US3798162A - Lubricating compositions containing metal phosphonates - Google Patents

Abstract

THE EXTREME PRESSURE PROPERTIES OF ORGANIC FLUIDS ARE IMPROVED BY ADDING THERETO A SMALL AMOUNT OF A GOLD HYDROCARBYL HYDROCARBYLPHOSPHONATE COMPLEXED WITH A BASIC NITROGEN COMPOUND OR ANOTHER METAL HYDROCARBYL HYDROCARBYLPHOSPHONATE WHICH MAY OR MAY NOT BE SO COMPLEXED.

Description

3,798,162 LUBRICATING COMPOSITIONS CONTAINING METAL PHOSPHONATES Joseph J. Dickert, Jr., and Carleton N. Rowe, Lower Makefield Township, Pa., assignors to Mobil Oil Corporation No Drawing. Continuation-impart of abandoned application Ser. No. 70,901, Sept. 9, 1970. This application Aug. 14, 1972, Ser. No. 280,604

Int. Cl. C10m 1/44, 3/38, 5/24 US. Cl. 252-32.5 15 Claims ABSTRACT OF THE DISCLOSURE The extreme pressure properties of organic fluids are improved by adding thereto a small amount of a gold hydrocarbyl hydrocarbylphosphonate complexed with a basic nitrogen compound or another metal hydrocarbyl hydrocarbylphosphonate which may or may not be so complexed.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of US. application Ser. No. 70,901, filed Sept. 9, 1970 and now abandoned.

BACKGROUND OF THE INVENTION Field of the invention This invention relates in one of its aspects to novel lubricant compositions. More particularly, it relates to such compositions containing anti-wear amounts of metal phosphonates either uncomplexed or complexed with a basic nitrogen compound. In another of its aspects, the invention relates to a novel method of protecting rubbing metal surfaces.

Description of the prior art The metal surfaces of machinery or engines operating under heavy loads wherein metal slides against metal may undergo excessive wear or corrosion. Often the lubricants used to protect the metal surfaces deteriorate under such heavy loads and as a result, do not prevent wear at the points of metal to metal contact. Consequently, the performance of the machine or engine will suffer, and in aggravated cases the machine or engine may become completely inoperative.

There have been many attempts to devise additive systems which would provide satisfactory protection, but these have not always been successful. The metal phosphonate additives of the present invention are believed capable of overcoming some of the deficiencies of prior art additives and to provide lubricating oil compositions with enhanced anti-Wear characteristics.

US. 2,758,971 describes a class of metal phosphonates which are disclosed as having properties which prevent breakdown of oils at high temperatures. These additives may be described as diorgano hydroxyorganophosphonates or certain metal salts thereof.

In another US. Pat. (2,792,374) are disclosed the alkali metal salts of certain alkyl alkylphosphouic acids as defoamants in aqueous systems.

Still another US. Pat. (2,982,727) discloses lubricating oil compositions containing certain salts of oxygencontaining esters of phosphorus. The esters are phosphonates similar to those described in US. 2,758,971.

nited States Patent 0 3,798,162, Patented Mar. 19, 1974 SUMMARY OF THE INVENTION In accordance with the invention there are provided lubricant compositions comprising a major amount of a lubricant and an amount suflicient to impart anti-wear properties thereto of a compound of the formula:

wherein R is hydrocarbyl containing from 14 to about 30 carbon atoms, R is hydrocarbyl containing from 1 to about 6 carbon atoms, X is a basic nitrogen-containing compound, Z is from 1 to 4, q is 0 or 1, M is a metal selected from the group consisting of Groups I-B, II-B, and IV-A of the Periodic Table and n is the valence of M, q being 1 and n being 3 when M is gold.

When used for anti-wear action, these compounds may be present in the lubricant in a concentration of from about 0.001 to about 10%, preferably from about 0.1 to about 5% by weight thereof.

DESCRIPTION OF SPECIFIC EMBODIMENTS As has already been stated, R of the above formula contains from 1 to about 6 carbon atoms. Preferably, R will contain from 1 to 3 carbon atoms and more preferably R will be the methyl group. Thus, among those compounds contemplated will be the following:

R R M MethyL. Cu, Au, Ag, Pb, Zn or Hg.

Do-. yl Same as above. Do- Tnacontyl.-. Do

Hexadecyl D0. yl Octadesyl. Do. Docosyl Do. Tricosyl.-- Do. Tetraeosyl Do.

The above and other compounds may be prepared by known means. One such means involves, first, the preparation of the phosphonic acid by reacting a hydrogen phosphonate [(RO) P(O)H] and an olefin under the influence of a free-radical catalyst, hoydrolyzing one of the methyl groups in a basic medium and acidifying, essentially as follows:

NaOH

Many methods exist for producing the salts of this invention from the acid. Initially, ammonia or ammonium hydroxide may be reacted with the acid to form the intermediate ammonium phosphonate. This in turn is reacted with, for example, a gold or copper compound, preferably in the form of its halide (e.g., auric chloride), to yield the final salt or the metal complex when excess base is present.

More specifically the reaction between the ammonium phosphonate and the metal halide to form the salt is carried out, usually, at room temperature, or with moderate heating, using equimolar amounts of reactants. The reaction, which usually is run in water, produces a solid product which may be isolated from the reaction medium by any conventional means of separation.

For the most part, the metal phosphonates of this invention, as well as the complexes thereof, appear to function as most conventional additives do. That is, it is believed that they undergo chemical decomposition during use and that such decomposition products actually react with the metal of the surfaces being lubricated and form a film which reduces mechanical wear.

Several of the phosphonates of the present invention, however, do not depend for their effectiveness of forming a film on the metal by chemical means. It has been observed that the gold complexes and the silver and copper salts or their complexes, actually have their metal ions reduced to the free metal, which in turn forms a very thin film of such free metal on the surface being lubricated. The film thus deposited is a fixed, almost permanent solid lubricant. In other words, the solid fihns are formed, thereby permitting the surfaces of the lubricated parts to move against each other with minimal wear, or no wear at all. Even if the solid film does wear, no substrate metal is lost (assuming some film is always present) because it is not chemically involved in the formation of the copper or gold film.

With respect to the gold, silver, and copper compounds, it is theorized that, since they deposit a coating of a solid that is softer than the metal substrate, this may provide improved lubrication by providing a softer, more yielding surface. However, no evidence has been found that this phenomenon of deposition is operative with the use of the other phosphonates disclosed herein.

The gold, silver and copper compounds of this invention are initially soluble in the oil phase. Breakdown during lubrication begins the deposition of the metallic solid upon the substrate metal of the mechanism being lubricated. Thus, the gold, silver and copper compounds can actually function two ways in keeping the sliding metal surfaces from wearing.

The phosphonates of this invention are preferably used in lubricating oil compositions. These include mineral oils, both paraflinic and naphthenic, and synthetic oils. These synthetic oils include synthetic ester lubricating oils such as esters of 2,2-disubstituted, 1,3-propanediol, trimethylolpropane, or pentaerythritol with monocarboxylic acids having from 4 to about 25 carbon atoms. The synthetic oils also include polyolefin fluids, polysiloxane fluids, polyglycol ether fluids and polyphenyl ether and polyphenyl thioether fluids. Suitable thickeners may be added to the liquid compositions to produce greases or other thickened forms of lubricants. Other additives, such as antioxidants and detergents, may also be present, collectively or alternatively.

The basic nitrogen-containing compound useful in forming the complexes of this invention may be selected from a wide range of materials. They include primary, secondary, and tertiary alkyl amines, wherein the alkyl group contains from 1 to about 30 carbon atoms, primary, secondary and tertiary aryl amines, the aryl group containing from 6 to about 30 carbon atoms, the polyalkylene polyamines such as ethylene diamine, diethylene tn'amine, triethylene tetramine, tetracthylene pentamine, pentaethylene hexamine, nonaethylene decamine, and the like. Also included are heterocyclic amines, both cycloaliphatic and aromatic.

Illustrative of the alkylamines that may be used are the mono, di-, and trimethylamines, the mono-, di-, and trihexylamines and the like. The mono-, di-, and triphenylamines illustrate aryl amines that one can employ. Pyridine is a useful heterocyclic aromatic amine.

The following specific embodiments will serve to illustrate the practice of this invention. It will be understood that no limitation on the scope of the invention is intended by such illustrations.

EXAMPLE 1 About 45 g. (0.2 mole) of l-hexadecene and about 55 g. (0.5 mole) of dimethyl phosphite were placed in a 250 ml. reaction flask equipped with a stirrer, thermometer, reflux condenser, addition funnel, and a nitrogen inlet tube. The system Was flushed well with nitrogen; the reaction mixture was stirred and warmed to about 150 C.

About 2.0 g. of di-t-butylperoxide was added slowly to the reaction mixture over about hour. The heating and stirring were continued during the addition and for 1 /2 hours thereafter. The excess dimethyl phosphite was removed by vacuum distillation. 69.5 (0.2 mole) of dimethyl n-hexadecylphosphonate was recovered.

About 67 g. (0.2 mole) of the above dimethyl n-hexadecylphosphonate was mixed with a solution of about 10 g. (0.25 mole) of sodium hydroxide in about 150 ml. of methanol. The mixture Was stirred and warmed at reflux temperature for about 3 hours. The mixture was allowed to cool to room temperature and about 0.25 mole of HCl as concentrated hydrochloric acid solution was slowly added to the stirred mixture. This was followed by the addition of 500 ml. of water. The product was recovered on a suction filter and washed twice, each time by stirring in a beaker with 500 ml. of water, then recovering by suction filtration. The crude product was recrystallized from a hexane-petroleum ether mixture to give the pure methyl n-hexadecylphosphonate.

About 9.6 g. (0.03 mole) of the above methyl n-hexadecylphosphonate was mixed with a solution of 5 m1. ammonium hydroxide (28-30% sp. g. 0.9). About 3.9 g. (0.1 mole) HauCl 3H O was dissolved in 20 ml. of water and added to the phosphonate solution. An excess of ammonium hydroxide was added and the mixture was extracted twice with diethyl ether. The solvent was removed from the ether extract by distillation. The solid product was washed twice by stirring with water and decanting. The last of the water was removed from the product by azeotropic distillation with benzene and finally removing the benzene. A phosphonate was formed in which the gold was Au+ and which was complexed with four parts of ammonia per part of gold phosphonate.

EXAMPLE 2 About 232 g. (0.75 mole) of l-docosene and about 247 g. (2.25 moles) of dimethyl phosphite were placed in a 2 liter reaction flask equipped with a stirrer, thermometer, reflux condenser (with a drying tube attached to the outlet) and an addition funnel. The flask was purged with nitrogen before adding the reagents. The mixture was stirred and warmed to about 150 C. While maintaining the temperature, about 3 g. of di-t-butylperoxide was added in small increments over about one hour. The temperature of the stirred mixture was maintained at about 150 C. for another 'hour after the peroxide addition was completed.

The mixture was allowed to cool and the apparatus was adapted for vacuum distillation. The excess dimethyl phosphite was removed by distillation up to a pot temperature of about C. and an estimated pressure of 10-20 mm. Hg. 311 g. of dimethyl n-docosylphosphonate was recovered.

About 300 g. (0.72 mole) of the above dimethyl ndocosylphosphonate was mixed with a solution of about 40 g. (1 mole) of sodium hydroxide in about 450 ml. of methanol. The mixture was stirred and warmed at reflux temperature (about 68 C.) for about 3 /2 hours and then allowed to cool. While the temperature was kept between 45-50 C. (to keep the product liquid) 83 ml. of aqueous 37% hydrochloric acid solution and 400 ml. water was added to the mixture. This produced an unfilterable emul- 6 EXAMPLE 5 sion at this stage. About 2 volumes of acetone were added 5 and the product isolated on a suct1on filter. The product Similarly, additional complexes of gold phosphonates was recrystallized from a solution of benzene and petroleum ether. After drying 299 g. of methyl n-docosylphosi f ifi i fi according to Example Analyses phonate was obtained. in lcate e o owing structures:

A small amount (e.g. 0.2 mole, about 8.1 g.) of the 10 EXAMPLE 6 above methyl n-docosylphosphonate was dissolved in about 50 m1. of Warm 95% ethanol. An equivalent amount l of a water soluble salt of the desired metal [e.g., 0.1 mole CH Q-P ()--A .4NH Pb(NO .02 mole AgNO .01 mole CuCI etc.] was H mixed with the warm ethanol solution of the phosphonate 22 a and warmed on a steam bath for 10-15 minutes. After cooling, the solid product was isolated by filtration and EXAMPLE 7 purified by washing and recrystallization. o

Alternately, the methyl n-docosylphosphonate was dis- 1 solved in an equivalent amount of ammonium hydroxide 0 'II solution, then reacted with the metal ion. 0 E1 3 EVALUATION OF PRODUCTS The compounds of Examples 3 to 7 were also tested The test used to obtain the data in the following table in the Four-Ball Test described above. The phosphonate was the well-known Shell Four-Ball Test. In this test, three 25 to be tested was placed in a base grease prepared by addsteel balls of 52100 steel are held in a ball cup. A fourth ing a modified clay thickener to polydecene fluid. The ball positioned on a rotatable vertical shaft is brought into test was run for minutes at 200 F. under a 20 kg. contact with the three balls and is rotated against them at load at '600 rpm. Following are illustrative results: a. predetermined load. The test lubricant is added to the ball cup, and at the end of the test, the steel balls are 30 examined for wear scar. The size of the scar and rate of g gi wear, Wear wear per unit sliding distance represents the effectiveness phosphoscar, rate, of the lubricant as an anti-wear agent. Example The data in the table below was obtained by placing a None 0.401 016x101: metal methyl alkylphosphonate in n-hexadecane (except 21:23:: 1322 1288; where noted) and running the above noted test under the 7 7.5 .356 .42x1oconditions shown.

Percent Wear Wear phospho- Temp., Load, Time, sear, rate, 00.] Metal Phosphonate nate F. kg. Rpm. min. mm. em. None None None 200 20 600 30 0.775 12.9X10- Cu" O p 1.31 200 20 600 30 .349 .38X10 Il/ CHsOP 1.51 200 20 600 30 .302 .16Xl0- jiiiij.-ff?f.ii flflf 1. 53 200 20 600 30 .370 .51X10-11 Pb+ do 1.52 200 20 600 30 .483 1.77x10- Au" O 0.475 200 20 600 30 .368 .50X10' CHaO Cu al Au+ Same as above 0.475 300 20 600 30 .351 .39X10- Copper phosphonates were prepared in a manner simi- We claim: lar to the procedure of Example 2. These, however, were 1. Lubricant compositions comprismg a lubricating oil complexed with nitrogen-containing compounds, and or grease and an amount suflicient to impart anti-wear analyses for carbon, hydrogen, phosphorus, nitrogen, and properties thereto of a compound of the formula metal content indicated the following structures: 0

EXAMPLE 3 Rl 1 O O M. ZX H I Jn )q CH3OP-O-Cu-2NH;

I J wherein R is a hydrocarbyl group contammg from 14 to 022m 2 about 30 carbon atoms, R' is a hydrocarbyl containing EXAMPLE 4 from 1 to about 6 carbon atoms, X is selected from the group consisting of alkylamines having from 1 to about 30 carbon atoms, arylamines having from 6 to about 30 CHaoPO ICu'NH2C2HNH' carbon atoms, ammonia and polyalkylene polyamines, Z 2 1 5 is from 1 to 4, q is 1, M is a metal selected from the group 7 consisting of Group I-B, Group II-B and Group IV-A of the Periodic Table and n is the valence of M, q being 1 and n being 3 when M is gold.

2. The composition of claim 1 wherein the metal is selected from the group consisting of copper, silver, zinc, mercury and lead.

3. The composition of claim 1 wherein the metal is 1 old.

g 4. The composition of claim 1 wherein the metal is copper.

5. The composition of claim 1 wherein the metal is silver.

6. The composition of claim 1 wherein R is docosyl.

7. The composition of claim 1 wherein R is methyl.

-8. The composition of claim 1 wherein M is Cu, Z is 2, and X is NH 9. The composition of claim 1 wherein M is Au, Z is 2, and X is NH2C2H4NH2.

10. The composition of claim 1 wherein M is An, Z is 4, and X is NH 11. The com-position of claim 2 wherein R is docosyl and R is methyl.

12. The composition of claim 2 wherein R is hexadecyl and R is methyl.

13. The composition of claim 11 wherein the metal is gold.

14. The composition of claim 11 wherein the metal is copper.

15. The composition of claim 11 wherein the metal is silver.

References Cited UNITED STATES PATENTS 2,382,043 8/ 1945 Farrington et al 252-325 2,758,971 8/1956 Mikeska 25232.5 2,837,481 6/1958 Hotten et a1 25232.5

PATRICK P. GARVIN, Primary Examiner A. H. METZ, Assistant Examiner U.S. Cl. X.R. 260-430