US3655562A

US3655562A - Stable synthetic ester lubricant composition

Info

Publication number: US3655562A
Application number: US3203A
Authority: US
Inventors: Tai S Chao; Allan N Roush
Original assignee: Atlantic Richfield Co
Current assignee: Atlantic Richfield Co
Priority date: 1970-01-15
Filing date: 1970-01-15
Publication date: 1972-04-11
Anticipated expiration: 1989-04-11
Also published as: CA926376A

Abstract

A normally-liquid, synthetic ester base lubricant composition having enhanced oxidation retardation at temperatures greater than 400* F. is disclosed. The composition contains, in addition to the base lubricant, minor amounts of an alpha-alkyl styrenated aromatic amine which is the condensation product of (1) a secondary aromatic mono or diamine having non-olefinic, nonacetylenic hydrocarbon radicals of about one to 20 carbon atoms and at least one non-olefinic, non-acetylenic aromatic hydrocarbon radical of about six to 16 atoms attached to an amine group, and (2) an alpha-alkyl styrene, particularly an alphalower alkyl styrene.

Description

United States Patent Chao et al. [45] Apr. 11, 1972 [54] STABLE SYNTHETIC ESTER 3,282,840 11/1966 Foster et al ..252/s0 LUBRICANT COMPOSITION 3,347,791 10/1967 Thompson et al. ....252/s0 x 5, 1 [72] Inventors: Tai S. Chao, l-lomewood; Allan N. Roush, 3 53 243 0/1970 Chao et al 252/50 x Park Forest both of Primary Examiner-Daniel E. Wyman [73] Assignee: Atlantic Richfield Company, New York, AssistantExaminer-W. J. Shine N.Y. Attorney-McLean, Morton and Boustead [22] Filed: Jan. 15, 1970 [57] ABSTRACT [21] Appl 3203 A normally-liquid, synthetic ester base lubricant composition having enhanced oxidation retardation at temperatures [52] US. Cl. ..252/51.5 A, 252/50 greater than 400 F. is disclosed. The composition contains, in II!!- Cl. addition to the base lubricant minor amounts of an alpha- Fleld of Search ..252/50, A, Styrenated aromatic amine is the condensation product of (1) a secondary aromatic mono or diamine having [56] References cued non-olefinic, non-acetylenic hydrocarbon radicals of about UNITED STATES PATENTS one to 20 carbon atoms and at least one non-olefinic, nonacetylenlc aromatlc hydrocarbon radical of about SIX to 16 Cralg atoms attached to an amine group and an alpha alkyi 3,004,916 10/1961 Ertelt ..252/50 X tyre e, articularly an alpha-lower alkyl styrene, 3,121,691 2/1964 Eickemeyer ..252/50 X 3,210,281 10/1965 Peeler ..252/50 12 Claims, No Drawings STABLE SYNTHETIC ESTER LUBRICANT COMPOSITION This invention relates to ester-based lubricant compositions containing a novel combination of additive agents. More particularly, the present invention is concernedv with estenbased lubricant compositions which exhibit increased oxidation resistance and decreased deposit-forming tendencies.

Organic compounds, such as lubricating oils, undergo oxidation upon exposure to air. This process is accentuated by elevated temperatures such as occur in engines and other operating machinery. When such organic compositions are used as engine or machinery lubricants, their stability is still further drastically reduced due to their contact with metal surfaces which give up metallic particles into the lubricant. Such abraded or dissolved metals or metal salts appear to act as oxidation catalysts in the lubricant causing the formation of primary oxidation products, which, in turn, cause further degradation of the. organic compounds present in the composition. Problems of this nature are encountered in mineral oils, butare also troublesome in synthetic oleaginous fluids, exemplified by esters, when used under relatively high temperature conditions. i

The development of modern high speed jet turbine aircraft engines necessitates the search for lubricants which are resistance to high temperature oxidative degradation. Jet turbines are actuated by the energy of a burning fuel and are used to drive compressors which providelarge amounts of air for the burning of the fuel. The combustion of the fuel provides the energy for driving the compressors with the remainder of the useful energy going into the propulsion of the aircraft. Jet turbine bearings are lubricated by pumping a lubricant to the bearings from a reservoir in a closed system. The design of more powerful jet turbines has led to an increase in the lubricant reservoir temperatures as well as the temperature of the bearings and various heat sections. This causes greater difficulty in maintaining lubricant stability under the more severe conditions. For example, a lubricant which will operate satisfactorily at a reservoir temperature of, say, 250' F. may sludge badly, build up viscosity, develop high acidity and corrode metal at a reservoir temperature of, say, 400 F Thus, jet turbine service requires a lubricant of superior thermal and, oxidation stability as well as satisfactory physical characteristics in terms of viscosity, flash point, volatility, and load carrying properties. To arrive at such a lubricant it has been the general practice to add antioxidants and other additives, such as foam inhibitors, anti-wear agents, etc., to a base fluid of suitable properties.

Numerous oxidation and corrosion inhibitors have been found for use in ester-based lubricating compositions and many combinations thereof also have been tested. For instance, anti-oxidants such as phenothiazine, N-phenyl-anaphthylamine, N-pheynl-B-naphthylamine; p,p-dioctyldiphenylamine, S-ethyll 0,lO-diphenylphenazasiline, etc., are well known in the art. The ester lubricants may also contain anti-scuff agents, such as long-chain dibasic acids or PHOsphate esters such as tricresyl phosphate. The known inhibitors, however, are not adequate to provide the superior oxidation resistance and engine cleanliness needed for more advanced gas turbine engines. These engines, as typified by those required for supersonic transport, stationary power generation and the more severe subsonic transport useage, require synthetic lubricants of extremely low deposit-forming tendency as well as superior oxidation resistance.

The present invention provides a synthetic esterof lubricating viscosity which exhibits increased resistance to oxidation and deposit formation at temperaturesgreater than 400 F., say in the range above 400 to about 700 F. The present lubricating composition is more resistant to oxidation and deposit formation than similar esters'containing amines such as Naphenyl-a-naphthylamine, Nphenyl-B-naphthylamine, phenothiazine, etc. More particularly, it has been discovered by the present invention that oil-soluble alpha-alkyl styrenated aromatic mono and diamines which are the condensation products of a secondary aromatic mono or diamine and an alpha-alkyl styrene, particularly alpha-lower alkyl styrene, are particularly effective in imparting to synthetic ester lubricants increased resistance to oxidation and decreased deposit-fonning tendencies than presently known lubricants.

The amine condensation products used in this invention can be obtained by reacting an excess, e.g. about 10 to percent excess, of an alpha-alkyl styrene, e.g., a-methyl styrene, with a secondary aromatic mono or diamine in the presence of a catalyst such as BF; etherate. The reaction can be carried out by dissolving the amine in a suitable solvent such as nitrobenzene, adding a small amount, e.g., about 0.5 to 10 percent of BF:, etherate, heating to a temperature of about 50 C., and adding the alpha-alkyl styrene dropwise over a period of time, with adequate stirring. Or, in the alternative, the amine can be melted and the reaction carried out in the absence of solvents. When the addition is completed, the mixture can be heated for a few hours to complete the reaction andthe excess reactants and catalysts then removed. Excess alpha-alkyl styrene can be removed by distillation, preferably under vacuum. The BF etherate catalyst can be removed by blowing with nitrogen, washing with water, or precipitating as an NH; complex. The excess amine can be removed by vacuum distillation or can be left in the finished product. Since the alpha-alkyl styrene has a tendency to polymerize during the reaction, it is preferable to add a small amount of polymerization inhibitor such as t-butyl catechol before the reaction and before distillation. The finished product can be purified by high temperature vacuum distillation and by filtration while dissolved in a non-polar solvent, such as xylene. In certain cases, such as with the condensation of a-methylstyrene with N-phenyl-a-naphthylamine, the product can be purified by recrystallization. However, condensation products which, contain major portion of the monocondensation products and minor proportions of polycondensation products, some starting aromatic amine and polyalkyl styrene, F and Zn compounds can be acceptable for use as lubricant additives.

The styrene component suitable for reaction with the amine to form the condensation products of the present invention is an alpha-alkyl styrene in which the alkyl group has up to about 12 or 16 or more carbon atoms, preferably the group is lower alkyl, for instance, of about one to five carbon atoms. The most preferred alpha-alkyl styrene for use in this invention is alpha-methyl styrene.

The secondary aromatic mono and diamine components of the invention are soluble in the ester fluid at least to the extent used and can be represented by the following general formula:

wherein Q is a hydrocarbon radical of one to about 20 carbon s, preferably six to 12 carbon atoms, whose adjacent carbon atoms are no closer than 1.40 A. (i.e., a non-olefinic, nonacetylenic hydrocarbon), Q is a non-olefinic, non-acetylenic aromatic hydrocarbon radical of six to about 16 carbon atoms, preferably six to 12 carbon atoms, and Q" is a hydrocarbon radical of one to about 20 carbon atoms, preferably six to 12 carbon atoms, whose adjacent carbon atoms are no closer than 1.40 A. (i.e., a non-olefinic, non-acetylenic hydrocarbon). At least one non-olefinic non-acetylenic aromatic hydrocarbon radical of six to about 20 carbon atoms must be bound to the amino nitrogens in the mono and diamines, preferably at least one such aromatic radical to each nitrogen in the diamines. Thus, Q can be an alkyl, a cycloalkyl or an aromatic group and Q" can be alkylene, a cycloalkylene or a divalent aromatic group (arylene). Preferably, Q, Q and Q" are all aromatic and often at least one is a fused ring aromatic, e.g., naphthyl. Also, Q, Q and Q" can be substituted with non-interfering groups such as alkyl or aryl groups; Q, Q and Q. can be linked together by means of a non-interfering element such as carbon, sulfur or oxygen. Further illustrative of the groups representing Q are hexyl, heptyl, octyl, decyl, dodecyl, hexadecyl, octadecyl, phenethyl, phenheptyl, cyclohexyl, cyclooctyl, 4-butyl cyclohexyl, phenyl, anaphthyl, ,B-naphthyl, biphenyl and p-octyl phenyl. Illustrative of groups representing Q are phenyl, a-naphthyl, B-naphthyl, biphenyl and p octyl phenyl. Illustrative of groups representing Q" are p-phenylene, naphthyl-ene, biphenylene, octylene, ethylene and Z-methyl hexylene. Illustrative of suitable specific amines are phenothiazine; N-phenyl-a-naphthyl amine; N-phenyl-B-naphthyl amine; N-octyl-B-naphthyl amine; diphenylamine; di-a-naphthyl amine, di-B-naphthyl amine; N ,Ndiphenyl-p-phenylene diamine; N,N-diphenyloctylene diamine; N-p-octyl-phenyl phenyl amine; di-p-octyl phenyl amine, N,N'-diheptyl-p-phenylene diamine, etc. The aromatic amine antioxidants are usually present in the lubricant composition in amounts of from about 0.1 to percent by weight of the final composition with a preferred amount being from about 0.5 to 3 percent by weight. For best results, the relative concentrations of the additive may vary with the particular lubricant employed and may also be dependent on the characteristics of the final lubricant composition desired. Often, it is preferred that the a-alkyl styrene to aromatic mono or diamine weight ratio in the condensation product be about 0.2 to 4:1, advantageously about 0.7 to 3:1.

The lubricant composition of this invention includes as the major component a base oil which is an ester of lubricating viscosity which may be, for instance, a simple ester or compounds having multiple ester groupings such as complex esters, dior other polyesters and polymer esters. These esters are usually made from monoand poly-functional aliphatic alcohols or alkanols, and aliphatic monoand polycarboxylic or alkanoic acids. Frequently, the alcohols and acids have about four to 12 carbon atoms. The reaction product of a monofunctional alcohol and a monocarboxylic acid is usually considered to be a simple ester. A diester is usually considered to be the reaction product of 1 mole of a dicarboxylic acid, say of six to 10 carbon atoms, with 2 moles of a monohydric alcohol, or of 1 mole of a glycol, for instance, of 4 to 10 carbon atoms, with two moles of monocarboxylic acid, e.g. of four to 10 carbon atoms. The diesters frequently contain from 16 to 40 carbon atoms.

A complex ester is usually considered to be of the type X Y Z Y X in which X represents a monoalcohol residue. Y represents a dicarboxylic acid residue and Z represents a glycol residue and the linkages are ester linkages. Those esters, wherein X represents a monoacid residue, Y represents a glycol residue and Z represents a dibasic acid residue are also considered to be complex esters. The complex esters often have 30 to 50 carbon atoms.

Polymer esters or polyester bright stocks can be prepared by direct esterification of dicarboxylic acids with glycols in about equimolar quantities. The polyesterification reaction is usually continued until the product has a kinematic viscosity from about to 20 centistokes at 210 F., and preferably about 40 to 130 centistokes at 210 F.

Although each of these products in itself is useful as a lubricant, they are particularly useful when added or blended with each other in synthetic lubricant compositions. These esters and blends have been found to be especially adaptable to the conditions to which turbine engines are exposed, since they can be formulated to give a desirable combination of high flash point, low pour point and high viscosity at elevated temperatures. In addition, many complex esters have shown good stability to shear. Natural esters, such as castor oil may be employed and also be included in the blends, as may be small amounts of a foam inhibitor such as methyl silicone polymer or other additives of lubricant components to provide a particular characteristic; for instance, extreme pressure or load carrying agents, corrosion inhibitors, etc., can be added.

The monohydric alcohols employed in these esters usually contain about four to 20 carbon atoms and are generally aliphatic. Preferably, the alcohol contains up to about 12 carbon atoms. Useful alkanols include butyl, hexyl, n-octyl, isooctyl and dodecyl alcohols, C -oxo alcohols and octadecyl alcohols. C to C branched chain primary alcohols are frequently use to improve the low temperature viscosity of the finished lubricant composition. Alcohols such as n-decanol, 2- ethylhexanol or oxo alcohols prepared by the reaction of carbon monoxide and hydrogen upon the olefins obtainable from petroleum products such as diisobutylene and C olefins, ether alcohols such as butyl carbitol, tripropylene glycol monoisopropyl ether, dipropylene glycol mono-isopropyl ether and products such as Tergitol 3A3 which has the formula C l-I O(CI-I CH O) l-I, are suitable alcohols for use to produce the desired lubricant. If the alcohol has no hydrogens on the beta carbon atoms, it is nee-structured; esters of such alcohols are often preferred. In particular, the nee-C alcohol 2, 2, 4-trimethyl-pentanol-l gives lubricating diesters or complex esters suitable for blending with diesters to produce lubricants which meet stringent viscosity requirements. Iso-octanol and iso-decanol are alcohol mixtures made by the 0x0 process from C and C copolymer heptenes. The cut which makes up isooctanol usually contains about 17 percent 3,4-dimethylhexanol; 28 percent 3,5-dimethylhexanol; 25 percent 4,5- dimethylhexanol; 1.4 percent 5,5-dimethylhexanol; 16 percent of a mixture of 3-methylheptanol and S-ethylheptanol; 2.3 percent 4-ethylhexanol; 4.3 percent a-alkyl alkanols and 5 percent other materials.

Generally, the glycols contain from about four to 12 carbon atoms; however, if desired, they could contain a greater number. Among the specific glycols which can be employed are 2-ethyl-1,3-hexanediol; 2-propyl-3,3-heptanediol; 2- methyl-1,3-pentanediol; 2-butyl- 1 ,3-butanediol; 2,4-diphenyl- 1,3-butanediol and 2,3-dimesityl-l,3-butanediol. In addition to these glycols, ether glycols may be used, for instance, where the alkylene radical contains two to four carbon atoms such as diethylene glycol, dipropylene glycol and ether glycol up to about 1,000 to 2,000 molecular weight. The most popular glycols for the manufacture of ester lubricants appear to be polypropylene glycols having a molecular weight of about -300 and 2-ethyl hexanediol. The 2,2-dimethyi glycols, such as neopentyl glycol have been shown to impart heat stability to the final blends. Minor amounts of other glycols or other materials can be present as long as the desired properties of the product are not unduly deleteriously affected.

One group of useful monocarboxylic acids includes those of eight to 18 or even 24 carbon atoms such as stearic, lauric, etc. The carboxylic acids employed in making ester lubricants will often contain from about four to 12 carbon atoms. Suitable acids are described in US. Pat. No. 2,575,195, herein incorporated by reference, and include the aliphatic dibasic acids of branched or straight chain structures which are saturated or unsaturated. The preferred acids are the saturated aliphatic carboxylic acids containing not more than about 12 carbon atoms, and mixtures of these acids. Such acids include succinic, adipic, suberic, azelaic and sebacic acids and isosebacic acid which is a mixture of a-ethyl suberic acid, a,a-diethyl adipic acid and sebacic acid. This composite of acids is attractive from the viewpoint of economy and availability since it is made from petroleum hydrocarbons rather than the natural oils and fats which are used in the manufacture of many other dicarboxylic acids, which natural oils and fats are frequently in short supply. The preferred dibasic acids are sebacic and azelaic or mixtures thereof. Minor amounts of adipic used with a major amount of sebacic may also be used with advantage.

The ester base oils to which incorporation of the additive combination of the invention is especially advantageous are the oils commonly referred to as neo-structured polyol polyesters i.e. having more than one ester group. These are the esters of aliphatic carboxylic acids, generally monoalkanoic acids, of about four to 12 carbon atoms, and a polyhydric alkanol free of beta hydrogen, i.e. containing no hydrogen on the beta carbon atoms, and including the di(polyhydric alcohol )ethers. The polyhydric alcohol generally contains about two to six hydroxy groups and about five to 20, preferably about five to 12, carbon atoms. Illustrative of the alcohols are those having the general formula:

wherein n is 0 to 1 and R is a lower alkyl group, preferably of about one to five carbon atoms, which can be straight or branched chain, or a hydroxy lower alkyl, e.g. hydroxy methyl, group. These esters can be made by reacting a mole of the alcohol with about 2 moles up to the stoichiometric equivalent of the carboxylic acid.

Illustrative of polyhydric alcohols free of beta hydrogen are neopentyl glycol, trimethylolethane, trimethylolpropane, pentae rythritol, dipentaerythritol, 2-butyl-2-ethy1-l ,3- propanediol, etc. Suitable aliphatic carboxylic .acids with which the polyhydric alcohols free of beta hydrogen may be esterified, are n-butyric acid, isobutyric acid, valeric acid, isopentanoic acid, caproic acid, isohexanoic acid, n-heptanoic acid, isoheptanoic acid, neoheptanoic acid, n-octanoic acid, isooctanoic acid, pelargonic acid, n-decanoic acid, isodecanoic acid neodecanoic acid, lauric acid, myristic acid, stearic acid, isostearic acid, etc.

Other additives, such as anit-scuff and anti-fatigue additives, corrosion inhibitors, anti-foam agents, etc., can also be advantageously used with the amines of the present invention. The viscosity of the lubricating oil containing the additives is preferably less than about 13,000 centistokes at -40 C.

The invention will be better understood by reference to the following examples:

Examples I to III are directed to the preparation of the alpha-alkyl styrenated aromatic amines.

EXAMPLE I A 500 ml, 4-necked flask was equipped with a mechanical stirrer, a dropping funnel and a reflux condenser. N-phenyl-anaphthylamine (109.5 g. or 0.5 moles, technical grade, Du- Pont) was charged into the flask and melted at 95 C. With constant stirring, 4.3 ml. of BF -ethereate as added. From the dropping funnel 71 g. (0.60 mole, percent excess) of amethylstyrene (containing 0.7 g. of t-butyl catechol) was added over a period of one hour. The temperature rose to l00-l.l0 C. The reaction mixture was stirred one hour longer at 100-l10 C. and two hours at 150 C. It was then blown with nitrogen while heating gradually to 220 C. to remove BF and topped to 190 C./ 1 mm. to remove 28 g. of unreacted material. The residue was a light brown solid weighing 143 g. showing the following analysis: C, 89.08; H, 6.94; N, 4.01. A portion of this solid was recrystallized in hexane to give grayish crystals having m.p. 29-3 1 and showing the following: C, 89.18; H, 6.80; N, 4.44. Theoretical calculations for the structure 1, below, indicate the following: C, 89.0; H, 6.83; N, 4.16. Mass spectroscopy showed the recrystallized solid to contain 98 percent of the structure I. NMR showed the recrystallized solid to contain an average of. one ot-methylstyrene group per mole of N-pheynla-naphthylamine JHa I EXAMPLE II Font). The amine was melted at and 166 ml. of BF; etherate was slowly added. The temperature was sustained at 100-l102,480 g. (20 percent excess) of a-methylstyrene and 28 g. of t-butyl-catechol was added, with constant stirring, over a period of 1 hour. The mixture was further heated for one hour at -150 C.; then the temperature was raised slowly to 200-210, while a stream of nitrogen was blown through the reaction mixture. When fumes of BF; were no longer evident (3-4 hours), the mixture was topped to 260/0.25 mm. to recover 910 g. of unreacted material. The residue, 5,980 g. of a dark red viscous liquid, was combined with 1,601 g. of a previous batch prepared in the same manner. The combined material showed the following analysis: C, 88.78; H, 6.85; N, 4.24.

The material also showed the presence of 50 p.p.m. of B, 149 p.p.m. of F, and 0.166% Zn. The material was purified by dissolving in xylene and removing the insoluble material by filtration. The purified material showed the following analysis: C, 89.05; H, 6.75; N, 4.31; 2 ppm B; 46 p.p.m. F and 0.071% Zn. The Zn came from the technical grade N-phenyl- B-naphthylamine used, and, at the level present, showed no adverse effect on performance of the finished lubricant. The C, H, N analyses are comparable to those calculated for structure II C, 89.0; H, 6.83; N, 4.10) below. However, NMR and mass and IR spectroscopy showed that the product also contained minor amounts of unreacted N-phenyl-flnaphthylamine, disubstitution products and poly-a-methylstyrene. This impure product is called a-methylstyrenated PBN. The presence of these impurities showed no detrimental effect on its performance in the present usage.

The benefits derived from the use of the amines described above in Examples 1 to III in place of conventional anti-oxidants such as N-phenyl-a-naphthylamine can be seen from Examples IV through VIH.

EXAMPLE IV Table I shows the antioxidant effectiveness of the additives of the present invention when used in synthetic ester-based lubricating compositions. The Type 2 Bearing Rig Test was conducted under conditions specified by Pratt and Whitney.

TABLE I Type 2 Bearing Rig Test Data Sample No. 1 2

Composition Wt. Wt. Hercolube 1"" 94.67 93.97 N-phenyl-unaphthylamine 1.30 a-Methylstyrenated PBN 2.00 Dioctyldiphenylamine 1.00 1.00 Tricresyl phosphate 3.00 3.00 Ouinizarin 0.03 0.03 D.C. Fluid (200 c.s., 60,000 MW)" 0.002 0.002

Bearing Rig Test Results WADD demerit rating 92 54 Viscosity lnc. KV 100, 91 646 91 Final Acid No., pH 11 7.17 3.57 100 Mesh Filter deposits, gms. 6.179 2.165

Conditions Duration, 100 hours (15 hr. Bearing Speed 10,000

intervals) r.p.m. Bearing Temp. 500F. Bearing load 500 lbs. Oil-in Temp. 400F. Oil Flow 600 mltlminv Sump Temp. 440F. Airflow 9,900 mL/min.

a) A pentaerythritol-dipentaerythritol ester ofa mixture ofC -C fatty acids.

b) A silicon containing anti-foam agent.

EXAMPLE V Table 11 shows, in another manner, the lower deposit-forming tendency of the additives of the present invention when used in the same synthetic ester base lubricating composition as used in Example IV. The High Temperature Deposition Test was conducted under conditions specified by the Alcor lnc. Technical Documentary Report No. APL-TDR-64-49. This High Temperature Deposition Test has been shown to have a good correlation with Bearing Rig and Engine Test results.

TABLE 11 High Temperature Deposition Test Sample No. l 2

Test No. I 11 Critical Temp. F. 575 630 610 Deposit rating 33.7 13.5 10.2 Tube deposits, mg. 49 10 2 Filter deposits, mg. 25 19 43 Overall rating 52.8 213 27.6 Sludge brown sludge none none The test results reported in Table 11 show significantly better performance in terms of lower deposit-forming tendencies of synthetic ester based lubricating oils containing the additives of this invention (Oil 2), when compared to the same ester based lubricating oil containing the commercially available additive.

EXAMPLE VI Table 111 shows the results of another test for measuring the deposit-forming tendencies of synthetic ester based lubricants containing the additives of the present invention. The Eppi Vapor Phase Coker Test was conducted under the following conditions: One liter of oil was heated to 400 F. and bubbled with 0.027 ft. 3/hr. of air for 17 hours. The resultant oil mist was led into a breather tube maintained at 700 F. After the test, the breather tube was cut into two halves and the weight of deposits determined.

(21) A mixture ofpentaerythritol and dipentaerythritol esters ofC,-C fatty acids.

The results reported in Table 111 clearly show that the oil containing 2 percent of the a-methylstyrenated PBN of the instant invention gave less deposits than the one containing 1% of the currently commercially available N-phenyl-anaphylamine.

EXAMPLE VII Table IV shows the antioxidant effectiveness of the additives of the present invention when used in synthetic ester based lubricating compositions and tested under the Type 2 Erdco Bearing Test condition specified by Pratt and Whitney as in Example 1V.

TABLE IV Type 2 Bearing Rig Test Data Sample No. 5

Composition Wt. Hercolube A"" 75.58 Hercolube F"" 1995 a-methylstyrenated PAN 2.00 Dioctyldiphenylamine 1.00 Tetrabutyl EDTA L00 Monoamide of hydrogenated dimer acid 0.20 Na perfluorobutyrate 0.12 Ouinizarin 0.03

Bearing Rig Test Results WADD demerit rating 41 Viscosity, lnc., KV/lOO", 38 Final Acid No., pH 11 0.71 mesh filter deposit, gmt 3.344

(a) Mixtures of pentaerythritol and dipentaerythritol esters ofC,-C fatty acids.

The results as indicated in the above Table IV show the lubricating composition of this example to be a significantly superior oil when compared to most Type 2 jet engine lubricants that generally have a demerit rating in the range of 60-100, as compared to the demerit rating of the present composition of41. This is clearly an improvement over the typical commercially available Type 2 jet engine lubricants.

EXAMPLE vrn A much more severe test for thermal and oxidative stability of synthetic lubricants than those of the previous Examples is the Type 2% Bearing Rig Test. In this test, the bearing temperature, the temperature of oil going into the bearing head, and the sump temperature are all 50 F. higher than those used in the Type 2 Bearing Rig Test.

As evidenced by the data presented in the following Table V, a synthetic ester based Type 2 lubricant currently available undergoes severe decomposition when subjected to the Type 2% Bearing Rig Test.

TABLE V Type 2-1/2 Bearing Rig Test Data Comparison The performance of the currently available Type 2 lubricant of Table V is sharply in contrast to the ester based synthetic lubricant containing the additives of this invention as exemplified in Table VI below:

TABLE VI Type 2 l; Bearing Rig Test Data Sample No. 6

Composition wt. Base Fluid C"" 95.17

a'methylstyrenated PBN 1.83

Dioctyldiphenylamine 1.00 Tetrabutyl ester of EDTA 1.50 Monoamide of hydrogenated dimer acid 0.20 Na pertlurobutyrute 0.15 DC Fluid (200 c.s., 60,000 MW) 0.001

Bearing Rig Test Results WADD demerit rating 102 Viscosity increase, KV/100, 7: 104 Final Acid No., pH 11 1.16 100 mesh filter deposit, gms. 14.26

(a) A pentaerythritol ester of a mixture of about equal molar proportions of neoheptanoic and n-valeric acids.

Table VI shows the superior performance of the lubricating composition of the present invention over that of the currently available Type 2 lubricant of Table V. The demerit rating of our lubricant is 102 as compared to the demerit rating of 177 in the commercial lubricant; and the composition of the present invention exhibits a viscosity increase (KV/ final acid number and 100 mesh filter deposit of 104, 1.6, and 14.26, respectively, as compared to 13,257, 4.09, and 3,657, respectively, for the commercially available type 2 lubricant under the conditions of the type 2% Bearing Rig Test.

it is claimed:

1. A normally liquid, synthetic ester based, high temperature lubricant composition comprising a major amount of an ester base oil of lubricating viscosity having dissolved therein a minor amount, sufficient to retard oxidation of the composition, of an alpha-alkyl styrenated amine which is the condensation product of a secondary aromatic monomine of the formula:

wherein Q is a non-olefinic, non-acetylenic hydrocarbon of one to about 20 carbon atoms and Q is a non-olefinic, nonacetylenic aromatic hydrocarbon of six'to about 16 carbon atoms or a secondary aromatic diamine of the formula:

wherein Q is a non-olefinic, non-acetylenic hydrocarbon of one to 20 carbon atoms and Q is a non-olefinic, nonacetylenic hydrocarbon of l to about 20 carbon atoms provided that at least one Q or Q is an aromatic hydrocarbon of six to about 20 carbon atoms, and an alpha-alkyl styrene, wherein the alkyl group has up to about 12 carbon atoms and the alpha-alkyl styrene to aromatic amine weight ratio in the condensation product is about 0.2 to 4:1.

2. A lubricant composition of claim 1 wherein the alphaalkyl styrene is alpha-methyl styrene.

3. A lubricant composition of claim 1 wherein the aromatic amine is an aromatic monoamine.

4. A lubricant composition of claim 3 wherein the aromatic monoamine is selected from N-phenyl-a-naphthylamine, N- phenyl-fi-naphthylamine, di-a-naphthylamine or di-B- naphthylamine.

5. A lubricant composition of claim 4 wherein the aromatic monoamine is N-phenyl-B-naphthylamine.

6. A lubricant composition of claim 4 wherein the alphaalkyl styrene is alpha-methyl styrene.

7. A lubricant composition of claim 1 wherein the alphaalkyl styrenated amine is present in an amount of about 0.5 to 3 percent by weight of the composition.

8. A lubricant composition of claim 1 wherein the base oil is an ester of a monoalkanoic acid of about four to 12 carbon atoms and a polyhydric alcohol having no hydrogen on beta carbon atoms, two to six hydroxyl groups and about five to 12 carbon atoms.

9. A lubricant composition of claim 8 wherein the polyhydric alcohol is pentaerythritol or dipentaerythritol.

10. The composition of claim 8 wherein the aromatic amine is selected from N-phenyl-anaphthylamine, N-phenyl-B- naphthylamine, di-a-naphthylamine or di-B-naphthylamine.

11. The composition of claim 10 wherein the alpha-alkyl styrenated amine is present in an amount of about 0.5 to 3 percent by weight of the composition.

12. The composition of claim 11 wherein the alpha-alkyl styrene is alpha-methyl styrene and the aromatic amine is N- phenyl-B-naphthylamine.

Notice of Adverse Decision in Interference In Interference No. 98,432, involving Patent No. 3,655,562, T. S. Chao and A. N. Roush, STABLE SYNTHETIC ESTER LUBRICANT COM- POSITION, final judgment adverse to the patentees was rendered Mar. 12, 1975, as to claim 3.

[Ofiicz'al Gazette August 5,19 5.]

Claims

2. A lubricant composition of claim 1 wherein the alpha-alkyl styrene is alpha-methyl styrene.
3. A lubricant composition of claim 1 wherein the aromatic amine is an aromatic monoamine.
4. A lubricant composition of claim 3 wherein the aromatic monoamine is selected from N-phenyl- Alpha -naphthylamine, N-phenyl- Beta -naphthylamine, di- Alpha -naphthylamine or di- Beta -naphthylamine.
5. A lubricant composition of claim 4 wherein the aromatic monoamine is N-phenyl- Beta -naphthylamine.
6. A lubricant composition of claim 4 wherein the alpha-alkyl styrene is alpha-methyl styrene.
7. A lubricant composition of claim 1 wherein the alpha-alkyl styrenated amine is present in an amount of about 0.5 to 3 percent by weight of the composition.
8. A lubricant composition of claim 1 wherein the base oil is an ester of a monoalkanoic acid of about four to 12 carbon atoms and a polyhydric alcohol having no hydrogen on beta carbon atoms, two to six hydroxyl groups and about five to 12 carbon atoms.
9. A lubricant composition of claim 8 wherein the polyhydric alcohol is pentaerythritol or dipentaerythritol.
10. The composition of claim 8 wherein the aromatic amine is selected from N-phenyl- Alpha naphthylamine, N-phenyl- Beta -naphthylamine, di- Alpha -naphthylamine or di- Beta -naphthylamine.
11. The composition of claim 10 wherein the alpha-alkyl styrenated amine is present in an amount of about 0.5 to 3 percent by weight of the composition.
12. The composition of claim 11 wherein the alpha-alkyl styrene is alpha-methyl styrene and the aromatic amine is N-phenyl- Beta -naphthylamine.