US2710839A - Aryl-urea thickened greases - Google Patents

Description

United States Patent 2,710,839 ARYL-UREA THICKENED GREASES Edward A. Swakon, Hammond, and Cecil G. Brannen, Munster, Ind., assignors to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Application November 1, 1952, Serial No. 318,321

14 Claims. (Cl. 25249.6)

The present invention relates to novel lubricant greases and to the method of preparing same. More particularly, it relates to novel greases comprising a lubricant vehicle thickened with certain high melting aromatic ureido and amido compounds. Greases of this type, particularly those wherein the lubricant vehicle comprises a silicone polymer oil, have demonstrated exceptional stability and lubricity at elevated temperatures.

As lubricants are required to perform at higher and higher temperatures because of increased speeds of engines and machines, the advent of jet propulsion, atomic energy as a source of power, etc., it has become increasingly diflicult to prepare greases fulfilling the require ments of such lubricants. In attempting to provide such greases, the art has progressed from the use of petroleum lubricant vehicles thickened with metal soaps of long chain fatty acids, e. g. lithium hydroxystearate, to more thermally stable synthetic lubricating oils such as the aliphatic diesters of dicarboxylic acids, silicone polymers, etc., thickened with such soaps or inorganic materials such as silica gels. The progress of thickener research has not in general, however, kept pace with the development of lubricant vehicles. And at temperatures as high as 400 to 450 F. there are few if any greases available which will retain their consistency and lubricity for any substantial period of time.

In recent years various synthetic lubricant vehicles, e. g. the silicones, fiuorocarbons, etc., have been found to be potentially valuable for use in greases employed at very high temperatures because of their thermal stability and relatively low volatility. Unless, however, a thickener having substantially the same degree of thermal stability is available to produce a grease fromssuch an oil, they are of little use. It has now been found'that certain very high melting aromatic urea s,:,di-.ureas,.amides, and di-amides, all of which contain at least one o RNHil radical, wherein R isan aryl radical, and which may hereinafter be referred to broadly as arylcarbamyl compounds, may be employed to thicken silicone polymer oils, as well as other known lubricant vehicles, to produce greases which are stable and display excellent lubricant propertiesat high temperatures. Whereas silicone polymer oils are particularly preferred for use in greases employed at temperatures as high as about 450 F, other lubricant vehicles, either natural or synthetic, may also be thickened with these materials to produce greases of particular utility between about 250 F. and

about 400 It. is aprirnary object of therpresent invention to provide lubricant greases which-are stable: and give excellent lubrication at elevated temperatures. A further object is to provide a readilyjproducible series:of:;greases embodying a novel class of thickening agents capable of yielding lubricants particularly suitable for use at temperaturesbffrom -about'250 "'F. to about 450 F. A

particular object of the present invention is to provide greases which are effective lubricants at temperatures as high as about 450 F. for substantial periods of time. These and additional objects will be apparent from the following detailed description.

We have found that lubricating vehicles such as silicone polymer oils, mineral lubricating oils derived from petroleum, synthetic lubricating oils such as polyalkylene glycols and their derivatives, high molecular weight esters of dicarboxylic acids, etc. and preferably the silicone polymer oils may be thickened to grease consistency by the addition thereto of from 5 to 70% and preferably from about 10 to about 50% of an arylcarbamyl compound selected from the group consisting of aromatic ureas, di-ureas, amides, and di-amides. Thus, in accordance herewith, arylcarbamyl compounds having the following empirical structure are contemplated as thickening agents in the art of grease manufacture:

O a minmen In .the above formulae, R, R and R" represent aryl or alkyl aryl radicals. With the exception that R" is necessarily a divalent radical, e. g. phenylene, biphenylene, naphthylene, etc., these radicals may be the same ordifferent, e. g. phenyl, biphenyl, naphthyl, etc. in each com pound. The aryl .or alkyl aryl radicals may be substituted radicals containing various reactive ,substituents such as hydroxy, carboxy, halo, nitro-, etc.

Examples of amides and di-amides which have been foundto yield excellent greases when employed as thickeners are N-benzoyl-4-aminobiphenyl, N,N'dibenzoylbenzidine, N,N'-dibenzoyl-p-phenylenefdiamine and N,N- bis-(p-nitrobenzoyl)-benzidine. Such compounds may 'be readily prepared by techniques well known to the art, e. g. by reaction of an aromatic amine or diamine such as phenylene-diamine, aniline, benzidine, etc., with an aroyl-halide, e. g. benzoyl chloride. 'Diamides such as may be prepared by reacting an aromatic monoamine, e. g. aniline, with an aroyl halide such as a phthalyl chloride, may likewise be employed in accordance herewith. These compounds maybe employedlalone or-in combination to thicken oleaginous vehicles to grease consistency,

'Examples of various ureas and di-ureas which have been found ,useful as thickeners in accordance herewith :are p-carboxyalfl-diphenylurea; CPrChl rmLB-diphenyI- urea; 1,3-di-(.l-naphthyl)-urea; 4,4-bis-[3-(p-biphenylyl)- llreido] -biphenyl; 1- (p-carboxyphenyl) -3- (p-biphenylyl an amine or diaminesuchas aniline; benzidine phenylenediamine, etc. with an isocyanate of benzene, diphenyl, etc. It should be understood that the specific aryl carbamyl compounds set forth above are enumerated for purposes of illustration and not of limitation. Compounds of this class may be employed alone or in combination with other such compounds to thicken oleaginous vehicles in accordance herewith.

Greases prepared with thickeners of the type described above, particularly those prepared from silicone oil, are exceptionally stable at elevated temperatures with those prepared from ureido compounds being slightly superior to those prepared from amide type thickeners.

The silicone polymer oils which may be employed in accordance with the present invention are those falling substantially within the lubricating oil viscosity range. In general, such oils have the following unit structure:

wherein R and R represent substituted or unsubstituted alkyl, aryl, alkylaryl, arylalkyl or cycloalkyl radicals.

Such compounds may be produced by well-known meth ods, e. g. the hydrolysis of dialkyldichlorosilanes or dialkyldiethoxysilanes with a suitable chain stopper, e. g. a trisubstituted mono-chlorosilane. For purposes of the present invention, those polymers which are high boiling liquids within the lubricating oil viscosity range are suitable, these generally possessing a viscosity at 100 P. which is within the range of from about 25 to about 3500 S. S. U. It is preferred, for purposes hereof, to employ such oils as have a viscosity at 100 F. of from about 300 S. S. U. to about 1250 S. S. U. Such products are generally colorless and inert, have a very low volatility and undergo relatively slight change in viscosity for a given change in temperature. Relatively common oils of this type are dimethylsilicone polymer, phenylmethylsilicone polymer, chlorophenylmethylsilicone polymer, etc., it being preferred to employ the phenylmethylsilicone polymer in accordance herewith. Methods of preparing such compounds are taught in numerous patents, e. g. U. S. 2,410,346, U. S. 2,456,496, and in the literature such as Chemistry of the Silicones by Rochow, page 61, et seq. A particularly desirable phenylmethylsilicone polymer for use in accordance with the present invention is Dow-Corning 550 silicone fluid, a product of Dow-Corning, Inc., which has a viscosity at 100 F. of about 300 to about 400 S. S. U.

Other oleaginous vehicles which may be employed herewith are, for example, mineral oils in the lubricating oil viscosity range, i. e. from about S. S. U. at F.- to about 300 S. S. U. at 210 F. These mineral oils are preferably solvent extracted, to substantially remove the low V. I. constituents, e. g. aromatics, with phenol, fur-- fural, B,B'-dichlorodiethylether (Chlorex), liquid S02, nitrobenzene, etc. Synthetic lubricating oils resulting from polymerization of unsaturated hydrocarbons or other oleaginous materials within the lubricating oil viscosity range such as high molecular weight polyoxyalkylene compounds such as polyalkylene glycols and esters thereof, aliphatic diesters of dicarboxylic acids such as the butyl, hexyl, 2-ethylhexyl, decyl, lauryl, etc. esters of sebacic acid, adipic acid, azeleic acid, etc., may be thickened by the aryl carbamyl compounds of the present invention to produce excellent greases. Polyfluoro derivatives of organic compounds, particularly hydrocarbons, in the lubricating oil viscosity range have shown excellent promise when thickened with compounds of the present invention.

Greases cf the present invention may be produced by one of the following methods:

(1) The thickener may be prepared apart from and then admixed with the lubricant vehicle and milled in a colloid mill, 3-rol1 mill, etc.

(2) The thickener may be formed in situ in the oil by introducing the reactants and the desired amount of lubricant vehicle, heating to about 450 F. for a relatively short time, c. g. from about five minutes to an hour to drive oif volatile by-products, and then cooling and milling the mixture.

(3) As a slight modification of method 2 above, a solvent such as dioxane may be employed as a diluent and mutual solvent for the reactants. The solvent is thenv evaporated and the grease is milled, etc. substantially as set forth.

(4) As a step in any of the above three methods, it has been found, when employing a silicone vehicle, that improved properties may be imparted to the grease by heat-treating the grease mixture, i. e. subjecting same to a temperature of about 450 F. for at least about half an hour and preferably longer, e. g. from about 1 to 20 hours. Prolonged heating at such temperature may evaporate a portion of the lubricant vehicle; this loss should be replaced and then the mixture should be milled. If desired, the heating and readdition of vehicle may be repeated before milling.

Table 1 Hours Be- Thickener Class g gfi Egg-s ggg i g Remarks 0 N-Benzoyl-p-aminobenzoic acid RtiiNHR' 33 (3) (4) 337 #1 o; #2 grade grease of excellent tex- 0 0 e. N,N-Dibe zoy1benz1d1 e RtiNHR'NHii R 26 188 2 33; fl sgg i g g e a sm g gg 4,4',b1s(3-b1pheny1ylureldo)-bipheny1 RN'H N'HW'NHi'JNHR 20 (3) (4) 437 Ggc id appearing #2 grade grease- O o ghly stable. D0 RNH( JNHR"N'HglNHR 18 (3) (4) 448 DO.

0 0 4,4 b1s[3 (2,5 diehloropheny1-)ureido1bt- RNH NH R"NHgNHR 25 (3) 435 smooth uttery 0r #2 grade phenyl. o grease. p-carboxy-L3-diphenylurea RNHgNHR' 29 (3) (4) 653 Good appearance-#2 grade grease.

0 Do RNH ()NHB. 23 (3) (4) 445 D0.

0 O 4,4'-b1s(3-p-tolylureido)-btphenyl RNHi'JNHW'NHi'JNHR 20 (3) (4) 481 Smooth buttery #2 grease.

'N. L. G. I. consistency grades.

The method'of forming the-thickener in 'situ in the lubricant vehicle desci ibd aboveis claimed in our'co- *pending serial No. 392,996 filed'November 18, 1953.

In Table 1 are 'setforththe data obtained on certain greases comprisingDCSSO (phenylmethyl silicone polytreated precision 204iN=ormaeHolfman bearing, is sub-' jected to a temperature of 450 F. in an oven, the other bearing, a standard New Departure 204 bearing, is at room temperature. Temperature is determined by a thermocouple inserted in the grease between the races of the bearing in the oven. Failure is adjudged to occur when (1) the temperature in the-test bearing reaches 470 F. or higher, (2) wattage inexcess of 300% of normal Wattage as required, or (3)the' bearing does not turn over at the beginning of a test cycle, (the test iscondu'cted in cycles of 20 hours operating and 4 hours at rest).

In Tables 2and'3,lbelow, are set forth data on greases comprising lubricant-vehicles other than silicone oil thickened with p-carbox'yl-1,3 diphenyl-urea and '4,4-bis-(3- phenylureido) -b'iphenyl, respectively.

1 C1H 5COOCHflCHzOCHQZCHzOCOC7H15 where z is such as to result in amaterial within the lubricating. oil viscosity range.

2 The composition of this 'v'ehicle'was asfollows: 90.6%di-2-ethylhexyl vsebacate, 3:9 commercialacrylimbase V. I. improver, 5.0% tricresyl phosphate, 0.001 U of silicone anti-foam, and 0.5% phenothiazine. 3 Kaufmann micropenetration.

."Tdble 13 Percent I Method Lubricant Vehicle y Consistency of Thickener Prep Benzyl benzoate 30 54 (3) A. I. F. Extracted Oil 25 47 (3) Fluorocarbon Oil 3 12 95 (3) 1 Kauimann micropcnetration. 2 Petroleum oil of high aromatic content. 3 Kel-F Polymer N o. 40 (product of The M. W. Kellogg 00.).

Greases of the type set forth in the above tables are stable at high temperatures although generally somewhat less stable than those prepared with silicone oil as the lubricant vehicle. Accordingly, they are more suitably employed at temperatures in the range of from about 250 F. to about 400 F. It should be understood, in any event, that While the greases of the present invention are particularly suitable for use at temperatures above 250 F. they are also extremely useful at lower temperatures. Surprisingly, greases of this type, e. g. a silicone thickened with p-carboxy-1,3-diphenyl urea, having exhibited exceptional properties at extremely low temperatures. Thus, as indicated in the following table, a grease comprising D. C. 550 silicone oil thickened with 25% by weight of p-carboxy-1,3-diphenyl urea (Grease A) exhibits substantially better low temperature properties than a grease comprising D. C. 550 thickened with 20% by weight of lithium-12-hydroxy stearate (Gerase B). It will be noted that of the two greases the grease of the present Table 4 Apparent Viscosity Data 1 Low Temperature Torque 2 (-40" F.

under 2,000 gm.-cm.

load) Apparent Viscosity (puises) Penetration 3 (Worked) Temperature Grease A 1 Method and apparatus are described in ASTM Standards on Petroleum Products and Lubricants Method .D1092-51.

Z See Specification MIL G3278 25 August 1950.

3 Same reference at above, method D217-48.

As is well known the lithium I'IZ-hydroxy *steaiate greases exhibit lower.apparent'viscosities atany .given shear rate than other metal base soaps, e. g. calcium, sodium, etc. The data in the abovetable clearly. indicate that the urea thickened grease'may be'employed at'ev'en lower temperatures than the lithium soap grease. iThese greases may have added thereto antioxidants, oiliness agents, extreme pressure additives, etc. Withoutiniany'way departing fromthe scope of 'the present invention.

Having'thus described our invention, what we claim as novel and desire to protect by LettersP-atent isde fined by the following claims:

1. A lubricantgrease comprising a lubricant-vehicle thickened with from 5 to 70% by 'weight of'at least one aryl-carbarnyl compound melting =above about 250 P. which compound is selected from the'group consisting of Grease B 19. 5 330 RNHONHR A and wherein R and R represent hydrocarbon radicals containing no more than 12 cyclic carbon atoms, which radicals are selected from the group consisting of aryl, alkyl aryl, substituted aryl, and substituted alkyl aryl radicals, and R" represents a divalent hydrocarban radical, containing no more than 12 cyclic carbon atoms, which radical is selected from the group consisting of arylene, alkyl arylene, substituted arylene, and substituted alkyl arylene radicals.

2. The lubricant grease of claim 1 wherein the lubricant vehicle comprises a silicone polymer oil in the lubrieating viscosity range.

3. The lubricant grease of claim 1 wherein the lubricant vehicle comprises an acyclic ester of an aliphatic dicarboxylic acid in the lubricating oil viscosity range.

4. The lubricant grease of claim 1 wherein the lubricant vehicle comprises a polyoxyalkylene compound in the lubricating oil viscosity range.

5. The lubricant grease of claim 1 wherein the lubricant vehicle comprises a mineral lubricating oil derived from petroleum.

6. The lubricant grease of claim 1 wherein the lubricant vehicle comprises a polyfluoro-compound in the lubricating oil viscosity range.

7. A lubricant grease comprising a lubricant vehicle thickened with from 5 to 70% by Weight of at least one aryl carbamyl compound melting above about 400 P. which compound is selected from the group consisting of (H) RCNHEV'NHPIR wherein R and R represent hydrocarbon radicals containing no more than 12 cyclic carbon atoms, which radicals are selected from the group consisting of aryl, alkyl aryl, substituted aryl, and substituted alkyl aryl radicals, and R" represents a divalent hydrocarbon radical containing no more than 12 cyclic carbon atoms, which radical is selected from the group consisting of arylene, alkyl arylene, substituted arylene, and substituted alkyl arylene radicals.

8. A lubricant grease comprising essentially a silicone polymer oil in the lubricating oil viscosity range thickened with from about to about 70% by weight of p-carboxy- 1,3-diphenylurea.

9. A lubricant grease comprising essentially a silicone polymer oil in the lubricating oil viscosity range thickened with from about 5 to about 70% by weight of N-benzoylp-aminobenzoic acid.

10. A lubricant grease comprising essentially a silicone polymer oil in the lubricating oil viscosity range thickened with from about 5 to 70% by weight of N,N'-dibenzoylbenzidine.

11. A lubricant grease comprising essentially a silicone polymer oil in the lubricating oil viscosity range thickened with from about 5 to 70% by Weight of 4,4'-bis- [3 (p-biphenylyl) -ureido] -biphenyl.

12. A lubricant grease comprising essentially a silicone polymer oil in the lubricating oil viscosity range thickened with from about 5 to by Weight of 4,4'-bis- [3 (2, S-dichlorophenyl) -ureido] -bipl1enyl.

13. The method of preparing a lubricant grease which comprises milling a mixture comprising essentially a lubricant vehicle and from about 5% to about 70% by weight of an aryl carbamyl compound melting above about 250 F. selected from the group consisting of O RNHENHR and wherein R and R' represent hydrocarbon radicals containing no more than 12 cyclic carbon atoms, which radicals are selected from the group consisting of aryl, alkyl aryl, substituted aryl, and substituted alkyl aryl radicals, and R" represents a divalent hydrocarbon radical containing no more than 12 cyclic carbon atoms, which radical is selected from the group consisting of arylene, alkyl arylene, substituted arylene, and substituted alkyl arylene radicals.

14. The method of claim 13 wherein the lubricant vehicle is a silicone oil in the lubricating oil range and said silicone oil and said aryl carbamyl compound are heated to a temperature between about 400 F. and 450 F. for a period of from about /2 an hour to about 20 hours prior to milling said mixture.

References Cited in the file of this patent UNITED STATES PATENTS 2,041,733 Werntz May 26, 1936 2,070,991 Hund et al. Feb. 16, 1937 2,468,534 Young et al Apr. 26, 1949 2,547,728 Abrams Apr. 3, 1951 2,550,746 Wohnsiedler et al May 1, 1951 2,594,286 Bryant et al Apr. 29, 1952 2,604,449 Bryant et al July 22, 1952

Claims (1)

1. 9. A LUBRICANT GREASE COMPRISING ESSENTIALLY A SILICONE POLYMER OIL IN THE LUBRICATING OIL VISCOSITY RANGE THICKENED WITH FROM ABOUT 5 TO ABOUT 70% BY WEIGHT OF N-BENZOYLP-AMINOBENZOIC ACID.