US3170878A - Grease composition - Google Patents

Description

United States Patent .0

3,170,878 1 GREASE COMPOSITION Eldon L. Armstrong, Muliica Hill, NJ., assignor to Socony Mobil Oil Company, Inc., a corporation of New York 1 No Drawing. Filed Mar. 3, 1961, Ser. No. 93,024

2 Claims. (Cl. 252-18) This invention has to do with new grease compositions, particularly complex soap greases containing molybdenum disulfide.

Complex soap greases are well known in the art. They comprise oils containing grease-forming quantities of metal salts and soaps of a mixture of acids, such as a mixture of a low and high molecular weight acids. Typicalof such greases are calcium acetate-stearate disclosedin U.S. Patent No. 2,197,263;- barium acetatestearate disclosed in US. Patent No. 2,564,561; and calcium and lead salts and soaps of a variety of acids as described in US. Patent No. 2,898,297.

Complex soap greases have proven to be of excellent character in a npmber of applications. They are useful, for example, as multi-purpose automotive greases, serving as chassis, wheelbearing and universal joint lubricants. However, they have not been entirely satisfactory when subjected to the rigorous conditions prevailing in electric motors and generators, wherein they have been used to lubricate the armature bearings. Design of high power output generators, without increase in physical dimensions, made possible by the use of class H silicone insulation to the windings of rotating equipment, has created a need for lubricants stable under high temperature, high load, continuous operation. Lubricants must be capable of long time operation at temperatures above 200 F.

Molybdenum disulfide has been used to date in a wide variety of lubricants, including grease compositions. This compound is a comminuted, inorganic, crystalline solid having lowshear'. strength properties under shearing stresses at relatively high pressures. When used in lubricants, it imparts excellent extreme pressure properties. Yet, there has been no indication from results obtained with such prior compositions that molybdenum disulfide could enhance a grease composition intended for lubrication of electric motor generators. It is: an object of this invention, therefore, to provide new compositions of matter. It is another object to provide new and improved, grease compositions. It is a particular object to provide greasecompositions capable of long, effective life in use as lubricants inelectric motor generators; Other objects and advantages of the present invention will become apparent to those skilled in the art from the following description.

The foregoing objects are realized with new grease compositions comprising alkaline earth metal complex greases containing from about one to about 65 percent, by weight, of molybdenum disulfide.

The term grease, as used herein, denotes a composition comprising a major proportion of lubricating oil thickened to a grease consistency with the salt-soap complexes described herein, such composition having an unworked penetration, when tested by ASTM Method D217-52T, of at most 475, using the modified cone recommended by ASTM Technical Committee G, of ASTM Committee D-2.

As indicated above, the complex greases described in US. Patent Nos. 2,197,263, 2,564,561 and 2,898,297 are representative of those which may be used to form the new grease compositions. Others include calcium-stearate-caprylate-acetate complexes described by Liddy in application Serial No. 67,499, filed November 7, 1960, now Patent No. 2,999,065, issued September 5, 1961; and

3,170,878 Patented Feb. 23, 1965 calcium caprylate-acetate described by Liddy in application Serial No. 78,842, filed December 28, 1960, now Patent No. 2,999,066, issued September 5, 1961. Still others are greases containing calcium salts and soaps of low-, intermediateand high-molecular weight acids and of nut oil acids, as described by Schott in application Serial No. 829,465, filed July 24, 1959, now abandoned. It is to be understood that all of the acids mentioned in the said applications and patents can be used herein. In this connection, a high molecular weight acid is one having 13 or more carbon atoms per molecule; an intermediate molecular weight acid is one having from about 7 to about 12 carbon atoms per molecule; and a low molecular weight acid has from'l to about 6 carbon atoms per molecule. Reference ismade to-said applications and patents for details in the method of preparation of the complex gelling agents and the relative balance of which include the use of calcium and mixtures of calcium and barium, as the alkaline earth metals, and the use of nut oil acids, as described in columns 2 and 3 thereof, in view of the exceptional results obtained therewith.

With respect to molybdenum disulfide used in the compositions of this invention, it has been found that the degree of comminution should be such that all of its parti cles have an effective diameter of less than 10 microns, and preferably 1essthan 2 microns.

The amount of molybdenum disulfide used herein can be from aboutl to about 65 percent, byweight, of the finished grease product. Preferred, however, are concentrations from about 3 to about 30 percent. V Molybdenum disulfide can be incorporated with the grease at almost any stage in the manufacture of the final product, dependent upon convenience with respect to the particular grease plant. For example, it can be incorporated when the complex salt-soap isformed, or more usually it can be incorporated at some stage in the handling of the semi-finished product. The important feature is that suflicient mixing should be utilized, by working, homogenizing, or otherwise, to secure a complete. and thorough dispersion of the particles of M08 throughout the grease.

An outstanding grease composition of this invention has been formedin the manner described in Example I *Coconut oil having the composition disclosed in the aforementioned U.S. Patent No. 2,898,297, column 3, lines 10-25.

4364 pounds of oil, and all of the other ingredients except the chlorinated sperm oil and the anti-oxidant, were heated in a Stratco Contactor up to a temperature of 345 F. over a period of minutes. This reacted material, a soap concentrate, was discharged into a jacketed, steam-heated, grease kettle of 2000 gallons capacity and was dehydrated at 300 320 F. for 3 hours. The material was then diluted with 3207 pounds of oil and cooled to 200 F. During this time the grease was homogenized in a Manton Gaulin machine at 3000 p.s.i. At 200 F., the chlorinated sperm oil and anti-oxidant were incorporated. The grease was cooled to 180 F. and filled from the homogenizer line at 3000 psi. This material designated as the blank grease had a worked penetration of 325 and a dropping point of 500+ F. 50 pounds of the blank grease were charged to a small gallon, steamheated grease kettle and warmed to 200 F. Thereafter, 1.5 pounds of molybdenum disulfide powder (technical, fine) were added to the grease and stirred for 15 minutes. This mixture was homogenized at 3000 psi. for about 2 passes and filled into a 35 pound container. The worked penetration of this material, designated Example I, was 320.

The grease product designated Example I was tested for high temperature performance in a motor-generator test set consisting of two squirrel-cage induction motors, Class H silicone insulated, with adjustable pitch diameter pulleys belted together so that one functions as a motor and the other as a generator. The temperature of the outer race of the test hearing was regulated at 300 F. by adjusting the load on the motor (i.e. adjusting the speed of the driven unit). A single shielded, steel retainer, deep groove, single row, Conrad type, number 310, ball hearing was used for the test bearing. This hearing was mounted on the end opposite the pulley and of the driving motor. I

The test bearing was packed with grams of the test grease, evenly distributed throughout the bearing. The end bell of the motor was packed with grams of grease. Failure of the grease was indicated by excessive bearing noise and stalling of the motor upon starting.

For comparative purposes, the corresponding grease free of molybdenum disulfide was subjected to the same test. It was found that the grease serving as a blank operated for only 191 hours, whereas, the MoS -containing grease operated for 283 hours. This is an improvement of 48 percent.

While the greases of this invention are particularly well adapted for use in lubricating equipment such as electric motor generators, they have a much wider range of industrial application. They can be used as multipurpose automotive greases including use in sealed-forlife ball joints; multi-purpose industrial greases serving as plain-bearing and anti-friction greases for normally loaded and heavily loaded equipment. Thus, greases of this invention range from types suitable as textile machinery lubricants, to solid block type greases used in lubrication of machinery in steel mills, paper mills, cement mills, etc.

It is to be understood that the greases of this invention can also contain other characterizing materials and fillers. In particular, it has been found that certain anti-oxidants enhance the storage and shelf stability of the grease com- 4 positions. Outstanding among such materials is 2-6-ditertiary butyl 4 methylphenol. Other such materials which may be used herein are: phenothiazine, diphenyl p-phenylene diamine, hexyl gallate, 4-tertiary butyl catechol, phenyl beta-naphthylamine, 2-4-dietertiary butyl pcresol, tritertiary amyl phenyl phosphite together with a small amount of dicyclohexyl amine, polymerized trimethyl di-hydroquinoline (Agerite resin of R. T. Vanderbilt Company), and mixtures of monoand diheptyl diphenylamines (Agerite Stalite of R. T. Vanderbilt Company).

I claim:

1. A grease consisting essentially of: a lubricating oil vehicle; a grease-forming quantity of a gelling agent comprising an alkyline earth metal salt-alkaline earth metal soap complex; and from about one to about sixtyfive percent, by weight, of molybdenum disulfide of such fineness that its particles have an effective diameter of less than ten microns, said complex being comprised of an alkaline earth metal salt of a low molecular weight aliphatic monocarboxylic acid having from one to six carbon atoms per molecule, an alkaline earth metal salt of an intermediate molecular weight aliphatic monocarboxylic acid having from seven to twelve carbon atoms per molecule and an alkaline earth metal soap of a high molecular weight aliphatic monocarboxylic acid having more than twelve carbon atoms per molecule.

2. A grease consisting essentially of: a lubricating oil vehicle; a grease-forming quantity of a gelling agent comprising an alkaline earth metal salt-alkaline earth metal soap complex; and from about one to about sixty-five percent, by weight, of molybdenum disulfide of such fincness that its particles have an effective diameter of less than ten microns, said complex being comprised of an alkaline earth metal salt of a low molecular weight aliphatic monocarboxylic acid having from one to six carbon atoms per molecule, an alkaline earth metal salt of an intermediate molecular weight aliphatic monocarboxylic acid having from seven to twelve carbon atoms per molecule, an alkaline earth metal soap of a high molecular weight aliphatic monocarboxylic acid having more than twelve carbon atoms per molecule, and alkaline earth metal soaps of coconut oil acids comprising mixtures of acids containing from about 8 to 18 carbon atoms per molecule and predominating in C C acids.

References Cited in the file of this patent UNITED STATES PATENTS 2,156,803 Cooper et a1 May 2, 1939 2,898,297 Schott Aug. 4, 1959 3,015,623 Loring et al Jan. 2, 1962 OTHER REFERENCES US. National Advisory Committee for Aeronautics, Technical Note 2180, by Godfrey et al., September 1950, 33 pages,

Claims (1)

1. A GREASE CONSISTING ESSENTIALLY OF: A LUBRICATING OIL VEHICLE; A GREASE-FORMING QUANTITY OF A GELLING AGENT COMPRISING AN ALKYLINE EARTH METAL SALT-ALKALINE EARTH METAL SOAP COMPLEX; AND FROM ABOUT ONE OF ABOUT SIXTYFIVE PERCENT, BY WEIGHT, OF MOLYBDENUM DISULFIDE OF SUCH FINENESS THAT ITS PARTICLES HAVE AN EFFECTIVE DIAMETER OF LESS THAN TEN MICRONS, SAID COMPLEX BEING COMPRISED OF AN ALKALINE EARTH METAL SALT OF A LOW MOLECULAR WEIGHT ALIPHATIC MONOCARBOXYLIC ACID HAVING FROM ONE TO SIX CARBON ATOMS PER MOLECULE, AN ALKALINE EARTH METAL SALT OF AN INTERMEDIATE MOLECULAR WEIGHT ALIPHATIC MONOCARBOXYLIC ACID HAVING FROM SEVEN TO TWELVE CARBON ATOMS PER MOLECULE AND AN ALKALINE EARTH METAL SOAP OF A HIGH MOLECULAR WEIGHT ALIPHATIC MONOCARBOXYLIC ACID HAVING MORE THAN TWELVE CARBON ATOMS PER MOLECULE.