US3795619A - Fire-resistant functional fluid compositions - Google Patents

Abstract

PRODUCTION OF FUNCTIONAL FLUIDS PARTICULARLY AIRCRAFT HYDRAULIC FLUIDS, OF IMPROVED FIRE RESISTANCE, AND ALSO REDUCED TENDENCY OF CORRODE METALS, COMPRISING (1) A FUNCTIONAL FLUID BASE STOCK, SUCH AS A PHOSPHATE ESTER, E.G., TRIN-BUTYL PHENYL PHOSPHATE, OR MIXTURES OF SUCH BASE STOCKS, SUCH AS A MIXTURE OF TR-N-BUTLY PHOSPHATE AND TRICRESYL PHOSPHATE, (2) A SMALL AMOUNT OF A SELENOPHENE OR A TELLUROPHENE COMPOUND, PREFERABLY A CHLORINATED SELENOPHENE OR A CHLORINATED TELLUROPHENE, E.G. TETRACHLOROSELENOPHENE OR TETRACHLOROTELLUROPHENE, AND (3) A SMALL AMOUNT OF A TERTIARY ORGANIC PHOSPHINE, E.G. TRIPHENYL PHOSPHINE.

Description

United States Patent 3,795,619 FIRE-RESISTANT FUNCTIONAL FLUID COMPOSITIONS 1 Martin B. Sheratte, Reseda, Califi, assignor to McDonnell Douglas Corporation, Santa Monica, Calif. No Drawing. Filed July 26, 1971, Ser. No. 166,312

Int. Cl. C09k 3/00 US. Cl. 252-78 23 Claims ABSTRACT OF THE DISCLOSURE This invention relates to functional fluid compositions having improved fire resistance and is particularly directed to compositions comprising certain functional fluids and an additive amount suflicient to improve fire resistance, of certain selenium or tellurium compounds, and an additive amount of certain phosphine compounds suflicient to substantially reduce metal corrosion, e.g. copper, iron or cadmium corrosion, by such functional fluids containing said selenium or tellurium 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 fluids, 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 resistance.

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 temperatures of use. Further, it is of importance that such fluids be compatible with and not adversely affect or corrode to any significant extent materials including metals of pumps and of hydraulic system components, and non-metals such as elastomeric seals of the hydraulic system in which the fluidis 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 of materials at high temperature.

While many functional and hydraulic fluid compositions have been developed having most 'of the aforemenice.

tioned'required properties, many of these compositions donot 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 andhydraulic fluids to the range of about 800 to about 1,000 1 As described and claimed in copending application Ser. No. 155,267, of Robert S. McCord, Donald H. Nail, and Martin'-B.-Sheratte, filed June 21, 1971, now Pat. No. 3,730,898, 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 or tellurium compounds, in the form of certain selenophenes and tellurophenes, especially chlorinated selenophenes and tellurophenes.

As pointed out in the above copending application, the selenophenes' and tellurophenes, and particularly the chlorinated sellenophenes and tellurophenes described therein, 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, do not have an objectionable odor, and have suflicient solubility in most functional and hydraulic fluids to effectively function as flame inhibitors. In addition, the selenophenes and tellurophenes, particularly the chlorinated selenophene and tellurophene derivatives employed according to the above application 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.

Many functional fluids, e.g. phosphate esters such as tri-n-butyl phosphate, di-n-butyl phenyl phosphate and tricresyl phosphate, and mixtures of functional fluid base stocks, such as a mixture of tri-n-butyl phosphate and tricresyl phosphate, tend to corrode certain metals such as iron, cadmium, and copper and its alloys such as bronze, which are often present in components such as pumps, valves and the like, of hydraulic systems in which such fluids are employed, especially when such metals or metal components are exposed to such fluids at elevated temperatures. Although incorporation of the selenophenes or tellurophenes such as the chlorinated selenophenes or chlorinated tellurophenes of the above copending application, into such fluids in certain instances tends to reduce to some extent such metal attack, as compared to the same fluid in the absence of such selenophenes or tellurophenes, the corrosive attack of such fluids containing such selenide or telluride additive in concentrations required for adequate flammability protection is still often substantial and undesirable. Moreover, the incorporation of the above selenophene or tellurophene additive into such fluids in suitable operative concentration and under certain conditions may tend to increase the corrosive attack of the fluid on certain metals, such as iron and its alloys as compared to the corrosive elfect of the same functional fluid in the absence of such additive.

While the addition of a metal deactivator such as benzotriazole into the above functional fluids containing a selenophene or tellurophene, e.g. chlorinated selenophene or chlorinated tellurophene of the above application, may

I reduce such metal attack, the presence of such deactivators results in the formation of deposits in the functional selenophene or tellurophene additive.

It has now been found that by incorporation of a small amount of a tertiary organic phosphine, e.g. in the form of a triaryl phosphine such as triphenyl phosphine, into a functional fluid or hydraulic fluid composition, e.g. one containing a phosphate ester or a mixture of phosphate esters as base stock, and also containing the above-noted selenophenes or tellurophenes, e.g. a chlorinated selenophene or tellurophene, to enhance [fire resistance, the presence of the phosphine usually materially reduces or substantially eliminates the corrosive effect of the fluid containing such additive selenium or tellurium compounds, Without formation of any undesirable deposits, and Without adversely afiecting any of the important characteristics and properties of the functional or hydraulic fluid, particularly for use as an aircraft hydraulic fluid, and without adversely affecting the function of the selenium or tellurium compound for improving the fire resistance or for increasing autoignition temperature of such functional or hydraulic fluid compositions.

As a matter of fact, it has been found that when the organic phosphine additive, e.g. triphenyl phosphine, is used in combination with the above-noted selenophene or tellurophene additive in a functional fluid, the phosphine additive exhibits two important phenomena, namely, it affords substantially complete protection to metal parts, such as copper and its alloys, iron and cadmium, against metal attack by such fluid containing the above-noted selenophenes or tellurophenes, and it interacts in a synergistic manner with the above selenophene or tellurophene additive, so that the amount of such additive required to provide a given improvement in fire resistance or a given increase in autoignition temperature, is substantially reduced over the amount of selenophene or tellurophene additive required in the absence of the tertiary organic phosphine. In addition, the reduced concentration in the fluid of the selenophene or tellurophene additive compound thus permitted by the presence of the phosphine to obtain a given degree of fire resistance also tends to reduce any corrosive effect of the selenophene or tellurophene compound and at the same time reduces the overall cost of the fluid.

Effective selenium and tellurium compounds for use as additive in functional or hydraulic fluids to reduce flammability and increase autoignition temperature of the fluid, as described in the above copending application, are the S-membered unsaturated selenium and tellurium heterocyclic compounds having the general formula:

where X is Se or Te, and Y is H or halogen such as C1 or Br.

Thus, specific examples of selenium and tellurium compounds within the above definition which can be employed include unsubstituted selenophene and tellurophene, wherein all of the Ys above are hydrogen.

The halogenated selenophenes and tellurophenes, particularly the chlorinated derivatives wherein at least one Y is halogen, e.g. chlorine or bromine, including both the partially halogenated and especially the completely halogenated, selenophenes and tellurophenes, and wherein 1, 2, 3 or all 4 Ys are halogen such as chlorine or bromine, are particularly effective functional fluid additives, according to the above application. Also, halogen substituted selenophenes and tellurophenes can be employed having mixed halogen substituents, e.g., 1 or more of the Ys can be chlorine and one or more of the Ys in the same compound can be bromine. Further, mixtures of the above-defined selen phenes, or of the abovedefined tellurophenes, or a combination of selenophenes and tellurophenes can be employed.

Specific examples of the above-defined selenophenes and tellurophenes which can be employed are as follows:

( l) selenophene (2) tellurophene (3 2-chloroselenophene (4) 3-chloroselenophene (5) 2,3-dichloroselenophene (6) 2,5-dichloroselenophene (7) 2,3,4-trichloroselenophene (8) 2,3,S-trichloroselenophene (9) tetrachloroselenophene 10) 2-chloro 3-bromoselenophene (1 1 2,3-dichloro 4-bromoselenophene Specific examples of halogenated tellurophenes correspond to those of Compounds 3 to 11 above, wherein selenium is replaced by tellurium.

Specific examples of brominated selenophenes are those corresponding to Compounds 3 to 9 above, wherein chlorine in each of such compounds is replaced by bromine, and specific examples of brominated tellurophenes correspond to the above specific brominated selenophenes, wherein selenium is replaced by tellurium.

Selenophene and tellurophene compounds which have been found especially elfective and which are preferred according to the above copending application are tetrachloroselenophene, Compound 9 above, and its tellurium analogue, tetrachlorotellurophene.

Selenophene, tellurophene and their halogenated derivatives employed as additives for functional fluids as described in the above copending application can be prepared in known manner. Thus, selenophene can be prepared by reacting selenium with acetylene under suitable reaction conditions, and tellurophene can be prepared in a similar manner employing tellurium.

Partially chlorinated derivatives of selenophene and tellurophene can be prepared in known manner by re acting selenophene or tellurophene with chlorine gas under suitable conditions and controls to obtain the de sired degree of partial chlorination, e.g., substitution by 1, 2 or 3 chlorine atoms. Partially brominated derivatives of selenophene and tellurophene can he prepared in a similar manner employing bromine in place of chlorine. However, this procedure cannot be employed for preparing the completely halogenated, that is the tetrachlorinated or tetrabrorninated derivatives of selenophene and tellurophene.

Thus, tetrachloroselenophene can be prepared by reacting substantially equimolar portions of selenium powder and hexachlorobutadiene, under heat and pressure, and tetrachlorotellurophene is prepared in a similar manner, but employing tellurium powder.

Tetrabromoselenophene and tetrabromotellurophene can be prepared in a manner similar to that noted above for tetrachloroselenophene and tetrachlorotellurophene, employing hexabromobutadiene in place of hexachlorobutadiene.

Examples of preparation of tetrachloroselenophene and tetrachlorotellurophene are described in the above copending application, and such disclosure is incorporated herein by reference.

The tertiary organic phosphine employed as additives in combination with the above-described selenophene and tellurophene additives according to the invention, are phosphines having the general formula:

where R,,, R and R each can be aryl such as phenyl and naphthyl, and 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. R,,, R and-R can be the'same or diiferent. Specific examples of the above tertiary organic phosphine additives which can be employed according to the invention are the preferred triphenyl phosphine and dicresyl phenyl phosphine, additional examples of suitable phosphines according to the invention being cresyl diphenyl phosphine, tricresyl phosphine, alpha-naphthyl-diphenyl phosphine and tris-(3,4-dimethylphenyl)phosphine.

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:

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-hexy1, 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. i

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, trial-kyl 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 combination of selenophenes or' tellurophenes, especially chlorinated selenophenes or telhirophenes, and phosphine additives 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 npropyl, n-butyl, n-amyLand n-hexyl,-particularly tri-nbutyl phosphate, tri(2-ethyl hexyl) 'phosphate and triisononyl phosphate, the straight chain alkyl groups preferaibly 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-Inethyl heptyl diphenyl, 2- ethylhexyl diphenyl, butyl phenyl cresyl, amyl phenyl xylyl, and butyl dicrcsyl phosphates.

Functional fluid base stocks according to the invention also include phosphonate and phosphinate esters having alkyl and aryl groups corresponding to those defined above with respect to the phosphate 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-npentyl phosphinate, p-methoxyphenyl-di-n-butyl ph0sphinate, tert-butylphenyl-di-nbutyl phosphinate. Examples of phosphonate esters to which the invention is applicable include aliphatic phosphonates such as an 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 alkyl aryl phosphonate, for example, di-octyl phenyl phosphonate, di(namyl) phenyl phosphonate, di(n-'butyl) phenyl phosphonate, phenyl butyl hexane phosphonate and butyl bisbenzene phosphonate.

Another class of phosphorus-containing compounds in which the combination of selenophene or tellurophene, and phosphine additives of the invention can be employed 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-cresylp-cresyl-N,N-dimethylphosphoroamidate, di-m-cresyl-N,N-dirnethylphosphoroamidate, dim-cresyl-N,N-dimethylphosphoro amidate, phenyl-N,N-dimethyl-N',N'-dimethylphosphorodiarnidate, N-methyl-N-butyl-N-N"-tetramethylphosphorotriamidate, N,N'-di-npropyl-N"-dimethylphosphorotriamidate.

Another class of functional fluid base stocks whose autoignition temperature and corrosivity can be improved by incorporation of the selenophene or tellurophene, and whose corrosive properties can be reduced by the addition of the phosphine additives 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 2-ethylhexyl, dioctyl, dinonyl, didecyl and diisodecyl adipate, and the corresponding seb-acates. 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, dinonyl phthalate, didecyl phthalate, and diisodecyl phthalate. r

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 12 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, tri-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 invention principles are applicable 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 MIL- H-56O6B, 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 diisodecyl 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 diisodecyl adipate and diisodecyl 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 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 to about 10%, generally about 2 to about 10%, by weight of the composition. Examples of the latter are polyalkyl acrylates and methacrylates, the polyalkyl methacrylates generally being preferred, and in which the alkyl groups may contain from about 4 to about 12 carbon atoms, either straight or branched chain, and having an average molecular weight ranging from about 2,000 to about 15,000. Specific examples of such viscosity index improvers are polybutyl methacrylate and poly n-hexyl acrylate, having an average molecular weight between about 2,000 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, it is usually desirable to employ only a small amount of the selenophene or tellurophene additive 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 selenophene or tellurophene additive, preferably from about 0.5 to about 2% of such additive, in the functional fluid base stock, based on the weight of the composition. It has been found that an optimum amount of such selenophene or tellurophene additive ranges from about 0.8 to about 2% by weight of the composition. However, as previously noted, and demonstrated hereinafter, the amount of the latter additive employed can be reduced a substantial proportion as a result of the presence of the phosphine additive, and still obtain a comparable reduction in flammability.

The amount of tertiary organic phosphine additive incorporated in the functional fluid base stock together with the small amount of the selenophene or tellurophene additive, can range from about 0.1 to about 5% by weight of the composition. In a preferred practice, however, there is employed an amount of such phosphine ranging from about 0.1 to about 2% by weight of the composition. As previously noted, this small amount of the abovedefined phosphine incorporated with the selenophene or tellurophene additive in the functional fluid base stock, particularly phosphate ester, eflectively minimizes or eliminates corrosion by the fluid, of copper and its alloys such as bronze, iron and steel, cadmium such as cadmium plate, and also aluminum and its alloys, and titanium and its alloys. It is found undesirable, however, to employ the above-noted phosphine additive when the functional fluid is to be contacted with magnesium and its alloys at temperatures above 150 F.

The above-noted tertiary organic phosphines e.g. triphenyl phosphine and dicresyl phenyl phosphine, are generally prepared by preparation of the appropriate Grignard reagent, such as R MgCl, e.g. C H MgCl, where R,, has the values defined above, that is aryl or alkaryl, and reaction of such aryl or alkaryl magnesium halide with PCl to produce the corresponding tertiary organic phosphine, e.g. triaryl phosphine such as triphenyl phosphine. Where one or more of R R and R as defined above are different, a mixture of the appropriate aryl and/or alkaryl magnesium halide compounds in appropriate molar proportion is employed to produce the mixed tertiary organic phosphine. Thus for example, triphenyl phosphine can be produced by reaction of phenylmagnesium chloride with PCl in ether, as follows:

Triphenyl phosphine is a white solid melting at 86 C. It has a slight phosphine odor, which is completely masked when dissolved in tributyl phosphate.

Similarly, dicresyl phenyl phosphine can be prepared by reacting two mols of cresyl magnesium chloride and one mol of phenyl magnesium chloride, with one mol of PCI The following are examples illustrating practice of the invention by incorporation of selenophene or tellurophene, and phosphine additives into functional fluid base stocks according to the invention, all percentages being in terms of percent by weight.

EXAMPLE 1 To one portion of a functional fluid blend comprising about tri-n-butyl phosphate, about 11% tricresyl phosphate, and a small amount of polybutyl methacrylate viscosity index improver, is added 1.3% tetrachloroselenophene, such fluid designated fluid I, and to another portion of the same functional fluid blend is added 1.3% tetrachloroselenophene and 0.5% triphenyl phosphine, the latter fluid blend being designated fluid II.

The above two fluids I and II, together with a control of the above fluid blend containing no selenophene or phosphine additive, are subjected to a closed oxidationcorrosion test at 325 F. on iron and cadmium plate, placing both of these metal samples in each of the above three fluids, and the corrosive effect of the respective fluids on each of these respective metals is measured over a period of 26 hours by determining the weight changes in mg./cm. on each of the respective metals at the end of this period, and the acid number of the respective fluids following the above 26 hour test at 325 F. is also determined.

i The results of these tests are noted ind-able 1 below.

From Table 1 above it is noted that addition of the tetrachloroselenophene additive to the functional fluid, forming fluid I, increases the corrosive effect of the fluid on iron at the end of this 26 hour test period to 0.47 mg./cm. from essentially no corrosivity for the control, but upon the addition of 0.5% triphenyl phosphine to the fluid containing the selenide additive, forming fluid II, the corrosive eifect of the fluid containing the tetrachloroselenophene additive on the iron is essentially eliminated.

In the case of cadmium plate, it is noted that in this 26 hour test, fluid I containing the above tetrachloroselenophene additive has a slightly corrosive effect corresponding to 0.02 mg./cm. as compared to mg./cm. for the control, whereas fluid II containing 0.5% triphenyl phosphine in addition to the selenide, eliminates the slightly corrosive etfect of the tetrachloroselenophene-containing fluid on the cadmium plate, as indicated by the value of 0 for the weight change in this test as noted in the above table.

Further, it is noted that the acid number of the fluid I containing only the tetrachloroselenophene additive at the end of these tests on iron and cadmium plate is 5.80, substantially higher than the 3.80 acid number for the control, whereas the acid number for the fluid 11 containing 0.5% triphenyl phosphine in combination with 1.3% of the tetrachloroselenophene additive is substantially reduced to only 1.95.

EXAMPLE 2 The tests of Example 1 are repeated on bronzeas well as on iron and cadmium plate, and the period of exposure of the respective fluids on each of these three metals is extended to 30 hours, and the triphenyl phosphine of fluid II is replaced by dicresyl phenyl phosphine.

The results of these tests are noted in Table 2 below.

Table 2 above clearly shows the dramatic reduction in corrosivity of the fluid containing tetrachloroselenophene, upon the addition of 0.5% dicresyl phenyl phosphine to such fluid, on each of the bronze, iron and cadmium plate samples, in these 30 hour tests.

In the case of iron and cadmium plate, it is noted that the corrosivity of the fluid I containing tetrachloroselenophene, of 5.6 and 0.70 mg./cm. is completely eliminated upon the addition of dicresyl phenyl phosphine to form fluid II, and that in the case of bronze, the corrosivity of fluid II is reduced to only 0.04 mg./cm. upon addition of the phosphine additive, from 0.12 mg./ :m. for the fluid I containing only the tetrachloroselenophene additive.

Also, the acid number of 6.04 for fluid I containing only the tetrachloroselenophene additive at the end of these tests, is markedly reduced to only 1.95 in the case of the fluid containing the phosphine additive.

The results of the tests in Examples 1 and 2 above as demonstrated in Tables 1 and 2, show that the presence of triphenyl phosphine or dicresyl phenyl phosphine, in combination with the additive tetrachloroselenophene, in the functional fluid of such examples reduces the corrosive attack of the fluid on bronze, iron and cadmium, generally, as compared tothe control fluid, and particularly as compared to the fluid containing only the tetrachloroselenophene, and also that the fluid containing the phosphine additive, as indicated by its relatively low acid number at the end of these tests, prevents acid build-up and prevents the formation of deposits in the fluid as compared to the control fluid and also the fluid containing only the tetrachloroselenophene.

EXAMPLE 3 To aliquot portions of a functional fluid blend consisting of 50% diisodecyl adipate and 50% dibutyl phenyl phosphate, and containing 1.3% of the additive tetrachloroselenophene, is added, respectively, 0.2%, 0.5% and 1.0% of the phosphine additive dicresyl phenyl phosphine.

The resulting three fluids, together with a control of such fluid blend containing the selenophene additive but nophosphine additive, are tested for the effect of the presence of the phosphine additive on reduction of corrosion of the fluid containing the additive tetrachloroselenophene on bronze, iron and cadmium plate in a 26 hour test at 325 F., according to the procedure of Example 1, and also obtaining the acid number of the respective fluids following the corrosion test.

The results of this test are noted in Table 3 below.

TAPLE 3 Weight changes (mg/cm!) Dicresyl phenyl Cadmium Acid phosphine, percent Bronze Iron plate number It will be seen from Table 3 above that increasing the amounts of dicresyl phenyl phosphine from 0.2% to 1.0%, particularly in the case of bronze and iron, substantially reducesthe corrosive effect of the fluid containing the tetrachloroselenophene additive on both the bronze and iron, reducing the amount of corrosion on bronze from 0.15 mg./cm. for the control fluid to 0.07 and 0.02 for the fluids containing 0.5 and 1% of the phosphine, and on iron from 0.51 mg./cm. for the control, to 0.01 and 0 corrosion for the fluids containing 0.5 and 1% phosphine additive, respectively. On cadmium plate, corrosion is reduced from 0.07 mg./cm. for the control to 0.01 for the fluid containing 1.0% of the phosphine.

Further, it-is noted that the acid number is substantially reduced from 5.97 for the control following the above test, down to 2.03 and 1.98, respectively, for the fluids containing 0.5 and 1.0% of the phosphine additive.

EXAMPLE 4 The test of Example 3 above is repeated, except employing in place of the functional fluid blend of Example 3, the functional fluid blend of Example 1.

Substantially similar results are obtained with respect to reduction of corrosion on bronze iron and cadmium plate, of the respective fluids containing 0.2%, 0.5% and 1.0% of dicresyl phenyl: phosphine, together with tetrachloroselenophene, as in the case ofthe corresponding fluids in Example 3, containing 0.2%, 0.5% and 1.0% of dicresyl phenyl phosphine.

EXAMPLE 5 The tests of Examples 1 to 4 are repeated, except em- 'ploying in'place'of tetrachloroselenophen e, the tellurium analogue tetrachlorotellurophene.

Reduction in corrosivity and acid number results obtainedare comparable to the corresponding results of EX- amples l to 4, for the fluids containing tetrachlorotellurophene together'with the phosphine additive.

1 1 EXAMPLE 6 The procedures of Examples 1 and 2 are repeated, employing respectively each of the selenophene Compounds 3, 5 and 7 above, and their tellurophene analogues, in place of tetrachloroselenophene, each such additive being employed in an amount of 0.8% by weight in the respective portions of the functional fluid 'blend.

Reduction in corrosivity and acid number results comparable to those of Examples 1 and 2 are obtained for the fluids containing the respective selenophene and tellurophene additives, together with the phosphine additive.

EXAMPLE 7 To three aliquot portions of the functional fluid blend containing about 80% tri-n-butyl phosphate, about 11% tricresyl phosphate, and a small amount of polybutyl methacrylate viscosity index improver, is added, respectively, 0.9% of tetrachloroselenophene, 0.3% of tetrachloroselenophene and a combination of 0.3% tetrachloroselenophene and 1.0% triphenyl phosphine. The autoignition temperature (AIT) of the resulting fluid compositions is obtained, the autoignition temperature of such functional fluid compositions being determined in accordance with standard methods of test for autoignition temperature in accordance with ASTM D 2155 procedure.

The results of such tests are noted in Table 4 below, in which the terms selenophene and phosphine designate the above-noted specific selenophene and phosphine additives, respectively.

From the table above, it is seen that the addition of 0.3% of the selenophene additive in the absence of phosphine, increases the AIT of the control fluid containing no selenophene from an AIT of 730 F., to 800 F., and when incorporating 0.9% of the selenophene in the absence of phosphine, the AIT is increased to 850 F. On the other hand, by incorporating with the fluid containing 0.3% of the selenophene, 1.0% of the phosphine additive, the resulting fluid has an AIT of 840 R, which is 40 F. higher than the AIT value for the fluid containing 0.3% tetrachloroselenophene in the absence of phosphine, and closely matching the AIT for the fluid containing 0.9% of the selenophene and in the absence of any phosphine.

The above Table 4 illustrates the synergistic effect of the phosphine additive on the fluid containing the selenophene, in substantially increasing the autoignition temperature and correspondingly reducing flammability over a fluid containing a comparable amount of the selenophene only, thus improving the AIT and performance of the fluid, while reducing the concentration of selenophene compound required, and at the same time the phosphine additive serves to protect the above-noted metals such as copper, iron and cadmium, against corrosive attack by the fluids containing the selenophene additives, as demonstrated in Examples 1 and 2 above.

EXAMPLE 8 The test procedure of Example 1 is reepated, but empolying as the functional fluid a blend of 56% tri-n-butyl phosphate, 35% diisodecyl adipate and 5% poly-n-hexyl acrylate having an average molecular Weight of about 2,000 as viscosity index improver, with one portion of the fluid containing 0.8% of tetrachloroselenophene, and the other portion containing such tetrachloroselenophene and also 1.0% of triphenyl phosphine.

The corrosivity of the fluid containing only the 0.8% of the tetrachloroselenophene on the metals in Example 1, and the acid number of such fluid containing only this tetrachloro selenophene, are substantially reduced by incorporation of the 1.0% triphenyl phosphine, comparable to the results obtained in Example 1.

EXAMPLE 9 The test procedure of Example 1 is repeated but employing as the functional fluid a blend of 39% tri-n-butyl phosphate, 47% diisodecyl adipate, 10% diisodecyl phthalate, and a small amount of oxidation inhibitor, with one portion of the fluid containing 1.3% of tetrachloroselenophene, and another portion containing 1.3% of tetrachloroselenophene together with 0.5 of triphenyl phos phine.

The presence of the 0.5% of triphenyl phosphine in the above-noted fluid blend containing the selenophene additive substantially reduces corrosivity of the fluid on the metals tested, and the acid number is also substantially reduced, as compared to the fluid containing only the selenophene additive, similar to the results obtained in Example 1.

EXAMPLE 10 The test procedure of Example 2 is repeated employing as the functional fluid tri-n-butyl phosphate instead of the blend of Example 2.

Reduction in corrosivity and acid number of the resulting fluid by addition of dicresyl phenyl phosphine to the fluid containing the additive tetrachloroselenophene, are comparable to the results obtained in Example 2.

EXAMPLE 11 The procedure of Example 1 is repeated employing in place of the functional fluid blend in Example 1, the following fluids:

(a) a blend of 70% diisodecyl adipate and 30% tri-nbutyl phosphate (b) a blend of 50% diisodecyl adipate, 30% tri-n-butyl phosphate and 20% dibutyl phenyl phosphate (c) a blend of 50% diisodecyl adipate, 40% tri-n-butyl phosphate, and 10% tri-isodecyl-tri-mellitate (d) a blend of 50% tri-n-butyl phosphate and 50% diisodecyl phthalate (e) a red petroleum hydrocarbon liquid containing hydrocarbon chains ranging from C to C (MILH- 5606-B) (f) phenyl-N-methyl-N-n-butyl N methyl-N'-n-butyl phosphorodiamidate.

In each of the above six fluids (a), (b), (c), (d), (e) and (f) a substantial reduction in corrosivity of the respective fluids on iron and cadmium plate, and a substantial reduction of the acid number of the respective fluids is obtained, by incorporation of the additive triphenyl phosphine, in each of the above fluids also containing the selenophene additive tetrachloroselenophene.

EXAMPLE 12 The procedure of Example 2 is repeated employing in place of dicresyl phenyl phosphine the following phosphine additives:

(1) cresyl diphenyl phosphine (2) tricresyl phosphine (3) alpha-naphthyl-diphenyl phosphine (4) tris-(3,4-dimethylphenyl) phosphine.

Incorporation of the above phosphine additives (1) to (4), respectively, in the functional fluid blend of Example 2, containing the selenophene additive tetrachloroselenophene, substantially reduces corrosivity of the respective fluids on bronze, iron and cadmium plate, and the resulting fluids containing the phosphine additives (1) to (4), respectively, have substantially reduced acid numbers in comparison with the corresponding fluids containing only the selenophene additive and in the absence of the phosphine additive.

The properties 'of'corr'iposition A are notedbelow: 'R'esiilts 'of closed oxidation corrosionLtests at 250 F. for 1'68 -l'1'0u1sare set-forth injTablesu5 and 6.. below, the metals of Table "5 below allibeing inserted. in the same fluid Aabove inone test-andthe metals; of Table 6 all being inserted in another "portion of fluid A in another test, the acid number of the. fluid A'in each of the tests =beir'ig detefminedi aftei'the1168 hour test period.

Thefluid A Show practically complete freedom from corrosive attack on the metals of Tables 5 and 6, except :for rnagnesiumfalthough thecb'rrosion value in Table 5 ;for magnesium is wi'thin aircraft specification standards, and} and amber for ,fiuid A isobtained in .both tests deported in ngs; s urs; I

. p F. a? ashlpoint' 390 i Fgre point 400 (flash- 'ipoirihand .fire oint obtained bykstandard Cleve- Iahd opencup procedure). J Autoignition temperature (AIT)E 870F. (obtained by procedure) =R'ubbe r compatibility+rubber swell .and hardness change in 1 week immersion ofEI R (ethylenepropylene rub- :ziIF-b'e'rjdfi-fluidii "at"-160 F.-:SH (change in hardness) 12 (ShoreA scale), swell 22%" Viscosity at-- 210 F. v cs. (centistokes) 3.8 1 100 F. CS 12.3 40 F. cs 600 Density at 77 F. gm./ml 0.9.66

The above values for flash point, fire point, and AIT indicate generally improved fire and flammability resistance of fluid A, and the above change in hardness and swell values for EPR in fluid A shows satisfactory performance within aircraft specification standards for contact of fluid A with EPR, an important rubber used Widely in the manufacture of seals for aircraft hydraulic systems. The above viscosity values show operability and pump-' ability of fluid A both at high operating temperatures of 210? F. and atlow temperatures of 40 F., and below, and the above density value of 0.966 of fluid A shows low density of the fluid, an important economic criterion especially for use of the fluid in the hydraulic systems of modern large commercial aircraft.

In accordance with the invention, by incorporation of the above-defined tertiary organic phosphine additive in a functional fluid, such as a phosphate ester, containing a selenophene or tellurophene additive as defined above, a substantial improvement in autoignition temperature and corresponding reduction in flammability is obtained as a result of the presence of the selenophene or tellurophene;

additive while at the same time substantially reducing the corrosive effect of the fluid containing the selenophene or tellurophene additive on various metals employed as components in hydraulic fluid systems, including pumps, valves and the like, without adversely afiecting any of the advantageous characteristics of the functional fluid, e.g. without reducing the high temperature thermal stability of the functional fluid and without any increase in low temperature viscosity of the fl-uid.

From the foregoing, it is seen that the invention provides novel functional fluid compositions containing a combination of certain organo-selenium or organo-tellurium compounds, together with certain tertiary organic phosphines, which have improved fire resistance and reduced corrosivity on certain metals.

While I have described particular embodiments of my 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.

" I claim:

1. A functional fluid composition consisting essentially of 1) 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; (2) a small amount of a selenium or tellurium compound suflicient to increase the autoignition temperature of said base stock, said compound having the formula:

where X is a member selected from the group consisting of Se and Te, and Y is a member selected from the group consisting of H and a halogen, and (3) a small corrosion inhibiting amount of a tertiary organic phosphine having the formula: v

PgR 7,

where R,,, R and R are each armemberselected from the group consisting of aryl and alkaryl, containing from :6 to about 8 carbon atoms.

2. A composition as defined in claim 1, saidseleuium or-tellurium compound being. present in an amount ranging from about 0.25 to about 5%, and said phosphine being present in an amount ranging from about 0.1 to about 5%, by weight of said composition. i

"3.: A composition as defined in claim 1, said-selenium or tellurium compound being present in an amount ranging from about 0.5 to about 2%, and said phosphine being present in an amount ranging from about 0.1 to about 2%, by weight of said composition.

4. A composition as defined in claim 2, wherein at least one Y of said selenium or tellurium compound is halogen.

5. A composition as defined in claim 4, wherein all 4 Ys of said selenium or tellurium compound are halogen.

6. A composition as defined in claim 2, wherein X of said selenium or tellurium compound is selenium and all 4 Ys of said compound are halogen selected from the group consisting of chlorine and bromine, and where R,,, R and R of said phosphine are each a member selected from the group consisting of phenyl and cresyl.

7. A composition as defined in claim 2, wherein each Y of said selenium or tellurium compound is hydrogen.

8. A composition as defined in claim 2, wherein said selenium or tellurium compound is selected from the group consisting of tetrachloroselenophene and tetrachlorotellurophene, and said phosphine is selected from the group consisting of triphenyl phosphine and dicresyl phenyl phosphine.

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

Rr-O,

Ra-O where s, m and n are each an integer of 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.

10. A composition as defined in claim 9, wherein s, m and n are each 1, and said phosphorus ester is a phosphate ester, and said selenium or tellurium compound being present in an amount ranging from about 0.25 to about 5% by weight of said composition.

11. A composition as defined in claim 2, wherein said base stock consists essentially of a phosphate ester selected from the group consisting of dialkyl aryl, triaryl, trialkyl and alkyl diaryl phosphates, said alkyl groups containing from about 3 to about carbon atoms and said aryl groups containing from 6 to 8 carbon atoms, the total number of carbon atoms in all three aryl groups in said triaryl phosphates being from 19 to 24.

12. A composition as defined in claim 8, wherein said base stock consists essentially of a phosphate ester selected from the group consisting of dialkyl aryl, triaryl, trialkyl and alkyl diaryl phosphates, said alkyl groups containing from about 3 to about 10 carbon atoms and said aryl groups containing from 6 to 8 carbon atoms, the total number of carbon atoms in all three aryl groups in said triaryl phosphates being from 19 to 24.

13. A composition as defined in claim 11, wherein said base stock additionally contains 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, and an alkyl diester of phthalic acid containing alkyl groups of from about 4 to about 12 carbon atoms.

14. A composition as defined in claim 11, wherein said mixture additionally contains an alkyl diester of phthalic acid containing alkyl groups of from about 4 to about 12 carbon atoms, and 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.

15. A composition as defined in claim 11, wherein said selenium or tellurium compound is tetrachloroselenophene, and said phosphine is triphenyl phosphine.

16. A composition as defined in claim 15, said selenium or tellurium compound being present in an amount rang- 6 ing from about 0.5 to about 2%, and said phosphine being present in an amount ranging from about 0.1 to about 2%, by weight of said composition.

17. A composition as defined in claim 13, wherein said selenium or tellurium compound is a member selected from the group consisting of tetrachloroselenophene and tetrachlorotellurophene, and said phospine is selected from the group consisting of triphenyl phosphine and dicresyl phenyl phosphine.

18. A composition as defined in claim 2, said base stock consisting essentially of a member selected from the group consisting of di-n-butyl phenyl phosphate, tri-nbutyl phosphate and tricresyl phosphate, and mixtures thereof, said selenium or tellurium compound is a member selected from the group consisting of tetrachloroselenophene and tetrachlorotellurophene, and said phosphine is selected from the group consisting of triphenyl phosphine and dicresyl phenyl phosphine.

19. A composition as defined in claim 18, said selenium or tellurium compound being tetrachloroselenophene and said phosphine being triphenyl phosphine.

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

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

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

23. A composition as defined in claim 18, wherein said phosphate is tri-n-butyl phosphate, and additionally containing diisodecyl adipate and diisodecyl phthalate.

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Encyclopedia of Chemical Technology, Kirk-Othmer (1965), vol. 8, p. 374.

LEON D. ROSDOL, Primary Examiner H. A. PITLICK, Assistant Examiner US. Cl. X.R. 25246.7, 389