US2440991A - Oil compound - Google Patents

Description

Patented May 4, 1948 OIL COMPOUND Stephen J. Wayo, Whiting, Ind., assignor to Sinclair corporation of Maine No Drawing. Application June 8, 1945, Serial No. 598,416

8 Claims. 1

This invention relates to improved mineral oil compositions. It relates more particularly to mineral oil compositions, especially adapted for use as turbine oils, and consisting principally of a petroleum lubricating oil fraction, the characteristics of the oil being modified by the addition thereto of a relatively small proportion of an alpha, alpha-thiocarbono-dialiphatic acid. The compositions of my present invention, when used as turbine oils, have been found to be particularly effective in inhibiting the rusting of metal parts exposed thereto.

I have discovered that the alpha, alpha'-trior dithiocarbono-dialiphatic acids, of which the aliphatic acid radicals are those of stearic acid or palmitic acid, are partiularly effective rust inhibitors when compounded with a turbine oil.

The alpha, alpha-thiocarbono-dialiphatic acid addends of my present invention may be represented by the following structural formula:

on, on, em), 011,)...

where X represents either oxygen or sulfur, and m represents one of the integers 13 and 15.

A lubricating oil composition to be used as a turbine oil, and especially in modern marine steam turbines, is subject to very exacting requirements. Not only must it perform the ordinary function of lubricating the turbine over prolonged periods without interruption, but usually it must serve as a coolant, to lubricate the gearing mechanism and to operate oil-actuated governers or control mechanisms having very nice tolerances and lubricate other auxiliary equipment.

Many lubricating oil compositions highly satisfactory for the lubrication of other mechanisms have been found to be wholly unsuitable for use as a turbine oil. This is probably due primarily to the fact that in normal use turbine oils rapidly become contaminated with water. Whatever the cause, it is generally recognized that the performance of a turbine oil is not predictable from conventional tests applicable to other oil lubri cants.

Essential characteristics of a satisfactory modern turbine oil include, in addition to ordinary lubricating requirements, extraordinary resistance to emulsification in the presence of water, and the avoidance of the rusting of metal parts within the oil system of the turbine, and auxiliary apparatus, under operating conditions.

Refining Company, New York, N. Y., a

The use of many lubricating oil compositions, otherwise satisfactory as turbine oils, has resulted in'the rusting of metal parts within the oil system with consequent serious interference with the operation ofthe turbine, including oil-actuated governors and other parts, depending upon close tolerances. The results of such rusting not only interfere with the operation of and tend to clog the delicate clearances of the 011 system, but the products of the rusting appear to catalyze oxidation of the oil with resultant sludge formation, which may further aggravate such conditions. The products of the rusting also appear to act as emulsifying agents.

In marine turbine operation, the exacting conditions under which the turbine oil must function satisfactorily are frequently further aggravated by the contamination of the oil with salt water, for instance sea water, which has been found incompatible with many of the corrosion inhibitors previously found suitable as addends for ordinary lubricants. To meet modern turbine oil specifications, particularly Navy specifications, the oil composition must satisfactorily pass tests involving its contamination with salt water.

The unique requirements of a turbine oil have resulted in the formation of special test methods for determination of the characteristics of the oil with respect to rusting. The result of rusting tests, hereinafter noted, were obtained in accordance with the method prescribed by the American Society of Testing Materials, procedure A. S. T. M. specification D665-42T, and designated Rust-preventing characteristics of steam turbine oil in the presence of water.

In the rusting tests, results of which are reported herein, a salt solution was used, as indicated, instead of distilled water prescribed by the test, said salt solution being prepared in accordance with the following Navy formula for synthetic sea water, the proportions being per liter of distilled water:

Grams NaCl 25.0 MgClzfiHzO 11.0 CaClz 1.2 NazSO4 "410 Test conditions when the salt water is substituted for distilled water are much more severe than when distilled water is used in the test, and oil compositions capable of withstanding such conditions have been found suitable for either land turbine or marine turbine use.

As previously indicated, a further essential characteristic of turbine oils is that they do not form objectionable emulsions under conditions of use. Consequently, in the compounding of such oils, it is necessary to avoid the use of addends which might deleteriously affect the emulsibility oftheoil a 1 An acceptable method for determining the emulsifying characteristics of turbine oil is that designated Emulsion test for lubricating oils prescribed by the Federal Standard Stock Catalog, section IV (part 5), Federal Specifica-' tions for Lubricants and liquid Fuels, General specifications (Methods for sampling and test-' The proportion of the addend used in accOrdance with my present invention may vary over a considerable range depending primarily upon the severity of; the conditions under which the oil is to be used. Under salt Water conditionsad vantageous results are obtained, using proportions or the addends within the range of about 0.05% about 0.1%, for instance, DUI-0.08% by weight based onthe mineral oil content. Under less severe conditions, even smaller proportions may be used with advantage. Larger proportions may be used, but are not generally required.

The mineral oil constituent of my improved turbine oils? may with advantage consist of a petroleum lubricating oil fraction or a blend of oils such as ordinarily specified for turbine. oils. It may with advantage be'a highly refined lubricatingoil, for instance an acid treated petroleum lubricating oil fraction, or one which has been subjected to solvent refining, for instance, a phenol treated fraction from East Texas crude. I have with particular advantage, used a solventtreated 420-450 neutral from East Texas crude for this purpose.

My alpha, alpha'-trithiocarbono-. ialiphatic acid addends may be prepared by reacting the sodium salt of an alpha-halo-aliphatic acid, either stearic acid, palmitic acid, or mixtures thereof, in alcoholic solution with disodium trithiocarbonate to form a sodium salt of the corresponding alpha, alpha-trithiocarbono-dialiphatic acid, separating the resultant thiodi-acid salt from the alcoholic solution and acidifying the separated thiodi-acid salt by treatment in aqueous suspension with'a mineral acid, for instance hydrochloric acid, to convert the thiodiacid salt to the free thiodi-acid. The disodium trithiocarbonate used in the production of this addend may be prepared by reacting carbon disulfide with an aqueous suspension of sodium sulfide.

The sodium salt of the alpha-halo-aliphatic acid used is with. advantage prepared from an 'alpha-brominated aliphatic acid, that is stearic acid or palmitic acid, or mixturesthereof, though other alpha-halo-aliphatic acids may be used, for instance alpha-chlorostearic acid or alpha- .ehloropalmitlc acid. The. alpha-bromoaliphatic acid may beprepared by reacting bromine with stearic acid, or palmitic acid, or mixtures thereof, in the presence of red phosphorus.

I have with advantage prepared my alpha, alpha-trithiocarbono-dialiphatic acid addend by the following method: An aqueous solution of disodium trithiocarbonate was first prepared by reacting 5.3, grams of carbon disulfide with a solution of 14.4 grams of crystalline sodium sulfide 4 i115, ca of. aterhen d s.-

'4 solved 36 grams of alpha-bromostearic acid in 100 cc. of 50% ethyl alcohol in a 1-liter Erlenmeyer flask. To this solution I added, with cooling, 5.5 grams of sodium carbonate in cc. of water to form the sodium salt of the bromostearic acid. Therefore I added to the resultant solution "50. ccIof the aqueous: solution of disodium trithiocarbonate, prepared as previously described, and raised the alcohol concentration of the solution to about 70% by the addition of 325. cc. of 95% ethyl alcohol. The mixture was then heated for four hours on a steam bath with refluxing, and then cooled to room temperature to eifectthe completion of the precipitation of the. sodium Scan, The reaction mixture was then filtered and the ,olive green precipitate thus ob- ,tained was suspended in 200 cc. of water in a 1- 'liter separatory funnel and treated with an excess of dilute (1:3) hydrochloric acid. The liberated thiodi-acids were then extracted with 300 cc. of benzene and the benzene extract washed with hot water and allowed to stand. On standing, the mixture separated into an aqueous phase and a benzene phase. The washed benzene phase, which contained thefatty acid reaction product, was then filtered to remove droplets of water and the solvent was evaporated therefrom on a steam bath.

By the foregoing procedure I have produced 23.8 grams of a crude product, found byanalysis to contain 67% of alpha, alpha-t1;ithi0carb,ono, dialiphatic. acid, this being equivalent to 77.5% of the theoretical yield. The crude productv was a clear viscous brown liquid, which slowly solidilied to astifi, Waxy paste.

The fatty acid from which the alpha-bromostearic acid used in'the foregoing operation was made was a commercial, doubleepressed stearic acid having an approximate composition: 45% stearic acid, 45 palmitic acid and 10% oleic acid. When brominated by the process previously noted, the oleic acid appears to be converted to 2, 9, 10 tribromostearic acid and some dibromostearic and dibromopalmitic acid is formed. Before use of the material in the foregoing operation, the impurities were separated from the monoealpha-bromoacids by recrystallization, of the crude mixture from benzene solution.

The resultant mono-bromoacid mixture contained approximately equal parts of alpha,- bromostearic acid and alpha-bromopalmitic acid, and, when reacted with the sodium carbonate and the disodium trithiocarbamate and acidified as previously described, resulted in the formation of a, mixture of alpha, alpha-trithiooarbono=di+ acids apparently consisting of about 25% distearic acid, about 25% dipalmitic acid, and about 50% of a thiodi-acid formed from one moleculeojf stearic acid and one molecule of palmitic acid.

The addendprepared as described was found by analysis to have a; neutralization valu of 170.5

and tccontain 10.50% sulfur and 3.03% bromine.

The ammonium dithiocarbamate used in the production of the addend may be prepared by reacting carbon disulfide with ammoniain cold alcoholic solution.

The sodium salt of the alpha-halo-aliphatic acid may be prepared as previously described.

' I have, for example, prepared the alpha, alphadicarbono-dialiphatic acid addend of my present invention as follows: The ammonium dithiocarbamate was first prepared by heating 16 cc. of concentrated (28%) aqueous ammonium hydroxide solution to a solution of 4.18 grams of carbon disulflde in 265 cc. of 95% ethyl alcohol. 36 grams of alpha-bromostearic acid was then added to 100 cc. of 50% ethyl alcohol in a 1-liter Erlenmeyer flask. This alpha-bromostearic acid was converted to the sodium salt by adding, with slight cooling, 5.4 grams of sodium carbonate in 25 cc. of water. The ammonium di-thiocarbamate solution, prepared as just described, was then added to the mixture in the flask and the composite mixture heated with refluxing on a steam bath for two hours, at the end of which period the alcohol concentration of the mixture was 75%. The mixture was then diluted with 200 cc. of water so as to reduce the alcohol concentration to about 50% and the refluxing was continued for two additional hours.

The reaction mixture was then cooled to room temperature to cause the precipitation of the thiodi-acid salt, and was then filtered. The resultant precipitate was then suspended in 300 cc. of water, acidified with an excess of dilute (1:3) hydrochloric acid and extracted with ether. The extract was washed with water, filtered through paper, and the solvent allowed to evaporate therefrom at room temperature.

By the foregoing procedure 12 grams of a crude product containing 50% of alpha, alpha'-dithiocarbono aliphatic acid was obtained which was equivalent to about 40% of the theoretical yield. The crude product was'a brown, somewhat brittle, waxy solvent, readily soluble in mineral oil.

The alpha-bromostearic acid used in the foregoing operation was prepared from a relatively pure stearic acid consisting of 90% stearic acid, 6% palmitic acid, and 4% oleic acid. Before use in the operation the triand di-bromoacids formed from the oleic acid, as previously noted, were separated from the mono-alpha-bromoacids by recrystallization from benzene solution. The resultant alpha-bromostearic acid used in the foregoing operation was thus purified to 95% or better alpha-bromostearic acid.

The alpha, alpha'-dithiocarbono dialiphatic acid prepared by the process just described was found by analysis to have a neutralization number of 150 and to contain 5.4% sulfur and 0.95% bromine.

The addends herein described are readily soluble in petroleum lubricating oil fractions such as used in turbine oil compositions. No particular precautions are necessary in the compounding of my improved mineral oil compositions. The addends may be added to the base oil or blends of various base oils by conventional methods, and thoroughly dispersed therein by agitation.

My improved lubricating oil composition may be illustrated by the following specific examples:

Examle I 0.075% by weight of my alpha, alpha-trithiocarbonodialiphatic acid added, prepared as previously described herein, was blended with a solvent refined 420-450 neutral, and the blend sub- When subjected to the Navy Emulsion Tests previously identified, the composition was found satisfactory to pass the test using either distilled water or a salt solution.

Example II 0.07% by weight of my alpha, alpha'-dithiocarbonodialiphatic acid addend, prepared as previously described herein, was added to the base oil of Example I. The resulting oil composition was subjected to the previously described rusting test, using sea water, and was found to have a rating of A. There was no rusting above the oil level and no coating or etching of the test strip. Similarly, the oil composition satisfactorily passed the Navy Emulsion Test when run with either distilled water or salt solution.

In the absence of my addends, the base oil used in the foregoing examples was unsuited for use as a turbine oil because of its tendency to cause the rusting of the metal parts and in this respect failed to meet the specifications, herein described.

I claim:

1. An improved mineral oil composition, especially adapted to use as a turbine oil, which comprises a petroleum lubricating oil fraction with which there has been compounded a minor proportion, effective to retard rusting, of an alpha, alpha'-thiocarbono-dialiphatic acid represented by the structural formula:

in which X is from the group sulfur and oxygen and m is one of the integers 13 and 15.

2. The composition of claim 1, in which the proportion of the alpha, alpha'-thiocarbono-dialiphatic acid is within the range of about 0.05% to about 0.1% by weight based on the mineral oil content.

3. The composition of claim 1, in which X represents sulfur.

4. The composition of claim 1, in which X represents oxygen.

5. The composition of claim 1, in which X represents sulfur and 112 represents the integer 15.

6. The composition of claim 1, in which X represents sulfur and 121. represents the integer 13.

7. The composition of claim 1, in which X represents oxygen and 111. represents the integer l5.

8. The composition of claim 1, in which X represents oxygen and m represents the integer 13.

STEPHEN J. WAYO.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,279,688 Larson Apr. 14, 1942 2,337,868 Burwell Dec. 28, 1943 2,369,640 Barnum Feb. 20, 1945 2,371,142 Barnum Mar. 13, 1945 2,371,143 Barnum Mar. 13, 1945 2,371,207 Zublin Mar. 13, 1945