US3121691A - Lubricant composition - Google Patents

Description

United States Patent No Drawing. Filed May 24, 1960, Ser. No. 31,282 Claims. (Cl. 252-515) This invention relates to ester based lubricant compositions containing a novel combination of base oil-soluble additive agents.

Organic compounds such as lubricant oi'ls 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 to 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. N-phenyl-l-naphthylamine 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 under high temperatures such as in excess of 400 F. F-urther, the additives of the present invention have provcn far more effective than the conventional use of N-phenyl-l-naphthylamine alone in reducing oxidation in synthetic ester fluids.

The present invention provides an improved esterbased lubricant composition containing N-phenyl-1-naphthylarnine and a component selected from the group of dipyridylamine, aminoquinoline, aminopyridine and mixtures thereof in minor amounts effective to impart to the lubricant increased resistance to oxidation. The amounts added should be soluble in the base oil into which they are introduced and these amounts will vary with the particular base oil utilized.

The preferred aminoqu-inolines which are used in the present invention are 3-aminoquinoline and B-aminoquinoline and their ring-substituted derivative e.g. allcyl-substituted. Among the useful aminopyridines are Z-arninopyridine and the ring-substituted, e.g., alkyl-substituted aminopyridines. The dipyridylamine additive useful in the present invention can be ringsubstituted, as for example, with alkyl groups, the preferred dipyridylarnine being 2,2'-dipyr-idylamine. Each of the aminoquinoline, aminopyridine and dipyridylamine or their mixture may be added in amounts from about .01 to 5 percent by weight of the final composition with a preferred amount of from about 0.1 to 2 percent by weight of the final composition. These additives are nor mally added to the ester-based lubricant along with the N-phenyl-l-naphthylamine. The N-phenyl-l-naphthyl amine is usually present in amounts from about .01 to 5 percent by weight of the final composition with a preferred amount being from about 0.1 to 2 percent and the N-phenyl-l-naphthylamine may be substituted as with alkyl groups, for instance, in the napthyl or phenyl ring. For best results the relative concentrations of the additives will vary with the particular ester lubricant employed and will also be dependent on the characteristics of the final lubricant composition desired. Normally, it is preferred that the dipyridylamine, aminoquinoline or aminopyridine to N-phenyl-l-naphthylamine weight ratio be about 0.5 to 2:1, advantageously about 0.75 to 15:1. Increasing the amounts of dipyridylamine, aminoquinoline or aminopyridine will generally be beneficial.

The lubricant composition or" this invention includes as the major compound 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, polyesters, or cliesters. These esters are made from monoand poly-hydroxy aliphatic alcohols and aliphatic car boxyiic acids, frequently of about 4 to 12 carbon atoms; aliphatic including cycloaliphat'ic. The reaction product of a monohydroxy alcohol and a mono carboxylic acid is usually considered to be a simple ester. A dicster 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 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 of the type XY-ZYX 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 polyesteriflaction reaction is usually continued until the product has a kinematic viscosity from about 15 to 200 centistokes 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 eng ines 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 included in 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,

- preferred.

. lmtanediol.

. 2-ethyl hexanediol.

extreme pressure or load carrying agents, corrosion inhibitors, etc., can be added.

Typical synthetic lubricants may be formulated essentially from a major amount (about 60-85%) of a complex ester and a minor amount (about 15-40%) of a diester, by stirring together a quantity of diester and complen 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 dies-tor oil. The polyester will generally not comprise more than about 50 weight percent of the blend, preferably about 20 to 35 weight percent. Usually the amount or": the polyester employed in any blend would be at least about 5 percent, and the majority of the lubricant is a di-.

ester. Other polymers, such as acryloids may be added .as thickeners to the esters, generally the simple esters such include butyl, hexyl, methyl, isoaoctyl, and dodecyl alcohols, C oxo alcohols and ootadecyl 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 monoiso-propyl 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 neo-structured; and esters of such alcohols are often In particular, the neo-C 'alooliol-2,2,4-trimethylpentanol-1-gives lubricating diesters or complex esters suitable for blending with diesters to produce lubricants which meet stringent viscosity requirements. Isooctanol and iso-decanol are alcohol mixtures made by the oxo process from C -C copolymer heptanes' The out which makes up iso-octanol usually contains about 17% 3,4-dimethy1henanol; 29% 3,5-dimethylhexanol; 23% 4,5-

dimethylhexanol; 1.4% 5,5-dimethylhexanol; 16% of a mixture of 3-methylheptanol and S-ethylheptanol; 2.3%

materials. 7 7

Generally, the glycols contain from about 4 to 12 car- 4-ethylhexanol; 4.3% a-alkyl alkanols and 5% other a bon 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- heptaaiediol, 2-methyl-1,3-pentanediol, 2-butyl-l,3-butane- .diol, 2,4-dipheny1-1,3-butanedio1, and 2,4-dimesityl-1,3-

In'addition to these glycols, ether glycols may be used, for instance, where the alkylene radical contains 2 to 4 carbon atoms such as diethylene glycol, dipropylene glycol and ether glycols up to 1000 to 2000 mo lecular weight. The most popular glycols for the manuiiactune oi ester lubricants appear to be polypropylene glycols having a molecular weight of about 100-300and neopentyl glycol have been shown to impart heat stability to the final blends. Minor amounts of other glycols or othermaterials can be present as long as the desired properties of the product are not unduly deleteriously afiected.

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 The 2,2-dimethyl glycols', such. as

12 carbon atoms, preferably about Slto 8 carbon atoms; for instance pentaer'vthritol, .trimethylolpropane and the like. Particularly suitable ester base oils are formed when these alcohols are reacted with monocarboxyli-c 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 substantially;completely esteri-iy the acids.

mixtures of these acids. adipic, suberic, azel-aic, and sebaoic acids and isosebacic acid which is a'mixture of a-ethyl suoeric acid, a,a'-die'thyl; adipic acid and sebacic acid. Thiscomposite of acids is attractive from the viewpoint of economy and availability; since it is made from petroleum hydrocarbons rather than 3 t the natural oils and fats which are used in the manufacture of many other dicarboxylic acids, which natural oils and 1 fats'are frequently in short supply. The preferred di-basic acids are sebacic and azelaic or mixtures thereof. Minor amounts of adipic used with a major amount ofsebacio may also be used with advantage;

Marious useful ester base oils are disclosed in United States Patents -Nos. 2,499,983, 2,499,984, 2,575,195, 2,575,196, 2,703,811, 2,705,724 and 2,723,286. Gener ally, 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 maybe substituted with other elements such as halogens, e.g. chlorine andflu'ori-ne. Some representative, components of ester lubricants-are ethylpalmit-ate, ethyl stearate, di-(Z-ethylhexyl) sebaca-te, ethylene glycol dilaunate, di-(2-ethylhexyl) phthalate, d.i(l,3-methyl butyl) adipa-te, di-(Z-ethyl butyl) adipate,di-(1-ethyl propyl) adipate, diethyl oxylalte, glycerol tri-n-Ootoate, di-cycloe hexyl adipatadi-(undecyl) sebacate, tetraethylene .glyool- J dis(2-ethylene hexoate), dicellosolve phthalate, bu-tyl k phthallylbutyl g -lycolate, di-n-hexyl fumarate polymer, dibenzyl sebaca'te, and diethylene glycol bis(2-n-bi1toxy ethyl'carbonatey" 2-ethylhexyl-adipate-neopentyl glycyl-l adipate-Z-ethylhexyl, is a representative complex ester. Generally, these synthetic ester lubricants have a viscosity ranging from light to heavy oils, e.g about 50 SUS at 1 l: to 250 SUS at 210 R, and preferably 30 to .1 50'SUS at2l0F. f

The esters are manufactured, in general, by meters-f action of the alcoholic and acidic constituents, although 1 simple esters may be converted to longer chain com- The constituents, iiithe] proportions suitable forgiving the desired ester, are'reacted preferably in the presence of a catalyst andsolvent or water entrainingagent to insure maintenance offtheliquid state during the reaction Aromatic hydrocarbons such as xylene or toluene. have proven satisfactory as 1 The choice of solventinfiuences the choice of temperature at which the esterification is conducted; for instance, when-toluene is used, a temperature of C.. is recommended; with xylene, temperatures upto about ponents by transesterification.

solvents.

C. may be used. To provide a better reaction rate boron. trifluoride, and silicon tetrafluorid-e, Titanium esters also make valuable esterification and transe'sterification 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 165 to 200 C. while refluxing water. The temperatures of the reaction must be sufiicient to remove the Water from the este-rification 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 175 C. The pressure is conveniently about atmospheric. Although reduced pressure or superatmospheric pressure could be utilized, there is usually no necessity to use reduced pressures, 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 210 F., preferably about 40 to 130 centistokes. When this point has been reached, the polymerization can be stopped, for instance, by adding a capping alcohol to the reaction mixture, and continuing to 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 paratoluenesulfonic 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 with weight percent of propylene oxide. It is also conventional to subject the ester to filtration to remove insoluble materials. After this the product may be subjected to a reduced pressure distillation or stripping at 100 to 200 C. to remove volatile materials, such as water, the solvent, and light ends.

Samples of ester fluids Without N-phenyl-l-naphthylamine and dipyridylamine, aminoquinoline or aminopyridine and samples made according to the present invention in various ester-based fluids Were subjected to the oxygen absorption tests. The tests were conducted at 450 F. by passing a stream of oxygen at the rate or one cubic foot per hour through 75 grams of the ester fluid containing the inhibitors and comparing the amount of oxygen absorbed vs. time. The induction period is signalled by a marked increase in the rate of oxygen ab- EXAMPLE I Parts by welght Plexol-20l 1 98 .0 Titanium polymer 2 1.0 N-phenyl- 1 -naphthylamine 0.5 2,2-dipyridylamine 0.5

D.C.F. 200--60,000 0.001

1 A diethylhexyl sebacate oil having a kinematic viscosity at 100 F. of 12.3 cs., a viscosity index of 154, a pour point of below SO F. and acid N0. of 0.12.

2 A polymer derived from tctrabutyl titanate and 2-ethyl-1,3 hexanediol.

11C1 0 ZOO-60,000 is a a viscosity of 60,000 cs. at agent.

methyl silicone polymer having 25 C. and is an anti-foaming EXAMPLE II Parts y Weight Plexol-ZSS 1 99.25 Glycol titanate polymer 2 0.25 N-phenyl-1-naphthylamine 0.5 2,2-dipyridylamine 1.0 Sebacic acid .0075 D.C.F. ZOO-60,000 .001

A mixture of diisooetyl adi pate, di-trideeyl sebacate, and Acrylo1d-966 (a copolymer of alkyl methacrylates and N-vinyl pyrrolidone). g1 cPflymer derived from titanium tetra-alkyl esters and EXAMPLE In Paris y Weight Diisooetyl azelate 26.0 Complex ester 1 74.0 Free azelaic acid 0.01 N -phenyll-naphthyl amine 0.5 2,2-dipyr-idylamine 1.0 D.C.F. 200-60,000 0.001

1 Derived from the reaction of one mole of neopentyl glycol, 2 moles of azelaic acid and two moles of isooctyl alcohol.

.In the compositions of Examples I, II and III, the 2,2'- dipyridylamine can be replaced with similar parts by Weight of Z-aminopyridine or B-aminoquinoline and obtain essentially similar results. Also, in Table I, 2,2- dipyridylamine and Z-aminopyridine can be replaced with 1.0 parts by weight of 3-aminoquinoline and obtain essorption. The results of these tests are shown in Table I. sentlally similar results.

TABLE I Results of Oxygen Absorption Tests [Test conditions: 450 F.; 1 it 02/1112; g. fluid] Cone. Induction Run No. Base Ester Additives (Wt. Period (min) None 5 N -Phenyl-1-naphthylarnine. 1. 0 97 d0 1. 0 305 2,2-Dipyridylamine 1. 0 d0 1.0 10 N-Pheny1-1-naphthlyamine 1. O 130 do 1. 0 307 2,2-Dipyridylamine 1. 0 N-P henyl-l-nap hthylamine 1. 0 82 o 1.0 299 2,2-Dipyridylamine.. 1. 0 400 Oil A N-Phenyl-l-napthyla 1. 0 276 2-Aminopyridine 1. 0 306 Trimethylolpropane do 1. 5 l3 tripelargonate. 46 Neo-oetylsebacate do 0.3 10

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

400; K.V. 210 F., 4.95 05.; K.V. F., 26.37 CS.

Typical inspection data: acid No., 0.01; sap.

and n-heptanoic acids.

3 Test stopped. Induction period not yet ended.

4 An ester from trimethylolpropane and n-heptanoie acid. Typical inspection data; acid No., 003; sap. No., 350; K.V. 210 F., 3.46 cs.;

K.V. 100 F., 14.82 cs.

It is claimed: a

major amount of synthetic ester. of lubricating viscosity and minor amounts effective to retard oxidation, of N- phenyl-l-naphthylainine and a material selected from the group consisting of dipyridylarnine, aminoquinoline and aminopyridine, said ester-based fluid being of an alkanol of 4 to 12 carbon atoms, said minor amounts being about 0.01 to 5 percent'by weight, and an alkane carboxylic acid of 4 to 12 carbon atoms. 1

2. The composition of claim 1 which contains 2,'2-dipyridylamine.

3. The composition of claim 1 which contains Z-aminopyridine.

quinoline.

naphthylamine.

References Citc din' the file of this pat ent v UNITED STAT ES PATENTS 7 OTHER REFERENCES I. and Chem., volume 39, No.4, April 1947, 'pp. V r 491-493 pertinent. t i 4. The composition of claim 1 wh1ch contams 3-amino- 15 V Cohen et aL: I. and E. Chem., voiume 45, No.

August 1953, page 1767 pertinent.

Mc-Neil "Nov. 22, 1960 I UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, l21;69l Q I February 18, 1964 Daniel B. Ei ckemeyer It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below. Y

Column 7, line 3, after "ester" insert fluid lines 8 and 9, strike outr", said minor amounts being about 0.01 to 5 percent by weight,"; line 10,- after "atoms" insert said minor amounts being about 0.01 to 5 percent by weight Signed and sealed ibis-23rd day of March 1965.

(SEAL) fittest:

ERNEST W. SWIDER V EDWARD J. BRENNER Aifilsting Officer g 1 Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 121;691 February 18, 1964 Daniel B. Eiclnemeyerhat error appears in the above numbered pat- It is hereby certified t that the said Letters Patentshould read as ent requiring correction and corrected below Column 7, lines 8 and 9, strike 'out' 0.01 to 5 percent by weight,"; said minor amounts being about 0.

line 3, after "ester' insert fluid said minor amounts being about line 10,- after "atoms" insert 01 to 5 percent by weight Signed and sealed .this.23rd day of March 1965.

EAL)

xst:

EDWARD J. BRENNER TEST W. SWIDER Commissioner of Patents ling Officer

Claims (1)

1. A LUBRICANT COMPOSITION CONSISTING ESSENTIALLY OF A MAJOR AMOUNT OF SYNTHETIC ESTER OF LUBRICATING VISCOSITY AND MINOR AMOUNTS EFFECTIVE TO RETARD OXIDATION, OF NPHENYL-1-NAPHTHYLAMINE AND A MATERIAL SELECTED FROM THE GROUP CONSISTING OF DIPYRIDYLAMINE, AMINOQUINOLINE AND AMINOPYRIDINE, SAID ESTER-BASED FLUID BEING OF AN ALKANOL OF 4 TO 12 CARBON ATOMS, SAID MINOR AMOUNTS BEING ABOUT 0.01 TO 5 PERCENT BY WEIGHT, AND AN ALKANE CARBOXYLIC ACID OF 4 TO 12 CARBON ATOMS.