US2878187A - Grease composition containing alkali metal salts and soaps of intermediate molecularweight acids and of low molecular weight acids - Google Patents

Description

United States Patent M GREASE COMPOSITION CONTAINING ALKALI METAL SALTS AND SOAPS OF INTERMEDIATE MOLECULAR WEIGHT ACIDS AND OF LOW MOLECULAR WEIGHT ACIDS Clarence Liddy, New York, N. Y., assignor to Socony Mobil Oil Company, Inc., a corporation of New York No Drawing. Application May 23, 1955 Serial No. 510,500

14 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, and is a continuation-in-part of my application Serial No. 300,775, filed July 24, 1952, which has been abandoned. The novel greases contain balanced proportions of low and intermediate molecular weight fatty acids, present as alkali metal salts and soaps, 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, notably at high temperatures of the order of 250-350 F. and higher. Some conventional greases are characterized by excessive softening when exposed to such high temperatureoperation, thereby being extruded too rapidly from the area being lubricated to provide efficient 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 lubricatedsurfaces. This is a. prime consideration inasmuch as grease-lubricated machine parts are encountered in port installations, on deck of navy and marine vesels, in steel rolling mills, in water pumps of all kinds, in mining machinery, in oil Well drilling equipment, etc. In many 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 styles 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 It is also an object to provide greases effective for high temperature use, such as at 250-350 F. and higher. 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 salts and 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 sodium and/or lithium salts and soaps in balanced proportions. More specifically, it has been found that regulated proportions of certain low molecular weight straight chain saturated monocarboxylic acids having from one to six carbon atoms per-molecule and of particular 2,878,187 Patented Mar. 17, 1959 intermediate molecular weight saturated monocarboxylic acids having from seven to twelve carbon atoms per molecule, can be incorporated, in the form of their corresponding sodium and/or lithium salts and soaps, into a lubricating vehicle 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 a grease. Illustrative of greases containing relatively small amounts of salts of low molecular weight acids are those described in U. S. Letters Patents 2,197,263 and 2,564,561. In contrast to such earlier grease compositions, the greases contemplated herein contain substantially greater amounts of low molecular weight acids.

The outstanding stability of my superior grease composition appears to be largely due to the amount and type of salts and soaps present. When the cation of the saltsoap molecule 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 polyhydroxy component, about 2% by weight based on the total grease composition is sufficient.

It has been found that the sodium and/ or lithium base greases should be formed from a combination of acids, in which the molar ratio of low molecular weight acid to intermediate molecular weight acid ranges from about 0.25 :1 to about 10:1. However, the optimum molar ratio ranges from about 1:1 to 25:1.

The foregoing molar ratios are critical inasmuch as an insufiicient quantity of a low molecular weight acid, such as acetic, is responsible for a semi-fluid product, and an undesirably low dropping point. correspondingly, an excessive amount of an acid, such as acetic, produces a salt-soap structure which is difiicult, if not impossible, to disperse in a stable state in an oil vehicle. A similar influence is seen in the use of too little, or an excess, of an intermediate molecular Weight acid such as caprylic. An insufliciency of caprylic acid generally causes the product to harden excessively in storage; and an excess of caprylic acid causes the product to bleed oil excessively in storage.

Typical of the low molecular weight straight chain saturated monocarboxylic acids contemplated herein are:

acetic, propionic, butyric, valeric, and capr'oic. 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 no side chain larger than a. methyl group, obtained by the 0x0 process. Preferred of such acids are those containing from seven to ten carbon atoms. Of these acids, caprylic, capric and pelargonic are particularly advantageous.

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 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-J50 seconds at 100 F.--provides greases of more fibrous character; whereas, a parafiinic 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, fluorocarbons. Typical of such synthetic oils are: di-(Z-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 100 F. to about 500 F.

The oil component, whether mineral or synthetic or a combination thereof, is generally used in amounts ranging from about 50 to about 99 percent by weight of the finished grease composition. The alkali metal salts and soaps of the aforesaid acids are incorporated in such oil component in amounts ranging from about 1 percent to about 50 percent. Preferably, however, the quantity of alkali metal salts and soaps will fall within the range to 30 percent by weight.

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

EXAMPLE I Fifty-six parts-by-weight of capric acid, ten parts-byweight of acetic acid, fifteen parts-by-weight of glycerine and forty-two and two tenths parts-by-weight of lithium hydroxide monohydrate in two hundred parts-by-weight of water, were charged to a small kettle. Two hundred parts-by-weight of a naphthenic mineral oil (750 seconds S. U. V. at 100 F.) were added and the mixture raised to a temperature of 160 F. and kept at this temperature for about ten minutes. The temperature of the kettle contents was finally raised to 310 F. until dehydration was complete at which time the mixture had a fair consistency. Additional mineral oil, one hundred and twenty seven parts-by-weight, was then added. After the mineral oil had been thoroughly incorporated into the mixture, the temperature was allowed to slowly drop. When a temperature of 180 F. was reached, the grease so formed was withdrawn from the kettle.

The character of the grease described in Example I above is shown below in Table I, wherein it is identified as composition 1. Also shown therein for purposes of comparison are the additional novel greases.

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

Table I Composition 1 2 3 Oapric, Percent Caprylic Acid, Percent Acetic Acid, Percent 2 Diethylene glycol, Percent. Glycerine LiOH.H20, Percent NaOH, Percent Mineral Oil (N aphthenic 75 100 F.), Percent. Tests:

ASTM Dropping 494 420 378.

Point. ASTM Penetration 368/349 365/360.

77 F., Unworked/ Worked. Description of Final Satisfactory Semi-fluid Satisfactory Product. grease strucgrease grease ture. structure. structure.

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 antioxidants such as amines (e. g., phenyl alpha-naphthylamine), phenols (e. g., 2-6-ditertiary-butyl-4-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 cautionary note, it is advisable to use small quantities of such characterizing materials to obtain the customary beneficial efiects thereof.

The greases of this invention are suitable for a wide range of industrial applications. Some, for example, are suitable for multi-purpose and auto-motive greases, serving as chassis, wheel-bearing, water-pump grease lubricants; typical of such 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.

I claim:

1. A grease composition comprising: an oil vehicle, a mixture of an alkali metal salt and an alkali metal soap, and from about 2 to about 5 percent by weight of a low molecular weight polyhydroxy alcohol, the mixture of salt and soap being present in a grease forming quantity, and the alkali metal salt of said mixture being a salt of a low molecular weight unsubstituted straight chain saturated monocarboxylic acid (I) having from one to six carbon atoms per molecule, and the alkali metal soap of said mixture being a soap of 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, the molar ratio of said acid (I) to said acid (II) being from about 0.25:1 to about 10:1.

2. A grease as defined by claim 1 wherein the molar ratio is from about 1:1 to about 2.5:1.

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

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

-5. A grease as defined by claim 1 wherein the low molecular weight acid is acetic.

6. A grease as defined in claim 1 wherein the intermediate molecular weight acid is caprylic acid.

7. A grease as defined by claim 1 wherein the oil vehicle is a mineral oil having a Saybolt Universal viscosity from about 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 viscosity 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 salt and soap is present in an amount from about 1 to about 50 percent by weight.

10. A grease as defined in claim 1 wherein the polyhydroxy alcohol is glycerine.

11. A grease composition comprising: an oil vehicle, a mixture of an alkali metal salt and an alkali metal soap, and from about 2 to about 5 percent by weight of glycerine, the mixture of salt and soap being present in a grease forming quantity, and the alkali metal salt of said mixture being a salt of a low molecular weight unsubstituted straight chain saturated monocarboxylic acid (I) having from one to six carbon atoms per molecule, and the alkali metal soap of said mixture being a soap of 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, the molar ratio of said acid (I) to said acid (II) being from about 0.25:1 to about 10:1.

12. A grease composition comprising: a naphthenic mineral oil having a Saybolt Universal viscosity of about 750 seconds at 100 F., a mixture of an alkali metal salt and an alkali metal soap, and from about 2 to about 5 percent by Weight of a low molecular weight polyhydroxy alcohol, the mixture of said alkali metal salt and soap being present in an amount from about 10 to about 30 percent by weight of said grease composition, the alkali metal being selected from the group consisting of sodium and lithium, the alkali metal salt being a salt of acetic acid and the alkali metal soap being a soap of caprylic acid, the molar ratio of said acids being about 1.6:1.

13. A grease composition comprising: an oil vehicle, a mixture of a lithium salt and a lithium soap, and from about 2 to about 5 percent by weight of glycerine, the mixture of said salt and soap being present in a grease forming quantity, the lithium salt being a salt of a low molecular weight unsubstituted straight chain saturated monocarboxylic acid (I) having from one to six carbon atoms per molecule, the lithium soap being a soap of 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, the molar ratio of said acid (I) to said acid (II) being from about 0.25:1 to about 10:1.

References Cited in the file of this patent UNITED STATES PATENTS 2,274,675 Earle Mar. 3, 1942 2,487,080 Swenson Nov. 8, 1949 2,606,153 Holdstock Aug. 5, 1952 2,607,735 Sproule et a]. Aug. 9, 1952 2,612,473 Morway Sept. 30, 1952 2,628,195 Allison et al. Feb. 10, 1953 2,628,202 Allison et al Feb. 10, 1953 OTHER REFERENCES Can. I. Research, vol. 11, Soc. B, pages 76-89 (1955), article by Gallay et al.

Claims (1)

1. A GREASE COMPOSITION COMPRISING: AN OIL VEHICLE, A MIXTURE OF AN ALKALI METAL SALT AND AND ALKALI METAL SOAP, AND FROM ABOUT 2 TO ABOUT 5 PERCENT BY WEIGHT OF A LOW MOLECULAR WEIGHT POLYHYDROXY ALCOHOL, THE MIXTURE OF SALT AND SOAP BEING PRESENT IN A GREASE FORMING QUANTITY, AND THE ALKALI METAL OF SAID MIXTURE BEING A SALT OF A LOW MOLECULAR WEIGHT UNSUBSTITUDED STRAIGHT CHAIN SATURATED MONOCARBOXYLIC ACID (I) HAVING FROM ONE TO SIX CARBON ATOMS PER MOLECULE, AND THE ALKALI METAL SOAP OF SAID MIXTURE BEING A SOAP OF 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, THE MOLAR RATIO OF SAID ACID (I) TO SAID ACID (II) BEING FROM ABOUT 0.25:1 TO ABOUT 10:1.