US3226323A - Lubricant composition containing a haloalkanoic compound - Google Patents

Description

United States Patent Office 3,226,323 Patented Dec. 28, 1965 3,226,323 LUBRICANT COMPOSITION CONTAINING A HALOALKANOIC COMPOUND John R. Stemniski, Swampscott, Mass., assignor to Monsanto Research Corporation, 't. Louis, Mo., a corporation of Delaware No Drawing. Filed Apr. 30, 1963, Ser. No. 277,024 6 Claims. (Cl. 25233.6)

This invention relates to liquid fluids of high thermal stability, and more particularly, provides functional fluids comprising polyphenyl ethers and certain haloalkanoic compounds as additives therefor.

Polyphenyl ethers have found wide application as functional fluids owing to their very good thermal stability, lubricity, and resistance to foam. For example, they have been found to be valuable as hydraulic fluids, as heatexchange media, as atomic reactor coolants, as diffusion pump fluids, as lubricants in motor operation generally, and particularly as jet engine lubricants.

As is known in the art, petroleum lubricants, in addition to the petroleum base stock, generally include additives which impart specific desired properties to the base stock, such as rust inhibitors, anti-oxidants, extreme pressure resisting agents, lubricity improvers, detersives and the like. The additives proposed heretofore have been designed to provide petroleum base compositions for lubrication in conventional equipment such as internal combustion engines of the automotive type, diesel engines and the like, in which the temperature of use is not excessive, not exceeding about 400 F. Advanced designs such as jet aircraft design have called for effective lubrication at higher temperatures, such as 500 F. and above, and for these designs, it was found that neither the petroleum base stock nor the conventional additives used therewith were practical. The temperatures of operation exceeded the boiling point of some lubricant composition compo-- nents, and generally were in a range at which both lubricant and additives were thermally unstable and decomposed.

Development of synthetic base stocks like the polyphenyl ethers has provided lubricant fluids stable at temperatures above the useful range of the mineral oils. There is now a demand for compositions in which such functional fluids, with thermal stability superior to that of the mineral oils, are compounded with additives enhancing desirable properties thereof. Many materials known as useful mineral oil additives are, as stated, excluded from utility in this connection by volatility and lack of thermal stability at the temperatures of use of the polyphenyl ethers. Furthermore, it has been found that additives conventional in mineral oil lubricants do not perform predictably upon combination with synthetic base stocks. There are significant differences in chemical structure of the stocks which can affect the response to additives: for example, whereas the mineral oils consist of aliphatic hydrocarbons, the polyphenyl ethers are, by contrast, aromatic ethers. Indeed, base stocks chemically different from the mineral oils may actually suffer chemical attack by certain additives, with deleterious effects on their superior high temperature properties. Temperature of operation can also affect the performance of additives, and so forth. Thus, an empirical approach has been required for the provision of improved lubricants including the polyphenyl ethers as base stocks.

One of the aspects in which the properties of the polyphenyl ether base stocks are considered deficient consists in their lubricity characteristics. The lubricity characteristics of a lubricant include its load-carrying abilities and its wear properties. Compared to other synthetic high temperature lubricant fluids, the polyphenyl ethers rank high in lubricity characteristics. However, severe design requirements for applications such as aircraft engines include effective lubrication under high pressure as Well as at high temperatures which the uncompounded polyphenyl ethers do not meet. Thus there is a demand for polyphenyl ether base composition having improved lubricity properties.

An object of the present invention is the provision of improved lubricant compositions employing polyphenyl ether fluids as base stocks.

A particular object of the present invention is to provide polyphenyl ether base compositions having improved lubricity properties.

These and other objects will become evident upon consideration of the following specification and claims.

It has now been found that compositions consisting essentially of a polyphenyl ether base fluid and an additive amount of a haloalkanoic compound of the formula where HalR- is a perhalogenated saturated aliphatic carbon chain of from 1 to 6 carbon atoms in which each of the carbon atom substituents is halogen having an atomic weight of below 40, X is a cation selected from the class consisting of hydrogen and heavy metals, and y is an integer equal to the valence of X, have unusual ability to lubricate under ultra high loads at high temperatures.

The improvement in lubricity characteristics achieved by addition of a compound of the stated kind to the polyphenyl ether base fluids is unusual and surprising. Wear is decreased at each of the test temperatures of 167 F., 400 F. and 600 F., whereas the effect of Wear-diminishing additives on polyphenyl ether base fluids is frequently temperature-dependent, apparent at only one or two points in this temperature range, and activity at one temperature is often accompanied by an actual increase in wear at another of the temperature points. The load-carrying ability of the base fluid has been raised to a different order of magnitude in accordance with this invention, which is a unique performance.

The polyphenyl ethers employed in the compositions of this invention have from 3 to 7 benzene rings and from 1 to 6 oxygen atoms, with the stated oxygen atoms joining the stated benzene rings in chains as ether linkages. One or more of the stated benzene rings in these polyphenyl ethers may be hydrocarbyl substituted. The hydrocarbyl substituents, for thermal stability, must be free of CH and aliphatic CH, so that preferred aliphatic substituents are lower saturated hydrocarbon radicals (1 to 6 carbon atoms) like methyl and tert-butyl, and preferred aromatic substituents are aryl radicals like phenyl, tolyl, t-butylphenyl and u-cumyl. In the latter case, the benzene ring supplied in the hydrocarbyl substituent contributes to the total number of benzene rings in the molecule. Polyphenyl ethers consisting exclusively of chains of from 3 to 7 benzene rings with at least one oxygen atom joining the stated benzene rings in the chains as an ether linkage have particularly desirable thermal stability.

Exemplary of the alkyl polyphenyl ethers suitable for base fluids are 3-ring polyphenyl ethers like l-(p-methylphenoxy)-4-phenoxybenzene and 2,4-diphenoxy-1-methylbenzene, 4-ring polyphenyl ethers like bis[p-(p-methylphenoxy)phenyl]ether and bis[p-(p-tert-butylphenoxy) phenyl]ether, and so forth.

Polyphenyl ethers consisting exclusively of benzene rings and ether oxygen atoms linking said rings are exemplified by the triphenoxy benzenes and aryl-substituted polyphenyl ethers such as biphenyl phenoxyphenyl ether, biphenylyloxyphenyl phenoxyphenyl ether, biphenylyl 3 ether, dibiphenylyloxy-benzene, bis(biphenylyloxyphenyl) ether, and the like.

A preferred class of the polyphenyl ethers comprises those consisting of benzene rings joined in a chain by oxygen atoms as ether linkages between each ring.

Examples of the polyphenyl ethers contemplated in this class are the bis(phenoxyphenyDethers (4 benzene rings joined in a chain by 3 oxygen atoms), illustrative of which is bis(m-phenoxyphenyl)ether. The bis(phenoxyphenoxy)benzenes are particularly valuable in the present connection. Illustrative of these are mbis(m-phenoxyphenoxy)benzene, m bis(p phenoxyphenoxy)benzene, o-bis(o-phenoxyphenoxy)benzene, and so forth. Further, the polyphenyl ethers contemplated herein include the bis(phenoxyphenoxyphenyl) ethers such as bis[m-(mphenoxyphenoxy)phenyl] ether, bis[p-(p-phenoxyphenoxy)phenyl] ether, m-(m-phenoxyphenoxy)phenyl m- (o-phenoxyphenoxy)phenyl ether and the bis(phenoxyphenoxyphenoxy)benzenes such as rn-bis[m-(m-phenoxyphenoxy phenoxy] benzene, p-bis [pm-phenoxyphenoxy) phenoxy] benzene and m-bis [m- (p-phenoxyphenoxy phenoxy] benzene.

The preferred polyphenyl ethers are those having all their ether linkages in the meta-positions since the allmeta-linked ethers are particularly advantageous because of their wide liquid range and high thermal stability. However, mixtures of the polyphenyl ethers, either isomeric mixtures or mixtures of homologous ethers, can also advantageously be used in some applications, especially where particular properties such as lower solidification points are required. Mixtures of polyphenyl ethers in which the non-terminal phenylene rings are linked through oxygen atoms in the meta and para positions have been found to be particularly suitable to provide compositions with wide liquid ranges. Of the mixtures having only meta and para linkages a preferred polyphenyl ether mixture of this invention is the mixture of 5 ring polyphenyl ethers wherein the non-terminal phenylene rings are linked through oxygen atoms in the meta and para position, and composed by weight of about 65% m-bis (m-phenoxyphenoxy) benzene, 30% m-[(m-phenoxyphenoxy) (p-phenoxyphenoxy)]benzene and 5% m-bis (p-phenoxyphenoxy)benzene. Such a mixture is liquid at room temperature (about 70 F.) whereas the three components solidify individually at temperatures above normal room temperatures.

The aforesaid polyphenyl ethers can be obtained by known procedures such as, for example, by the Ullmann ether synthesis, by a procedure involving reaction of alkali metal phenoxides such as sodium and potassium phenoxides with aromatic halides such as bromobenzene in the presence of a catalyst such as metallic copper, copper hydroxides, or copper salts.

Referring to the additives combined with the abovedescribed polyphenyl ether base fluids in accordance with this invention, these are chloroalkanoic acid compounds wherein the organic radical attached to the carboxyl function is a saturated lower aliphatic hydrocarbon radical, of from 1 to 6 carbon atoms, wherein all of the hydrogen atoms of such hydrocarbon radical have been replaced by halogen atoms having an atomic weight of below about 40, that is, chlorine or fluorine, and preferably chlorine. Thus, illustrative of the acids contemplated are perchloralkanoic acids such as trichloroacetic acid, pentachloropropionic acid, heptachlorobutyric acid, pentachloroisopropionic acid, nonachlorovaleric acid, nonachloroisovaleric acid and the like. Part of the halogen atoms substituting the hydrocarbon nucleus of the alkanoic compound may be replaced by fluorine, and the remainder by chlorine, whereby there are provided additives such as dichlorofluoroacetic acid, chlorodifluoroacetic acid, 2,3,3-trichlorodifluoropropionic acid, tetrachloro-3-fluoropropionic acid, pentachlorodifluorobutyric acid, tetrachlorotrifiuorobutyric acid, 2,2-difluoroheptachlorovaleric acid and so forth. The substituent of the carboxyl group (represented by X in the formula above) may and preferably will be hydrogen, providing acids such as the above-stated acids. Alternatively, it is within the scope of the invention to employ the oil-soluble salts of said acids with heavy metals, by which are meant metals having a density of 4 or more. Particularly preferred in this connection are heavy metals of group II of the periodic table, including mercury, cadmium, and asthe salt-forming metal of choice, zinc, and of group IV, especially tin and lead. Alternatively, the selection depending on such considerations as the reactivity and availability of the metals, there may be employed salts of other heavy metals, such as those of group I, like copper, silver and so forth; of group III, like indium and thallium; of group IV, like thorium; of group V, like antimony and bismuth; of group VI, like tungsten and tellurium; and of the transition elements, like iron, cobalt, nickel and so forth.

Thus, illustrative of the salts employed in accordance with this invention are zinc bis(trichloroacetate), cadmium bis(trichloroacetate), mercury bis(trichloroacetate), tin bis(trichloroacetate), tin tetrakis(trichloroacetate), lead tetrakis(trichloroacetate), cupric bis(trichloroacetate), cuprous trichloroacetate, bismuth tris(pent-achloropropionate), zinc bis(pentachloropropionate), zinc bis(heptachlorobutyrate), nickel bis(dichlorofluoroacetate), zinc bis(dichlorofluoroacetate), copper bis(trichlorodifluoropropionate) and the like.

The haloalkanoic acid compound is combined with the fluid polyphenylether base fluid to the extent of, generally, between about 0.01% and 10% by weight of the fluid. Particular effective amounts depend on the nature of the individual additive and of the ether fluid. In most cases the ability of the agent with respect to extreme pressure lubrication improvement increases as the concentration is increased. Remarkably low concentrations of the additives in the compositions presently provided are eflective to give extremely high lubricity properties. Indeed, it has been shown that treatment of frictionally contacting metal surfaces with an additive of the invention prior to lubrication thereof with a polyphenyl ether fluid provides a suflicient residue on the metal surfaces to produce better than double the weld point values obtained without such prior treatment. Concentration limits may also affect the selection of a. suitable proportion of additive and base fluid in the lubricant compositions.

It will be appreciated that the compositions of this invention, in addition to the polyphenyl ether base fluid and the haloalkanoic compound additive, may additionally include any of a wide variety of further additives. For example, the polyphenyl ethers are inclined to increase in viscosity on prolonged exposure to elevated temperatures on the order of 550 F., particularly in the presence of air. To diminish this undesirable tendency, the polyphenyl ether base fluids are frequently combined with an antioxidant, such as a high molecular weight amine, an organo-metallic compound, and so forth. Furthermore, viscosity index improvers such as polymeric materials like polymethacrylate alkyl esters, dispersants and additives improving other aspects of the lubricant composition may be employed in these compositions if desired.

The invention is illustrated but not limited by the following examples, in which the tests employed to determine the reported adjuvant effects of the haloalkanoic compounds when employed with the polyphenyl ether lubricant base fluid are conducted as follows:

The antiwear and extreme pressure lubrication char- ;acteristics of the lubricant compositions are evaluated by means of the well known Shell 4-Ball Extreme Pressure Tester and the Shell 4-Ba1l Wear Machine, as described, for example, in the Lubrication Engineers Manual (US. Steel Corp., 1960). These testers include 4 balls of stainless steel arranged in the form of an equilateral tetrahedron. The three lower balls are held immovably clamped in a holder to form a cradle in which the fourth upper ball is caused to rotate at 1200-4800 r.p.m. about a vertical axis in contact with the three lower stationary balls. The contacting surfaces of the balls are immersed in the test fluid which is held in a cup surrounding the assembly. A modified cup and heater assembly is used to evaluate lubricants at elevated temperature and provisions are made to permit high temperature testing under an inert atmosphere: see The Study of Lubrication in Using the 4-Ball Type Machine by R. G. Larsen, Lubrication Engineering, vol. 1, 35-43, 59 (August 1945).

For determination of the extreme pressure properties in the 4-ball EP tester, the upper ball is rotated while the load is gradually increased by increments of kg. until the balls are welded together Within a 1-minute test period.

For measurement of wear in the wear machine, the upper ball is rotated under a load of 40 kg. for one hour at each of the temperatures for which wear scar diameters worn in the surface of the three lower stationary balls are reported.

Example 1 A lubricant composition is prepared by combining trichloroacetic acid with a polyphenyl ether of the following composition, by weight: 65% m-bis(m-phenoxyphenoxy) benzene, 30% m-[m-phenoxyphenoxy)(p-phenoxyphenoxy) benzene, 5 m-bis (p-phenoxyphenoxy)benzene, in a proportion of 1 gram (g.) of the acid to 100 g. of the base fluid.

A portion of the base fluid used to provide the abovedescribed composition is reserved, free of additive, and run through the same sequence of tests, to provide a basis for comparison.

Using the base fluid alone, in the extreme pressure test, the balls weld at a pressure of 150 kg.

Employing the lubricant composition described above, consisting of 1% of trichloroacetic acid combined with the same polyphenyl ether, the extreme pressure tester is taken to its load limit, 1000 kg. without achieving a weld of the balls.

Using the Shell 4-ball wear tester, the wear scar diameters determined for the lubricant composition of this example including trichloroacetic acid and for the base fluid without additive are as follows:

Wear Scar Diameter, mm. 167 F. 400 F. 600 F.

With Additive 1.36 2.48 2.10 Without Additive 1.79 3.30 2.93

Example 2 Four of the stainless steel balls used in the Shell 4- ball test are soaked in molten trichloroacetic acid for two hours, and then wiped clean and used to determine the weld point of untreated polyphenyl ether of the composition described in Example 1. The weld point obtained is constant at 350 kg., whereas the same polyphenyl ether fluid when employed with untreated balls welds at 150 kg. Weld points of 350-400 kg. are also obtained when the treatment time for soaking in molten trichloroacetic acid is diminished to one-half hour.

6 Example 3 A lubricant composition is prepared by combining zinc bis(trichloroacetate) with a polyphenyl ether base fluid of the composition stated in Example 1, to the limit of the solubility of the salt at room temperature. Zinc bis(trichloroacetate) is prepared by heating 2 parts (by weight) of trichloroacetic acid to form a melt, adding 1 part of zinc acetate and stirring, washing the cooled mixture with petroleum ether to remove acetic acid, and drying. The filtered solution of the additive in the polyphenyl ether is subjected to test of its extreme pressure properties as compared to the untreated base fluid. The weld point is increased.

Using the tin, antimony, lead and bismuth salts of trichloracetic acid, trichloropropionic acid and dichlorofluoroacetic acid, similar results demonstrating an enhancement in the lubricant characteristics of the polyphenyl ether base fluid are obtained.

While the invention has been described with reference to specific preferred embodiments thereof, it is to be appreciated that modifications and variations can be made without departing from the scope of the invention, which is limited only as defined in the appended claims.

What is claimed is:

1. A lubricant composition comprising a major amount of a polyphenyl ether base fluid and a haloalkanoic acid compound of the formula (HalRCOO) X where Hal-R is a perhalogenated saturated aliphatic carbon chain of from one to six carbon atoms in which each of the carbon atom substituents is a halogen atom having an atomic weight below 40, X is a cation selected from the class consisting of hydrogen and heavy metal cations, and y is equal to the valence of X, said haloalkanoic acid compound being present in said composition in an amount sufficient to improve a lubricity property of said polyphenyl ether fluid selected from the group consisting of wear resistance and load-carrying ability 2. The composition of claim 1 wherein said haloalkanoic compound is a perchloroalkanoic acid.

3. The composition of claim 1 wherein said haloalkanoic compound is trichloroacetic acid.

4. The composition of claim 1 wherein said haloalkanoic compound is an oil-soluble heavy metal salt of trichloroacetic acid.

I 5. The composition of claim 1 wherein said haloalkanoic compound is a salt of trichloroacetic acid with a heavy metal of Group II of the Periodic Table.

6. The compositions of claim 1 wherein said haloalkanoic compound is zinc trichloroacetate.

References Cited by the Examiner UNITED STATES PATENTS 2,559,629 7/1951 Berry 25258 X 2,802,028 8/1957 England 25235 X 2,940,929 6/1960 Diamond 252-33.6 3,080,321 3/1963 Blake et al. 252-52 X FOREIGN PATENTS 752,383 7/1956 Great Britain.

842,647 7/ 1960 Great Britain.

851,651 10/1960 Great Britain.

DANIEL E. WYMAN, Primary Examiner.

Claims (1)

1. A LUBRICANT COMPOSITION COMPRISING MAJOR AMOUNT OF A POLYPHENYL ETHER BASE FLUID AND A HALOALKANOIC ACID COMPOUND OF THE FORMULA (HAL-R-COO)Y-X WHERE HAL-R IS A PERHALOGENATED SATURATED ALIPHATIC CARBON CHAIN OF FROM ONE TO SIX CARBON ATOMS IN WHICH EACH OF THE CARBON ATOM SUBSTITUENTS IS A HALOGEN ATOM HAVING AN ATOMIC WEIGHT BELOW 40, X IS A CATION SELECTED FROM THE CLASS CONSISTING OF HYDROGEN AND HEAVY METAL CATIONS, AND Y IS EQUAL TO THE VALENCE OF X, SAID HALOALKANOIC ACID COMPOUND BEING PRESENT IN SAID COMPOSITION IN AN AMOUNT SUFFICIENT TO IMPROVE A LUBRICITY PROPERTY OF SAID POLYPHENYL ETHER FLUID SELECTED FROM THE GROUP CONSISTING OF WEAR RESISTANCE AND LOAD-CARRYING ABILITY.