US3511781A - Complex aluminum greases of enhanced stability - Google Patents

Description

United States Patent Int. Cl. C10m 5/16 U.S. Cl. 252-36 6 Claims This invention concerns novel improved grease compositions having as their grease thickener aluminum carboxylate salts. More particularly, this invention concerns novel grease compositions having enhanced stability comprising novel grease compositions having aluminum carboxylate salts as grease thickeners and alkali meta aroates as stabilizers. 1

Complex aluminum carboxylate greases are well known in the art and have been reported in numerous patents (see U.S. Pat. Nos. 2,768,138, 2,719,826, 2,654,710 and 2,599,553). The aluminum soap thickeners are described as having at least 2 dissimilar substantially hydrocarbonaceous organic anions having certain characteristics. The organic anions are generally oleophilic; however, one of the organo anions of the complex soap molecule has a greater oil solubility than the other organo anion of the same soap molecule. Further on, the aluminum di soaps are described as the aluminum di-soaps of the more soluble organo-anions (i.e., the relatively oleophilic anions) are soluble in an amount of at least 5 percent (by volume) at 400 F. in petroleum white oil having viscosity characteristics 'of 346 SSU at 100 F. and 54 SSU at 210 F. and having a viscosity index of 92. That is, at 400 F., 5 percent of the aluminum soap of the oleophilic organo anion will form a true solution in the petroleum white oil.

On the other hand, the aluminum soaps of the less soluble organo anions (i.e., the relatively oleophobic anions) are soluble in the above white oil in an amount of less thanl percent at 400 F. That is, at 400 F. less than 1 percent (from 0 percent to about 1 percent) [by volume] of the aluminum soap containing the oleophobic anions will dissolve in the white oil to form a true solution.

The carboxylic acids from which the oleophilic anions are derived are illustrated by caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, l2-hydroxystearic acid, arachidic acid, melissic acid, oleic acid, linoleic acid, etc. The preferred acids are stearic acid and hydroxystearic acid. The preferred carboxylic acids have from 14 to 22 carbon atoms, more usually from 16 to 18 carbon atoms.

The relatively oleophobic anions are substantially hydrocarbon in structure, are from about 7 to 12 carbon atoms and have an aromatic hydrocarbon ring (benzene). Illustrative of such acids are benzoic acid, toluic acid, ethylbenzoic acid, phenylacetic acid, phenylpropionic acid, salicyclic acid, etc. The preferred acids are those of from 7 to' 9 carbon atoms having the carboxyl group bonded to the benzene ring, e.g., benzoic acid, toluic acid, dimethylbenzoic acid, and ethylbenzoic acid.

While any of the methods of preparation disclosed in the various patents indicated above might be used, a preferred method of preparation is disclosed in copending application Koundakjian and Dreher, Ser. No. 331,127, filed Dec. 17, 1963, now U.S. Pat. No. 3,345,291. Accordingly, approximately 1.5 to 2.5 molar parts of the oleophilic acid and oleophobic acid, in which the mole ratio of the oleophilic acid to the oleophobic acid is in the range of from about 0.25 :1 to 4: 1, approximately 1 molar part of a lower aluminum alcoholate, from 0 to 1.5 molar parts of water and a large molar excess 3,511,781 Patented May 12, 1970 "ice of an oil of lubricating viscosity are heated to a temperature in the range of about 150'to 300 F., until reaction of the alcoholate with the acids is substantially complete, then a quantity of water is added in the range of 0.05 to 10 molar parts and at least suflicient to bring the total water introduced to at least about 0.5 molar part, and the resultant mixture is vigorously agitated at a temperature of from about 200 to 500 F. The grease is then ready to be used.

It is found, however, that after long periods of time, particularly at elevated temperatures, the grease begins to liquefy. In attempting to stabilize the grease, many of the known commercial stabilizing agents are found to be ineffective or have detrimental side eifects, particularly in the presence of common additives, such as the filler, zinc oxide, or the common rust inhibitor, sodium nitrite.

Pursuant to this invention, alkali metal aroates (aromatic carboxylic acids)-the alkali metal is of atomic number 3 to 19, preferably 11 (sodium) and the aroate is of from 7 to 12 carbons, preferably benzoic acid-are added in from about 0.1 to 20 weight percent, more usually 2 to 7 weight percent to the complex aluminum grease composition to provide a composition with enhanced stability at elevatedtemperatures. The alkali metal aroate may be added during the preparation of the grease or subsequent to its preparation.

The basic complex aluminum soap may be described by the general formula:

0 (O-iL-R):

in which R is an aliphatic group having 8 to about 30 carbon atoms, Ar is an aromatic radical, preferably a monocyclic hydrocarbon radical, R is either hydrogen or a lower aliphatic hydrocarbon radical, at least one-half of R being hydrogen, x is at least 0.25, y is at least 0.25, the sum ofx and y is from 1.5 to 2.5, and z is from 0.5 to 1.5. The aluminum is trivalent in the. above formula and, therefore, the sum of x, y and z is 3. However, this formula is not intended to indicate the actual structure of the aluminum salt in the grease, but rather indicates the stoichiometry between the aluminum cation and the anions.

Illustrative of R, which is derived from the lower alcoholates used, are methyl, ethyl, propyl, isopropyl, butyl, or mixtures thereof, namely alkyl groups of from 1 to 6 carbon atoms.

The oil component of the grease is a hydrocarbon oil of lubricating viscosity derived from petroleum or synthesized. Description of the various oils is found in U.S. Pat. No. 2,768,138. These oils may be mixed base, naphthenic based, asphaltic based or paraflin based. The synthetic oils may be derived by the polymerization of ethylene, propylene, isobutylene, or other hydrocarbon olefin to an oil of the desired viscosity.

As indicated, the alkali metal aroate may be added together with the aluminum alcoholate and fatty acids or may be added to the already prepared grease.

The following example is offered by way of illustration and not by way of limitation.

EXAMPLE 1 A 1,600 pound batch of grease was prepared by the process of this invention. The components of the batch were 64.8 pounds stearic acid, 36.2 pounds of benzoic acid, 53.1 pounds of aluminum isopropoxide, 1,320 pounds of white oil, pounds of sodium benzoate, 32 pounds of zinc oxide, 8 pounds of sodium nitrite and 6.2 pounds of water.

he stearic acid, benzoic acid and 150 gallons of e oil were charged to a mixer and heated to 220 F. agitation. After the acids were dissolved, the soluwas circulated from the mixer to a Charlotte mill back to the mixer. The aluminum isopropoxide was d to the mixer over a 30-minute period while agitain the mixer was maintained and circulation of the ure through the Charlotte mill was maintained. The llatlOIl and agitation were continued for 45 minutes the temperature was maintained at 210-220 F. he end of 45 minutes, 6.2 pounds of water were d and the resultant mixture was slowly heated to F. During the heating the materials in the mixer 1 agitated, but circulation through the mill was disinued. After the temperature of 320 was reached roximately 1 hour), the reaction mixture was slowly at with continuing agitation to 230 F. During the ng the remainder of the white oil was added. When temperature of 230 F. was reached, the sodium 1e mixed with 3 gallons of water was added to the ion mixture which was then reheated to 260 F. held at that temperature for about 30 minutes to drate the reaction mixture. The reaction mixture then cooled to 200 F. and the sodium benzoate and zinc oxide added. The resultant mixture was cired-through the Charlotte mill and slowly cooled to F. When the temperature reached 160' F., it was lrawn from the mixture and passed through a filter n and packaged. hile more or less oil may be used, in general, satisry greases are obtained when the soap content of grease is in the range of about 4 to 16 weight perllowing the procedure of Example 1, greases having ng weight percents of the aluminum salts were pre- I. Also varied, was the method of introduction of odium benzoate. These greases were tested accordo the Thin Film Life Test at 250 F., both in the :nce andabsence of other additives.

TABLE 1 a n o :o

said oil to a grease, a compound of the formula:

carbon atoms, R is selected from the group consisting of hydrogen and a lower aliphatic hydrocarbon radical, at

10 least one-half of R being hydrogen, and Ar is an aromatic hydrocarbon of from 6 to 11 carbon atoms, at is at least 0.25, y is at least 0.25, the sum of x and y is from 1.5 to 2.5, z is from 0.5 to 1.5, and the sum of x, y and z is 3, and

alkali metal aroate of from 7 to 12 carbons, wherein said metal is of atomic number 3-19.

2. A composition according to claim 1, wherein said alkali metal is of atomic number 11.

3. A composition according to claim 1, wherein said alkali metal is of atomic number .11 and said alkali metal aroate is present in an amount of from about 0.1 to 10 weight percent of said composition.

4. A composition according to claim 1, wherein said alkali metal is of atomic number 11 and said alkali metal aroate is present in amount of about 5 weight percent of said composition.

5. A lubricating oil composition comprising an oil of 30 lubricating viscosity and in an amount suflicient to thicken said oil to a grease, a compound-of the formula:

gen and methoxy, at least one-half of R being hydrogen,

E F o H I (Amounts are reported as weight percent) mass A 100 95 97 aluminum benzoats stearate hydroxide in white 011 having 468 SUS at 100 F. and 62 BUS at 210 F. aluminum benzoate steer-ate hydroxide in white 011 having 466 SUS at 100 F. and 62 SUS at 210 F.

um benzoate milled into the grease with Three Roll Mill lium benozate added as water solution and water then removed by heating.

is evident from the above table that a great extenx is at least 0.25, y is at least 0.25, the sum of x and y of useful life is obtained by the addition of sodium ateas exemplary of alkali metal aroatesto the inum complex greases. Not only is this evident with Iasic grease itself, but more important, it is also at in the presence of common commercial additives ently added to-greases. Sodium benzoate finds paruse for those greases used in machines in propinof food. These greases which generally employ oil, sodiunrnitrite as their rust inhibitor and zinc as a filler and colorant, are greatly improved in useful life by the addition of small amounts of m benzoate.

will be evident to those skilled in the art, various fications on this invention can be made or followed, e light of the foregoing disclosure and discussion, rut departing from the spirit or scope of the disre' or from the scope of the following claims. laim: A lubricating oil composition comprising an oil of eating viscosity and in an amount suflicient to thicken is from 1.5 to 2.5, z is from 0.5 to 1.5 and the sum of x, y andz is 3, and

in an amount suflicient to provide stabilization sodium benzoate.

6. A composition according to claim 5, wherein said sodium benzoate is present in an amount of from about 5 weight percent of said composition.

References Cited UNITED STATES 1 PATENTS 2,182,137 12/1939 Ricketts 252- -41 2,431,760 12/1941 Licata 252-36 2,599,553 6/1952 Hotten 2s2 35 0 DANIEL E. WYMAN, Primary Examiner C. F. DEES, Assistant Examiner U.S. Cl. X.R.

in an amount suflicient to provide stabilization an

Claims (1)

1. A LUBRICATING OIL COMPOSITION COMPRISING AN OIL OF LUBRICATING VISCOSITY AND IN AN AMOUNT SUFFICIENT TO THICKEN SAID OIL TO A GREASE, A COMPOUND OF THE FORMULA: