US 3248326 A
Description (OCR text may contain errors)
' torily withstanding severe operating conditions.
United States Patent Ofifice 3,248,326 LUBRICANT GREASE Reuben A. Swenson, Whiting, Ind., assignor to Standard Oil Company, Chicago, 11]., a corporation of Indiana No Drawing. Filed June 3, 1963, Ser. No. 284,832 3 Claims. (Cl. 252-49.6)
The present invention relates to novel lubricant greases and more particularly to novel greases wherein oleaginous materials are thickened to grease consistency with fluorocarbon resins.
Various types of greases have long been used in the lubrication of anti-friction bearings such as ball or roller bearings. These greases must provide a low torque and low temperature rise in the bearing and they should have long high temperature lubrication life so that frequent repacking of bearings is unnecessary.
In the past the so-called complex and soap type greases have been generally accepted as satisfactory for most applications. Soap greases are thickened with a soaptype grease thickener which contains an alkali or alkaline earth metal soap of a high molecular weight soap-forming carboxylic acid and/or petroleum sulfonic acid.
Technology has advanced rapidly in the past few years with the development of machines, engines, etc., which operate at higher speeds and higher temperatures than their forerunners. Consequently, a need has arisen for greases capable of withstanding these more severe conditions of operation. To meet this need, soap thickened greases have been improved in many respects and have been found quite useful in many high-speed, high-temperature operations.
In addition, other thickening agents have been developed in an attempt to find a grease capable of satisfac- One of these thickening agents is a polymerized tetrafluoroethylene. Greases thickened with this polymeric material have been prepared and evaluated under various conditions of operation. In several instances such greases were found to be satisfactory and even advantageous in comparison with certain soap greases known to the prior art. However, it was observed that greases thickened with polymerized tetrafluoroethylene lost their consistency andbroke down to an undesirable extent when used in applications requiring high speed and consequently high temperature machine and engine operation.
According to the present invention, it has now been unexpectedly found that a particularly advantageous grease results when an oleaginous vehicle is thickened to grease consistency with a resinous material which is the product of copolymerizing tetrafluoroethylene and hexafluoropropylene. Such a grease composition possesses unique properties making it particularly adaptable for high speed application at elevated temperatures up to 450 F. and higher. Unexpectedly greases of the present invention thickened with a fluoroethylenepropylene resin possess excellent wear, extreme pressure, and high temperature properties and retain their consistency for long periods of operation in contrast to the relatively poorer performance given by the chemically similar tetrafluoroethylene resin thickened greases. Fluoroethylenepropylene resin thickeners have been observed according to the present invention to impart superior properties to a variety of oleaginous vehicles including the hydrocarbon oils, ester oils, and silicone oils such as fluorosilicone oil.
3,248,326 Patented Apr. 26, 1966 The fluoroethylenepropylene resin thickeners of the present invention are prepared by polymerization of tetrafluoroethylene with hexafluoropropylene to form a copolymer having the following repeating unit:
Typically, these fluoroethylenepropylene resin thickeners are in a finely divided white powder form with a particle size on the order of to microns. Other characteristic properties of these materials have the following values.
Table 1 Melting point 545565 F. Specific heat .28 cal./g./ C.
At 475,1 134412003. 1 1.388. Hardness Rockwell (ASTM 785-51T) R25. Water absorption (ASTM D570) .01%.
Fluoroethylenepropylene resins such as these are avail able commercially and have been marketed under the trademark Teflon 120 FEP fluorocarbon resin. These materials are further processed for use in this invention by drying, heat treating and grinding.
The resin will be used in particular applications in an amount sufficient to thicken the oleaginous vehicle to the desired consistency and impart the desired characteristics to the resulting grease. This amount will vary with the requirements of the particular application for which a grease of the present invention is being formulated. Typically, however, a grease of the present invention. will contain fluoroethylenepropylene resin thickener in an amount from about 20 to about 60 percent by weight of the total grease composition. In particular applications it may be advantageous to employ the thickener in an amount from about 25 to about 50 percent by weight, and in preferred formulations the thickener will be present in an amount from about 25 to about percent by weight.
The thickeners of the present invention may be employed in conjunction with a wide variety of oleaginous lubricant vehicles. All typesof mineral lubricating oils as well as synthetic oils including diesters, complex esters, hydrocarbon polymers, and silicone oils having lubricating oil characteristics, may be used. Specific oils which may advantageously be employed as the vehicle in grease formulations of the present invention include hydrocarbon base oils such as solvent extracted SAE 40 Oil and unextracted SAE Oil. In addition, ester oils, such as that marketed commercially under the name Her- 5 colube A and silicone polymer oils, may be used. The
preferred silicone oil is a fluorosilicone oil having the following characteristics:
3 4 Table 2 significant advantage over that of the tetrafluoroethylene resin thickened grease of column 2. The aforemenviscosiiygmde tioned grease formulations were compared with a conventional lithium soap grease having the concentrations 300 cs 1,000 Cs 5 and exhibiting the properties set forth in column 6. It will be seen that the percent of leakage is reduced in Color Watcrwhi e to straw each of the fluoroethylenepropylene resin thickened g fi" cemiswkes greases by a factor of at least 2 in comparison with the i 0,500 22, 000 77 F-.. 300 1,000 lithium soap grease. The fluoroethylenepropylene thick- 25% g g 10 ened greases .are clearly superior to the lithium soap Specific ilv y a 1. '25 1'28 greases in the other significant categories, as will be seen figgfgggagfrom a comparison of the data in column 2 with the data Fire p 0 inl; sour 620E in column 6. iiiggggi ggg g 20 L5 In higher temperature applications, the advantage of 120 hours at 392: '1 18.0 5.0 employing greases thickened with fiuoroethylenepropylg g?% ;1- &8 3' 8 ene resins in comparison with greases thickened with T t ieg tetrafluoroethylene resins becomes even more apparent. Table 4 shows the results of high temperature (450 F.) operation for extended periods in the L-35 Bearing Persili polymer il f hi type can b b i d formance Test with greases thickened with fiuoroethylenemercially from Dow Corning Corporation as FS 1265 P py fluid. Grease formulations according to the present in- Table 4 vention may be prepared according to methods known in the art such as by colloid milling, roll milling, etc. v
To emphasize the advantage to be obtained through giififii iiirlf afi 3323;111:1333: $8 use of greases prepared according to the present inven- 3?; 1,230+ 1,120+ tron to COHIQIH- fluoroethylenepropylene ('FEP resin) resin thickeners, these materials were compared with at Coming Company DC 510 Silicone fluid. similar grease thickened with tetrafluoroethylene resin n (TFE resin). Results of that comparison are shown in 00 Both grease formulations were still performing satisfaccolumns 1 and 2 of Table 3. It will readily be seen after more than 1000 hours of Operation when from comparison of results set forth therein that the the test runs were Voluntarily pp Y y Of grease thickened with flu thyl r l resin is trast, satisfactory tetrafluoroethylene thickened greases equivalent to the tetrafluoroethylene resin thickened for Operation at these higher tempfl'amfes Could not be grease in all other tests and out performs the tetrafiuoroformulated- Attempts P p gfaase formulations ethylene resin thickened grease a factor greatc than using the latter mentioned fhlCkCl'lCIS in conjunction With 10 in the leakage test. This difference in percent leakvehicles of the yp reported herein ffliled- Formulaage i hi hl important because l k i an i ll tions attempted balled-up, lost their consistency and were significant measure of the all-important property of 40 found to be ullsatisfactory- Accordingly, 110 K1511 grease stability. The lower the leakage value, the greater runs W r mad Wi h tetrafluoroethylene thickened the amount of grease retained within the bearing, the greasesmore uniformly the thickener is dispersed throughout The L-35 Test is Coordinating Research Council Test the vehicle, the greater the stability of the grease and CRCL3559 developed and published by the Coordinatthus the higher is its efiiciency. ing Research Council, 30 Rockefeller Plaza, New York That the fluoroethylenepropylene resin thickeners are 20, New York. versatile and can be adapted for use in conjunction with Having thus described the invention, what is claimed is: various oleaginous vehicles can be seen from columns 3, 1. A grease-type lubricant composition consisting essen- 4 and 5 of Table 3. tially of an oleaginous lubricant vehicle selected from Table 3 FEP rcsin,wt.perccnt 30 43 43 4O 'IFE resin, wt. percent 30 Lithium soap, wt. percent. 7 Fluorosiliconc oil, wt. percent 37 "HERCOLUBE A ester oil, wt. percent... 57
Solvent extracted SAE 40 base oil, \vt. percent Unextracted SAE base oil, wt. percent Penetration at 77 F. ASTM D217-60T Leakage at 210 F., percent 1 4 Ball \vcar test scar diam., MM 4 Ball extreme pressure test weld pt., KGS
1 Federal test method-standard 791 method no. 321.
When the fluorosilicone oil, the ester oil and the solvent extracted SAE-40 Oil were used in conjunction with the fluoroethylenepropylene resin thickener, the penetration remained at a sufficien-tly high level while leakage was kept well Within the range established by the data in column 1, and in one case, that of the fiuorosilicone oil, there was no leakage whatsoever. Each of these specific the group consisting of a hydrocarbon oil, a silicone O lubricating oil and a synthetic ester lubricating oil and from about 20 to about 60 percent by weight of co- I polymer of tetrafluoroethylene and hexafluoropropylene said copolymer having a melting point from about 545 to 565 F., a specific heat of .28 cal./g./ C., a refracformulations, therefore, demonstrates a surprising and tive index at 475 of about 1.344, a Rockwell hardness of R25 and a water absorption of .01%, and said (10- 3. A grease-type lubricant composition as described polymer having the following repeating unit: in claim 1 in which the lubricant vehicle is a silicone oil.
References Cited by the Examiner UNITED STATES PATENTS 3,011,975 12/1961 Nitzsche et a1. 252-58 XR FOREIGN PATENTS a m mm mm m mm r m 5 M w 1 H 52B 41 N 6 2. A grease-type lubricant composition as described in claim 1 in which the lubricant vehicle is a hydrocarbon lubricating oil.