US2223793A - Lubricating composition - Google Patents

Description

Patented Dec. 3, 1940 LUBRIOATIN G COMPO SITION Norman E. Peer-y, San Francisco, Calif., assignor to Shell Development Company, San Francisco,

Calif, a corporation of Delaware No Drawing. Application November 14, 1938;

BerialNo. 240,341 a s Claims.- (01. 252-48) The present invention relates to improved lubricating compositions and a method for producing the same. .As is well-known, the recent trend in modern machinery design has been toward more powerful and flexible machinery and toward increasing" the efliciency by decreasing the effective area of contact of bearing and gear-surfaces. The extent to which these trends may be carried is, however. sharply limited by the problems of lubrication thereby created. Certain types of bearings and gears, for instance, have recently come into wide use in which the operating pressures per unit' area of working surface are so high that ordinary mineral oil lubricants will not provide adequate lubrication for satisfactory operation.

The main lubrication difliculty created by the newer machinery design is. the diiliculty in maintaining a film of lubricant between the lubricated metal parts. Under the high pressures per unit area of working surface employed, the thin film of'lubricant between the metal surfaces is apt to rupture and thus allow metal-to metal contact. This results in wear or souiling, and under extreme conditions even to actual welding of the bearing metals.

It has been found that the addition of certain .dopesor modifiers to ordinary lubricants increases the fllm strength and hence their ability to withstand greater working pressure without rupturing. Compounds capable of imparting this property to lubricants are commonly referred to as "extreme pressure dopes or "E. P. dopes." and lubricating compositions containing them as "E. P. lubricants."

Although numerous compounds are capable of imparting E. P. characteristics to lubricants, nearly all of the known compounds have certain more or less obiectionable characteristics. The main disadvantage often found in'manyyof the E. P. compounds in use is the tendency to corrode the bearing surfaces and to create a sludge in the lubricant during use. Other disadvantages often found are the tendency'to separate from the lubricant in cold weather and to raise the cloud and pour points oi the lubricant.

Several E. P. compounds used are mixtures oi two or more-ingredients such as lead soaps, ac-

tive sulfur, inactive sulfur, saponiflable ma table oil etc. Most of these. although showin high film strength on laboratory tests tend to I form sludge or corrode the metal, especially alloy bearing metals, when used under severecon- In general, it'has been found that halogen (particularly chlorine) compounds tend to impart E. ,P. characteristics to lubricants. Although certain organic chlorinecompounds are used to some extent, many oi these compounds 5 tend to break down during severe use, especially in the presence of moisture and thus cause corrosion of the metal parts. Another class of compounds found to impart E. P. characteristies to lubricants is the neutral organic esters 19 of inorganic polybasic acids, especially phos phoric and thiophosphoric acids; These esters likewise tend to hydrolyze somewhat in the presence of moisture toform acid compounds which .cause corrosion. The majority oi these 'compounds furthermore must be used. in appreciable quantities in order to impart the desired E. P. characteristics and in such quantities that they tend to promote channelling of the lubricant. 20

An object of the present inventionis to provide new and superior E. P. lubricant compositions. Another objectof the invention is toprovide a class of E. P. compounds which, when added to lubricants; causes no substantial change in the other physical properties ofthe lubricant, such as the viscosity index. odor, pour point, channelling tendency. etc. Still another object 01. the invention is to provide a new class of E. P. compounds possessing the desirable properties of the chlorine compounds and of the organic esters of phosphoric and thiophosphoric acid hitherto used, but without their disadvanj tages. Still another important object or" the inv'entiorris to provide: a new class of E.-P. compounds, which, when added to lubricants, im-

part extreme pressure characteristics but do not hydrolyze. corrode the metal parts or form sludge upon use, even in the presence oi water and under severe conditions. I

' According to the present invention, common lubricants are made capable of-' afiordlng lubrication under extreme pressure conditions without increasing the sludging or corrosion tend-'- ency of the lubricant by dissolving therein a small quantity of a suitable tertiary alcohol .es-.

' ter of, a halide of phosphorus containing two halogen'atoms attached to the phosphorus atom. The tertiary alcohol groups of the compounds of the'present inventionhave the generalstructure wherein R1, R2 and R: represent the same or diiferent lipophile groups, and x represents oxygen or sulfur. As an example of the most suit- 7 esterP-- Halz in the case of phosphorous compounds, and

Ester-P=Hah in the case of phosphoric compounds wherein, in both cases, Hal represents an atom of halogen, and ester represents an alcohol residue. of the above-described class.

These compounds, particularly the phosphorous compounds, are exceptionally well suited as E. P. compounds, since they effectively raise the film strength or lubrlcants;'they are not corrosive or sludging; they have a suitable solubility in lubricants; they are effective in small concentrations and do not appreciably .alter the other physical properties of the lubricant; they are easy to prepare, inexpensive, easily handled and do not possess an objectionable odor; they are stable to heat and do not volatilize from the lubricant.

The following typical example clearly demonstrates the effectiveness of the present type of E, P. compounds in increasing the film strength of ordinary lubricants. Three samples of a lubricating oil which had a viscosity of 80 seconds (S. U. at 210 F.) were prepared. The first sample wa left undoped and to the second and third were added .05% and 1.5% by weight of triphenyl methcxy phosphorus dichloride, respectively. Tests were conducted on the Timken tester to determine the film strength of the samples with the following results:

Timken Sample Lbs/in. failure As can be seen. the addition of only .5% of the E. P. compound greatly enhanced :the load carrying capacity of the hydrocarbon oil, while the addition of 1.5% .rendered the oil suitable for use under the most severe conditions of extreme pressure.

While I do not desire my invention to be limited by the soundness or accuracy of any theories advanced to explain the advantageous results obtained, I believe that the excellent ability of the present E. P. compounds to impart E. P. characteristics to ordinary lubricants is due to the presence of the the very strong polar group, i. e., the phosphorus-halogen linkage in combination methoxyphenyl with the very voluminous lipophillic group of strong negative character.

It will .be noticed that'the lipophillic ester groups of the present invention are much more voluminous than the ester groups of other esters of phosphorus, such as triphenyl phosphate, tricresyl phosphate, etc., hitherto used. As a consequence, it is to be expected that the present compounds will be effective in much lower concentrations, and this is indeed the case.

The phosphorus-halogen linkage contained in the present compounds, it is seen. combines the effective polar groups of both the neutral esters of phosphorus and the chlorine compounds hitherto found to possess valuable E. P. characteristics. While organic esters of phosphorus containing one or two halogen atoms attached to the phosphorus atom have long been known, it was-hitherto believed impossible to utilizethese compounds as E. P. compounds due to the fact that most compounds of this structure readily hydrolyze to give halogen acid and an acid ester of phosphorus. Thus, for example, all of thehalogen-containing esters of phosphorus of the general structures or. on on c r ng, o=roa, r ms in r ce HaI Hal HaI mu wherein R represents an aromatic or alkyl group are readily hydrolyzed under mild conditions,

most of them, in fact,- being hydrolyzed almost completely by simply contacting with cold water. I have found, however, that if the lipophillic ester group attached to the phosphorus atom through oxygen or sulfur is a suitable tertiary alcohol group. verystable compounds are formed which are exceptionally resistant to hydrolysis. The extraordinary resistance of the present compounds to hydrolysis will be appreciated when compared with other comparatively stable compounds such as the chlorinecompounds and esters of phosphorus, commonly used in E. P. lubricants. Thus, for example, the ordinary chlorine compounds commonly used and the common organic esters of phosphoric acid such as tributyl phosphate, triphenyl phosphate, tricresyl phosphate, triphenyl phosphite, etc., very slowly hydrolyze in'the presence of water, especially if hot, and are readily hydrolyzed in a short time by heating with dilute alkali. The present compounds, on the other hand, show no hydrolysis with either hot or cold water and can even in most cases be boiled with concentrated aqueous caustic soda without any noticeable hydrolysis. As a consequence of the stability and resistance of the present compounds against hydrolysis,

these compounds may be used in lubricants even in the presence of moisture without fear of corrosion or sludging.

The present E. P. compounds may be dissolved in any of the common lubricants such as mineral oils, vegetable oils and the like to increase their fllm strength. Mineral oil, for example, may be only slightly refined or highly refined with sulfuric acid and/or by treatment with any of the solvents commonly used for that purpose. Since refining treatments in general decrease the film strength of the oil, especially refining by solvent extraction, the present E .1. compounds may be most advantageously used in highly refined oils. For example, very highly refined mineral oils having low film strength may be greatly improved by the addition thereto of only about 0.1% of the present E. P. compounds, These compounds may, of course, be used in oils of various viscosities, synthetic mineral oils, mixtures of mineral oils containing pour point depressors, waxes, etc., grease bases, cutting and pouring oils, etc. a

The present E. P. compounds may be used in I any proportion from traces up to their limit of solubility, While, in general, concentrations in film strengths may be obtained by employing aromatic B'I'OUDS increases.

larger quantities.

The solubility of the present E. P. compounds in mineral oils varies considerably with the nature and size of the iipophile groups, increasing, in general, as the number of carbon atoms in the The compounds of the present invention, especially the lower members, such as tritoluenyl methoxy phosphorous dichloride, tri-p-tertiary butyl phenyl methoxy phosphorous dichloride, etc., have the advantage of not being too soluble in the usual mineral lubricants. It is, therefore, practical to saturate the mineral lubricant with. these compounds. This is of advantage since with such lubricant compositions, adsorption of the E. P. compound on the bearing surface is enhanced.

The present compounds may be easily prepared, in general, with very good yields according to well-known methods. One suitable method, for example, is to add the alcohol to half its weight of the desired halide of phosphorus at about 0 C.. allow to stand for a short time and then heat to about 100 C. to complete the reaction. The product may be recovered pure from the reaction mixture by washing with water, dissolving in a solvent such as chloroform, and reprecipitating by adding a diluent such as acetone.

Although throughout the present description I have frequently referred to the problem of lubrication under conditions of extreme pressure, and have chosen to refer to my new lubricating composition in the customary manner as extreme pressure or E. P. lubricants, it is to be understood that the lubricant compositions of the present invention may also be used to advantage for lubrication under moderate or even very mild conditions, such as, for example, in the lubrication of the bearings, etc., in internal combustion engines, inordinary gear transmissions, reduc- I tiongear assemblies, cable greases, cupgreases and the like. In such cases, where the lubricant is designed to be used under conditions involving only'm'oderate' working pressures only very small I quantities such as; for example, 0.05% to 0.15%

in the lubricant than is essential for the purpose for which it is to be used is not detrimental to the lubricant.

I claim as my invention:

1. A lubricant comprising a mineral lubricating oil and an amount suflicient to impart extreme pressure properties of a compound having the structure wherein R1, Rz-and Ra represent aryl radicals,

X is an element selected from the group consisting of oxygen and sulfur, and Y is a phosphorous halide radical containing two halide atoms at structure wherein R1, R2 and R3 represent aryl radicals, X is an element selected from the group consisting of oxygen and sulfur and Y is a radical selected from the group consisting of halogenand --Phalogen' halogen O 5. A lubricant comprising a mineral lubricating oil and an amount suificient to impart extreme halogen pressure properties of an ester combining aryl tritertiary carbinol with a halide of phosphorus, said ester containing two halogen atoms attached to the phosphorus.

6. A lubricant comprising a mineral lubricating oil and an amount suflicient to impart extreme pressure properties of a mono ester combining butyl phenyl tritertiary carbinol with phosphorus trichloride, said ester containing two atoms of chlorine attached to the phosphorus.

7. A lubricant comprising a mineral lubricating oil and. an amount suflicient to impart extreme pressure properties of a mono ester combining phenyl tritertiary 'carbinol with phosphorus trlchloride, said ester containing two atoms of chlorine attached to the phosphorus.

' 8. A lubricant comprising a. mineral lubricating oil and an amount suflicient to impart extreme pressure propertiesoi a mono ester combining butyl phenyl tritertiary thiocarbinol with phosphorus trichloride, said ester containing two atoms of chlorine attached to the phosphorus.

NORMAN E. PEERY.