US3798166A - Lubricant compositions - Google Patents

Abstract

LUBRICANTS HAVING ADDED THERETO A SMALL AMOUNT OF A MIXTURE OF AN ACYLAMIDO DIARYLAMINE AND A DI(ALKARYL) AMINE HAVE INPROVED OXIDATION STABILITY.

Description

United States Patent Oifice 3,798,166 Patented Mar. 19, 1974 ABSTRACT OF THE DISCLOSURE Lubricants having added thereto a small amount of a mixture of an acylamido diarylamine and a di(alkaryl) amine have improved oxidation stability.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to lubricant compositions having improved oxidation stability. More particularly, the invention relates to such compositions comprising small but effective amounts of an additive that has the ability to reduce oxidation of the lubricant.

Description of the prior art Lubricating oils and greases are subject to oxidative deterioration at elevated temperatures or upon prolonged exposure to the elements. The deterioration is evidenced, in many instances, by an increase in acidity and in viscosity, and when such deterioration is severe enough, it can cause metal parts to corrode. Additionally severe oxidation leads to a loss of lubricating properties of the oil, and, in aggrevated cases, to complete breakdown of the lubricated part or of the entire machine. -In combatting oxidation, many additives have been tried, but many of them are only marginally elfective except at high concentrations, especially when the lubricants are subjected to drastic oxidizing conditions.

;U.S. Pat. 3,377,315 discloses the use of one of the members of the inventive mixture, i.e. an acylamino diphenylamine as a stabilizer for natural and synthetic polymers and mineral oils. In addition, U.S. Pat. 1,907,- 545 teaches the use of m-acetylaminophenyl-beta-naphthylamine to increase aging resistance of rubber-like products.

SUMMARY OF THE INVENTION The invention provides a lubricant composition comprising a major amount of a lubricant and an amount suificient to inhibit oxidation thereof of a mixture of an acylamido diarylamine and a di(alkaryl)amine.

DESCRIPTION OF SPECIFIC EMBODIMENTS The acylamido diarylamines useful in the practice of the present invention correspond to the formula rl r A NH LA J NH R wherein Ar and Ar are selected from the group consisting of phenyl, naphthyl, anthryl and phenanthryl and R contains from about 4 to about 18 carbon atoms and is selected from the group consisting of alkyl, cycloalkyl, lower alkyl-substituted cycloalkyl and alkenyl. The

0 NHJJJR group may be attached at any of the available positions.

The di(alkaryl)amine utilizable with the above acylamido diaryl amine has the formula wherein Ar" and Ar' are selected from the group consisting of phenyl and naphthyl and R and R" are alkyl of from about 4 to about 18 carbon atoms.

When used as antioxidants, the mixtures of this invention are effective when they constitute from about 0.005%

to about 15% by weight of the lubricant base. Preferably,

anes and the like. Especially useful are those synthetic esters which are becoming more and more popular, particularly in aviation. These include esters made from polycarboxylic acids and monohydric alcohols, such as those obtained by reacting methanol, ethanol, propanol, butanol, neopentyl alcohol and the like with pimelic acid, azelaic acid, adipic acid and the like, or from polyhydric alcohols and monocarboxylic acids. Of these preferred members are those made from trimethylol alkanes, where alkaneincludes ethane, propane and butane, pentaerythritol, diand tripentaerythritol, or mixtures thereof and an aliphatic monocarboxylic acid containing from 1 to about 20 carbon atoms or a mixture of such acids. The most preferred are esters from the pentaerythritols and monocarboxylic acids having from 5 to 9 carbon atoms, or mixtures of these acids.

The following examples will serve to specifically illustrate the practice of the invention. It will be understood that they are illustrative only, and are not intended to limit the scope of the invention to a narrower range than described hereinabove.

EXAMPLE 1 N- (4-anilinopheny1) pivalamide To a solution of 92 g. of N-phenyl-p-phenylenediamine in 300 ml. of pyridine there was added during nearly 0.75 hour 61 g. of pivaloyl chloride while stirring. During the addition the temperature was maintained at 2530 C. by external cooling. The temperature was raised to 45 C. while stirring was continued for an additional 1.5 hours. The reaction mixture was poured into an excess of ice-water. The organic part was taken up in ether. The ether solution was washed with aqueous caustic solution, then with water and dried. Solvent was removed and the residue was recrystallized from benzene to afford the N- (4-anilinophenyl)pivalamide, melting at l28130 C.

EXAMPLE 2 N- (2-anilinophenyl) pivalamide This product was prepared by the method of Example 1 using 46 g. of N-phenyl-o-pehnylenediamine in 150 ml.

, of pyridine and 30.5 g. of pivaloyl chloride. Recrystallization from ethanol gave N-(2-anilinophenyl)pivalamide, a crystalline solid, melting at ll6l18 C.

EXAMPLE 3 N-(4-anilino-1-naphthyl)pivalamide This product was prepared by the method of Example 1 using 10 g. of 4-anilino-l-naphthylamine in ml. of pyridine and adding 6 g. of pivaloyl chloride in 50 ml. of 1,2-dimethoxyethane. Addition was at 22-28 C. during. 1.25 hours; reaction time was 3.25 hours at 100 C. N-(4-anilino-1-naphthyl)pivalamide was recrystallized 3 from ethanol to aiford a crystalline solid melting at 174 176 C.

EXAMPLE 4 4-(4-anilino-1-naphthy1)lauramide To a mixture of 4-anilino-1-naphthylamine and 100. ml. of triethylamine dissolved in 100 ml. of dimethoxyethane, 10.5 g. of lauroyl chloride was added during about 1 hour at 2226 C. while stirring and cooling with an ice-water bath. The reaction mixture was then refluxed at 90 C. while stirring for an additional 3.75

hours and then poured into water. The crude N-'('4-" anilino-1-naphthyl)lauramide which precipitated was collected and recrystallized from ethanol to give a crystalline solid melting at 101102 C.

EVALUATION OF PRODUCTS Oxidation test The compounds produced in accordance with this invention were blended into a synthetic ester oil lubricant (made by reacting pentaerythritol with an equimolar mixture of C and C monocarboxylic acids) and tested in oxidation test in accordance with the following proce-'. dure.

A sample of the test composition is heated and air at the rate of about 5 liters per hour is passed through for a period of about 24 hours. Present in the test sample are specimens of iron, copper, aluminum, and lead. The kinematic viscosity, measured at 100 -F. (percent KV change) and the change in the neutralization number (NN change) are reliable indicators of an additives antioxidant effectiveness. Lead loss is determined by weighing the sample prior to the start of the procedure and once again after it is completed. An improvement in either or all of these indicates that an additive is elfectively reducing the effects of oxidation. It should be noted that the metals are typical metals of engineer machine construction and that they provide some cat;

alysis for the oxidation of organic materials. The results,

are tabulated in the following table.

X VAN 81 is p,p-di'octyl diphenylamine.

It may be seen from the above data that "the combina tion of additives improves at least one of the indicators of oxidation. For instance, the combination of the Example 2 product with VAN 81 gives an unexpected decrease in lead loss.

Among the other acylamido 'diarylamines which may be used are the following.

O l]; I ArNH{Ar}NH R Compound Ar Ar R 1 Phen 1 Na hthyl Butyl. 2 dz r Octyl. 3---- do Phenyl Tetradecyl. 4 Naphthyl..... Naphthyl-.- Octadecyl.

Phenyl Anthry1 Cyclohexyl. do .-Phenanthry1 Methylcyclohexyl. 7 do Naphth Butenyl.

rln dn Pentenyl.

Included among the other di(alkaryl)amines which 7 may be used are the following.

Octadeeyl .do -.do Octadecyl.

Either of these can be combined with the acylamido diarylamines above to provide eifective antioxidant mixtures for lubricants. In other words Compound A may be mixed with Compounds l-8 in accordance with this invention. So in turn may Compounds 13, C and D be mixed with Compounds 1-8.

*Although'the present invention has been described with certain specific embodiments, it is to'be understood that modifications and variations may be resorted to without departing from the spirit and scope of this invention as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the appended claims.

I claim:

1. A lubricant composition comprising a major amount of a lubricant and an antioxidant amount of a mixture of (1) an acylamido diarylamine of the formula 0 Ar-NH-Afl-NHii R wherein Ar and A1" are selected from the group consisting of phenyl, naphthayl, anthryl and phenanthryl, and R contains from 4 to 18 carbon atoms and is selected from the group consisting of alkyl, c'ycloalkyl, lower alkylsubstituted cycloalkyl and alkenyl, the

0 Nat group being attached at any of the available positions and (2.) a di(alkaryDamine of the formula wherein Ar" and Ar' are selected from the group consisting of phenyl and naphthyl and R and -R" are alkyl of from 4 to 18 carbon atoms.

2. The composition of claim 1 comprising from about 0.005% to about 15% by weight thereof of said mixture. 3. The composition of claim 1 wherein the lubricant is a lubricating oil or grease. i 4. The composition of claim 3 wherein the lubricating 4 oil is a synthetic ester lubricating oil.

5. The composition of claim 1 wherein the diarylamine is N- (4-anilinophenyl)pivalamide and the di(alkaryl) amine is p,p'-dioctyl diphen'ylamine.

6. The composition of claim 1 wherein the diarylamine is N-(2-anilinophenyl)pivalamide and the di(alkaryl) amine is p,p'-dioctyl diphen'ylamine.

7. The composition of claim 1 wherein the diarylamine is N- (4anilino-1-naphthyl) pivalamide and the di( alk-aryl) amine is p,p-dioctyl diphenylamine.

8. The composition of claim 1 wherein the diarylamine is N-(4-anilino-4-naphthyl)lauramide and the di(alkaryl) amine is p,p'-dioctyl diphen'ylamine.

References Cited UNITED sTATEs PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3798166 Dated March 19, 97

Inventofls) MI L ID It is certified that error appears in the above-identified patent "and that said Letters Patent are hereby corrected as shown below:

Col. 3, line L- t-Anilino, etc should be N- L-Anilino, etc.

Col. 3, line 52, "5" should be 5M Col. L, line 31, "naphthayl" should be naphthyl Signed and sealed this 30th day of July 1971 (SEAL) Attest:

McCOY M. GIBSON, JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents