US3533943A - Lubricant compositions - Google Patents

Description

United States Patent O 3,533,943 LUBRICANT COMPOSITIONS Andreas G. Papayannopoulos, Woodbury, N.J., now by judicial change of name Andrew George Papay, assignor to Mobil Oil Corporation, a corporation of New York No Drawing. Filed Nov. 10, 1966, Ser. No. 593,294 Int. Cl. (110m 1/38, 1/48 US. Cl. 252-325 2 Claims ABSTRACT OF THE DISCLOSURE Lubricant compositions, which normally corrode metal surfaces, are provided, containing a small amount sufficient to inhibit corrosion, of a mixture of a salt of a dialkyl dithiophosphoric acid and a 2,5-bis(alkyldithio)- 1,3,4-thiadiazole.

This invention relates to improved organic compositions and, in one of its aspects, relates more particularly to improved organic compositions in the form of liquid and solid hydrocarbon-containing materials which normally tend to react with and corrode metal surfaces under conditions of use. Still more particularly, in this aspect, the invention relates to improved organic compositions in the form of lubricating oils and greases which, in their uninhibited state, tend to react with and corrode metal surfaces with which they may come into contact in performing their intended function.

It is well known that lubricating oils, and greases containing such oils as lubricating vehicles, cause wear of metal surfaces under conditions of use as, for example, in functioning as lubricants in internal combustion engines and as lubricants for various types of mechanical elements in which the lubricants are employed, for example, as gear oils, cutting oils and other forms of lubricating media. More specifically, products which are formed in the oil are acidic in nature and exert a deteriorative of feet on metal parts with which the oils or grease may come into contact. Furthermore, when employed in the form of lubricating oils, such products may produce formations of varnish and sludge on metal surfaces, thus lowering the operating efficiency as, for example, when employed in the form of engine oils. Similarly, it is known that solid lubricants in the form of greases tend to have their lubricating properties impaired under the stress of environmental use and thus may be ineffective with respect to exhibiting good antiwear properties.

It is, therefore, an object of the present invention to provide organic compositions having improved anti-corrosion properties.

Another object of the invention is to provide improved organic compositions in the form of liquid and solid hydrocarbon-containing materials as lubricants containing additives adapted to prevent the aforementioned wear and deterioration of metallic surfaces.

Still another object of the invention is to provide effective corrosion-inhibiting additives for incorporation into the aforementioned organic compositions.

Other objects and advantages inherent in the invention will become apparent to those skilled in the art from the following detailed description.

It has now been found that the aforementioned corrosive properties of organic compositions, particularly in the form of liquid and solid lubricants, can be effectively overcome by incorporating therein small amounts, sufficient to inhibit such corrosion, of a synergistic mixture of a salt of dialkyl dithiophosphoric acid and a thiadiazole. In general, the present invention, in its preferred apfit "ice

plications, contemplates organic compositions which normally cause corrosion of metal surfaces and which contain a small amount of the aforementioned synergistic mixture as an anticorrosion agent, usually from about .01 percent to about 20 percent, and preferably from about .01 percent to about 2 percent, by weight, of the total weight of such composition. Insofar as the additive synergistic mixture, itself, is concerned, the salt of the dialkyl dithiophosphoric acid and the thiadiazole, described above, may be individually present in an amount from about 20 percent to about percent, by weight, of the total weight of the mixture.

A field of specific applicability is the improvement of liquid hydrocarbons employed as lubricants, including any of the conventional hydrocarbon oils of lubricating viscosities. These may include mineral or synthetic lubricating oils, aliphatic phosphates, esters and diesters, silicates, siloxanes, oxalkyl ethers, or esters. Mineral lubricating oils employed as the lubricating composition may be of any suitable lubricating viscosity and may range from about 45 SSU to about 6,000 SSU at 100 F., and preferably from about 50 SSU to about 250 SSU at 210 F. These may have viscosity indexes from below 0 to about 100 or higher. Viscosity indexes from about 70 to about are preferred. The average molecular weights of these oils may be, for example, from about 250 to about 800.

As previously indicated, the aforementioned synergistic additive mixtures may also be incorporated as anticorrosion and antioxidative agents in grease compositions. Such greases may comprise a combination of a wide variety of lubricating vehicles and thickening or gelling agents. Thus, greases in which the aforementioned additive mixtures are particularly effective may comprise any of the aforementioned conventional hydrocarbon oils of lubricating vis cosity as the oil vehicle, and may include any of the aforementioned mineral or synthetic lubricating oils of the type indicated.

With respect to the formation of improved grease compositions in which the aforementioned additive mixtures are to be incorporated, the choice of employing a mineral or a synthetic oil of lubricating viscosity can best be determined from the nature of the intended environmental use for the grease. Thus, when high temperature stability is not a requirement of the finished grease, mineral oils having a viscosity of at least 40 SSU at F., and particularly those falling within the range from about 60 SSU to about 6,000 SSU at 100 F. may be effectively employed. In instances where synthetic vehicles are employed rather than mineral oils, or in combination therewith as the lubricating vehicle, various compounds of this type may be successfully utilized. Typical synthetic vehicles include: polypropylene, polypropylene glycol, trirnethylol propane esters, neopentyl and pentaerythitol esters, di-(-ethyl hexyl) sebacate, di-(Z-ethyl hexyl) adipate,

di-butyl phthalate, fluorocarbons, silicate esters, silanes, esters of phosphorus-containing acids, liquid ureas, ferrocene derivatives, hydrogenated mineral oils, chain-type polyphenyls, siloxanes and silicones (poly-siloxanes), alkyl-substituted diphenyl ethers exemplified by a butylsubstituted bis(p-phenoxy phenyl) ether, phenoxy phenyl ethers, etc.

The lubricating vehicles of the aforementioned improved greases of the present invention containing the above-described additive mixtures are combined with a grease-forming quantity of a thickening agent. For this purpose, a wide variety of materials may be employed. These thickening or gelling agents may include any of the conventional metal salts or soaps which are dispersed in the lubricating vehicle in grease-forming quantities in such degree as to impart to the resulting grease composition the desired consistency. Other thickening agents that may be employed in the grease formulation may comprise nonsoap thickeners, such as surface-modified clays and silicas, aryl ureas, calcium complexes and various other materials. In general, grease thickeners may be employed which do not tend to melt and dissolve when used at the required temperature within a particular environment; however, in all other respects, any material which is normally employed for thickening or gelling hydrocarbon fluids for forming greases, can be used in preparing the aforementioned improved greases in accordance with the present invention.

The salt of the dialkyl dithiophosphoric acid present in the synergistic mixtures of the present invention may be employed either in the form of any metal salt or in the form of any amine salt of the dialkyl dithiophosphoric acid. Preferably, metal salts of dialkyl dithiophosphoric acids are employed in which the metal may, for example, comprise zinc, calcium, barium, lead, magnesium, nickel, sodium, potassium, lithium, copper, cadmium, aluminum, cobalt, manganese, iron, tin, mercury or antimony. Metal salts of dialkyl dithiophosphoric acids in which the metal element is a metal of Groups I and II of the Periodic Chart of the Elements are found to produce the most desirable results. When the salt of the dialkyl dithiophosphoric acid is present in the synergistic mixture in the form of the amine salt, the amino group preferably contains from about 1 to about 25 carbon atoms. In this respect, amine salts of dialkyl dithiophosphoric acids in which the amino group contains from about 8 to about 18 carbon atoms have been found to produce the most desirable results. Thus, the amine salt may contain, for ex ample, any amino group derived from paraffinic or arotioned salts of dialkyl dithiophosphoric acids and thiadiazoles. In this respect, it is found that although each of the aforementioned components is individually effective in inhibiting corrosion and deterioration of metal surfaces when employed in organic compositions, nevertheless, when employed in admixture, a pronounced effect is obtained in which'the efficacy of each of the components, viz, the aforementioned salt and the thiadiazole, is pronouncedly more than merely additive. This synergistic effect is observed with any ratio of the aforementioned salt and thiadiazole components being present in combination. The following examples will serve to illustrate this synergistic effect of the aforementioned components in additive mixtures present in the novel organic compositions of the present invention in inhibiting corrosion of metal surfaces, particularly with respect to lubricant compositions.

In accordance with the data of the examples of the following Table I, a series of comparative corrosion tests was carried out for the purpose of demonstrating the aforementioned synergistic corrosion-inhibiting effect realized in employing mixtures of the aforementioned salts of the dialkyl dithiophosphoric acids and the thiadiazole. The test employed for this purpose was a standard ASTM Test D130 which, in general, comprises immersing a copper strip in the material to be tested for a period of 3 hours and maintained therein at a temperature of 250 F. Since sulfur-containing materials are known to be highly corrosive to copper, an SAE 90 base lubricating oil containing sulfurized polyisobutylene (having a sulfur content of 57 percent, by weight, and a saponification number of 80) was employed as a blank. This SAE 90 base oil comprised, by weight, about 70 percent bright stock (150 SSU at 210 F.) and about percent paraffinic stock (200 SSU at 100 F.).

Additive Wt. percent in SAE 90 Base Oil Suliurizcd polyisobutylene 2,5-bis(t-0ctyl dithio) 1,3,4-tliiadiazolo 0. 2 Oleyi amine salt of diisopropyl dithiophosphoric acid--. Zinc salt of diisohcxyl dithiophosphoric acid Oetyl acid phosphate Copper corrosion rating (3 hours at 250 F.)

matic hydrocarbons, either substituted or unsubstituted. Thus, amine salts of the dialkyl dithiophosphoric acids may be employed in which the amino group is derived from an octylamine, dodecylamine, oleylamine, and may preferably be derived either in the form of a primary or secondary amine. A particularly outstanding metal salt of the dialkyl dithiophosphoric acids is the zinc salt of diisohexyl dithiophosphoric acid. An outstanding amine salt of the dithiophosphoric acids is the oleyl amine salt of diisopropyl dithiophosphoric acid.

The thiadiazole component of the novel'synergistic mixtures of the present invention may comprise any commercially available thiadiazole. Representative thereof are the 2,5 bis(alkyldithio) 1,3,4 thiadiazoles and the 2,5 bis(N,N dialkyl thiocarbamyl) 1,3,4-thiadiazoles. Specific preferred examples of the thiadiazoles employed in the synergistic mixtures of the present invention include 2(n dodecyldithio) benzothiazole, 2(n hexyldithio) benzothiazole, 2(n dodecyldithio) benzoxazole, 2(n dodecyldithio) benzimidazole, 2,5 bis(ndodecyldithio) 1,3,4 thiadiazole, 2,5-bis(t-octyldithio)- 1,3,4 thiadiazole, and 2,5 bis(N,N-diethyldithiocarbamyl)-1,3,4-thiadiazole.

As previously indicated, the novel synergistic mixtures employed in the organic compositions in accordance with the present invention comprise mixtures of the aforemen- As will be seen from the data of the examples of the foregoing Table I, the sulfurized polyisobutylene-containing oil is highly corrosive to copper with a rating of 3B (Example 1). No perceptible improvement is realized when a thiadiazole (Example 2) is present; or when a salt of a dialkyl dithiophosphoric acid is present (Examples 3 and 4). On the other hand, when a mixture of the thiadiazole and the aforementioned salts is present in the oil, a Significant synergistic effect is obtained (Examples 5 and 6) with an improved rating of 1B.

Table I (Examples 7 through 12) further demonstrates that the addition of an acidifying agent (octyl acid phosphate) to render the base oil even more corrosive, still results in obtaining a significant synergistic corrosionin hibiting effect when the thiadiazole and salts of the dialkyl dithiophosphoric acids are employed in combination. In this respect, an improvement in rating from 4A (Examples 7 through 10) to 2A (Examples 11 and 12) is achieved.

In Table II, the aforementioned synergistic effect is again apparent when employing a different sulfurized polyisobutylene from that employed in the data disclosed in Table I. In the data of the examples shown in Table II, an SAE base lubricating oil containing sulfurized polyisobutylene (having a sulfur content of 46 percent, by weight, and a saponification number of 30) was employed as a blank. This SAE 90 base oil contained the same agent (octyl acid phosphate) to render the base oil even bright stock and parafiinic stock components as the base more corrosive, still results in obtaining a significant syn- 011 disclosed in the data of the examples of Table I. ergistic corrosion-inhibiting effect when the thiadiazole TABLE II Example Additive Wt. percent in SAE 90 Base Oil 1 2 3 4 5 6 7 8 9 10 11 12 Sulfurized polyisobutylene 4. 4 4. 4 4.4 4.4 4 4 4 4 4 4 2,5-bis(t-octyl dithio) 1,3,4-thiadiazole 0.2 0.1 .1 0.1 Oleyl amine salt of diisopropyl dithiophosphor ac 0. 3 0. 1 0.2 0. 1 Zinc salt of di-isohexyl dithiophosphoric acidnu 0 2 0. 1 0.2 0. 1 Octyl acid phosphate 0.2 0.2 0.2 0.2 0.2 0.2 Copper corrosion rating (3 hours at 250 F.) 2A 20 2C 113 1B 48 2E 3B 4A 2A 2A As Will be seen from the data of the examples of the and salts of the dialkyl dithiophosphoric acids are emforegoing Table II, the sulfurized polyisobutylene-conployed in combination. In this respect, an improvement taining oil is corrosive to copper when subjected to the in rating from 4C, 313, 4C and 4B (Examples 7, 8, 9 and aforementioned standard ASTM Test Dl30 with a 10, respectively) to 2A (Example 11) is achieved. rating of 2C (Example 1). A slight improvement is re 20 It will be understood, moreover, that the improved alized when the thiadiazole (Example 2) is present. No organic compositions of the present invention may, if so perceptible improvement is realized when the salt of the desired, contain various other additives or mixtures of dialkyl dithiophosphoric acid is present (Examples 3 and such additional additives in order to further enhance their 4). On the other hand, when a mixture of the thiadiazole properties. Thus, the organic compositions of the present and the aforementioned salts is present in the oil, a siginvention may contain such additives as extreme pressure nificant synergistic effect is obtained (Examples 5 and 6) agents, antioxidants, antifoamants, detergents, dispersants with an improved rating of 1B. and the like. It will also be understood that although the Table II (Examples 7 through 12) further demonstrates present invention has been described with preferred emthat the addition of the aforementioned acidifying agent bodiments, various modifications and adaptations thereof (octyl acid phosphate) to render the base oil even more may be resorted to without departing from the spirit and corrosive, Still results in Obtaining a Significant y scope of the invention as those skilled in the art will gistic corrosive-inhibiting effect when the thiadiazole readily understand. and salts of the dialkyl dithiophosphoric acids are em- I claim:

ggy zg g g s ZE an g 1. A lubricant composition containing corrosion-inhibsg Egg to g les 11 ggg f i gg iting synergistic proportions of 2,5-bis(t-octyl dithio) i Table the aforemenliioned S neroisfic efiect 1,3,4-thiadiazole and a salt selected from the group cony sisting of the oleyl amine salt of di-isopropyl dithiophosagain apparent when employing still another sulfur-containing material. In the data of the examples shown in f and the Zmc salt of dx'lsohexyl dnhlophos' 40 phone acid.

Table III, an SAE 90 base lubricating oil containing ditertiary butyl trisulfide (containing approximately 25 Synerglstlc mlxture of 3 dlthlo) 1,3,4-thiadiazole and a salt selected from the group conpercent, by weight, ditertiary butyl tetrasulfide) was employed as a blank. This SAE 90 base oil contained the slstlllg 0f the oleyl amlne Salt of p py dIthIOPhOS- same bright stock and paraifinic stock components as the phoric acid and the zinc salt of di-isohexyl dithiophosbase oil desclosed in the data of the examples of Table I phoric acid. and Table II.

TABLE III Example AdditiveWt. percent in SAE 90 Base Oil 1 2 3 4 5 6 7 8 9 l0 l1 g iiilitiicth iitiiifii ilihnaaaan:311111111111111111111;iftit ff '1 i Oleyl amine salt of diisopropyl dithiophosphoric acid Zinc salt of di-isohexyl dithiophosphoric acid. Octyl acid phosphate Copper corrosion rating (3 hours at 250 F.)

. 0. 1 0. 2 O. 2 0. 2 0. 2 0. 2 4B 4B 4B 4B 113 2A 4C 313 40 4B 2A As will be seen from the data of the examples of the References Cited foregoing Table III, the ditertiary butyl trisulfide-contain- UNITED STATES PATENTS ing oil is highly corrosive to copper when subjected to the aforementioned standard ASTM Test D-l30 with a ratkggg g ing of 4B (Example 1). No perceptible improvement is 2719126 9/1955 Fields 252 47 realized when the thiadiazole (Example 2) or when the 2:719827 10/1955 Lowe 252 47 salts of the dialkyl dithiophosphoric acids are present 3,103,492 9/1963 Dinsmore et aL (Examples 3 and 4). On the other hand, when a mixture 3,318,808 5/1967 Plemich et aL of the thiadiazole and the aforementioned salts is present in the oil, a significant synergistic effect is obtained (Ex- PATRICK P. GARVIN, Primary Examiner amples 5 and 6) with an improved rating of 1B and 2A, L VAUGHN Assistant Examiner respectively.

Table III (Examples 7 through 11) further demons CL strates that the addition of the aforementioned acidifying 252 .47, 389

po-wso (5/69) UNITED STATES PATENT OFFICE Patent No 3, 533, 9 1-3 Dated October li lfijO Inventor(s) ANDREW GEORGE PAPAY It is certified that error appears in the above-identified patent and that: said Letters Patent are hereby corrected as shown below:

Column L line 30:

Table I, under Example 12 Table I, under Example 12 Table II, third compound Table II, under Example 3 Column 5, line 45:

;SEA.L) 1mm:

EdmrdMFlewbcnIr.

LAwsstingOffioer for "57" read r7- f'or kl" read -4. L-

for "0.4" read O.l-

for "dithiophosphoric acied" read --dithiophosphoric acid-- bio-LL13 seam JAN 5 1971 mum a. eomiraiom or PM!