US2998386A - Lubricant containing a fatty acid amide of phenothiazine - Google Patents

Description

2,998,386 LUBRICANT CONTAINING A FATTY ACID AMlDE F PHENOTHIAZINE John W. Nelson, Lansing, 111., assignor to Sinclair Refinlil ig Company, New York, N.Y., a corporation of ame No Drawing. Filed Jan. 26, 1959, Ser. No. 788,766

9 Claims. (Cl. 25242.1)

This invention is concerned with oleaginous base lubricants having exceptional oxidation resistance at high temperatures. The compositions contain a base oil of lubricating viscosity and a small amount of a fatty amide of phenothiazine.

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 up 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 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 oxidize to only a negligible extent at temperatures of the order of 200 F. and lower, oxidation may become quite pronounced at tem peratures 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 100-fold, 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 suflicient air or oxygen and at suificiently elevated temperatures. Paraflinic 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 chain and the partial oxidation of some carbon atoms.

Of evenmore 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 ends-products of the oxidation of paraifin 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 yieldoxy or hydroxy acids, 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. 'Ilhe more complex oxy acids have United States Patent been indicated to be a cause of piston ring sticking. Naphthenic hydrocarbons probably oxidize and yield oxyproducts in a manner very similar to the paraffins.

The aromatic hydrocarbon constituents of lubricating oils tend to be the 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 parafiins. 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, parafiinic 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 V1. 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 flaey 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 oleaginous lubricant whencon'ditions 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 effective as an oxidation inhibitor. In order to render sulfur less corrosive to copper and still retain its inhibiting effect, 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 sulfur:

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

Oil-soluble organic amines and phenol derivatives, such as phenyl-a-naphthylamine and fl-naphthol, have been used for many years as oxidation inhibitors in highly refined turbine oils, lubricating greases and the like. How- -2,99s,3se

ever, compounds of this type display but limited efiectivenests in motor oils under the oxidizing conditions encountered in engines. It has been theorized that these simpler amines and phenols are essentially low temperature inhibitors, and as such are effective only at tempera tures below about 200 or 250?. R, which is considerably below those to which motor oils are exposed in engines. operating at heavy loads. More complex am-inesand 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 conjunctionwith other types of inhibitors, so that they may be considered more as. supple mental additives. rather than as. primary -inhibitors.

It has now been found that acid amides-in particular, fatty acid. amides-of, phenothiazine' are. superior agents to inhibit oxidation of 'oleaginous. base. lubricants in a temperature range ofabout 300 to. 450. F. The compositions of this invention .incorporatea small amount, sufficient to inhibit oxidation, of an acid amide. o'fpheno; thiazine in the lubricatingoilbase which is the major por-. tior of the composition. This inhibitor ispreferably used in combination with low-ternperaturev antioxidants, such as Ortholeurn 300?? (a diphenylarninetype.) orzinc dithiophosphate which are eifective below. about 3.00.? E, to PI Vide. a. lubricant resistant. to. oxidation overthe. whole temperature range in which. it. will be used. The acid amide of phennthiazine. frequently. comprises. about 0.1 to of the final lubricant. omposition, preferablyless than about 2%. The, compositionsofthis. invention have oxid s abili y. in. a h gher. emp rature. r g than clcagino s lu ricant containing he, lines, mentioned bov r ampl he. atty ac ides of. p en thia:

zinc n m ner l. il cfic tivc y. inh it d the. QiLtcc id tiQn in n oxyg n b o p o test at. 3.69.? us ng copp r and ead. cataly t ih no h az n itse f. is. incfiectir an a additiycfcr n al cilb sc ubric n s! t s q yabcut 0- lu le. in mine oi At cmpt o sclwb li c 0. %,v by n rporatingl uric. acid. in. th ase. il nd heatin the. mixt e, ai ed The novel additives of this invention are (Ii-substituted, amidssfc nc easily byhc eaction. c a at c diw n caothiazine ith hc c casccti wat r, ddi ive maybe ma e fr nt a ty. acids rsqucn y h vin 0 .0 ca bon a ms he n thj hc carb n e 1.. impqr ant. 9 ar. a the. fic tcthc d itix con: c acd but it liculd c nsfincush. cimna i pa ib c. -c-. 1ub1a is srsibl -cr. uscihla ro he fina mi c-.. Al. ns f ver/ car on om is o be n. sc a c mnatt n dv nta es he maybe u d; minera li uitlt u r ant tminc al; Qil a ds casss. d. nth ic srca s.-. ns. a xas' as au ic nd te an u ble f wa crs ca c c monocarboxylic acids su h as isodeca I wi at ac r ffe ts: he-w nt n be st cnn y. a n ou h y. c c iomstdc qu ntit es... .3 he s: rad n r' 'fc ablr t n s snc a wa e mta ias agent Such as luene. ylen cmrst n ts mess u a a catal t sb ti c l oni i is al a' sa tiqn ke asi tated and heated until water ceases to be given. off, A slight excess of phenot hiahine may be useddnthereaction, e n st sl' 'r s lfia ine n st! 9? e 9 .1 from the product, since, the phenOthiazine-arnide solubilizing efiect onth rihentith-iazine.

The mineral oil. b e stock used in, thepresentinven; tionfis of lubricating viscosity can be in hit solvent extracted. or. solvent. refiiiedfl oilv obtained, 1 v cordance wit 1 'o li lg ii l Iincth ds; f solvent. reiining lubricating oils. Generally, lubricating have vijsf T base nolc n-iay of acidson alcohols.

4 stocks may be employed. A particularly suitable base oil used in the preparation 05- the compositions described hereinafter is a solvent treated Mid-Continent neutral having a viscosity index of about 95.

Grease compositions may be prepared by the incorporation or formation in the oleaginous base of grease-thickening fatty acid soaps of metals such as the alkaline metals of groups I and ll of the periodic table. The sntstitc e sr c s s ncra y ab u .5 Although the use of high viscosity oils (above 10.0. SUS at F.) gives harder greases, the use of a low viscosity non-naphthem'c 100 percent solvent refined neutral Mid-Continent base lubricating oil provides a grease having better lowtemperature 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 2-2 5% of the abovementionedsoaps in a synthetic oleaginous base may also be given resistance to oxidation in the 300-450" F. temperature range by the use of acid amides of phenothi'azine. One type ofsynthetic oleaginous base used is the ester synthetic oils of lubricatingviscosity which consist essentially ofcarbon, 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. 'Iihesees'ters are of improved thermal stability, low acid number, and high flash and fire points. These complex esters, 'diesters, monoesters andpolyesters may be used aloneror, to achieve the mostdesirable viscosity characteritics, complex esters, diestersand polyesters may be blended with each. other or with. naturally occurring esters lilrecastorv oil to produce lubricating compositions of wide viscosity. ranges which can .betailor-made to meet various specifications. Thisblending is performed, for example, by,.stirring together a quantity of diester and con plcx esterat an. elevated temperature, altering the proportions; of. each component until the desired viscosity is reached;

Thcsccsters. are prepared. fundamentally by the action The mere mixture of an-alcohol andacidatthe. propertem-perature willreact to produce equilibrium. mixture. which includes thev monoester. same. is true, for. the. reactionso-f organic dibasic acidsand glycolsto producesynthetic lubricant polyester hrighhstocks, The diesters are.frequently..of the type algohol dicanboxylic acidealcohol, while. complex esters aregenerally-ofi the..type.X.--.YZY--X in which X represents a. mono-alcohol residue, represents a dica rboxylie. acidresiduaand Z. representsa glycol residue and thelinkages. are. ester linkages. These esters have been foupdqto be especially. adaptable. to. .the conditions to which, turbine engines are..exposed, since they. can be formulatedto give adcsirablecombination of high flash point, low, point, and, highyiscosityl at elevated temn. 8,. a cedccntain. no additives which might le a,residue,upon volatilization. In addition, many c m sn e t rs ave. shown. good stability o. sh ar. qreases whigh use these. esters. as the oleaginolls .base

Y9.- mcst; of. h e. arac ri c -1 a; mono. n d ca bcxy c ac d ed to make i syn he ic st rrs u ric ntba s-can n hed o a h chai. tur ted r unsaturated a -th y on i from abgut: M 2; arbon t m h pr c r d cid are he aun l ph ti ibasic acids w ch in ud among Q cta.succt c,. i l co ubc ic, ai ac nd... s sbaci cid which t es of l ha.-

egi ji suberic acid, alphaaalpha diethyl adipic acid, and seb acid. The. alcohols. contain from .4. -.to 12 carbon t. hcmc ic dr a ho s clude, m so u l hc y1,,. -c 1 l .cxyl, .d dccy c yl, nd. s r lsq ls-l h l cels. d. l col. a l dc thylene glycol, propylene glycol, butylene glycol, triathylene glycol, diethylene glycol, ethylene glycol mono-2- ethylhexyl ether, diethylene glycol mono-n-butyl ether, propylene glycol mono-n-butyl ether, tripropylene glycol mono-ethyl ether, 2-ethyl-1,3-pentanediol, 2-ethy1-1-,3- hexanediol, 2-isopropyl-1,3-hexanediol, etc. In general the useful glycols include the aliphaticmonoglycols of 4 to 20 or 30 carbon atoms, preferably 4 to 12, and it the polyg lycols having from about 1 to 50 ether oxygen atoms obtained from monoglycols 'of 2 to 12 carbon atoms. Advantageously, the polyglycols contain from about 1 to 10 ether oxygen atoms and these can be of the-formula H(OC H OI-I;whe re x is 2 to 4. The preferred polyglycols are the polyethylene and polypropylene glycols and those particularly useful have molecular weights from about 150 to 450.

Di-Z-ethylhexyl sebacate (Plexol 201) and diisooctyl azelate (DiOAz) are preferred synthetic lubricant bases from the standpoint of economy, availability and satisfactory properties. DiOAz is a product made by the esterification of azelaic acid with an alcohol mixture made by the oxo process from C to C copolymer heptanes. This alcohol is commercially available as a mixture containing 17% 3,4-dimethylhexanol; 29% 3,5-dimethylhexanol; 25% 4,5-dimethylhexanol; 1.4% 5,5-dimethylhexanol; 16% of a mixture of 3-methylheptanol and 5- ethylheptanol; 2.3% 4-ethylhexanol; 4.3% alpha-alkyl alkanols and 5% other materials. Some other specific satisfactory diesters are di-(1,3-methylbutyl) adipate, di- (Z-ethylbutyl) adipate, di-(l-ethylpropy'l) adipate, diethyl oxalate and di-(undecyl) sebacate.

Materials normally incorporated in iube oils and greases to impart special characteristics can be added to the compositions of this invention. These include corrosion inhibitors, extreme pressure agents, antiwear agents,

denser, thermometer, water trap and heating mantle, were charged the following: 219 g. (1.1 moles) pheno- The amount of additives included in the composiing the fluid upon completion of the test.

in 3 parts of hot hexane, cooling to room temperature and filtering it. This gave sample 80.

EXAMPLE II The stearic acid amide of phenothiazine, was prepared as follows. To the same equipment described in the lauric acid run above, were charged 299 g. (15 moles) phenothiazine (N.F. grade), .284 g. (1 mole) stearic acid (Armour & Co. Neo Fat 1-65), 150 g. commercial xylene and 6 g. boron trioxide. The mixture was heated at reflux-173 to 190 C. for 20.5 hours dropping water and some xylene during this time. Then 4 g. more of boron trioxide were added and the mixture was refluxed for an additional 12.75 hours. A total of 18 cc. of Water were obtained. The mass was then blown with nitrogen for 15 minutes at 265 C. to remove the xylene. The product (sample 105) weighed 552 g. Part of the product was treated with 8 times its weight of hot hexane. It was cooled to room temperature and filtered. The filtrate was evaporated to dryness to give sample 106. The hexane insoluble portion was treated with hexane again to give an extract, sample 107. Properties of the phenothiazine amides are reported in Table I.

Table I Saponification Sam- N 0. Acid Per- Acid Used ple No. cent No. Yield Theo. Actual Laurie 78 140 119 11 100 Laurie Hexane Purified 80 147 133 3. 2 46 Stearic 105 97 99 8. 7 96 Stearic Hexane Extract 1st 106 112 115 19 37 Stearic Hexane Extract 2nd. 107 112 109 5. 2 25 Blends of various proportions of the phenothiazine amides were made with various mineral oil lubricants. Table II reports the results of tests made upon some of these blends containing a lubricating oil having a viscosity of 150 SUS at 100 F. The tests were conducted by placing a 100 ml. portion of a blend in a beaker which contained a weighed amount of copper and lead particles. Air was bubbled into the liquid at a rate of 5 liters per hour. Pentane insolubles were determined by centrifug- A blank was run on a portion of lubricating oil which contained no phenothiazine amide inhibitor.

Table II FIVE HOURS OXYGEN ABSORPTION TEST 360 F. (OnPb) Amid1e 3 ement 0 Ab P t 1793 8 1 1 0 A 'd 1 f- Sam e one. in cc. ercen ge. 5 c1 Phenothiazme Am de 0 N o sorl ed Vis. Rise (Milli- Insol. No.

grams) Laurie Acid 78 0.5 240 6. 3 5. 6 0. 35 0.65

t A d 11 ac Blai cl em 6 1 2,200 in 2.5 19. 0 +11. 8 0. 52 3. 7

thiazine, (N.F. grade), 200 g. (1 mole) lauric acid (Eastman Kodak Co. red label grade) and 100 g. of commercial xylene. The mixture was heated to reflux at 193 C. over /2 hour and 57 g. xylene were removed in order to increase the reflux temperature. It was then refluxed at 255 C. Heating was continued for 20.5 hours dropping xylene and water during this time, and raising the reflux temperature to 295 C. A total of 15.5 cc. of water were removed. The mass was then blown with nitrogen at 250 C. until no odor of xylene could be detected. The dark brown product Weighed 394 g. (sample 78). Some of this product was purified by dissolving it In another high temperature oxidation test, a 1% solution of crude lauric acid amide of phenothiazine in a solvent treated Mid-Continent neutral oil having a viscosity of about 600 SUS at 100 F. and viscosity index, proved far superior to the neat oil. In this test 20 cc. of the oil was dripped over a 6" x 3" inclined piece of tared aluminum foil, over 5 hours, at 425 F. The foil increased in weight 38 milligrams when using the inhibited oil and over mg. when using the neat oil.

These oxidation inhibitors were found to be efliective 75 in preserving the oxidation stability of greases exposed to high temperatures. For examnlsa, greases were prepared having the following;

Composition Parts By Weight Sample N A B Li soap of-12-OH- stear-io acid 15. 15. 0Q di-isooetyl, a zelate 83. 78 84. 78 Water. L 0. 07 0. 07 Freooleic acid" 0. 15. i 0.15 Pheuothiazinestearyl amide. 1. 00-

NORM OFFMAN 13 MB: OXIDATION.

100 hours-.- 2

130 hours 55 I claim;

1. A lubricant composition consisting essentially of a lubricant base, selected; from the group consisting of mineral oil lubricants and synthetic, ester oil. based metal soap thickened; greases, and an oibcompatible fatty acid amide of phenothiazine, wherein the fatty acid radical contains 10 to 32 carbon atoms, in an amount sufficient to give improved oxidationw stability in. the empe atu e range of about 300 to 450 F.

-2. The composition of claim 1 in which the lubricant base a mineral oil lubricant.

present in a range of about 0.1 to 2%.: Of the, total; lu-

blfieant, composition.

8. The composition. of claim 3 where the fatty acid radical is that of lauric acid.

9., The composition of claim 3, where the fattycid radical is that of steanic acid. 7

References Cited in the file of this patent,

' UNITED STATES PATENTS Moore et a1. Sept. 15 .1953 2,693,449 Hain et a1. Nov. 2, 1954 2,813,828.

Woods et a1 Nov. 19;"195-7 OTHER REFERENCES Murphy. et a1.: Mode of 'Action. of Phenothiazine Type Antioxidants, Ind. and Eng. Chem vol. 42,.No. 12, pp. 2479-89.

Claims (1)

1. A LUBRICANT COMPOSITION CONSISTING ESSENTIALLY OF A LUBRICANT BASE SELECTED FROM THE GROUP CONSISTING OF MINERAL OIL LUBRICANTS AND SYNTHETIC ESTER OIL BASED METAL SOAP THICKENED GREASES, AND AN OIL-COMPATIBLE FATTY ACID AMIDE OF PHENOTHIAZINE, WHEREIN THE FATTY ACID RADICAL CONTAINS 10 TO 32 CARBON ATOMS, IN AN AMOUNT SUFFICIENT TO GIVE IMPROVED OXIDATION STABILITY IN THE TEMPERATURE RANGE OF ABOUT 300 TO 450*F.