US2073841A - Extreme pressure lubricating compositions - Google Patents

Description

Patented Mar. .16, 1937 Tammi EXTREME ranssnan LnnmcA'rnyG comosrrrons Robert L. Humphreys and Bruce B. Farrington, Berkeley, Calif., assignors to Standard Oil Company of California, San Francisco, Calif., a corporation of Delaware No Drawing. Application December 8, 1934, Serial No. 756,704

15 Claims.

This invention relates to new and useful compositions of matter and to methods of preparing the same. In particular, it relates to the preparation of lubricating compositions, particularly of the'type known generally as extreme pressure lubricantsf, such, for example, as will satisfy the severe requirements demanded in the proper lubrication of hypoid and the like gears, and hearing surfaces, metal cutting tools, and the like, subjected to unusually heavy loads per unit area of bearing surface, and has reference to the incorporation in lubricating compositions of certain derivatives of organic thio acids.

In generaLtheprimary requirement of such an extreme pressure lubricant is that it shall possess high lubricating film strength; preferably it also has low rates of wear and low coeflicients of friction, and it is an object of the present invention to disclose and provide a novel type of lubricating composition which fulfills these requirements. It is a further object of this invention to disclose and provide extreme pressure lubricants that do not suffer a loss or deterioration of high film strength, low rate of wear, or low coefficients of friction in long continued use under severe conditions, and which have no tendency to cause gumming or fouling of the lubricated metal parts or surfaces under such long continued service.

As now known, oneclass of compositions designed for use as "extreme pressure lubricants comprises mineral lubricating oils to which have been added, preferably in oil-soluble form, sufflcient amounts of various active agents discovered to possess the properties of increasing the film strength and/or of decreasingtwear and/or of decreasing coeflicients of friction of the mineral base to which they have been added. Mineral oil lubricants containing added metallic soaps, notably lead soaps, and/or sulfurized fatty acid or fatty oils, such as sulfurized animal or vegetable oils, are examples of such compositions.- Certain of the compositions of this type have thevery serious defects that they tend to cause gumming of the metal parts; certain of them tend toseparate into their constituent parts upon long continued subjection to severe operating conditions.

Another class of compositions designed for such service, comprises mineral lubricating oils, either alone or' in admixture with fatty oils, to which have been added sulfur in elemental or uncombined form. Compositions containing such uncombined sulfur have the serious defects that they cause undue corrosion and wear of the metal parts to be lubricated, or the parts adjacent thereto, such as bushings, etc., which result not only in deterioration of the said metal parts, but lead directly to a short life of the lubricating compositions themselves.

'We have now discovered that the addition of small amounts of organic derivatives of organic thio acids, particularly the esters and anhydrides of organic thio acids, in admixture with hydrocarbon or fatty lubricating oils, provide lubricating compositions which satisfy all of the primary requirements of extreme pressure lubricants, and, in addition, are stable in long continued use, do not separate into their constituent parts and do not tend to form gum, or to foul or corrode metal surfaces.

lhe amounts of the said derivatives of organic thio acids required to be added to hydrocarbon or fatty lubricating oils for the preparation of the compositions of our invention vary somewhat, depending upon the severity of the service for which they are designed, and, to some extent, upon the character of the hydrocarbon or fatty lubricating stock used as a base; these amounts are in all cases small, however, compared with the amounts of active agents of the prior types, and in general vary between about /2 of 1% and about 5% of the oil base, by weight.

The esters and anliydrides of organic thio acids to be added to mineral or fatty lubricating oils in preparing the compositions of this invention correspond to the like derivatives of ordinary carboxylic acids, in which one or more oxygen atoms are replaced by sulfur atoms. They may thus correspond to any one of the following type formulae:

organic radical, whether allsvl, aryl or aralkyl, as well as the following:

'in which anhydrides of thio acids R and R likewise represent any organic radical, whether alkyl, aryl or aralkyl.

It will thus be apparent from a consideration of the above type formulae that the aryl, alkyl and aralkyl esters of the aliphatic thio fatty acids,

such as thio acetic acids, thio valeric acid, thio oleic acid, and the thio naphthenic acids, and the thio carboxylic acids, as well as the anhydrides of these said type thio acids, are contemplated to be added to mineral'or fatty lubricating oils in preparing therefrom extreme pressure lubricating compositions in accordance with our invention.

These compounds are generally oil soluble to the extent required in the practice of our invention,

and they are likewise generally stable to heat at temperatures of 300 F. or above.

As typical of the results accomplished by the addition of the said derivatives of organic thio acids to lubricating oils, reference is made to the accompanying tabulation, in which three distinct types of sulfur linkage are represented, exempli-r fying each of the types of sulfur linkage referred to hereinabove and found to be operative to markedly increase the film strength of the lubricating compositions in which they are caused to be present.

In the respective columns in the above tabulation there are set out: First, typical derivatives of thio acids, representative of a great number which may suitably be used in the practice of our invention; second, the type formula of the said thio acid derivatives, particularly setting out the sulfur linkage therein; third, the amount of combined sulfur in each of the said thio acid derivatives, in percentage by weight; fourth, the amount of each of the thio acid derivatives added to a mineral hydrocarbon lubricating oil base batch (kept uniform in amount here only for the purposes of exemplification); fifth, the amount of sulfur in each of the finished extreme pressure lubricants, in percentage by weight; sixth, the

film strength of the finished lubricating compositions, as measured on the Timken machine described by O. L. Maag in the National Petroleum News for November 16, 1932, page 53, article entitled Extreme pressure lubricants, wherein the O. K. load i Pounds, or the load carrying capacity of the lubricant, is directly measured. In the above exemplifying tabulation the same mineral oil stock was used throughout.

In the preparation of the compositions of our invention, the desired thio acid derivative or mixture of thio acid derivatives, in suitable amounts, is admixed with a hydrocarbon or fatty mineral oil and the admixture merely agitated mechanicallyin ordertoobtain completeand homogeneous solution. We have found in general that the organic esters and the "anhydrides of the organic thio acids are easily soluble in hydrocarbon and fatty oils to the extent required, and that no difliculty is encountered in incorporating them therein.

A particular feature of our invention lies in the preparation of bases or concentrates containing relatively large amounts of thio acid derivatives in admixture with hydrocarbon or fatty oils. Such concentrates may be stored or transported in this form and before actual use in extreme pressure lubrication service may be diluted with the same or other lubricating oil to any desired agents in suspended form, however, is sufficientto allow these esters and anhydrides" of the organic thio acids to function in decreasing film strength in actual use. 4

Obviously the character and viscosity of the lubricating oil in which the thio acid derivatives are added will be dependent to some extent upon the character of service to which the composition is ultimately to be put, and we are not to be limited in the character of the lubricating composition used as a base in the preparation of our compositions. For example, we have found that the life of metal cutting tools is very remarkably lengthened by the incorporation of small amounts of esters of organic thio acids and of anhydrides of organic thio acids in either the mineral hydro-, carbon or fatty oils used ordinarily in this service.

Moreover, we have prepared miscible metal cut- .ting oils in which the usual oil component is replaced with an oil containing small amounts of these thio acid derivatives in solution and have found that the life of the cutting tools is greatly lengthened and the character of the metal surfaces cut much improved, especially in severe cutting service. Further, semi-solid and solid lubricating greases may be prepared, in the usual manner, wherein small amounts of these thio acid derivatives may be incorporated in the hydrocarbon and fatty oils-ordinarily used therein; the lubricating film strength is in all cases increased to a degree comparable to the increases pointed out in the example tabulated above.

While we have described in detail the character of our invention and given numerous illustrative examples of the preparation and application of the compositions of our invention, we have done so by way of illustration and with the intention that no limitation should be imposed upon the invention thereby. It will be obvious to those skilledin the art that numerous modifications and variations of the above illustrative examples may be effected in the practice of our invention, which is of the scope of the claims appended hereto.

We claim:

1. A composition of matter comprising an admixture of a lubricating oil and an organic derivative of an organic thio acid.

2. A composition of matter comprising an admixture of a lubricating oil and a compound of the class consisting of the types in which at least one oxygen atom is replaced by a sulfur atom, and in which R and R represent any alkyl, aryl or aralkyl radical.

3. Acomposition of matter comprising an admixture of a hydrocarbon lubricating oil and an organicderivative of an organic thio acid.

4. A composition of matter comprising an admixture of a hydra arbon lubricating oil and an organic ester of an organic thio acid.

5. A composition of matter comprising an admixture of a hydrocarbon lubricating oil and an "anhydridef of an organic thio acid.

6. A composition of matter comprising a lubricatlng oil containing between about 0.5 and about 5.0 per cent by weight of an organic derivative of an organic thio acid.

7. A lubricating composition containing a lubricating oil and an ethyl thio benzoate.

8. A lubricating composition containing a. lubricatingoil and benzyl thiobenzoate.

9. An extreme pressure lubricant base comprising an oil and an organic derivative of a thio acid, capable of dilution with a lubricating oil to produce an extreme pressure lubricant containing between about 0.5 and about 5.0 per cent by weight of the said thio acid derivative.

10. An extreme pressure lubricant base containing 50 or more per cent by weight of an organic derivative of a thio acid in admixture with an oil.

11. A composition of matter consisting of a hydrocarbon lubricating oil and a compound of the class consisting of the types-- in which at least one oxygen atom is replaced by 12. A composition of matter consisting of a hydrocarbon lubricating oil containing between about 0.5 and about 5.0 per cent by weight of a compound of the class consisting of the types 6 I? u R-OO-R and RCOC-R in which one or more oxygen atoms are replaced by sulfur atoms, and in which R. and R represent any alkyl, aryl or aralkyl radicals.

13. A lubricating composition comprising a lubricating oil containing between about 0.5 and about 5.0 per cent by weight of an ethyl thio benzoate.

14. A lubricating composition comprising a lubricating oil containing between about 0.5 and about 5.0 per cent by weight of a benzyl thio benzoate.

15. An extreme pressure lubricant base comprising an oil containing an. organic ester of an organic thioacid, capable of dilution with a lubricating oil to produce an extreme pressure lubricant containing between about 0.5 and about- '5.0'per cent by weight-of the said organic ester of the said organic thioacid.

ROBERT 1.. HUMPHREYS. BRUCE B. FARRINGTON.