US3514400A - Complex aluminum greases of enhanced stability - Google Patents

Description

. US. Cl. 252-18 3,514,400 COMPLEX ALUMINUM GREASES OF ENHANCED STABILITY Bruce W. Hotten, Orinda, Califi, assignor to Chevron Research Company, San Francisco, Calif., a corporation of Delaware No Drawing. Continuation-impart of application Ser. No. 451,068, Apr. 26, 1965. This application July 24, 1967, Ser. No. 655,350

Int. Cl. C10m 5/14, 5/12, 5/02 a ,7 .6 Claims ABSTRACT OF THE DISCLOSURE Greases thickened with partially neutralized aluminum mixed carboxylic acid salts having enhanced oxidative and thermal stability, resulting from the addition of alkali metal aroates in combination with zinc oxide. The greases find particular use for lubricating machinery employed in the presence of food.

CROSS-REFERENCES TO RELATED APPLICATIONS This application is a continuation-in-part of application Ser. No. 451,068, filed Apr. 26, 1965.

BACKGROUND OF THE INVENTION Field of the invention Lubricants used in machinery for food processing not only must fulfill their normal lubricant function, but also are severely limited to materials approved by the Food and Drug Administration. Therefore, in preparing greases to be used in food processing machinery, not only must the thickener be acceptable, but any additives in the grease almost must be acceptable so as not to be possible contaminants in food. Many additives which ordinarily might find use in enhancing the properties of a grease cannot be used in greases for food processing machinery.

Description of the prior art SUMMARY OF THE INVENTION Oxidative and thermally stabilized aluminum salt thickened greases are provided comprising an aluminum base partially neutralized with a mixture of dissimilar carboxylates, namely an aromatic carboxylic acid and oleophilic aliphatic carboxylic acid, and as stabilizers, an alkali metal aroate and zinc oxide.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Basic complex aluminum soap The aluminum soap thickeners have at least 2 dissimilar substantially hydrocarbonaceous organic anions having certain characteristics. One of the organo carboxylate anions of the complex soap molecule has a greater oil solubility than the other organic carboxylate anion of the: same soap molecule. The aluminum di-soaps of the .fnited States Patent 0 ice more soluble organo carboxylate anions (i.e., the relatively oleophilic anions) are soluble in an amount of at least 5% (by volume) at 400 F. in petroleum white oil having viscosity characteristics of 34-6 SUS at F. and 54 SUS at 210 F. and having a viscosity index of 92. By contrast, the aluminum soaps of the less soluble organic carboxylate anions (i.e., the relatively oleophobic anions) are soluble in the same white oil in an amount of less than 1% at 400 F.

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, 12- hydroxystearic acid, arachidic acid, melissic acid, oleic acid, linoleic acid, etc. The preferred acids are stearic acid and hydroxystearic acid. The preferred carboxylic acids are the hydrocarbon and hydroxy hydrocarbon carboxylic acids having from 14 to 22 carbon atoms, more usually from 16 to 18 carbon atoms.

The relatively oleophobic anions are substantially bydrocarbon 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.

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

(O- (R'0).A1 o

(O%Ar), in which R is an aliphatic group having 7 to about 29 carbon atoms, Ar is an aromatic hydrocarbon radical, preferably a monocyclic hydrocarbon radical, R is either hydrogen or a lower aliphatic hydrocarbon radical (1 to 6 carbon atoms), at least one-half of R being hydrogen, x is at least 0.25, y is at least 0.25, the sum of x 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 struture 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.

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 US. Pat. 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 of an oil of lubricating viscosity are heated to a temperature in the range of about 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, at least sufiicient 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.

When preparing the grease, the alkali metal aroate may be added together with the aluminum alcoholate and carboxylic acids or may be subsequently milled in with the prepared grease. The other additives will normally be incorporated during the preparation of the grease, conveniently being added at the same time as the aluminum alcoholate and carboxylic acids.

Alkali metal aroates Included in the grease is an alkali metal aroate, the alkali metal being of atomic number 3 to 19 and preferably 11 (sodium). Said aroate is an alkali metal salt of an aromatic monocarboxylic acid having 7-12 carbon atoms and having the carboxyl carbon atom bonded to an aromatic ring carbon atom. The preferred aromatic monocarboxylic acid is benzoic acid.

Other materials The alkali metal aroate is generally used in combination with zinc oxide. While zinc oxide is normally used as a filler, in the present invention when used in combination with an alkali metal aroate, it greatly extends the oxidative and thermal life of the aluminum complex salt thickener.

Other materials which are normally present are rust inhibitors, particularly sodium nitrite, and viscosity index improvers.

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 US. Pat. No. 2,768,138. These oils may be mixed base, naphthenic base, asphaltic base or parafiin base. The synthetic oils may be derived by the polymerization of ethylene, propylene, isobutylene, or other hydrocarbon olefin to an oil of the desired viscosity.

to the mixer. The aluminum isopropoxide was added to the mixer over a 30-minute period while agitation in the mixer was maintained and circulation of the mixture through the Charlotte mill was maintained.

The circulation and agitation were continued for minutes, while the temperature was maintained at 210 to 220 F. At the end of 45 minutes, 6.2 pounds of water was added and the resultant mixture was slowly heated to 320 F. During the heating, the materials in the mixer were agitated, but circulation through the mill was discontinued. After the temperature of 320 F. was reached (approximately 1 hour), the reaction mixture was slowly cooled with continuing agitation to 230 F. During the cooling, the remainder of the white oil was added.

When the temperature of 230 F. was reached, the sodium nitrite mixed with 3 gallons of water was added to the reaction mixture, which was then reheated to 260 F., and held at that temperature for about 30 minutes to dehydrate the reaction mixture. The reaction mixture was then cooled to 200 F. and the sodium benzoate and the zinc oxide added.

The resultant mixture was circulated through the Charlotte mill and slowly cooled to 160 F. When the temperature reached 160 F., it was withdrawn from the mixture and passed through a filter screen and packaged.

Following the procedure of Example I, greases having varying Weight percents of the aluminum salts were prepared. Also varied was the method of introduction of the sodium benzoate. These greases were tested according to the Thin Film Life Test at 250 F., both in the presence and absence of other additives. A description of the Thin -Film Life Test is found in NLGI Spokesman, May 1957, p. 13.

TABLE I Amounts are reported as weight per cent A B C D E F G H I Base grease A l 100 95 97 92 Base grease B 98 97 93 97 03 Acryloid J17 0. .5 0. 5 Zinc oxide 2.0 2. 0 2.0 2.0 2.0 2.0 2.0 Sodium nitrite. 0, 5 0. 5 Sodium benzoate 6. 5.0 3 1. 0 3 5. 0 4 1.0 4 5.0 Thin film life, hr. at 250 F 24 300 24 168 48 120 l, 128 120 1, 128

l 12% aluminum benzoate stearate hydroxide in White Oil having 466 SUS at 100 F. and 62 SUS at 210 F 2 9.2% aluminum benzoate stearate hydroxide in White Oil having 466 SUS at 100 F. and 62 SUS at 3 Sodium benzoate milled into the g 4 Sodium benzoate added as water s AMOUNTS The amount of thickener will generally be in the range of about 4 to 16 weight percent, more usually in the range of about 7 to 15 weight percent of the total composition. The alkali metal aroate will normally be present in an amount of from 0.1 to 20 weight percent more usually from 1 to 7 weight percent based on the total composition. The zinc oxide will normally be present in amount of about 0.5 to 5 weight percent, more usually in the range of about 1 to 3 weight percent. Other additives which may be present such as sodium nitrite or polymeric viscosity index improvers will normally be present in a total amount of from about 0.1 to 2 weight percent, more usually from about 0.5 to 1.5 weight percent. The remainder will be the lubricating oil.

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

EXAMPLE I A 1,600 pound batch of grease was prepared as follows. The components of the batch were 64.8 pounds of stearic acid, 36.2 pounds of benzoic acid, 53.1 pounds of aluminum isopropoxide, 1,320 pounds of white oil, 8 0 pounds of sodium benzoate, 32 pounds of zinc oxide, 8 pounds of sodium nitrite and 6.2 pounds of water.

The stearic acid, benzoic acid and 150 gallons of white oil were charged to a mixer and heated to 220 F. with agitation. After the acids were dissolved, the solution was circulated from the mixer to a Charlotte mill and back Base Grease 1 Grease+Additive 2 Penetration worked 311 312 Dropping point 487 480 Percent 011 separation:

At 210 F. for 30 hrs. (FTM 6.16 4.02

N 0. 791-321). 6. 65 At ambient temperatures 5. 5.0

for 24 hrs. (ASTM D 1742). 6. 13

7.5% aluminum benzoate stearate 466 SUS at F. and 62 SUS at 210 ?Abo ve base grease plus 1.7% zinc oxide and 3.6% sodium benzoate mllled into the base grease (the difference in the results is within experimental error and can be explained on the basis of the additional milling).

ydroxide in white oil having It is evident from the above tables that a great extension of useful life is obtained by the addition of sodium benzoateas exemplary of alkali metal aroatesto the aluminum complex greases. Not only is this evident with the sodium benzoate by itself, but when used in combination with zinc oxide, a surprisingly greater extension of the useful lifetime of the grease is obtained. Moreover, these additives are effective with other additives normally used in the grease. These additives are particularly effective with'white oil, which is generally employed for greases to be used in machines in propinquity of food.

As will be evident to those skilled in the art, various modifications on this invention can be made or followed, in the light of the foregoing disclosure and discussion, without departing from the spirit or scope of the disclosure or from the scope of the following claims.

I claim:

1AA 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:

in which R is an aliphatic group having from about 7 to 29 carbon atoms, R is selected from the group consisting of hydrogen and a lower aliphatic hydrocarbon radical, at least one-half of R being hydrogen, and Ar is an aromatic hydrocarbon of from 6 to 11 carbon atoms, x 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,

in an amount sufiicient to provide thermal and oxidative stabilization, an alkali metal salt of an aromatic monocarboxylic acid having 7-12 carbon atoms and having the car boxyl carbon atom bonded to an aromatic ring carbon atom, wherein said? metal is of atomic number 3 to 19, and zinc oxide.

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, said alkali metal salt is present in an amount of from about 0.1 to 10 weight percent of said composition, and said zinc oxide is present in an amount of from about 0.5 to 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 salt is present in amount of about 5 weight percent of said composition.

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

(RO),--Al O (OCAr) in which RCO is 12-hydroxystearoyloxy, ArCO is benzoyloxy, R is selected from the group consisting of hydrogen and methoxy, at least one-half of R being hydrogen, x 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

in an amount sufficient to provide thermal and oxidative stabilization, sodium benzoate and zinc oxide.

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 and said zinc oxide is present in from about 1 to 3 weight percent.

References Cited UNITED STATES PATENTS 2,043,638 6/1936 Watts 252-11 2,182,137 12/1939 Ricketts 2524l 2,599,553 6/1952 Hotten 25237.7 2,671,758 3/1954 Vinograd et al. 252-48 2,860,104 11/ 1958 Peterson et al 25228 OTHER REFERENCES Manufacture and Application of Lubricating Greases by Boner, Reinhold Pub. Corp., New York, 1954, p. 781.

DANIEL E. WYMAN, Primary Examiner I. VAUGHN, Assistant Examiner US. Cl. X.R. 25225, 400