such synthetic oils are: di(2-ethyl hexyl) sebacate, dibutyl phthalate, di-(2- ethyl hexyl) adipate. Other suitable synthetic oils are esters of poly alcohols and monocarboxylic acids, such as polyethylene glycol di-(2-ethyl hexoate). The synthetic vehicles are most suitable for providing greases for use in aircraft, since such greases retain their lubricating value over a wide temperature range, from about -l F. to about 500 F.

The oil component, whether mineral or synthetic or a combination thereof, is generally used in amounts ranging fromabout 50 to about 99 percent by weight of the finished grease composition. And the alkali metal soaps and salts of the aforesaid acids are incorporated in such oil component in amounts ranging from about 1 to about 50 perecent. Preferably, however, the quantity of alkali metal soaps and salts will fall within the range 5 to 40 percent by weight.

The greases of this invention are prepared by conventional grease making techniques. This is in contrast to the calcium soap and salt greases made the subject of a separate and related application for Letters Patent, Serial No. 505,063, filed concurrently herewith. The calcium soap and salt greases are prepared by a novel technique.

A grease typical of those contemplated herein is described in the following example:

EXAMPLE I The quantities of materials used are shown in Table I, following, wherein the product is identified as Grease 1. All of the acids and a saturated aqueous solution of the alkali, together with approximately half of the total mineral oil, are charged to a grease kettle. The contents of the kettle are heated to about 350 F. and are so maintained for about one-half hour, whereupon the contents are dehydrated. Heating of the kettle is discontinued. The remainder of the mineral oil is added to the kettle. The product is paddled and cooled to 140150 F.

The character of the grease described in Example I above is shown below in Table I, wherein it is identified as Grease 1. Also shown therein is Grease 2 which contains lithium soaps and lithium salt. Grease 2 was prepared in the same manner as Grease l.

The data in Table I includes a showing of various physical properties of the several greases. Consistency was determined in accordance with ASTM Method D217- 48 Cone Penetration ofLubricating Grease. The dropping point was determined in accordance with ASTM Method D566-42.

Table I Experiment N o 1 2 Caprylic Acid, Percent 5. 82 Oapric Acid, Percent 8.7 Stearic Acid, Percent 3. 42 5. 4 Acetic Acid, Percent 6. 00 1.6 Lithium Hydroxide Monohydrate, Pe ent 4. 2 Sodium Hydroxide, Percent 6. 85 Glycerine, Percent 5.14 2. 2 Paraffin Oil, Percent 72. 77 77. 9 Unworked Penetration at 77 F. 405 358 Worked Penetration at 77 F 409 339 Dropping Point, F 461 455 It is to be understood that the greases of this invention can also contain other characterizing materials and fillers. For example, the greases can contain anti-oxidants such as amines (e. g., phenyl alpha-naphthylamine), phenols (e. g;, 2-6-ditertiary-butyl4-methyl phenol), and the like; lubricity improving agents such as free fat, free fatty acids, esters of alkyl and/or aryl acids, sulfurized fats, lead soaps, etc. However, as a cautionary note, it is advisable to use small quantities of such characterizing materials to obtain the customary beneficial effects thereof.

The greases of this invention are suitable for a wide range of industrial applications. Some, for example, are suitable for multi-purpose automative greases, serving as chassis, wheelbearing, water-pump grease lubricants; typical of such a grease is that shown above and identified as Grease 1. Others are multi-purpose industrial greases serving as plain-bearing and anti-friction greases for normally loaded and heavily loaded equipment. In general, then, greases contemplated herein range from semi-fluid types suitable as textile machinery lubricants, to solid block type greases used in lubrication of machinery in steel mills, paper mills, cement mills, etc.

The present application is filed as a continuation-inpart of my earlier application Serial No. 300,777, filed July 24, 1952, which has been abandoned in favor of this application.

I claim:

1. A grease composition comprising: an oil vehicle, from about 1 to about 5 percent by weight of a low molecular weight polyhydroxy alcohol, and a mixture therewith of alkali metal soaps and salts selected from the group consisting of lithium and sodium soaps and salts and of mixtures of said soaps and salts, the mixture of said soaps and salts being present in a grease forming quantity, and the alkali metal soaps and salts of said mixture being soaps and salts of acids identified as (I), (II) and (III), one of said acids being a low molecular weight unsubstituted straight chain saturated monocarboxylic acid (I) having from one to six carbon atoms per molecule, one of said acids being an intermediate molecular weight unsubstituted saturated monocarboxylic acid (II) having from seven to twelve carbon atoms per molecule and having no side chain larger than a methyl group, and one of said acids (III) having more than twelve carton atoms per molecule and having no more than one unsaturated double bond being selected from the group consisting of a monocarboxylic acid and a monohydroxy-substituted monocarboxylic acid, the percent-by-weight distribution of said acids being as follows:

I. From about 10 to about 50. II. From about 30 to about 70. III. From about 10 to aboutSO.

2. A grease as defined by claim 1 wherein the metal is sodium.

3. A grease as defined by claim 1 wherein the metal is lithium.

4. A grease as defined by claim 1 wherein the low molecular weight acid (I) is acetic acid.

5. A grease as defined by claim 1 wherein the intermediate molecular weight acid (II) is caprylic acid.

6. A grease as defined lay claim 1 wherein acid (111) is stearic acid.

7. A grease as defined by claim 1 wherein the oil vehicle is a mineral oil having a Saybolt Universal viscosity from about 60 to about 6000 seconds at 100 F.

8. A grease as defined by claim 1 wherein the oil vehicle is a naphthenic oil having a Saybolt Universal viscos ity of about 700-800 seconds at 100 F.

9. A grease as defined by claim 1 wherein the oil vehicle is present in an amount from about 50 to about 99 percent by weight, and wherein the mixture of soaps and salt is present in an amount from about 1 to about 50 percent by weight.

10. A grease as defined by claim 1 wherein the polyhydric alcohol is glycerine.

11. A sodium grease comprising: a naphthenic oil, about 5 percent by weight of glycerine, and about 23 percent by weight of a mixture of sodium salt and soaps of acetic acid, caprylic acid and stearic acid, the percent-byweight distribution of said acids being about:

12. A lithium grease comprising: a naphthenic oil, about 2 percent by weight of glycerine, and about 20 percent by weight of a mixture of lithium salt and soaps of acetic acid, capric acid, and stearic acid, the percent-byweight distribution of said acids being about:

Acetic acid 10 Capric acid 55 Stearic acid References Cited in the file of this patent UNITED STATES PATENTS 2,229,030 Adams et a1. Jan. 21, 1941 2,229,042 Brunstrum et a1 Ian. 21, 1941 2,229,367 Brunstrum Jan. 21, 1941 2,274,675 Earle Mar. 3, 1942 2,413,121 Swenson Dec. 24, 1946 2,487,080 Swenson Nov. 8, 1949 2,606,153 Holdstock Aug. 5, 1952 2,612,473 Morway Sept. 30, 1952 2,628,195 Allison et a1. Feb. 10, 1953 2,628,202 Allison et a1. Feb. 10, 1953

Claims (1)

1. A GREASE COMPOSITION COMPRISING : AN OIL VEHICLE FROM ABOUT 1 TO ABOUT 5 PERCENT BY WEIGHT OF A LOW MOLECULAR WEIGHT POLYHYDROXY ALCOHOL, AND A MIXTURE THEREWITH OF ALKALI METAL SOAPS AND SALTS SELECTED FROM THE GROUP CONSISTING OF LITHIUM AND SODIUM SOAPS AND SALTS AND OF MIXTURES OF SAID SOAPS AND SALTS, THE MIXTURE OF SAID SOAPS AND SALTS BEING PRESENT IN A GREASE FORMING QUANTITY, AND THE ALKALI METAL SOAPS AND SALTS OF SAID MIXTURE BEING SOAPS AND SALTS OF ACIDS INDIFIED AS (I), (II) AND (III). ONE OF SAID ACIDS BEING LOW MOLECULAR WEIGHT UNSUBSTITUED STRAIGHT CHAIN SATURATED MONOCARBOXYLIC ACID (I) HAVING FROM ONE TO SIX CARBON ATOMS PER MOLECULE, ONE OF SAID ACIDS BEING AN INTERMEDIATE MOLECULAR WEIGHT UNSUBSTITUTED SATURATED MONOCARBOXYLIC ACID (II) HAVING FROM SEVEN TO TWELVE CARBON ATOMS PER MOLECULE AND HAVING NO SIDE CHAIN LARGER THAN A METHYL GROUP AND ONE OF SAID ACIDS (III) HAVING MORE THAN TWELVE CARBON ATOMS PER MOLECULE AND HAVING NO MORE THAN ONE UNSATURATED DOUBLE BOND BEING SELECTED FROM THE GROUP CONSISTING OF A MONOCARBOXYLIC ACID AND A MONOHYDROXY-SUBSTITUDED MONOCARBOXYLIC ACID, THE PERCENT-BY-WEIGHT DISTRIBUTION OF SAID ACIDS BEING AS FOLLOWS: I. FROM ABOUT 10 TO ABOUT 50. II. FROM ABOUT 30 TO ABOUT 70. III. FROM ABOUT 10 TO ABOUT 50.