US3639236A

US3639236A - Colloidal asbestos-complex aluminum salt-alkali-alkaline earth metal mixed salt/soap lubricant

Info

Publication number: US3639236A
Application number: US715529A
Authority: US
Inventors: Arnold J Morway; Albert J Bodner
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1968-03-25
Filing date: 1968-03-25
Publication date: 1972-02-01
Anticipated expiration: 1989-02-01

Abstract

A lubricating grease containing lubricating oil, a complex fatty acid salt thickener, a complex aluminum salt and colloidal asbestos demonstrates excellent structural stability, extreme pressure properties and resistance to hardening under static conditions at high temperatures. The colloidal asbestos is distinguished over art-known asbestos by its randomly oriented, mattelike flakes and agglomerates of visible asbestos filaments.

Description

United States Patent Morway et al.

COLLOIDAL ASBESTOS-COMPLEX ALUMINUM SALT-ALKALl-ALKALINE EARTH METAL MIXED SALT/SOAP LUBRICANT Arnold .l. Morway, Clark; Albert J. Bodner, Watchung, both of NJ.

Assignee: Esso Research and Engineering Company Filed: Mar. 25, 1968 Appl. No.: 715,529

Inventors:

US. Cl ..252/l3, 252/21 252/37.7 lnt.Cl ...Cl(lm l/24,Cl0m l/lO Field of Search ..252/l3, 21, 37.7

References Cited 7 UNITED STATES PATENTS l 1/1961 Odell et al. ..252/l3 8/1958 Morway et al ..252/39 Primary Examiner-Daniel T. Wyman Assistant Examiner-T. Vaughn Anomey-Pearlman & Stahl and Robert I. Pearlman [57] ABSTRACT A lubricating grease containing lubricating oil, a complex fatty acid salt thickener, a complex aluminum salt and colloidal asbestos demonstrates excellent structural stability, extreme pressure properties and resistance to hardening under static conditions at high temperatures. The colloidal asbestos is distinguished over art-known asbestos by its randomly oriented, mattelike flakes and agglomerates of visible asbestos filaments.

8 Claims, No Drawings BACKGROUND OF THE INVENTION 1. Field ofthe Invention This invention is directed to lubricating grease compositions containing lubricating oil, a complex aluminum salt, a complex fatty acid salt thickener and colloidal asbestos. More particularly, it is directed to a grease composition containing naphthenic base mineral oil; an aluminum complex salt prepared from aluminum alcoholates, higher molecular weight fatty acids and aromatic acids; a complex fatty acid salt thickener comprising an alkaline earth metal salt of a C, to C fatty acid and an alkali-alkaline earth metal salt of a C,- to C fatty acid; and colloidal asbestos having a particle outer diameter of about 1 to 80 millimicrons and a particle length of about 2,000 to 30,000 millimicrons. The colloidal asbestos is distinguished from art-known asbestos by its chrysotile structure and its hollow tubular structure.

2. Description ofthe Prior Art The employment of an aluminum complex salt in lubricating greases is known to the art. See US. Pat. No. 3,345,291. Greases having this salt are characterized as having very high melting points and relatively high resistances to water solubility. Greases containing a complex salt thickener of fatty acid salts of alkali and alkaline earth metals have also been known in the art. Greases containing this thickener system are characterized as having relatively high dropping points and excellent extreme pressure properties, but have the attendant disadvantage of hardening excessively at high temperatures under static conditions. The use of asbestos as a thickener or filler in lubricating greases is also not new to the art. A number of grease formulations describing asbestos as a component are described in the book Lubricating Greases by C. J. Boner, Second Edition, pages 687, etc. These greases utilize conventional asbestos or asbestos floats which are relatively longfibered asbestos agglomerates sometimes containing abrasive materials. This long-fibered asbestos is generally used in conjunction with other thickening agents such as soaps or other inorganic thickeners, as the asbestos does not, by itself, form a thickened, homogeneous, nonseparating grease gel.

SUMMARY OF THE INVENTION It has now been found that a grease comprising a major amount of lubricating oil, about 2 to weight percent preferably 5 to ID weight percent ofa complex aluminum salt, about 5 to weight percent, preferably 8 to 15 weight percent of a fatty acid salt complex comprising an alkaline earth metal salt ofa C, to C fatty acid and a salt of a C, to C fatty acid and a member selected from the group consisting ofalkali bases, alkaline earth metal bases and combinations thereof, and about 2 to l5 weight percent, preferably 5 to 10 weight percent of colloidal asbestos has excellent structural stability and extreme pressure properties and does not harden excessively at high temperatures under static conditions. In addition the colloidal asbestos will normally improve the life of the lubricant during high-temperature use and will reduce the total amount of thickeners required to thicken the oil to the desired consistency.

The complex aluminum salt which forms a part of the grease can generally be described as the reaction product of an aluminum alcoholate ofthe general formula:

R-O-Al where R is a C, to C,, preferably C branched or straight chain alkyl group; a C,, to C preferably a C to C fatty acid: and an aromatic acid having the general formula:

COOH

where Ar is an organic aromatic group and X is selected from the group consisting of hydrogen, a lower alkyl group, an amino group, a halogen and combinations thereof and n is an integer offrom l to 5.

Suitable aluminum alcoholates for use in the preparation of the greases are those in which the alcohol precursor is ethyl alcohol, propyl alcohol, isopropyl alcohol, any of the butyl alcohols, or mixtures of the foregoing alcohols.

Suitable fatty acids for use in the preparation of the complex basic aluminum soap greases are caproic acid, lauric acid, myristic acid, palmitic acid, stearic acid, l2-hydroxy stearic acid, arachidic acid, melissic acid, oleic acid, and linoleic acid. Phenyl-substituted fatty acids such as phenyl decanoic acid and naphthenic acids containing at least l2 carbon atoms may also be employed as the fatty acid reactant.

Aromatic acids suitable for use in the preparation of the basic complex aluminum grease are benzoic acid, the toluic acids, benzoic acids substituted with one or more ethyl, propyl or butyl groups, amino-substituted benzoic acids, chlorobenzoic acids and naphthoic acids. Preferably, the aromatic carboxylic acid is a monocarboxylic acid.

As to the preparation of aluminum complex salts in general, see US. Pat. Nos. 3,345,291 and 2,768,138.

The complex fatty acid salt thickeners as employed in the present invention are comprised of a mixture of an alkaline earth metal salt ofa C, to C fatty acid, the preferred salt being calcium acetate; and a salt of a C to C preferably C,. to C fatty acid and a base selected from the group consisting of alkali bases, alkaline earth metal bases and combinations thereof. The term alkali metal as used in the invention means the metals ofGroup l ofthe periodic chart of elements, including lithium, sodium and potassium. The term alkaline earth metal refers to the metal of Group II of the periodic chart of the elements, including magnesium, calcium and barium. The C, to C fatty acids from which the alkaline earth metal salt is formed include formic, acetic, propionic, butyric and valeric acid. The fatty acids useful for forming the higher molecular weight alkali or alkaline earth metal salts include naturally oc curring or synthetic, hydroxy-substituted and unsubstituted, saturated and unsaturated, mixed or unmixed fatty acids having about C to C30 but preferably C to C carbon atoms per molecule. Examples of such acids include: caproic, stearic, hydroxy stearic, such as l2-hydroxy stearic, dihydroxy stearic, polyhydroxy stearic, and other saturated hydroxy fatty acids, arachidic, oleic, ricinoleic, hydrogenated fish oil, tallow acids, etc.

Particularly preferred is l2-hydroxy stearic acid. A preferred alkaline earth metal salt is barium l2-hydroxy stearate. It is within the scope of this invention to not only include an alkali or alkaline earth metal salt of a C to C fatty acid but also combinations of these materials. For example, the grease of this invention may include not only barium l2- hydroxy stearate but also lithium l2-hyulroxy stearate.

It is to be emphasized that the complex fatty acid salt element of this grease is made up of two parts; the alkaline earth metal salt of a C, to C fatty acid part and the alkali-alkaline earth metal salt of a C,, to C fatty acid part. The mole ratio of the C, to C fatty acid salt to the C to C fatty acid salt is in the range of about 3:1 to 20:], preferably 7:1 to 12: l.

The lubricating oil employed to produce lubricating grease compositions in the method of this invention may be conventional grease-making mineral oils as well as synthetic lubricating oils, although the mineral lubricating oils are preferred. The synthetic oils include synthetic lubricating oils having a viscosity of at least 30 SSU at F. such as esters of monobasic acids (e.g., ester of C Oxo alcohol with C Oxo acid, ester of C Oxo alcohol with octanoic acid, etc.), esters of dibasic acids (e.g., di-2-ethyl hex yl sebacate, dinonyl adipate, etc.), esters of glycols (e.g., C Oxo acid diester of tetraethylene glycol, etc.), complex esters (e.g., the complex ester formed by reacting 1 mole of sebacic acid with 2 moles of tetraethylene glycol and 2 moles of 2-ethyl hexanoic acid, complex ester formed by reacting 1 mole of tetraethylene glycol with 2 moles of sebacic acid and 2 moles of Z-ethyl hexanol, complex ester formed by reacting together 1 mole of azelaic acid, 1 mole of tetraethylene glycol, 1 mole of C Oxo alcohol, and 1 mole of C Oxo acid), esters of phosphoric acid (e.g., the ester formed by contacting 3 moles of the monomethyl ether of ethylene glycol with 1 mole of phosphorus oxychloride, etc.), halocarbon oils (e.g., the polymer of chlorotrifluoroethylene containing 12 recurring units of chlorotrifluoroethylene), alkyl silicates (e.g., methyl polysilixanes, ethyl polysiloxanes, methyl phenyl polysiloxanes, ethyl phenyl polysiloxanes, etc.), sulfite esters (e.g., ester formed by reacting 1 mole of sulfur oxychloride with 2 moles of the methyl ether of ethylene glycol, etc.), carbonates (e.g., the carbonate formed by reacting C Oxo alcohol with ethyl carbonate to form a half ester and reacting this half ester with tetraethylene glycol), mercaptals (e.g., the mercaptal formed by reacting Z-ethyl hexyl mercaptan with formaldehyde), formals (e.g., the formal formed by reacting C Oxo alcohol with formaldehyde), polyglycol type synthetic oils (e.g., the compounds formed by condensing butyl alcohol with 14 units of propylene oxide, etc.), or mixtures of any of the above in any proportions. Quite generally the mineral or synthetic oils should have a viscosity within the range of about 35 to 200 SSU at 210 F. and flash points of about 350 to 600 F. Lubricating oils having a viscosity index of 100 or higher may be employed.

The asbestos of the present invention differs from the above-mentioned long-fibered conventional asbestos in that the asbestos fibers are separate and distinct, occurring in a small colloidal size, having a large surface area, and can be dispersed in oil to form a gel by themselves, and without settling out from the oil. This colloidal asbestos is chrysotile having the chemical formulation Mg,,(OH),,Si 0,,,. The usual mode of occurrence of chrysotile is a cross-fiber configuration in which filaments of chrysotile (i.e., bundles of fibers) are closely packed together and set at right angles to the walls of cracks and fissures that extend through the host rock of the ore body. However, in 1959, an unusual deposit of chrysotile asbestos, with properties and a mode of occurrence different from the previously known cross-fiber material, was discovered in central California. The ore of this new deposit, instead of occurring in veins, occurs in randomly oriented, mattelike flakes and agglomerates of visible asbestos fila merits. which in turn are made up of many thousands of extremely small tubular fibers. The lengths of these small fibers vary from a few millimicrons to thousands of millimicrons, generally 2,000 to 30,000 millimicrons, while the outer diameters of the fibers vary much less and are usually in the range of 1 to 80, e.g., 10 to 30 millimicrons. A typical colloidal asbestos that was used in the working examples of the invention had the following characteristics:

PROPERTIES OF COLLOIDAL ASBESTOS FIBERS Brightness GE) Refractive Index Dispersion in Water Surface Area Oil Absorption Water Retention Dry Bulk Density 2-2.5 lbs./cu. l't. Fiber Dimension Fully/pH range 4-6 47-50 sq. meters/gram 14-16 cc./l grams of fibers 42 grams/20 grants of fibers O.D. 25.0 millimicrons LD. 60 millimicrons Length Z.500-25,()00 millimicrons vious properties to a grease which cannot be predicted from the prior art.

Various other additives may also be added to the lubricating composition in amounts of 0.1 to 10.0 weight percent each. Such additives include lubricating oil sludge detergents and dispersants; oxidation inhibitors such as phenyl-alphanaphthylamine; corrosion inhibitors such as sorbitan monooleate and sodium nitrite; dyes; other grease thickeners; and the like.

The preparation of the grease of this invention generally comprises neutralizing in situ the alkali or alkaline earth metal hydroxide and the C to C fatty acid and then adding the alkaline earth metal salt of a C to C fatty acid and colloidal asbestos. The alkaline earth metal salt of the C, to C fatty acid may be added as a preformed constituent or it may be formed in situ as was the longer fatty acid soap.

The complex aluminum soap is formed separately from the colloidal asbestos fatty acid soap-salt complex described above. The preparation of the complex aluminum soap is generally described in US. Pat. No. 3,345,291. Essentially it comprises forming a complex aluminum soap in the presence ofa base mineral oil by reacting a lower aluminum alcoholate with a mixture ofa fatty acid, an aromatic carboxylic acid and water at moderate temperatures. Another method of incorporating the complex aluminum salt into a lubricating oil is simply to mix the preformed salt into the oil as described in US. Pat. No. 2,768,138. The finished product can be prepared by mixing the desired amount of the lubricant containing the complex aluminum salt and the lubricant containing the colloidal asbestos fatty acid salt complex at moderate temperatures. Additional lubricating oil may be added to bring the amount of constituents into the desired ranges.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be further understood by the following examples which are not to be construed as a limitation on the invention.

EXAMPLE Part A Preparation of Colloidal Asbestos Fatty Acid Salt Complex Grease 5.12 parts by weight of l2-hydroxy stearic acid and 69.00 parts by weight of a naphthenic based mineral oil having a viscosity of 510 SUS (Saybolt Universal Seconds) at F. were charged to a steam-heated kettle, mixed and warmed to 200 F. 2.88 parts by weight of barium hydroxide octahydrate in the form ofa 20 weight percent aqueous solution was then added to the kettle while mixing. 15.00 parts by weight of calcium acetate in the form of a 20 weight percent aqueous solution was then slowly added and the entire ingredients in the steam kettle were heated to 325 F. At this point, 6.00 parts by weight of colloidal asbestos and 2.00 parts by weight of phenyl-alpha-naphthylamine were added and the grease was cooled.

Part B Preparation ofComplex Aluminum Grease A complex aluminum grease was prepared by charging to a gas fire heated grease kettle 5.96 parts by weight (1 mole) of Hydrofol Acids 51, 2.59 parts by weight 1 mole) of benzoic acid and 29.04 parts by weight of a mineral lubricating oil having a viscosity of 510 SUS at 100 F. The ingredients were heated to 200 F. and mixed at that temperature for 1 hour to drive off the water of reaction. Hydrofol Acids 51 is a commercial acid obtained by hydrogenating fish oil and has an average chain length and degree of unsaturation corresponding to stearic acid.

434 parts by weight (1 mole) of aluminum isopropoxide and 29.04 additional parts by weight of the mineral oil were then added to the kettle and heated while mixing to 300 F. The mixture was held at this temperature for 40 minutes to allow for a sufficient reaction time and to drive off the water of reaction. The mixture was then cooled to 200 F., at which point 16 ml. of water was added as a complexing aid. The ingredients were then reheated to 290 F., holding at this temperature for 1 hour to complete the reaction. 29.04 additional parts by weight of the mineral oil was added, and the temperature was raised to about 400 to 410 F. and held at that temperature for 1 hour 2.00 parts by weight of phenyl-alphanaphthylamine (a conventional antioxidant) was then added and the aluminum complex grease cooled to 340350 F.

Part C Preparation of Grease Containing Complex Aluminum Salt, Mixed Salt-Soap Thickener, and Colloidal Asbestos.

At 350 F. 72.6 parts by weight of the grease of Part A was mixed with 18.2 parts by weight of the grease of Part B. The resulting grease was mixed and allowed to cool. This product was Morehouse milled and an additional 9.2 parts by weight of the mineral oil was added. The final product, the grease of this invention, was then remilled to the desired consistency.

Grease C was smooth in appearance, had a dropping point in excess of 400 F., was not abrasive and was filterable through a lOO-mesh screen. A similar grease containing artknown (Canadian) asbestos was lumpy in appearance, abrasive in texture and was not filterable through a IOO-mesh screen. The oil and asbestos components of the art-knowntype greases also tended to separate at temperatures in excess of 300 F., indicating that such grease was not as suitable for high-temperature services as was the grease of the invention.

Grease C, the grease of this invention, also passed the 40 lb. load Timken Test, a standard test used to determine the ability of a lubricant to function under extreme pressure without causing sliding surfaces to become scarred or welded. This test indicates that the grease containing the colloidal asbestos possesses excellent extreme pressure properties.

Grease C also demonstrated resistance to static hardening under high temperatures. The test procedure to determine static hardening consisted essentially of initially working a grease 60 strokes with a penetration apparatus consisting of a modified cone, such cone producing penetrations about onehalf the scale of penetrations produced by the usual cones. The initial depth of penetration was measured and the grease stored in ovens at 250 F. At periods of l, 9 and 28 days the depth of penetration was measured. Lower values indicate a hardening of the grease while higher values indicate a loss of structural stability and general decomposition of the grease. The original penetration value in mm./l0 at 77 F. was 147. At 1, 9 and 28 days after oven storage, the values were l33, 120 and l2] respectively. Such values indicate good high-temperature resistance to static hardening.

What is claimed is:

l. A lubricating grease composition comprising:

a. a major amount oflubricating oil;

b. about 2 to weight percent ofa complex aluminum salt;

c. about 5 to weight percent of a salt complex comprismg: 1. an alkaline earth metal salt ofa C, to C fatty acid, and 2 an alkaline earth metal salt ofa C to C fatty acid; and d. about 2 to l5 weight percent of colloidal asbestos; said weight percents being based on the total composition; said colloidal asbestos being characterized as having naturally occurring fibers with a particle outer diameter of about 1 to millimicrons and a particle length of about 2,000 to 30,000 millimicrons;

said complex aluminum salt comprising the reaction product of an aluminum alcoholate of a C to C aliphatic alcohol, a C to C fatty acid, and an aromatic carboxylic acid.

2. A lubricating composition as in claim 1 wherein the mole ratio of the C to C fatty acid salt to the C to C fatty acid salt in said salt complex is in the range of about 3:1 to 20: l,

3. A lubricating composition as in: claim It wherein the lubricating oil is a naphthenic base mineral oil.

4. A lubricating composition as in claim 3 wherein the complex aluminum salt is the reaction product of an aluminum alcoholate of the general formula:

where R is a C to C, alkyl group; a C to C fatty acid; and an aromatic acid having the general formula:

COOH where Ar is an organic aromatic group and X is selected from the group consisting of hydrogen, a lower alkyl group, a halogen and combinations thereof and n is an integer from 1 to 5.

5. A lubricating composition as in claim 1 wherein the alkaline earth metal salt of a C to C fatty acid is calcium acetate and the C to C fatty acid salt is an alkaline earth metal salt.

6. A lubricating composition as in claim 5 wherein the C to C fatty acid salt is barium l2-hydroxy stearate.

7. A lubricating composition as in claim 6 wherein the mole ratio of calcium acetate to barium l2-hydroxy stearate is in the range of7:l to 12:1.

8. A lubricating composition as in claim 1 wherein the aluminum alcoholate reactant portion of the aluminum complex is aluminum isopropoxide, the fatty acid is stearic acid and the aromatic acid is benzoic acid.

Claims

2. an alkaline earth metal salt of a C6 to C30 fatty acid; and d. about 2 to 15 weight percent of colloidal asbestos; said weight percents being based on the total composition; said colloidal asbestos being characterized as having naturally occurring fibers with a particle outer diameter of about 1 to 80 millimicrons and a particle length of about 2,000 to 30,000 millimicrons; said complex aluminum salt comprising the reaction product of an aluminum alcoholate of a C1 to C4 aliphatic alcohol, a C6 to C22 fatty acid, and an aromatic carboxylic acid.
2. A lubricating composition as in claim 1 wherein the mole ratio of the C1 to C5 fatty acid salt to the C6 to C30 fatty acid salt in said salt complex is in the range of about 3:1 to 20:1.
3. A lubricating composition as in claim 1 wherein the lubricating oil is a naphthenic base mineral oil.
4. A lubricating composition as in claim 3 wherein the complex aluminum salt is the reaction product of an aluminum alcoholate of the general formula: where R is a C1 to C4 alkyl group; a C6 to C22 fatty acid; and an aromatic acid having the general formula: where Ar is an organic aromatic group and X is selected from the group consisting of hydrogen, a lower alkyl group, a halogen and combinations thereof and n is an integer from 1 to 5.
5. A lubricating composition as in claim 1 wherein the alkaline earth metal salt of a C1 to C5 fatty acid is calcium acetate and the C6 to C30 fatty acid salt is an alkaline earth metal salt.
6. A lubricating composition as in claim 5 wherein the C6 to C30 fatty acid salt is barium 12-hydroxy stearate.
7. A lubricating composition as in claim 6 wherein the mole ratio of calcium acetate to barium 12-hydroxy stearate is in the range of 7:1 to 12:1.
8. A lubricating composition as in claim 1 wherein the aluminum alcoholate reactant portion of the aluminum complex is aluminum isopropoxide, the fatty acid is stearic acid and the aromatic acid is benzoic acid.