US3150092A

US3150092A - Lubricant composition

Info

Publication number: US3150092A
Application number: US34882A
Authority: US
Inventors: Daniel B Eickemeyer; James E Engelking
Original assignee: Sinclair Research Inc
Current assignee: Sinclair Research Inc
Priority date: 1960-06-09
Filing date: 1960-06-09
Publication date: 1964-09-22
Anticipated expiration: 1981-09-22

Description

United States Patent 3,150,092 LUBRECANT COMPOSITION Daniel B. Eickemeyer, Park Forest, 111., and James E.

Engelking, St. Paul, Minn., assignors, by mesne assignments, to Sinclair Research, Inc, New York, N.Y., a

corporation of Delaware No Drawing. Filed June 9, 1%0, Ser. No. 34,882 2 Claims. (Cl. 252-463) This invention relates to ester-based lubricant compositions and more particularly to ester-based lubricant compositions containing phenothiazine and a base oilsoluble S-alkyl-lO,10-diphenyl-phenazasiline which have improved resistance to oxidation.

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 motor 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. In addition, Water also causes corrosion of metallic surfaces and accentuates oxidation of the lubricant. Problems of this nature are encountered in mineral oils but appear to be particularly troublesome in synthetic oleaginous fluids exemplified by esters. These synthetic fluids are not sufficiently resistant to oxidation to be useful alone.

They can, however, be adequately protected by use of small amounts of additives. Phenothiazine has been employed extensively to protect synthetic fluids against oxidation. Its activity, however, is not great enough to protect fluids for long periods of time above about 400 F.

It is the particular object of the present invention to provide an ester oil of lubricating viscosity that exhibits increased resistance to oxidation. Further, the additives of the present invention have proven far more effective than the conventional use of phenothiazine alone in reducing oxidation in synthetic ester fluids.

The present invention provides an improved esterbased lubricant composition containing phenothiazine and a -alkyl-l0,10-diphenyl-phenazasiline wherein the alkyl group is a lower alkyl group i.e. generally of about 1 to 4 carbon atoms, preferably 2 carbon atoms. The rings of the latter compound may be substituted as for instance with alkyl groups. The additives of the present invention are used in minor amounts that provide a final esterbased synthetic lubricant composition exhibiting increased.

resistance to oxidation under temperatures such as in excess of 400 F. The amounts added shouid be solublein the base oil into which they are introduced and these amounts may vary'with the particular base oil utilized. Generally the 5alkyl-10,IO-diphenylphenazasiline component of this invention is added in amounts from about .01 to 5 percent by weight of the final composition'with a preferred amount being about-0.1 to 2 percent by weight.

meta to the nitrogen. The relative concentrationstof the additives may varywith the particular ester lubricant,

employed and-also be dependent upon the characteristics of the final lubricant composition desired. Normally, it

preferably about 20 to 35 weight percent.

3,15%,(992 Patented Sept. 22, 1964 are made from monoand polyhydroxy aliphatic alco hols and aliphatic carboxylic acids, frequently of about 4 to 12 carbon atoms; aliphatic including cycloaliphatic. The reaction product of a monohydroxy 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 6 to 10 carbon atoms with 2 moles of a monohydric alcohol of, for instance 6 to 12 carbon atoms or of 1 mole of a glycol of 4 to 10 carbon atoms with two moles of a monocarboxylic acid of 4 to 10 carbon atoms. The diesters frequently contain from 20 to 40 carbon atoms. One complex ester is usually considered to be of the type XYZY-X in which X represents a monohydric alcohol 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. Polyesters, or polyester bright stocks can be prepared by direct esterification of dibasic acids with glycols in about equimolar quantities. The polyesterification reaction is usually continued until the product has a kinematic viscosity from about 15 to 200 centistckes at 210 F, and preferably 40 to 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, and need contain no additives which might leave a residue upon volatilization. In addition, many complex esters have shown good stability to shear. Natural esters, such as castor oil may also be includedin the blends, as may be up to about 1 percent or more by weight of a foam inhibitor such as a methyl silicone polymer or other additives to provide a particular characteristic, for instance,

extreme pressure or load carrying agents, corrosion in-' plex ester at an elevated temperature, altering the proportions of each component until the desired viscosity is reached. Polyesters can be employed to thicken diester base' stocks to increase the load carrying capacity of the base diester oil. The polyester will generally not comprise more than about 50 weight percent of the blend,

amount of the polyester employed in any blend would be at least about 5 percent, and the majority of the lubrif jcant is a diester. Other polymers such as the acryloids may be added as thickeners to the esters, generally the single esters to obtain a base oil of desired viscosity."

The acryloids are polymers of mixed C to C esters of methacrylic acid having a 16,000 to 20,000 molecular weight. Advantageously the final lubricating oil compo- 'sition would have a maximum viscosity at 40 F. of

Usually the F about 13,000 centistokes and a minimum viscosity of about 7.5 centistokes at 210 F.

The monohydrice alcohols employed in these esters usually contain less than about 20 carbon atoms and are generally aliphatic. Preferably the alcohol contains up to about 12 carbon atoms. Useful aliphatic alcohols include butyl, hexyl, methyl, iso-octyl, and dodecyl alcohols, C oxo alcohols and octadecyl alcohols. C to C branched chain primary alcohols are frequently used to improve the low temperature viscosity of the finished lubricant composition. Alcohols such as n-decanol, 2- ethylhexanol, 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 mono-isopropyl ether, dipropylene glycol mono-isopropyl ether, and products such as Tergitol 3A3, which has the formula C H O(CH CH O) H, 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; and esters of such alcohols are often preferred. In particular, the neo-C alco hol2,2,4-trimethyl-pentanol-l-gives lubricating diesters or gives complex esters suitable for blending with diesters to produce lubricants which meet stringent viscosity requirements. Iso-octanol and isodecanol are alcohol mixtures made by the x0 process from C C copolymer heptenes. The cut which makes up iso-octanol usually contains about 17% 3,4dimethylhexanol; 29% 3,5-dimethy1hexanol; 25% 4,5-dimethylhexanol; 1.4% 5,5-dimethylhexanol; 16% of a mixture of B-methylheptanol and -ethylheptanol; 2.3% 4-ethylhexanol; 4.3% a-alkyl alkanols and 5% other materials.

Generaliy, the glycols contain from about 4 to 12 carbon atoms; however, if desired they could contain a greater number. Among the specific glycols which can be employed are 2-ethyl-l,3-hexanediol, 2-propyl-3,3- heptane-diol, Z-methyl-l,B-pentanediol, 2-butyl-1,3-butanediol, 2,4-diphenyl-1,3-butanediol, and 2,4-dimesityl-1, 3-butanediol. In addition to these glycols, ether glycols may be used, for instance, where the alkylene radical contains 2 to 4 carbon atoms such as diethylcne glycol, di propylene glycol and ether glycols up to 1000 to 2000 molecular weight. The most popular glycols for the manufacture of ester lubricants appear to be polypropylene glycols having a molecular weight of about 100- 300 and 2-ethyl hexanediol. The 2,2-dimethyl glycols, such as neopentyl glycol have been shown to impart heat stability to the final blends. iinor amounts of other glycols or other materials can be present as long as the desired properties of the product are not unduly deleteriously affected. Aside from glycols, the esters may be made from polyhydric alcohols of more than two hydroxyl groups, e.g. tri and tetra hydroxy aliphatic alcohols having about 4 to 12 carbon atoms, preferably about 5 to 8 carbon atoms, for instance, pentaerythritol, trimethyloipropane and the like. Particularly suitable ester base oils are formed when these alcohols are reacted with monocarboxylic acids having about 4 to 12 carbon atoms, preferably 4 to 9 carbon atoms. It is preferred that the reaction be conducted so as to completely esterify the acids.

()ne group of monocarboxylic acids includes those of 8 to 24 carbon atoms such as stearic, lauric, etc. The dicarboxylic acids employed in making ester lubricants will in general contain from about 4 to 12 carbon atoms. Suitable acids are described in US. 2,575,195 and include the aliphatic dibasic acidsof branched or straight chain structures which are saturated or unsaturated. The preferred acids are the saturated aliphatic dicarboxylic 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, 0L.Z.-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 sup ply. 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.

Various useful ester base oils are disclosed in United tates Patents Nos. 2,499,983; 2,499,984; 2,575,195; 2,575,196; 2,703,811; 2,705,724 and 2,723,286. Generally the synthetic base oils consist essentially of carbon, hydrogen and oxygen, i.e. the essential nuclear chemical structure is formed by these elements alone. However, these oils may be substituted with other elements such as halogens, e.g. chlorine and fluorine. Some representative components of ester lubricants are ethyl palmitate: ethyl stearate, di-(Z-ethylhexyl) sebacate, ethylene glycol di-laurate, di-(Z-ethylhexyl) phthalate, di(1,3-methylbutyl) adipate, di-(2-ethylbutyl) adipate, di-(l-ethylpropyl) adipate, diethyl oxylate, glycerol tri-n-octoate, dicyclohexyl adipate, di-(undecyl) sebacate, tetraethylene glycol-di(ethyleno hexoate), diceliosolve phthalate, butyl phthallyl butyl glycolate, di-n-hexyl fumarate polymer, dibenzyl sebacate, and. diethylene glycol bis(2-n-butoxy ethyl carbonate). 2-ethylhexyladipate-neopentyl glycyladipate-Z-ethylhexyl, is a representative complex ester. Generally, these synthetic ester lubricants have a viscosity ranging from light to heavy oils, eg. about 50 SUS at F. to 250 SUS at 210 F, and preferably 30 to SUS at 210 F.

The esters are manufactured, in general, by mere reaction of the alcoholic and acidic constituents, although simple esters may be converted to longer chain components by transestcrification. The constituents, in the proportions suitable for giving the desired ester, are reacted preferably in the presence of a catalyst and solvent or water entraining agent to insure maintenance of the liquid state during the reaction. Aromatic hydrocarbons such as xylene or toluene have proven satisfactory as solvents. The choice of solvent influences the choice of temperature at which the esterification is conducted; for instance, when toluene is used, a temperature of 140 C. is recommended; with xylene, temperatures up to about 195 C. may be used. To provide a better reaction rate an acid esterification catal st is often used. Many of these catalysts are known and include, for instance, HCl, H 50 NaHSO aliphatic and aromatic sulfonic acids, phosphoric acid, hydrobromic acid, HF and dihydroxyfluoboric acid. Other catalysts are thionyl chloride, boron trifluoride, and silicon tetrailuoride. Titanium esters also make valuable esterification and tr-ansesterification catalysts.

In a preferred reaction, about 0.5 to about 1 weight percent, or advantageously, 0.2 to 0.5% of the catalyst is used with a xylene solvent at a temperature of to 200 C. while refluxing water. The temperatures of the reaction must be sufficient to remove the water from the esterification mass as it is formed. This temperature is usually at least about 140 C. but not so high as to decompose the Wanted product. The highest temperature needed for the reaction will probably be about 200 C., preferably not over about C. The pressure is conveniently about atmospheric. Although reduced pressure or superatmospheric pressure could be utilized, there is usually no necessity to use reduced pressurcs, as the temperatures required at atmospheric pressure to remove the water formed do not usually unduly degrade the product.

When reacting glycols with dibasic acids to produce a polyester, it is preferred to continue the reaction with concomitant boiling off of water from the reaction mixture until the polyester product has a kinematic viscosity of about 15 to 200 centistokes at 210F., preferably about 40 to 130 centistokes. When this point has been I reached, the polymerization can be-stopped, for instance,

by adding a capping alcohol to'the reaction mixture, and continuing a reflux until Water ceases to be evolved. The capping alcohol is a low molecular weight monoalcohol of up to about 20 carbon atoms. It is standard practice, when esters are made using the conventional acid catalysts such as sodium bisulfate or paratoluene- :sulfonic acid to give the esters an after-treat by washing the ester with a 5 percent aqueous K CO solution or by heating the ester in an autoclave for 15 hours at 340 to 350 F. with weight percent of propylene oxide. It is also conventional to subject the ester to filtration to re move insoluble materials. After this the product may be 6 EXAMPLE II Parts by wt. Plexol-255 1 97.75 Phenothiazine 0.5 Glycol titanate 2 0.25 Sebacic acid I .0075 D.C.F ZOO-60,000 .001 5-ethyl-10,10 diphenylphenazasiline 1.0

A mixture ofdiisooctyl adipate, di-tridecyl sebacate, and

EXAMPLE III subjected to a reduced pressure distillation or stripping Partsby wt. at 100 to 200 C. to remove volatile materials, such as Dllsooctyl fi at 25.5 Water, the solvent, and light ends. -1 f 1 73.0 Samples of ester fluids without an oxidation inhibitor Ph@n0ih1aZ 1ne 0.5 and samples containing phenothiazine alone, S-ethyl-lO, Free flZelalC acid 0.01 10 diphenyl phenazasiline alone and samples made ac- ,0 0 0.001 cording to the present invention containing varying pro- Y J dlphenylphenazasflme 1.0 portions Of 5-ethyl-10,10 diphenylphenazasiline a Derived from the reaction of one mole of neopentyl glycol, phenothiazine were Subjected to oxygemabsorpfion tests 2 moles of azelaic acid and two moles of isooctyl alcohol. The tests were conducted at 450 F. by passing a stream We claim: of oxygen at the rate of one cubic foot per hour through 1. A lubricant composition consisting essentially of an 75 grams of the ester fluid containing the inhibitors and ester-based fluid of lubricating viscosity and minor comparing the amount of oxygen absorbed vs. time. amounts effective to retard oxidation at temperatures in The induction period is signalled by a marked increase excess of 400 F., of about .01 to 5 percent by weight of in the rate or" oxygen absorption. The results of these phenothiazine and about .01 to 5 percent by weight of tests are shown in Table I. 5alkyl-10,1O diphenylphenazasiline wherein the alkyl TABLE I Results of Oxygen Absorption Tests 7 [Oonditionsz 450 F.; 1 its O2/hr.; 75 g. fluid] Cone. Induction Total Volume Run No. Name Additives (wt. perperiod time 038 abfluid cent) (min) (min) sorbed 5 119 3, 000 117 146 2, 500 205 247 2,500 5-ethyl-10, 10 (111] 5 47 2, 500

phenazasiline. Phenothiazine 0 5 304 do. 5-ethyl-l0,10-d1phenyl- 319 388 2,500

phenazasiline.

An ester from pentaerythritol and a mixture of aliphatic monocarboxylic acids with an average chain length of seven carbons.

The lengths of the induction periods serves as a significant measure of the relative effectiveness of the inhibitors. As shown in Table I, the 5-ethyl-l0,10 -diphenylphenazasiline-phenothiazine synthetic ester-based lubri-.- cant composition prevents oxygen uptake by the fluid for more than twice as long as would be expected from the results obtained when using phenothiazine and 5-ethyl- 10,10 diphenylphenazasiline alone.

Other examples of formulations made in accordance A diethylhexyl sebacate oil having a. kinematic viscosity at 100" F. of 12.3 cs., a viscosity index of 154-, a pour pomt of below -80 F. and acid No. of 0.12.

2 A polymer derived from tetrabutyl titanate and 2-ethy1-1,3- hexanediol.

D.C.F. 20060,000 is a methyl silicone polymer havmg a viscosity of 60,000 cs. at 25 C. and is an anti-foaming agent.

group contains 1 to 4 carbon atoms, said ester-based fluid being an ester of an alkanol of 4 to 12 carbon atoms and an alkane carboxylic acid of 4 to 12 carbon atoms.

2. The lubricant of claim 1 containing about 0.1 to 2 percent of phenothiazine, and about 0.1 to 2 percent by weight of 5-ethyl-10,10 diphenylphenazasiline.

References (Iited in the file of this patent UNITED STATES PATENTS Fainman Aug. 23, 1960 Kock May 22, 1962 OTHER REFERENCES Cohen,'-et al.: Aliphatic Esters, I and E Chem., vol. 45, No. 8, August 1953, pp. 1766-1775.

Dintses et al.: Synthetic Lubricating Oils, published by Liaison Otiices, Technical Information Center, Wright Patterson AFB, Ohio, F-TS-9719/V, August 1959, pages 283-304.

Rodd: Chemistry of Carbon Compounds, Vol. No (1960), page 1519, QD, 251, R6.

Claims

1. A LUBRICANT COMPOSITION CONSISTING ESSENTIALLY OF AN ESTER-BASED FLUID OF LUBRICATING VISCOSITY AND MINOR AMOUNTS EFFECTIVE TO RETARD OXIDATION AT TEMPERATURES IN EXCESS OF 400*F., OF ABOUT .01 TO 5 PERCENT BY WEIGHT OF PHENOTHIAZINE AND ABOUT .01 TO 5 PERCENT BY WEIGHT OF 5-ALKYL-10.10 DIPHENYLPHENAZASILINE WHEREIN THE ALKYL GROUP CONTAINS 1 TO 4 CARBON ATOMS, SAID ESTER-BASED FLUID BEING AN ESTER OF AN ALKANOL OF 4 TO 12 CARBON ATOMS AND AN ALKANE CARBOXYLIC ACID OF 4 TO 12 CARBON ATOMS.