US2276162A - Stabilized mineral oil - Google Patents

Description

Patented Mar. 10, 1942 UNIED S ATES PATEN OFFICE STABILIZED MINERAL OIL Philip Gordon Colin, Westfield, N. J., assignor to Tide Water Associated Oil Company, Bayonne, N. J., a corporation of Delaware 3 Claims.

This invention relates to the stabilization of lubricants; and, more particularly, is concerned with mineral hydrocarbon lubricating and like oils having incorporated therewith substances or compounds efiective to inhibit or retard deterioration in service.

The useful service life of mineral oils, in respect both of the character and rapidity of deterioration, is influenced by the service conditions obtaining during use. In some instances,,as in the lubrication of internal combustion engines, high temperatures prevail and thin films of the oil are in continued and renewed contact with hot metal surfaces. Strongly oxidizing atmospheres may be encountered in other services where operating temperatures are the same or may be lower. In the lubrication of steam turbines, the oil temperature is relatively low but contacted metal surfaces or other operating conditions may catalyze, promote or permit acid or sludge formation with eventual emulsification due to the presence of water. For transformer, cable wrapping or other electrical services, the foregoing or other factors may tend to occasion deterioration.

Petroleum hydrocarbon oils may be improved in some respects by refining methods effective to remove or convert, at least in part, certain deterioration inducing constituents normally present therein. Refining with chemicals frequently is employed, as by extraction with selective solvents of the character of phenol, liquid sulfur dioxide, nitro-benzine, furfural, and others well known in the art as well as combinations thereof, by clay filtration, or by moderate treatment with sulfuric acid of less than fuming acid strength. More drastic refining, as by treatment with fuming sulfuric acid, may be resorted to when it is desired to produce high refined viscous hydrocarbon oils (the so-called technical white oils) from which substantially all asphaltic constituents have been removed. The refined products, however, still are to an undesirable degree susceptible to oxidation, polymerization, or other chemical phenomena to which may be attributed observed impairment of the oil resulting from or indicated therewith of substances or compounds having an.

inhibiting or retarding action in one or another respect upon the deterioration of the oil. Many suggestions heretofore have been made in this direction and a number of compounds advanced for trial as inhibitors some of which in greater or less degree have proved effective. Discrepancies in results have been noted, however, both as to the relative inhibiting effect of a given compound with different oils in overcoming a particular undesired result, and as to the eifectiveness of a given inhibitor in preventing difierent undesired results flowing from the same or different service uses of a given oil. Analogy between different petroleum products and the efiective inhibiting action of various compounds therein does not seem to exist in suflicient degree to provide a reliable basis for predicting the value of an inhibitor in one oil environment from its efiect in another. Thus, many compounds efiective as anti-gum forming agents for cracked gasoline may be wholly without effect in petroleum lubricating oils. Again, certain inhibitors of value in preventing deterioration of very highly refined turbine oils (the so-rcalled technical white oils) have proved quite ineffective in respect of inhibiting action in less highly refined turbine oils.

The action of inhibitors, particularly in mineral hydrocarbon oil environments, appears, therefore, to be in a sense specific not only for certain reactions but further with respect to the character of the oil, the nature and extent of the refining to which it has been subjected, and the service for which it is intended. The present invention is concerned with and provides a compound of proven inhibiting action; but it is deemed undesirable and of little practical value to attempt or rely upon any prescribed theory in explanation of observed eifects or results.

In its broad aspect, the present invention relates to the use of an inhibitor which I have discovered to be of marked utility in preventing the deterioration of viscous or relatively viscous petroleum oils (as contrasted with the less viscous or non-viscous distillate petroleum products such as gasoline and kerosene).

More specifically, an important object of the invention is to provide an effective inhibitor for lubricating and like oils of petroleum origin; which oils have been subjected in greater or less degree to conventional methods of refining other than drastic treatment of the character resorted to for the production of water white viscous mineral oils (viz: technical white oils as prepared by extended treatment with heavy fuming sulfuric acid).

A further object of the invention is to provide, for the indicated use, an inhibitor compnsing dialpha. naphthylamine. It is likewise an object of the invention to improve, and to provide improved, lubricating oils by incorporating therewith small amounts of di-alpha naphthylamine.

Other objects and advantages will appear from the following description of the invention and the illustrative examples presented hereinafter in order that the invention may be more particularly ascertained.

Various tests have been devised and are available by which a comparative evaluation of oils with respect to deterioration thereof in service may be obtained in a relatively short period of time. Some of these tests are of longer duration than others, but have the advantage of affording a, perhaps more reliable laboratory criterion by which to judge the relative value of various inhibitors than extremely accelerated tests.

One such relatively prolonged test, which has proved of particular convenience in, although not limited to, the evaluation of oils intended for such service as the lubrication of steam turbines, is the familiar Funk test. In this test, a measured quantity of oil and water (ordinarily 8 gallons of oil and 0.8 gallon of distilled water) is continuously circulated through a cast iron chamber under conditions of violent. agitation, the oil being maintained at a temperature of 200 F. and air being passed continuously through the oil asit circulates and re-circulates through the chamber. The length of time required to form 1% (by volume) of sludge and emulsion as measured in a centrifuged sample is the criterion by which the relative service life of the oil is measured.

Di-alpha naphthylamine is a compound con-' forming to the structural formula:

and may be prepared, for example, by reacting Funk machine as an evaluating means, clearly demonstrate the efficacy of di-alpha naphthylamine as an inhibitor of deterioration in viscous mineral hydrocarbon oils. The runs were made with a turbine oil, produced from an East Texas crude petroleum, which oil had been refined by solvent extraction with liquid sulfur dioxide and had a viscosity at 100 F. of 150 Saybolt seconds.

Time to form Inhibitor 1% sludge and emulsion Hours None 50 0.05% di-alpha naphthylamine 2100+* *No evidence of sludge and emulsion formation at 2100 hours.

A particular advantage of the inhibitor according to the invention resides in the extremely small proportions necessary to efiect very substantial inhibiting or stabilizing of the oil in respect of deterioration thereof. This is aptly demonstrated by the foregong data wherein 0,05% or di=alpha naphthylamine is shown to occasion a remarkable increase in the Funk life of the oil in question. It will be understood, of course, that larger or smaller proportions of inhibitor may be used as deemed desired, but in general it is contemplated that the practice of the invention will entail the use of amounts of the order of less than 1% and, in the interests of economy, less than 0.1%. My investigations indicate that the potency of this inhibitor is such that proportions in the range of 0.005% to 0.05% will in many cases be entirely satisfactory.

The compound which I have discovered to be of value as an inhibitor for lubricating and like petroleum oils is readily soluble in the oil in proportions well in excess of the range indicated above as giving effective stabilizing action. The invention may be practiced, therefore, either by the direct addition of inhibitor to oil'in the desired inhibiting proporton or, as mayin many instances be preferable, by preparing a more concentrated solution of inhibitor in oil andthen adding a suitable amount of such concentrate to bulk quantities of oil.

The use of di-alph naphthylamine as an inhibitor according to the invention is not confined to the specific oil designated in the foregoing example. Other mineral hydrocarbon oils of lubricating oil character may be stabilized against deterioration by the incorporation therewith of this inhibiting compound. Thus, the inhibitor of the invention may be applied to the stabilization of oils having greater or less viscosity than 150 seconds Saybolt at F.; and to such oils as refined by various methods alternativeto extraction with liquid sulfur dioxide. However, the use of this inhibitor in technical white oils derived from petroleum as by drastic refining with fuming sulfuric acid forms no part of the present invention; nor does the present tain other services where the deterioration in question primarily is one caused by the oil rather than of the oil itself. A particular example of this has been noted in connection with studies of the effect of various mineral hydrocarbon lubricating oils upon the corrosive deterioration of certain hard bearing alloys such as cadmium-silver, cadmium-nickel and copper-lead, now frequently employed in automotive services in lieu of the softer Babbitt bearings.

One difliculty which arose early in the use of these new type bearings was the very rapid corrosion thereof by many lubricating oils; and one method of retarding or preventing such corrosion is to incorporate suitable inhibitors in the motor oil.

In the hope that the very unusual inhibiting action of di-alpha naphthylamine in turbine oil and like service was an indication that this compound likewise would be of value as a bearing corrision inhibitor, tests were made using cadmium-silver, cadmium-nickel and copper-lead bearings. The results, however, were quite negative, no measurable improvement or degree of bearing corrosion inhibition being produced.

It would appear, therefore,that the compound comprising the inhibitor of the present invention, While remarkably effective in preventing the serv- 'ice deterioration of certain viscous hydrocarbon oils, is clearly specific in its action.

This application is a substitute for my application Serial No. 137,012, filed April 15, 1937, and now abandoned.

I claim:

1. Mineral oil composition comprising'a viscous hydrocarbon oil normally tending to deteriorate