US3031402A - Lubricant composition - Google Patents

Description

3,931,492 Patented Apr. .24, 1962 3,031,402 LUBRICANT COMPOSITION John W. Nelson, Lansing, 111., assignor to Sinclair Refining Company, New York, N.Y., a corporation of Maine No Drawing. Filed July 27, 1959, Ser. No. 829,513 Claims. (Cl. 252-515) The present invention relates to oleaginous base lubricants having improved resistance to oxidation. More particularly it relates to lubricants containing certain organic nitrogen compounds, that is a small amount of an amide of an alkyl amine and a di(hydroxy phenyl)-substituted lower aliphatic carboxylic acid.

Mineral oil and synthetic ester lubricants, in the form of greases or free-flowing liquids are called upon to ease friction and prevent damage to machinery operated at temperatures to as high as about 450 F. At these higher temperatures, the internal combustion engine is an ideal oxidizing machine since the motor oil is violently agitated in the presence of air for lengthy periods of time. Greases are subject to similar conditions in their many applications.

Over the range of temperatures developed when employing lubricants, the rate of oil and grease oxidation approximately doubles for each 20 F. rise of temperature. Thus, the oil exposed to aeration at 300 F. may oxidize at a rate about 32 times as great as at 200 F. While well refined motor oils will only oxidize to only a negligible extent at temperatures of the order of 200 F. and lower, oxidation may become quite pronounced at temperatures of 250 F. and higher. In addition, metals act as powerful oxidation catalysts or accelerators; iron, copper and lead being particularly active. The rate of motor oil oxidation may accordingly be increased as much as one hundredfold, at any given temperature, due

- to exposure to engine metal surfaces, metal particles resulting from normal engine wear, and contamination with combustion chamber blow-by solids and air-borne dust.

All the various types of hydrocarbon constituents of lubricating oils and greases are susceptible to oxidation, if exposed to sufficient air or oxygen and at sufficiently elevated temperatures. Paraffinic hydrocarbons, both straightand branched-chain, and naphthenic hydrocarbons are readily reactive. Aromatic hydrocarbons, other than some naphthalene and anthracene derivatives, are indicated to be even more susceptible, possibly because of the activating influence of the aromatic ring structure. Synthetic ester lubricants are basically paraifinic in structure differing from hydrocarbon lubricants in many instances by the insertion of ether oxygen atoms in the 7 chain and the partial oxidation of some carbon atoms.

Of even more importance from an engine performance viewpoint are the oxidation end-products formed. Probably one of the first types of oxidation products formed in an oil undergoing oxidation is organic peroxides, which may act as catalysts, causing oxidation of additional components in an oil, or more intensive oxidation of slightly oxidized constituents. Peroxides have also been indicated to be vigorously corrosive to sensitive types of engine bearings. One of the chief end-products of the oxidation of paraflin hydrocarbons is organic acids, ranging from formic and acetic up to high molecular weight fatty acids. Alcohols, aldehydes and ketones also appear to be produced, while more drastic oxidation of parafiin hydrocarbons may yield oxy or hydroxy acid, esters, lactones and complex condensation products of high molecular weight. The acids formed by parafiin oxidation, particularly those of low molecular weight, are vigorously corrosive to copper-lead and cadmium engine bearings. The more complex oxy-acids have been indicated to be a cause of piston ring sticking. Naphthenic hydrocarbons probably oxidize and yield oxy-products in a manner very similar to the paraflins.

The aromatic hydrocarbon constituents of lubricating oils tend to be most readily oxidized, possibly because of the sensitivity of the hydrogen atoms in side chains adjacent to the aromatic ring nucleus, yielding acids and acidic oxy-products of the same general types as the paratfins. Subsequent oxidation of the aromatic ring residue probably results in formation of very complex condensation and polymerization products which tend to be oil insoluble. These types of oxidation products probably constitute the sludges, resins and varnishes which are formed by the oxidation of the more asphaltic or aromatic types of mineral oils. Thus, highly refined, paraflinic oils of high viscosity index tend to become acidic and corrosive to bearings, but do not form excessive oxidation sludges or varnishes in severe engine service, whereas oils of lower V.l. and containing considerable aromatic constituents tend to develop excessive engine sludges and varnishes.

As is well known, commercial lubricating compositions generally contain an oxidation inhibitor. The exact mechanisms by which inhibitors minimize or retard oil oxidation are not known, although it is probable that they function by decomposing organic peroxides as they are formed so that their catalytic effect is nullified. Similarly, inhibitors probably tend to poison or counteract metallic catalysts. Inhibitor additives do not eliminate or entirely prevent oxidation of the lubricant when conditions of exposure are severe, and some types of oils are stabilized and improved to a much greater degree by inhibitors than are others. A satisfactorily stable and oxidation resistant oil requires careful refining of the base stocks plus proper selection of the type and concentration of inhibitor most suited to the particular oil.

The art has recognized several types of inhibitors. Elemental sulfur in small amounts can be dissolved in lubricating oils and is quite efiective as an oxidation inhibitor. In order to render sulfur less corrosive to cooper and still retain its inhibiting eifect, it may be reacted with unsaturated fatty oils such as sperm oil or synthetic unsaturated fatty esters of similar general composition. Aromatic and aliphatic sulfides represent another type of compound sometimes utilized as an oxidation and corrosion inhibitor. Relatively simple sulfurcontaining aromatics such as dibenzyl sulfide, dixylyl disulfide or dicetyl sulfide are sometimes utilized. More complex compounds of similar type are the alkyl phenol sulfides.

The efiectiveness of phosphorous as an oxidation inhibitor in oils has been recognized for many years. Oilsoluble organic compounds of phosphorous such as alkyl and aryl phosphites, e.g., tributyl phosphite and triphenyl .phosphite, and aluminum, calcium or barium salts of alkyl phosphoric acids are types of phosphorous compounds which display antioxidant properties. Inhibitors containing both sulfur and phosphorous are usually more effective and efficient in a wider variety of lube oil base stocks than those containing only phosphorous or sulfur, and many of the inhibited motor oils now on the market contain one kind or another of these combination sulfurphosphorous type additives. One widely used type of sulfur-phosphorous additive is the dithiophosphates, which are prepared by the reaction of phosphorus pentasulfide with alcohols. I

Oil soluble organic amines and phenol derivatives such as phenyl-a-naphthyl amine and fi-naphthol, have been used for many years as oxidation inhibitors in highly refined turbine oils, lubricating greases and the like. However, compounds of this type display but limited effectiveness in motor oils under the oxidizing conditions encountered in engines. It has been theorized that these simpler amines and phenols are essentialy low temperature inhibitors, and as such are effective only at temperatures below about 200 or 250 F., which is considerably below those to which motor oils are exposed in engines operating at heavy loads. More complex amines and phenol derivatives such as tetramethyl diamino diphenylmethane and alizarin are used to some extent as motor oil inhibitors. However, these compounds are rarely used alone but are applied in conjunction with other types of inhibitors, so that they may be considered more as supplemental additives rather than as primary inhibitors.

It has generally been believed that aliphatic amides have no anti-oxidant properties, but it has now been found that certain carboxylic acid amides are antioxidants for oleaginous base lubricating oils. The compositions of this invention incorporate a small amount sufficient to inhibit oxidation, of an acid amide of an alkyl amine in the base oil of lubricating viscosity which is the major portion of the composition. The acid amide is usually present from about 0.005 to 5.0 weight percent of the final lubricant composition, preferably from about 0.05 to 0.5% or 1%.

The novel additive of this invention can be formed by the amidization of a phenol-substituted aliphatic carboxylic acid containing from 4 to 8 carbons in the aliphatic chain containing the carboxyl groups. Especially preferred is 4,4-bis(phydroxy phenyl) pentanoic acid,

' (1H2 (13H; (700K The phenol group may also be substituted with alkyl or other groups which do not destroy the anti-oxidant effect.

These acids may be prepared by a method described by Yu and Day in the Journal of Organic Chemistry 23, pp. 1004 to 1006 (July 1958). Suitable acids are 3,3- bis(p-hydroxyphenyl) butanoic acid; 3,3bis(3-methyl- 4-hydroxyphenyl) butanoic acid; 3,3-bis(3,5-dimethyl-.4- hydroxyphenyl) butanoic acid; 3,3 bis(3-methyl 4 hydroxyphenyl) pentanoic acid and 4,4-bis(3-monochloromethyl-4-hydroxyphenyl) pentanoic acid.

These acids have generally been found to be insoluble in lubricating oil, and the number of the carbon atoms in the amine is usually from about 10 to 50 or more preferably at least '28, to impart oil-compatibility, i.e. soluble, dispersible or miscible properties, to the final product. Primary or secondary amines can be used and I prefer that the amine have at least one alkyl group of at least 16 carbon atoms, e.g. 16 to 24, in a straight chain, most advantageously the amine has two such groups.

Some amines which can be used to supply the amide portion of the novel compounds of the invention are commercial available fatty amines such as: Armeen HT, a hydrogenated tallow amine comprising approximately 71% octadecyl, 24% hexadecyl, 3% octadecenyl and 2% tetradecylamines; Armeen HTD (distilled Armeen HT); Armeen O, a mixture of 85% oleyl, 6% linoleyl, 5% hexadecyl, 4% tetradecyl and 1% stearylamines; Armeen OD (distilled Armeen O); Armeen 18D, distilled octadecylamine; Armeen C, a mostly C amine derived from cocoanut; Armeen CD (distilled Armeen C); Alamine H26D, another distilled tallow amine; Primene 81R, a mixture of branched-chain amines containing 12 to 14 carbon atoms; and Primene IMT, a mixture of branched chain primary amines containing 18 to 21 carbon atoms. Secondary amines useable in this invention include those corresponding to the named primary amines, e.g. dioctydecyl amine, dihexyldecyl amine, dioleylamine, etc. Aliphatic primary diamines, such as those commercially available in the Duomeen series which have the requisite 4 carbon content are also suitable materials for use in this invention. For example, Duomeen T, a hydrogenated reaction product of tallow amine and acrylonitrile having a 32 to 50 iodine value and the structure where R is an alkyl group of 16 to 18 carbon atoms obtained from tallow, may be used.

The amides may be used in mineral oil liquid lubricants, mineral oil based greases, synthetic oils and synthetic oil based greases. The additive is prepared by heating and stirring equimolecular quantities of the acid and appropriate amine with suflicient water entraining agent, such as xylene, to obtain a temperature of about 150 to 200 C. for say from about 10 to 25 hours. Boric acid may be used to increase the speed of the reaction. After the theoretical amount of water is removed, the water entraining agent is removed and the product needs no further purification.

The lubricating oil base stock used in the present invention is of lubricating viscosity and can be for instance a solvent extracted or solvent refined oil obtained in accordance with conventional methods of solvent refining lubricating oils. Generally, lubricating oils have viscosities from about 20 to 250 SUS at 210 F. The base oil may be derived from parafiinic, naphthenic, asphaltic or mixed base crudes, and if desired, a blend of solventtreated Mid-Continent neutral and Mid-Continent bright stocks may be employed. A particularly suitable base oil used in the preparation of the composition may be described as a liquid mineral oil fraction having a viscosity index of about 100.

Grease compositions may be prepared by the incorporation or formation in the oleaginous base of greasetlrickening fatty acid soaps of metals such as the alkaline metals of group I and II of the periodic table. The soap content of the grease is generally about 225 Although the use of high viscosity oils (above SUS at 100 F.) gives harder greases, the use of a low viscosity nonnaphthenic 100% solvent refined neutral Mid-Continent base lubricating oil provides a grease having better low temperature pumpability. The soaps are usually the alkali metal or alkaline earth metal, e.g. lithium, barium, calcium, etc.; salts of natural or synthetic long-chain carboxylic acids, such as stearic, hydroxy stearic or lauric acids, say of 12 to 20 carbon atoms.

Greases which comprise about 225% of the abovementioned soaps in a synthetic oleaginous base may also be given resistance to oxidation by the use of the phenolsubstituted aliphatic acid amide of an N-alkyl amine of this invention. One type of synthetic oleaginous base used is the ester of synthetic oils of lubricating viscosity which consist essentially of carbon, hydrogen and oxygen. Various of these lubricating materials have been described in the literature and generally their viscosity ranges from the light to heavy oils, e.g. about 50 SUS at 100 F. to 250 SUS at 210 F. and preferably 30 to SUS at 210 F. These esters are of improved thermal stability, low acid number, and high flash and fire points. These complex esters, diesters, monoesters and polyesters may be used alone or to achieve the most desirable viscosity characteristics, complex esters, diesters and polyesters may be blended with each other or with naturally-occurring esters like castor oil to produce lubricating compositions of wide viscosity ranges which can be tail0r-made to meet various specifications. This blending is performed, for example, by stirring together a quantity of diester and complex ester at an elevated temperature, altering the proportions of each component until the desired viscosity is reached.

These esters are prepared fundamentally by the action of acids on alcohols. The mere mixture of an alcohol and acid at the proper temperature will react to produce an equilibrium mixture which includes the monoester. The same is true for the reactions of organic dibasic acids and glycols to produce synthetic lubricant polyester bright stock. The diesters are frequently of the type alcoholdicarboxylic acid-alcohol, while complex esters are generally of the type XY-ZYX in which X reprea steel-backed copper-lead catalyst, and oxygen is bubbled into the liquid at a rate of 5 liters per hour. Pentane insolubles are determined by centrifuging the fluid upon completion of the test. A test was also run on a portion sents a monoalcohol residue, Y represents a dicarboxylio 5 of the mineral oil blend containing the additives other acid residue and Z represents a glycol residue and the linkthan the amide inhibitor to show the anti-oxidant charages are ester linkages. These esters have been found to acteristics of the amides of this invention. be especially adaptable to the conditions to which turbine The alkaline earth metal sulfonate detergents that may engines are exposed, since they can be formulated to give be used, if desired, in my invention are those soluble in a desirable cpmbil'lalion of high fl h point, low pou 10 the base lubricating oils and obtained for instance, by point, and h1gh viscosity at elevated temperature, and neutralizing aromatic sulfonic acids with the hydroxides, need e ntalu no addltl s wl h might leave a l'esldlle chlorides, orddes or other inorganic compounds of the Epon xlllolatihzatigmt glllt'adtililgll, mag complefit 1ester: allllirgil netearth metallls. 1(generally, thebsulfmate vlvlillhbe ave 5 Own goo S a y 5 e313 reases W 1C 118 8 men to give t e u ricating oi I en an a a'ne these esters as the oleagino-us base also have most of these 15 earth metal content of about 0.2 to 2.0 weight percent. chasractirfsucs. d d b r d d t k The preferred aromatic sulfonic acids are the oil-soluble m 6 1110110- an 16a! 3 16 5 use 0 m3 6 mahogany sulfonic acids which can be derived from the synthetic ester lubricant bases can be branched or straight treatment of a suitable petroleum oil, such as a liquid chain and saturated or u s ur and y q y petroleum distillate boiling in the range of about 600 to contain from about 2 to 12 carbon atoms. The alcohols 20 1000 R, i h f i 1f -i id or lf t i id usually; ctclilntalneglirml Sag}? 4c ltgd 12t hi glogh gzmgong separaing the resulzgig acilcll sludge from the acid treated genera e us g 111 e i 01 an recovering e ma ogany acids contained in the glycols Of 4 to 20 30 carbon atoms Preferably 4 to acid treated oil. The useful mahogany acids generally Material? normally incorporated in 1ubfiating Oils and ha e a molecular Weight of from about 300 to 500 or ggea-ses to $13531"?- jsptieig lni lialrtagl l ll ls 52 5121 gsiz lrg more, and althotaglh theili; exadct chemical structures may e compo 1 n 0 1 1 I e vary, it appears at suc aci s are composed to a large 1011 m l eX'lfeme DQ1 agents, Q extent of sulfonated aromatic hydrocarbons having either or r one or more on -c am a on s containin om t about Weight P F in general they can about 8 to 30 carbon atoms Zttai hecl tothe ring nuclei. employed in any amoluntsdesiredflso lOclllg as the comp0s1- Other suitable aromatic sulfonic acids are the oill h 2 1a f i d6 i fl y 3 acts d soluble aryl sulfonic acids; such as benzene sulfonic acids e O exampe 1s e consl ere us m W and naphthalene sulfonic acids, which include the oil- To a 3-l1ter round bottom 4-necked flask equipped with 80,11,016 alk lated ar 1 sulfonic acids hi h th 1k 1 a thermometer, motor driven stirrer, reflux condenser, l f t 18 b w F a y Water trap and heating mantle, were charged 214 g. (0.75 con ams mm 0 on aoms or Instance mole) 44 biS (p hydmxy phenyl) Pentanoic acid, 400 dmonyl naphthalene sulfomc acid, and those prepared (0.75 mole) diotadecyl amine from hydrogenated tallo-w by reactlol} of P T Wax F l chalns of 20 or more and 180 g. of xylene. The mixture was heated and stirred Wlth f f nuclel Whlch are then Sulfonated for 14 hours, removing the Xylene meanwhile to raise the 40 by fuming sulfuric acid, e.g. wax substituted naphthalene. flask temperature to 200 C. A total of 16.5 cc. of water The aromatic oil-soluble sulfonic acids are conveniently was obtained. The remainder of the xylene was then reemployed as a concentrate in the hydrocarbon from moved y heating The Product While blowing which they are derived and are usually present in an it w1th mgr7ogen. l'ghe p o c welghed 5 80 and m approximate 10 to 30 weight percent concentration. Sented a 0 Y The alkaline earth metal sulfonates of the present in- Blends of various propoftlons of the P' vention can be neutral or basic sulfonates. By basic X P pentamlcllesl were g g sulfonates is meant those sulfonates in which the alkaline Pl fractlons'f {g g i 535?: sg gis earth metal is present in an amount in excess of that g fig ig ggg i ss g g a viscogsity of 537 theoretically required to react with the sulfonic acid from sus at 100 F.; 5.44% carbonated, basic barium mahogf f $5 9 P if any sulfonate (15 to 20% concentrate in mineral oil) ou 9 e o anum e Su ona a an which gives a barium content of 037% to the finished 1n the case of basic calcium sulfonate at least about 1.2 lubricant, 13% dLLmethYlamy} Zinc .dithjophosphate eqmvalents of calcium. Usually the bHSlC alkahne earth ester (50% concentrate'in mineral oil) and 0.005% of 50 metal sulfonates do not have to have more than 5 q ysilicon antifoam agent alents of alkaline earth metal. Also suitable are the 011- TABLE I Railroad Oxidation Test e ili 0 t Wt A d i i Initial l s. a 01 so Run s Samp e Pe ignt Rise chg.(mg.) No. ubles pH 111 l 1 Mineral Oil containing sulfonate 86.5 2.3 4.9 1.4 1.6

and other additives plus- 2 N-dhioctaideeylt sa-Bism-hydroxy 0.5 18.4 -4.8 4.2 0. 02 1.7

. 3 N31i d iizli lt laZb is Q-hyGIOXy 0.1 21.6 2.9 4.5 0.02 1.6 4 N- bl z tlain rl t ig i gp-hydroxy 0.3 23 -2.8 4.5 0.02 1.8 5 N ie b ebr rl ifil ib fp-hydroxy 0.6 22 4.3 4.5 0.03 1.0

phenyl) pentamide The test was the standard Railroad Oxidation test. The test consists essentially of placing 300 m1. portion of a blend in a beaker which contains a weighed amount of soluble carbonated neutral or basic alkaline earth metal sulfonates.

The zinc dithiophosphate anti-oxidants which may, if

a desired, be incorporated in the lubricating compositions of my invention are the oil-soluble Zinc salts derived from various diester dithiophosphoric acids conventionally prepared by reacting a sulfide of phosphorus, such as phosphorous pentasulfide with an alcohol, phenol or mercaptan. The organic portion in the acid diesters may be an aryl, alkyl, aralkyl or cycloalkyl group which contains from about 4 to 20 carbon atoms, preferably 6 to 14 carbons, and may, if desired, be further substituted. Suitable alcohols which may be employed in preparing the acid esters include primary and secondary alcohols such as 2-methylamyl alcohol, 4-methylpentanol-2, Z-methylpentanol-l, Z-ethylhexanol, diisopropyl carbinol, cyclohexanol, butanol-l and octadecanol-l, or mixtures of high and low molecular Weight alcohols. Other hydroxyl-containing materials which can be reacted with phosphorus sulfide include phenols and allrylatecl phenols such as dioctylphenol, tri-isobutylphenol and the like. More specifically, the preferred compounds of this group include the zinc salts of dialkyl dithiophosphates such as dihexyl dithiophosphate, diheptyl dithiophosphate, dilauryl dithiophosphate, di-Z-methylamyl dithiophosphate, di-Z-ethylhexyl dithiophosphate, and the like.

Particularly suitable zinc dithiophosphates which can be employed are the zinc salts obtained from a mixed dithiophosphate prepared by reacting Z-methylamyl alcohol or a technical mixture of C secondary and C primary alcohols, mainly the former, with phosphorus pentasulfide. The zinc dithiophosphate is employed in my improved lubricating composition in a minor amount suflicient to inhibit oxidation and bearing corrosion and, in most instances, the amount used provides about 0.03 to 0.2 percent by weight of phosphorus on the basis of the lubricating oil in which it is incorporated.

I claim:

1. An oleaginous lubricant composition consisting essentially of a base oil of lubricating viscosity and an amount sufiicient to give improved anti-oxidant properties to the composition of an oil-compatible, N-alkyl,

is(hydroxy phenyl) carboxylic acid amide, wherein the carboxylic acid radical is in an aliphatic chain of 4-8 carbon atoms.

2. The lubricant composition of claim 1 in which the base oil is a mineral oil of lubricating viscosity.

3. The lubricant composition of claim 1 where the N-alkyl has two alkyl groups each of which has 16 to 24 carbon atoms.

4. The lubricant composition of claim 1 in which the N-alkyl group contains about 10 to carbon atoms.

5. The lubricant composition of claim 2 wherein the amide is present in a range of about 0.05 to 1% of the lubricant composition.

6. The lubricant composition of claim 2 in which the Nall-;yl group contains about 10 to 50 carbon atoms.

7. The lubricant composition of claim 3 where the carboxylic acid is 4,4-bis(p-hydroxyphenyl) pentanoic acid.

8. The lubricant composition of claim 4 in which the N-alkyl group contains 28 to 50 carbon atoms.

9. The lubricant composition of claim 5 in which the N-alkyl group contains about 10 to 50 carbon atoms.

10. The lubricant composition of claim 7 where the N-alkyl is N-dioctadecyl.

References Cited in the tile of this patent Johnsons Di-Phenolic Acid 4,4 Bis (4-Hydroxyphen yl) Pentanoic Acid, pub. February 1959, by S. C. Johnson and Son, Racine, Wisconsin, pages 6 and 2426.

Claims (1)

1. AN OLEAGINOUS LUBRICANT COMPOSITION CONSISTING ESSENTIALLY OF A BASE OIL OF LUBRICATING VISCOSITY AND AN AMOUNT SUFFICIENT TO GIVE IMPROVED ANTI-OXIDANT PROPERTIES TO THE COMPOSITION OF AN OIL-COMPATIBLE, N-ALKYL, BIS(HYDROXY PHENYL) CARBOXYLIC ACID AMIDE, WHEREIN THE CARBOXYLIC ACID RADICAL IS IN AN ALIPHATIC CHAIN OF 4-8 CARBON ATOMS.