US2737493A - Lithium soap grease with phosphate ester vehicle - Google Patents

Description

7 Q I I M r 2,131,493 O Y Patented Mar. 6, 1956 soAPGnEAs'E WITH PHOSPHATE ESTER VEHICLE Richard A. Bntcosk, EastHempstead, N. Y., assignor to Nonrawing. :Application December26, 1952,

. Serial N0. 328,133

reclaim-s. cum-36 This' invention has to'do with lubricating grease compositious suitabl'e -foruseovera Wide range of operating temperatures. More specifically, the present invention is concer'ned with'lithium basegreases of excellent lubricating'characterand stable when used at temperatures varying-from about '70 F. to about 300 F. and higher.

In recentyears-ademand has been created'for greases of outstanding lubricating character which retain'their grease structure during use over a wide rangeor" operating temperatures. Typical of such a demand is that created by the 'aircraft'industry. For efiicient aircraft operation, g'r'eases should have low temperature-torque properties such-that they will flow properly at temperatures'as low as about '70 F. In addition,the greases should be of 'low volatility and retain their? grease structure'at temperatures at least as-high as 300 F. Failure to retain.-grease structure results in high consumption of grease and frequent-servicing. Other desirablefeatures ofsuch greases are: homogeneity and smooth, unctuous consistency; water resistance; I resistance to oxidation; i resistance to oil separation; and resistance to sheer or breakdown upon working or milling.

The demand for greases of the foregoing specification has not been satisfied to date, except by resort to expensive operating procedures. example, that lithium base greases containing synthetic vehicles comprising esters of dibasic acids, such as di- (Z-ethyI-hexyl) sebacate and di-(iso octyl) adipate, are suitable for low temperature operations; and, in fact, such greases are used in aircraft, as reflected in Military Specification MIL-G-3278. The latter greases have the desired homogeneous nature and smooth consistency, and have satisfactory water resistance. "Yet, these lithium base greases have a weakness .in that-their ester vehicles ther object is to provide a greasewhich retains its "original character over a wide range of operating conditions. Another object'is to provide a grease with extreme pressure properties furnished by the oil -vehicle rather than by an E. P. additive. Still another object is to provide a grease characterized by a relatively low degree of volatility. Another object is to provide a'grease of desired character which can bemanu'factured by conventional greaseprocedures in conventional grease-making equipment. Other objects of the invention will be apparent from thefollowing description.

It has now-been discovered that lithium base greases containing vehicles comprising alkyl, aryl phosphate esters, and containing small amounts of particular lithium or aluminum salts, in certain proportions, make possible realization of the foregoing objects.

The vehicles or synthetic'oils of thegreases contemplated herein are confined to alkyl, 'aryl phosphatees'ters, represented by the Tel-lowing. general formula:

Rr-"O wherein R is alkylylh is aryl and R2 is either alkyl or aryl, typical of 'which groups'are: (1') alkyl such as methyl, ethyl, .propyl, butyl, amyl, 2-ethyl hexyl, iso octy-l etc. "(2) eryl-such-as phenyl, and its alkyla-ted derivativessuch as cresyl, amyl phenyl and thedike. Representative of suchuesters are: d'ibutyL-mono-phenyl phosphate; -di-(2-ethyl-hexyl), ,monophenyl phosphate; and .mono .iso .octyl, .diphenyl phosphate. Particularly advantageous .of such esters is dibutyl, mono phenyl phosphate,

'In general,'the synthetic vehicles described above and contemplated for use in the greases of this invention have a viscosity from about 40 seconds to about 150 seconds, S. U. V. at 100 F. Particularly desirable are those hav- .ing a viscosity of the order of to 60 seconds, S. U. V.,

It has been found, for

have excess volatility at temperaturespf 300 Fiand higher. Such a lossis too greatfor. long-service life of the greases in'anti friction bearings. 'Another shortcoming of-"such greases is their lack :of extreme pressure (15. P.) properties, necessitating incorporati'on'of an additive material impartin'g "P. characteristics. One approach taken to effect improvement of lithium base greases involves a special-filrn-cooling technique to obtain at 100 F. The vehicles also have low pour points and low evaporation rates at elevated temperatures.

Physical characteristics of several typical phosphate esters are'presented belowin Table I.

specific-Gmay" 0.9916.....I-.

Pour, "F

-The lithium fatty" acid" soap constituting one of "the soap or gelling components of the greases of. thisinvention, is. prepared with a fator fattyrmaterial containing from abouttwelveto about twenty-two carbonatoms per lower melting points, thus requiring their use at lower operating temperatures (e. g., below 250- F.).

It is an obi'ectof this'inventiomtherefore, tof-provide a grease eifective over a wide temperature range, particularly from about F. to about 300 F. A furmolecule. Representative of such materials -.are-vegetable, animal and fish fatty oils, and hydrogenated mate- .rials thereof. Stearin, stearic acid, cottonseed oil acids, oleic acid, palmitic acid, myristic acid,'l2ehydroxy stearic acid, hydrogenated fish oils such as .Hydrogenated-Fish Oil, Iodine No. 77 and Hydrofoliarc typical. "Preferred soaps, however, are lithium .-stearate ,-,and-: the lithium-soap of-12-hydroxystear-ic acid. Methods of preparation of lithium soaps are well-knownein the art and,- for this -reason,-detailed" discussion of the sameis omitted.

The lithium and aluminum salts contemplatedhereiu as modifying agents are salts of aliphatic monocarboxylic acids having from about six to about ten carbon atoms per molecule. Typical of such salts are lithium and aluminum salts of: hexanoic, heptanoic, octoic such as caprylic and 2-ethyl hexanoic, pelargonic and decanoic. Particularly preferred herein are lithium and aluminum octoates.

In connection with the above-mentioned modifying agents, it has been found that satisfactory grease gels could not be formed from the phosphate ester vehicles and lithium soaps described above when the modifying salts were absent. It has also been found that conventional metal soap types, such as calcium and magnesium stearates do not form gels with the phosphate esters with or without the modifying salts. It was further found that when certain proportions of the lithium and/ or aluminum salt modifying agents were used with the phosphate ester vehicles and lithium soaps, excellent grease gels could be formed. The lithium and/or aluminum salts are used in amounts of the order of 0.2 per cent to about ten per cent by weight of the grease. Generally, however, particularly advantageous behavior is realized with from about one to about three per cent of the modifying agent, with balanced proportions of the phosphate ester vehicle and lithium soap. The latter comprises from about four to about thirty per cent of the grease, and the vehicle from about sixty to about ninety-four per cent of the grease. For convenience, these balanced proportions are shown below in tabulated form:

It is to be understood that the greases of this invention can also contain other characterizing ingredients. For

5 value of the greases contemplated herein nor do they detract from the beneficial properties imparted by the lithium soap and the lithium and/or aluminum salt; rather, these characterizing materials serve to impart their cus tomary properties to the grease. In general, the characterizing material or materials are present, in total, in

amounts up to about five per cent by weight of the grease.

By way of illustration, the greases of this invention can be formed in the following manner. A preformed lithium soap and a preformed lithium and/or aluminum salt are mixed well at room temperature, about 70-80 F. with a phosphate ester vehicle. The resultant mixture is heated to a temperature from about 90 F. to about 500 F., preferably about 420 F., with constant stirring, during a period of thirty minutes to about two hours, depending upon the quantities of materials used. After the time period indicated above, the resulting liquid product is cooled to room temperature, generally requiring a period of about one to ten hours. The cooled grease product is milled to a buttery product in a suitable milling apparatus, such as Cornell homogenizer. When any additives are incorporated in the greases it is advisable to add them just prior to cooling the products.

The greases of this invention are illustrated by several examples-l through 5-tabulated in Table II below.

Provided also in Table II are comparable examples in which lithium base greases and other metal base greases, other than those contemplated herein are illustrated.

Each of the greases shown in Table II was prepared ac cording to the procedure described above, unless otherwise indicated. Consistency of the greases was deter mined in accordance with ASTM Method D 217-48 Cone Penetration of Lubricating Grease.

Table II Grease No 1 2 Ingredients:

Lithium Stearate -pereent by weight- Aluminum Octoate do Lithium O te do Lithium Laurate do Dibutyl, Monophenyl Phosphate do.- 78.00 78.00r

Iso Octyl, Diphenyl Phosphate rln Consistency 26s at: Structur Smooth"--- Smooth"--. Appearance Buttery... Buttery 400. Grainy. Fibrous Grease No 8 9 10 Ingredients:

Lithium Stearate percent by weight-.. 15.00 15.00-- 20.00 Lithium Palrnitate.do. Lithium 12 Hydroxystear do Calcium Stearate.. do.. 3.00 Aluminum Stearate do Aluminum Cnprylatae Lithium Caprylatedm.-.

Dibutyl. Monophenyl Phosph (10-...

Iso Octyl, Diphenyl Phosnhata d o D i-(2-E thyl-Hexyl) Monophenyl Phosphate Consistency Fluid. Semifluid Appearance Grainy.. Grainy Semifluid- Semifluid- Semiiiuid- Grainy Grainy Grainy 400. Grainy Grainy.

Table II.-Continued Grease No. 17 18 19 Ingredients:

Magnesium Steal-ate percent by weight Calcium Stcarate .do Aluminum stearate. do Aluminum Octoate do. Calcium Laurate .do. Lithium Alpha Hydroxy Decanoate percent by weight. Lithium stearate .do- Dibutyl, Monophenyl Phosphate .percent by weight. Iso Octyl, Diphenyl Phosp1ate percent by weight.. Consistency Appearance 80.00. Fluid. Grainy 83.00- Fluid- Grainy.

80.00. 360. S1. Grainy.

1 Experiment 25 was prepared like previous experiments but the mixture was agitated during cooling to 90 F. over a period of 45 minutes.

In reviewing the results set forth in Table II, it will be noted that greases 1 through represent compositions of the present invention. Greases 1 through 4 are smooth textured. The greases of this invention are suitable for lubrication of ball and roller bearings at low and elevated temperatures. In addition, they are characterized by low volatility at high temperatures and are further characterized by excellent film strength properties.

As a further note in connection with greases 1 through 5, each of such greases in addition to being pan cooled, was shock cooled. Each grease was poured, while hot, onto a cool surface and then worked with a spatula. The resultant greases were firm, just as they were when obtained by the pan cooling technique. In contrast,

greases 8 through 24 were unsatisfactory when shock cooled.

Greases 6 and 7 are unsatisfactory because they are grainy and approach a semifluid consistency.

Greases 8 through 24 are semi-fluid and grainy in nature, and are unsatisfactory. Grease 25 is slightly grainy and soft in consistency; it was kettle cooled, or agitated during cooling, from 420 F. to 90 F. over a period of two hours.

The greases of this invention are suitable for a wide range of industrial applications. They are, as indicated above, particularly well suited for use in aircraft, such as applied to wheel bearings, ball bearing motors, actuators.

I claim:

1. A lubricating grease comprising: at least 60 percent by weight of a dialyl monoaryl phosephate ester vehicle, a lithium fatty acid soap (I) in an amount from about four to about thirty percent by weight of the grease, and a metal salt (II) of a monocarboxylic aliphatic acid having from about six to about ten carbon atoms per molecule in an amount from about 0.2 to about ten per cent by weight of the grease, the metal of said metal salt (II) being selected from the group consisting of lithium and aluminum.

2. A grease defined by claim 1 wherein the vehicle is an ester represented by the general formula wherein R and R1 are alkyl groups, and R2 is an aryl group.

3. A grease defined by. claim 1 wherein the vehicle is dibutyl, monophenyl phosphate.

4. A grease defined by claim 1 wherein the lithium soap is lithium stearate.

5. A grease defined by claim 1 wherein the metal salt is lithium octoate.

6. A grease defined by claim 1 wherein the metal salt is aluminum octoate.

7. A lubricating grease comprising:

Per cent by weight A dialkyl monoaryl phosphate ester vehicle 82-91 A metal salt (II) of a monocarboxylic aliphatic acid having from about six to about ten carbon atoms per molecule, the metal of said salt (II) being selected from the group consisting of lith ium and aluminum 1-3 A lithium fatty acid soap (1) 8-15 8. A lubricating grease comprising about seventy-eight per cent by weight of dibutyl, monophenyl phosphate,

about twenty per cent by weight of lithium stearate and about two per cent by weight of aluminum octoate.

9. A lubricating grease comprising about seventy-eight per cent by weight of dibutyl, monophenyl phosphate, about twenty per cent by weight of lithium palmitate and about two per cent by weight of aluminum octoate.

10. A lubricating grease comprising about eightythree per cent by weight of dibutyl, monophenyl phosphate, about fifteen per cent by weight of lithium 12- hydroxy stearate and about two per cent by weight of aluminum octoate.

11. A lubricating grease comprising about ninety-two per cent by weight of dibutyl, monophenyl phosphate, about four per cent by weight of lithium stearate and about four per cent by weight of aluminum octoate.

12. The method for preparing a lithium soap lubricating grease, which comprises mixing a lithium fatty acid soap (I) in an amount from about four to about thirty per cent by weight of the total charge, with a metal salt (II) in an amount from about 0.2 to about ten per cent by weight of the total charge, and with the balance a vehicle consisting of a dialkyl monoaryl phosphate ester, said metal salt (II) being a salt of a monocarboxylic aliphatic acid having from about six to about ten carbon atoms per molecule and the metal thereof being selected from the group consisting of lithium and aluminum; heating the resultant mixture to a temperature from about F. to about 500 F., while agitating said mixture, for a period of time from about /2 hour to about four hours; cooling and milling the grease product.

13. The method as defined by claim 12 wherein the resultant mixture is heated to a temperature of about 420 F.

References Cited in the file of this patent UNITED STATES PATENTS 2,203,102 Powers June 4, 1940 2,237,336 Caprio Apr. 8, 1941 2,376,312 Morgan May 15, 1945 2,455,892 Fraser Dec. 7, 1948 2,487,080 Swenson Nov. 8, 1949 2,495,651 Butcosk Jan. 24, 1950 2,585,321 Butcosk Feb. 12, 1952 2,614,076 Moore et al Oct. 14, 1952 2,614,077 Moore et a1 Oct. 14, 1952 2,628,195 Allison et al Feb. 10, 1953 2,628,202 Allison et al. Feb. 10, 1953 2,651,616 Matthews et al. Sept. 8, 1953

Claims (1)

1. A LUBRICATING GREASE COMPRISING: AT LEAST 60 PERCENT BY WEIGHT OF A DIALYL MONOARYL PHOSEPHATE ESTER VEHICLE, A LITHIUM FATTY ACID SOAP (I) IN AN AMOUNT FROM ABOUT FOUR TO ABOUT THIRTY PER CENT BY WEIGHT OF THE GREASE, AND A METAL SALT (II) OF A MONOCARBOXYLIC ALIPHATIC ACID HAVING FROM ABOUT SIX TO ABOUT TEN CARBON ATOMS PER MOLECULE IN AN AMOUNT FROM ABOUT TEN CARBON ATOMS PER CENT BY WEIGHT OF THE GREASE, THE METAL OF SAID METAL SALT (II) BEING SELECTED FROM THE GROUP CONSISTING OF LITHIUM AND ALUMINUM.