US2521395A - Aluminum soap greases - Google Patents

Description

iatented Sept. 5, 1950.

uurnzo STATES PATENT OFFICE ALUMINUM SOAP GREASES Arnold J. Morway, Clark Township, Union County,

N. J., and Alan Beerbower, Baltimore, Md., as-

signors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application April 7, 1948, Serial No. 19,633

1 Claim. (Cl. 252-3'7) soap grease having desirable characteristics of stability and consistency notwithstanding the use of rapid cooling techniques.

It has {been known in the prior art that aluminum soap base greases may be improved in certain respects by the incorporation therein of various modifying ingredients. Thus in the patent to Zimmer and Morway, No. 2,365,037, there is disclosed an aluminum soap base grease in which is incorporated a small amount of aluminum naphthenate or aluminum oleate with a small quantity of a free acid, such as oleic acid or stearic acid. Also, in the patent to Sproule and Zimmer, No. 2,394,567, there is described a process for producing an aluminum soap grease which comprises the use of a phenolic compound as a modifier or stabilizer. This patent specifically mentions the use of tertiary octyl phenol and points out that by the use of the phenolic modifier aluminum soap greases may be rapidly cooled and still have a desirable consistency and gel structure, a difliculty which had previously been encountered in the continuous or rapid production of aluminum soap greases.

In the production of aluminum soap greases, for example greases containing aluminum stearate, the continuous and semi-continuous methods have been used in the past with only limited success. It has been found that without grease structure modifiers, such as those referred to above, grease produced by the use of continuous and semi-continuous apparatus with quick cooling apparatus sets up in hard crusts resulting in graininess and considerable syneresis. The use of an alkylated phenolic modifier as described in the patent to Sproule and Zimmer, No. 2,394,567, mentioned above, has resulted in some improvement in the grease but it has been found that there is a breakdown in consistency when greases produced by the continuous meth- 0d are dispensed in high pressure grease guns and the like or otherwise subjected to substantial shearing stresses. Even with the alkylated phenol modifier, when aluminum soap greases are subjected to high shearing stresses, the grease structure is temporarily broken down, the composition reverting to a very soft fluid or semifiuid mass which recovers part of this lost consistency in standing (delayed thixotropy) but not sufiiciently fast to prevent the grease from running out of bearings or dripping onto the floors and parts of machinery where it is not desired. Such partial breakdown in structure obviously is objectionable to those who handle the lubricant.

On the other hand, greases produced by the general process described in the Zimmer and Morway patent, No. ,365,037, may in some instances lack the uniformity in consistency and structure which is desired, being subject to the deficiencies more fully pointed out in the Sproule and Zimmer patent referred to above.

We have found that by the addition of a substantially saturated acid in a quantity of approximately 10 to 20% of the aluminum soap, the amount of the alkylated phenol modifier hitherto required may be considerably reduced and also the amount of aluminum soap required to obtain a given grease consistency or hardness may be reduced appreciably. The structure and stability of the lubricant are improved even when the quantities of these other materials are appreciably reduced. Apparently the addition of a saturated fatty acid overcomes the tendency of aluminum soap greases to break down unduly under shearing stresses. Greases produced in this manner have been found to be exceptionally satisfactory for automotive chassis lubrication and related uses. The excellent qualities of adhesiveness to metal and rapid recovery of body after working make the aluminum soap greases, such as aluminum stearate greases, especially desirable for this purpose.

volved in modern high pressure grease guns and the like. In view of the structural breakdown mentioned, and also because grease packages for the trade had to be allowed to stand for some 96 hours or longer before the grease would revert to a final solid grease structure ready for final inspection, further improvements in stability have been needed and are among the main objects of this invention.

A grease having good shear stability, produced by continuous methods involving rapid cooling, was compounded comprising 6.0% aluminum stearate of commercial grade and 1.2% of hydrogenated fish oil acids, which are substantially saturated acids having between 12 andIZZZ carbon atoms per molecule. As a modifier, 0.56% iso octyl phenol was added, the soap and modifier being mixed into about 92% of a low cold test mineral oil having a viscosity of 900 to 1000 S. S. U. at 100 F. with addition of a small amount, about 0.25% of a tackiness agent, such as an oil solution of polybutene.

All of the above materials were charged to a grease kettle and the temperature raised to about 300 F. while mixing. At this temperature a fluid homogeneous mass was formed. The grease was cooling progresses. It prevents the grease from forming soft cores in shipping containers, a difficulty that formerly arose with frequency in aluminum soap greases produced by the rapid cooling process. Also the grease does not require a long standing time for reversion to a final solid grease structure. What is even more important, it shows no signs of syneresis or oil separation in containers over longer periods of time, even when shallow wells are dug into the grease to enhance the tendency toward oil separation. However, the most important effect of the added acid is to prevent structure breakdown of the grease under shearing stress. The following table shows the various characteristics of greases containing different amounts of aluminum soap (aluminum ste'aratm the 'isooctyl phenol structure modifier siderably less in theexamples where the fatty acid was employed. The optimum composition covered by this table appears to be that consisting of 3% aluminum steara'te, 0.56% iso-o'ctyl phenol and 1.2% fatty acid.

TABLE I Grlizizgeavnvflltgggg gig; Grease 1gb varnymg amounts of added amount of modifier acid an sma amount of modifier Formulation 1 Aluminum Stearate Per cent 8.50 V 7.00 6.00 6.00 6.00 Iso-Octyl Phenol do 1.70 1. 40 0. 56 0. 50 '56 Tackiness Agent (Polybutene-inoil) do 0v 25 0.25 0.25 0:25 0. 25 Mineral Oil (900/1000 Via/100 F.) (10 89.55 91.35 91.99 92. 28 93.19 Saturated Acid of 12-22 carbon atoms. do 1. 0.00

Properties ASTM Penetration (unworked) 77 F 218 190 205 220 226 ASTM Penetration wol ked Strokes. 332 343 320 318 307 ASTM Penetration Worked 150 Strokes 345 354' 325 1322: 305 ASTM Penetration Worked 300 Strokes 344 354 331 321 317 ASTM Penetration Worked 600 Smokes 347 370 343 328; 314 ASTM Penetration Worked 1200'Strokcs- 376 395 .348 343 332 ASTM Penetration Worked 1800 Strokes 380 395 352 347 325 Penetration after passage through a standard commercial-air operated grease gun 379 371 v 338 341 3'40 Appearance in'container after reversion to solid grease Excellent Good Exeellent- Excellent Syneresis Syneresis after three months of normal bulk plant storage in lb. eontoiners Large Large None None Large packaging and was ready for final inspection in one-half to two hours after packaging.

Stearic acid may be used as the saturated iat ty acid or various hydrogenated vegetable or fish oil acids which are commercially available maybe employed. lhe optimum quantity of the free or excess fatty acid to be used appears to be in the range of about 10 to 20%, based on the quantity of aluminum soap employed. The aluminum soap is preferably aluminum stearate although other substantially saturated aluminum soaps having between 12 and 22 carbon atoms may be used if desired. The added or excess acid appears to have a synergisticeifect on the grease modifier (iso-octyl phenol, as in the example given above). For this reason a considerably lesser-quantity of the modifier can be employed than in thecase where no free acid is used.

"'2 of the in combination with s "zali' r amounts or the modifier modifies the structure sufliciently to keep the composition substantially in a fluid state while the rapid -source=of the aluminum s'tearate, apparently .be-

cause some aluminum stearates of commercial grade include appreciable quantities of free fatty acids. However, when purchasing aluminum stearate this free acid is held to aminimum by specification for economical reasons. Thus, where the aluminum soap already contains some free fatty acid, the effects of the addition of further acid will vary, depending on the original acid content of the soap. .To determine the effect of the variations of different aluminum stearates, various batches of lubricating compositions were prepared by both rapid cooling .and conventional pan cooling methods. The mineral oil used was a blend of lubricating oils having .a viscosity after blending of 900 S. 8.2-1 at 100 Soap contents of the'finished greases were adjusted to give products :having worked penetrations between 320 and 340. All of the greases prepared by rapid cooling softened excessively when subjected to shear in a grease worker .or in a standard grease gun. Table II shows the comparative structure stability characteristics of three r ases pr pared from commercial aluminum stearates by the continuous cooler and the pan methods, respectively.

TABLE 'III 1 good performance in commercial grease dispensing equipment. I

1 High pressure grease gun with needle fitting.

. The data in Table II show that'an aluminum stearate pressure type lubricant possessing adequate structure stability under shear could not be prepared by rapid cooling methods without a change in formula, it being noted that no fatty acids. were added. The formulation was improved to an unexpected degree by the addition of stearic acid, or of a hydrogenated fish oil acid which is approximately equivalent to stearic acid. The quantity of acid employed in the latter series of tests was about 10% of the soap content and the is'o-octyl phenol content, which had been of the soap content in the experiments covered by Table II, was reduced to 10%. A typical product containing 7.0% of aluminum stearate,

below in Table III.

TABLE I11 Aluminum Soap Source A B 0 Manufacturing Process Cooler Cooler Pan Cooler Formulation Aluminum Stearate "percent" 6.00 6.00 9.75 7.00 Hydrogenated Fish Oil Acid l'so-octyl Phenol 110.... 0. 80 0.60 0. 70 'lackiness Agent o 0. 0. 25 0. 25 0. 25 Mineral Lubricating Oil do 91. 95 91. 95 90.00 91.35

ASTM Peurtrmz'ous Unworked 190 212 200 After 60 Strokes 320 320 332 331 After 1,800 Strokes 352 348 360 345 After Passage Through Grease Gun. 338 348 352 328 Appearance Good Good Good Good.

The aluminum stearate grease obtained from commercial source C listed in the table above had particularly good structure stability when prepared on a laboratory scale by rapid cooling. It appears to have excellent structure stability even under conditions of high shear and to give Structure stability of aluminum stearate pressure lubricant Aluminum Soap Source A B 7 0 Manufacturing Process Cooler Pan Cooler Pan Cooler Pan Formulation Y Aluminum Stearate percent '7. 00 8. 9. 8. 00 6. 50 Iso-octyl Phenol d0 1. 40 1. 70 l. 60 Tackmess A ent (10---. 0. 25 O. 25 0. 25 O. 25 0. 25 0. 25 Mineral Oil do 91. 35 93. 75 89. 90. 75 90. 15 93. 25

AS TM Penetrations I Unworlzed 196 161 218 177 241 211 After Str 332 320 332 339 326 335 After 1800 Strokes 395 338 380 352 382 360 After Passage Through Gun 1 371 347 379 362 378 V 388 One Hour After Passage Through Gun 1 327 324 330 345 360 348 The quantities offatty acid to be added and the alkylated phenol modifier appear to-be'some what critical. The amounts used may be varied somewhat, depending upon the characteristics of the aluminum soaps with which they are used. Under some conditions both additives may be used in quantities as little as 0.1 to as much as 2.0% by weight, based on the total grease composition. The fatty acid may be from 1 to 3 times the quantity of the alkyl phenol. Generally speaking, the quantities employed will be between 0.25 and 2.0% for the fatty acid and 0.25 and 1.25% for the alkylated phenol modifier. For greases containing soaps of good commercial quality the range may often be even narrower. Based on the amount of soap used in the grease, the added fatty acid may be from about 10 to 20% by weight. A good over-all formula for the finished lubricant appears to be 5 to 9% by weight of aluminum soap of saturated or substantially saturated fatty acid, for example aluminum stearate, 89 to 94% of mineral lubricating oil of appropriate grade, i. e. of 35 to 1000 S. S. U. viscosity at 210 F. and 0.25 to 1.25% of a substantially saturated fatty acid, with 0.25 to 1.25% of modifier. The added acid is preferably stearic acid, although the other saturated fatty acids having between 12 and 22 carbon atoms, and mixtures thereof, may be employed. The phenol type modifier is preferably an alkylated phenol, particularly iso-octyl phenol, but other phenols such as resorcinol may be used, as described in application Serial No. 638,431 by Beerbower and Zimmer, now Patent No. 2,449,580. A tackiness agent also is usually desirable, though not indispensable. It is commonly used in quantities of 0.1 to 0.5% and other conventional additives such as corrosion inhibitors, oxidation inhibitors, extreme pressure agents, and the like, may be employed, as will be understood by those skilled in the art.

The following table gives still further data which were obtained on Various samples of grease prepared from aluminum soaps obtained from various sources. It will be noted that good balance is required between the aluminum stearate or other soap, the fatty acid, and the alkylated phenol. Where the quantity of soap is reduced, the added acid needs to be increased somewhat. These data pertain to the rapid cooling process which has been found more difficult to apply to the production of satisfactory aluminum soap greases than to some of the other types of greases under commercial manufacture.