US3730897A

US3730897A - Fire-resistant functional fluids

Info

Publication number: US3730897A
Application number: US00129268A
Authority: US
Inventors: R Mccord; D Nail; M Sheratte
Original assignee: McDonnell Douglas Corp
Current assignee: McDonnell Douglas Corp
Priority date: 1971-03-29
Filing date: 1971-03-29
Publication date: 1973-05-01
Anticipated expiration: 1990-05-01

Abstract

PRODUCTION OF FUNCTIONAL FLUIDS, PARTICULARLY AIRCRAFT HYDRAULIC FLUIDS, OF IMPROOVED FIRE RESISTANCE, COMPRISING A FUNCTIONAL FLUID BASE STOCK, SUCH AS A PHOSPHATE ESTER, E.G., DI-N-BUTYL PHENYL PHOSPHATE, OR MIXTURES OF SUCH BASE STOCKS, AND A SMALL AMOUNTS OF AN ARYL SELENIDE COMPOUNDS, PREFERABLY A CHLORINATED ARYL SELENIDE, E.G., ETHYL P-CHLORO PHENYL SELENIDE.

Description

United States Patent 3,730,897 FIRE-RESISTANT FUNCTIONAL FLUIDS Robert S. McCord, Pacific Palisades, Donald H. Nail, Los Angeles, and Martin B. Sheratte, Reseda, Calif assignors to McDonnell Douglas Corporation, Santa Monica, Calif. No Drawing. Filed Mar. 29, 1971, Ser. No. 129,268 Int. Cl. C09k 3/00 U.S. Cl. 252-78 25 Claims ABSTRACT OF THE DISCLOSURE Production of functional fluids, particularly aircraft hydraulic fluids, of improved fire resistance, comprising a functional fluid Ibase stock, such as a phosphate ester, e.g., di-n-butyl phenyl phosphate, or mixtures of such base stocks, and a small amount of an aryl selenide compound, preferably a chlorinated aryl selenide, e.g., ethyl p-chloro phenyl selenide.

This invention relates to functional fluid compositions having proved fire resistance and is particularly directed to compositions comprising certain functional fluids and an additive amount sufficient to improve fire resistance, of certain selenium compounds.

Many different types of materials are employed as functional fluids and functional fluids are utilized in a wide variety of applications. Thus, such fluids have been utilized as electronic coolants, diffusion pump fluids, lubricants, damping fluid, power transmission and hydraulic fluids, heat transfer fluids and heat pump fluids. A particularly important application of such functional fluids has been their utilization as hydraulic fluids and lubricants in aircraft, requiring successful operation of such fluids over a wide temperature range, a particularly important and highly desirable property of such fluids being fire resistant.

Functional and hydraulic fluids employed in many industrial applications and particularly hydraulic fluids for aircraft must meet a number of important requirements. Thus, such hydraulic fluids particularly for aircraft use, should be operable over a wide temperature range, should have good stability at relatively high temperatures and preferably have lubricating characteristics. In addition to having the usual combination of properties making it a good lubricant or hydraulic fluid, such fluid should also have relatively low viscosity at extremely low temperatures and an adequately high viscosity at relatively high temperatures, and must have adequate stability at the high operating temperature of use. Further, it is of importance that such fluids be compatible with and not adversely affect materials including metals and non-metals such as elastomeric seals of the system, in which the fluid is employed. It is particularly important in aircraft hydraulic fluids and lubricants that such fluids have as high a fire resistance as possible to prevent ignition if such fluids are accidentally or as result of damage to the hydraulic system, sprayed onto or into contact with surfaces or materials of high temperature.

While many functional and hydraulic fluid compositions have been developed having most of the aforementioned required properties, many of these compositions do not have the requisite high fire resistance desired particularly for use of such functional fluid or hydraulic fluid compositions in modern high speed aircraft or in a hydraulic system located near a high temperature jet-turbine power plant of a jet-turbine aircraft.

Thus, as an illustration, many functional and hydraulic fluids have an autoignition temperature ranging from about 450 to about 750 F. It is particularly desirable to increase the autoignition temperature of such functional and hydraulic fluids to the range of about 800 to about 1,000 F.

It has now been found in accordance with the present invention that the fire resistance, or autoignition temperature, of functional fluid or hydraulic fluid compositions, can be significantly improved by the addition to such compositions of a small amount of certain selenium compounds, in the form of certain aryl selenides and diselen-ides, especially chlorinated phenyl selenides and diselenides, defined in greater detail hereinafter. The inclusion of such selenium additives in functional and hydraulic fluid compositions generally does not adversely affect any of the above noted important characteristics of such fluids, particularly aircraft hydraulic fluids, including their desirable viscosity characteristics.

Another important feature is that certain recently developed hydraulic fluids for aircraft use have been designed particularly to have reduced density, but many of these low density fluids have inferior fire resistance to the higher densiity hydraulic fluids, and it has been found that selenium additives of the invention when incorporated into such low density fluids substantially increase the fire resistance and reduce the flammability of these low density hydraulic fluids.

The use of dialkyl selenides as oxidation inhibitors for orthosilicate fluids is described in U.S. Patent 3,118,841 to Moreton. In such patent the selenide, e.g., dilauryl selenide, is employed in combination with other oxidation inhibitors such as phenyl alpha naphythylamine. However, selenides which inhibit oxidation in liquids do not necessarily function to reduce flammability, or to increase autogenous ignition temperature of a fluid, and in such patent only orthosilicates are employed as the base stock. Further, many of the selenides are toxic, thermally unstable, insufliciently soluble at the working temperature, or have an objectionable odor. Certain selenides also tend to corrode metals. Moreover, in order to effectively reduce flammability, selenium compounds should also possess the property of decomposing in the plasma condition in flames to prevent or poison continuation of the flame.

It has been found that the aryl selenides and particularly the chlorinated aryl selenides of the invention not only function to substantially increase autogenous ignition (autoignition) temperature and reduce flammability of a wide variety of functional fluids and hydraulic fluids, but in addition have the advantageous properties of being thermally stable, free from toxicity, relatively free from corrosion, do not have an objectionable odor, and have sufiicient solubility in most functional and hydraulic fluids to effectively function as flame inhibitors. In addition, the aryl, particularly the chlorinated aryl, selenides employed according to the invention have no adverse effect on low temperature viscosity of the functional fluids, particularly when employed as hydraulic fluids in aircraft, do not adversely affect the thermal stability of the fluid, and are of relatively low cost.

Effective selenium compounds, that is aryl selenides, for use as additives in functional and hydraulic fluids to reduce flammability and increase autoignition temperature of the fluid, according to the invention, have the formula ArSeR, where Ar is a member selected from the group consisting of aryl and substituted aryl including a substituent selected from the group consisting of alkyl, halogen, alkoxy, aryloxy, amino and dialkylarnino, and R is a member selected from the group consisting of unsubstituted and substituted alkyl, aryl and aryloxy, including a substituent selected from the group consisting of halogen, amino and diakylamino; and SeAr, where Ar has the same definition as Ar above, and Ar and Ar are the same or different.

Thus, Ar and Ar can be phenyl, naphthyl anthranyl, and the like, and such aryl groups can contain alkyl substituents, such as methyl, ethyl, propyl, butyl, and branched chain alkyls such as isopropyl and isobutyl, and the like, halogen atoms such as chlorine and bromine, alkoxy such as methoxy, ethoxy, propoxy, and the like, aryloxy such as phenoxy and naphthoxy, amino and dialkylamino such as dimethylamino, diethylamino, and the like, such alkyl groups containing from 1 to about carbon atoms. R can be alkyl such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, and the like, of from 1 to about 10 carbon atoms, aryl such as phenyl, naphthyl, and the like, aryloxy such as phenoxy and naphthoxy, and substituted alkyl, aryl and aryloxy radicals containing substituents such as halogen, e.g., chlorine and bromine, amino and dialkylamino such as dimethylamino and diethylamino, and the like, such alkyl groups containing from 1 to about 10 carbon atoms.

The preferred aryl selenides according to the invention are those selected from the group having the general formulae:

SeR

e-Se

where X is selected from the group consisting of H, alkyl, both straight chain and branched chain and having 1 to about 10 carbon atoms, such as methyl, ethyl, propyl, butyl, isopropyl, pentyl, and the like, halogen such as chlorine and bromine, alkoxy such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, amino and dialkylamino such as dimethylamino, diethylamino, and the like, and R is alkyl of from about 1 to about 12 carbon atoms, both straight and branched chain, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, hexyl, and the like.

Compounds which have been found particularly effective according to the invention are the halogenated, e.g., chlorinated or brominated aryl selenides, especially the chlorinated aryl selenides, that is, selenides of the formulae noted immediately above, where X is halogen such as chlorine. The aryl nuclei of the above noted formulae each can contain one or more of the X, e.g., chloro or bromo, substituents, such as one, two or three such halogen, e.g., chlorine, atoms on each of the phenyl nuclei. The most desirable chlorinated selenides of these types have been found to be ethyl p-chlorophenyl selenide and 4,4-dichlorodiphenyl diselenide. Other exemplary chlororinated aryl selenides having a structure as defined by the above formulae include methyl p-chlorophenyl selenide, ethyl and propyl o-chlorophenyl selenides, methyl and ethyl 2,4-dichlorophenyl selenides, ethyl 2,4,6- trichlorophenyl selenide, 2,2'-dichlorodiphenyl diselenide, 2,4,2',4'-tetrachloro diphenyl diselenide and 2,4,6,2,4', 6-hexachloro diphenyl diselenide. Brominated analogues corresponding to the above specific examples of the chlorinated selenides and diselenides can be employed.

The following base stocks are illustrative of typical base stocks that can be utilized in preparing the functional fluid compositions of the present invention, and the instant invention can be practiced utilizing the various modifications of the base stocks which are set forth below.

Preferably functional fluid base stocks are employed which are selected from the group consisting of phosphorus esters, amides of an acid of phosphorus, diand tricarboxylic acid esters, and petroleum hydrocarbons.

Phosphorus esters which can be employed according to the invention have the general formula:

Rt-O.

R20m-P=0 Rr-O 4 where s, m and n can be 0 or 1, and not more than two of s, m, and n can be 0, where R R and R each can be aryl such as phenyl and naphthyl, alkaryl such as cresyl, xylyl, ethyl phenyl, propyl phenyl, isopropyl phenyl, and the like, said aryl and alkaryl radicals preferably containing from 6 to about 8 carbon atoms, alkyl, both straight chain and branched chain of from about 3 to about 10 carbon atoms such as n-propyl, n-butyl, namyl, n-hexyl, isopropyl, isobutyl, and the like, and alkoxyalkyl having from about 3 to about 8 carbon atoms such as methoxy methyl, methoxy ethyl, ethoxy ethyl, methoxy propyl, and the like.

The corresponding phosphonates can also be employed, where one of s, m and n is 0, and the corresponding phosphinates where two of s, m and n are 0.

Preferred phosphorus esters are the dialkyl aryl, triaryl, trialkyl and alkyl diaryl phosphates.

Examples of such phosphate esters are the dialkyl aryl phosphates in which the alkyl groups are either straight chain or branched chain and contain from about 3 to about 10 carbon atoms, such as n-propyl, n-butyl, n-amyl, n-hexyl, isopropyl, isobutyl, isoamyl, and the aryl radicals have from 6 to 8 carbon atoms and can be phenyl, cresyl or xylyl, particularly dialkyl phenyl phosphates including dibutyl phenyl phosphate, butyl amyl phenyl phosphate, butyl hexyl phenyl phosphate, butyl heptyl phenyl phosphate, butyl octyl phenyl phosphate, diamyl phenyl phosphate, amyl hexyl phenyl phosphate, amyl heptyl phenyl phosphate, and dihexyl phenyl phosphate.

Examples of triaryl phosphates to which the aryl selenides, especially chlorinated selenides of the invention can be added are those in which the aryl radicals of such phosphates have from 6 to 8 carbon atoms, that is, may be phenyl, cresyl or xylyl, and in which the total number of carbon atoms in all three of the aryl radicals is from 19 to 24, that is, in which the three radicals include at least one cresyl or xylyl radical. Examples of such phosphates include tricresyl, trixylyl, phenyl dicresyl, and cresyl diphenyl phosphates.

Examples of trialkyl phosphates employed according to the invention include phosphates having alkyl groups which are either straight chain or branched chain with from about 3 to about 10 carbon atoms, such as n-propyl n-butyl, n-amyl and n-hexyl, particularly tri-n-butyl phosphate, tri(2-ethyl hexyl) phosphate and triisononyl phosphate, the straight chain alkyl groups preferably containing from 4 to 6 carbon atoms.

Examples of alkyl diaryl phosphates which can be employed to produce the invention compositions include those in which the aryl radicals of such phosphates may have from 6 to 8 carbon atoms and may be phenyl, cresyl or xylyl, and the alkyl radical may have from about 3 to about 10 carbon atoms, examples of which are given above. Examples of the alkyl diaryl phosphates include butyl diphenyl, amyl diphenyl, hexyl diphenyl, heptyl diphenyl, octyl diphenyl, 6-methyl heptyl diphenyl, 2-ethylhexyl diphenyl, butyl phenyl cresyl, amyl phenyl xylyl, and butyl dicresyl phosphates.

Functional fluid base stocks according to the invention also include phosphonate and phosphinate esters having alkyl and aryl groups corresponding to thoese defined above with respect to the phopshate esters.

Examples of phosphinate esters to which the invention principles are applicable include phenyl-di-n-propyl phosphinate, phenyl-di-n-butyl phosphinate, phenyl-di-n-pent yl phosphinate, p-methoxyphenyl-di-n-butyl phosphinate, tert-butylphenyl-di n butyl phosphinate. Examples of phosphonate esters to which the invention is applicable include aliphatic phosphonates such as alkyl alkenyl phosphonate, e.g., dioctyl isooctene phosphonate, an alkyl alkane phosphonate such as di-n-butyl n-octane phosphonate, di-isooctyl pentane phosphonate, and dimethyl decane phosphonate, a mixed alkl aryl phosphonate, for example, di-octyl phenyl phopshonate, di(n-amyl) phenyl phosphonate, di(n-butyl) phenyl phosphonate, phenyl butyl hexane phosphonate and butyl bis-benzene phosphonate.

Another class of phosphorus-containing compounds in which the selenides of the invention can be employed as additives are the amides of acids of phosphorus, e.g., amido phosphates, including the mono-, diand triamides of an acid of phosphorus, an example of which is phenyl N-methyl N-n-butyl-N-methyl-N'-n-butyl phosphoro-diamidate. Additional examples are m-cresyl-p-cresyl-N,N- dimethylphosphoroamidate, di-m-cresyl |N,N dimethylphosphoroamidate, di-p-cresyl N,N dimethylphosphoroamidate, phenyl-N,N-dimethyl-N',N'-dimetliylphosphorodiamidate, N methyl-N-butyl-N',N"-tetramethylphosphorotriamidate, N,N'-di-n-propyl-N"-dimethylphosphorotriarnidate.

Another class of functional fluid base stocks whose antoignition temperature can be improved by incorporation of the aryl selenides, particularly the chlorinated aryl selenides of the invention are the diand tricarboxylic acid esters, particularly the dicarboxylic acid esters. Preferred types of the latter compounds are the alkyl diesters of adipic and sebacic acid, that is the diester adipates and sebacates. Such esters can contain alkyl groups, either straight chain or branched chain, containing from about 4 to about 12 carbon atoms including butyl, isobutyl, amyl, pentyl, hexyl, isohexyl, nonyl, decyl and isodecyl groups. Specific examples of these base stocks are dihexyl, di Z-ethylhexyl, dioctyl, dinonyl, didecyl and diisodecyl adipate, and the corresponding sebacates. Also, the diesters of the dicarboxylic aromatic acids, particularly the diesters of phthalic acid, that is the phthalate diesters can be employed as base stocks. The diesters of such acids can contain alkyl groups of from 4 to 12 carbon atoms, examples of which are given above with respect to the diesters of the dicarboxylic aliphatic acids, adipic and sebacic acid. Illustrative examples of the diester phthalates which can be employed are di-n-butyl phthalate, dihexyl phthalate, dioctyl phthalate, dinon'yl phthalate, didecyl phthalate, and diisodecyl phthalate.

There can also be employed as functional fluid base stocks according to the invention the esters of tricarboxylic acids, particularly the aromatic tricarboxylic acids such as trimellitic acid. The triesters of such acids can contain alkyl groups of from 4 to 2 carbon atoms, illustrative examples of which are noted above with respect to the dialkyl esters of phthalic acid, specific examples of trimellitate triesters including tri-butyl, tIi-hexyl, trioctyl, tri-isooctyl, tri-nonyl, tri-decyl and tri-isodecyl trimellitate.

There can also be employed as functional fluid base stocks to which the aryl selenides are added according to the invention, petroleum hydrocarbons, which can contain carbon chains of from C to about C carbon atoms. A typical example of such a petroleum hydrocarbon is the red petroleum hydrocarbon liquid according to military specification MILH-5606B, understood to contain carbon chains of about C to about C carbon atoms, generally employed as a hydraulic fluid in military aircraft.

It is also contemplated within the scope of the present invention that mixtures of individual functional or hydraulic fluid components are included to form a single base stock. Thus, for example blends of esters of an acid of phosphorus can be employed, e.g., a blend of tri-nbutyl phosphate and tricresyl phosphate, blends of an ester of an acid of phosphorus and a dicarboxylic acid diester such as the aliphatic diesters of adipic, sebacic or phthalic acid, e.g., a mixture of tri-n-butyl phosphate and di-isodecyl adipate and/or diisodecyl phthalate, or a combination or blend of dicarboxylic acid diesters and/ or tricarboxylic acid triesters can be employed, such as a blend of di-isodecyl adipate and di-isodecyl phthalate.

Thus, there can be employed as functional fluid base stocks a blend or mixture of a phosphorus ester such as a phosphate and an alkyl diester of phthalic acid, with or without an alkyl diester of adipic acid and/or of sebacic acid, wherein said alkyl groups contain from about 4 to about 12 carbon atoms as described and claimed in the copending application Functional Fluid Compositions, M. B. Sheratte, Ser. No. 129,270, filed Mar. 29, 1971. In addition, functional fluid base stocks can be utilized comprising a blend or mixture of a phosphorus ester such as a phosphate and an alkyl diester of adipic acid and /or of sebacic acid, as defined above, and as described and claimed in the copending application, Functional Fluids, M. B. Sheratte, Ser. No. 129,269, filed Mar. 29, 1971.

The functional or hydraulic fluid base stocks employed and described above, can also contain other additives such as viscosity index improvers, in a small amount ranging from 0 to about 10%, generally about 2 to about 10%, by weight of the composition. Examples of the latter are polyal kyl acrylates and methacrylates, the polyalkyl methacr'ylates generally being preferred, and in which the alkyl groups may contain from about 4 to about 12 carbon atoms, either straight or branched chain. Specific examples of such viscosity index improvers are polybutyl methacrylate and poly n-hexyl acrylate, having an average molecular weight between about 6,000 and about 12,000. Other additives such as corrosion inhibitors, stabilizers, metal deactivators, and the like, can also be employed.

For greatest effectiveness in substantially reducing the flammability, and for correspondingly substantially increasing the autoignition temperature of the above functional fluid base stocks according to the invention, it is usually desirable to employ only a small amount of the aryl selenide or halogenated aryl selenide in the functional or hydraulic fluid base stock. Generally, there can be employed as little as 0.25% and up to about 5% of the selenide additive of the invention, preferably from about 0.5 to about 2% of such selenide, in the functional fluid base stock, based on the weight of the composition. It has been found that an optimum amount of such selenide additive ranges from about 0.8 to about 2% by weight of the composition.

The following are examples of preparation of two of the preferred chlorinated selenide additives of the invention, such examples being simply exemplary of the preparation generally of the aryl selenides employed as additives according to the invention:

EXAMPLE 1 Preparation of 4,4-dichlorodiphenyl diselenide Magnesium (24.0 g., 1.0 mole) was placed in a 2000 ml. flask, which was equipped with a reflux condensor, stirrer, thermometer, liquid addition funnel, power addition funnel and a nitrogen inlet and outlet. Selenium powder (87 g., 1.1 mole) was placed in the powder addition funnel, and the entire apparatus was evacuated for several hours to remove traces of water. The apparatus was then filled and flushed with dry nitrogen.

A solution of p-dichlorobenzene (147 g., 1.0 mole) in tetrahydrofurane (300 ml.) was placed in the liquid addition funnel. 7

Approximately 1 ml. of ethylene dichloride was added to the flask to activate the magnesium, and then about 20 ml. of the p-dichlorobenzene solution was run in. The reaction generally started within 10-20 minutes and the vigorous exotherm took the temperature to 90 C. When the initial vigorous reaction had subsided, the rest of the p-dichlorobenzene solution was added at a rate which maintained the temperature at 6585 C. When all the dichlorobenzene had been added, the mixture was heated under reflux for an hour, forming the intermediate reaction product, p-chlorophenyl magnesium chloride.

The temperature was then allowed to fall to about 65 0., and the selenium powder was added carefully so that the temperature of the mixture remained below 80 C.

After all the selenium had been added, the mixture was again heated under reflux for 1 hour, forming p-chlorophenyl selenium magnesium chloride. After cooling, the resultant mixture was cautiously poured over a mixture of 300 ml. concentrated hydrochloric acid and 500 g. ice. Air was bubbled through the resultant mixture for 20 hours, after which the selenium-containing product, 4,4- dichlorodiphenyl diselenide, was obtained as a greenish stilf paste. The aqueous layer was decanted, and the green paste was dissolved in tetrahydrofurane. The product was filtered from excess selenium powder, which was recovered. The filtrate was evaporated to dryness, and the solid orange product was washed once with methanol. After drying, the product was a yellow to orange powder, which weighed 133 g., corresponding to a 70% yield. The theoretical yield is 190.5 g.

EXAMPLE 2 Preparation of ethyl p-chlorophenyl selenide A solution of p-chlorophenyl selenium magnesium chloride was prepared as described in Example 1 above, and dissolved in 60 ml. tetrahydrofurane. To this solution was slowly added 0.2 mole of ethyl chloride. After the exothermic reaction had stopped, the reaction mixture was heated under reflux for 1 hour. The mixture of products was dissolved in ether, washed several times with water, dried over sodium sulphate, and fractionally distilled. In addition to an approximately 60% yield of ethyl p-chlorophenyl selenide, approximately 25% of 4,4'-dichlorodiphenyl selenide and 10% of 4,4'-dichlorodiphenyl diselenide were also obtained.

The following are examples illustrating practice of the invention by incorporation of aryl selenide additives according to the invention into functional fluid base stocks. In the examples below the term AIT means autoignition temperature, the autoignition temperature of the functional fluid compositions of the invention according to the examples below being determined in accordance with standard method of test for autoignition temperature in accordance with ASTM D 2155 procedure.

EXAMPLE 3 TABLE 1 Additive coneentra- AIT Additive tion, percent F.)

4,4'-dichlorodiphenyldiselenide 740 d 0. 3 875 0. 6 910 0.9 930 From Table 1 above it is seen that incorporation of only 0.3% by weight of the chlorinated selenide additive increases AIT of the control fluid A from an AIT of 740 F. to 875 F., and that increased proportions of the chlorinated selenide additive to 0.9% increases AIT further to 930 F., almost 200 F. higher than the 740 F. AIT of the control fluid.

EXAMPLE 4 To the functional fluid blend A of Example 3 is added ethyl p-chlorophenyl selenide in an amount of 0.6% by weight of the composition, and the AIT of the resulting composition is determined against the control fluid A containing no selenide additive. The results are shown in Table 2 below:

TABLE 2 Additive concentra- AIT Additive tion, percent F.)

Fluid:

A Ethyl p-chlorophenyl selenide 0 740 A do 0. 6 930 From Table 2 above, it is seen that the addition of 0.6% of the chlorinated additive of this example increases the AIT of 740 F. for the control containing no selenide additive, to 930 F.

EXAMPLE 5 TABLE 3 Additive coneentra- AIT Additive tion, percent F.)

Fluid:

B Ethyl p-chlorophenyl selenide. O 700 B .do 0. 6 850 From the Table 3 above it is seen that the AIT of the invention composition containing the chlorinated selenide is increased from an AIT of less than 700 F. for the control, to 850 F.

EXAMPLE 6 Ethyl p-chlorophenyl selenide is added to a red petroleum hydrocarbon liquid containing hydrocarbon chains ranging from C to C (MIL-H-5606B), designated C in the table below, in an amount of 0.6% by weight of the total composition, and the AIT of the resulting composition, determined against a control of the same petroleum hydrocarbon liquid but in the absence of any additive selenide. The results are shown in Table 4 below:

TAB LE 4 Additive concentra- AIT Additive tion, percent F.)

Fluid:

C Ethyl p-chlorophenyl selenide- 0 470 C do 0. 6 590 It is noted from Table 4 above that the AIT of the control composition C of 470 F., is increased to 590 F. by the incorporation of the chlorinated selenide noted above in an amount of 0.6% by weight.

EXAMPLE 7 Phenyl ethyl selenide is added to tri-n-butyl phosphate in an amount of 0.5% by weight of the composition, and the resulting composition D tested for AIT against a control of tri-n-butyl phosphate containing no selenide.

The control has an AIT of 730 F. and the blend containing the above phenyl ethyl selenide in an amount of 0.5 has a substantially higher AIT of 915 F.

EXAMPLE 8 To the functional fluid blend A of Example 3 above, is added 4,4-di(seleno ethyl)diphenyl ether, in an amount of 0.6% by weight of the total composition. The composition containing the selenide additive is tested for AIT against a control of fluid A in the absence of any selenide.

The resulting composition containing the above selenide has an AIT of 900 F. against an AIT of only 740 F. for the control rfluid A.

EXAMPLE 9 To a blend of a functional fluid containing 50% diisodecyl adipate, 30% tri-n-butyl phosphate and 20% dibutyl phenyl phosphate, by weight, designated composition E, is added 4,4'-dichlorodiphenyl diselenide, in an amount of 0.9% by weight of the composition, and the hot manifold temperature of the resulting composition containing the chlorinated selenide is obtained against the control composition E containing no selenide.

Hot manifold temperature is obtained by a standard procedure, Federal Test Standard 791, method 6053, and varying the manifold temperature to note the maximum temperature of non-ignition.

The hot manifold temperature of the control composition E is 1,070 F., whereas the hot manifold temperature of the same functional fluid blend E containing the 0.9% of the above chlorinated diselenide is 1,240 F.

EXAMPLE 10 To a blend of a functional fluid containing 50% diisodecyl adipate, 40% tri-n-butyl phosphate, and 10% triisodecyl-tri-mellitate, designated composition F, is added ethyl p-chlorophenyl selenide in an amount of 0.9% by weight, and the AIT of the resulting composition is obtained against the control composition F in the absence of any selenide.

The AIT of the control composition F is only 630 F., whereas composition F containing the above chlorinated selenide has a substantially higher AIT of 850 F.

EXAMPLE 11 To a functional fluid blend containing 39% tri-n-butyl phosphate, 47% di-isodecyl adipate, and 10% di-isodecyl phthalate, and containing minor amounts of oxidation inhibitor, designated composition G, and to another functional fluid blend containing 56% tri-n-butyl phosphate, 35% di-isodecyl adipate, 5% poly-n-hexyl acrylate having an average molecular weight of about 12,000 as viscosity index improver, and a small amount of oxidation inhibitor additive, designated composition H, is added 4,4- dichlorodiphenyl diselenide in each case in an amount of 0.8% by weight of each of the blends.

The AIT of each of the above compositions G and H containing the chlorinated aryl selenide, and the AIT of the corresponding controls, compositions G and H, each in the absence of any selenide, are obtained, and the results noted in Table 5 below:

TAB LE 5 Additive concentra- AIT Additive tion, percent F.)

From Table above, it is seen that the AIT of each of the controls, compositions G and H, in the absence of any selenide is 600 F., and such AIT was substantially increased to 870 F. and to 895 F. for compositions G and H containing the 0.8% of the chlorinated selenide, respectively.

In each of the Examples 3 to 11 above, a substantial improvement in autoignition temperature, and corresponding reduction in flammability is obtained, by incorporating the aryl selenides of the invention into the various functional fluids and blends thereof set forth in the examples, and such reduction in flammability is obtained without reducing the high temperature thermal stability of the functional fluid and without any increase in low temperature viscosity of the fluid, employing selected 10 selenium compounds having relatively good solubility in such fluids and hence high effectiveness therein, and which are free from toxicity and relatively odor-free.

From the foregoing, it is seen that the invention provides novel functional fluid compositions containing certain organo-selenium compounds which function efficiently as flame retardants or flame inhibitors in such fluids.

While we have described particular embodiments of our invention for purposes of illustration, it will be understood that various changes and modifications within the spirit of the invention can be made, and the invention is not to be taken as limited except by the scope of the appended claims.

We claim:

1. A functional fluid composition consisting essentially of a major portion of a functional fluid base stock selected from the group consisting of phosphorus esters, amides of an acid of phosphorus, diand tricarboxylic acid esters, and petroleum hydrocarbons containing carbon chains of from C to about C carbon atoms, and about 0.25 to about 5% by weight of a selenium compound having the general formulae:

SeR -Se-Se X and X X Wher X is halogen and R is alkyl of from about 1 to about 12 carbon atoms.

2. A composition as defined in claim 1, wherein said selenium compound has the general formula:

SeR

where X is halogen and R is alkyl of from about 1 to about 12 carbon atoms, there being from 1 to 3 X substituents on the phenyl nucleus.

3. A composition as defined in claim 1, where said selenium compound has the general formula:

where X is halogen, there being from 1 to 3 X substituents on each phenyl nucleus.

4. A composition as defined in claim 1, wherein said base stock is a phosphorus ester having the general formula:

where s, m and n are each an integer of 0 to 1, and not more than two of s, m and n are 0, R R and R are each a member selected from the group consisting of aryl, alkaryl, alkyl of from about 3 to about 10 carbon atoms, and alkoxyalkyl having from about 3 to about 8 carbon atoms.

5. A composition as defined in claim 4, wherein s, m and n are each 1, and said phosphorus ester is a phosphate ester, and said selenium compound being present in an amount ranging from about 0.5 to about 2% by weight of said composition.

6. A composition as defined in claim 1, said base stock comprising a petroleum hydrocarbon containing carbon chains of from C to about C carbon atoms, and said selenium compound being a member selected from the group consisting of ethyl p-chlorophenyl selenide and 4,4'-dichlorodiphenyl diselenide.

7. A functional fluid composition consisting essentially of a major portion of a functional fluid base stock which 80B S Kg and X X where X is halogen and R is alkyl of from about 1 to about 12 carbon atoms.

8. A composition as defined in claim 7, wherein said selenium compound is present in an amount ranging from about 0.5 to about 2% by weight of said composition.

9. A composition as defined in claim 7, wherein said base stock comprises a mixture of a phosphate ester selected from the group consisting of dialkyl aryl, triaryl, trialkyl and alkyl diaryl phosphates, and a dicarboxylic acid ester.

10. A composition as defined in claim 9, wherein said dicarboxylic acid ester is selected from the group consisting of the alkyl diesters of adipic and sebacic acid, containing alkyl groups of from about 4 to about 12 carbon atoms.

11. A composition as defined in claim 9, wherein said dicarboxylic acid ester is an alkyl diester of phthalic acid containing alkyl groups of from about 4 to about 12 carbon atoms.

12. A composition as defined in claim 11, wherein said mixture includes a dicarboxylic acid ester selected from the group consisting of the alkyl diesters of adipic and sebacic acid, containing alkyl groups of from about 4 to about 12 carbon atoms.

13. A composition as defined in claim 7, wherein said base stock comprises a phosphate ester selected from the group consisting of dialkyl aryl, triaryl, trialkyl and alkyl diaryl phosphates, and said selenium compound is a member selected from the group consisting of ethyl p-chlorophenyl selenide and 4,4'-dichlorodiphenyl diselenide.

14. A composition as defined in claim 13, said selenium compound being present in an amount ranging from about 0.25 to about 2% by weight of said composition.

'15. A composition as defined in claim 7, wherein said base stock comprises a mixture of a phosphate ester selected from the group consisting of dialkyl aryl, triaryl, trialkyl and alkyl diaryl phosphates and a dicarboxylic acid diester selected from the group consisting of the alkyl diesters of adipic and sebacic acid, containing alkyl groups of from about 4 to about -12 carbon atoms, and said selenium compound is a member selected from the group consisting of ethyl p-chlorophenyl selenide and 4,4-dichlorodiphenyl diselenide.

'16. A composition as defined in claim 7, said base stock comprising a mixture of a phosphate ester selected from the group consisting of dialkyl aryl, triaryl, trialkyl, and alkyl diaryl phosphates, and an alkyl diester of phthalic acid containing alkyl groups of from about 4 to about 12 carbon atoms, and said selenium compound being a member selected from the group consisting of ethyl 12 p-chlorophenyl selenide and 4,4-dichlorodiphenyl diselenide.

17. A composition as defined in claim 16, wherein said mixture includes a dicarboxylic acid ester selected from the group consisting of the alkyl diesters of adipic and sebacic acid, containing alkyl groups of from about 4 to about 12 carbon atoms.

'18. A composition as defined in claim 7, said base stock comprising a member selected from the group consisting of di-n-butyl phenyl phosphate, tri-n-butyl phosphate an d tricresyl phosphate, and mixtures thereof, and said selenium compound is a member selected from the group consisting of ethyl p-chlorophenyl selenide, and 4,4'-dichlorodiphenyl diselenide, said selenium compound being present in an amount ranging from about 0.5 to about 2% by weight of said composition.

19. A composition as defined in claim 18, said base stock comprising a mixture of tri-n-butyl phosphate and tricresyl phosphate.

20. A composition as defined in claim 18, said base stock including a member selected from the group consisting of diisodecyl adipate and diisodecyl phthalate, and mixtures thereof.

21. A composition as defined in claim 18, said base stock including a mixture of di-isodecyl phthalate and diisodecyl adipate.

22. A composition as defined in claim 18, said base stock being a mixture of tri-n-butyl phosphate, diisodecyl adipate and diisodecyl phthalate.

23. A composition as defined in claim 20, said base stock comprising a mixture of tri-n-butyl phosphate, di-nbutyl phenyl phosphate and diisodecyl adipate.

24. A composition as defined in claim 1, wherein said base stock comprises a mixture of a dialkyl phthalate and a member selected from the group consisting of a dialkyl adipate and a dialkyl sebacate, and said selenium compound is a member selected from the group consisting of ethyl p-chlorophenyl selenide and 4,4-dichlorodiphenyl diselenide.

25. The composition as defined in claim 6, said petroleum hydrocarbon containing carbon chains of from C to about C and said selenium compound being present in an amount ranging from about 0.5 to about 2% by weight of said composition.

References Cited UNITED STATES PATENTS 6/ 1949 Denison et al 252-45 1/1961 Bolt et a1. 252-45 X OTHER REFERENCES MAYER WEIN'BLATT, Primary Examiner H. A. PITLICK, Assistant Examiner US. Cl. X.R.