US3639237A

US3639237A - Extreme pressure greases

Info

Publication number: US3639237A
Application number: US824675A
Authority: US
Inventors: George G Curtis
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1969-05-14
Filing date: 1969-05-14
Publication date: 1972-02-01
Anticipated expiration: 1989-02-01

Abstract

A lubricating grease having extreme pressure (e.p.) properties comprising a major amount of lubricating oil and minor amounts of colloidal asbestos, finely divided polymeric fluorocarbon powder having a melting point (m.p.) above 450* F. and a powdered inorganic grease thickener. The colloidal asbestos is characterized by its chrysolite configuration and by its separate distinct fibers. The polymeric fluorocarbon is selected from the group consisting of polytetrafluoroethylene and fluorinated ethylene propylene copolymer. The inorganic thickeners are selected from the group consisting of talc, graphite and Group I, II and IV metal oxides and carbonates.

Description

United States Patent Curtis 1 1 Feb. 1, i972 EXTREME PRESSURE GREASES 3,314,889 4/1967 Christian ..252/49.6

3,350,307 10/1967 Brown et 2.1.... [72] Inventor. George G. Curtis, Westfield, NJ. 3,424,678 1/1969 Morway et "252/13 [73] Assignee: Esso Research and Engineering Company 3,437,593 4/1969 Bellavin ..252/13 [22] Filed: May 1969 Primary Examiner-Daniel E. Wyman [2| App) 24 7 Assistant Examiner-J. Vaughn Attorney-Pearlman and Stahl [52] US. Cl ..252/13, 252/28, 252/29, [57 BST ACT 252/30, 252/58 51 Int. Cl. ..Cl0m 1/30, c 10m 1/10 A fl f hav'ng 9 Pmpeftles [58] Field of Search ..252/13, 28, 29, 30, 5s COmPflsmg a 19 amwm of fi, and amounts of colloidal asbestos, finely divided polymeric 56 R i d fluorocarbon powder having a melting point (m.p.) above 1 8 names I e 450 F. and a powdered inorganic grease thickener. The col- UNITED STATES PATENTS loidal asbestos is characterized by its chrysolite configuration I and by its separate distinct fibers. The polymeric fluorocarbon 2,836,560 5/1958 Teale et al. ..252,25 is selected from h group consisting of 23771182 3/1959 May "252/28 polytetrafluoroethylene and fluorinated ethylene propylene 2,890,170 6/1959 Ragborg ..252/28 copolymer. The inorganic thickeners are selected from the 3,0l 1,975 12/1961 Nitzsche et a1. ..252/28 group consisting f talc, graphite and Group I, [l and v meta] 3,159,577 12/1964 Ambrose et a1 ..252/28 Oxides and carbonates 3,248,326 4/1966 Swenson ..252/49.6 3,288,710 11/1966 Hollitz 1.25 2/25 10 Claims, No Drawings EXTREME PRESSURE GREASES BACKGROUND OF THE INVENTION 1. Field of the Invention This invention is directed to lubricating grease compositions containing a combination of colloidal asbestos, finely divided, polymeric fluorocarbon having a melting point above 450 C. and inorganic thickeners, which combination results in an extreme pressure grease. More particularly, it is directed to a lubricating grease composition containing lubricating oil, such as mineral oil, polyphenylether oils and polysilicone oils, etc., colloidal asbestos, finely divided, solid polymeric fluorocarbons, such as polytetrafluoroethylene, and fluorinated ethylene propylene copolymer powder having an average particle size ranging from submicron (e.g., 0.1 micron) to 100- micron size, and inorganic thickeners, such as talc, graphite, and Group I, II and IV metal oxides and carbonates.

2. Description of the Prior Art The use of natural asbestos as an ingredient in lubricating grease compositions is old in the art. A number of such grease formulations are taught in the book, Lubricating Grease by C. J. Boner, Second Edition, pages 687 et seq. These prior greases utilized conventional natural asbestos or asbestos floats, both of which are relatively long-fibered asbestos occurring in fibril bundles or agglomerates almost impossible to separate or deagglomerate. However, this prior art, fibered asbestos was always used in conjunction with other thickening agents, such as soaps, since the prior long-fibered asbestos fibrils or bundles (agglomerates) are too large and will not form a thickened, homogeneous stable grease gel by itself but, rather, rely upon other ingredients to form the grease or gellike structure. In addition, these prior asbestos greases were often abrasive due to the large asbestos fibers.

Recently issued patent U.S. Pat. No. 3,424,678 discloses the use of colloidal asbestos in greases. This colloidal asbestos differs from the long-fibered conventional asbestos in that the asbestos fibers are separate and distinct, occuring in a small colloidal size, having a large surface area, and can be dispersed in oil to form a gel by themselves without settling out from the oil.

The use of fluorocarbon polymers in grease compositions has been described in U.S. Pat. No. 3,011,975 and U.S. Pat. No. 3,248,236. Similarly, the use of inorganic thickeners has also been taught. (See, e.g., U.S. Pat. No. 2,599,353, Lubricating Greases, C. .l. Boner, pp. 677 etc., and Lubricating Greases, their Manufacture and Use, E. N. Klemgard, pp. 686 etc., [Reinhold 1937].) Thus, while colloidal asbestos, polymeric fluorocarbons and inorganic thickeners per se are known in the an, it has not heretofore been known that a mixture of three components exhibits an enhanced coaction in greases.

SUMMARY OF THE INVENTION It has now been found, in accordance with this invention, that by incorporating in a lubricating oil the combination of (l) colloidal asbestos, (2) finely divided polymeric fluorocarbon powder having an m.p. above 450 F., and (3) an inorganic thickener, an improvement in the e.p. properties of the resultant grease over that provided by the incorporation of any one or two of these three components is obtained. More specifically, it has now been discovered that a grease having exceptional and unexpected extreme pressure properties can be prepared by adding about 1 to about weight percent of a finely divided polymeric fluorocarbon powder selected from the group consisting of polytetrafluoroethylene and fluorinated ethylene propylene copolymer and about 1 to about 25 weight percent or an inorganic thickener selected from the group consisting of talc, graphite, Group I, II and IV metal oxides and carbonates, to a lubricating oil having about 1 to about 15 weight percent of colloidal asbestos as its primary thickener. It has further been found that, if the weight percent ratio of said inorganic thickener to the combined weight percent of the other two components is greater than 1:2, a further improvement in e.p. properties is achieved. Thus, it is especially preferred that the ratio of weight percent of said inorganic thickener to the combined weight percent of the other two components, ranges from about 0.5:] to about 3:1, and most preferred is a ratio of about 0.75:1 to about 1.25: l.

The colloidal asbestos of the present invention is chrysolite having the chemical formulation: Mg (0l-I) Si 0 The usual mode of occurrence of chrysolite is a cross-fiber" configuration in which agglomerates of chrysdlite (i.e., bundles of fibers) are closely packed together and set at right angles to the walls of cracks and fissures that extend through the host rock of the ore body. However, in 1959, an unusual deposit of chrysolite asbestos, with properties and a mode of occurrence different from the previously known cross-fiber material was discovered in central California. The ore of this new deposit, instead of occurring in veins, occurs in randomly oriented, mattelike flakes of relatively deagglomerized, visible asbestos filaments which, in turn, are made up of many thousands of extremely small tubular fibers. The lengths of these small fibers vary from a few millimicrons to thousands of mil- PROPERTIES OF COLLOIDAL ASBESTOS FIBERS Brightness (GE) Refractive index Dispersion in water Surface area Oil absorption Water retention Dry bulk density Fiber dimension Fully/pH range 4-6 47-50 sq. meters/gram 14-] 6 cc./l0 grams offiibers 42 grams/20 grams of fibers 2-2.5 lbs./cu.ft.

Outer diameter 25.0 m Inner diameter 6.0 mg. Length 2500-25,000 ma Any polymeric fully fluorinated fluorocarbon powder can be used in this invention provided it is characterized by a high melting point, i.e., above 450 F., and consists of finely divided particles whose average size ranges from submicron (e.g., 0.1 to IOU-micron size, Preferably, these particles will have an average particle size of about 5 to about 25 microns. Preferred are the polymeric fluorocarbons selected from the group con sisting of polytetrafluoroethylene and fluorinated ethylene propylene (FEP) copolymer. The polymer fluorocarbon compounds operable in this invention can be prepared by methods well known in the art, (See, e.g., U.S. Pat. Nos. 2,833,686; 2,946,763; 3,011,415 and 3,248,326.) or can be purchased as readily available commercial commodities under such trade names as TFE Teflon and dFEP Teflon. The polytetrafluoroethylene is a polymer of a fully fluorinated hydrocarbon of the basic chemical formula CF CF containing 71 percent by weight of fluorine and having a melting point above 600 F. The fluorinate-d ethylene propylene copolymer is a fully fluorinated resin prepared by polymerization of tetrafluoroethylene and hexafluoropropylene to form a copolymer containing about 5 to about 50 weight percent hexafluoropropylene and about to about 50 weight percent tetrafluoroethylene. These copolymers have melting points ranging from about 480 F. to about 560 F. Especially preferred for use in this invention is polytetrafluoroethylene.

The inorganic grease thickeners contemplated for use in the combination of this invention are those known in the art which do not, in their normally available particle size, form thick, homogeneous grease gels by themselves: and which rely upon other ingredients to fonn the gellike structure. Among these are talc, graphite, and Group I, II and IV metal oxides such as zinc, titanium and magnesium oxides, and carbonates, such as calcium carbonate, sodium carbonate, e.g., Na CO Na CO-r H O, zinc carbonate, e.g., ZnCO ZnCO -H O, and magnesium carbonate etc. Among these inorganic secondary thickeners, talc and zinc oxide are preferred and tale is most preferred.

While the ratios of the colloidal asbestos, the polymer fluorocarbon and the inorganic thickener of this invention can vary in relation to each other, it is understood that an oilthickening, grease-forming amount will be used. Thus, the

The lubricating oil used in the composition of the invention 5 combined amount of colloidal asbestos and inorganic may be either a mineral lubricating oil or a synthetic lubricatthickener will range from about 5 to about 40 weight percent, ing oil. Synthetic lubricating oils which may be used include preferably 6 to 30 weight percent, of the total composition polyphenyl ether oils, polysilicone oils, esters of dibasic acids and the polymeric fluorocarbon powder will form a minor (e.g., di-Z-ethylhexyl sebacate), esters ofglycols (e.g., C OX0 amount, usually about 1.0 to about 15 weight percent, acid diester of tetraethylene glycol, etc.), complex esters (e.g., 10 preferably 2 to 10 weight percent, of the total composition. the complex ester formed by reacting 1 mole of sebacic acid Generally, the colloidal asbestos forms about 1.0 to about with 2 moles of tetraethylene glycol and 2 moles of 2-ethyl weight percent, preferably about 3 to about l0 weight percent hexanoic acid,phosphoric acid, (e.g.,the ester formed by conof the total composition, and the inorganic thickeners from tacting 3 moles of the monomethyl ether of ethylene glycol about i to about 25 weight percent, preferably about to with 1 mole of phosphorus oxychloride, etc.) halocarbon oils 15 about 2 eigh P Ofthe total mposi i (e.g., the polymer of chlorotrifluoroethylene containing l2 Various other additives may also be added to the lubricating recurring units of chlorotrifluoroethylene), alkyl silicates composition in amounts of 0.1 to 10.0 weight percent each. (e.g., methyl polysiloxanes, ethyl polysiloxanes, methyl phenyl Such additives include lubricating oil sludge detergents and polysiloxanes, ethyl phenyl polysiloxanes, etc.), sulfite esters dispersants, oxidation inhibitors such as phenyl-alpha- (e.g., ester formed by reacting -1 mole of sulfur oxychloride naphthylamin C rr si n i hi C as rbitan with 2 moles of the methyl ether of ethylene glycol, etc.), carmon lea e and di m ni i y h r gr e hick ners. bonates (e.g., the carbonate formed by reacting C Oxo aland the like:

cohol with ethyl carbonate to form a half ester and reacting The lubheahhg grease of Preseht Invention can be this half ester with tetraethylene glycol), mercaptan with for- P ep y methods known the For p the maldehyde, formals (e.g., the formal formed by reacting C loldal asbestos, the Polymeric h e l' i the inorganic Oxo alcohol with formaldehyde), polyglycol-type synthetic thickener and a P of the lubl'leahhg ell be lfsed h" be oils (e.g., the compounds formed by condensing butyl alcohol P atelevated p h e below the melhhg P of with 14 units of propylene Oxide em) or mixtures of any of the polymeric fluorocarbon, |.e., in the range of about 250 to the above in any proportions 450 F., when free water and water of crystallization is felt to Preferred synthetic lubricating oils are the polyphenyl ether be ahove the dashed level orfier to drive e substantially all oils and the polysilicone oils, when the lubricant is designed of Sam :Vateh e can h P at emblem temperatures, for high temperature use since they are particularly stable at 77 h h Oil f Wet the ether hp high temperature. The polyphenyl ether oils are those no clent lubricating Oil to obtain the desired consistency can then mally liquid (at 77 F.) ethers represented by the general forbe added and the ehhre h h the mum: homogeneous product 15 obtained. This product can then be milled to optimum smoothness by passage through a mill apparatus. Alternatively, the grease can just as readily be made 0 0 by charging all of the components at essentially the same time to a Hobart mixer and then milling. h The nature of this invention will be further understood wherein n is about 2 to 6. The oxygen atoms attached to the when reference to the following examples which hydrocarbon rings intermediate the terminal phenyl groups, prefhhled emhhdhhehtsr whch are not to be construed can be in an ortho, meta, or para position relative to each asahlmtahoh oh thelhvehhoh other. isomeric mixtures of polyphenyl ethers within the Senes of grhases prepare: by the h h above formula are also included as well as mixtures of a Hobart mixer h h to for 5 minutes while polyphenyl ether molecules having different values for n. An and theri i mmmg to a umform homogeneolis product oil of the above general formula wherein n was about 3, ob- T composmons 9 the cases prepare? tained from Monsanto Chemical Co. under the designation, 2; and load'carrymg ablhty are Summarized m the following High Temperature Functional Fluid and Lubricant OS-l24, a

TABLE I Properties Composition (grams) ASTMD-217 Poly Phenylpenetration Polytetraalpha- (mm./100) 4-ball E.P. phenyl- Colloidal fiuoro- Zinc naphthyi- 77 F.,60 1,800 r.p.m. ether asbestos ethylene Tale 2 oxide amine strokes (kg. weld) Example 1 398 24. 5 3 24. 5 4 316 447 Comparative Grease A. 398 24. 5 4 316 158 Examp 2 600 30 30 6.4 315 316 Comparative Grease B. 600 30 6.4 315 158 Examp 3 750 40 4 37. 5 0 312 398 Comparative Grease O... 750 40 9 312 168 Comparative Grease D.-- 1,000 10.6 309 158 Comparative Grease E-.. 1,000 60 5 50 10.6 309 251 Comparative Grease F 820 12.5 326 251 Comparative Grease G 820 5 12.5 326 251 other specific examples of these polyphenyl ethers include:

l. An oil represented by the general formula:

L L, Ur

where n is 3, obtained from Monsanto Chemical Co. under the designation, High Temperature Functional Fluid and Lubricant 08-124."

2. Powdered talc obtained from Baker & Adams Co. and

described as meeting USP standards.

3. DuPont TFE Teflon 7A having an average particle size of microns, a specific gravity within the range of 2.12-2.14 (ASTM D-742) and an apparent bulk density of 470 g./l. (ASTM D-l457-62T).

4. Liquid Nitrogen Processing Co.s TL-l26 having an average particle size of about 5-10 microns, a specific gravity of about 2.16 and a softening point of 6 1 2 F.

5. Liquid Nitrogen Processing Co.s TL-l l5 having an average particle size of 8-10 microns and a specific gravity within the range of2. 16-2. 1 8.

The Shell 4-ball e.p. test is used to evaluate the e.p. characteristic of a grease. In this test three steel balls in a pot are locked in contact with one another on a horizontal base. A fourth ball is held on top in a vertical chuck which rotates at I800 rpm. The points of contact are lubricated by the test grease. Initially, a 40-kilogram load applied to a lever arm presses the three stationary balls upward against the rotating ball. The machine is run at room temperature, e.g., 77 F., and increasing pressure is applied to the balls rotating in the machine until seizure is felt and finally until the balls weld. The higher the seize and weld values, the better the extreme pressure properties of the grease. A series of l0-second runs was made at preselected, successively higher loads until weld ing of the four balls occurred. The loads used were 40 kg., 50 kg., 63 kg., 79 kg., 100 kg, 126 kg, 158 kg, 200 kg., kg, 316 kg, 398 kg., and 447 kg. A fresh grease sample and new steel balls were used with each load.

As can be seen from comparing the greases formed in examples l, 2 and 3, which represent the invention, with those of comparative greases A, B and C, the greases containing a combination of the three components of this invention exhibit unexpectedly superior e.p. properties over those greases having the same consistency in which the polytetrafluoroethylene was not present.

Comparative Greases D through G serve to demonstrate that the observed synergistic effect was a result of the combination of the three components of this invention and was not the result of the combination of polytetrafluoroethylene with only one of the other two components or the result of merely additive e.p. properties. As can be seen by comparing grease G with grease F, polytetrafluoroethylene does not increase the ep. properties of the product containing only talc and oil. Furthermore, a comparison of grease D with greases A and B shows that talc does not increase the e.p. properties of a grease containing only colloidal asbestos and oil.

Thus, while a comparison of greases D and E shows that polytetrafluoroethylene does increase the e.p. properties of a grease containing colloidal asbestos and oil, this, in view of the data on polytetrafluoroethylene, talc and oil, is far from suggesting that a combination of the three components of this invention would exhibit the clearly synergistic effect seen in examples 2, 3 and especially 1 oftable 1.

EXAMPLE 4 Extreme pressure greases are also obtained when LII fluorinated ethylene propylene copolymer(Liquid Nitrogen Processing Co.s TL-120 FEP, having an average particle size of 0.7 micron, a specific gravity within the range of 2. 16-2. 1 8

and a melting point of about 540 F.) is substituted for the polytetrafluoroethylene of examples 1,. 2 and 3. When making these greases the components are heated to 400" F. for 5 minutes and then roll milled to a homogeneous product.

In light of the extreme pressure properties exhibited by the grease compositions of this invention, these greases are especially useful in the lubrication of relatively moving parts (e.g., gears, bearings, etc.) which are subject to high pressures in their operation.

While particular embodiments of this invention are shown in the examples, it will be understood that the invention is obviously subject to the variations and modifications disclosed above without departing from its broader aspects and, therefore, it is not intended that the invention be limited to the specific modifications which have been given above for the sake of illustration, but only by the appended claims.

What is claimed is:

l. A lubricating grease composition comprising:

a. a major amount of lubricating oil;

b. about 1 to about 15 weight percent of colloidal asbestos, characterized as having naturally occurring fibers with a particle outer diameter of about I to millimicrons and a particle length of about 2,000 to 30,000 millimicrons;

c. about I to about 15 weight percent of a finely divided polymeric fluorocarbon powder having an average parti cle size ranging from submicron to l00-micron size and having a melting point above 450 F.; and

d. about l to about 25 weight percent of an inorganic grease thickener selected from the group consisting of talc and zinc oxide;

said weight percents being based on the total composition, the combined amount of components (b) and ((1) representing about 5 to about 40 weight percent of the total composition.

2. The lubricating composition of claim 1 wherein said polymeric fluorocarbon powder is selected from the group consisting of polytetrafluoroethylene and copolymer of tetrafluoroethylene and hexafluoropropylene.

3. A lubricating composition as in claim ll wherein the inorganic thickener is zinc oxide.

4. A lubricating composition as in claim 1 wherein the inor ganic thickener is talc.

5. A lubricating composition as in claim ll wherein the combined amount of colloidal asbestos and inorganic thickener represents about 6 to about 30 weight percent of the total composition.

6. A lubricating composition as in claim ll wherein the finel divided polymeric fluorocarbon powder polytetrafluoroethylene.

7. A lubricating composition as in claim l wherein the finely divided polymeric fluorocarbon powder is characterized as having an average particle size ranging from about 5 to about 25 microns.

8. A lubricating composition as in claim 1 wherein the ratio of component ((1) to the combined weight percent of components (b) and (c) ranges from about 0.5:] to about 3: l.

9. A lubricating composition as in claim 1 wherein the colloidal asbestos forms about 3 to about 10 weight percent of the total lubricating grease composition, the finely divided polymeric fluorocarbon powder forms about 2 to about 10 weight percent of the total composition and the inorganic thickener forms about 3 to 20 weight percent of the total com position.

110. A method of improving the lubrication of relatively moving parts which comprises applying to said parts the grease composition defined by claim ll.

Claims

2. The lubricating composition of claim 1 wherein said polymeric fluorocarbon powder is selected from the group consisting of polytetrafluoroethylene and copolymer of tetrafluoroethylene and hexafluoropropylene.
3. A lubricating composition as in claim 1 wherein the inorganic thickener is zinc oxide.
4. A lubricating composition as in claim 1 wherein the inorganic thickener is talc.
5. A lubricating composition as in claim 1 wherein the combined amount of colloidal asbestos and inorganic thickener represents about 6 to about 30 weight percent of the total composition.
6. A lubricating composition as in claim 1 wherein the finely divided polymeric fluorocarbon powder is polytetrafluoroethylene.
7. A lubricating composition as in claim 1 wherein the finely divided polymeric fluorocarbon powder is characterized as having an average particle size ranging from about 5 to about 25 microns.
8. A lubricating composition as in claim 1 wherein the ratio of component (d) to the combined weight percent of components (b) and (c) ranges from about 0.5:1 to about 3:1.
9. A lubricating composition as in claim 1 wherein the colloidal asbestos forms about 3 to about 10 weight percent of the total lubricating grease composition, the finely divided polymeric fluorocarbon powder forms about 2 to about 10 weight percent of the total composition and the inorganic thickener forms about 3 to 20 weight percent of the total composition.
10. A method of improving the lubrication of relatively moving parts which comprises applying to said parts the grease composition defined by claim 1.