US2686760A

US2686760A - Hydraulic fluids and lubricating compositions

Info

Publication number: US2686760A
Application number: US253556A
Authority: US
Inventors: Forrest J Watson
Original assignee: Shell Development Co
Current assignee: Shell Development Co
Priority date: 1951-10-27
Filing date: 1951-10-27
Publication date: 1954-08-17
Anticipated expiration: 1971-08-17

Description

Patented Aug. 17, 1954 HYDRAULIC FLUIDS AND LUBRICATING COMPOSITIONS Forrest J. Watson, Berkeley, Calif., assignor to ShellDevelopment Company, Emeryville, Califi, a corporation of Delaware No Drawing. Application October 27, 1951, "Serial No. 253,556

This invention is directed to lubricating compositions and hydraulic fluids having improved technical properties. More particularly, the invention pertains to such compositions containing components imparting-improvedlow temperature properties, corrosion resistance and low fiammability.

Current developments in aviation and industrial fields require the use of lubricants and hydraulic fluids having high resistance to corrosion, ilow flammability, and especially improved properties at the low operating temperatures which are encountered, for example, during the operation of aircraft, and the like. Numerous proposals havebeen made for correcting one or another of theseaproperties, but such correction is usually .elfected .at the expense of another property of the fluids. For example, the use of aryl phosphates, such as tricresyl phosphate, as a hydraulic fluid is satisfactory only at moderate temperatures due to the highsensitivity of .said phosphates to thermal influences. The aryl phosphates, however, are beneficial in having great resistance to flammability. Heavy mineral oils may be used in similarsituations, but are of limited use under cold conditions due to their high pour points. Alkyl phosphates may be used under certain limited conditions .in an unmodified state, but are usually unsuitable for lubricating purposes and the like due to their-mediocre resistance to flammability and their inherent low viscosity. Mixtures of lubricants have been suggested, but heretofore such combinations have been limited due, for example, "to the relatively lowrniscibility of aryl phosphates with mineral lubricating oil's.

:"It is an object of the present invention to provide improved lubricantsfor use at both low and high temperatures. It is another :object of this invention :to provide improved hydraulic fluids :and lubricating compositions combining in an optimum degree the properties of .high non-flammability and low response to thermal "changes. Other objects will become apparent during the following discussion.

Now in accordance with the present invention, it has been found that the aboveand other ob jects may be accomplished by combining high viscosity index bright stock with normally liquid aliphatic phosphorus esters. More specifi- 6 Claims. (Cl. 252-75) cally, the compositions-ofthe present invention comprise from about 7.5% to about by weight of ahigh viscosity index bright stock and from about 40% to about 925% of an aliphatic ester of a phosphorus acid,

THE COMPOSITIONS The compositions of this invention comprise two main ingredients as generally referred to above. In their preferred embodiments, the hydraulic fluids of this invention comprise from about 30 to about 50% by Weight of a bright stock and from about 50% to about by weight of an aliphatic ester of a phosphorous acid. While these compositions are preferred for use as hydraulic fluids, somewhat difierent mixtures are more suitable for use as aircraft turbo-prop or turbo-jet lubricants. The latter preferably contain from about 9 to about 20% of bright stock and from about to about 91% of an aliphatic ester of a phosphorus acid. In both types of compositions the preferred ester is a tri-alkyl phosphate, which will be defined more fully hereinafter. Optimum properties are obtained, however, if the tri-alkyl ester contains alkyl groups having at least 6 carbon atoms and usually between about 6 and about 12 carbon atoms each, the total carbon atom content of each molecule thus being at least about 18 carbon atoms.

In addition to the two principal components which are the essential features of this invention, other ingredients may be added in order to provide desirable properties. An especially effective type of additive for the prevention of corrosion under oxidizing conditions in this particular mixture of liquids comprises the metallic salts of condensation products of formaldehyde with alkyl phenols; preferably the calcium salt is employed. A synergistic effect has been found to occur in this composition when the latter additive is combined with an aromatic amine such as phenyl alpha naphthylamine. In addition, other important additives finding use with certain of the subject compositions compriseespecially pour point depressants such as the polymerized esters of the acrylic acid series and the like, especially aliphatic esters of polymerized methacrylic acid.

BRIGHT STOCK While the present invention is not to be confinedto the use of a mineral oil derived from any particular source or by any particular refining process, the usual source of suitable mineral oils comprises the fraction thereof generally termed bright stocks, and particularly bright stocks having a viscosity index of at least 60. The term bright stock is one which is well recognized in the art of refining mineral oils. To obtain the desired fraction, crude oils are usually subjected to distillation under ordinary pressures in order to obtain a long residue comprising the fraction which does not distill under these conditions without substantial decomposition. The long residue is then subjected to steam distillation,

usually under a vacuum. Under these conditions,

gas oil and waxy lubricant fractions distill over, leaving what is normally termed a short residue or a steam refined stock, also known as cylinder stock. The steam refined stock is then deasphalted (if an asphaltic crude is employed) and subjected to dewaxing operations to remove microcrystalline or macrocrystalline waxes. Following this, the rafiinate is treated with a solvent for the purpose of reducing or removing the aromatic fractions. Clay contact treatment or percolation may be employed to clean up the oil following any one or all of these separate operations. The rafiinate which remains after deasphalting, dewaxing, extraction, and clay treatment is generally called bright stock.

The bright stocks suitable for use in the present compositions should have the following ranges of properties:

Table I PROPERTIES OF BRIGHT STOCKS Viscosity, S. U. S,, 100 F. 1250, usually 125011,000,

preferably 1500-3500 Viscosity, S. U. 8., 210 F. 75, usually 125-325, preferably 150-250 Viscosity index +60, preferably +85-110 Aniline point, C. 100, preferably 115 Flash, F. 475, preferably 500 Fire, F. 550, preferably 600 Pour point, F.maximum 25, preferably lower than 15 Percent aromatics 15, preferably 10 opt. 5

Percent naphthenes 35 Percent paraffines, at least 60 The tables which follow give :the properties of typical bright stocks which are useful in the compositions of this invention.

4 vention is predicated upon the use of a mineral oil fraction having the above defined ranges of properties and not upon the source or treatment of such oil. I

The two most important inherent properties of a mineral oil suitable for the present use comprise the aromatic content and the viscosity characteristics. The aromatic content has a large influence upon the sensitivity of the oil to thermal changes and the viscosity of the oils defines their suitability for their present purpose. Hence, the best definition with respect to essential characteristics of mineral oil suitable for the present compositions comprises those having an aromatic hydrocarbon content less than about 15% by weight and having a viscosity of between about 1250 and about 11,000 SUS at 100 F. Having defined these particular properties, the other properties such as flash, fire, aniline point, and viscosity index usually, are largely dependent upon them.

THE PHOSPI-IORUS ESTERS The phosphorus esters useful for inclusion in the present compositions comprise the normally liquid aliphatic esters of acids of phosphorus.

While the trialkyl phosphates are particularly preferred, other classes are suitable in addition to or in place of said phosphates. These include dialkyl hydrocarbon phosphonates, especially dialkyl alkanephosphonates, alkyl dialkanephosphinates, diphosphorus compounds such as bis (dialkyl phosphono)alkanes, bis(alky1 alkane phosphino) alkanes, alkane diol bis(dialkane phosphinate), alkane diol bis(dialkyl phosphates), alkane diol bis(alky1 alkane phosphonates) and the corresponding ethers of the above diphos- Table II EXAMPLES OF TYPICAL BRIGHT STOCKS SUS Ring Analysis Ratio of Viscos- Paraf- Average Average fines to Mol Rings per 100 210 Index Aro- Naph- Paraf- Naph- Weight Mol matic thenes fines thenes Mid-Continent Bright Stock-Convcntional Extraction 3, 650 164 77 13 17 4. 1 685 3. 7 M1d-Oont nent Bright Stock-Mild Extraction 2, 569 141 9 19 72 3. 8 685 3. 4 Mid-Continent Bright StockHeavy Extractlon 2, 049 131 93 3 21 76 3. 62 675 2. 9 Pennsylvania Bright Stock... 2, 109 144 102 5 16 79 4. 730 3. 0 Coastal Bright Stock 1, 251 85 63 4 35 61 1. 74 515 3- 4 Table III SPECIFICATIONS FOR TYPICAL MID-CONTINENT BRIGHT STOCKS Unfiltered Filtered 24.5 25. 5 Dark Green. (3. 7

l0. 10 545 610 -150 Viscosity Index, minimum- 90 mg, clay treating, acid treating, and the like. 75

Hence, it will be recognized that the present in phorus compounds. Classes of the latter which are included are bis(dialkyl phosphono alkyl) ethers, bis(alkyl alkanephosphinico alkyl)ethers and bis(dialkyl phosphato alkyl) ether.

The phosphorus esters which are particularly useful in these compositions ordinarily have a total of at least 18 carbon atoms per molecule; preferably this total is between about 20 and about 32 carbon atoms per molecule. Typical trialkyl phosphates which are especially suitable contain alkyl radicals having from about 6 to about 12 carbon atoms each and include the following:

Trihexyl phosphates Triheptyl phosphates Tricotyl phosphates, e. g.,

Tri(2-ethylhexyl) phosphate OR Tri (isooctyl) phosphate Trinonyl phosphates, e. g.,

Tri (3,5,5-trimethylhexyl) phosphate Tridecyl phosphates Tridodecyl phosphates pihexyl octyl phosphate aeeaveo 5,. Typical species of phosphonates and phosphinates are given below:

Dialkyl hydrocarbon phosphonates:

Di( 2-ethylhexyl) hexanephosphonate Dihexyl hexanephosphonate l Dioctyl(3,5,5 trimethylhexane) phosphonate Dihexyl benzenephosphonate A-lkyl dialkane phosphinates:

Butyl di(2-ethylhexane) phosphinate Hexyl diheptane phosphinates Referring now to the diphosphorus compounds, these may be represented with the following general formula:

wherein each R is an aliphatic hydrocarbon radical.

The above classification of diphosphorus compounds includes especially substituted aliphatic hydrocarbons bearing 2 phosphorus radicals in the form of phosphate, phosphonate, phosphinate, or phosphine oxide groups. One of the more preferred classes of liquids suitable for use, according to the present invention, includes the bis(dialkyl phosphono)a1kanes. These have the general configuration of Preferably R1 in the above formula is an alpha, omega-alkylene hydrocarbon radical of at least 3 carbon atoms. Each of the other R substituents may be a hydrocarbon radical of such nature that the entire compound is substantially fluid at operating temperatures. Preferably each of these groups contains from 3 to 9 carbon atoms each, and still more preferably at least two of them are of branched configuration. The following suitable species are typical of this presented configuration:

Bis-1,3-(diisobuty1 phosphono) propane Bis-1,4+ (diisopropyl phosphono) butane Bis- 1,5- [di (B-methylbutyl) phosphonol pentane Bis-1,6- [di(2-ethy1hexyl) phosphonol hexane Bis-1,3- [di(3,5,5-trimethylhexyl) phosphonolpropane The alkylene group separating the two phosphorus radicals may be shorter than about 12 carbon atoms or may be of branched configuration as typified by the following species:

Bis-1,2-(di-tert-butyl phosphono) ethane Bis-1,2- (di-tert-butyl phosphono) -3,l-dimethylpentane Bis-2,5l- (di-sec.-buty1 phosphono) -3,5-dimethylhexane Bis-1,6- (di-n-pentylphosphono) -3,4,5-trimethylhexane Another suitable subgeneric group of phosphorus compounds useful in the practice of this invention comprises the alkanediol bis(dialkane phosphinates). These materials have the general configuration:

The preferred configurations and carbon contents of the individual portions of this and the following classes are in general those given in the foregoing description of the bis dialky1 phosphono alkanes except where especially noted. Preferably the substituent R1 contains from 3 to 9 carbon atoms while the remaining Rs have from i to 9 carbon atoms each. The following species are typical of this class:

1,5-pentanediol bis- [di (2-ethylhexane) phosphinate] 1,6-hexanedio1 bis- [di (2-isobutane) phosphinate] L'I-heptanediol bis-(di-n-butanephosphinate) 3,4-heptanediol bis-[di(3,5,5 trimethylhexane) phosphinate] 2,5-hexanediol bis-(dipentanephosphinate) l Another class of compounds coming within the general scope of this invention are the tetraalkylalkylenediphosphine oxides. These materials have the following general formula:

Ihe following species are typical of this class of compounds:

The following list of suitable species illustrates this group:

1,6-hexanediol bis(dibutyl phosphate) 3-methyl1,6-hexanediol bis(di-tert-butyl phosphate) 2,3-diethyl-1,6-hexanediol bis(di-sec-amyl phosphate) 2,4,e-trimethyl 1,5-pentanediol bis(di-3,5,5 trimethylhexyl phosphate) 1,4-butanediol bis(diisopropyl phosphate) Another sub-generic class constitutes alkanediol bis alkyl alkanephosphonates) which have the general configuration:

The suitable species which follow illustrate the nature of this class:

1,5-pentanediol bis-(butyl butanephosphonate) 1,4-butanediol bis-(tert-butyl 2-methyl-1-pro- .panephosphonate) l,6-hexanediol bis-(3,5,5-trimethylhexyl butanephosphonate) 3, l-dimethyl-1,6-hexanediol bis-(tert-amyl pentanephosphonate) 1,2-ethanediol bis-(3,5,5-trimethylhexyl butane- .phosphonate) l Another class of compounds to be considered includes bis-(alkyl alkanephosphinico)alkanes which have the general configuration:

This class is exemplified by the following species:

It will be understood that symmetrical compounds are not necessary for the operation of the present invention. For example, the various substituents denoted as R in the above general formulae may vary within a given compound,

both with respect to carbon atom content and to spatial configuration. The branched configurations are favored due to their generally superior effect upon the lubricating characteristics, especially at low temperatures. Unsaturated hydrocarbon radicals are especially to be desired when they are directly attached to a phosphorus atom since their presence has been found to improve the corrosion characteristics of lubricants prepared therefrom. Additionally, while the two end groups may be identical in a single compound for specific purposes, it is sometimes desirable to include two different types of phosphorus end groups in order to obtain the beneficial properties attributable to each type. Suitable illustrating compounds having mixed end groups are as follows:

l (butyl butanephosphinico) 2 (di secbutyl phosphono)ethane l (di 2 ethylhexanephosphinate) 5 (dibutyl phosphate) pentanediol Typical species of the corresponding ethers of di-phosphorus compounds are the following:

Bis-E di-amylphosphono) methyl] ether Bis-E (di-laurylphosphono) ethyl] ether Bis- (butyl hexanephosphinico) ethyl] ether Bis-E (di-isopropyl phosphono) amyll ether Details of the preparation and properties of these and other ethers will be found in copending application Serial No. 214,432 filed March 7, 1951, by Denham Harman et al.

The above classes of compounds may be prepared by the following typical methods:

The preparation of bis-(dialkyl phosphono)- alkanes illustrates the conditions necessary for the preparation of typical compounds. In this particular instance sodium is suspended in a suitable solvent (such as refluxing heptane) after which a dialkyl phosphite is added and refluxed for a period of 1 to 4 hours to form a sodium dialkyl phosphite. Subsequently a dibromoalkane is gradually added to the refluxing solution. After heating for 1 to 8 hours at reflux, the corresponding bis-(dialkyl phosphono) alkane has been formed. Sodium bromide is filtered off and the remaining solution is water Washed, neu tralized with dilute alkali, water-washed again and the volatile diluent is removed by topping to a temperature of about 150 C. at 150 mm. pressure. If a highly purified product is desired the bottoms from this topping operation may then be distilled in a molecular still to obtain a purified product as distillate.

The preparation of alkanediol bis-(dialkyl phosphate) is preferably effected by reaction of an alkylene glycol with a dialkyl chlorophosphate in the presence of a hydrogen chloride acceptor. Preferably the components are added to one another at a temperature between about 10 C. and +20 C. and then warmed on a steam bath for a period of time between about 1 hour and 16 hours, preferably between 2 and 4 hours. Typical hydrogen chloride acceptors are amines, such as trimethylamine, pyridine, or dimethylaniline. Alternatively, the hydrogen chloride evolved during the reaction may be removed as it is formed by a current of air. Followin the reaction, the mixture is water-washed to remove hydrochloride salts or the salts (such as pyridine hydrochloride) may be removed by filtration. The mixture isthen washed with dilute hydrochloric acid to remove any excess base which may be present. Purification may be completed by distillation of the volatile constituents leaving the desired phosphate compounds.

In the preparation of the tetra-alkylalkylenediphosphine oxides, the following conditions have been found to be suitable: A tetra-alkyl diphosphonoalkane is treated with phosphorus pentachloride at a temperature between 75 and C. for a period of time, preferably between 2 and i hours. The product of this reaction is a tetrachlorodiphosphonoalkane. This product is then treated with a Grignard reagent (an organo magnesium halide) at a temperature between 0 and 25 C; for a period of 2 to 4 hours. The resulting product is the desired bis-phosphine oxide.

A suitable preparation for bis-(alkyl alkanephosphinico)alkanes comprises treatment of a dialkyl alkanephosphonite with a dibromoalkane under the conditions of the well-known Arbuzov reaction.

One property of this general class of diphosphorus derivatives distinguishing them from the more commonly employed monophosphates, such as trioctyl phosphate, is their exceptional behavior with respect to corrosion. These materials have been found to be substantially noncorrosive with respect to copper, magnesium, iron, cadimium, or aluminum. As a class, the diphosphorus compounds described hereinbefore have suitable properties for use as hydraulic fluids. In general, their viscosities are between 10 and 25 centistokes at about room temerature. The derivatives bearin 4 alkane to 2 phosphorus linkages or 2 alkane to l phosphorus linkages have substantially higher viscosities making them especially suitable as synthetic lubricating 011s. The latter compounds include especially alkanediol bis- (dialkanephosphinate) The following table illustrates the unexpected properties of a typical composition coming within the definition of the present invention:

Table IV PROPE RTIES Trioctyl Phosphate Percent 100 Bright Stock, Percent 100 Viscosity Index" 90 98 Pour Point, F 80 +27 -50 Flammability- 14 l7 acea'zeo This, table shows, that an unexpecteduresult wasobtained inthe changes in three. properties.

resulting. from a the combination of trioctyl phosphate with a typical. brig-ht stock. In the first place, the viscosity index, of the blend is. about 50% higher than the viscosity indexof either of the components. The reasonfor this is obscure,

. sequently a base such aslime may be added and but constitutes an unexpected and beneficial result adding substantially to thevalue of this.

combinationof fluids. Secondly, it will be found fromthe above data that the pour point of the low that of the higher pqur point of one of the.

components. Hence, it was unexpected to discover that in this particular combination the resulting pour pointof the blend was in fact 77 F. lower than that of the component having the higher pour point. Finally, this table shows an unexpected feature with respect to flammability. While this term is dependent upon the exact physical conditions under which the fluid is to be used, a testcalled the Pipe Cleaner Flammability Test has been devised for differentiating between fluids under standard conditions for this property. Under the conditions which will be described hereinafter, the addition of bright stock to .tri-octyl phosphate actually reduced flammability instead of increasing it as would normally be. expected. In other words, the addition of a mineraloil (which is normally regarded as relatively flammable) reduced the flammability of a phosphate estenwhich is normally regarded asrelatively non-flammable. Hence, the present invention is particularly predicated upon the unexpected findings in these three properties, namely, with respect to viscosity in:

dex improvement, blended pour point advantage and reduction in fiammability.

METALLIC SALTS Insome applications the compositions as defined hereinbefore cause corrosion of certain metals, and under oxidizing influences exhibit an increase in viscosity under operating conditions. Itwas found that only certain specific classes of additives could be. eifectively used in correcting these phenomena. The most eifective additive for the purpose comprises the metallic salts of condensation products of formaldehyde with alkyl phenols. While the preferred metal in this respect is calcium, other effective metals are alkaline earth metals such as barium and magnesium. These may be supplemented by heavy metal salts and alkali metal salts of the subject condensation products such as zinc, aluminum, copper, lead, iron, nickel, cobalt, manganese, chromium, tin, sodium, potassium and lithium.

The alkyl phenols are preferably thosehaving used. Underthese conditions an efiective reducheating continued for a similarlength of time inordr to formthe metallic salt. Alternatively the salt may, be formed Simultaneously with condensation by utilizing the, metallic base as the condensation catalyst. Preferably mineral oil is also present so that the resulting product is obtained in the form of an oil concentrate ready for addition to liquid compositions. Further details of this type of roduc are to be found in U. S. Patent 2,250,188 issued July 22, 1941, 170

Chester E. Wilson.

In improving the compositions of this invention by the useof such salts, amounts between about 0.25% and about 5% by weight may be tion in metallic corrosion may be obtained. The

following table illustrates the properties of a typatleast one alkyl group with from 4 to 12 carbon atoms. The most effective members for the present purpose are tertiary alkyl phenols having from about 5 to about 9. carbon atoms per alkyl radical. The condensation product formed between these alkyl phenols and formaldehyde are enerally prepared by heatingone Incl of the phenol with between about 7 and one molof formaldehyde with a catalytic amount of an acid or base. Normally these metals are heated for pericd l e w n' about on andt r e our at a temperature between about 175 and 225 F. S ubicai composition containing about 1.0% of a calcium salt of the condensation product formed between formaldehyde and amyl phenol.

Table V Oxidation corrosion test, 16s hr. at 250 F'.--wt.

loss, mg /cmi Cu 0.03 Mg 0.02 Fe 0.02 Cd 3.81 1 0.01 Per cent increase in viscosity at 100 F. AcidNeut. No. after use 15.9 4 ball. wear (7 kg., C.) 0.21 Pipe cleaner flash 17 Pipe cleaner fire. 21

AROMATIC AMINES Table VI Trioctylphosphate, wt. percent 59. 8 Bright Stock, wt. percent 38. 2 Calcium Salt, Wt. percent 1 0 Phenyl alpha nephthylamine, wt. percent Viscosity Cs. F Viscosity Cs. 210 F Viscosity Index Pour Point, F Acid Neut. N o MILO5606 Specification-Oxidation Carrosion Percent Increase in Viscosity at 100 F Acid Neut. No. after use diamine. The alkylated phenyl amines are also useful such as l-isopropyli-amino benzene, 1- hexyl 3 amino benzene, l amino 2 methyl- G-ethylbenzene and 1-amino-ZA-diethylbenzene.

In order to provide an effective synergistic result with the metallic salts described hereinbefore, the aromatic amines should be present in an amount between about 0.25 and about 5% by weight of the total composition. In the absence of the metallic salts described above, the aromatic amines have proved to be unsatisfactory for the purpose of stabilizing these compositions against oxidation corrosion. On the other hand, as described above, the metallic salts do not fully protect cadmium against corrosion and permit a substantial increase in viscosity upon exposure to oxygen. However, as the data contained in Table VI indicate, combinations of these two additives provide substantially complete protection in these respects.

The pipe cleaner flammability test is made as follows: A pipe cleaner, reduced to 4 inches in length, is saturated with fluid to be tested, the excess drained and the cleaner inserted in a metal holder. It is then cycled at 36 R. P. M. between two electric hot plates mounted horizontally one-half inch apart with ceramic grids over the open coil heaters. The temperature between the grids varies between 760 and 710 C., dropping during the test. The number of passes necessary to cause initial flash and continuous fire are recorded.

In addition to the ingredients described hereinbefore, these compositions may contain other lubricating oil and hydraulic fluid components or additives. In certain compositions wherein the proportion of bright stock is above about 35% and the composition is to be used at relatively low temperatures, it is desirableto incorporate therein one or more pour point depressants. The

most satisfactory type of material comprises polymerized esters of the acrylic acid series. These include especially the esters of methacrylic acid and of acrylic acid. The former are available as commercial products and are sold under the trade name Acryloid. The esters to be used should have molecular weights from about 5,000

to about 25,000, which will be understood to be an average figure for the mixture of polymers normally present. The acids are esterified with aliphatic alcohols having from 2 to carbon atoms and the polymers may be homopolymers of a single ester or may be copolymers of a mixture of such esters. The term polymerized esters will be understood to include both of these types.

Another type of pour pointdepressant suitable for use in the present compositions includes the condensation products of high molecular weight parafiins and polycyclic aromatics such as the condensation products produced by condensing chlorinated paraffin wax and naphthalene.

I claim as my invention:

1. A composition comprising essentially from about 50% to about 92.5% by weight or a; normally liquid trialkyl phosphate said ester having at least 18 carbon atoms per molecule, from about 7.5% to about 60% by weight of a mineral oil bright stock having a viscosity of between about 1250 and 11,000 SUS at F., said oil containing less than about 15% by weight of aromatic hydrocarbons and said composition containing from about 0.25% to about 5% by weight of an alkaline earth metal salt of a condensation product of formaldehyde with alkyl phenols the alkyl groups thereof containing from 4 to 12 carbon atoms, and 0.25-5% by weight of a naphthylamine.

2. A hydraulic fluid composition comprising the following ingredients in the stated proportions:

Per cent.

Trioctylphosphate 59.8:

Mineral oil bright stock 38.2:

Phenyl alpha-naphthylamine 1. Calcium salt of the condensation product of formaldehyde with amyl phenol 1 Trioctyl phosphate 50-70 Mineral oil bright stock 30-50 Phenyl alpha naphthylamine 0.25-5

Calcium salt of the condensation product of formaldehyde with amyl phenol 0.25-5

said mineral oil bright stock having a viscosity of between about 1250 and 1,000 SUS at 100 F. and containing less than about 15% by weight of aromatic hydrocarbons.

4. A hydraulic fluid composition comprising essentially the following ingredients in the stated proportions:

Per cent by weight Trialkyl phosphate, each alkyl radical thereof containing from 6 to 12 carbon atoms 50-70 Mineral oil bright stock 30-50 Phenyl alpha naphthylamine 0.25-5

said mineral oil bright stock having a viscosity of between about 1250 and 1,000 SUS at 100 F.

and containing less than about 15% by weight.

of aromatic hydrocarbons.

5. A hydraulic fluid composition comprising essentially the following ingredients in the stated proportions:

Per cent by weight Trialkyl phosphate, each alkyl radical thereof containing from 6 to 12 carbon atoms 50-70 Mineral oil bright stock 30-50 A naphthylamine 0.25-5 Calcium salt of the condensation product of formaldehyde with amyl phenol 0.25-5

said mineral oil bright stock having a viscosity of between about 1250 and 11,000 SUS at 100 F. and

omatic hydrocarbons.

Calcium salt of the condensation product of formaldehyde with alkyl phenol, each alkyl radical thereof containing from 4 to 12 carbon atoms 025-5 said mineral oil bright stock having a viscosity of between about 1250 and 11,000 SUS at 100 F. and containing less than about 15% by weight of aromatic hydrocarbons.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,175,877 Clark Oct. 10, 1939 2,251,531 Wiezevich May 13, 1941 2,250,188 Wilson July 22, 1941 2,397,380 Smith et a1 Mar. 26, 1946 2,509,620 Watson et a1 May 30, 1950

Claims

1. A COMPOSITION COMPRISING ESSENTIALLY FROM ABOUT 50% TO ABOUT 92.5% BY WEIGHT OF A NORMALLY LIQUID TRIALKYL PHOSPHATE SAID ESTER HAVING AT LEAST 18 CARBON ATOMS PER MOLECULE, FROM ABOUT 7.5% TO ABOUT 60% BY WEIGHT OF A MINERAL OIL BRIGHT STOCK HAVING A VISCOSITY OF BETWEEN ABOUT 1250 AND 11,000 SUS AT 100* F., SAID OIL CONTAINING LESS THAN ABOUT 15% BY WEIGHT OF AROMATIC HYDROCARBONS AND SAID COMPOSITION CONTAINING FROM ABOUT 0.25% TO ABOUT 5% BY WEIGHT OF AN ALKALINE EARTH METAL SALT OF A CONDENSATION PRODUCT OF FORMALDEHYDE WITH ALKYL PHENOLS THE ALKYL GROUPS THEREOF CONTAINING FROM 4 TO 12 CARBON ATOMS, AND 0.25-5% BY WEIGHT OF A NAPHTHYLAMINE.