US3546116A

US3546116A - Lubricant composition

Info

Publication number: US3546116A
Application number: US620280A
Authority: US
Inventors: Quentin E Thompson
Original assignee: Monsanto Co
Current assignee: Monsanto Co
Priority date: 1967-03-03
Filing date: 1967-03-03
Publication date: 1970-12-08
Anticipated expiration: 1987-12-08
Also published as: GB1205274A; DE1719571C3; DE1719571A1; BE711539A; ES351114A1; DE1719571B2; NL6802917A; FR1566461A; CH522028A

Description

United States Patent 3,546,116 LUBRICANT COMPOSITION Quentin E. Thompson, Belleville, Ill., assignor to Monsanto Company, St. Louis, Mo., a corporation of Delaware No Drawing. Filed Mar. 3, 1967, Ser. No. 620,280 Int. Cl. Cm 1/20 US. Cl. 25242.7 9 Claims ABSTRACT OF THE DISCLOSURE Compositions of the class which exhibit improved oxidation resistance by the incorporation of certain alkali metal compounds into a class of base stocks, representative of which are monoesters, diesters, triesters, polyesters, complex esters and mixtures thereof. The composition have many uses, among which are jet engine lubricants and hydraulic fluids.

This invention relates to functional fluid compositions which exhibit improved oxidative stability together with improved resistance to the corrosion of metal surfaces and more particularly to functional fluid compositions comprising certain functional fluids and an additive amount of an alkali metal compound.

Many different types of materials have been utilized as functional fluids and functional fluids are used in many different types of applications. Such fluids have been used as electronic coolants, atomic reactor coolants, diffusion pump fluids, synthetic lubricants, damping fluids, bases for greases, force transmission fluids (hydraulic fluids), heat transfer fluids, die casting release agents in metal extrusion processes and as filter mediums for air conditioning systems. Because of the wide variety of ap plications and the varied conditions under which func tional fluids are utilized, the properties desired in a good functional fluid necessarily vary with the particular application in which it is to be utilized with each individual application requiring a functional fluid having a specific class of properties.

Of the foregoing the use of functional fluids as lubricants, particularly jet engine lubricants, has posed what is probably the most difficult area of application. As the operating temperatures for lubricants have increased it has become exceedingly diflicult to find lubricants which properly function at engine temperatures for any satisfactory length of time. Thus, the requirements of a jet engine lubricant are as follows: The fluid should possess high and low temperature stability, foam resistance, good storage stability and be noncorrosive and nondamaging to metal mechanical members which are in contact with the fluid. Such fluids should, in addition, possess adequate temperature-viscosity properties and satisfactory lubricity, that is, the lubricants must not become too thin at the very high temperatures to which they are subjected nor must they become too thick at lower temperatures and must at the same time be able to provide lubricity over such range of temperatures. In addition, such lubricants should not form deposits which interfere with the proper operation of a jet engine.

As the speed and altitude of operation of jet engine containing vehicles increases, lubrication problems also increase because of increased operating temperatures and higher bearing pressures resulting from the increased thrust needed to obtain high speeds and altitudes. As the Service conditions encountered become increasingly severe the useful life of the functional fluid is shortened, primarily due to their deficiency in oxidative stability above 450 F. In general, as the operating requirements "ice of a jet engine are increased, engine temperatures increase and oil tempeartures in the range of 500 F. and higher are encountered.

The useful life of any lubricant can be adjudged on the basis of many criteria such as the extent of viscosity increase, the extent of deposits and the extent of corrosion to metal surfaces in contact with the lubricant. Those skilled in the art have found many ways to improve lubricants and to thus retard or prevent the effects which shorten the useful life of a lubricant. Thus, it is a general practice to add small amounts of other materials,, or additives, to lubricants in order to affect one or more of the properties of the base lubricant. It is difficult, however, especially as operating temperatures are increased, to find additives which will still perform the function for which they are added and yet not inject other problems such as increasing corrosion and engine deposits.

One of the major problems that occurs when a fluid oxidizes is the formation of oxidation products which can form sludge and deposits and in addition chemically attack both the fluid and mechanical members in contact with the fluid. In addition to the inhibition and control of oxidation of a fluid, such as by the incorporation of an antioxidant, the antioxidant itself must perform its function without injecting other problems, such as increasing corrosion of metal surfaces. As is readily apparent from the aforedescribed uses of a functional fluid, a fluid, depending upon the application, contacts various metals as for example, lead, aluminum, copper, bronze, steel and many alloys, which alloys utilize many types of metals in the allow composition. Corrosion of mechanical members such as bearing cages having lead flashings adversely affects (1) the mechanical members of a system in contact with the fluid, (2) the functional fluid itself and (3) the lubrication function of the fluid. The main problem resulting from corrosion of mechanical members, especially lead corrosion, is the effect of the corrosion products on the functional fluid and the lubrication function of the fluid. The corrosion products can form deposits on the mechanical members in contact with the fluid as well as being solubilized in the functional fluid. Certain corrosion products in addition to forming deposits can promote oxidation by catalyzing the oxidation of a functional fluid, thereby promoting increased sludge and deposit formation.

Thus, deposits can in general be formed from the oxidation of the base stock as well as deposits formed by the corrosion of mechanical members in contact with the fluid. The corrosion products can be formed, for example, by the corrosion of mechanical members by the oxidized fluid or by additives which are incorporated into a given fluid. The formation of deposits contaminates the fluid and requires premature draining of the fluid from the system as well as filter clogging and excessive filter replacement. In addition, deposits can adversely affect the proper lubrication of bearings such as by restricting and in some cases completely restricting the ability of a fluid to reach critical mechanical parts so as to perform their lubrication function. In addition, deposits can act as insulating materials when such deposits and other insoluble materials form on mechanical members. When this insulating effect occurs, the fluid does not accept heat as readily from mechanical parts at temperatures higher than the fluid and as a consequence metal fatigue and pitting of mechanical members can occur.

As is seen from the foregoing characteristics of a jet engine, a functional fluid can attain temperatures of up to 500 F. and higher which can result in oxidative and thermal degradation of a lubricant. The stabilization of lubricants at these high operating temperatures through the use of additives presents an extremely complex and difficult problem, especially since the incorporation of an antioxidant can inject other problems such as increased corrosion and engine deposits. Thus, the fact that one problem is solved such as oxidative stability of a functional fluid does not justify the introduction of an additional problem such as lead corrosion. As has been discussed above, deposits formed from corrosion of mechanical members can be generated by the oxidation of the base stock as well as additives incorporated into a base stock. It is, therefore, of particular importance that an antioxidant inhibit and control oxidation of a base stock as Well as not presenting any adverse problems.

It is, therefore, an object of this invention to provide functional fluid compositions which have improved oxidative stability by the incorporation of an antioxidant whereby said functional fluid exhibits improved oxidative stability together with improved resistance of the functional fluid composition towards the corrosion of lead surfaces in contact with functional fluids.

It has now been found that the oxidative stability and thus the useful life of functional fluids can be greatly extended, without injecting other problems, even under the severe conditions encountered in jet engines and other devices by the addition to functional fluids of an alkali metal compound selected from the group consisting of (A) (l) A compound represented by the structure where X is selected from the group consisting of carbonyl and sulfonyl; R is selected from the group consisting of R2 0 -c'1i'J0M I". and

-c=coo R2 Ra provided that when X is sulfonyl R is R is selected from the group consisting of a hydrocarbon radical and a heterocyclic ring having from 3 to 10 atoms optionally interrupted 'by from 1 to 4 hetero atoms selected from the group consisting of oxygen, nitrogen and sulfur; Y is selected from the group consisting of oxygen, sulfur and a is a whole number having a value of from 0 to 1, provided that when R is a has a value of 0; R and R are each selected from the group consisting of hydrogen and a hydrocarbon radical and when R is (|1=CI3OM R2 Ra R and R together with the carbon atoms to which they are attached can form a nonbenzenoid carbocyclic ring having from 4 to 8 carbon atoms; R; is selected from the group consisting of hydrogen and a member of the group represented by R and when a has a value of l and Y is R, and R together with the nitrogen atom to which they are attached can form a heterocyclic ring having from 3 to 10 atoms optionally interrupted by from 1 to 4 hetero atoms selected from the group consisting of oxygen, nitrogen and sulfur and M is an alkali metal; and

(2) mixtures thereof.

(B) (l) A compound represented by the structure RfiAI-R5 wherein Ar is an aromatic nucleus selected from the group consisting of benzene, benzoquinone and naphthalene; R

is selected from the group consisting of hydroxyl, 0M and II OORs, wherein M is an alkali metal; R is Rg(Yl)c (o)d and when R occupies a position ortho to R or when Ar is napthalene and R and R occupy positions l,8-, R and R together with the aromatic nucleus to which they are attached can form a cyclic carbonate; 0 and d are each whole numbers having a value of 0 to 1, provided that the sum of c1+d is from O to 1; R and R are each selected from the group consisting of a hydrocarbon radical and a heterocyclic ring having from 3 to 10 atoms optionally interrupted by from 1 to 4 hetero atoms selected from the group consisting of oxygen, nitrogen and sulfur; Y is selected from the group consisting of oxygen, sulfur and l io .N

R is selected from the group consisting of hydrogen and a member of the group represented by R and R and R together with the nitrogen atom to which they are attached can form a heterocyclic ring having from 3 to 10 atoms optionally interrupted by from 1 to 4 hetero atoms selected from the group consisting of oxygen, nitrogen and sulfur; d is a whole number having a value of from 0 to 6; R is selected from the group consisting of a hydrocarbon oxy radical, a member of the group represented by R a member of the group represented by R and a member of the group represented by R and when 11 has a value greater than 1 any two groups represented by R which are attached to adjacent carbon atoms can together with the carbon atoms to which they are attached form a cyclic ring selected from the group consisting of a carbocyclic ring and a heterocyclic ring, said cyclic ring having from 3 to 10 atoms optionally interrupted by from 0 to 4 hetero atoms selected from the group consisting of oxygen, nitrogen and sulfur; provided that when Ar is selected from benzene or naphthalene and R and R are attached to the same carbocyclic ring, R is positioned ortho to R when d has a value of 0 and R is positioned ortho or meta to R when d has a value of 1, and provided that when Ar is naphthalene wherein R and R are attached to different carbocyclic rings R and R occupy positions selected from 1,5- and 1,8- and further provided that there is present at least one 0M group wherein M is an alkali metal; and (2) mixtures thereof.

(C) (1) A compound represented by the structure wherein M is an alkali metal, R and R are each selected from the group consisting of hydrogen and a hydrocarbon radical; and (2) mixtures thereof; and

(D) Mixtures of (A), (B) and (C).

The functional fluids to which the alkali metal compounds represented by (A), (B), (C) and (D) are added to provide compositions of this invention, hereinafter referred to as *base stocks, include by way of example, an ester base stock, ester base stock defined herein to include a single ester base stock as well as a mixture of ester base stocks, typical examples of which are monoester base stocks, diester base stocks, triester base stocks, polyester base stock, complex ester base stocks and mixtures thereof. It is contemplated that mixtures of the aforedescribed base stocks can contain major amounts of one base stock even as high as 99% with the remainder being one or more base stocks.

Whereas the incorporation of any foreign element into a base stock can alter properties of a functional fluid, the concentration of the alkali metal compounds represented by (A), (B), (C) and (D) in the base stock is adjusted in terms of the particular system and the base stock which is utilized in this system to provide functional fluid compositions of this invention which contain additive amounts of an alkali metal compound represented by (A), (B), (C) and (D) sufiicient to improve the oxidative stability of a base stock while not adversely affecting critical functional fluid properties. It has generally been found that the preferred additive concentration of an alkali metal compound represented by (A), (B), (C) and (.D) for the base stocks described above is generally from about 0.001 weight percent to about 10 weight percent, preferably from about 0.01 weight percent to about 2.5 weight percent.

Therefore, included within the present invention are compositions comprising a base stock and an oxidation improving amount of an alkali metal compound represented by (A), (B), (C) and (D), that is, an alkali metal compound represented by (A), (B), (C) and (D) is added to the compositions at a concentration sufficient to improve the oxidative stability. The functional fluid compositions of this invention can be compounded in any manner known to those skilled in the art, as for example, by adding an alkali metal compound represented by (A), (B), (C) and (D) to the base stock with stirring until a composition is obtained. In addition, the metal compounds can be prepared in situ, that is, in the base stocks as aforedescribed. It is also contemplated within the scope of this invention that additive concentrates can be prepared such as additive compositions containing from about 10% to about 60% of the alkali metal compounds represented by (A), (B), (C) and (D) and the base stocks as aforedescribed.

Typical alkali metals are lithium, sodium, potassium, rubidium and cesium. Although all alkali metals are contemplated within the scope of this invention, the preferred alkali metal is potassium.

The various groups represented by a hydrocarbon radical, a hydrocarbon oxy radical, a cyclic ring, a carbocyclic ring and a heterocyclic ring are defined broadly to include groups which are unsubstituted as well as substituted. In the following discussion the term hydrocarbon radical includes not only a group represented by a hydrocarbon radical but in addition includes the hydrocarbon portion of the hydrocarbon oxy radical. In addition, two or more substituents can together form a carbocyclic or heterocyclic ring. Thus, for example, when a heterocyclic ring or carbocyclic ring is the representative group, substituents on a carbocyclic ring or heterocyclic ring can together with the heterocyclic or carbocyclic ring form a ring. Thus, two or more substituents can, for example, form an aromatic ring, an example of which would be benzimidazolyl, which group would be included in the generic description, heterocyclic ring. In addition, the term heterocyclic ring is herein defined to include a heterocyclic ring which is present in a compound such as a compound represented by (A)(l) wherein R and R together with a nitrogen atom to which they are attached form a heterocyclic ring in which the nitrogen atom to which R and R are attached is the sole hetero atom.

The term hydrocarbon radical is herein defined to include hydrocarbons which contain only carbon and hydrogen and also hydrocarbons which contain other elements in addition to carbon and hydrogen. The term hydrocarbon radical, Whichcontains carbon and hydrogen as well as carbon, hydrogen and other elements, includes hydrocarbon radicals which are completely saturated as well as hydrocarbons which have unsaturation. Thus, the term hydrocarbon radical, in addition to hydrocarbons containing only carbon and hydrogen, includes hydrocarbon radicals containing one or more elements (such as oxygen, nitrogen and sulfur) other thna carbon and hydrogen, which elements can be substituted upon a hydrocarbon radical or can link two or more hydrocarbon radicals. It is also contemplated that a hydrocarbon radical can contain both substitution and linkage by one or more elements.

Thus, substituents can be present such as aryloxy, aryl, alkyl, alkoxy, polyaryloxy, arylmercapto, acyl, aroyl, dialkylamino, monoand polyhydroxy aryl, monoand polyacyl aryl, hydroxyand acyl-substituted aryl, cyano, 0x0 and carboalkoxy.

Whereas all of the aforedescribed groups, that is, a hydrocarbon radical, a hydrocarbon oxy radical, a cyclic ring, a carbocyclic ring and a heterocyclic ring, are contemplated within the scope of this invention, such groups should be non-interfering with respect to the functioning of the compounds represented by (A), (B), (C) and (D). Thus, a group should be non-interfering to the extent that it does not completely nullify the antioxidant activity of the compounds represented by (A), (B), (C) and (D) when incorporated into a base stock. The aforedescribed groups can be adjusted with respect to the number of carbon atoms present and the number of elements present in a group other than carbon and hydrogen such that a compound represented by (A), (B), (C) and (D) would be soluble in a particular base stock to which the subject compound is incorporated. Thus, depending on the particular base stock, a compound represented by (A), (B), (C) and (D) can be modified such as by adjusting the chain length of the group or adjusting the branching present in a group in order that the particular compound will be soluble in a given base stock. As is apparent from the description of the aforedescribed base stocks, the solubilizing properties of the base stocks can vary and thus the solubility characteristics of the compounds represented by (A), (B), (C) and (D) can be adjusted. The various aforedescribed groups, that is, the hydrocarbon radical, the hydrocarbon oxy radical, the cyclic ring, the carbocyclic and heterocyclic rings, are non-critical features of this invention. Thus, these groups can vary over a wide range with respect to the number of carbon atoms present and the number of elements other than carbon and hydrogen which are attached to the various groups. Thus, in general, it is preferred that the various groups contain as an upper limit with respect to the number of carbon atoms present per equivalent weight of M, M or M of about 28 carbon atoms per equivalent of M, M or M and more preferably up to about 10 carbon atoms per equivalent of M, M, or M In addition, the aforedescribed groups can be defined by the number of elements other than carbon and hydrogen which are present per equivalent of metal represented by M, M or M wherein M, M, or M have their aforedescribed significance. Thus, for the various groups represented by a' hydrocarbon radical, a hydrocarbon oxy radical, a cyclic ring, a carbocyclic and heterocyclic ring, the upper limit of the number of elements other than carbon and hydrogen such as oxygen, nitrogen and sulfur Which can be present per equivalent of M, M or M has a preferred upper limit of about 6 elements per equivalent of M, M, or M and more preferably is an upper limit of about 4 elements per equivalent of a metal represented by M, M, or M Typical examples of a hydrocarbon radical are alkyl, such as methyl, ethyl, propyl, isopropyl, butyl, tertbutyl, amyl, hexyl, heptyl, octyl, nonyl, octadecyl; alkenyl, such as propenyl, butenyl, heptenyl, dodecenyl and the like; cycloaliphatic, such as cyclopropyl, cyclobutyl, cyclohexyl, monoand polymethyl cyclohexyl, monoand polyisopropyl cyclohexyl, naphthenyl, cyclopentyl, noncyclohexenyl and the like; aryl, herein defined to include mono-, diand polynuclear hydrocarbons, such as phenyl, naphthyl and anthyryl, typical examples of aryl being phenyl, alkylphenyl, xenyl, tert-amylphenyl, naphthyl, tolyl, cresyl, halogenated phenyl, monoand polyhydroxy phenyl, dialkylamino phenyl, monoand polyacyl aryl, hydroxyand acyl-substituted aryl, cyanophenyl, alkylhydroxyphenyl, alkylchlorophenyl, algylcyanophenyl, butylcyano naphthyl, cyclohexylphenyl, phenoxyphenyl, tertbutylphenoxyphenyl, dialkylaminophenyl and the like; aralkyl, such as benzyl, methylbenzyl, phenylethyl and the like; oxyand/or oxo-containing aliphatic, cycloaliphatic and aromatic radicals, such as aroyl, typical examples of which are benzoyl, 3-methylbenzoyl, acyl such as acetyl, aryl-substituted acyl, alkoxy-substituted alkyl radicals, cycloalkoxy-substituted alkyl radical, alkenoxy-substituted alkyl radical, carboalkoxy such as carboethoxy, carboalkoxy-substituted aryl or alkyl radical, aroxy-substituted alkyl radical, alkoxy-substituted cyclohexyl, aroxy-substituted cyclohexyl, carboalkoxycycloalkyl radical and the like; and the aforedescribed groups further substituted with a heterocyclic group containing from 4 to 10 atoms optionally interrupted by from 1 to 4 hetero atoms, which can be nitrogen, sulfur or oxygen or combinations thereof, such as substituted and unsubstituted pyridyl and the like.

Typical examples of heterocyclic groups are fury], thienyl, piperidyl, pyrryl, thiazolyl, thiadiazolyl, pyrazinyl, pyridyl, pyrazolyl, imidazolyl, oxazolyl, pyrimidinyl or a benz derivative thereof such as benzisoxazolyl, benzimidazolyl, benzofuranyl, benzothiazolyl, benzotriazolyl, benzoxazolyl, benzothienyl, indazolyl or isoindazolyl.

Typical examples of compounds represented by (A) (1) wherein R is and a has a value of zero, are alkali metal salts of 2- benzoyl acetic acid,

2-(1-naphthoyl) acetic acid, 2-(2-naphthoyl) acetic acid, 2,2-dimethyl-2-benzoyl acetic acid, 2,2-dimethyl-2-(l-naphthoyl) acetic acid, 2,2-dimethyl-2-(Z-naphthoyl) acetic acid, 2-methyl-2-ethyl-2-benzoyl acetic acid, 2-(2-methyl-2-ethyl) acetic acid, 2,2-dimethyl-2-(2-methyl-2-ethyl) acetic acid, 2,2-dimethyl-2-(3-methylbenzoyl) acetic acid, 2,2-dimethyl-2-(8-hydroxyl-2-naphthoyl) acetic acid, fi-oxo-cyclohexane propionic acid, a,a-dimethyl-fi-oxo-cyclohexane propionic acid, a-methyl-u-ethyl-fi-oxo-(3-ethylcyclohexane) propionic acid, fi-ox-3-pyridine propionic acid, a,a-dimethyl-fl-oxo-3-pyridine propionic acid, u,u-dimethyl-B-oxo(2-methyl-3-pyridine) propionic acid, 2,2-dimethyl-3-oxo-4-methyl valeric acid, 2-methyl-2-ethyl-3-oxo-4-methyl valeric acid, 2,2-diethyl-3-oxo-4-methyl valeric acid, 2,2-dirnethyl-3-oxo-4-methyl hexanoic acid, 2-methyl-2-ethyl-3-oxo-4-methyl hexanoic acid, 2,2-diethyl-3-oxo-4-methyl hexanoic acid, 2-2-dimethyl-3-oxo-4-methyl octanoic acid, 2-methyl-2-ethyl-3-oxo-4-methyl octanoic acid and 2,2-diethyl-3-oxo-4-methyl octanoic acid.

Typical examples of compounds represented by (A) (1) wherein R is and a has a value of 1 are alkali metal salts of N,N- dimethyl malonamic acid,

N-methyl-N-butyl malonamic acid, N-methyl-N-propyl malonamic acid, N,N-dimethyl-2,2-dimethyl malonamic acid, N-methyl-N-butyl-2,2-dimethyl malonamic acid, methyl-N-propyl-2,2-dimethyl malonamic acid, N,N-dimethyl-2-methyl-2-ethyl malonamic acid, N-methyl-N-butyl-Z-methyl-2-ethyl malonamic acid, N-methyl-N-propyl-2-methyl-2-ethyl malonamic acid, N-phenyl-N-methyl malonanilic acid, N-phenyl-N-ethyl malonanilic acid, N-phenyl-N-butyl malonanilic acid, 'N-phenyl-N-methyl-Z,Z-dimethyl malonanilic acid, N-phenyl-N-ethyl-2,2-dimethyl malonanilic acid, N-phenyl-N-butyl-2,2-dimethyl malonanilic acid, N-phenyl-N-methyl-2-methyl-2-ethyl malonanilic acid, N-phenyl-N-ethyl-2-methyl-2-ethyl malonanilic acid, N-phenyl-N-butyl-2-methyl-2-ethyl malonanilic acid, 2-ethoxycarbonyl-2-dimethyl acetic acid, 2-ethoxycarbonyl-Z-methyl-Z-ethyl acetic acid, Z-tert-butoxycarbonyl-2,2-dimethyl acetic acid, 2-tert butoxycarbonyl-Z-methyl-2-ethyl acetic acid, 2-(2-pyridine oxycarbonyl)-2,2-dimethyl acetic acid, 2-(4-pyridine oxycarbonyl)-2,2-dimethyl acetic acid, 2-(cyclohexane oxycarbonyl)-2,2-dimethyl acetic acid, 2-(2-pyridine oxycarbonyl)-2-methyl-2-ethyl acetic acid, 2-(4-pyridine oxycarbonyl)-2-methyl-2-ethyl acetic acid, 2-(cyclohexane oxycarbonyl)-2-methyl-2-ethyl acetic acid, .2-(phenoxycarbonyl)-2,2-dimethyl acetic acid, 2-(phenoxyphenoxycarbonyl)-2,2-dimethyl acetic acid, 2-(phenoxycarbonyl-Z-methyl)-2-ethyl acetic acid, 2- (phenoxyphenoxycarbonyl -2-methyl-2-ethyl acetic acid, 2-(ethoxy sulfonyl)-2,2-dimethyl acetic acid, 2-(2-pyridine oxysulfonyl)-2,2-dimethyl acetic acid, 2-(ethoxy sulfonyl)-2-methyl-2-ethyl acetic acid and 2-(2-pyridine oxysulfonyl)-2-methyl-2-ethyl acetic acid.

Typical examples of compounds represented by (A)(l) wherein R is are alkali metal salts of 1,3-indane dione, 2,4-pentane dione,

3-methyl-2,4-pentane dione,

2,4-hexane dione,

3-methyl-2,4-hexane dione, 3-acetyl-2,4-pentane dione, 3-acetyl-2,4-hexane dione, 2-methyl-5,5-dimethyl-2,4-hexane dione, 1- (m-chlorophenyl) -2,4-hexane dione, 1,3-cyclohexane dione and 5-tert-butyl-1,3-hexane dione,

Typical examples of compounds represented by (B) 1) are alkali metal salts of 2-hydroxy-3-naphth0ylanilide,

o-acetyl phenol,

o-n-butyryl phenol,

2,4-diacetyl phenol,

resorcinol monoacetate,

resorcinol hexanoate,

catechol monoacetate,

catechol monohexanoate,

resorcinol monobutyrate,

catechol monobutyrate,

3,4-dimethyl catechol monoacetate, 3,4-dimethyl resorcinol monoacetate, 3-methyl-4-acetyl catechol monoacetate, 3-methyl-4-acetyl resorcinol monoacetate, 4-methyl-8-ethyl-1,3-naphthalene diol, 8-butyryl-l,3-napthalene diol, l-hydroxy-S-acetoxy naphthalene, 2-hydroxy-4-acetoxy acetophenone,

9 2-acetoxy-4-hydroxy acetophenone, 2,2-di-hydroxy-4,4'-diacetoxy benzophenone, 2'hydroxy-2',4,4'-triacetoxy benzophenone, Z-hydroxy-S-acetoxy-p-benzoquinone and 2-hydroxy acetophenone.

Typical examples of compounds represented by (C) (1) are alkali metal salts of 2-cyano-2-methyl acetic acid,

2-cyano-2,2-dimethyl acetic acid, 2-cyano-2,2-diethyl acetic acid, 2-cyano-2-ethyl-2-methyl acetic acid, 2-cyano-2-butyl-2-ethyl acetic acid, 2-cyano-2-hexyl-2-methyl acetic acid and 2-cyano-2,2-dihexyl acetic acid.

as polyethylene glycols. Complex esters are also formed by linking dibasic acid half esters through a glycol such as dipropylene glycol, a polyethylene glycol of 200 molecular Weight, and so forth. Permutation and combination of these methods of forming ester type lubricant fluids are valuable as well and also it is common practice to achieve desired properties in the ultimate base fluid by blending different ester base stocks. Simple esters providing suitable fluids can be exemplified, for example, by

bis(2-methylbuty1) sebacate, bis(l-methylcyclohexylmethyl) sebacate, bis(2,2,4-trimethylpentyl) sebacate, dipropylene glycol dipelargonate,

the diesters of acids such as sebacic, azelaic and adipic acid with complex (3 primary branched chain alcohols such as those produced by the x0 process,

polyethylene glycol 200 bis(2-ethylhexyl) sebacate,

diisoamyl adipate,

1,6-hexamethylene glycol di(Z-ethylhexanoate),

bis(dimethylamyl)azelate, di(2-ethylhexyl azelate,

di(Z-ethylhexyl) sebacate,

diisooctyl sebacate,

Z-ethylhexyl 3:5 :5 trimethylhexyl sebacate,

diisooctyl azelate,

di(3 5 :5 trimethylhexyl) sebacate,

di(1-methyl-4-ethyloctyl) sebacate,

diisodecyl azelate,

diisotridecyl azelate,

di(1-rnethyl-4-ethyloctyl) glutarate,

di(Z-ethylhexyl) adipate,

di(S-methylbutyl) azelate, di(3:5 :5 trimethylhexyl) azelate,

di(2-ethylhexy1) adipate,

di(C oxo) adipate,

bis(diethylene glycol monobutyl ether) adipate,

diisooctyl/isodecyl) adipate,

diisotridecyl adipate,

triethylene glycol di(Z-ethylhexanoate),

hexanediol 1,6-di(2-ethylhexanoate) and dipropylene glycol dipelargonate.

Ester fluids with particularly good high temperature oxidation resistance are provided by neopentyl polyol esters. The alcohols from which these esters are derived have the carbon structure of neopentane, with a central carbon atom surrounded by 4 substituent carbon atoms. Included in the neopentyl polyols are neopentyl glycol, trimenthylolethane, trimethylolpropane and pentaerythritol. Generally, the base fluids comprising neopentyl polyol esters are the esters with monocarboxylic acids. Such esters are generaly more oxidatively and thermally stable than the dibasic acid esters. The useful esters of the neopentyl polyols include, for example, the esters of trimethylol propane, neopentyl glycol and pentaerythritol with normal, branched chain and mixed acids having chain lengths varying from C to C Thus, an illustrative series of esters are trimethylolpropane tri-n-pelorgonate, trimethylolpropane, tricaprate, trimethylolpropane tricaprylate, the trimethylolpropane triester of mixed octanoates, pentaerythrityl tetrabutyrate, pentaerythrityl tetravalerate, pentaerythrityl tetracaproate, pentaerythrityl dibutyrate dicaproate, pentaerythrityl butyrate caproate divalerate, pentaerythrityl butyrate trivalerate, pentaerythrityl butyrate tricaproate, pentaerythrityl tributyrate caproate. Suitable dipentaerythrityl esters include dipentaerythrityl hexavalerate, dipentaerythrityl hexacaproate, dipentaerythrityl hexaheptoate, dipentaerythrityl hexacaprylate, dipentaerythrityl tributyrate tricaproate, dipentaerythrityl trivalerate trinonylate and dipentaerythrityl mixed hexaesters of C fatty acids.

Typical examples of complex esters are obtained by esterifying dicarboxylic acids with a mixture of monohydric alcohol and a glycol to give complex esters. Complex esters which can be prepared by esterifying a dicarboxylic acid (1 mole) with a glycol (2 moles) and a monocarboxylic acid (2 moles) or with 1 each of a glycol, a dicarboxylic acid and a monohydric alcohol or with 2 moles each of a monohydroxy monocarboxylic acid and a monohydric alcohol. Still other complex esters may be prepared by esterifying a glycol (1 mole) with a monohydroxy monocarboxylic acid (2 moles) and a monocarboxylic acid (2 moles).

Other complex esters which are suitable are prepared by polymerizing a dihydroxy compound With a dicarboxylic acid and reacting the terminal hydroxy and acid r radical with a mixture of a monocarboxylic acid and a monohydric alcohol. Specific examples of polymers which may be utilized as additives Within the scope of this invention are polymers prepared by the polymerization of adipic acid and 1,2-propane diol in the presence of minor amounts of short-chain monocarboxylic acids and a monohydric alcohol to give molecular weights of the polymers thereby produced of from about 700 to about 40,000 or higher.

The mono-, diand polyhydric alcohols, and the mono carboxylic acids employed in the preparation of the complex esters can also contain ether oxygen linkages.

Specific examples of suitable complex esters which are suitable base stocks are esters prepared from methylene glycol (1 mole), adipic acid (2 moles) and 2-ethylhexanol (2 moles); esters prepared from tetraethylene glycol (1 mole), sebacic acid (2 moles), and 2-ethylhexanol (2 moles); esters prepared from 2-ethyl-1:3 hexanediol (1 mole), sebacic acid (2 moles) and Z-ethylhexanol (2 moles); esters prepared from diethylene glycol (1 mole), adipic acid (2 moles) and n-butanol (2 moles); esters prepared from polyglycol 200 (1 mole), sebacic acid (2 moles) and ethylene glycol mono(2-ethylbutyl) ether (2 moles); esters prepared from sebacic acid (1 mole), tetraethylene glycol (2 moles) and caproic acid (2 moles); esters prepared from triethylene glycol (1 mole), adipic acid (1 mole), n-caproic acid (1 mole) and 2-ethylhexanol (1 mole); esters prepared from sebacic acid (1 mole), lactic acid (2 moles) and n butanol (2 moles); esters prepared from tetraethylene glycol (1 mole), lactic acid (2 moles) and butyric acid (2 moles); complex esters prepared from neopentyl glycol (2 moles), dicarboxylic acids (1 mole) and monocarboxylic acids (2 moles) and complex esters prepared from neopentyl glycol (1 mole) dicarboxylic acids (2 moles) and monohydric neoalcohols, e.g., 2,2,4-trimethylpentanol (2 moles).

In order to demonstrate the outstanding properties of the compositions of this invention, various metal salts were blended into base stocks and the resulting functional fluid compositions evaluated for oxidative stability and improved resistance to lead corrosion. One of the major bench scales for evaluating the high temperature performance characteristics of lubricants under a selected level of severity is the hearing test.

Briefly the apparatus used in this test is an Erdco high temperature bearing head mounted on an Erdco universal test stand. The bearing head is divided internally into two main sections. The front, or test section, contains the test oil system and an unshielded 100 ml. straight roller bearing. The temperature of the test bearing is controlled by supplying heat to the outer race of the bearing. The rear of support section of the bearing head provides for the external loading of the main shaft which transmits a radial load to the test bearing. The test and support sections of the bearing head are separated by air cell to prevent mixing of the test and support oils. The test oil temperature is maintained by a controlled heat sump.

In conducting the test a sample of the lubricant is subjected to a selected severity (temperature) level for a 100-hour endurance period. At l-hour intervals during the test, samples of the oil are taken so that changes in physical and chemical properties of the oil during the test can be determined. A visual inspection is made at the end of the test which assesses the type and extent of accumulated deposits in the test bearing compartment. A weighted numerical rating system is used to define the deposit condition at the end of the test. Additional data on the relative sludge forming tendencies are obtained by monitoring the weight of air inlet screen (100 mesh) and outlet screen (40 mesh) during the test. Screens are changed when their pressure drop reaches p.s.i.

Oil is supplied to the bearing during the test from the sump at a rate of 600 cc. per minute through a No. 60 drill size jet located so as to supply test oil to the bearing at approximately the 12 oclock position. Before the test proper is commenced, the bearing rig is started and the following conditions are allowed to stabilize.

reported in terms of cleanliness by the use of a demerit system which embodies the assignment of values of 0 to 20 based upon inspection of the bearing head and bearing. 0 designates a new or thoroughly clean condition, whereas 20 represents the worse condition possible. An example of the types of deposits which can be encountered are those ranging from what is normally termed a varnish through deposits which are only in the form of a sludge to degrees of actual carbon coating which can be a light, smooth coating to a heavy carbon deposit which is blistered or even flaky.

In addition to assigning a demerit rating to various points within the bearing head, an area demerit is also applied in determining an over-all deposit rating. An area demerit is defined as the area covered by the deposits divided by 10. In turn the area demerit is multiplied by the demerit value previously assigned from the inspection to provide a rating. Then in turn the rating obtained as described above is multiplied by a weight factor to yield a demerit rating. The weight factor takes into account the severity of the conditions which are encountered in various locations in the bearing head. For example, the weight factor for the end cover of the bearing head is one, whereas the weight factor for the bearing itself is 5. In all, 6 different locations are inspected and rated and the foregoing system applied to arrive at a demerit for each such location. In the case of the inspection in the determination of demerits for the bearing, the bearing is broken down into various categories, such as a roller case and outer and inner races, which are individually rated to arrive at a demerit rating. The demerit ratings of the 6 locations which are inspected are then added and divided by 6 to arrive at an over-all rating.

In the following examples in Table I the bearing temperature was 500 F. and the bulk oil temperature was 440 F. The base stock that was utilized in the following examples was a mixture of short-chain pentaerythritol esters and short-chain dipentaerythritol esters having an Oil in tem erature 400 F. Oil flow i 600 cc per minute average chain length of about 6 carbon atoms. The base Bearing speed 10 000 rpm stock was formulated with a trlaryl phosphate and 1% Radial load 5 lbs each of phenyl-a-naphthalene and dioctyl phenylamme. Air flow to beating head and cover 0.35 c.f.m.

TABLE I Deposit test result Concentratlon, Percent, meq/ deposit viscosity Example No. Metal compound 100 g. rating increase 1 None None 48 406 Potassium salt of 2,2,4-trlmethyl-3-oxo valerlc acld 0.443 24 190 Potassium salt of 2-hydroxy-3-naphthoylanlhde 0.156 22 87 The 100-hour endurance test is then commenced. The 100-hour test is conducted so that there is at least one thermal cycle" every 17 hours of operation. This thermal cycle consists of a shutdown at least long enough to allow the test oil bulk temperature to drop to 150 F., after which the temperature is raised back to that present at the beginning of the test. Bearing stabilization and warm-up time following a shutdown is considered part of the 100-hour test time.

After completing the test and shuting down the equipment, the conditions of the bearing and bearing head are One of the major bench scale methods used for evaluating the lead corrosivity of various lubricant formulations is Federal Test Method Standard No. 791, Method No. 5321.1. The base stock that was used was the same base stock as was utilized for preparing the compositions of Table I. In the above test method, 500 ml. of the test fluid is placed into a tube to which is inserted a lead test panel. The tube is inserted in a bath which is maintained at a temperature of 375. Air is bubbled through the sample liquid at approximately 2 cubic feet per hour. The weight loss or net weight gain of the test sample is measured after a period of 5 hours. The weight loss is measured in milligrams per square inch.

TABLE II Coneen- Weight loss lead,

tration, mg./in. Example meq./ No. Metal compound g. 1 hour 5 hours 4 Potassium salt of 2,2,4-trimethyl-3-oxo valeric acid 0 22 10 Potassium salt of 2-hydroxy-3-naphtlroylanilide- Potassium salt of o-hydroxy acetophenone 7 Potassium salt of N-C12.14 alkyl tetrapropenylsuccinamic acid 1 Over 100.

As is demonstrated by Table I, it is clearly evident that the incorporation of the metal compounds represented by (A), (B), (C) and (D) into a base stock provides a functional fluid composition which has a high degree of resistance towards oxidative degradation and therefore a greatly extended useful life. In regard to the extension of useful life, it has been found that the test procedure used above correlates quite well with the results obtained during full-scale aircraft gas turbine engine tests and under conditions of actual use. In particular, Table I clearly illustrates the reduction in deposits tendencies and the control oxidation by the incorporation of a metal compound represented by (A), (B), (C) and (D). This is of particular significance since the control of oxidation influences the useful life of a functional fluid composition. In addition, the tendencies of a functional fluid to form deposits adversely affects the lubricating qualities and in particular the ability of a functional fluid composition to perform its lubricant function. Thus, deposits can plug filters as well as critical orifices through which a fluid of necessity has to flow in order to lubricate critical areas in a jet engine.

Table II significantly demonstrates the reduction in corrosion tendencies of a functional fluid composition having incorporated therein an alkali metal compound represented by (A), (B), (C) and (D). In particular, Table II demonstrates the high degree of resistance towards oxidative degradation by the incorporation of a compound represented by (A), (B), (C) and (D) while not adversely affecting other critical fluid properties such as lead corrosion. Thus, for example, Example 7 shows that a potassium salt of a compound not having the requisite structure of those compounds represented by (A), (B), (C) and (D) injects other problems and in particular adversely affects the lead corrosion. The high degree of lead corrosion is well illustrated by the weight loss in lead after hours, which loss is 10 times over the compounds represented by (A), (B), (C) and (D). Thus, the oxidative stability of a functional fluid is increased without injecting other problems such as lead corrosion which itself can adversely affect the performance of a functional fluid composition.

As a result of the excellent stabilization of functional fluids which incorporate the metal compounds of this invention, lubrication of gas turbine engines is obtained over extended periods of time. Thus, this invention relates to a novel method of lubricating gas turbine engine which comprises maintaining on the bearings and other points of wear a lubricating amount of a composition of this invention.

In addition, utilizing the functional fluid compositions within the scope of this invention, improved hydraulic pressure devices can be prepared in accordance with this invention which comprise in combination a fluid chamber and an actuating fluid composition in said chamber, said fluid comprising a mixture of one or more of the base stocks hereinbefore described and a minor amount, suflicient to inhibit and control corrosion damage, of the additive composition of this invention. In such a system, the parts which are so lubricated include the frictional surfaces of the source of power, namely the pump, valves, operating pistons and cylinders, fluid motors, and in some cases, for machine tools, the Ways, tables and slides. The hydraulic system may be of either the constant-volume or the variable-volume type of system.

The pumps may be of various types, including centrifugal pumps, jet pumps, turbine vane, liquid piston gas compressors, piston-type pump, more particularly the variable-stroke piston pump, the variable-discharge or variable displacement piston pump, radial-piston pump, axial-piston pump, in which a pivoted cylinder block is adjusted at various angles with the piston assembly, for example, the Vickers Axial-Piston Pump, or in which the mechanism which drives the pistons is set at an angle adjustable with the cylinder block; gear-type pump, which may be spur, helical or herringbone gears, variations of internal gears, or a screw pump; or vane pumps. The valves may be stop valves, reversing valves, pilot valves, throttling valves, sequence valves, relief valves, servo valves, nonreturn valves, poppet valves or unloading valves. Fluid motors are usually constantor variable-discharge piston pumps caused to rotate by the pressure of the hydraulic fluid of the system with the power supplied by the pump power source. Such a hydraulic motor may be used in connection with a variable-discharge pump to form a variable-speed transmission. It is, therefore, especially important that the frictional parts of the fluid system which are lubricated by the functional fluid be protected from damage. Thus, damage brings about seizure of frictional parts, excessive wear and premature replacement of parts.

In addition, due to the excellent physical properties of the compositions of this invention having incorporated therein a metal compound represented by (A), (B), (C) and (D), heat transfer systems can be developed wherein a liquid heat exchange medium is utilized to exchange heat with another material wherein said material is at a given temperature. Thus, the function of the liquid heat exchange medium can be any one or a combination of the following: transfer heat, accept heat and maintain a material at a given temperature.

The fluid compositions of this invention when utilized as a functional fluid can also contain dyes, pour point depressants, metal deactivator, acid scavengers, antioxidants, defoamers in concentration sufiicient to impart antifoam properties, such as from about 10 to about 100 parts per million, viscosity index improvers such as polyalkylacrylates, polyalkylmethacrylates, polycyclic polymers, polyurethanes, polyalkylene oxides, polyalkylene polymers, polyphenylene oxides, polyesters, lubricity agents and the like.

It is also contemplated within the scope of this invention that the base stocks as aforedescribed can be utilized singly or as a fluid composition containing two or more base stocks in varying proportions. The base stocks can also contain other fluids which include, in addition to the functional fluids described above, fluids derived from coal I products and synthetic oils, e.g., alkylene polymers (such The embodiments of this invention in which an exclusive property or privilege is claimed are defined as follows:

1. A composition comprising (A) a major amount of an ester lubricant base stock,

and

(B) an oxidation improving amount of a material selected from the group consisting of compounds represented by the structure wherein Ar is an aromatic nucleus selected from the group consisting of benzene, benzoquinone and naphthalene, M is an alkali metal, R is selected from the group consisting of alkyl, aryl, and alkaryl hydrocarbon radicals, R is selected from the group consisting of hydrocarbonoxy radicals, hydrocarbon radicals, and

O -O--C Ro group, b is a whole number having a value of 0 to 6, and c is 0 to 1.

2. A composition of claim 1 wherein Ar is a naphthalene nucleus, R is an aromatic hydrocarbon radical, b is 0, and c is 1.

3. The composition of claim 2 wherein the oxidation improving material is the potassium salt of 2-hydroxy-3- naphthoyl-anilide.

4. A composition of claim 1 wherein Ar is a benzene nucleus, R is an alkyl radical and b and c are 0.

5. The composition of claim 4 wherein the oxidation improving material is the potassium salt of o-hydroxyacetophenone.

6. A composition of claim 1 wherein the ester base stock is selected from the group consisting of pentaerythritol esters, depentaerythritol esters, and mixtures thereof.

7. In a method of lubricating a gas turbine engine the improvement which comprises maintaining on the bearings and other points of wear a lubricating amount of a composition of claim 1.

8. In a method of lubricating a gas turbine engine the improvement which comprises maintaining on the bearing and other points of wear a lubricating amount of a composition of claim 3.

9. In a method of lubricating a gas turbine engine the improvement which comprises maintaining on the bearings and other points of wear a lubricating amount of the composition of claim 5.

References Cited UNITED STATES PATENTS 2,346,156 4/ 1944 Farrington et al. 25342.7X 2,810,696 10/1957 Lowe et a1. 25242.7X 3,347,791 10/1967 Thompson et al. 25242.7X

PATRICK P. GARVIN, Primary Examiner W. J. SHINE, Assistant Examiner