IL24342A - Functional fluid compositions - Google Patents

Description

C O H E N Z E D E K & S P I S B A C H R E G D . PAT E NT A TT O R N E YS 24, LEVONTIN STR., P. O. B. 1169 T E L - A V I V P A T E N T S & D E S I G N S O R D I N A N C E 13659/65 SPECIFICATION EONCTIONAL FLUID COMPOSITIOHS WE, HONSABTO COMPANY, a Corporation of the State of Delaware, of 600 North Lindbergh Boulevard, St. Louis 66, Missouri, U.S.A., DO HEREBY DECLARE Ihe nature of this invenfion and in what manner the same is to be performed to be particularly described and ascertained in and by the following statement: FUNCTIONAL- FLUID COMPOSITIONS This invention relates to novel functional fluid compositions comprising as base stocks dihalogenated diphenyl ethers and as blending agents . therewith halogenated lower alkylbenzenes, monohalogenated diphenyl ethers or chlorinated biphenyl or com-binations thereof. Wherever the term "halogen" or "halogenated" or the like is used herein,, only bromine and chlorine are contemplated.

Many different types of materials are 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) and as filter mediums for air conditioning systems. Because of the wide variety of applications and the varied conditions under which functional 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 hydraulic fluids, particularly aircraft hydraulic fluids, has posed what is probably the most difficult area of application. Thus, up to a few years ago the requirements for an aircraft hydraulic fluid could be described as follows: The hydraulic power systems of -aircraft for operating various mechanisms of an airplane impose stringent requirements on the hydraulic fluid used. Not only must the hydraulic fluid for aircraft meet stringent functional and use requirements but in addition such fluid should be as highly non-flammable as possible and must be sufficiently non-flammable to satisfy aircraft requirements for fire resistance. The .viscosity characteristics of the fluid must be such that it may be used over a wide temperature range; that is, -adequately high viscosity at high temperature , .low viscosity at low temperature and a low rate of change of viscosity with temperature. Such temperature range, is generally from -40°?. to 250°F. Its pour point should be low. Its volatility should be low at elevated temperatures of use and the volatility should be balanced; that is, selective evaporation or. volatilization of any important component should not take place at the high temperatures of use. It must possess sufficient lubricity and mechanical stability to enable it to be used in the self-lubricated pumps, valves, etc. employed in the hydraulic systems of aircraft which are exceedingly severe on the fluid used. It should be thermally and chemically stable in order to resist oxidation and · decomposition so that it will remain uniform under conditions of use and be able to resist the loss of desired characteristics due to high and sudden changes of pressure and temperature, high shearing stresses, and contact with various metals which may be, for example, aluminum, bronze, copper and steel. It should also not deteriorate the gaskets or packings of the hydraulic system. It must not adversely affect the materials of which the system is constructed^ and in the event of a leak, should not adversely affect the various parts^ of the airplane with which it may accidentally come in contact, such as electrical wire insulation and point. It should not be toxic or harmful to personnel who may come in contact with it.

While it is evident that the a orementioned requirements are quite severe, the development of the commercial sup.er-sonic transport (SST) has imposed requirements on any hydraulic fluid to be used therein which make the satisfaction of such prior requirements appear to be no problem at all.

In the first' place, the SST flight control system will be more difficult to design than that of any current commercial aircraft since it must have excellent flight control characteristics both at subsonic and supersonic speeds. It is estimated th^ the SST, a Mach 3 aircraft, will spend approximately half its time at the climb, hold, and approach conditions. Further, if past ana current trends are any indication, it can be assumed that the SST hydraulic functions will be somewhat more numerous than those of current commercial jets. Indications are —-that the commercial SST will have about 1000 hydraulic horsepower. This extended horsepower demand, needed to drive accessories, landing gear, and the control system, of itself will impose severe reliability considerations on the hydraulic fluid. Coupled to the factor of component numbers versus reliability is the factor of higher temperatures to which the system will be subjected. Surface temperatures of a Mach 3 aircraft will range from 50°F. to 600°F. or higher at stagnation points. By taking advantage of natural heat sinks, such as the fuel in a manner-utilized in the B-70, the hydraulic system should be capable of performing with a fluid operating at 00°F. to 500°F. On the other end of the temperature scale, temperatures as low as - 0°F are anticipated. ■ The Commercial Jet, Hydraulics Panel of SAE Αβ,, which was initiated during 19 l for the purpose of investigating and making recommendations for corrections of currer. c fire resistant jet hydraulic systems, found that 2/3 of all hydraulic system incidents during a 1-1/2-year period prior to June 19β2 were due to external system leakage, largely from components such as ''lines j fittings, hoses and seals. This leakage problem was considered by the panel and industry in general to be a very undesirable situation 'from 'the standpoint of loss of powered control. In the SST, any leakage problems would be magnified excessively over and above the loss of powered control when one " considers the temperatures involved. In this case, there is no longer the situation in which leakage fluid will issue into relatively cold areas but rather into ambient temperatures as high as 600°F. It is apparent that a flammable fluid Injected into hot compartments would create a blow torch effect, an- untenable condition. A fire-resistant fluid is thus of greater importance than ever before.

The principal problem facing a fluid supplier, therefore, is that o developing an SST fluid having temperature compatibility to approximately 400°F. to 500°F. combined with fire resistance. In addition to the foregoing an SST hydraulic fluid must still have the properties mentioned above, including good viscosity characteristic (over a quite extended temperature range), a low freezing point, low volatility, sufficient lubri- city, no toxicity and compatibility with various metals, packings and gaskets.

Basec upon the specifications of the various SST airframe manufacturers, the requirements for a hydraulic fluid for the SST and similar supersonic aircraft are expected to be as follows: While the SST requirements set forth above may not appear to be difficult to meet, these requirements are in fact quite severe for many reasons. For example, there are few, if any, individual compounds known which remain usable over the extreme temperature range of at least 550°F. (i.e., from -50°F crystallizing point to Q°F. thermal stability) much less provide such a usable rar. a, be fire resistant and also have the desired viscosities.

It is, therefore, 'an object of this invention ' to provide functional fluid compositions having a combination of properties, such as wide liquid range and fire-resistance, vni make such compositions well suited for the' various application mentioned above. It is a' further object of this invention to rovide functional fluid compositions- hich are useful as hydraulic fluids., particularly aircraft hydraulic fluids. A • further object is to provide functional fluids useful as hydraulic fluids in supersonic aircraft. Other objects -will be apparent from the following description of the invention.

It has now been found that functional fluids having excellent ire-resistance coupled with the physical properties necessary to provide compositions useful for the many applications disclosed above and particularly as aircraft hydraulic fluids comprise a major proportion of dihalogenated diphenyl ethers or sulfide and a minor amount of blending agents selected from halogenated lower alkyl benzenes,, monohalogenated diphenyl ethers and chlorinated biphenyl or combinations thereof* Preferred compositions suitable for use as aircraft hydraulic fluids under the SST conditions comprise certain dihalo- genated diphenyl ethers, and. minor amounts of said blending agents. As used herein the term "major amount" of a base stock means that the amount of a particular base stock in a specific- formulation is at least equal to the amount of any particular- blending agent in said formulation. On the other hand the term "minor amount" of a blending agent means that the amount of a particular blending agent in a specific formulation is no more than the amount of any specific base stock in said formulation.

■ The dihalogenated diphenyl ethers suitable for use as base stocks in the fluid compositions of this invention are those represented by the structure ~e A is oxygen or sulfur and X and Y are bromine or chlorine Typical examples of such ethers and sulfides are (1) 'dif: : er ■ent halogen on each ring: 2-oronio -21 -chlorodiphenyl ether, 2-bromo -2 ' -chlorodiphenyl sul ide , 2- omo -3' -c lorodiphenyl ether. 2-bromo -3' -chlorodiphenyl sulf 2-bromo _J -chlorodiphenyl ether, 2-b omo- -4 ' -chlorodiphenyl sulfide, 3-b om'o -2 ' -chlorodiphenyl ether , 3-brorao- ~2 ' -chlorodiphenyl ide, j5-bromo- -3' -chlorodiphenyl ether, 3-bromo- -3' -chlorodiphenyl sul 3-bromo- -4' -chlorodiphenyl ethe r, j3~bromo- -4 ■ -'chlorodiphenyl sul fi.de , 4~b omO' -3' -chlorodiphenyl e her, 4-bromo- -3' -chlorodiphenyl s ulfide. 4- romo- -4 ' -chlorodiphenyl ether, 4-bromo- -41 -chlorodiphenyl s l ide , 4-bromo- -2 ' -chlorodiphenyl ether and 4-bromo -2 ' -chlorodiphenyl sul:fide. (2) same halogen o " eac r~* ng: 2,2 1 -dibromodiphenyl ether, 9 9 i -dibromodiphenyl sulfide, 2,3 ' -dibromodiphenyl 2,3' -dibromodiphenyl sulfide, 2,4 ' -dibromodiphenyl ethe . 2,4' -dibromodiphenyl sulfide, 3,3 ' -dibromodiphenyl eihar, 3,3' -dibromodiphenyl sulfide, ; 1 -dibromodiphenyl e he , 3,4- -dibromodiphenyl sulfide, 4,4 1 -di romodiphenyl ether, 4,4' ■-dibromodiphenyl sulfide, ' -dichlorodiphenyl ethe , 2,2 '-dichlorodiphenyl sulfide, 2,3 ' -dichlorodiphenyl ether , 2,3 '-dichlorodiphenyl sulfide-, 9 il ' -dichlorodiphenyl e her 2.4 '-dichlorodiphenyl sulfide, 3,3 ' -dichlorodiphenyl ethe '-dichlorodiphenyl sulfide, 3, ' -dichlorodiphenyl ether . 3,4 '-dichlorodiphenyl sulfide, it . ' -dichlorodiphenyl ether a d < , 4 ' -dichlorodiphenyl sulfide The ethers are · enerally preferred over the sulfides because their lc- r melting points make them usable in a wider-number of applications and of the ethers, those in which the halogen substituents are in the 3,4'- relationship are pre-' ferred for use in the compositions of this invention, because their low melting points are the lowest of all the base stocks of the instant invention .

• The blending agents which can be used to provide the novel compositions of this invention include the halogenated lower alkyl (Ci_4) benzenes containing 1 to 5 halogens, such as - roiTiomethylber. ene , 2-bromoe-ohylbenzene, 4-bromopropyi-benzene, 4-chlorobutylbenzene 2, 4-dichlorometh lbenzene , 2 5~ dibrcmcethylbenzene , 2 , ¼-dibromoethylbenzene , 2 , 4-dichloro-eth l er.zene , 2-broino- -chloroethylbenzene , 2, 5-dibromoethyl-benzene, 3,4-aibrorr.oethylbenzene, 3,5-dibromopropylbenzene, 2,4-dichlorabutylbenzene, and the like. It is preferred to use the bromine-containing compounds because of the increased fire-resistance obtained thereby. Further examples of halogenated alkyl benzenes are tri- and tetrachloroe h lbenzene , tri- and tetrabrcmoethylbenzene , pentachicromethylbenzene, pentachloro-eth lbenzene, 'pentabro.moethylbenzene, pentabromopropylbenzene, pentachlorobu ylbenzene and the like.

In addition to the use of specific compounds, there can be used a mixture of halogenated alkyl benzenes such as the mixture of brominatec ethyl benzenes disclosed in United States Patent No. 2,257, 9 , which contain an average of two atoms of bromine per ol of ethyl benzene. The mixture of Example 1 of U. 3. 2,257,903 is particularly preferred for use in the fluids of this invention because of its low crystallizing point.

Other blending agents include the monohalogenated di-p enyl ethers such as 2-ch.iorodIphenyl ether, 5-chlorodiphenyl ether, ½-chlorodiphenyl ether, 5-bromodiphenyi ether and the like and chlorinated diphenyl which is illustrated by the chlorinated biphenyl commercially available as products con-taining about 21j», 5 , 5K% and β0<¾ of combined chlorine corresponding approximately to mono-, di-, tri-,' terra- penta- and hexachlorobiphenyl, respectively. The expression chlorinated biphenyl containing a stated percentage of combined chlorine is used herein as not only including these directly · chlorinated products, but also as blends of one or more chlorinated biphenyl whereby the total chlorine content is broadly within the ' range of 20% to 60%, preferably "within the range of % zo 2% by weight. It is also preferred, in order to. obtain fluids having low crystallizing points, to use chlorinated biphenyl which has been isomerized and preferably distilled thereafter according to the teachings of United States Patent No. ,068,297- The preparation of the base stock compounds used to provide the compositions of this invention is illustrated by the following examples in which parts are parrs by weight.

Example 1 Into a suitable reaction vessel fitted with an agitator, a reflux condenser and heating and cooling means, there is charged 610 parts of 3-chlorodiphenyl ether and 2 parts of powdered iron. The resulting mixture is heated to about 69-iS. followed by the slow addition of 320 parts of liquid bromine. n mass, is maintained of bromine the reac- tion mass is slowly heated to about- ^3~6- and then held at that temperature for four hours. The pressure in the reaction system is then lowered to about 100-200 mm. of Hg. and maintained for about minutes in order to remove as much residual hydrogen d I* bro in^ as possible. Afte a oixt 70°C. , 10 parts of c JO suiting mixture is fractionated to gi\re a main fraction containing lJ— romo-3 ' -chlorodiphenyl ether and a small amount of the other isomers s ch as the 3*3'- isomer. The product is a colorless liauid having an index of refraction, ^5 of 1.6128, " 298°F-316°F a specific gravity of 1.485 and a boiling range of i^Q-i^ -Q-* , at 1.0 mm. of Hg.

Alternatively the mixed halogen-containing diphenyl ethers can be prepared by the Ull an reaction. Although this method yields the desired product in pure form, it is a somewhat expensive procedure and is, therefore, not as commercially attractive, especially since the procedure illustrated in Example 1 yields a mixture having of the order of 90 of the desired product which mixture is quite useful in the instant invention. The sulfides can be prepared by reacting an alkali , metal halothiophenolate with a dihalobenzene in a carboxamide or N-alkyl pyrrol!do e. An example of the preparation of a base stock compound of this invention by the Ullman reaction' is given below.

Example 2 are Into a suitable reaction vessel there S»s- charged 212.1 parts of m-chlorcphenol and 84.2 parts of potassium hydroxide followed by the -addition of 150 ml. of toluene. The resultin mixture is heated to complete formation of the potassium chloro- phenolate vjhile removing, azeotropicall , 3 ml. of water. The toluene is then stripped and 500 ml. of diglyme is added. There are then charged to a different reaction vessel 707-7 parts of p- dibro obenzene , 5 parts of cuprous chloride and 3 parts of potas 329°F siu iodide. The resulting mixture is heated to A&^°C, and then the phenolate previously prepared is slowly charged over about one and one-half hours. After completing the phenolate addition the reaction mass is helc at l65°C. for an additional five hours The diglyrne is then stripped and the residue diluted with ether and filtered,, washed with 10$ caustic solution and water and dried. The purified residue is then fractionated to provide and an index of refraction,,' ¾? of 1.6158.

Example '5 Into a suitable reaction vessel containing- 9^ parts of m-dibromobenzene there was slowly charged a solution of potas-0 sium phenate in diglyrne (prepared by dissolving 122 parts of potassium hydroxide in 257-1 parts of p-chlorophenol and removing the water formed by distillation using toluene ) , 6 parts of cupro chloride and parts of potassium iodide. The resulting mixture was heated at l65°C. , with agitation, for about five hours after 5 which the diglyrne was removed by distillation by heating the mixture at reduced pressure. The residue remaining was then taken up in ether and the solids removed by filtration. The ether solution was then washed with 10$ caustic solution followed by washing with water, and dried. The ether was then 0 evaporated and the residue fractionated to give the desired product, 5-hrcmc-~ ' -chlorcdiphenyl ether, which had a boiling point 262°F -naa&a of ½S-&r at 0.2 mm. of Hg. , a melting point of 7°F. (-1 °C.) and an index of refraction, n^5 of 1.6150.

Example In 'c e manner of Example 5, the potassium salt of m- chlorophenol was reacted with _~dichlorobenzene to nrovide ΐ> '~ > 235°F ( dichlorodiphenyl ether -whic had a boiling point of ·ϋ¾?<6-» at 0.5 mm. of Hg. , a melting point of l4°F. ( -10°C. ) and an index of refraction, n2^5. of 1.5950. 0 E ample 5 were 200 ml. of N~me thylpyrrolldone and the resulting mixture \ was were heated to 150°C. There/w&s then charged 125- parts ' ί ^potassium hydroxide in 500 ml. of ethanol after which the reaction mixture was at reflux for about eleven hours. The reaction, mass was then cooled, taken up in ether and filtered. The filtrate was washed with dilute caustic solution, then with water, am dried. The residue as then frac 3-bromo ~4 ' chlorodiphenyl sulfide vhicn had 147 C. at 0.2 mm. of Kg., a melting point of 104°F. (40°C.); and an index of refraction, n rj of 1.6608.

Example 6 In the manner of .Example 5, 1 7 parts of p_-chlorothio~ phenolj 1 parts of m-diohlorobenzene and ^β.Ι parts of potassium hydroxide were reacted in -methylpyrrolidone to provide 3,4 ' -dichlorodiphenvl sulfide which had a boiling point of 127°C. at 0.4 mm. of Kg., a melting point of 86°F. (30°C. ) and an index' of refraction, ¾ of 1.6454.

Other base stock compounds of this invention can be similarly prepared. Typical properties of the above-prepared and other base stock compounds of this invention are set. forth in Table I, below. The tests or procedures used to measure the various properties of the fluids of this invention and the components thereof are as follows: Viscosity ASTM D-445-βΙ Hot Manifold Test AMS 3150C High Pressure Spray Test AMS 3150C Autogenous Ignition Temperature ASTM _ D-2155-63T In addition, the solution or melting point of the compositions of this Invention were also measured. Because the compositions of the instant invention easily supercool (as do the components) crystallizing points are difficult to determine.

However, since solution point and crystallizing point, coincide the solution point was' generally measured.

Solution 'points were determined by placing a test com- ' '5 position in a test tube provided with an' agitator and suspending the apparatus in a well -insulated dry ice-acetone bath. The dry ice-acetone bath was maintained at a temperature in the. range of -30°F.- to -50°F. , a range considered- high enough to prevent a ii.ss from forming and low enough to speed up potential crystallization. After a test composition had been agitated for about eight hours, seeds of one of the components were added. The seeded composition was then stored in a cold box ■ at - 50°F. for sixteen hours and then agitated in the dry ice-, acetone bath for eight hours. The cycle was then repeated.

Those mixtures which did not crystallize after one week were warmed, to room temperature to make the fluids pcurable and were transferred to small bottles with lids. The bottles were then placed in cold storage at -60°F.

The thermal stability of the components and co posi- 0 tions of this invention were determined by the use of an isoteni- scope according to the procedure of Blake et al. , J. Chem. Eng. Data, 6 , 67 ( 19β1 ).. when a fluid is heated in the isoteniscope apparatus, it exerts a vapor pressure which can be readily _ measured. The vapor pressure increases as temperature is in- 5 creased f llowing a straight-line relationship .when logarithm of pressure is plotted versus the reciprocal of the absolute tem erature. The vapor pressure curve will depart from a straight line if decomposition occurs to give volatile products. The temperature at which this occurs is called the decomposition D temperature (¾) .

Several tests were used for the measurement Of the fire resistance of the. instant fluids since there is no single test-that can be use to evaluate all types of fluids under all expected use conditions. The degree of fire resistance in any given test is influenced by the characteristics of the fluid, the type of flair.e or source of ignition, the total amount of energy available in relation to the amount of fluid, the physical state of the fluid^ and many ether factors.

The early technical committees working on fire-reslstan hydraulic fluid specifications for aircraft recognized the many factors involved in assessing fire resistance. As a result, the specifications developed by the SAE and the military required several different methods for testing the flam ability of proposed products.

These specifications include the same general type of fire resistance tests. The tests were designed to simulate conditions in aircr ft resulting from a broken line spraying hydraulic fluid into various sources of ignition and are known as the "High-pressure Spray Test/' and the "Hot Manifold Test."' An additional tes often used, which is a smaller scale test, is the Molte -me tal Pour Test. In this test the fluid under evaluation is dropped from a medicine dropper or poured from a calibrated test tube onto the surface of molten aluminum alloy which has been heated to about 1250 °F. If spontaneous ignition dees not occur, a flame is placed in . the vapors to determine if they can be ignited.

TABLE I ^το.τ; the properties set forth in Table I above, it ist evident that the base stock compounds have a combination of physical properties which make them well suited for' use as f nctional fluids, yet -in most cases they are deficient with respect to some property which limits their commercial applicability. The problem to which the present invention is directed, therefore, is to provide functional fluids having the combination of properties discussed above and which, therefore, retain the good fire resistance of the base stocks yet are improved with respect to one or' more other properties,, such as low or high . temperature viscosity or solution point. The problem can also be stated, in the case of those base stocks not having the desired fire resistance, of improving their fire resistance without adversely affecting viscosity and thermal stability and to also obtain fluids having good low temperature properties.

Representative properties of typical blending agents used in the compositions of this invention are set forth in Table IIi below.

Solution r Boiling The mal Blending Agent Point Point Stabilit °F. °F. . «';O -Bromop enyl phenyl ether 65 2-Ch 1oropheny 1 phenyl ether 105 2-Br or. -.oph eny 1 ■phenyl .eti:-..-r 111 Ί -Ch 1oro pheiny 1 phenyl e her 21 2Qi\ The deficiencies of the aforedescribed base stock compounds of this invention are signi icantly improved by the addition of such compounds of the above-described blending agents to thereby provide the compositions of the instant invention, . typical examples of which and their propc ".ies are listed in Table III, belov;.' Similarly compositions of this invention can be ba on the use of a dihalodiphenyl sulfide instead of a dihalodi phenyl ether. Typical examples of. such compositions are set forth below in Table IV.

The compositions of this invention also possess good · lubricating properties as evidenced by the results obtained . from testing of such compositions on the Four-ball machine. Typical results are listed in Table V below. The composition numbers are for the compositions listed in Table III.

• ' In addition to the above the compositions of this invention are shear stable and are not prone to foaming and any foam formed is not stable. Furthermore, the claimed compositions have good sta ility,- even at temperatures of 550°F. and in the presence of oxygen, and are essentially non-corrosive to metals, such as aluminum j aluminum bronze, iron, silver and titanium. A further advantage of the instant compositions is their out- standing hydrolytic stability.

As a result of the excellent physical properties of the functional fluids particularly described in the preceding examples, improved hydraulic pressure devices c n be prepared in accordance ' with this invention which comprise in combination a fluid chamber and an actuating fluid in said chamber, said fluid 'eompris ;.:vv. 'mixture of one or more of the ba.se stocks hereinbefore described.- In such a hydraulic apparatus /herein a movable member is actuated y the above-described functional fluids, performance characteristics are obtainable which are superior tc those heretofore obtainable.

Because of the excellent fire-resistance of the functional fluids of this invention, their exceptionally low pour points, and good lubricity, the functional fluids of this invention can be utilized in those hydraulic systems wherein pcv.'er must be transmitted and the f ictional parts of the system- lub icated by the hydraulic fluid utilized. Thus, the novel functional fluids of this invention find utility in the trans-■ mission of power in a hydraulic system having a pump therein supplying the power for the system. 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 the . 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 or relief valves. Fluid motors are usually constant- or 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 interesting to note that the base stock compounds of this invention which contain one bromine atom and one chlorine atom possess a unique . combination of fire resistance' and viscosity. Thus, such compounds are as fire resistant or have the ability to impart as much fire resistance as chlorinated biphenyl ethers and sulfides containing at least three chlorine atoms but do .not suffer from the problem of having the high viscosities at low temperatures which is common to such trichlorinated compounds and which problem is further. magnified with compounds containing more than three chlorines. The chlorine- and bromine-containing compounds are ; therefore, preferred moieties of the instant invention because such combination of fire resistance and good low temperature viscosities make them particularly well suited for use in hydraulic fluid formulations where wide variations in temperature are likely to be encountered.

. The compositions of this invention can also contain dyes, pour point depressants, antioxidants, viscosity index improvers, suc as pol alkylacrylates and polyalkylmethacrylates lubricity agents and the like.

While this invention has been described with respect to various specific examples and embodiments, it is to be understood that the invention is not limited thereto and that it can be variously practiced within the scope of the following claims.

Claims (1)

1. HAVING NOW partioularly described and ascertained the our said and in manner the same le to be we declare that what wo is t of the invention which an or claimed functional fluid A a amount of a base stock selected t e group consisting of a cihalogenated diphenyl ether represented by the structure c where A is a gen having an atomic number of 8 to 16 and and Y are selected from the group consisting of bromine and chlorine and mixtures and a minor amount of a blending agent selected from the group consisting of a lower benzene where the halogens are selected from the group consisting of bromine and a monohalogenated diphenyl ether where the halogen is selected the group consisting of and a chlorinated having from about to about by weight of combined and mixtures A composition of Claim 1 where the base stock is dihalogenated dipnenyl ether in which A is composition of 2 where X is and Y chlorine functional fluid A on comprising a amount of and minor amount of a blending agent selected from group consisting of a lower benzene where the halogens are selected from the group consisting of bromine and chlorine a dipnenyl ether the halogen is selected from the group consisting of bromine and a chlorinated having from about to about by weight of combined and mixtures functional fluid composition of Claim 4 where the blending agent is a onohalogenated dipnenyl ether functional fluid comprising ft a major amount of ethe and a minor amount of functional fluid osition a major amount of and a of functional fluid of Claim where the blending agent is a halogenated lower uted A major amount of and amount of dibromoethylbenzene functional fluid of Claim where the blending agent is a chlorinated having from about to about by weight combined functional fluid composition comprising a major amount of a base stock selected from the consisting of a dihalogenated diphenyl ether represented by the structure where A is a having an atomic number of 8 to 16 and X and Y are selected from the group consisting of bromine and and mixtures and a onohalogenated diphenyl ether where the halogen is selected from the group consisting omine and functional A by from about to about r and ingly from about to about functional fluid A Composition by about about chlorinated biphenyl having about 5 by weight about dibromoethylbenzene and about functional fluid A of Claim 1 where the base stock is a dihalogenatec diphenyl ether in which A is functional fluid composition of X is bromine and is A hydraulic system containing as the fluid a composition of Claim A hydraulic system containing as the operative fluid a composition of Claim A hydraulic system containing as the operative fluid a composition of Claim In the method of operating a hydraulic pressure device wherein a displacing force is transmitted to a able member by means of a hydraulic the improvement which comprises employing as said hydraulic fluid a composition of Claim functional fluid as described and DATED THIS 19th day of Z K SPSBAH insufficientOCRQuality