US3642630A - Lubricant compositions - Google Patents

Abstract

SYNTHETIC ESTER BASED LUBRICANT COMPOSITIONS CONTAINING MINOR AMOUNTS EACH OF AN N-SUBSTITUTED PHENOTHIAZINE AND A SYMMETRICAL OR ASYMMETRICAL SUBSTITUTED TRIAZINE HAVE GOOD OXIDATION STABILITY OVER A WIDE RANGE OF TEMPERATURES.

Description

United States Patent 3,642,630 LUBRICANT COMPOSITIONS Alexander C. B. MacPhail, Wood River, 11]., and Ian Keddie, Pensby, Wirral, England, assignors to Shell Oil Company, New York, NY.

N0 Drawing. Filed Feb. 24, 1969, Ser. No. 801,785 Claims priority, application Great Britain, Feb. 22, 1968, 8,660/68 Int. Cl. Cltlm 1/38 US. Cl. 252--47.5 7 Claims ABSTRACT OF THE DISCLOSURE Synthetic ester based lubricant compositions containing minor amounts each of an N-su'bstituted phenothiazine and a symmetrical or asymmetrical substituted triazine have good oxidation stability over a wide range of temperatures.

BACKGROUND OF THE INVENTION This invention relates to synthetic ester lubricating oils having exceptional oxidation stability. More particularly it relates to synthetic ester oils containing N-substituted phenothiazines and symmetrical or asymmetrical substituted triazines.

Synthetic lubricants have gained recent prominence in the field of lubrication because of stringent requirements of long life under extreme conditions imposed by certain new applications. Synthetic lubricants have low pour points and desirable viscosity characteristics and can generally be used at temperatures considerably above the decomposition temperature of most mineral oils. These oils have found use in jet aircraft, missiles, and the like Where wide temperature ranges and extreme operating conditions are likely to be encountered. Proper lubrication of aircraft gas turbines, for example, requires ability to function at bulk oil temperatures as low as -65 F. to as high as 450 to 500 F. for said applications.

Although these synthetic lubricants are more stable than mineral oils, they nevertheless undergo oxidation when exposed to air, especially when subjected to elevated temperatures such as occur under normal operation. Oxidation stability is further impaired by dissolution of metals under operating conditions. Dissolved metals seem to catalyze oxidative degradation of the lubricant, thereby substantially shortening its useful life. Additives have traditionally been employed in small concentrations to impart resistance to oxidation to these lubricants. Much research effort has been directed to finding additives or combinations of additives which are effective antioxidants for long periods of time yet which do not impart or cause undesirable side effects such as increased corrosion, viscosity change, discoloration, and so on. Available information regarding mineral oil formulation is generally of little aid in developing successful synthetic lubricants since entirely different side effects are likely to occur under the more extreme conditions to which synthetic lubricants are subjected.

According to the invention, a synthetic ester lubricant having excellent oxidation stability comprises a major amount of a synthetic ester lubricating oil and minor amounts, sufficient to increase the oxidation stability of the oil, of (1) a substituted phenothiazine having the formula 3,6 42,fi3 Patented Feb. 15, 1972 wherein R is selected from the group consisting of alkyl, aryl, alkaryl, aralkyl and cyanoalkyl radicals having from 1 to 12 carbon atoms, and R R R and R are selected from the group consisting of hydrogen and alkyl and alkyoxy radicals having from 1 to 12 carbon atoms; and (2) a substituted triazine selected from the group consisting of symmetrical triazines and asymmetrical triazines having the respective formulas X{ HY XI N N and J wherein X, Y and Z are selected from the group consisting of NH C to C hydrocarbylamino, di-C to C hydrocarbylamino, pyridylamino, di-pyridylamino, C to C hydrocarbyl and pyridyl, and wherein at least one X, Y or Z substituent is an amino grouping, the nitrogen atom of which is attached to the heterocyclic ring.

The N-su-bstituted phenothiazines preferably have one alkyl or alkoxy radical as substituent in each aromatic ring comprising the phenothiazine molecule and 3,7-substitution is most preferred. Preparation of N-substit-uted p'henothiazines is described, for example, in British patent specification No. 873,066. N-substituted phenothiazines which are particularly useful for the purposes of the present invention are N-methyl-3,7-dioctyl phenothiazine,

N-n.butyl-3,7-dioctyl phenothiazine, N-n.octyl-3,7-dioctyl phenothiazine, N-phenyl-3,7-dioctyl phenothiazine, N-tolyl-3,7-dioctyl phenothiazine, N-cyanoethyl-3,7-dioctyl phenothiazine, N-cyanopropyl-3,7-dioctyl phenothiazine, N-cyanobutyl-S,7-dioctyl phenothiazine, N-benzyl-3,7-dioctyl phenothiazine, N-benzyl-3,7-dibutyl phenothiazine, N-benzyl-3,7-diisopropoxy phenothiazine, N-benzyl-3,7-dibutoxy phenothiazine and mixtures thereof.

It is anticipated that a wide range of triazine compounds may be used in conjunction with the phenothiazines for the purpose of the present invention, the choice of substituents being limited by requirements of solubility in the ester. It is envisaged that the triazines giving the best combination of solubility and activity will be those having the general formulae as follows- Types 1, 2 and 3 are 1,3,5-triazines referred to as symmetrical or s-triazines.

R R. R3

\ I Re i N R Rs R N N R4 Typc7 Types 4 to 8 are 1,2,4-triazines referred to as asymmetrical or as-triazines.

R may be H, C C hydrocarbyl, or pyridyl R may be H, C -C hydrocarbyl, or pyridyl R may be H, C C hydrocarbyl, or pyridyl R may be H, C -C hydrocarbyl, or pyridyl R may be H, C C hydrocarbyl, or pyridyl R may be H, C C hydrocarbyl, or pyridyl R to R may be C to C hydrocarbyl, C to C hydrocarbylamino, pyridyl or pyridylamino, where the term hydrocarbyl is intended to mean a radical formed from a hydrocarbon by removal of a hydrogen atom. All hydrocarbyl groups within the claimed ranges which are free of aliphatic unsaturation are operable, whether they are alkyl, aryl, alkaryl, aralkyl, cycloalkyl, single or multi-ring, straight chain or branched.

Type 8 Examples of triazines which may be used in accordance with the invention are as follows:

2-a1nino-4-anilino-6-benzylamino-1,3,5-triazine 2-amino-4-anilino-6-dibutyl amino-1,3,5-triazine 2-arnino-4-anilino-6-benzylamino-1,3,5-triazine 2-azido4-ethyl amino-6-t-butyl amino-1,3,5-triazine 2-di isobutylamino-4-octadecyl amino-6-phenyl- 1,3,5-triazine 2,4-di-n-butyl amino-6-anilino-1,3,5-triazine 2-benzylamino-4,6-dianilino-1,3,5-triazine 2-amino-4-butyl amino-6-phenyl-1,3,5-triazine 2-amino-4,6-di-anilino1,3,5-triazine 3-amino-5,6-di-phenyl-1,2,4-triazine 2-amino-4-n-butylamino-6-phenyl-1,3,5-triazine 2-di isobutylamino-4-dodecyl-amino-6-pheny1- 1,3,5-triazine 2,4-bis(n-butylamino)-6-phenyl-1,3,5-triazine 2-cyclo hexyl-4-hexadecylamino-6-(di-n-butylamino)- 1,3,5-triazine 2-amino-4-sec-butylamino-6-phenyl-1,3,5-triazine 2,4-bis(di-n-butylamino)6-N-cyano-ethylamino- 1,3,5-triazine 2,4-bis(sec-butyl amino)-6-phenyl-1,3,5-triazine Z-methyloctyl amino-4,6-bis(di-n-butylamino)- 1,3,5-triazine 2,4,6-tris(n-butylamino)-1,3 ,S-triazine 2-anilino-4,6-bis (ethylamino) -1,3,5-triazine 2-anilino-4,6-bis(n-butylamino)-1,3,5-triazine 2-phenyl-4- (di-n-butylamino) -6-octadecyl amino- 1,3,5-triazine 2-n-butylamino-4,6-dianilino-1,3,5-triazine 2-dioctylamino-4,6-bis (diethylamino)-1,3,5-triazine 3-amino-5,6-diphenyl-1,2,4-triazine 5-amino-3,6-diphenyl-1,2,4-triazine 6-amino-3,5-diphenyl-1,2,4-triazine 3,5-bis(amino)-6-phenyl-1,2,4-triazine 3,5-bis(n-butylamino)-6-phenyl-1,2,4-triazine 5,6-bis amino-3-pheny1-1,2,4-triazine It is as yet not fully understood by what mechanism the triazine compounds act in improving the antioxidant effect of the phenothiazines, but it is thought that the triazine compounds exhibit metal deactivating or passivating properties as well as behaving as antioxidants.

Preferably the phenothiazines and triazines of the present invention are each employed in a proportion of 0.005 to 10% by weight, more preferably in a proportion of 0.01 to 5% by weight based on the whole composition.

Esters suitable as the ester base in the composition of the present invention are simple esters, complex esters, polyesters or mixtures thereof to which may be added thickeners, depending upon the viscometric properties desired for the composition and the temperature conditions under which it is to be used. By simple ester is meant an ester formed between an aliphatic dicarboxylic acid and an aliphatic monohydric alcohol, preferred simple esters being formed from an aliphatic discarboxylic acid containing from 6 to 10 carbon atoms in the molecule and a branched chain monohydric alcohol containing from 6 to 12 carbon atoms in the molecule, especially those alcohols having no hydrogen on the beta carbon atom. Examples of simple esters useful for the purposes of the present invention are diiso-octyl sebacate, di(2-ethyl hexyl) sebacate, diiso-octyl azelate, diisodecyl azelate, di- (3,5,5-trimethyl hexyl) adipate, 2-ethyl hexyl 3,5,5-trimethyl hexyl sebacate and 2,2,4-trimethyl pentyl azelate.

By complex ester is meant an ester formed from various combinations of an aliphatic dicarboxylic acid, a glycol or polyglycol and either or both of an aliphatic monohydric alcohol and an aliphatic mono-carboxylic acid. Some typical complex ester structures are represented by A(DG),,M and MG(DG) M wherein A, D, G and M represent the esterification residues from an aliphatic monohydric alcohol, an aliphatic dicarboxylic acid, a glycol or polyglycol and an aliphatic monocarboxylic acid respectively and n is a number from 1 to 6. Examples of typical starting materials suitable for the preparation of such esters are 2-ethyl butyl alcohol, 2-ethyl hexyl alcohol, caproic acids, pelargonic acid, capric acid, neopentyl glycol, ethylene glycol, propylene glycol, polyglycols such as polyethylene glycols, sebacic acid, adipic acid, azelaic acid and pimelic acid.

By polyesters is meant esters made from aliphatic alcohols having therein at least 3 hydroxyl groups, for example esters made from trimethylol propane, e.g. trimethylol propane, tripelargone, tetra esters such as the pentaerythritol tetra esters or the dimers or trimers of the same and dipentylerythritol esters, for example esters sold under the Registered Trademarks Hercolube A and Hercolube F, all esters being fatty acid esters. Preferably each fatty acid radical of the ester contains from 4 to 18 carbon atom and more preferably from 6 to 14 carbon atoms.

As thickeners there may be used polymers of esters of acrylic or an alkyl substituted acrylic acid, for example lauryl methacrylate, or an ether or a polyoxyalkylene glycol of the general formula R O(R O),,R wherein R is an alkyl group, R is hydrogen or an alkyl group, R is an alkylene group of 2 to 4 carbon atoms and n is a number greater than unity. Suitable compounds are marketed under the registered trademark Ucon, specific examples being LB 385, LB 525, LB 625. Also suitable are copolymers of propylene oxide and ethylene oxide marketed under the Registered Trademark Oxilube, e.g. Oxilube 140. The thickeners may be used in proportions up to 40% by weight calculated on the final lubricant composition depending upon the viscometric properties required for said lubricant.

The ester base compositions of the present invention may additionally contain extreme pressure additives, additional antioxidants, metal deactivators, anti-corrosion agents, anti-foaming agents, dye stuffs and other additives known to be suitable for use with ester base lubricant formulations.

As examples of extreme pressure additives are mentioned esters of acids of phosphorus particularly triphenyl phosphorothionate, tritolyl phosphorothionate and trixylyl phosphorothionate; phosphate esters e.g. triphenyl phosphate and tritolyl phosphate may also be used. Another class of phosphorus containing extreme pressure additives which may be usefully employed in the ester base compositions of the present invention are diaryl haloalkyl phosphates which are described and claimed in British Pat. No. 1,035,984. Yet another class of extreme pressure additives which may usefully be employed in the present ester compositions are the chlorinated dior polyphenyls i.e. diphenyls, terphenyls, higher polyphenyls or mixtures thereof containing at least one chlorine atom attached directly to each benzene nucleus for example chlorinated dior poly-phenyls sold under the Registered Trademark Arochlor. Still another suitable class of extreme pressure additives for the present use are substituted oxetane polymers, i.e. polymers prepared from oxetanes having the formula:

X CH:

wherein one X is chlorine or bromine and the others are chosen from hydrogen, chlorine or bromine e.g. 3,3-bis (chloromethyl) oxetane. Further information concerning oxetane polymers may be found in UK. Pat. No. 964,672.

A class of extreme pressure additives which are particularly useful for conferring extra resistance to extreme pressure conditions are the mono chloro methyl phosphonic acid salts of tertiary alkyl primary amines, for example, the mono chloro methyl phosphonic acid salts of C tertiary alkyl primary amines.

Additional anti-oxidants suitable for use in compositions of the present invention are alkylated phenols e.g. 2,6-ditertiary butyl-4-methyl phenol and alkylated bis phenols e.g. 4,4'-methylene bis (2,6-ditertiary butyl phe- 1101).

As metal deactivators and or passivators and corrosion inhibitors which may be employed in compositions according to the present invention there may be used a wide range of compounds which can be employed according to the metal or metals with which the compositions will come into contact. Materials particularly suitable when the metals to be contacted are copper, copper alloy or silver are the triazoles, e.g. 1,2,3-benztriazole, methyl- 1,2,3 benztriazole, 3-amino-5-methyl-1,2,4-triazlole, especially 3-amino-5-phenyl-1,2,4-triazole, 3-amino-5-p-yridyl- 1,2,4-triazole, 3-amino-5-anilido-1,2,4-triazole and 5,5'-diamino 3,3'-bi-(1,2,4-triazole), up to about 1% preferably about 0.5% wt. of these materials being useful. Also useful when the metals are copper, cadmium, silver and magnesium for example, are similar weights of pyridylamines, particularly di pyridylamines, e.g. 2,2-dipyridylamine. Small proportions e.g. from 0.01 to 0.2% wt. of sebacic, azelaic or adipic acid are also useful additives for the protection of lead while metal petroleum sulphonates are useful rust inhibitors.

Suitable anti-foaming agents are the poly-dirnethyl siloxanes having viscosities from 100 to 100,000 c./s. at C.

The lubricant compositions of the present invention are further illustrated by the following examples which are not intended to limit the invention to the particular compounds or compositions described.

EXAMPLE I To illustrate the efiicacy of the additive combination of the invention the following compositions were prepared and subjected to the Rolls Royce Blown Oxidation Test. In this test, 250 ml. per minute of air saturated with water vapor, are bubbled under controlled conditions through a 50 gram sample of ester base composition. Deterioration of the composition due to oxidation is then measured in terms of toluene insolubles, volatility, change in kinematic viscosity (VK) and increase in acidity...Test conditions and results are presented in Table I. The base stock employed in the preparation of all of the compositions shown was a mixture of approximately 70% by weight of Hercolube A (pentaerythrityl esters of saturated fatty acids of C average chain length) and by weight Hercolube F (dipentaerythrityl esters of saturated fatty acids of C average chain length).

TABLE I Rolls Royce a blown oxidation test (1001): Conditions 192 hrs. at 225 0 Change in VK at Toluene Volatility 210 F., Increase in Composition insolubles, los percent acid value, number percent wt. percent wt. increase mg. KOH/g.

l Solid 2 Solid 3 0.20, 0. 23 40, 41 +35, +40 1.15, 1.80

B The words Rolls Royce" are a registered trademark.

The data presented in Table I are indicative of the surprising results obtained by use of the additive combination of the invention.

Compositions 1 and 2 containing each of the additives separately, completely solidified under the extreme conditions of the test. In comparison composition 3 containing the additive combination of the invention displayed remarkable oxidation stability.

EXAMPLE II To further demonstrate the effectiveness of the ester base compositions of the invention, a series of formulations containing the phenothiazine-triazine additive combination were compared to compositions containing a well known prior art antioxidant in place of the triazine. These formulations and test results are shown in Table II. The base stock employed in preparing these compositions was the same as that used in Example I.

Composition 4-Base stock plus 1.7% wt. N-benzyl 3,7- dioctyl phenothiazine and 1.5% wt. phenyl-alpha-naphthylamine Composition 5-Base stock plus 1.7% wt. N-benzyl 3,7- dioctyl phenothiazine and 2.0% wt. phenyl-alpha-naphthylamine Composition 6-Base stock plus 1.7% wt. N-benzyl 3,7- dioctyl phenothiazine and 2.0% Wt. 2-azido-4-ethylamino-6-t-butylamino-l,3,5-triazine.

Composition 7-Base stock plus 1.7% wt. N-benzyl 3,7- dioctyl phenothiazine and 2.0% wt. 2-amino-4-butylamino-6-phenyl-l,3,5-triazine Composition 8Base stock plus 1.7% wt. N-benzyl 3,7- dioctyl phenothiazine and 2.0% wt. 2 amino-4,6-dianilino-1,3,5-triazine Composition 9--Base stock plus 1.7% wt. N-benzyl 3,7- dioctyl phenothiazine and 2.0% wt. 3-amino-5,6,-diphenyl-l,2,4-triazine Composition 10-Base stock plus 2.0% wt. N-benzyl 3,7- dioctyl phenothiazine and 1.0% wt. 2-benzylamine-4,6- dianilino-1,3,5-triazine Composition l1Base stock plus 2.0% wt. N-benzyl 3,7- dioctyl phenothiazine and 1.0% 2-anilino-4,6-bis (ethylamino)-1,3,5-triazine Composition 12Base stock plus 2.0% N-benzyl 3,7-dioctyl phenothiazine and 1.0% 2-amino-4-anilino-6-benzylamine-l,3,5-triazine TABLE II Rolls Royce blown oxidation test (100): Conditions 192 hrs. at 225 C.

Toluene Volatility Change in Increase in Composition insolubles, loss, VK at acid value, number percent wt. percent wt. at 210 F., mg. KOH/g.

From Table II it is clear that although the formulations of the invention give slightly greater toluene insoluble values, they are significantly superior to the compositions containing the prior art antioxidant in respect to the classical oxidation stability factors such as increase in acid value and 210 F. VK change.

EXAMPLE III In order to illustrate still further the superior oxidation stability characteristics of formulations according to the present invention, several of the compositions were subjected to a modified version of the above test wherein the oxidation is carried out at 250 C. for 22 hrs. The results of this series of tests is given in Table III, wherein the most important factor, the percent change in viscosity at 100 F. is compared.

TABLE III Blown oxidation test: 22 hrs. at 250 C.

Composition No.: Percent change in VK at 100 F.

We claim as our invention:

1. A lubricant composition comprising a major amount of a synthetic ester lubricating oil and a combination of 0.005 to 10% Wt. each of (l) a substituted phenothiazine having the formula wherein R is selected from the group consisting of alkyl, aryl, alkaryl, aralkyl and cyanoalkyl radicals having from 1 to 12 carbon atoms, and R R R and R are selected from the group consisting of hydrogen and alkyl and alkoxy radicals having from 1 to 12 carbon atoms; and

(2) a substituted triazine selected from the group consisting of symmetrical triazines and asymmetrical triazines having the respective formulas to 5% by weight.

3. The composition of claim 1 wherein the substituted 20 phenothiazine is an N-substituted 3,7-dialkyl phenothiazine.

4. The composition of claim 3 wherein the triazine is 3. 1,3,5 triazine.

5. The composition of claim 3 wherein the triazine is 9. 1,2,4 triazine.

6. The composition of claim 4 wherein the substituted phenothiazine is N-benzy1-3,7-dioctyl phenothiazine.

7. The composition of claim 5 wherein the substituted phenothiazine is N-benzyl-3,7-dioctyl phenothiazine.

References Cited UNITED STATES PATENTS 3,344,068 9/1967 Waight et al. 252-47 3,093,585 6/1963 Low et al 25251.5 X 3,378,490 4/1968 Hotton 252-50 X 3,498,981 3/ 1970 Culbertson 25250 X DANIEL E. WYMAN, Primary Examiner W. H. CANNON, Assistant Examiner US. Cl. X.R. 252-47, 51.5 R