Daniels, David A. (Kendall Park, NJ)
Degeorge, Nicholas F. (Metuchen, NJ)

05/379821

03/04/1975

07/16/1973

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W. R. Grace & Co. (New York, NY)

508/252

508/563

C10M1/38; C10M1/46

252/46.7,47.5,47,50,56S

Cannon W.

Fisher, Elton Prince Kenneth E.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of copending application, U.S. Ser. No. 152,435, filed June 11, 1971, now abandoned.

What is claimed is

1. A lubricant composition comprising:

2. The lubricant composition of claim 1 in which:

3. The lubricant composition of claim 2 in which the octyl groups of the phenothiazine are 1,1,3,3-tetramethylbutyl groups.

4. The lubricant composition of claim 2 in which the first group member is p,p'-dioctyldiphenylamine.

5. The lubricating composition of claim 4 in which the p,p'-dioctyldiphenylamine is p,p'-(1,1,3,3-tetramethylbutyl)diphenylamine

6. The lubricant composition of claim 2 in which the second group member is N,N-bis-4-octylphenylbenzylamine.

7. The lubricant composition of claim 6 in which the N,N-bis-4-octylphenylbenzylamine is N,N-bis-4-(1,1,3,3-tetramethylbutyl)-phenylbenzylamine.

8. A lubricant composition comprising:

9. The lubricant composition of claim 8 in which:

10. The lubricant composition of claim 9 in which the octyl groups of the phenothiazine are 1,1,3,3-tetramethylbutyl groups.

11. The lubricant composition of claim 9 in which the first group member is p,p'-dioctyldiphenylamine.

12. The lubricating composition of claim 11 in which the p,p'-dioctyldiphenylamine is p,p'-(1,1,3,3-tetramethylbutyl)diphenylamine.

13. A lubricant composition comprising:

14. The lubricant composition of claim 13 in which:

15. The lubricant composition of claim 14 in which the octyl groups of the phenothiazine are 1,1,3,3-tetramethylbutyl groups.

16. The lubricant composition of claim 14 in which the first group member is N,N-bis-4-octylphenylbenzylamine.

17. The lubricant composition of claim 16 in which the N,N-bis-4-octylphenylbenzylamine is N,N-bis-4-(1,1,3,3-tetramethylbutyl)-phenylbenzylamine.

18. A lubricant composition comprising:

19. -amino-1,2,4-triazole,

20. -amino-1,2,4-triazole,

21. ,2,3-benzotriazole, and

22. ,5'-methylene-bis-(1,2,3-benzotriazole).

23. A lubricant composition comprising:

BACKGROUND OF THE INVENTION

The present invention relates to an improved ester base lubricant composition including small amounts of N-substituted phenothiazine and secondary or monoaralkyl tertiary aromatic amine, and to a method for lubricating surfaces using this composition. The substituents on the phenothiazine nitrogen is an aralkyl group which is substituted by at least one member of the group consisting of halo, nitro, alkoxy, and hydroxy groups. In use, the present composition exhibits better cleanliness and improved oxidative stability even at elevated use temperature.

Ester base lubricants have been available to the art and have been used with some success for high temperature lubrication. With the development of high-temperature jet engines, increasing use has been made of synthetic lubricants based on organic esters of the diester type such as diesters derived from adipic, azelaic and sebacic acids by esterification of C ₈ to C ₁₀ alcohols. An example of such a widely used synthetic lubricant is di(2-ethylhexyl) sebacate which has been employed in jet engine oils and in related lubricants. However, recent heavy demands and price competition have led to use of a variety of diesters from more readily available dicarboxylic acids.

Various known ester base or synthetic lubricating compositions have often included minor amounts (e.g., about 0.5 to 1 weight percent) of phenothiazine for stabilization against oxidation. While oxidation stability of these lubricants has been somewhat improved using phenothiazine, overall improvement has been minimized by associated formation of insolubles and deposition of often substantial amounts of sludge. Failure of the prior art to effectively solve oxidation stability and especially cleanliness problems associated with synthetic lubricants containing phenothiazines, especially at higher temperatures, has given rise to the term "phenothiazine dirtiness."

A number of lubricant compositions including various phenothiazine derivatives have been proposed. For example, Edwards, et al., U.S. Pat. No. 3,218,256, describes a lubricating composition which consists essentially of (1) a synthetic lubricating oil consisting essentially of a carboxylic acid ester base, the oil having dissolved therein (2) a non-N-substituted, phenylene ring alkylated or alkoxylated phenothiazine (preferably 3,7-dioctyl phenothiazine), (3) a secondary aromatic amine selected from diphenylamines and N-phenylnaphthylamines, and (4) benzotriazole.

U.S. Pat. No. 3,344,068 to Waight, et al., describes a lubricating composition which includes a major amount of an ester base lubricating oil and minor amounts of an N-substituted phenothiazine and a secondary aromatic amine having two aromatic groups attached to the amine nitrogen atom. The substituent on the phenothiazine nitrogen is selected from a hydrocarbyl group having 1 to 12 carbons and a cyanoalkyl group having 1 to 20 carbons. The hydrocarbyl group can be alkyl, aryl, alkaryl, or aralkyl. At least one of the aromatic rings of the phenothiazine is substituted by an alkyl or alkoxy group having from 1 to 12 carbons. The composition is illustrated in the patent by a variety of specific formulations, the majority of which include 10-benzyl-3,7-dioctylphenothiazine as the N-substituted phenothiazine component. Data representing results of oxidation/corrosion tests at 175°C. is presented for (i) three of the 10-benzyl-3,7-dioctylphenothiazine containing formulations and (ii) three otherwise identical formulations except containing 3,7-dioctylphenothiazine (the preferred phenothiazine of U.S. Pat. No. 3,218,256 noted above) and no 10-benzyl-3,7-dioctylphenothiazine. It is concluded in the patent that the aforesaid "i" formulations show a resistance to oxidation and corrosion at high temperature which is at least as good as that shown by the comparative "ii" formulations. Also presented are data comparing type "i" and type "ii" formulations for storage tests at 15° and 80°C. and a conclusion that only the formulations containing 10-benzyl-3,7 -dioctylphenothiazine give satisfactory performance in the storage tests.

British Pat. No. 873,066, issued July 19, 1961, discloses preparation of N-substituted phenothiazines by reacting alkyl or aralkyl halides with alkali metal phenothiazines formed from alkali metal and either phenothiazine or derivatives thereof.

The patent literature outlined above is representative of the field of synthetic lubricants containing substituted phenothiazines and secondary aromatic amines. Other patent literature which may be of interest is summarized below.

Cohen, U.S. Pat. No. 2,957,022, teaches esters prepared from cyclic dicarboxylic acids having five carbon atoms in the ring. The esters are disclosed to be useful as lubricating oils.

U.S. Pat. No. 2,308,282 to Howland, et al., teaches corrosion inhibitors or retarders for protecting metal surfaces. The corrosion inhibitors are disclosed to be ammonia compounds of the formula aralkyl--N(X ₁ )X wherein X and X ₁ are hydrogen, alkyl, or aralkyl.

Use of N--(C ₁ --C ₁₄ alkyl)-p,p'-dioctyldiphenylamines as antioxidants for lubricating oils is taught in U.S. Pat. No. 3,368,975 to Davis, et al.

Peterli, et al., U.S. Pat. No. 3,475,112, teaches iminodibenzyl compounds which are disclosed to serve as antioxidants in synthetic lubricants.

British Pat. No. 1,124,904, Carswell, teaches a lubricating grease comprising a lubricating oil, a thickener, and a minor proportion of a 1,2,4-triazole which may be 3-amino-1,2,4-triazole. This British patent corresponds to Dutch Patent Publication No. 68/09807.

Typically, known synthetic lubricant compositions containing phenothiazines and secondary aromatic amines have not been entirely satisfactory at high temperature service due to rapid degradation leading to undesirable changes in viscosity, excessive deposit formation, increased corrosion and other undesirable results. Moreover, many of these lubricating compositions do not meet stringent oxidative stability and cleanliness requirements of lubricant users.

It has not been found by practice of the present invention that there is provided a new improved ester base lubricant composition including minor amounts of N-substituted phenothiazine and secondary or tertiary aromatic amine components, more fully described hereinafter. In use, the present lubricant composition typically exhibits good storage stability, better cleanliness and improved oxidative stability at high temperatures, e.g., about 250°F to about 400°F and higher. Surfaces lubricated by the the present composition often show increased service life, decreased wear and less corrosion.

SUMMARY OF THE INVENTION

Generally stated, the present lubricant composition includes a major amount of a carboxylic acid ester component; a minor stabilizing amount of an aromatic amine component which may be a secondary aromatic amine having two aromatic groups, a tertiary aromatic amine having two aromatic groups and an aralkyl group, or a mixture thereof, where the aromatic nuclei of the aromatic groups and the substituted alkyl moiety of the aralkyl group are attached directly to amine nitrogen atom; an N-substituted phenothiazine component having the following general formula: ##SPC1##

where R is a C ₇ to about C ₂₂ aralkyl group which, as more fully described below, is characterized by (a) being ring substituted by at least one member selected from the group consisting of halo, nitro, alkoxy, hydroxy, and alkyl groups, (b) having a particularly defined alkylene linkage, or (c) both characteristics (a) and (b); and R ₁ , R ₂ , R ₃ and R ₄ are members selected from the group consisting of a hydrogen atom, and alkyl, alkoxy, and aralkyl groups having from 1 to about 12 carbon atoms; and optionally, a triazole component and/or a phosphorus-containing acid ester component.

In use, a suitable amount of the present improved composition may be applied to a surface to be lubricated, or the lubricant may be circulated about parts to be lubricated, as desired.

DETAILED DESCRIPTION OF THE INVENTION

The carboxylic acid ester component of the present lubricant composition may be almost any carboxylic acid ester which is suitable for lubricating. Suitable esters include aliphatic diesters having the general formula R ₅ QOC(CH ₂ ) _n COOR ₆ wherein n is an integer from about 2 to about 34, and R ₅ and R ₆ are members selected from the group consisting of straight and branched chain alkyl, phenoxyalkyl, and alkyloxyalkyl groups having from about 6 to about 20 carbon atoms. Preferably, n is from about 4 to about 8 and R ₅ and R ₆ are selected from straight and branched chain alkyl groups having from about 8 to about 16 carbon atoms. Exemplary esters of this type include di(2-ethylhexyl) sebacate, di(2-ethylhexyl) azelate, diisodecyl sebacate, diisooctyl azelate, isooctylisodecyl adipate, di(1,3-dimethylbutyl) adipate, and the like.

The carboxylic acid ester component may also include esters derived from aliphatic monocarboxylic acids by esterifying these acids with polyols, i.e., aliphatic alcohols having 2 or more hydroxy groups. Acids suitable for deriving these esters include aliphatic acids having from about 3 to about 18, and preferably from about 4 to about 12 carbon atoms. Suitable polyols include, for example, trimethylolpropane, neopentyl glycol, pentaerythritol, dipentaerythritol, tripentaerythritol and mixtures thereof. Exemplary esters of this class include pentaerythrityl tetrabutyrate, pentaerythrityl tetracaproate, pentaerythrityl dibutyrate-dicaproate, mixed C ₄ to C ₁₀ saturated fatty acid esters of pentaerythritol, dipentaerythrityl mixed hexaesters of C ₄ to C ₁₀ fatty acids, trimethylolpropane tricaprylate, and the like.

The carboxylic acid ester component may further include aliphatic polyesters having the following general formula: ##SPC2##

wherein R ₇ is an alkyl group having from 1 to about 12 carbon atoms, and preferably from about 5 to about 12 carbon atoms in branched chain configuration with a tertiary carbon atom adjacent the carbon atom which is linked to the oxygen atom. R ₈ is an alkylene group having from about 6 to about 20 carbon atoms in straight or branched chain configuration, and R ₉ is an alkylene or oxyalkylene group having from about 2 to about 20 carbon atoms. These polyesters may be prepared, for example, by esterifying two moles of aliphatic dicarboxylic acid per mole of glycol, followed by esterifying the resulting diester product having two --COOH groups with two moles of monohydric alcohol per mole of the product.

The ester component of the present lubricant composition may include mixtures of the above-described carboxylic acid esters. Typically, the composition includes the ester component in a major amount.

The aromatic amine component of the present lubricant may be selected from secondary amines having two aromatic groups attached to a nitrogen atom of the amine. The aromatic groups may be heterocyclic or homocyclic, as desired. Preferably, the aromatic groups are homocyclic aromatic groups of the benzene series and alkyl substituted derivatives thereof. Phenothiazine and phenothiazine derivatives having one or more substituents on their phenylene rings may prove useful as the secondary aromatic amine component. However, as a general preference the two aromatic groups included in the amine component are free of inter-connecting atoms other than nitrogen. The aromatic groups of the amine component may have the same or different formulas, as desired. The secondary aromatic amine component may be selected from the group consisting of N-phenylnaphthylamines and diphenylamines. Exemplary aromatic amines suitable herein are N-phenyl-1-naphthylamine, diphenylamine, N-phenyl-2-naphthylamine, alkyl or alkoxy substituted derivatives of these compounds, and mixtures thereof. Preferably, at least one of the aromatic groups on each of the various amines is alkyl or alkoxy substituted, e.g., N-(4-octyl)phenyl-2-naphthylamine, N-(4-octyl)phenyl-1-naphthylamine, and the like. The alkyl and alkoxy groups may have from about 4 to about 12 carbon atoms and preferably about 8 carbon atoms. A preferred amine component is p,p'-dioctyldiphenylamine, which may be, for example, 4,4'-(2,2,3,3-tetramethylbutyl)-diphenylamine. Other preferred aromatic amines includes N-4-octylphenyl-1-octyl-2-naphthylamine. Especially preferred amines include N-4-(1,1,3,3-tetramethylbutyl)-phenyl-1-naphthylamine, N-4-(1,1,3,3-tetramethylbutyl)-phenyl-2-naphthylamine, N-4-(1,1,3,3-tetramethylbutyl)-phenyl-N-1-(1,1,3,3-tetrameth ylbutyl)-2-nap hthylamine, and 4,4'-(1,1,3,3-tetramethylbutyl)diphenylamine. Mixtures of suitable secondary aromatic amines may be included in the present lubricant composition. The secondary amine may be included in a minor stabilizing amount, for example, from slightly above 0 (e.g., about 0.1) to about 8 parts by weight or more, typically from about 0.5 to about 8 parts by weight, and preferably from about 1 to about 4 parts by weight, per 100 parts by weight of the carboxylic acid ester component.

The N-substituted phenothiazine component of the present lubricant may be represented by the following general formula: ##SPC3##

where R is a particularly defined aralkyl group having from 7 to about 22 carbon atoms. In a preferred aspect of the present invention, R is ring substituted by at least one member selected from the group consisting of halo, nitro, alkyl, alkoxy, and hydroxy groups. In general, R may be selected from the groups having the following general formulas: ##SPC4##

wherein n is an integer in the range from 0 to about 4; R ₁₀ and R ₁₁ are selected from chlorine atom, hydrogen atom and methyl group; and A, B, D, E, F, G, and J are members selected from the group consisting of hydrogen atom and halo, nitro, hydroxy, alkyl, and alkoxy groups such that at least one of the members A, B, D, E, F, G, and J is other than hydrogen atom when both R ₁₀ and R ₁₁ are hydrogen atoms. Preferred alkyl and alkoxy groups having 1 to about 12 carbon atoms. Preferred halo substituents are fluoro, bromo and chloro, Generally, the present lubricant composition exhibits even better stability where A, B, D, E, F, G, and J are selected from the subgenus consisting of hydrogen atom, fluoro, chloro, bromo, nitro, hydroxy, and C ₁ to about C ₁₂ alkoxy groups such that at least one of A, B, D, E, F, G and J is other than hydrogen atom when both R ₁₀ and R ₁₁ are other than chlorine atoms. Exemplary of suitable R groups are 2,4-dichlorobenzyl; 3,4-dichlorobenzyl; 2-(4-chlorophenyl)ethyl; 2,4-dibromobenzyl; 3,4-dibromobenzyl; 4-nitrobenzyl; 4-hydroxybenzyl; 4-butoxybenzyl; and the like.

R ₁ , R ₂ , R ₃ and R ₄ are members selected from the group consisting of hydrogen atom and alkyl, alkoxy, and aralkyl groups having from 1 to about 12 carbon atoms. For greater oxidative stability at least one of R ₁ , R ₂ , R ₃ and R ₄ is C ₁ to about C ₁₂ alkyl or alkoxy. Preferably, 2 of these substituents are selected from straight and branched chain octyl groups. The 2 groups may be on the same or different phenylene rings of the phenothiazine structure, as desired.

The N-substituted phenothiazine component may be an N-(R)-3,7-dioctylphenothiazine wherein R is a member selected from the group consisting of 2-chlorobenzyl; 4-chlorobenzyl; 2,4-dichlorobenzyl; 3,4-dichlorobenzyl; α,α-dichlorophenylmethyl; 2-fluorobenzyl; 4-fluorobenzyl; 2-nitrobenzyl; 4-nitrobenzyl; 2-methylbenzyl; 4-methylbenzyl; and 2,2-dimethyl-2-phenylethyl. Preferably, R is selected from the group consisting of 2-chlorobenzyl; 4-chlorobenzyl; 2,4-dichlorobenzyl; 3,4-dichlorobenzyl; α,α-dichlorophenylmethyl; 2-fluorobenzyl; 2-nitrobenzyl; and 4-nitrobenzyl. The octyl groups in the N-(R)-3,7-dioctylphenothiazines may be, for example, 2,2,3,3-tetramethylbutyl groups, and preferably 1,1,3,3-tetramethylbutyl groups.

An especially preferred N-substituted phenothiazine component is N-(2,4-dichlorobenzyl)-3,7-dioctylphenothiazine. Another especially preferred compound is N-(3,4-dichlorobenzyl)-3,7-dioctylphenothiazine. It is to be understood that in these preferred compounds R ₂ and R ₃ are octyl groups, e.g., 1,1,3,3-tetramethylbutyl groups, while R ₁ are R ₄ are hydrogen atoms. Lubricants of the present invention which typically have excellent lubricant qualities include those which contain N-substituted phenothiazines having 1,1,3,3-tetramethylbutyl substituents attached as shown by R ₂ and R ₃ , e.g., N-(2,4-dichlorobenzyl)-3,7-(1,1,3,3-tetramethylbutyl)-phenot hiazine.

The N-substituted phenothiazine component together with the aromatic amine component aids in improving cleanliness and oxidative stability of the present lubricant composition. The N-substituted phenothiazine component may be included in the composition in a minor stabilizing amount, for example, from slightly above 0 (e.g., about 0.l) to about 10 parts by weight or more, typically from about 0.5 to about 10 parts by weight, and preferably from about 0.5 to about 3 parts by weight, per 100 parts by weight of the carboxylic acid ester component.

Preparation of N-substituted phenothiazines is taught in copending Daniels applications "Preparation of Tertiary Amines", U.S. Ser. No. 152,372 filed June 11, 1971; U.S. Ser. No. 308,890 filed Nov. 22, 1972 (a divisional of said application Ser. No. 152,372); and U.S. Ser. No. 379,834 filed July 16, 1973 under attorney docket number 4231 (a continuation-in-part of said application Ser. No. 308,890). The various applications last referred to are assigned to the assignee hereof.

N-(3,4-dichlorobenzyl)-3,7-(2,2,3,3-tetramethylbutyl)phe nothiazine, for example, may be prepared substantially as next described. 1.5 moles of dimethylsulfoxide is added to a 3 liter reaction flask equipped with a condenser, stirrer, nitrogen inlet, thermometer and dropping funnel. After heating the dimethylsulfoxide to about 60°C., 1.1 moles of 60 percent by weight sodium hydride dispersed in mineral oil is added with stirring. Generally, the reaction mixture turns slightly orange with evolution of hydrogen. Stirring is continued for about 1/2-hour after hydrogen evolution has substantially ceased. Next, 1 mole of 3,7-(2,2,3,3-tetramethylbutyl)phenothiazine is added with stirring. The reaction mixture is cooled, as necessary, to maintain the mixture at a temperature below about 100°C. The reaction mixture is stirred for about 2 hours, and thereafter, 1 mole of 3,4-dichlorobenzyl chloride is added dropwise with stirring. The reaction mixture is again cooled, as necessary, to maintain the mixture between about 90°C. and about 100°C. while stirring is continued for about 6 hours. Thereafter, 200 milliliters of water is added dropwise, resulting in a reaction mixture which may be characterized as viscous oil. The viscous oil is extracted with 400 milliliters of toluene and washed with 200 milliliters of aqueous 10 percent by weight sodium bicarbonate solution. Washing is repeated, as necessary, using water until the washings have a pH of from about 6 to about 8. Remaining solvents and volatiles are removed by heating to about 150°C. under moderate vacuum to yield an N-(3,4-dichlorobenzyl)-3,7-(2,2,3,3-tetramethylbutyl) phenothiazine product, which may be cooled and recovered as desired.

Preparation of other N-substituted phenothiazine compounds useful herein may be effected in substantially the same manner above-described.

The advantageously, although optionally, included triazole component of the present lubricant may be exemplified by metal passivators such as 3-amino-1,2,4-triazole; 4-amino-1,2,4-triazole; 1,2,3-benzotriazole and alkyl substituted derivatives thereof wherein the alkyl substituents or substituents have, for example, from 1 to about 12 carbon atoms, e.g., 5-methyl-1,2,3-benzotriazole; and 5,5'-methylene bis-(1,2,3-benzotriazole). The triazole component may be included in any effective amount in the range of solubility of the triazole in the composition. Generally, the triazole component may be included in an amount from 0 to about 1 part by weight, and preferably from about 0.01 to about 0.2 parts by weight per 100 parts by weight of the carboxylic acid ester component.

The advantageously, although optionally, included phosphorus-containing acid ester component may be selected from triesters of phosphoric acid with alcohols such as straight and branched chain aliphatic alcohols having from 1 to about 8 carbon atoms. Exemplary of these esters are triethyl phosphate, tributyl phosphate and triisooctyl phosphate. Other suitable phosphoric acid esters include esters of phenol and naphthol. These esters may have from 1 to about 3 C ₁ to C ₁₀ alkyl substitutents on one or more of the aryl moieties. Exemplary of these esters are tricresyl phosphate, triphenyl phosphate and the like. The phosphorus-containing acid ester component may be included in an amount from 0 to about 10 parts by weight, and preferably from about 0.5 to about 5 parts by weight per 100 parts by weight of the carboxylic acid ester component.

The aromatic amine component of the present composition may be a tertiary aromatic amine having attached to its amine nitrogen atom (a) a first aromatic group, (b) a second aromatic group, and (c) an aralkyl group which may be selected from those groups herein denominated R _k and having the general formulas (I), (II), and (III): ##SPC5##

wherein R ₁₂ and R ₁₃ may be selected from chlorine atom, hydrogen atom and methyl group; n is an integer in the range of from 0 to about 4; and R ₁₄ , R ₁₅ , R ₁₆ , R ₁₇ , R ₁₈ , R ₁₉ and R ₂₀ may be selected from hydrogen atom, alkyl, or alkoxy groups having from 1 to about 12 carbon atoms, halo (preferably, fluoro or chloro), nitro, hydroxy and like groups. In general, these tertiary amines unexpectedly cooperate with the N-substituted phenothiazine component in providing improved oxidative stability and increased cleanliness relative to that obtained when either of these two components is included in the absence of the other. The first aromatic group may be alkyl or alkoxy substituted phenyl, while the second aromatic group may be selected from phenyl, alkyl, or alkoxy substituted phenyl, 1-naphthyl, 2-naphthyl, and alkyl or alkoxy substituted 2-naphthyl. The alkyl and alkoxy groups which may be substituted on the first and second aromatic groups may have from about 1 to about 12 carbon atoms, and preferably about 8 carbon atoms. A preferred alkyl group which may be substituted on the aromatic groups is octyl, which may be, for example, 2,2,3,3-tetramethylbutyl. Lubricants of the present invention typically have excellent lubricant qualities in embodiments including 1,1,3,3-tetramethylbutyl substituents on one or more of the first and second aromatic groups of the tertiary aromatic amines.

Suitable tertiary amines include those compounds having a general formula selected from the group consisting of: ##SPC6## wherein R _k is an aralkyl group selected from those groups having the general formulas I, II, and III which are set forth and defined in the preceding paragraph; R ₂₁ , R ₂₂ , R ₂₃ , R ₂₄ and R ₂₅ are selected from the group consisting of hydrogen atom, C ₁ to about C ₁₂ alkyl groups, and C ₁ to about C ₁₂ alkoxy groups such that at least one of R ₂₁ , R ₂₂ , R ₂₃ and R ₂₄ is other than hydrogen; and R ₂₆ and R ₂₇ are selected from the group consisting of C ₁ to about C ₁₂ alkyl groups and C ₁ to C ₁₂ alkoxy groups. A preferred alkyl group in these compounds is octyl group, which may be, for example, 2,2,3,3-tetramethylbutyl. Typically, lubricants of the present invention which include these tertiary amines are characterized with excellent lubricant qualities where R ₂₁ , R ₂₂ , R ₂₆ , and R ₂₇ are 1,1,3,3-tetramethylbutyl groups and R ₂₃ , R ₂₄ , and R ₂₅ are hydrogen atoms. Eminently suitable tertiary amines include those compounds having the general formula: ##SPC7##

wherein R ₂₈ is octyl, for example, ##SPC8## O

and preferably ##SPC9##

and R _k is an aralkyl group which is defined above. It is to be understood that mixtures of suitable tertiary amines may be included in the present composition.

Tertiary amines which may be included herein may be exemplified by N,N-bis-4-octylphenyl-benzylamine, for example, N,N-bis-4-(2,2,3,3-tetramethylbutyl)-phenylbenzylamine, and preferably N,N-bis-4-(1,1,3,3-tetramethylbutyl)-phenyl-benzylamine; N,N-bis-4-octylphenyl-2-phenylethylamine, for example N,N-bis-4-(2,2,3,3-tetramethylbutyl)-phenyl-2-phenylethylami ne, and preferably N,N-bis-4-(1,1,3,3-tetramethylbutyl)-phenyl-2-phenylethylami ne; N-4-octylphenyl-N-1-naphthylbenzylamine, preferably N-4-(1,1,3,3-tetramethylbutyl)-phenyl-N-1-naphthylbenzylamin e; N-4-octylphenyl-N-1-naphthyl-2-phenylethylamine, preferably N-4-(1,1,3,3-tetramethylbutyl)-phenyl-N-1-naphthyl-2-phenyle thylamine; N-4-octylphenyl-N-2-naphthylbenzylamine, preferably N-4-(1,1,3,3-tetramethylbutyl)-phenyl-N-2-naphthylbenzylamin e; and N-4-octylphenyl-N-2-naphthyl-2-phenylethylamine, preferably N-4-(1,1,3,3-tetramethylbutyl)-phenyl-N-2-naphthyl-2-phenyle thylamine.

Other tertiary amines which may be included herein may be exemplified by N,N-bis-4-octylphenyl-2-methylbenzylamine; N,N-bis-4-octylphenyl-4-methylbenzylamine; N,N-bis-4-octylphenyl-2-chlorobenzylamine; N,N-bis-4-octylphenyl-4-chlorobenzylamine; N,N-bis-4-octylphenyl-2,4-dichlorobenzylamine; N,N-bis-4-octylphenyl-3,4-dichlorobenzylamine; N,N-bis-4-octylphenyl-α,α-dichlorobenzylamine; N,N-bis-4-octylphenyl-2-fluorobenzylamine, N,N-bis-4-octylphenyl-4-fluorobenzylamine; N,N-bis-4-octylphenyl-4-nitrobenzylamine; and N,N-bis-4-octylphenyl-2,2-dimethyl-2-phenylethylamine. Preferably, the octyl groups in the preceding amines are 1,1,3,3-tetramethylbutyl groups.

Typically, eminently suitable oxidative stability and better cleanliness are provided when a preferred tertiary amine is included in the present lubricant composition with N-(2,4-dichlorobenzyl)-3,7-dioctylphenothiazine, e.g., N-(2,4-dichlorobenzyl)-3,7-(2,2,3,3-tetramethylbutyl)-phenot hiazine, and preferably N-(2,4-dichlorobenzyl)-3,7-(1,1,3,3-tetramethylbutyl)-phenot hiazine; N-(3,4-dichlorobenzyl)-3,7-dioctylphenothiazine, e.g., N-(3,4-dichlorobenzyl)-3,7-(2,2,3,3-tetramethylbutyl)-phenot hiazine, and preferably N-(3,4-dichlorobenzyl)-3,7-(1,1,3,3-tetramethylbutyl)-phenot hiazine; or the like.

Tertiary amines which may be included in the present composition may be prepared, for example, using the method caught in the Daniels application U.S. Ser. No. 152,372, which is referenced supra in connection with preparation of the N-substituted phenothiazine component hereof, and the method taught in application U.S. Ser. No. 379,835 filed July 16, 1973 under attorney docket number 4230 ( a continuation-in-part of said application Ser. No. 152,372 and assigned to the assignee hereof). The tertiary amine may be included in a minor stabilizing amount, for example, from slightly above 0 (e.g., about 0.1) to about 8 parts by weight or more, typically from about 0.5 part by weight to about 8 parts by weight, and preferably from about 1 to about 4 parts by weight, per 100 parts by weight of carboxylic acid ester component.

The present lubricant composition may further include metal deactivating agents, anti-corrosion agents, anti-rusting agents, anti-foaming agents, dyes, thickening agents, additional anti-oxidants and other suitable agents known in the art for use in ester-containing lubricants.

The present method for lubricating includes contacting a surface to be lubricated with the improved composition of this invention. Typically, surfaces of two parts which may be moved relatively to each other in a zone of near-contact are lubricated by this method. The lubricant may be placed in the zone in a manner such that the parts may be moved relatively with substantially no surface-to-surface contact. The lubricant may be circulated through the zone, if desired. In many instances it is preferred to circulate the lubricant along a flow path such that lubricant which may be frictionally heated flows from a near-contact zone to a heat sink from which cooled lubricant may be returned to the near-contact zone. Where circulation of the lubricant is desired any suitable circulation means may be used. In other applications highly desirable lubrication may be effected by merely applying a suitable amount of the lubricant to a surface to be lubricated.

The present invention will be further illustrated by the following non-limiting examples. In this description, including the examples which follow, all parts given are by weight unless indicated otherwise.

EXAMPLES 1 to 10A

Liquid lubricant compositions were prepared by uniformly mixing the various components in the amounts indicated in Table I below. The compositions of Examples 1 to 6 inclusive were formulated including either phenothiazine or 3,7-dioctylphenothiazine, as indicated. These compounds have been used in prior art attempts to enhance oxidative stability of ester base lubricants. The lubricant compositions of Examples 7 to 10 inclusive are embodiments of the present invention. The composition of Example 10A was prepared for comparative purposes more fully described below.

TABLE I ____________________________________________________________ ______________ Example No. and Approximate Parts by Weight Component 1 2 3 4 5 6 7 8 9 10 10A ____________________________________________________________ ______________ Isooctylisodecyl adipate 100 100 100 100 100 100 100 100 100 100 100 Tricresyl phosphate 1 1 1 1 1 1 1 1 1 1 1 Phenothiazine 0.5 0.5 0.5 0.5 -- 0.5 -- -- -- -- -- 3,7-Dioctylphenothiazine (1) -- -- -- -- 1.0 -- -- -- -- -- -- N-(2,4-dichlorobenzyl)- (2) -- -- -- -- -- -- 1.5 -- -- -- -- 3,7-dioctylphenothiazine N-(3,4-dichlorobenzyl)- (3) -- -- -- -- -- -- -- 1.5 1.5 1.5 -- 3,7-dioctylphenothiazine p,p'-dioctyldiphenylamine -- 2.0 2.0 4.0 2.0 2.0 2.0 2.0 2.0 2.0 3-amino-1,2,4-triazole -- -- 0.05 0.05 0.05 -- 0.05 0.05 -- -- 0.05 4-amino-1,2,4-triazole -- -- -- -- -- 0.05 -- -- 0.05 -- -- 1,2,3 benzotriazole -- -- -- -- -- -- -- -- -- 0.05 -- ____________________________________________________________ ______________ (1), (2), (3) The octyl groups in these compounds were 1,1,3,3-tetramethylbutyl groups.

These compositions were tested for corrosiveness and oxidative stability. The test included placing 0.032 inch × 1 inch × 1 inch metal test specimens in glass test tubes and adding 100 milliliter samples of the various compositions to cover the test metals. The samples were heated to a substantially constant temperature of about 347°F, and thereafter 5 liters per hour of clean dry air was flowed upwardly through the liquid compositions. The metals used included magnesium, aluminum, iron, copper and electrolytic grade silver. At the end of a 72 hour testing period, the air flow was terminated and the metal test squares were removed from the compositions, washed in 1,1,1-trichloroethane, air dried, and thereafter weighed. Metal weight changes from before to after the test, expressed in milligrams per square centimeter of metal surface, are shown in Table II for the various lubricant compositions.

The test included also measuring kinematic viscosity at 100°F of the various compositions tested, before and after testing, using the procedure of ASTM Standard D 445. The results are given below in Table II as percent increase in viscosity. The changes in acid values as determined by the procedure of ASTM D 664 are also shown in Table II. The acid values used for calculating the changes were measured by potentiometric titration with potassium hydroxide to an end point of pH 11 using the procedure of ASTM Standard D 664. The compositions were observed and rated for sludge content at the end of the 72 hour oxidation corrosion tests. A sludge rating of nil means essentially no sludge was observed, while ratings of light, moderate, heavy, etc., were assigned for increasing amounts of observed sludge.

The observed absence of sludge in those compositions of the invention which are illustrated by Examples 7 to 10 illustrates improved cleanliness and increased resistance to oxidation of these compositions relative to the compositions of Examples 1 to 4 and 6 containing phenothiazine and no N-substituted phenothiazine. The data shows that relative to the 3,7-dioctylphenothiazine-containing composition of Example 5, the compositions of Examples 7 to 10 exhibited resistance to oxidation which ranged from generally equivalent to better.

TABLE II ____________________________________________________________ ______________ Sample of Lubricant Metal Weight Change (1) Acid Value Viscosity Increase Sludge Composition milligrams per square centimeter Increase (2) Percent (at 100°F) Rating ____________________________________________________________ ______________ Mg Al Fe Cu Ag Example 1 +0.031 +0.023 +0.031 +0.054 +0.062 2.0 2.0 Very Heavy Example 2 +0.023 -0.023 +0.015 -1.123 N.C. 2.9 8.7 Heavy Example 3 -0.046 -0.054 -0.015 -0.046 -0.039 1.1 5.6 Moderate Example 4 -0.031 -0.015 -0.031 -0.046 -0.039 1.3 7.9 Light Example 5 +0.010 +0.015 +0.015 +0.023 -0.010 1.0 4.9 Nil Example 6 N.C. +0.010 +0.023 -0.023 +0.010 1.1 7.7 Moderate Example 7 N.C. N.C. +0.015 -0.031 +0.010 1.6 4.6 Nil Example 8 -0.015 -0.010 +0.010 -0.015 -0.010 1.5 4.6 Nil Example 9 +0.023 +0.031 +0.023 -0.015 -0.015 1.5 4.3 Nil Example 10 +0.015 -0.021 +0.015 -0.015 -0.010 1.6 5.0 Nil Example 10A -0.015 -0.010 +0.010 -0.023 -0.010 1.7 5.0 Moderate ____________________________________________________________ ______________ (1) A plus sign (+) signifies gain; a minus sign (-) signifies loss; N.C. signifies substantially no change in weight. (2) Milligrams of potassium hydroxide per gram of composition.

EXAMPLES 11 to 14

Dry air was bubbled through an amount of isooctylisodecyl adipate having a temperature of 200°F until thiosulfate titration data for samples of the ester showed a peroxide content of 20 milliequivalents of O ₂ per kilogram of the ester. Aeration time was about 2 hours. Observations of the ester before and after aerating evidenced substantially no visible change in the ester. After cooling to about 80°F, portions of the peroxide-containing ester were used for preparing compositions including the components in the amounts shown in Table III.

TABLE III ______________________________________ Component Example No. and Approximate Parts by Weight ______________________________________ 11 12 13 14 Isooctylisodecyl adipate (1) 100 100 100 100 Tricresyl phosphate 1 1 1 -- N-(3,4-dichlorobenzyl)- 1.5 -- -- -- 3,7-dioctylphenothiazine 3,7-dioctylphenothiazine -- 1.0 -- -- Phenothiazine -- -- 0.5 -- p,p'-dioctyldiphenylamine 2.0 2.0 2.0 -- 3-amino-1,2,4-triazole 0.05 0.05 0.05 -- ______________________________________ (1) including 20 milliequivalents of peroxide per kilogram as determined by iodometric titration

200-milliliter samples of these compositions were tested for storage stability using an accelerated storage test. The samples were placed in 400 ml. glass beakers and stored for 1 week in contact with air at 160°F in a static air oven. At the end of 1 week, observation of the Example 11 sample containing N-(3,4-dichlorobenzyl)-3,7-dioctylphenothiazine showed that this composition remained free from insolubles while retaining its pre-storage clearness and brightness. Results of titration tests showed substantially no change in peroxide content. Observation of the 3,7-dioctylphenothiazine-containing composition of Example 12 at the end of 3 days showed presence of substantial amounts of undesirable flocculent precipitate. The phenothiazine-containing composition of Example 13 exhibited substantial darkening at the end of 1 week. While the sample of the Example 14 composition consisting solely of peroxide-containing ester underwent no appreciable darkening, tests showed an unacceptably large increase in peroxides at the end of 1 week storage.

Relative to the other compositions tested, the N-(3,4-dichlorobenzyl)-3,7-dioctylphenothiazine containing composition of Example 11 exhibited no change from its original appearance and exhibited decreased corrosiveness and improved resistance to oxidation.

EXAMPLES 15 to 26

Components in the amounts indicated in Table IV are uniformly mixed to form lubricant compositions of the present invention. ##SPC10##

These lubricant compositions are tested using the procedure described for Examples 1 to 10A. Although relative to the Example 8 composition minor variations are observed in viscosity change, acid value change, and weight change for the various metal specimens, substantially no sludge is observed for the compositions of Examples 15 to 26.

EXAMPLES 27 to 33

The following compositions were prepared by uniformly mixing the various components in the amounts indicated in Table V below.

TABLE V ____________________________________________________________ ______________ Example No. and Approximate Parts by Weight Component 27 28 29 30 31 32 33 ____________________________________________________________ ______________ Isooctylisodecyl adipate 100 100 100 100 100 100 100 N-(2,4-dichlorobenzyl)3,7-(1,1,3,3- 1.5 -- -- -- 1.5 -- -- tetramethylbutyl)-phenothiazine N-(3,4-dichlorobenzyl)3,7-(1,1,3,3- -- 1.5 -- -- -- 1.5 1.5 tetramethylbutyl)-phenothiazine N,N-bis-4-(1,1,3,3-tetramethybutyl)- -- -- 2.5 -- 2.5 2.5 -- phenylbenzylamine N,N-bis-4-(1,1,3,3-tetramethylbutyl)- -- -- -- 2.6 -- -- 2.6 phenyl-2-phenylethylamine Tricresyl phosphate 1.0 1.0 1.0 1.0 1.0 1.0 1.0 3-Amino-1,2,4-triazole 0.05 0.05 0.05 0.05 0.05 0.05 0.05 ____________________________________________________________ ______________

These compositions were tested for corrosiveness and oxidative stability using the procedure of Examples 1 to 10A. The observed absence of sludge in those compositions of the invention which are illustrated by Examples 31 to 33 inclusive illustrates cooperative improvements in cleanliness and increased resistance to oxidation of these compositions relative to the compositions of Examples 27 to 30, inclusive, which contain either an N-substituted phenothiazine compound in the absence of a tertiary amine or contain a tertiary amine in the absence of an N-substituted phenothiazine compound. The data for the composition of Example 31 containing N-(2,4-dichlorobenzyl)3,7-(1,1,3,3-tetramethylbutyl)-phenoth iazine and N,N-bis-4-(1,1,3,3-tetramethylbutyl)-phenylbenzylamine shows substantially less sludge formation, relative to that observed for the composition of Example 27 including this N-substituted phenothiazine compound in the absence of this tertiary amine compound, and shows a similar improvement relative to the composition of Example 29 including the tertiary amine in the absence of the N-substituted phenothiazine. A cooperative effect, similar to that exhibited by the Example 31 composition, was observed for the Example 32 composition wherein the 2,4-dichlorobenzyl group of the N-substituted phenothiazine was substituted by its 3,4-dichlorobenzyl isomer, relative to the compositions of Examples 28 and 29. The cooperative effect exhibited by the Example 32 composition is evidenced, in part, by comparison of the negligible amount of sludge observed therefor with the higher amounts of sludge observed for the Example 28 and Example 29 compositions which do not include the N-substituted phenothiazine in conjunction with the tertiary amine. An unexpected cooperative effect was also observed for the Example 33 composition including N-(3,4-dichlorobenzyl)3,7-(1,1,3,3-tetramethylbutyl)-phenoth iazine and N,N-bis-4-(1,1,3,3-tetramethylbutyl)-phenyl-2-phenylethylami ne in that substantially no sludge was observed therefor. In contrast a moderate amount of sludge was observed for the Example 29 composition and an amount of sludge rated heavy was observed for the Example 30 composition, which included this N-substituted phenothiazine in the absence of this tertiary amine, and included this tertiary amine without this N-substituted phenothiazine, respectively. The data shows that at high temperature the compositions of Examples 31 to 33 exhibit excellent suppression of sludge formation, increased resistance to oxidation, and substantial freedom from corrosiveness, rendering them eminently suitable for lubricating. The tests results are shown below in Table VI.

TABLE VI ____________________________________________________________ ______________ Sample of Lubricant Metal Weight Change (1) Acid Value Viscosity Increase Sludge Composition Milligrams per Square Centimeter Increase (2) Percent (at 100°F.) Rating ____________________________________________________________ ______________ Mg Al Fe Cu Ag Example 27 +0.023 +0.046 +0.054 +0.039 +0.054 1.68 1.0 Moderate Example 28 +0.062 +0.092 +0.062 N.C. +0.023 2.20 1.6 Moderate Example 29 +0.031 N.C. N.C. -0.015 -0.062 4.80 10.0 Moderate Example 30 -1.341 -0.046 +0.023 +0.039 +0.015 1.20 6.2 Heavy Example 31 +0.023 N.C. N.C. -0.010 -0.039 1.60 5.0 Nil Example 32 -0.046 +0.031 -0.023 -0.015 -0.054 1.10 4.0 Nil Example 33 +0.010 +0.015 +0.015 +0.023 -0.070 1.17 3.6 Nil ____________________________________________________________ ______________ (1) A plus sign (+) signifies gain; a minus sign (-) signifies loss; N.C. signifies substantially no change in weight. (2) Milligrams of potassium hydroxide per gram of composition.

Samples of the compositions of Examples 31 to 33 are tested, substantially as described in the procedure of Examples 11 to 14, for their performance in the presence of peroxide. All of these compositions exhibit excellent storage stability in this test and show substantially no evidence of formation of insoluble matter in the presence of peroxides at an elevated storage temperature of 160°F for 2 weeks.

EXAMPLES 34 to 44

Liquid lubricant compositions are prepared by uniformly mixing the various components in the amounts indicated in Table VII below. The compositions of Examples 34 to 39 inclusive are formulated including either phenothiazine or 3,7-dioctylphenothiazine, as indicated. These compounds have been used in prior art attempts to enhance oxidative stability of ester base lubricants. The lubricant compositions of Examples 40 to 43 inclusive are embodiments of the present invention. The composition of Example 44 was prepared for comparative purposes more fully described below.

TABLE VII ____________________________________________________________ ______________ Example No. and Approximate Parts by Weight Component 34 35 36 37 38 39 40 41 42 43 44 ____________________________________________________________ ______________ Isooctylisodecyl adipate 100 100 100 100 100 100 100 100 100 100 100 Tricresyl phosphate 1 1 1 1 1 1 1 1 1 1 1 Phenothiazine 0.5 0.5 0.5 0.5 -- 0.5 -- -- -- -- -- 3,7-Dioctylphenothiazine (1) -- -- -- -- 1.0 -- -- -- -- -- -- N-(2,4-dichlorobenzyl)- (2) -- -- -- -- -- -- 1.5 -- -- -- -- 3,7-dioctylphenothiazine N-(3,4-dichlorobenzyl)- (3) -- -- -- -- -- -- -- 1.5 1.5 1.5 -- 3,7-dioctylphenothiazine p,p'-dioctyldiphenylamine -- 2.0 2.0 4.0 2.0 2.0 2.0 2.0 2.0 2.0 3-amino-1,2,4-triazole -- -- 0.05 0.05 0.05 -- 0.05 0.05 -- -- 0.05 4-amino-1,2,4-triazole -- -- -- -- -- 0.05 -- -- 0.05 -- -- 1,2,3 benzotriazole -- -- -- -- -- -- -- -- -- 0.05 -- ____________________________________________________________ ______________ (1), (2), (3) The octyl groups in these compounds are 2,2,3,3-tetramethylbutyl groups.

These compositions are tested for corrosiveness and oxidative stability using the procedure of Examples 1 to 10 A. The compositions are observed and rated for sludge content at the end of the 72 hour oxidation corrosion tests. Tests of the lubricant compositions of Examples 40 to 43 show minor variations in viscosity change, acid value change, and weight change for the various metal specimens, relative to the corresponding data for the compositions of Examples 7 to 10 (see Tables I and II). Substantially no sludge is observed for the compositions of Examples 40 to 43.

Substantially the same results are obtained for the compositions of Examples 34, 35, 36, 37, 38, 39, and 44 as were obtained for the compositions of Examples 1, 2, 3, 4, 5, 6 and 10 A, respectively. (See Tables I and II.)

The observed substantial absence of sludge in those compositions of the invention which are illustrated by Examples 40 to 43 illustrates improved cleanliness and increased resistance to oxidation of these compositions relative to the compositions of Examples 34 to 37 and 39 containing phenothiazine and no N-substituted phenothiazine. The data shows that relative to the 3,7-dioctylphenothiazine-containing composition of Example 38, the compositions of Examples 40 to 43 exhibit resistance to oxidation which ranges from generally equivalent to better.

EXAMPLES 45 to 51

The following compositions are prepared by mixing the various components in the amounts indicated in Table VIII below.

TABLE VIII ____________________________________________________________ ______________ Example No. and Approximate Parts by Weight Component 45 46 47 48 49 50 51 ____________________________________________________________ ______________ Isooctylisodecyl adipate 100 100 100 100 100 100 100 N-(2,4-dichlorobenzyl)3,7-(2,2,3,3- 1.5 -- -- -- 1.5 -- -- tetramethylbutyl)-phenothiazine N-(3,4-dichlorobenzyl)3,7-(2,2,3,3- -- 1.5 -- -- -- 1.5 1.5 tetramethylbutyl)-phenothiazine N,N-bis-4-(2,2,3,3-tetramethylbutyl)- -- -- 2.5 -- 2.5 2.5 -- phenylbenzylamine N,N-bis-4-(2,2,3,3-tetramethylbutyl)- -- -- -- 2.6 -- -- 2.6 phenyl-2-phenylethylamine Tricresyl phosphate 1.0 1.0 1.0 1.0 1.0 1.0 1.0 3-Amino-1,2,4-triazole 0.05 0.05 0.05 0.05 0.05 0.05 0.05 ____________________________________________________________ ______________

These compositions are tested for corrosiveness and oxidative stability using the procedure of Examples 1 to 10A. The observed absence of sludge in those compositions of the invention which are illustrated by Examples 49 to 51 inclusive illustrates cooperative improvements in cleanliness and increased resistance to oxidation of these compositions relative to the compositions of Examples 45 to 48, inclusive, which contain either an N-substituted phenothiazine compound in the absence of a tertiary amine or contain a tertiary amine in the absence of an N-substituted phenothiazine compound. The data for the composition of Example 49 containing N-(2,4-dichlorobenzyl)3,7-(2,2,3,3-tetramethylbutyl-phenothi azine and N,N-bis-4-(2,2,3,3-tetramethylbutyl)-phenylbenzylamine shows substantially less sludge formation, relative to that observed for the composition of Example 45 including this N-substituted phenothiazine compound in the absence of this tertiary amine compound, and shows a similar improvement relative to the composition of Example 47 including the tertiary amine in the absence of the N-substituted phenothiazine. A cooperative effect, similar to that exhibited by the Example 49 composition, is observed for the Example 50 composition wherein the 2,4-dichlorobenzyl group of the N-substituted phenothiazine is substituted by its 3,4-dichlorobenzyl isomer, relative to the compositions of Examples 46 and 47. The cooperative effect exhibited by the Example 50 composition is evidenced, in part, by comparison of the negligible amount of sludge observed therefor with the higher amounts of sludge observed for the Example 46 and Example 47 compositions which do not include the N-substituted phenothiazine in conjunction with the tertiary amine. An unexpected cooperative effect is also observed for the Example 51 composition including N-(3,4-dichlorobenzyl)3,7-(2,2,3,3-tetramethylbutyl)-phenoth iazine and N,N-bis-4-(2,2,3,3-tetramethylbutyl)-phenyl-2-phenylethylami ne in that substantially no sludge is observed therefor. In contrast a moderate amount of sludge is observed for the Example 47 composition and an amount of sludge rated heavy is observed for the Example 48 composition, which includes this N-substituted phenothiazine in the absence of this tertiary amine, and includes this tertiary amine without this N-substituted phenothiazine, respectively. The data shows that at high temperature the compositions of Example 49 to 51 exhibit excellent suppression of sludge formation, increased resistance to oxidation, and substantial freedom from corrosiveness, rendering them eminently suitable for lubricating. Substantially the same results are obtained for the compositions of Examples 45, 46, 47, 48, 49, 50 and 51 as were obtained for the compositions of Examples 27, 28, 29, 30, 31, 32 and 33, respectively. (See Tables V and VI.)

Samples of the compositions of Examples 49 to 51 are tested, substantially as described in the procedure of Examples 11 to 14, for their performance in the presence of peroxide. All of these compositions exhibit excellent storage stability in this test and show substantially no evidence of formation of insoluble matter in the presence of peroxides at an elevated storage temperature of 160°F for 2 weeks.

It will be apparent to those skilled in the art that compositions of the present invention exhibit cooperative activity respecting improvements in cleanliness and oxidative stability not only where the amine component is a tertiary amine, but also where a secondary amine is included. For example, the data of Tables II and VI show that the composition of Example 7 exhibits in use, inter alia, substantially less sludge formation (Table II) than one skilled in the art would expect in view of that observed for the composition of Example 10A (Table II) and that observed for the composition of Example 27 (Table VI). Desirable cooperative effect is further illustrated, for example, by the improved sludge rating for the composition of Example 8 (Table II), relative to the sludge rating for the composition of Example 10A (Table II) and to that for the composition of Example 28 (Table VI).

EXAMPLE 52

A lubricant composition illustrating an aspect of the present invention wherein the amine component is a secondary aromatic amine was prepared by uniformly mixing the various essential and optional components in the amounts indicated below:

Approximate Component Parts by Weight ______________________________________ Essential Isooctylisodecyladipate 100 N-(2,4-dichlorobenzyl)-3,7-(1,1,3,3- tetramethylbutyl)phenothiazine 0.5 4,4'-(1,1,3,3-tetramethylbutyl)- diphenylamine 2.0 Optional Tricresylphosphate 1.0 5,5'-methylene-bis-(1,2,3-benzotriazole) 0.01 ______________________________________

This lubricant composition will be referred to hereinafter as Lubricant A.

EXAMPLE 53

A lubricant composition illustrating an aspect of the present invention wherein the amine component is a tertiary aromatic amine was prepared by uniformly mixing the various essential and optional components in the amounts indicated below:

Approximate Component Parts by Weight ______________________________________ Essential Isooctylisodecyladipate 100 N-(2,4-dichlorobenzyl)-3,7-(1,1,3,3- tetramethylbutyl)-phenothiazine 0.5 N,N-bis-4-(1,1,3,3-tetramethylbutyl)- phenyl-benzylamine 2.5 Optional Tricresylphosphate 1.0 5,5'-methylene-bis-(1,2,3-benzotriazole) 0.01 ______________________________________

This lubricant composition will be referred to hereinafter as Lubricant B.

EXAMPLE 54

A composition not within the present invention was prepared by uniformly mixing the various components in the amounts indicated below:

Approximate Component Parts by Weight ______________________________________ Isooctylisodecyladipate 100 N-benzyl-3,7-dioctylphenothiazine (1) 0.44 4,4'-(1,1,3,3-tetramethylbutyl)diphenylamine 2.0 Tricresylphosphate 1.0 5,5'-methylene-bis-(1,2,3-benzotriazole) 0.01 ______________________________________ (1) The octyl groups in this compound are 1,1,3,3-tetramethylbutyl groups.

This composition will be referred to hereinafter as Lubricant C.

The N-substituted phenothiazine compounds of Examples 52 to 54 were prepared using the procedure of the previously noted U.S. patent application, Ser. No. 152,372. Tests showed that the melting point for the N-substituted phenothiazine compound included in Lubricant A and Lubricant B was 115° to 117°C. and that for the N-substituted phenothiazine compound included in Lubricant C was 123° to 125°C, indicating substantial purity for both N-substituted phenothiazine products.

EXAMPLE 55

Portions of Lubricant A, Lubricant B, and lubricant C were tested for corrosiveness and oxidative stability at 347°F using the procedure of Example 1 to 10A. After the 72 hour oxidation corrosion test period, the lubricants were filtered at 347°F through a 10 micron filter and the sludge retained by the filter was dried, weighed, and calculated as milligrams of sludge per 100 milliliters of lubricant. Data for acid value increase, percent increase in viscosity, and metal weight change show that Lubricants A and B, which illustrate lubricants of the present invention, are characterized with a balance of resistance to oxidation and freedom from corrosiveness which is in a range from generally as good as to better than the balance observed for Lubricant C. The substantially better performance shown by Lubricants A and B respecting aluminum is especially important in lubricant applications in the field of lightweight engine assemblies. The amount of filter retained sludge for Lubricant A and Lubricant B was in a range from about 15 to 90 percent less than that for Lubricant C, illustrating substantially better cleanliness, and increased resistance to oxidation for lubricants of the present invention. The test data are shown below in Table IX.

TABLE IX ____________________________________________________________ ______________ Sample of Lubricant Metal Weight Change (1) Acid Value Viscosity Increase Sludge Composition Milligrams per Square Centimeter Increase (2) Percent (at 100°F.) m.g./100 ____________________________________________________________ ______________ ml. Mg Al Fe Cu Ag Lubricant A -0.023 -0.007 N.C. -0.039 -0.015 1.87 5.6 12.1 Lubricant B -0.015 N.C. N.C. -0.015 -0.023 2.00 3.6 1.7 Lubricant C -0.015 -0.015 N.C. -0.031 -0.023 1.30 4.0 14.3 ____________________________________________________________ ______________ (1) A plus sign (+) signifies gain; a minus sign (-) signifies loss; N.C. signifies substantially no change in weight. (2) Milligrams of potassium hydroxide per gram of composition. (3) Milligrams of sludge, dry basis, retained on 10 micron filter pe 100 milliliters of filtered lubricant (after visual observation these lubricants were given a sludge rating of nil)

The following example illustrates the improved performance of the present lubricant compositions at still higher temperatures.

EXAMPLE 55A

Portions of Lubricant A, Lubricant B, and Lubricant C were tested for oxidation stability and cleanliness using the Alcor High Temperature Deposition Test with a "test" temperature of 525°F. In this test, a lubricant composition being tested is circulated for a 48-hour period through an Alcor Deposition Tester, Model HTDT 1003, manufactured by Alcor, Inc., San Antonio, Texas. The Alcor Tester includes a Type 446 stainless steel tube having a heated section 10 inches in length, a lower end of which is electrically heated to and maintained at 525°F. for the first 2 hours of the test. Thereafter, the electrical power input to the metal tube is maintained at a substantially constant value of about 1,000 watts. The lubricant is circulated from a sump-cooler at a substantially constant rate of 300 milliliters per minute using a suitable pump driven by constant speed drive means and rated for high temperature service. Air saturated with water is injected, at a rate of about 1,000 milliliters (200°F., 14.7 pounds per square inch, absolute) per minute, into the lubricant at a location in the lubricant flow path in advance of the heated tube. The lubricant-air mixture enters the tube zone near the lower end of the tube and flows upwardly adjacent the heated tube. After discharging from the tube zone, air is vented and the lubricant returns to the sump-cooler, associated with which is a 100 mesh (U.S. Standard) filter screen disposed in a conduit connecting the sump outlet with the pump inlet.

The power input simulates the frictional heat imparted to lubricants in high-temperature lubrication of bearings in heavy duty applications such as high speed gas turbine engines in jet aircraft where lightweight materials, e.g., aluminum, are often required. This power input is manifested typically by an increase in lubricant temperature, for example, from about 300°F. at the metal tube section inlet to about 450°F. at the outlet. The temperature near the upper end of the metal tube typically is in the range from 650° to 700°F., depending in part on the specific heat of the lubricant being tested.

Deviations from perfection are measured by a quantity designated Overall Rating which is calculated by summing the tube deposit weight in milligrams plus the filter screen deposit weight in milligrams plus the visual tube evaluation and dividing the resulting sum by two. In this regard, perfection is indicated by an Overall Rating of zero. The terms "tube deposit weight: and filter screen deposit weight" mean the weight of deposits which form during the test on the tube and screen, respectively. The term "visual tube evaluation" means a numerical rating assigned to the lubricant taking into account type of tube deposit and the thickness of the deposit. In general, the type of tube deposits which can be detected in this test are carbon deposits, sludge and varnish. Carbon deposits are classified in this test as flaked, blistered, crinkled, and smooth. The test description generic to all these carbon deposits is a carbonaceous coating which cannot be removed by wiping with a rag. The carbon deposits are further classified in the four following classes corresponding to the descriptions given parenthetically: (I) flaked carbon (broken blisters, peeling), (II) blistered carbon (non-broken blisters, bubbled), (III) crinkled carbon (ridges, not smooth), and (IV) smooth carbon (smooth coating). Sludge type deposits (V) are described as shiny oily emulsions of carbon and oil which can be wiped off with a rag. Varnish type deposits (VI) are described as shiny varnish or lacquerlike coatings.

After the 48-hour test period, each one-inch segment of the 10-inch metal tube is observed for the presence and type of deposit. Thereafter, the thickness of deposit for each of the 10 segments is measured, followed by stripping and weighing the deposits for each segment. A base numerical demerit value is assigned for each segment according to the following scheme, the Roman numerals used herein referring to the various classes of deposits described previously: I-18, II-15, III-12, IV-9, V-6, VI-5, and zero if no deposit is observed. A numerical demerit value for each segment is calculated by adding to the base value a number from 0 to 2, as may be required, according to the description next given. The number 2 is added for carbon deposits (Classes I to IV) where the deposit thickness is more than 3/64 inch and for Class V deposits of more than 1/16 inch. The number 1 is added for Class I to IV deposits where the deposit thickness is from more than 1/64 inch to 3/64 inch inclusive and for Class V deposits in the range from more than 1/32 to 1/16 inch inclusive. For classes and thickness not within The previous description no adjustment is made, i.e., the numerical demerit value is taken to be the base value, with the proviso that where a segment includes portions of two or more different classes or two or more different thicknesses of deposits of the same class, the demerit value for such segment is calculated using a pro tanto modification of the above procedure based on extent of lateral coverage for each such portion, as will be apparent to those skilled in the art. Next, a numerical demerit rating is calculated for each segment by multiplying the numerical demerit value therefor by the deposit weight therefor. The visual tube evaluation rating used in the previously described calculation of the Overall Rating is calculated by adding the numerical demerit ratings for the 10 segments and dividing by 10.

Samples of the test lubricant are taken at the start and conclusion of the test for measuring changes in kinematic viscosity and total acid value. At the conclusion of the test, the metal tube is removed from the test section and after cooling to room temperature, is immersed without agitation in hexane and then allowed to dry at room temperature. The filter is removed, allowed to drain and thereafter dried in air at 200°F. for 1 hour. The dried filter is weighed and the weight of filter deposits is calculated by weight difference.

Data shows that not only are Lubricant A and Lubricant B (lubricants of the present invention) characterized with substantially better Overall Ratings (from 25 to 50 percent better relative to Lubricant C which is outside the present invention), but also with better resistance to high temperature deposit formation in two of the three categories underlying these ratings. In a number of prior attempts to increase resistance to deposit formation in synthetic lubricants at high temperature, substantial losses in oxidation stability have been observed. The test shows that such losses did not occur for the test lubricants illustrating this invention. The test data are shown below in Table X.

Table X ______________________________________ Sample of Lubricant A (1) B (2) C (3) ______________________________________ Overall Rating 20.8 14.0 27.9 Tube deposits, milligrams 6.6 3.1 6.0 Visual tuube evaluation 17.5 14.1 24.5 Filter screen deposits, milligrams 17.6 19.8 24.4 Acid value change (4) 3.02 4.10 4.03 Viscosity change (4) 10.3 12.6 11.4 ______________________________________ (1) Prepared in Example 52 (2) Prepared in Example 53 (3) Prepared in Example 54 (4) See description in Examples 1 to 10 A and Table I

EXAMPLES 56 to 64

The procedure of Example 52 was repeated except that all the N-(2,4-dichlorobenzyl)- 3,7-(1,1,3,3-tetramethylbutyl) phenothiazine was replaced by the following N-substituted phenothiazine components in the amounts indicated:

Approximate N-Substituted Phenothiazine Parts Ex. Component by Weight ______________________________________ 56 N-(2-chlorobenzyl)-3,7-(1,1,3,3- tetramethylbutyl)phenothiazine 0.47 57 N-(4-chlorobenzyl)-3,7-(1,1,3,3- tetramethylbutyl)phenothiazine 0.47 58 N-(3,4-dichlorobenzyl)-3,7-(1,1,3,3- tetramethylbutyl)phenothiazine 0.50 59 N-(α,α-dichlorophenylmethyl)-3,7- (1,1,3,3-tetramethylbutyl)phenothiazine 0.50 60 N-(2-fluorobenzyl)-3,7-(1,1,3,3- tetramethylbutyl)phenothiazine 0.45 61 N-(2-nitrobenzyl)-3,7-(1,1,3,3- tetramethylbutyl)phenothiazine 0.46 62 N-(4-nitrobenzyl)-3,7-(1,1,3,3- tetramethylbutyl)phenothiazine 0.46 ______________________________________

The lubricants of Examples 56 to 62 were tested using the Alcor High Temperature Deposition Test described in Example 55A. The results were substantially the same as the results shown in Example 55A for Lubricant A (the lubricant of Example 52).

EXAMPLES 63 to 65

The procedure of Example 52 was again repeated except that all the 4,4'-(1,1,3,3-tetramethylbutyl)-diphenylamine was replaced by the following secondary amine components in the amounts indicated:

Approximate Example Secondary Amine Component Parts by Weight ______________________________________ 63 4-(1,1,3,3-tetramethylbutyl)- phenyl-1-naphthylamine 1.84 64 4-(1,1,3,3-tetramethylbutyl)- phenyl-2-naphthylamine 1.84 65 4-(1,1,3,3-tetramethylbutyl)- phenyl-1-N-1-(1,1,3,3-tetramethyl)- butyl)-2-naphthylamine 2.47 ______________________________________

The lubricants of Examples 63 to 65 were tested using the Alcor High Temperature Deposition Test described in Example 55A. The results were substantially the same as the results shown in Example 55A for Lubricant A (the lubricant of Example 52).

EXAMPLES 66 to 72

The procedure of Example 53 was repeated except that all the N-(2,4-dichlorobenzyl)-3,7-(1,1,3,3-tetramethylbutyl)-phenot hiazine was replaced by the following N-substituted phenothiazine components in the amounts indicated:

Approximate N-Substituted Phenothiazine Parts Ex. Component by Weight ______________________________________ 66 N-(2-chlorobenzyl)-3,7-(1,1,3,3- tetramethylbutyl)phenothiazine 0.47 67 N-(4-chlorobenzyl)-3,7-(1,1,3,3- tetramethylbutyl)phenothiazine 0.47 68 N-(3,4-dichlorobenzyl)-3,7-(1,1,3,3- tetramethylbutyl)phenothiazine 0.50 69 N-(α,α-dichlorophenylmethyl)-3,7- (1,1,3,3-tetramethylbutyl)phenothiazine 0.50 70 N-(2-fluorobenzyl)-3,7-(1,1,3,3- tetramethylbutyl)phenothiazine 0.45 71 N-(2-nitrobenzyl)-3,7-(1,1,3,3- tetramethylbutyl)phenothiazine 0.46 72 N-(4-nitrobenzyl)-3,7-(1,1,3,3- tetramethylbutyl)phenothiazine 0.46 ______________________________________

The lubricants of Examples 66 to 72 were tested using the Alcor High Temperature Deposition Test described in Example 55A. The results were substantially the same as the results shown in Example 55A for Lubricant B (the lubricant of Example 53).

EXAMPLES 73 to 83

The procedure of Example 53 was again repeated except that all the N,N-bis-4-(1,1,3,3-tetramethylbutyl)-phenylbenzylamine was replaced by the following tertiary amine components in the amounts indicated:

Approximate Parts Example Tertiary Amine Component* by Weight ______________________________________ 73 N,N-bis-4-octylphenyl- 2-methylbenzylamine 2.57 74 N,N-bis-4-octylphenyl- 4-methylbenzylamine 2.57 75 N,N-bis-4-octylphenyl- 2-chlorobenzylamine 2.67 76 N,N-bis-4-octylphenyl- 4-chlorobenzylamine 2.67 77 N,N-bis-4-octylphenyl- 2,4-dichlorobenzylamine 2.85 78 N,N-bis-4-octylphenyl- 3,4-dichlorobenzylamine 2.85 79 N,N-bis-4-octylphenyl- α,α-dichlorobenzylamine 2.85 80 N,N-bis-4-octylphenyl- 2-fluorobenzylamine 2.59 81 N,N-bis-4-octylphenyl- 4-fluorobenzylamine 2.59 82 N,N-bis-4-octylphenyl- 4-nitrobenzylamine 2.57 83 N,N-bis-4-octylphenyl- 2,2-dimethyl-2-phenylethylamine 2.71 ______________________________________ *The octyl groups were 1,1,3,3-tetramethylbutyl groups.

The lubricants of Examples 73 to 83 were tested using the Alcor High Temperature Deposition Test described in Example 55A. The results were substantially the same as the results shown in Example 55A for Lubricant B (the Lubricant of Example 53.)

Dry air was bubbled through an amount of di-2-ethylhexyl adipate having a temperature of 200°F until thiosulfate titration data for samples of the ester showed a peroxide content of 25 milliequivalents of O ₂ per kilogram of the ester. Aeration time was about 2 hours. Observations of the ester before and after aerating evidenced substantially no visible change in the ester. After cooling to about 80°F., portions of the peroxide-containing ester were used for preparing the compositions of Example 84 to 86 which follow.

EXAMPLE 84

A lubricant composition illustrating as aspect of the present invention wherein the amine component is a secondary aromatic amine was prepared by uniformly mixing the various components in the amounts indicated below:

Approximate Component Parts by Weight ______________________________________ Di-2-ethylhexyl adipate 100 N-(2,4-dichlorobenzyl)-3,7-(1,1,3,3- tetramethylbutyl)phenothiazine 1.5 4,4'-(1,1,3,3-tetramethylbutyl)- diphenylamine 2.0 ______________________________________

This lubricant composition will be referred to hereinafter as Lubricant A'.

EXAMPLE 85

A lubricant composition containing a secondary aromatic amine and an N-substituted phenothiazine and not within the present invention was prepared by uniformly mixing the various components in the amounts indicated below:

Approximate Component Parts by Weight ______________________________________ Di-2-ethylhexyladipate 100 N-benzyl-3,7-dioctylphenothiazine (a) 1.32 4,4'-dioctyldiphenylamine (a) 2.0 ______________________________________ (a) The octyl groups in these compounds were 1,1,3,3-tetramethylbutyl groups

This lubricant composition will be referred to hereinafter as Lubricant D.

EXAMPLE 86

A composition not within the present invention was prepared by uniformly mixing the various components in the amounts indicated below:

Approximate Component Parts by Weight ______________________________________ Di-2-ethylhexladipate 100 3,7-dioctylphenothiazine (a) 0.44 4,4'-dioctyldiphenylamine (a) 2.0 ______________________________________ (a) The octyl groups in these compounds were 1,1,3,3-tetramethylbuty groups.

This composition will be referred to hereinafter as Lubricant E.

The N-substituted phenothiazine compounds of Examples 84 and 85 were prepared using the procedure of the previously noted U.S. patent application, Ser. No. 152,372. Tests showed that the melting point range for the N-substituted phenothiazine compound included in Lubricant A' was 115° to 117°C. and that for the N-substituted phenothiazine compound included in Lubricant D was 123° to 125°C., indicating substantial purity for both N-substituted phenothiazine products.

200-milliliter amounts of Lubricant A', Lubricant D and Lubricant E were tested for storage stability using an accelerated storage test. The lubricants were placed in 400 ml. glass beakers and stored for one week in contact with air at 160°F. in a static air oven. Observations of Lubricant D at the end of each day during the week showed that this composition remained free from insolubles while retaining its pre-storage clearness and brightness. Daily observation of Lubricant A' showed at least as good results in these respects relative to Lubricant D. Daily observations of the 3,7-dioctylphenothiazine-containing composition of Lubricant E showed presence of substantial amounts of undesirable flocculent precipitate beginning with day 1 and continuing throughout the test period.

Changes in acid value from the start to the end of the test were determined for these lubricants using the procedure therefor of Examples 1 to 10A. Data shows that Lubricant E had an increase of 4.01 milligrams of potassium hydroxide per gram of lubricant (mg. KOH/g.); Lubricant D, 0.05 mg. KOH/g.; and Lubricant A', 0.03 mg KOH/g. In summary, the data shows that Lubricant A' is characterized with storage stability which is as good as to better than that of Lubricant D containing an N-benzyl-3,7-dioctylphenothiazine and substantially better than that of Lubricant E containing a 3,7-dioctylphenothiazine.

As used herein, including in the claims which follow, halo means a substituent selected from the group consisting of fluoro, chloro and bromo.

As used herein 3,7-(2,2,3,3-tetramethylbutyl) phenothiazine means that compound having formula IV which follows: ##SPC11##

As used herein 3,7-(1,1,3,3,-tetramethylbutyl)phenothiazine means that compound having formula V which follows: ##SPC12##

and it is to be understood that the various N-substituted 3,7-(1,1,3,3-tetramethylbutyl) phenothiazines referred to herein have formula V except that the nitrogen-attached hydrogen atom is replaced by the various arakyl groups or substituted aralkyl groups, as indicated.

As used herein with reference to the amounts of the amine component and the N-substituted phenothiazine component, the term minor stablizing amount means an effective amount of the respective component sufficient to enhance the lubricant composition with respect to at least one of the following: storage stability, cleanliness, oxidative stability, relative freedom from corrosiveness, relative resistance to degradation, relative resistance to oxidation, relative resistance to deposit formation, and equivalents thereof. Such properties or characteristics are often referred to generally in the art by terms such as oxidation stability, inhibition of oxidation, etc., although chemical oxidation is not necessarily involved in every category to which the terms are applied. More simply stated and in view of the foregoing, the term minor stabilizing amount as used herein means an amount effective for enhancing cleanliness and oxidation stability.

Peroxide content is expressed herein in milliequivalrnts of 0 ₂ as determined by iodometric titration.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that various modifications may be made therein without departing from the spirit or scope of the present invention.