US3269947A

US3269947A - Lubricant grease

Info

Publication number: US3269947A
Application number: US189953A
Authority: US
Inventors: Reuben A Swenson
Original assignee: Standard Oil Co
Current assignee: Standard Oil Co
Priority date: 1962-04-25
Filing date: 1962-04-25
Publication date: 1966-08-30
Anticipated expiration: 1983-08-30

Description

States Pate .1

This invention relates to lubricant greases and to compositions used in their manufacture, and more particularly provides an aluminum-soap thickened grease having improved mechanical stability. The inventive grease has special applicability as a wire drawing lubricant and for similar metal drawing applications.

The technology of aluminum soap thickened greases is by now a developed art (see Klemgard, Lubricating Greases, Their Manufacture and Use, Chapter VIII- Aluminum Base Greases, 1937, Reinhold) and accordingly their advantages and limitations are well recognized. They have found wide acceptance in many fields, including those in which extreme shear and compressive loads are encountered; wire drawing applications are perhaps the most severe of these, and it is here that aluminum soap greases are most widely used.

However even the best commercial aluminum soap wire drawing greases are not completely satisfactory. Ideally, the grease shall retain its consistency (mechanical stability) under high shear and high pressures, and while aluminum soap greases are more or less adequate in this respect, there is a clear margin for improvement.

It has now been discovered, according to the invention, that aluminum soap greases may be improved with respect to mechanical stability by incorporating in the greases a small amount of an alkaline earth metal salt of a preferentially oil-soluble sulfonic acid, such as calcium mahogany sulfonate.

The aluminum soap greases of the invention generally comprise mineral lubricating oils thickened to grease consistency with an aluminum soap of a fatty acid having about 10-30 carbon atoms per molecule, together with the alkaline earth metal salt of the preferentially oilsoluble sulfonic acid. Preferred greases comprise about 2-20 weight percent aluminum soap and about 0.012 weight percent alkaline earth metal salt although greater or lesser quantities of either may be employed where desirable. Optimally, the grease comprises about 5-l0 percent of an aluminum soap of a 12-24 carbon atom fatty acid, about 0.05l.0 percent of a calcium mahogany sulfonate, with the balance being hydrocarbon oil and any desirable additives and dyes.

The aluminum soaps may be the tri-soaps, the di-soaps, or the mono-soaps, or commercial mixtures of these with possibly some unsaponified fatty acid. (Typical preparations of the soaps are given in Klemgard, above.) Long chain fattyacids which are used in preparing aluminum soap greases are made from fatty acids which advantageously contain from about to about carbon atoms per molecule. optimally from about 12 to about 24 carbon atoms. Such fatty acids may be derived from natural sources, e.g. from mineral fats or vegetable oils, and may be saturated, unsaturated, hydroxy, or hydroxyunsaturated. Examples of individual fatty acids, which are present in varying amounts in natural materials, include: the saturated acids such as lauric, myristic, oleic, palmitic, stearic, arachidic, and behenic acids; the unsaturated aeids such as lauroleic. myristoleic, palmitoleic, and oleic acids; the hydroxy acids such as IZ-hydroxy stearic and 9,l0dihydroxy stearic acids; and the hydroxyunsaturated acids typified by ricinoleic (l2-hydroxy-9 octadccanoic acid). Unsaturated acids may be completely or partially hydrogenated to remove such unsaturalion before being employed in the manufacture of the soaps. Where fatty acids are derived from natural sources, the resultant acid will ordinarily be a mixture of several fatty acids and may be employed either in this condition or after suitable distillation to recover a single fatty acid.

Mineral lubricating oils normally are the most commonly employed lubricant vehicles in preparing aluminum soap greases. These oils are in the lubricating oil viscosity range, e.g. from about 50 SSU at 100 F. to about 300 SSU at 210 F. Mineral oils are preferably solvent extracted to substantially'remove low viscosity index constituents, e.g. aromatics, with known selective solvents such as phenol, Chlorex, liquid sulfur dioxide, etc.

The alkaline earth metal salt of preferentially oil-soluble sulfonic acids used in the above formulation are preferably the salt of sulfonic acids obtained in the treatment of hydrocarbon oils, such as petroleum lubricating oils with strong sulfuric acid, such as concentrated sulfuric acid of at least about percent strength, or fuming sul furic acid. The alkaline earth metal salt of preferentially oil-soluble sulfonic acids, such as those obtained by the sulfonation of olefin polymers having at least about 22 carbon atoms in a molecule or those obtained by the sulfonation of alkylated aromatics having at least about 19 carbon atoms, can also be used.

Preferentially oil-soluble petroleum sulfonic acids are those obtained in the treatment of petroleum oils to obtain highly refined products of the type of technical insulating oils, turbine oils, medicinal white oils, technical white oils, etc., in which the petroleum oils are treated successively with a number of portions of concentrated sulfuric acid, i.e. above about 95 percent strength, or fuming sulfuric acid. A variety of sulfur-containing compounds are formed by chemical reaction of the sulfuric acid upon the oil, including sulfonic acids, organic esters of sulfuric acid, and partial esters of sulfuric acid. Most of these compounds are relatively insoluble in the oil under treating conditions and separate from the oil together with unreacted sulfuric acid as a sludge, which is separated from the oil after each treatment. The sulfuric acid is usually added in dumps of about one-half pound per gallon of oil, the total quantity of acid added depending upon the oil being treated and the final product. Usually, from about three pounds to about nine pounds of sulfuric acid per gallon of oil are used. Some of the sulfonic acids resulting from the treatment of the oil with the sulfuric acid are preferentially oil-soluble and remain in the oil layer after removal of the acid sludge. The sulfonic acids in the acid-treated oil can be extracted therefrom with an alcohol of 60-70 percent strength, and the extracted sulfonic acids neutralized with a basic alkaline earth metal compound, such as for example, lime. Because of the characteristic mahogany color of the sulfonates they are known as mahogany salts in the petroleum art. While the majority of the preferentially oil-soluble sulfonates are obtained from the acidtreated oil, there can be recovered from the acid sludge by suitable solvents, preferentially oil-soluble sulfonates or sulfonic aids. The term preferentially oil-soluble sulfonates therefore includes the oil-soluble sulfonates recovered from the acid-treated oil and the acid sludge.

While any of the preferentially oil-soluble alkaline earth metal sulfonates, such as calcium, barium, or strontium sulfonates can be used, we prefer to employ those obtained from the preferentially oil'soluble sulfonic acids having combining molecular weights in the range of from about 350 to about 525, and preferably those in the range of from about 420 to about 500. The sulfonic acid salt obtained in the manner described contains from about 30 percent to about 60 percent sulfonate, from about 30 percent to about 60 percent oil, up to about 2.0 percent Water. and less than 0.5 percent inorganic salts.

The calcium salt of the preferentially oil-soluble petrolearn sulfonic acids or mahogany acids is preferred, and the preparation thereof is illustrated by the following example: A Mid-Continent petroleum distillate having a Saybolt Universal viscosity at 100 F. of between 220 seconds and 230 seconds, is treated with 6 pounds of fuming sulfuric acid per gallon of oil in one-half pound dumps. After the separation of the acid sludge, the acidtrcatcd oil is treated with a suitable alcohol, for example, ethyl alcohol of about 6 percent strength to remove crude preferentially oil-soluble petroleum sulfonic acids. The alcoholic layer containing the crude sulfonic acids is then treated with lime, preferably in the form of a lime slurry to neutralize the sult'onic acids. The mixture is allowed to settle, the alcohol layer containing the calcium mahogany salt is drawn off and then distilled to remove the alcohol therefrom. The resultant calcium salt of the preferentially oil-soluble petroleum sulfonic acids is usually of 70 percent to 80 percent concentration in unreacted oil. To facilitate the handling of the salt, it is preferred to further dilute the salt with a petroleum oil of suitable viscosity to a concentration of about 35-40 percent.

Preparation of the inventive greases may be carried out in a variety of ways. One preferred method uses a pro-formed mixture of the aluminum soap and the alkaline earth metal salt, in proportions sufficient to afford a grease of desired salt content, and add this mixture to a minor proportion of the oil with stirring to form a smooth slurry. After this, the balance of the oil is added and the mixture heated to about 280-320 F. (preferably above 290 F.) until clear and free of foam, then slowly cooled to room temperature and milled in a colloid mill or homogenizer, advantageously after aging for several hours in the 120-175 F. range to obtain stable aluminum soap crystals. Alternatively, the aluminum soap powder alone is dispersed in a small portion of the oil at low temperature and then the alkaline earth salt and the balance of the oil are added.

To illustrate the preparation and performance of the inventive greases, several batches of grease were made and tested. For their preparation, the aluminum distea-,;,

rate powder is stirred into 1 /2 times its weight of virgin distillate oil (not solvent extracted, SUS viscosity at 100:

F. of 80 seconds). When a smooth slurry is obtaine'gflthe calcium mahogany salt described earlier and the ance of the oil are added. The mixture is then heat 0;. 00 F. with stirring and held until clear and i of foam. The batch is then filled and allowed to ic'ool'to room temperature. After cooling the produot is milled at a coarse setting.

Tests of the greases are made as follows:

(1) PenetrationASTM 13-2 -56T. A measure of grease hardness or consistency gained by measuring the distance a falling weigh d one-quarter inch cone enters a cup of grease.

(2) Mechanical stabili to change upon physic .The resistance of a grease orking is measured by determining the ASTM penetration on a grease as obtained from the mill or homogenizer, and again after working 60 strokes in the ASTM D-217-52T worker. The percentage change in penetration is taken as a quantitative indication of the mechanical stability.

The following results are obtained:

Thus it is evident that there has been provided, in accordance with the invention, an improved lubricant grease. While the invention has been described in conjunction with preferred embodiments thereof, these are by way of illustration only and accordingly any alternatives, modifications, and variations thereof such as fall within the spirit and broad scope of the appended claims are embraced thereby.

I claim:

1. A lubricant grease composition comprising a major proportion of a mineral lubricating oil, from about 5 to about 10 weight percent of an aluminum soap of a fatty acid having about 10 to 30 carbon atoms per molecule and from about 0.05 to about 1 weight percent of an alkaline earth metal salt of a preferentially oil-soluble petroleum sulfonic acid having a molecular weight of from about 350 to about 525.

2. The grease composition of claim 1 wherein said aluminum soap is aluminum distearate.

3. The grease composition of claim 1 wherein said alkaline earth metal is calcium.

References Cited by the Examiner UNITED STATES PATENTS Re. 23,082 1/1949 Zimmer et al 252-332 2,521,395 9/1950 Morway et al 25237 2,629,692 2/ 1953 Liehe 25233.2

FOREIGN PATENTS 525,236 5/1956 Canada.

OTHER REFERENCES Manufacture 8: Application of Lubricating Greases, by Boner, Reinhold Pub. Corp., New York, 1954, pages 293-296 and 321-322.

DANIEL E. WYMAN, Primary Examiner.

I. R. LIEBERMAN, Examiner.

I. VAUGHN, Assistant Examiner.

Claims

1. A LUBRICANT GREASE COMPOSITION COMPRISING A MAJOR PROPORTION OF A MINERAL LUBRICATING OIL, FROM ABOUT 5 TO ABOUT 10 WEIGHT PERCENT OF AN ALUMINUM SOAP OF A FATTY ACID HAVING ABOUT 10 TO 30 CARBON ATOMS PER MOLECULE AND FROM AOUT 0.05 TO ABOUT 1 WEIGHT PERCENT OF AN ALKALINE EARTH METAL SALT OF A PREFERENTIALLY OIL-SOLUBLE PETROLEUM SULFONIC ACID HAVING A MOLECULAR WEIGHT OF FROM ABOUT 350 TO ABOUT 525.