US3585137A - Synthetic ester lubricating oil composition - Google Patents

Abstract

SYNTHETIC NEUTRAL SATURATED CARBOXYLIC ACID ESTER LUBRICATING OILS SUCH AS THE DIBASIC ACID ESTERS, POLYBASIC ACID ESTERS, DIESTER-COMPLEX ESTERS, AND THE TRI AND TETRAESTERS OF POLYGLYCOLS WITH MONO OR DIBASIC ACIDS ARE IMPROVED ESPECIALLY AS TO THEIR SUPERSONIC TURBINE ENGINE PERFORMANCE BY INCORPORATING THEREINTO A METAL PASSIVATOR WHICH IS AN ANTHRANILAMIDE-TYPE COMPOUND HAVING THE FORMULA:

(R5,(R3-N(-R4)-)CYCLOHEXYL)-CO-N(-R1)-R2

WHEREIN R1 AND R2 AR EACH HYDROGEN, C1-C12 ALKYL, PHENYL, PENALKYL OR CYCLOALKYL, R3 AND R4 ARE EACH HYDROGEN, C1C9 ALKYL, C1-C13 ACYL OR PHENYL, AND R5 IS HYDROGEN, C1C9 ALKYL OR HALO C1-C9 ALKYL. PREFERABLY, THE NUCLEAR AMINO RADICAL IS ORTHO TO THE AMIDE GROUP. AN ARYLAMINE MAY BE ALSO EMPLOYED, AS AN ANTIOXIDANT, IN CONUCTION WITH THE ANTHRANILAMIDE-TYPE COMPOUND. AN ARYLTHIAZINE MAY BE USED IN CONJUCTION WITH THE ANTIOXIDANT. ADDITIONALLY, OTHER ADDITIVES SUCH AS PHOSPHATE ESTERS OR PHOSPHITE ESTERS, DIMER ACIDS (DILINOLEIC ACID) AND THE LIKE ARE ALSO INCORPORATED INTO THE ESTER LUBRICATING OIL FOR THE PURPOSE OF IMPROVING ITS EXTREME PRESSURE, ANTIWEAR AND/OR LOAD CARRYING PROPERTIES. IF DESIRED, STILL FURTHER ADDITIVES MAY BE INCORPORATED FOR THE PURPOSE OF REDUCING ACIDITY OR MINIMIZING ACIDITY INCREASES DURING USAGE OF THE OIL.

Description

United States Patent 3,585,137 SYNTHETIC ESTER LUBRICATING 01L COMPOSITION David S. Bosniack, Edison, and Stephen J. Metro, Scotch Plains, N.J., assignors to Esso Research and Engineering Company No Drawing. Filed June 25, 1969, Ser. No. 836,613 Int. Cl. (110m 1/32, 1/36, 1/44 U.S. Cl. 252-325 16 Claims ABSTRACT OF THE DISCLOSURE Synthetic neutral saturated carboxylic acid ester lubricating oils such as the dibasic acid esters, polybasic acid esters, diester-complex esters, and the tri and tetraesters of polyglycols with mono or dibasic acids are improved especially as to their supersonic turbine engine performance by incorporating thereinto a metal passivator which is an anthranilamicle-type compound having the formula:

wherein R and R ar each hydrogen, C C alkyl, phenyl, phenalkyl or cycloalkyl, R and R are each hydrogen, C C alkyl, (l -C acyl or phenyl, and R is hydrogen, C C alkyl or halo C -C alkyl. Preferably, the nuclear amino radical is ortho to the amide group. An arylamine may be also employed, as an antioxidant, in conjunction with the anthranilamide-type compound. An arylthiazine may be used in conjunction with the antioxidant. Additionally, other additives such as phosphate esters or phosphite esters, dimer acids (dilinoleic acid) and the like are also incorporated into the ester lubricating oil for the purpose of improving its extreme pressure, antiwear and/ or load carrying properties. If desired, still further additives may be incorporated for the purpose of reducing acidity or minimizing acidity increases during usage of the oil.

DESCRIPTION OF THE INVENTION Turbine engines are customarily employed in aircraft today. They are, however, subjected to extreme temperatures, and excessive corrosion difliculties are encountered because of the bearings and seals employed in such engines. Alloyed bearings are customarily used in such engines and the seals which are employed to retain the oil in the engine are also subjected to extremes of temperatures, which conditions necessitate the employment of highly specialized synthetic ester oils. Heretofore these oils have been improved by the use of minor amounts, i.e. of the order of 0.01 up to as high as 5.0 wt. percent of various special purpose additives, in an effort to overcome some of the deficiencies of the synthetic ester oils. The severity of operating conditions far exceeds those encountered in internal combustion automotive engines. It has not been advantageous to lubricate aircraft turbine engines using mineral oil com-positions. In the past, synthetic ester oils have performed far more satisfactorily but because of the operating conditions encountered such ester Too base oils, without further compounding, likewise tend to rapidly decompose, corrode metals, and attack oil seals even though improved metal alloys and oil seals are now conventionally employed. Consequently, it is customary to add small amounts of antioxidants, antiwear or high load reagents, metal passivators, anticorrosion agents, and the like, for the purpose of further improving these oils for their intended aviation use.

Many types of synthetic neutral saturated carboxylic acid esters are conventionally employed as turbine engine aviation lubricants. One of the problems presently being encountered is in manufacturing or compounding a synthetic ester lubricant which will be able to withstand even harsher operating conditions than have heretofore been encountered, namely, in lubricanting those turbine engines which are to power aircraft designed to fly at supersonic speeds. The instant invention is directed to the compounding of ester type oils which will satisfy the exacting requirements of such usage.

Heretofore, the synthetic neutral saturated carboxylic acid ester lubricants have employed phenothiazine or the nuclearly substituted C C alkyl derivatives thereof as an antioxidant. See, U.S. Pat. 3,218,256, column 2, as well as British Pat. 824,114, which latter mentioned patent also shows the use of benzotriazole in such capacity with or without the use of phenothiazine. Additionally, amine antioxidants as shown in column 3 of U.S. Pat. 3,247,111 have been employed in conjunction with the phenothiazine and benzotriazoles for the purpose of inhibiting the undue rapid oxidation of such synthetic ester oils. Phenolic antixodiants have been employed as well. Quinizarin and its simple derivatives and analogous compounds are also employed as antioxidants; see U.S. Pat. 3,247,111, column 4, lines 3-10. Still further additives have been employed to act as metal corrosion inhibitors such as sebacic acid as shown by British Pat. 928,798 and U.S. Pat. 2,730,871.

The load carrying additives which have been employed are generally the phosphate esters and phosphite esters; see, for example, U.S. Pats. 2,971,912, column 6; 3,215,720, column 1; and 3,247,111, column 4. In particular, dibutyl posphite and tricresyl phosphate have been widely used for the purpose of imparting antiwear or load carrying characteristics to the synthetic ester oils although any of the specific materials mentioned in the last three stated U.S. patents are also applicable conventionally for imparting load carrying properties to such oils. Specifically, tris (2-ethyl hexyl) phosphite ester, tris (butoxyethyl) phosphate ester and tris (beta chloroethyl) phosphate ester have been used. Other specific phosphorus esters are enumerated in the aforementioned three U.S. patents as improving the antiwear or load carrying ability of various synthetic ester based oils. The amine antioxidants, as shown in column 3 of U.S. Pat. 3,247,111, most often are N-phenyl alpha naphthylamine, N-phenyl beta naphthylamine or p,p-di-isooctyl diphenylamine, although any of the aromatic amines mentioned therein (lines 36-48) may be used in the instant novel oil compositions.

The synthetic neutralized saturated carboxylic acid ester lubricating oils which serve as the base oil and to which one or more of the aforementioned additives are added may be of several kinds. Numerous patents disclose these types of ester oils as being conventionally produced and used as shown by the following patents: 1,993,736; 2,249,768; 2,766,273; 2,015,088; 2,723,286; 2,743,234; 2,575,196; 3,218,256 and 3,360,465.

As examples of the specific types of oils to which the present invention relates, the following ester base oils are described; the triester and tetraester lubricating oils, the complex ester oils and the diester oils all of which are conventional articles of commerce. Such oils have heretofore all been used at one time or another and are still used in turbine engines that power aircraft. These engines are of the turbo jet, turbo prop, turbo fan and supersonic jet transport types. Because these engines and drive mechanisms for powering aircraft are all operated under extremely wide temperature ranges, the use of synthetic ester oils is presently almost an absolute necessity.

Briefly, these types of esters, as referred to in the above patents, can be described as being formed in the following manner. The triester and tetraester types are formed by reacting tri and tetra polyols such as trimethylol propane, pentaerythritol, trimethylol ethane, and higher trimethylol alkanes, and so forth, with C C e.g. C C normal or branched chain monocarboxylic acid or mixtures of two or more of such types of acids. These acids are exemplified by n-butanoic acid, valeric acid, caproic acid, heptanoic acid, caprylic acid, pivalic acid, 2-ethyl hexanoic acid, pelargonic acid, lauric acid and the like. The hexaesters of dipentaerythritol are also useful alone or admixed with the aforementioned tetraesters of monopentaerythritol.

Complex or polyester oils are also conventionally used. These are formed by esterifying polyols such as the glycols, the neopolyols previously mentioned, and the straight chain alkane diols with such dicarboxylic acids as succinic, glutaric, adipic, 2,2,4-trimethyl adipic acid, pimelic, suberic, azelaic, sebacic, brassylic acids, and dibasic dimer acids of oleic and/or linoleic acids. The diols or polyethoxylated diols of C C alkylene groups or mixtures thereof are also employed in preparing polyesters from the dibasic acids. The complex esters and their methods of preparation are conventional and are disclosed in representative US. patents such as 2,575,195 and 2,743,234, columns 36, inclusive.

Among the earliest types of synthetic esters employed as lubricating base oils are the diesters. These are conventionally formed from monohydric alcohols and dibasic acids. There are numerous references in the literature to their formation. These diesters are formed from the same dibasic acids used in connection with the formation of the complex esters hereinbefore described. The alcohols are such alcohols as the 0x0 alcohols or 0x0 alcohol mixtures such as C C oxo alcohols, or from 2-ethyl hexyl alcohols, n-octyl alcohol, nonyl alcohol,

either normal or branched chain, and 2,2,4 trimethyl pentanol and methyl cyclohexanol. Mixtures or blends of the various types of diesters with the complex esters, heretofore referred to, have been employed as synthetic lubricating oil compositions.

The synthetic ester oils or blends thereof generally have physical properties and specifications as follows: a viscosity index of at least 100, a pour or freezing point not exceeding 40 F., a boiling or decomposition temperature of at least 600 F., a Cleveland Open Cup Flash 'Point of at least 400 F., and a kinematic viscosity of less than 10 centistokes at 210 F. The supersonic turbine engine oils have a more exacting specification and requirement. These specifications are: a viscosity index of at least 100, a pour or freezing point not exceeding 65 F., a boiling or decomposition temperature of at least 600 F., a Cleveland Open Cup Flash Point of at least 450 F., and a kinematic viscosity of less than 5.5 to 6.0 centistokes at 210 F. The novel additive incorporated into the synthetic ester oils in accordance with the presently discovered advance in the art is applicable to the more generally used synthetic aviation ester oils of less exacting specification as well as to the more exacting requirements of the supersonic aviation turbine ester oils.

It has now been discovered that the aminobenzamides and their derivatives, when used in a sufficient amount to passivate metal components such as copper and magnesium, usually of the order of 0.015.0 wt. percent of the total ester oil composition, remarkably improve the anticorrosion characteristics of the oil with respect to the metals, reduce the deposit forming tendencies in the oil and improve the overall oil stability of the synthetic ester oils whether they be of the generally used aviation turbine types or of the highly specialized supersonic aviation turbine types. Ordinarily, the use of many phosphate esters or phosphite esters, for their antiwear and load carrying ability, results in increased metal corrosion, increased acidity and increased oil viscosity with continued oil use. Many materials have been employed in the past for the purpose of controlling metal corrosion but these oftentimes raise the acidity of the oil during its use. Use of copper corrosion inhibitor systems such as anthranilic acid with N-phenyl beta naphthylamine, for some reason which is unexplained, results in a marked increase in oil viscosity and acidity during their use in synthetic ester oils as turbine lubricants. Many of the metal passivators which have been used in the past will not work with some of the specific load carrying phosphate esters and phosphite esters because when added to the oil they react with the passivator and this defeats the purpose for which the passivator was added in the first place. The acidity of the ester oil is increased with continued use even though conventional nitrogen-containing additives (aromatic amino compounds) have been used as antioxidants therein. The use of the aminobenzamide-type compounds not only reduces the acidity and viscosity increase during oil usage but additionally dramatically reduces corrosion of copper and magnesium as well as that of other metals present in the turbine engines.

Compounds which are useful in the synthetic neutral saturated carboxylic acid ester lubricating oils have the following formula:

wherein R and R are each hydrogen, C -C alkyl, phenyl, phenalkyl or cycloalkyl, R and R are each hydrogen, C -C alkyl, C -C acyl, or phenyl, and R is hydrogen, C -C alkyl or halo C -C alkyl. Specifically, typical alkyl radicals are methyl, ethyl, isopropyl, n-proply, butyl, hexyl, octyl, decyl, or dodecyl, of either straight chain or branched chain configuration; typical phenalkyl radicals are benzyl, phenethyl, phenpropyl, etc.; typical cycloalkyl radicals are cyclohexyl and cyclopentyl; and typical acyl radicals are acetyl, propionyl, butyryl, lauroyl, caproyl, capryl, caprylyl, etc.; and halo alkyl may be fiuoro or chloro mono or di-substituted methyl, ethyl, etc., i.e. the same specific alkyl radicals as set forth above for C C alkyl. Orthoaminobenzamide (anthranilamide) and its derivatives are most useful as an additive for sythetic ester lubricating oils. Also metaaminobenzamide may be employed. Other useful compounds are:

The foregoing compounds as well as many others analogous thereto, but not specifically set forth, are prepared by conventional methods. See, for example, the methods set forth in Butler et al., Jour. of Am. Chem. Soc. (1959), pp. 2396-2400; Petyunin et. al., Zhur. Obshchei Khim. 30, 2028-2030 (1960); Petyunin et al., ibib 30, 2453-7 (1960) and Jacobs et al., Jour. Am. Chem. Soc. 34, 1437-8 (1917).

Most generally, the synthetic ester oils will contain between about 0.01 and 5.0 wt. percent, preferably between about 0.05 and about 0.2 wt. percent. Such small amounts do not necessitate a high degree of oil solubility of the anthranilamide-type component. The solubility of anthranilamide, per se, is sufficiently high in ester oils that it is unnecessary to substitute onto either the amino or amido nitrogen, an alkyl or cycloalkyl radical for the purpose of improving the oil solubility of the anthranilamide. Anthranilamide, or its simple hydrocarbon substituted or chlorhydrocarbon substituted derivatives, find great utility when these are used in association with the usual aromatic amino hydrocarbon antioxidants heretofore employed. Optionally, these compounds are also of quite high effectiveness in passivating or inhibiting metals such as copper and/or magnesium when used in association with mono or di, or mixed mono and dialkyl phosphate or phosphite esters or the primary amine salts of dibasic or monobasic chloralkyl-phosphoric acid as described in U.S. Pat. 2,858,332. One useful antiwear load bearing phosphate ester is a mixture of mono and dimethyl phosphate esters neutralized with a branched chain mixed primary C -C alkyl amine. Other similar types of acidic phosphate or phosphite esters neutralized with primary or secondary long chain alkyl amines are also equally eificacious. Thus, for example, a mixture of C -C mono and di'alkyl hydrogen phosphates partially or completely neutralized with Primene 81-R (a commercial mixture of C -C alkyl primary amine) is also suitable.

In all cases, the conventional materials previously employed such as phenothiazine, the benzotriazoles, quinizarin and its analogues, and the primary and secondary aromatic amino antioxidants may also be used in association with the anthranilamides or their nitrogen substituted hydrocarbon derivatives. The amount employed of the conventional additives are those which have here tofore been employed. These amounts range between about 0.01 and about 5.0 wt. percent. -It has, however, been discovered that it is unnecessary to employ benzotriazole, heretofore used as a specific copper corrosion inhibitor, when one employs the aminobenzamide or its derivatives as a metal passivator. Benzotriazole, while effectively minimizing metal corrosion, markedly increases magnesium corrosion and increases total acidity buildup. Desirably, its use should be eliminated for these reasons. The use of the aminobenzamides or their derivatives has now made it possible to eliminate the use of benzotriazole and/ or its derivatives and at the same time employ some of the more efficacious phosphate and phosphite esters as load carrying additives in synthetic ester oils whereas, before, such highly effective load carrying phosphorus additives could not be employed because they imparted too great a tendency for acidity buildup, during usage of the synthetic oils, to permit any practical application of such oils in commercial operation. The anthranilamide-type component effectively controls and minimizes acidity buildup during usage of the ester aviation oils.

Anthranilamide may be prepared by a number of processes but the one which is generally employed involves the reaction of anthranilic acid with chloro carbonic esters of the lower aliphatic alcohols to form isatoic anhydride which is then reacted with ammonia or with a suitable primary or secondary amine to produce anthranilamide or the amino nitrogen substituted alkyl derivatives thereof. Similarly, for those derivatives of anthranilamide in which the amino nitrogen is substituted as heretofore set forth instead of using anthranilic acid the corresponding N-alkyl 0r N-cycloalkyl derivatives of anthranilic acid are used. The reaction of isaotic anhydride with ammonia or a corresponding amine is an old and conventional reaction and is disclosed in Journal fur Praktische Chemie, volume 30, page 467; volume 33, page 18; and volume 48, page 92. Anthranilamide and its analogue may also be produced by the chemical reduction or by catalytic hydrogenation of ortho or methanitrobenzamide and, of course, the amido nitrogen alkyl substitutions can be placed on the corresponding benzamide prior to the chemical reduction or catalytic hydrogenation of the corresponding orthonitrobenzamide. This method is described in the Journal of the American Chemical Society, volume 34, pp. 1435-1438 (1917). The present invention is not limited to any particular method of producing the anthranilamide or its N-substituted hydrocarbon derivatives since these are well known and conventional reactions used in the commercial production of such amides or their analogues.

In the following examples, the test data have been obtained using standard tests for determining the suitability of the aviation ester lubricants for their intended use. One of the tests which have been employed is the so-called Oxidation/ Corrosion Stability Test. This is a standardized test procedure described in Specification FTMSTD 791 Method 5308. Briefly, this test involves blowing air through the oil to be tested at a specified temperature for a specified length of time (usually 347 F. for 72 hours or 400 F. for 72 hours) in the presence of metal specimens consisting of aluminum, magnesium, steel and copper tied together to form a square with a silver specimen inserted as a diagonal between the copper and steel and the aluminum and magnesium junctions. The number of hours of test and the temperatures can be varied from those above specified but if and when such is the case in connection with the following tests, expressed mention of this deviation or variation will be made. The test is a severe test, the results being affected by the specific chemical nature of the ester base oil and by the nature of the additive or additives present in the oil during test. The test is designed to measure the attack on the various metal specimens, the percentage of change in viscosity measured in centistokes at F. (usually this is an increase in viscosity), the total increase in acidity meas ured as total acid number (TAN) measured in milligrams of KOH per gram of oil. The attack on the various metals is measured in milligrams per square centimeter (although in some cases a protection film or deposit forms resulting in a plus value instead of a minus value) and finally, although not always, the amount of sludge or insolubles formed in grams per 100 mls. of oil is also determined.

Still another test which has become more or less standard, designed to measure the load carrying ability or anti-wear ability of the synthetic oil under test is known as the Ryder Gear Test which is also to be found and described in FTMSTD 791 Method 6508.

The following examples illustrate the nature of the invention but it is not intended that the invention be limited thereto.

EXAMPLE 1 The following compounded synthetic aviation oil was prepared: 100 parts constituted the tetraester and the hexaester of a mixture of 90% monopentaerythritol and 10% dipentaerythritol poly esterified with mixed C -C normal alkanoic acids. Based on the 100 parts of the ester base oil, (this and all subsequent oil compositions are also based on 100 parts by weight of ester base oil) the following additives (also in parts by weight per 100 parts of base oil) were added:

1.6 p,p'-dioctyl diphenylamine; 0.4 phenothiazine;

0.02 sebacic acid;

0.05 benzotriazole; and

0.1 of a mixture of phosphate esters which amounted to about 3 parts of the dodecylamine salt of dimethyl phosphate and 2 parts of di (dodecyl) amine salt of monomethyl phosphate.

In the following table, the designation, 1a, in the base oil example column, indicates the 100 parts of base oil but without any of the above set forth additives.

EXAMPLE 2 Same base ester oil as in Example 1. 1.0 p,p'-dioctyl diphenylamine; and 1.0 N-phenyl beta naphthylamine.

EXAMPLE 3 Same base ester oil as in Example 1.

1.6 p,p-dioctyl diphenylamine;

0.02 sebacic acid;

0.1 of same amine neutralized phosphate ester mixture as in Example 1; and

0.1 quinizarin.

8 EXAMPLE 4 Same base ester oil as in Example 1. 1.6 p,p'-dioctyl diphenylamine; 0.4 phenothiazine; 0.02 sebacic acid; and 0.1 of same amine neutralized phosphate ester mixture as in Example 1.

EXAMPLE 5 Same base composition as in Example 4 but contains, in addition, 0.1 quinizarin.

EXAMPLE 6 35 parts monopentaerythritol ester of a mixture of C -C normal alkanoic acids;

parts of the base oil (without additives) of Example l;

15 parts of dipentaerythritol fully esterified with npentanoic acid;

Plus same additives in same amounts as in Example 6.

EXAMPLE 8 50 parts of base oil of Example 1 (without additives);

15 parts of dipentaerythritol fully esterified with npentanoic acid;

35 parts of same triester oil of Example 6;

Plus same additives in same amounts as in Example 6.

EXAMPLE 9 parts of triester of Example 6; 30 parts of dipentaerythritol fully esterified with npentanoic acid;

Plus same additives in same amounts as in Example 6.

EXAMPLE 10 parts of the coester of equal parts of 2-ethylhexyl alcohol and hexadecyl alcohol fully esterified with azelaic acid;

1.6 p,p'-dioctyl diphenylamine;

0.4 phenothiazine;

0.02 sebacic acid;

0.1 quinizarin; and

0.1 same amine neutralized phosphate ester mixture us in Example 1.

TAB LE I Used oil Percent Corrosion, change in Total acid .8 ase oil, Add. mg./em. viscosity, number, Example amount, increase increase- Example N0. N0. Additives pts. Cu Mg cs. at 100 F. Mg-KOH/gm.

11 1 None 0. '73 +0. 09 36.13 4.03 12 1 Anthranilic acid. 0.05 0. 56 +0. 09 33. 96 3, 23 Anthranilie acid 0. 0.5

13 1 N-phenyl B.

Naphthylamine. 0. 25 14 1 Anthranilamide 0. 1 0. 2 {Anthranilamid 0. 1 Quinizarin 0. 1 1 {Anthranilamide 0.2 Quinizarin 0. 1 1a None t 1a Ant. anilamidm 0. 1 11: .....(lo 0.25 it! 'lricrcsylplrospln 1.00 m tAnthranilamide 0.25 lTricresylphosphate 1. 00

TABLE I.-Oontinued Used 011 Percent Corrosion, change in Total acid Base 011, Add. mg./cm. viscosity, number,

xample amount, increase increase- Exarnple No. No. Additives pts. Cu Mg cs. at 100 F. Mg KOH/gm 2 None 1. 29 1. 92 35. 40 13. 6 2 Anthrarulamide 0. 1 -0. 14 --0. 02 31. 70 1. 04 {Anthranilamide 0. 1 0. 23 -.0. 01 33. 57 1. 69 Phenothiazine 0. 4 2 -(N-neocapryly1 amino) benzarnide- 0. 1 38. 86 1. 59 2 O-NHz, N-octyl benzarnide 0. 1 33. 63 1. 09 2 ONHQ, N-phenyl benzamide 0. 1 83. 39 0. 96 2 o-(CH NH) benzamideuu 0. 1 32. 86 0. 92 2 O-(CH NH),N,N diethyl, m 0. 1 22. 39 0.98 2 0-NH ,N,N diethyl, benzamide 0. 1 20. 32 4. 72 3 None i 44. 24 12. 53 3 Anthranilamide 0. 1 41. 12 8. 01 3 Phenothiazine 0.4 16. 1. 3 {Anthranilamida 0. 1 Phenothiazine 0.4 18. 19 0, 92 4 one 1 24. 61 2. 65 4 Anthranilamide. 0.2 24. 17 2. 17 4 Benzotriazole- 0. 2 11. 23 6. 39 5 None 21. 78 2. 5 Anthranilamide. 0. 1 22. 00 1. 65 5 Benzotriazole. 0. 1 12. 10 5. 69 6 Anthranilami 0. 1 21. 00 2. 52 7 0. 1 24. 95 1. 04 O. 1 22. 00 1. 75 0. 1 19. 56 1. 50 135. 00 22. 00 10 Anthranilamide 0. 1 51. 9O 19. 24

1 Too heavy Norm-All The US. Navy Specification MIL-L-23699A for 5 centistokes gas turbine lubricants for oxidation-corrosion tests 400 F. for 72 hours is as follows:

10.4 copper corrosion in milligrams per square centimeter;

$0.2 milligram per square centimeters magnesium, silver, aluminum and iron corrosion;

A differential increase or decrease in the used oil as to the viscosity at 100 F. in percentage change of -5% to +25%; and

A differential increase in used oil total acid number of 3.0 milligrams KOH per gram of oil maximum.

From the above tabulated data, it is at once apparent that for maximum effectiveness, there is decided improvement in meeting these specifications in the use of both anthranilamide type compounds and aromatic amines and that the presence of benzotriazole, if anything, is not so important, and not necessary. The presence of quinizarin although not required to meet Navy specifications, is nevertheless advantageous in improving used oil properties. Anthranilamide and its derivatives are beneficial when used in synthetic ester lubricating oils alone or along with conventional additives in that copper and magnesium corrosion is minimized, and the viscosity increase and acidity increase are also held to a minimum.

The present invention having now been fully described and illustrated, what is desired to be secured by Letters Patent is:

1. A lubricating oil composition comprising a major portion of a synthetic neutral saturated carboxylic acid ester lubricating oil, and an amount, sufficient to inhibit metal corrosion, of an amino-benzamide having the formula:

wherein R and R are each hydrogen, C -C alkyl, phenyl, phenalkyl or cycloalkyl, R and R are each hydrogen, C -C alkyl, C -C acyl, or phenyl and R is hydrogen, C -C alkyl, or halo C -C alkyl.

of the data set forth in the table were obtained by carrying out the tests at 400 F. for 72 hours.

2. A lubricating oil composition comprising a major portion of a synthetic neutral saturated carboxylic acid ester lubricating oil, an amount, sufiicient to inhibit oxidation, of an aromatic amine antioxidant, and an amount, sufficient to inhibit metal corrosion, of an aminobenzamide having the formula:

wherein R and R are each hydrogen, C -C alkyl, phenyl, phenalkyl or cycloalkyl, R and R are each hydrogen, C -C alkyl, C C acyl, or phenyl and R is hydrogen, C -C alkyl, or halo C -C alkyl.

3. A lubricating oil composition as in claim 2 wherein the nuclear substituted amino group is in the ortho position.

4. A lubricating oil composition as in claim 2 wherein the metal corrosion inhibitor is anthranilamide.

5. A lubricating oil composition as in claim 2 wherein the oil composition also contains an arylthiazine.

6. A lubricating oil composition as in claim 5 wherein the aryl-thiazine is phenothiazine.

7. A lubricating oil composition as in claim 3 wherein the oil composition also contains a phosphorus ester.

8. A lubricating oil composition as in claim 3 wherein the oil composition also contains an amine addition salt of a phosphorus ester.

9. An oil composition as in claim 5 wherein the arylthiazine is phenothiazine and the composition also contains a phenol.

10. An oil composition as in claim 5 wherein the arylthiazine is phenothiazine and the aromatic amine is p,p'- dioctyl diphenylamine.

11. An oil composition as in claim 7 which also contains phenothiazine and the aromatic amine is p,p-dioctyl diphenylamine.

12. An oil composition as in claim 2 wherein the ester oil is the tetraester of pentaerythritol with a mixture of C -C normal alkanoic acids.

12 13. An oil composition as in claim 2 wherein the ester References Cited base oil is the triester of trimethylol propane with at least UNITED STATES PATENTS Immal alkamic acid- 2,330,239 9/1943 Prutton 252-51.5A 14. An oil composition as in claim 12 wherein the metal 2,959,550 11/1960 Young et ah 252 51 5A corrosion inhibitor is anthranilamide. 3 3 224 969 12/19 5 Hotten 252 51 5 15. An oil composition as in claim 14 which also con tains an arylthiazine E. Primary Examiner 16. An oil composition as in claim 15 wherein the aryl- W. J. SHINE, Assistant Examiner thiazine is phenothiazine, the aromatic amine is p,p'-dioctyl 10 diphenylamine and the composition also contains an amine addition salt of a phosphorus ester.