CA2048923A1

CA2048923A1 - Oxidation inhibited fluid compositions and a process for the preparation thereof abstract of the disclosure

Info

Publication number: CA2048923A1
Application number: CA002048923A
Authority: CA
Inventors: John S. Mcconaghy Jr.
Original assignee: Monsanto Co
Current assignee: Solutia Inc
Priority date: 1990-08-30
Filing date: 1991-08-12
Publication date: 1995-05-19
Also published as: FR2718148A1; FR2718148B1; GB2280199A; DE4128892A1; GB9117208D0; GB2280199B

Abstract

OXIDATION INHIBITED FLUID COMPOSITIONS AND
A PROCESS FOR THE PREPARATION THEREOF
ABSTRACT OF THE DISCLOSURE
Fluid compositions useful to serve as oxidation inhibited functional fluids, and a process for the preparation thereof, are provided. Such fluid compositions comprise a colloidal dispersion of an aromatic ether represented by the formula

Description

892~

-1- 43-21(7857)A -OXInATION INHIBITED FLUI~ COM~ITIONS ~ND

5BACKGROUND OF THE INVE~IQ~
1. Field of the Invention This invention relates to fluid compositions and a process for the preparation of ~uch compositions.
More particularly, this invention relates to fluid 10 compositions comprising a colloidal dispersion of an ~ .
aromatic ether represented by the formula Rl-O ~ R2-o~ R3 - ~ :

wherein Rl, R2, and R3 independently are phenyl, : .
biphenyl, and terphenyl and n is an integer of from zero (O) to 5, and an oxidation inhibiting amount of an alkali metal salt of oxalic acid and a process for the - :
preparation thereof.
The fluid compositions of thi~ invention are useful in a number of applications requiring fluids .:~
resistant to oxidative and thermal degradation under use conditions of high stress (such a~ elevated temperatures of 316- C (600- F) and higher. For example, the fluid compositions are useful as atomic reactor coolants, diffusion pump fluids, damping fluid~, force transmission fluids (hydraulic fluids), ¦ h-at transfer fluids, and synthetic lubricants, particularly as jet engine lubricants.

2. Description of the Prior Art Aromatic ethers, particularly polyphenyl ethers (wherein each of R1, R2, and R3 is phenyl), and their use as functional fluid compositions are well ~'''' "," .
~'`':'' ~ ' - ' .
~' .
~''''~

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-2- 43-21(7857)A
known in the art. They are oxidatively stable to about 275- c (527' F) and resist pyrolysia to about 445- C
(833' F). However, at temperatures above their stability limits, the aromatic ethers tend to develop sludge and thlcken to a degree which adversely af~ects their high temperature performance. Therefore, a variety of additives have been proposed and disclosed in the prior art to stabilize the aromatic ethers against oxidative dsgradation and thereby extsnd their operation range.
The susceptibility of the aromatic ethers to ~-some degree of oxidative stabilization by a variety of -metals (or their oxides and carboxylates) was reported .-for polyphenyl ethers by Ravner et al, J. Chem. Eng.
15 ~9~, 8, 591-596 (1963).
U. S. Patent No. 3,245,907 discloses the stabilization of polyphenyl ethers against oxidative degradation by the incorporation therein of an organotin compound repre~ented by the formula ~ -R~-Sn-X~
and ~
- ~-.
R3-Sn-Sn-R~
- ~
wherein R i8 an alkyl, aryl, aralkyl, aryloxyaryl, ~ -biaryl, thienyl, and pyridyl group; X is R or a h~logsn, and m is an integer (whole number) of from 1 to ~.
In ~.S. Patent No. 3,290,247, polyphenyl sther compositions having improved antioxidant propsrties are disclosed and claimed. The oxidative stabilization of ''` ''.

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"' " . ' .
~.. .. .
~.'','''~.

-3- 43-21(7857)A
the polyphenyl ethers i9 achieved by incorporating therein organotin compounds represented by the formula (I) FnSn~XR')~ -wherein n is an integer of from 2 to 3, m is an integer of from 1 to 2, and the sum of m + n is 4; R is an alkyl group ~referred to in the reference as a radical) of from 1 to 12 carbon atoms, benzenoid hydrocarbon groups which are free of olefinic and acetylenic unsaturation and contains from 6 to 12 carbon atoms, and aryloxyaryl groups of from 12 to 24 carbon atoms, and such groups having halogen substituted at the -benzenoid nucleus; R' is R, paraffinic and lS haloparaffinic acyl groups of from 2 to 12 carbon ~ .
atoms, the group .~ ~
-N Z
~... .. J

wherein Z is a necessary member to complete a saturated heterocyclic group of from 6 to 10 members, the groups -SnR3 and -arylene-0-SnR3; and X is a chalcogen element 25 having an atomic weight of less than 33, and those -:
represented by the formula R
_ -Y-X-~n-X- _ _ _ Y
wherein Y is an arylene group of from 6 to 12 carbon atoms, an arylenealkylenearylene group and ~` ``';:.
' :::

:
~:~
., ~ 8923 -4- 43-21(7857)A
alkylenearylenealkylene group having from 1 to 4 carbon atoms in the alkylene group and from 6 to 12 carbon atoms in the arylene radical, R and X are as previ-ously defined, and y is a number of from 10 to lO00 (to denote the degree of polymerization).
U.S. Patent No. 3,492,229 discloses, inter , aromatic ether compositions which exhibit improved oxidation resistance. Such compositions are ~ -provided by incorporation of organic salts of alkali metals, antimony, bismuth, and lanthanum into the aromatic ether basestock. Such compositions reportedly are useful as ~et engine lubricants, heat transfer -~ ~
fluids and hydraulic fluids. -Although these prior art aromatic ether compositions generally exhibit increased oxidation stability over aromatic ether~ themselves, they, in general, are limited in their application usefulness as functional fluids and engine lubricants under high stress conditions extant in present-day high stress engines -- jet engines, for example -- as well as engines currently under development for the next generation of ~et engines. For example, as the speed and ~ltitud~ of operation oP jet engine-containing -vehicles increases, lubrication problems also have increased because of increased operating temperatures and higher bear~ng pressures resultinq from the increa~ed thrust needed to obtain and maintain high s~ ~ds and altitudes. And as the service conditions encountered become increasingly severe, the useful life 30 of the functional fluid is shortened, primarily due to -their deficiency in oxidative stability above about 275- C (550- F). In general, as operating requirements --of a ~et engine are increased, engine temperatures :. , -~'``'``"'~'~ ".
,~
~ . . , `` 2n48923 -5- 43-21(7857)A
increase and oil temperatures in the range of 316- C
(600' F) and higher are encountered. Accordingly, research efforts are continually being made to define new or improved fluid compositions, and processes o~
making new and old fluid compositions, particularly aromatic ether compositions, and most particularly polyphenyl ether compo~itions, which exhibit increased oxidative stability and concomitantly are suitable for use as functional ~luids under use condit~on~ o~ high stress. The discovery of the fluid compositions of the instant invention, and the process for the preparation thereof, therefore, is believed to be a decided advance in the functional fluid art.
SUMMARY OF THE INVENTION
lS This invention i8 directed to fluid compositions having increased oxidative stability under use conditions of high stre6s (such as elevated temperatures of 316' C ~600- F) and higher) and a process for the preparation of such fluid compoeitions.
Accordingly, the primary ob~ect of this invention is to provide fluid compositions having increased resistance --to oxidative degradation under use conditions of high stress.
It i~ another primary object of this invention to provide a process for the preparation of oxidation inhibited rluid compositions having increased rosistance to oxidative degradation under use condition~ of high stress.
These and other objects, aspects, and advantage~ of the instant invention will become apparent to thosQ skilled in the art from the accompanying description and claims.

, . . .

.
~'' ' 4~923 -6- 43-21(7857)A
The above primary ob~ct of providing ~ ~ -oxidation inhibited fluid compositions, as well as ~ ~ .
other related ob~ects, are achieved by fluid compositions which comprise a colloidal dispersion of:
(a) an aromatic ether represented by the : :
formula :

Rl-O--~- R2-o--~ R3 10 wherein Rl, R2, and R3 independently are phenyl, -biphenyl, and terphenyl and n is an integer from zero (Q) to 5, and : - .
(b) an oxidation inhibiting amount of an alkali metal salt of oxalic acid, the fluid composition being characterized by being transparent when sub~ected to visual inspection with white light ~hining through the fluid composition at a:.
180- angle to the line of sight.
The above additional primary ob~ect of 20 providing a process for the preparation of oxidation ..
inhibited fluid compositions, as well as other related - : -ob~ects, are achieved by a procass which comprises~
(a) mixing an aromatic ether represented by :-.
ths formula R1~~~~- R2-o--~ R3 w~ rein R1, R2, and R3 independently are phenyl, ~ -.
biphenyl, and terphenyl and n is an integer from zero ~.`
30 (0) to 5, and an alXali metal precursor compound . .
convertible under alkali metal precursor compound conversion conditions into an alkali metal salt of oxalic acid, s': /. ;. .~ . ~ ' ~ ` . . .

~)4~9~

-7- 43-21(7857)A
(b) heating the aromatic ether/alkali metal precursor compound mixture from Step (a) at an elevated temperature in the presence of molecular oxygen or a molecular oxygen-containing gas and for a time effective to convert the alkali metal precursor compound into an alkali metal salt of oxalic acid and form a colloidal dispersion of the aromatic ether and an oxidation inhibiting amount of the alkali metal salt of oxalic acid, and (c) separating any noncolloidally dispersed solid material from the colloidal dlspersion to thereby recover the oxidation inhibited fluid composition, the fluid composition being characterized by being transparent when subjected to visual inspection with white light shining through the fluid composition at a 180- angle to the line of sight.
DESCRIPTION OF THE PREFERRED ENBODIMENTS
In accordance with this invention novel fluid compositions, and a process for the preparation of same, are provided which are useful as functional fluids under u~e conditions of high stress. The fluid compositions co~prise a colloidal dispersion of: -(a) an aromatic ether represented by the formula Rl~~~~-- R2-o----~R3 wherein R1, R2, and R3 independently are phenyl, biphenyl, and terphenyl and n is an integer from zero (O) to 5, and (b) an oxidation inhibiting amount of an alkali metal salt of oxalic acid, ~..~ ... ....
~''' ~ ' ~'' , .
~ .
~. '' 2~)48923 -8- 43-21(7857)A
the fluid composition being characterized by being transparent when sub~eeted to visual inspection with white light shining through the fluid eomposition at a 180- angle to the line of sight.
The oxidation inhibited ~luid compo~itions are prepared by a proeess whieh eomprises~
(a) mixing an aromatie ether represented by the formula R1-ot-- R2-~ ] n R3 wherein Rl, R2, and R3 independently are phenyl, biphenyl, and terphenyl and n is an integer from zero (0) to 5, and an alkali metal preeursor compound convertible under alkali metal preeursor eompound conversion eonditions into an alkali metal salt of oxalie aeid, (b) heating the aromatie ether/alkali metal preeursor compound mixture from Step (a) at an elevated temperature in the presence of moleeular oxygen or a moleeular oxygen-eontaining gas and for a time . -~
effective to eonvert the alkali metal precursor `.:. .
compound into an alkali metal salt of oxalie aeid and form a colloidal dispersion of the aromatic ether and~ - :
25 an oxidation inhibiting amount of the alkali metal salt - :
of oxalie aeid, and (e) separating any noncolloidally dispersed - -solid material from the colloidal dispersion to -~;
thereby reeover the oxidation inhibited fluid ~`
eomposition, the fluid co~position being characterized by being -~
transparent when subjeeted to visual inspeetion with :~

~:~

,~
.~, ...
~- ' .. -~2098923 -9- 43-21(7857)A
white light shining through the fluid composition at a 180- angle to the line of sight.
For purposes of this invention, the term "colloidal dispersion" means a system in which particles of colloidal size (roughly between 1 nanometer (nm) and 1 micron (~m) of one state [solid phase material (alkali metal salt of oxalic acid)~ are dispersed in a continuous phase of a different state [liquid phase material (aromatic ether)].
The aromatic ethers suitable for use in the instant invention are those represented by the formula R1-----~-- R2-o----~ R3 wherein Rl, R2, and R3 independently are phenyl, biphenyl, and terphenyl and n is an integer of from zero (0) to 5. Among the aromatic ethers, the polyphenyl ethQrs are generally preferred in that they 20 are readily available and exhibit desirable properties for a wide variety of applications. And among the polyphQnyl ethers, those having all their ether linkages in the meta position are in general most preferred ~ince the all-meta linked ethers are the best 25 suited for many applications because of their wide liquid range and high degree of thermal stability. v How ver, mixtures of the polyphenyl ethers, that is, ~ther i~omeric mixtures or mixtures of homologous eth-r~, ar- also suitable, particularly to obtain 30 certain prop~rties, for example, lower solidification points.
Among the aromatic ethers, nonlimiting examples of suitable polyphenyl ethers are diphenyl i ~..... .
F
.
.~,.. . . .
.
~....... .. .
.

8~23 -lO- 43-21~7857)A
ether (also known as diphenyl oxide), the diphenoxybenzQnes, for example, m-diphenoxybenzene, the bis(phenoxyphenyl) ethers, for example, bis(m-phenoxyphenyl) ether, the bis(phenoxyphenoxy)benzenes, for example, m-bis(m-phenoxyphenoxy)benzene, m-bis(p-phenoxyphenoxy)benzene, o-bis(o-phenoxyphenoxy)benzene, the bis(phenoxyphenoxyphenyl) ethers, for example bis~m-(m-phenoxyphenoxy)phenyl] ether, bistp-(p-phenoxyphenoxy)phenyl] ether, [m-(m-phenoxyphenoxy)-phenyl][o-(o-phenoxyphenoxy)phenyl~ ether, and the bis(phenoxyphenoxyphenoxy)benzenes, for example, m-bis[m-(m-phenoxyphenoxy)phenoxy]benzene, p-bis[p-(m-phenoxyphenoxy)phenoxy]benzene, m-bis[m-(p-phenoxyphenoxy)phenoxy]benzene.
It al80 ig contemplated that mixtures of the polyphenyl ethers can be employed in the instant invention. For example, mixtures of polyphenyl ethers in which the nonterminal phenyl (phenylene) rings [that i9, wherein R2, which is enclosed in the bracXets in the above structural formula representation of suitable aromatic ethers, is phenyl (phenylene)] are linked through oxygen atoms in the meta and para positions, -~
are particularly suitable for use in the instant invention in that such mixtures possess lower 25 solidification points and thus provide fluid ~ ~:
composition~ having wider liquid ranges.
Of these mixtures, that is, those having only ~ta and para linkages, a preferred polyphenyl ether mIxture for use in the instant invention is the mixture o~ five-ring polyphenyl ethers where the nonterminal phenylene rings are linked through oxygen atoms in the meta and para positions and composed, by weight, of about 64-65% m-bis(m-phenoxyphenoxy)benzenQ, 30-32% m-' ~

., . ~ , ,. ..
.'-" ' .
. ' ~i~4892~

-11- 43-21(7857)A
[(m-phenoxyphenoxy)(p-phenoxyphenoxy)]benzene, and 3-6% m-bis(p-phenoxyphenoxy)benzene, with the proviso that the sum of the components must egual 100%, with a mixture composed, by weight, of about 64% m-bis(m-phenoxyphenoxy)benzene, 32% m-~(m-phenoxyphenoxy)(p-phenoxyphenoxy)]benzene, and 4% m-bis(p-phenoxyphen-oxy)benzene being most preferred. Such a mixture solidifies at about 4~ C (40- F) whereas the three components solidify individually at temperatures above normal room temperatures.
In addition to the polyphenyl ethers (wherein Rl, R2, and R3 are phenyl), suitable aromatic ethers include those wherein at least one of R~, R2, and R~ is biphenyl or terphenyl. Nonlimiting examples of such aromatic ethers are the phenoxybiphenyls, for example, o-phenoxybiphenyl, m-phenoxybiphenyl, p-phenoxybiphenyl, the bis(biphenylyl) ethers, for exampla, bis(o-biphenylyl) ether, bis(p-biphenylyl) ether, (o-biphenylyl)(p-biphenylyl) ether, the i;
diphenoxybiphenyls, for example, those in which the phenoxy group~ are attached as sub~tituents on different aro~atic rings (of the biphenyl moiety), as in 4,4'-diphenoxybiphenyl, or on the same aromatic ring, as in 3,4-diphenoxybiphenyl, the `~--phenoxyterphenyls, for example, 4-phenoxy-m-terphenyl, and the diphenoxy-terphenyls, including, for example, in ~ manner similar to that noted for the diph-noxybiphenyls, those in which the phenoxy groups are attached as substituents on different aromatic rings (of the terphenyl moiety), as in 4,4'-diphenoxy-m-terphenyl, or on the same aromatic ring, as in 3,4-diphenoxy-m-terphenyl.

.
i . .-..... .
' ~

2~8~3 -12- 43-21(7857)A
In a manner sim~lar to that previously discussed for the polyphenyl ethers, it also is contemplated that mixtures of the aromatic ethers, in general, can be employed in the instant ~nvention. For example, mixtures of o-phenoxybiphenyl and p-phenoxybiphenyl and o-bis(biphenylyl) ether and p-bis(biphenylyl) ether are suitable ~or use in the instant invention. Such mixtures, in general, possess lower solidification points and thereby provide fluid compositions having wider liquid ranges.
The aromatic ethers suitable for use in the instant invention can be obtained by the Ullmann ether synthesis which broadly relate~ to ether-forming reaction of, for example, alkali metal arenoxides (or arenates) such as sodium and potassium phenoxides (or phenates) with aromatic halides, for example, bromobenzene and 4-iodo-4'-bromo-m-terphenyl in the presence of a copper catalyst such as metallic copper, copper hydroxides, or copper salts. Detailed descriptions for the preparation of the polyphenyl ethers are disclosed in U.S. Patent No. 3,451,061 and Sax et al, "Preparation and Infrared Absorption Spectra of Some Phenyl Ethers," J. Org. Chem., 25, 1590-1595 (1960). Detailed descriptions for the preparation of 25 the phenoxyterphenyls (including the multi phenoxy- -substituted terphenyls) are disclosed in U.S. Patent No. 4,143,077. Other aromatic ethers, such as, for ex~Jple, the phenoxybiphenyls, can be prepared as by-product~ in the caustic hydrolysis of chlorobenzene in accordance with the detailed description disclosed in U. S. Patent No. 4,092,364.
Compounds useful as source materials to provide the alkali metal -- that is, the lithium, ~: . ,. ,: ' ..: . .

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. ~ .

8 '3 ~ .~

-13- 43-21(7857)A
sodium, potassium, rubidium, and cesium -- salts of oxalic acid component o~ the fluid co~positions of the instant invention are not narrowly critical. All that is necessary i~ that such compounds provide the desired colloidal dispersion comprising an oxidation inhibiting amount of the alkali metal salt of oxalic acid in the aromatic ether. Suitable source material compounds are compounds convertible at elevated temperatures in the presence of molecular oxygen or a molecular oxygen-containing gas -- that is, under eolloidal dispersion forming conditions -- into the corresponding alkali metal oxalate~. As such, compounds which are suitable as source materials to provide th~ alkali metal oxalates may be considered as precursors of the alkali metal salts of oxalic acid or alkali metal oxalates.
Typical eompounds include those that are insoluble in the aromatie ethers, for example, alkali metal earbonates, those that are partially soluble in the aromatic ethers, for sxample, alkali metal phenates, and those that are soluble in the aromatic ethers, for example, alkali metal phenoxyphenates and alkali metal phenoxyphenoxyphenates. Among such alkali metal compounds, thQ potassium salts are generally preferred in that they are readily available and readily provide the desired eolloidal dispersion.
The fluid compositions of the instant in~ention ean be prepared by mixing the aromatic ether ba~estoek with at least one alkali metal precursor eo~pound to form a mixture in the form of a slurry, slurry/solution, or solution, depending upon the solubility of the alkali metal preeursor eompound in the aromatic ether basestock.

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It will be apparent that the coneentration of the alkali metal precursor eompound in the aromatic ether basestock is not narrowly critical and can vary within fairly wide limits. Indeed, all that is 5 necessary is that the concentration is sufficient to -.
provide the desired eolloidal dispersion o~ the aromatic ether and an oxidative inhibiting amount of the alkali metal salt of oxalic acid as hereinafter discussed. Convenient, albeit nonlimiting, concentrations range from about 1 mmol to about 20 mmols, preferably from about 5 mmols to about 15 mmols, and most preferably from about 8 mmols to about 12 mmols of the alkali metal precursor compound per kilogram (kg) of aromatic ether.
Following the formation of the aromatic ether/alkali metal precursor eompound mixture, the resultant mixture i9 sub~eeted to eonditions effeetive to eonvert the mixture into a colloidal di6persion eomprising an oxidation inhibiting amount of the alkali 20 metal salt of oxalic acid in the aromatic ether. ~ ~
Noneolloidally dispersed solid material, i~ present, is ~ l-separated or r moved from the eolloidal dispersion by a variety of eonventional separation teehniques well known to thofie skilled in the art, ineluding ~ ~-filtration, eentrifugation and decantation of the supernatant eolloidal dispersion from the noncolloidally dispersed solid material. In a pr~ferred embodiment, the noneolloidally dispersed ~terlal i- separated from the colloidal dispersion by filtration through a filter having a pore size effective to retain such noneolloidally dispersed solid ~;~
material and permit the colloidally dispersed particles j..... ,.. . ~ . :, - . . . .
,~, .. ;.. .. - . . - :- ~ :
~,.' :.
.

~, . . .

-15- 43-21(7857)A
to pass therethrough to thereby recover the oxidation inhibited fluid composition.
It will be apparent that the conditions effective to convert the aromatic ether/alXali metal precursor mixture to the desired colloidal dispersion will depend to some extent upon the particular aromatic ether employed as the basestock and the source material for the alkali metal salt of oxalic acid. In general, the mixture i8 heated at a temperature of from about 225' C to about 300- C, preferably about 280- C, in the presence of molecular oxygen or a molecular oxygen-containing gas, preferably air, for a period Or from about 3 hours to about 48 hours, preferably from about 12 hours to about 36 hours, and most preferably from about 20 hours to about 24 hours. At these conditions (which may be conveniently referred to as "alkali metal precursor co~pound conversion conditionsn), the alkali metal precursor compound employed a~ the source material for the alkali metal salt of oxalic acid undergoes an in situ oxidation and is converted into the corresponding alkali metal salt of oxalic acid.
The resultant alkali metal salt of oxalic acid is dispersed as colloidal sized particles to form the desired colloidal dispersion of alkali metal salt of oxalic acid in ths aromatic ether.
The concentration of the alkali metal salt of oYalic acid in the aromatic ether is not narrowly critical and will depend to some extent upon the particul~r aromatic ether and alXali metal salt of oxalic acid employed as components of the fluid composition and the ultimate end use for the fluid composition. All that is necessary is that the alkali metal salt of oxalic acid be present as a colloidal .~
.;. . .~ .
. ~ . ..

.~,"'.'.-~- ,.''~ ' ' - ~1)48923 -16- 43-21(7857)A
dispersion at a concentration e~ective to inhibit oxidative degradation of the aromatic ether. At the same time, however, the concentration of the colloidally dispersed alkali metal salt of oxalie acid must not exceed, or preferably must be less than, the agglomeration/precipitation threshold for such alkali metal salt of oxalie aeid in the aromatic ether. In general, concentrations of from about 0.20 mmol to about 2.50 mmol8, prererably from about 0.30 mmol to about 2.00 ~mols, of colloidally dispersed alkali metal oxalate per kg of fluid composition are sufficient to impart the desired inhibition of oxidative degradation to the aromatic ether. However, in the event the concentration of the colloidally dispersed alkali metal salt of oxalic acid is greater than the agglomeration/precipitation threshold value for such alkali metal salt of oxalie aeid in the aromatie ether, i~ particular greater than the generally desirable 2.50 mmols/kg upper limit or greater than any other specified desirable value, fresh aromatie ether may be added to the fluid eomposition to dilute the fluid composition to a desirable concentration of choiee.
It will be apparent to those skilled in the --art that the fresh aromatic ether employed as a diluent may be the same as, or different from, the aromatie ether ba~estoek employed initially to prepara the eolloidal dispersion. A different aromatie ether, ineluding blends of two or more aromatie ethers, may be used advantageou~ly as a diluent to aehieve eertain de~irable properties -- for example, a lower solidification point for the aromatie ether basestoek and ultimately the fluid composition.

~;' ~'.. ,'~ ' ., ': - : . ,, , .. .
.
; -~ ' ' ' '.- .
.. ' .. . . .
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The following speci~ic examples illustrating the best currently-known method o~ practicing this invention are described in detail in order to facilitate a clear understanding of the invention. It should be understood, however, that the detailed expositions of the application of the invention, while indicating preferred embodiments, are given by way of illustration only and are not to be construed as limitinq the invention since variou~ changes and modifications within the spirit of the invention will become apparent to those skilled in the art ~rom this detailed description.

General (a) Oxidative Stability The oxidative stability of the fluid compositions of, and prepared in aeeordanee with, this invention, as well as that of the aromatie ether basestock, was determined using a modified Corrosion &
Oxidation (C&O) test as speeified in the military speeification MIL-L-87100 in accordance with Method 5307 of FED-STD 791. In accordance with this test, the fluid composition (lubricant) to be tested was heated over a 48-hour period at a speci*ie temperature t343- C
(650- F), as opposed to the stated standard temperature of 320- C (608- F] at a dry air flow rate through the ~-~luid composition of 10 L/hr in the presenee of certain ~ tal specimen speeified as aluminum (bottom), silver, mild steel, ~-50 steel, Waspaloy (a nickel-based alloy), and titanium (top) and the viscosity increase of the fluid composition was determined. In addition, information a~ to the corrosivity of a fluld composition to metals may be determined, if desired.

-: -- - - -~.. ~-. .. :.: . . -.-,- :. . ..., - ~, :- . .
: . - .- . . ~ . .
, .. .. .
,~

~,148923 `\
-18- 43-21(7857)A
Viscosity measurements were made according to ASTM Method D445-88 using a Cannon-Fenske modified Ostwald viQcosimeter. The percentage o~ viscosity increase was determined by taking the difference in viscosity of a fluid composition be~ore and a~ter it was heated, dividing that difference by the original viscosity and multiplying the quotient by 100.
(b) Storage Stability The storage stability of the fluid compositions of this invention, as well as that of the aromatic ether basestock, was determined using Method 3403 of FED-STD 791, except that the method was modified to serve as an accelerated storage stability test. In accordance with this modified test, a sample of the fluid composition (neat) to be tested was stored in a loosely capped glass container (usually a small flask) in an oven maintained at 120-125- C (24a-257- F) for a period o~ 168 hours or more, up to several ~ -months. At the end of the storage period, the sample, without a final centrifugation step, was visually inspected for turbidity with white light shining through tha sampl6 at a 180- angle to the line of sight. Noticeable turbidity at any time during the test period resulted in the fluid composition being characterized as having failed the test.
(c) ~ erial Component Identification The colloidally dispersed solid material -co~ponent Or the fluid compositions was isolated from th- fluid composition by mixing the fluid composition with di~thyl ether and extracting ths fluid composition/diethyl ether mixture with water, followed by evaporation of the agueous extract to yield a ~olid ~-material. The resultant solid material was identified ,:.
.
.,.-,., ,, , , ' .', . . . - , 2 (~ 2 3 -19- 43-21(7857)A
as the corresponding alkali metal salt of oxalic acid (for example, potassium oxalate for potassium precursor compounds), usi~g standard procedures, by ln~rared spectra, titration with hydrochloric acid, titration with permanganate, and ICAP analysis.
EXAMPLE 1 (Comparative) This Example illustrates a typical prior art process using soluble potassium salts to stabilize polyphenyl ethers. The fluid composition was prepared according to the procedure described in Example 38 of U.S. Patent No. 3,492,229.
A polyphenyl ether basestock having a composition, by weight, of:
64% m-bis~m-phenoxyphenoxy)benzene 32% m-t(m-phenoxyphenoxy)(p-phenoxyphenoxy)]-benzene 4S m-bis(p-phenoxyphenoxy)benzene was employed. Potassium m-(m-phenoxyphenoxy)phenate was dissolved in the basestock at two concentration levels -- 7.40 mmols/kg and 3.12 mmolsJkg. These fluid compositions were further diluted with additional polyphenyl ~ther basestock to provide samples at concentrations of 1.58 mmols/kg and 0.79 mmol/kg. The - ~ -oxidative stability and the ~torage stability of the fluid compo~itions were determined as described for the Oxidative Stability test and the Accelerated Storage Stability te~t, respectively. The results were as --~

- . ~ -' "'`~"`.' ;, -.; -2~4~923 -20- 43-21(7857)A
C&O R~-ult-Conc l (Vl-co-ltv m2/-)2 Aq~, Ator~- 8t~bllltv ~gmL~ mmol-~ka ~nl~ia~3 ~ ~ Chang- AD~ear~nc~ Comment 51 7 40 368 0 463 0 ~25 8 Dark browr~ rall~d ppt ~

2 3.12 364.o 434.o ~19.3 Dark brown Fall~d ~pt 4 3 1.58 ND5 ND5 ND5 D-rltbrown Fall-d ppt 4 0.79 ND5 ND5 ND5 Tran~parQnt~ P~ d --..... : , ".

~Potassium m-(m-phenoxyphenoxy)phenate in the ~luid composition.
2At 38- C (100' F). -3Stated value x 106.
~After one ~1) week.
5Not determined.
The result~ indicate that the fluid compositions containing soluble potassium salts exhibited excellent results in the C&0 tQst at 343- C ;~-~
(650- F). However, except for Sample 4, the fluid compositions developed clumps of dark brown precipitate following one (1) week of storage, thereby failing the Accelerated Storage Stability test. The formation of th dark brown precipitate further indicates the lik lihood that such fluid compositions could be prone ~ -~
to ~orming deleterious precipitates under use con~
30 ditions, particularly, high stres~ conditions. - `~
- .
'- . -: `

,...

, '~ .
~, , ' '.

'~J48923 -21- 43-21(7857)A
EXAMpLE 2 This Example illustrates the preparation of a colloidal dispersion of an alkali metal oxalate, potassium oxalate, in an aromatic ether basestock from an insoluble alkali metal salt, potassium carbonate.
Run 1 The polyphenyl ether basestock (405 g) employed in Example 1 was charged to a 500 mL round-bottomed flask fitted with a glass paddle stirrer, a fritted glass air bubbler, a thermometer, and a bent glass exit tube and heated while a stream of air [flowing through a tube packed with anhydrous calcium sulfate (Drierite)] was passed therethrough at the rate of 75 scc/~in. When the temperature of the polyphenyl ether basestock had reached 130- C, 0.34 g (0.0025 mol) of potassium carbonate in the form of coarse granular powder (primarily larger than 50 mesh ~300 microns (~m)]) was added, with rapid stirring to thoroughly mix and suspend the potassium carbonate in the polyphenyl ether basestock. Heating was continued to raise the tempsrature of the mixture to 280- C, while maintaining the passage of air therethrough. The mixture was maintained at these conditions for 23 hours, after ;-- --which the air flow was turned off. The mixture was allowed to cool to 120- C and was filtered through a Buchner funnel using a glass fiber filter (GF/F filter ~-~
fro~ Whatman) having an effective pore size of 0.7 ~m ~ -to re~ove noncolloidally dispersed solid-phase mate- - --r~l. The r~3ultant fluid composition of a colloidal 30 dispersion of potassium oxalate in the polyphenyl ether -~
basestock was shown to have a concentration of 1.17 -~
mmols of potassium oxalate per kg of fluid composition by titrating three samples (6.1 g, 6.1 g, and 4.5 g) of ~ -' . ~' "`-, . . . .

i, - .
' .' ' . . .
:-. .
~'`~"' ' ' " , '.`'.
.... ~ .

-22- 43-21(7857)A
the fluid composition with 0.01 N hydrochloric acld in water-acetone solvent to the ~irst end point tXH(C00)2]
using bromphenol blue indicator, ~ollowed by averaging the results obtained for the three samples. The ~luid composition was diluted with fresh polyphenyl ether basestock to yield several lower concentrations.
The solid phase material collected in the Buchner funnel on the filter, as w~ll as that remaining in the reaction flask, was washed several times with hot hexane to remove residual polyphenyl ether basestock and dried. The resultant dry solid phase material was identi~ied as a mixturs o~ potassium carbonate (75% by weight) and potassium oxalate (25~ by weight).
15 Run 2 ;~
The procedure described in Run 1 was repeated to yield n fluid composition of a colloidal dispQrsion of potassium oxalate in the polyphenyl ether basestock at a concentration of 1.67 mmols/kg.
A C&0 test from Runs 1 and 2 was carried out on the fluid compositions at various concentrations. ~ --An Accelerated Storage Stability tes~ wa~ carried out on the Run 2 fluid composition (Sa~ple 6). In ;~
addition, a comparative C&0 test was carried out on the 25 neat polyphenyl ether basestock. The results were a~ ~-follow~: -- ~

` ` .`, , ` , .
.~

~1)48923 -23- 43-21(7857)A

C&0 R-~ult-conc.l LVl-co~ltv. m2/~2 ACC. Stor~qe Stabllltv Sam~le mmol~/k~ In~ 3 Fln~13 ~ Ch~no~ AoDe~ranc- Comment 1 0.00~ 12.45 237.6 +1809.0 ND5 26 0.070 12.72 104.7 l723.0 ND5 3~ 0.1~ 12.68 58.1 +358.0 ND5 4~ 0.21 12.70 30.2 +137.0 ND5 56 0.35 12.70 13.33 +5 ND5 67 1.67 12.68 13.S5 +6.9 ~ran-p~r-nt~ P~ d .. .
lPotassium oxalate tK2(C00)2~ in the fluid composition. -- -2At 100 C (212- F)-3Stated valuo x 10 6.
~Neat polyphenyl ether basestock.
5Not determined.
~From Run 1 followinq dilut~on with fresh polyphenyl ether basestock.
7From Rum 2.
20 8After twenty-thrae (23) weeks. -The results demonstrate that at a threshold concentration of about 0.30 mmol/kg, a substantially constant level Or oxidation inhibition i8 provided.
Howevor, at concentrations bQlow this threshold level, the degree of oxidation inhibition, although observ-able, falls off quite rapidly. :~
EXAMpT-~
- - This ~xample illustrates the preparation of a -~
cQlloidal dispersion of an alkali metal oxalate,~`-` ;`
pota-sium oxalate, in an aromatic ether basestock from a soluble alkali metal salt, potassium m-(m- ;~-phenoxyphenoxy)phenate. ~ - `

. '.' " ,~ : , ' ' , '' ' ':
'-` ~ ' . . , ' ;:

~''''-'.' ' ' : "
, .

211~8923 -24- 43-21(7857)A

The procedure described in Example 2, Run 1 was employed except that 1.03 g (0.0033 mol) Or potassium m-(m-phenoxyphenoxy)phenate (which i9 soluble in the polyphenyl ether basQstock) was substituted ror the potassium carbonate and 273 g o~ polyphenyl ether basestock was employed to yield a solution of potassium phenoxyphenoxyphenate in the polyphenyl ether basestock of 12.00 mmols/kg. Following the heating with air at 280- C for 23 hours and filtration, the resultant fluid composition of a colloidal dispersion of potassium oxalate in the polyphenyl ether basestock had a --concentration Or 4.67 mmols/kg.
15 Run 2 ~
The procedure described in Run l was repeated - ~-except that 1.53 g (0.048 mol) Or potassium m-~m-phenoxyphenoxy)phenate was dissolved in 404 g of polyphenyl ether basestock to yield a solution of potassium m-(m-phenoxyphenoxy)phenate in polyphenyl ether Or 12 ~mols/kg and the solution was heated rOr 21 `~
hours at 280- C in the presence of air. After filtration, the resultant fluid composition Or a colloidal dispersion of potassium oxalate in the -polyphenyl ether basestock had a concentration of 4.56 mmols/kg. The ~luid composition was diluted with fresh -~
polyphenyl ether basetock to a concentration of 0.70 l/kg.
A C~0 test was carried out on the fluid compositions from Runs 1 and 2 and an Accelerated Storage Stability test were carried out on the fluid compo~ition from Run 2. The results were as follows:

.`~ ~ , .~ .

:
. ~ .
.: : .

, ~ - - .

2~8923 -25- 43-21(7857)A
C~O R--ult~
Conc l ~Vl-co~ltv,_~2/~)2 Acc Stora~- 8t~bllltv ~gmDL~ mmol~/k~ Inltlal3 Flnal3 ~ Chana- A~oar~nc- Comment 1~ 0 70 12 74 13 91 +9 18 Tran~paren~5 P~ d 2~ 4 67 12 73 14 11 +10 80 ND7 '':
lPotassium oxalate ~X2(COO)2] in the fluid composition.
2At 100- C (212- F). -3Stated value x 10~.
~From Run 2 ~ollowing dilution with fresh polyphenyl ether basestock.
5After fifteen (15) weeks.
6From Run 1.
7Not determined. However, at the end of the C&0 test, a crystalline precipitate was present, thereby indicating that the concentration of potassium oxalate in the fluid composition was too high to remain stable as a colloidal dispersion. - ~
EXAM~ 4 ---Thi~ Example illustrates the preparation of a colloidal dispersion of an alkali metal oxalate, potassium oxalate, in an aromatic ether basestock from --a partially soluble alkali metal salt, potassium -~
phenate.
Run 1 The procedurs described in Example 2, Run 1 was e~ployed exc~pt that 1.27 g (0.0096 mol) of potassium pb-n~te (which is slightly soluble in the polyphenyl ~th-r ba6Qstock) was substituted for the potassium 30 carbonate and mixed with 800 g of the polyphenyl ether -ba~estock in a 1000 mL round-bottomed flask fitted as described in Example 1, Run 1 to yield a slurry/solution of potassium phenate in the polyphenyl ~ . , .
~ .

~'' - ' ~ ' .
.: . , .

~i~A~923 -26- 43-21(7B57)A
ether basestock of 12.00 mmols/kg. Following the heating with air (150 scc/min.) at 280- C for 45 hours and filtration (at 120-C), the resultant fluid composition of a colloidal dispersion of potassium oxalate in the polyphenyl ether basestock had a concentration of 1.83 mmols/kg. The solid material collected on the ~ilter consisted primarily of potassium oxalate, with traces of unidentified impurities (possibly potassium carbonate or potassium phenate).
Run 2 The procedure described in Run 1 was repeated except that 5.30 g (0.040 mol) of potassium phenate was mixed with 3346 g of polyphenyl ether basestock to yield a slurry/solution of potassium phenate in polyphenyl ether of 12 mmols/kg and the slurry/solution was heated for 23 hours at 280-C in the presence of air. After filtration, the resultant fluid composition of a colloidal di persion of potassium oxalate in the polyphenyl ether basestock had a concentration of 2.67 mmols/kg. The fluid composition wa~ diluted with fresh ~ -polyphenyl ether ba~estock to provide a concentration of 0.70 mmol/k~. A C&0 test and an Accelerated Storage - --Stability test were carried out on the diluted fluid composition. The results were a~ follows:

~-, '"'~
.' : .
:
.-2~48923 -27- 43-21(7857)A

C&O R--ult-Conc.l LVl-co~itv. mZ/~2 Acc. Storaae Stab-lltY
SamD1~ mmol-lka ~n~lal3 ~ ~ Chana~ A~D~a~a~c~ Comment 1 0~70 12.4a 13.56 +8.70 Tran-p~r-nt~ P~ d lPotassium oxalate [K2(COO)2~ in the ~luid composition. --2At 100- C (212- F). -3Statad value x 1o6. -~

10 ~After forty-two (42) weeks. --This Example illustrates the preparation of a colloidal dispersion of an alkali metal oxalate, sod$um ~ -oxalate, in an aromatic ether basestock from a soluble alkali metal salt, sodium m-phenoxyphenata.
Tha procedure described in Example 2, Run 1 was employed, excapt that 0.38 g ~0.0018 mol) of sodium m-phenoxyphenate (which is soluble in the polyphenyl ~ ~ -ether basestock) was substitutQd ror the potassium 20 carbonate and dissolved in 302 g of the polyph~nyl ~ -ether baststock to yield a solution o~ sodium m- - ~
phenoxyphenate in the polyphenyl ether basestock of ~---~-;
6.00 mmols/kg. Following the heating with air at 280- --C for 16 hours and filtration, the resultant fluid 25 composition of a colloidal suspension of sodium oxalate -in the polyphanyl ether basestock had a concentration of 0.90 mmol/kg.
-- The ~luid composition was diluted with fresh -polyphenyl ether basestock to provide a concentration of 0.70 mmol/kq. A C&O test and an Accele~ated Storage Stability test were carried out on the diluted fluid composition. The results were as follows:

~.. ,.~ .,..., , ;

,--28- 43-21(7857)A
C~O R-~ult-Conc 1 ~Vl-co-ltY m2/~2 Acc Stora~e Stabllltv Samol~ mmol~/k~ L~ al~ ~ ~ Chan~- ADoearanc- Comment 1 0 70 12 51 39 60 +137 00 Transpar~nt4 Pass~d 1Sodium oxalate ~Na2(C00)2] in the ~luid compo~ition.
2At 100- C (212- F).
3Stated value x 10 6 4After nine (9) weeks.

This Example illustrates the preparation of a colloidal dispersion of alkali metal oxalate, potassium oxalate, in an aromatic ether basestock from a soluble alkali metal salt, potassium m-(m-phenoxyphen-lS oxyphenate.
The procedure described in Example 3 wasemployed, except that a six-ring polyphenyl ether basestock, bistm-(m-phenoxyphenoxy)phenyl] ether, was substituted for the five-ring polyphenyl ether basestock. Following the heating with air at 280- C
for 21 hours and filtration, the resultant fluid composition of a colloidal disper~ion of potassium oxal~te in the polyphenyl ether basestock had a concentration of 2.09 mmols/kg. --A portion of the fluid composition was diluted with fresh polyphenyl ether basestock to provide a ~-cond concentration o~ 1.40 m~ol~/kg. A C&0 test and ~a Accelerated Storage Stability test were carried out o~ the fluid composition at the two concentrations.
30 The results were as follows: -~"
,~
.
::~
;:
~s~-~J~8923 -29- 43-21(7857)A
C60 R--ult-conc.l(vlsco~lty~ m2/s)2 A~c- storag- 8t~bllitY
Samol~ mmol~/k~Fin~l,3 ~ Ch~ng- Ao ~ ar~nce Con ~ nt --1 1.~0 24.58 27.02 +9.93 Tr~n-par-nt4 Pa~-d 52 2.09 24.41 27.13 l11.14 sran-par-nt4 Pa~-~d ~:
;..~ " .
lPotassium oxalate tK2(C00)2] in the fluid compo~ition.
2At 100- C (212- F). ;
10 3Stated value x 10~. -~After thirty-seven (37) day8.
Thus, it is apparent that there has been ~ ~-provided, in accordance with the instant invention, fluid compositions that fully satisfy the ob~ects and advantages set forth hereinabove. While the invention has been described with respect to various specific -~-exaDIples and embodiments thereof, it i8 understood that ~--the invention is not limited thereto and many alternatives, modification~, and variations will be apparent to those ~killed in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variation~ a~ fall within the spirit and broad scope of the invention. ~-~ `

~ ..
. . .~,

Claims

1. A fluid composition comprising a colloidal dispersion of:
(a) an aromatic ether represented by the formula wherein R1, R2, and R3 independently are phenyl, biphenyl, and terphenyl and n is an integer of from zero (0) to 5, and (b) an oxidation inhibiting amount of an alkali metal salt of oxalic acid, the fluid composition being characterized by being transparent when subjected to visual inspection with white light shining through the fluid composition at a 180° angle to the line of sight.

2. The fluid composition of Claim 1 wherein the aromatic ether is a polyphenyl ether.

3. The fluid composition of Claim 2 wherein the polyphenyl ether is a mixture of five-ring polyphenyl ethers having the nonterminal phenylene rings linked through oxygen in the meta and para positions.

4. The fluid composition of Claim 3 wherein the mixture of five-ring polyphenyl ethers comprises a composition, by weight, of 64-65% m-bis(m-phenoxy-phenoxy)benzene, 30-32% m-[(m-phenoxyphenoxy)(p-phenoxyphenoxy)]benzene, and 3-6% m-bis(p-phenoxyphen-oxy)benzene.

5. The process of Claim 4 wherein the mixture of five-ring polyphenyl ethers comprises a composition, by weight, of 64% m-bis-(m-phenoxyphenoxy)benzene, 32%
m-[(m-phenoxyphenoxy)(p-phenoxyphenoxy)]benzene, and 4%
m-bis(p-phenoxyphenoxy)benzene.

6. The fluid composition of Claim 2 wherein the polyphenyl ether is a six-ring polyphenyl other.

7. The fluid composition of Claim 6 wherein the six-ring polyphenyl ether is bis[m-(m-phenoxyphonoxy)-phenyl ] ether.

8. The fluid composition of Claim 1 wherein the aromatic ether is a phenoxybiphenyl.

9. The fluid composition of Claim 8 wherein the phenoxybiphenyl is selected from the group consisting of o-phenoxybiphenyl, p-phenoxybiphenyl, and mixtures thereof.

10. The fluid composition of Claim 1 wherein the aromatic ether is a bis(biphenylyl) ether.

11. The fluid composition of Claim 10 wherein the bis(biphenylyl) ether is selected from the group consisting of bis(o-biphenylyl ) ether, bis(p-biphenylyl) ether, bis(o-biphenylyl)(p-biphenylyl) ether, and mixtures thereof.

12. The fluid composition of Claim 1 wherein the aromatic ether is a diphenoxybiphenyl.

13. The fluid composition of Claim 12 wherein the diphenoxybiphenyl is selected from the group consisting of 4,4'-diphenoxybiphenyl, 3,4-diphenoxybiphenyl, and mixtures thereof.

14. The fluid composition of Claim 1 wherein the aromatic ether is selected from the group consisting of phenoxyterphonyls and diphenoxyterphenyls.

15. The fluid composition of Claim 14 wherein the aromatic ether is a phenoxyterphenyl.

16. The fluid composition of Claim 15 wherein the phenoxyterphenyl is 4-phenoxy-m-terphenyl.

17. The fluid composition of Claim 14 wherein the aromatic ether is a diphenoxyterphenyl.

18. The fluid composition of Claim 17 wherein the diphenoxyterphenyl is 4,4'-diphenoxyterphenyl.

19. The fluid composition of Claims 1, 2, 3, 4, 5, 6, or 7 wherein the colloidal dispersion of the alkali metal salt of oxalic acid in the aromatic ether has a concentration of from about 0.20 mmol to about 2.50 mmols of alkali metal salt of oxalic acid per kg of fluid composition.

20. The fluid composition of Claim 19 wherein the concentration of the alkali metal salt of oxalic acid is from about 0.30 mmol to about 2.00 mmols per kg of fluid composition.

21. The fluid composition of Claim 1 wherein the alkali metal of the alkali metal salt of oxalic acid is selected from the group consisting of sodium and potassium.

22. The fluid composition of Claim 21 wherein the alkali metal of the alkali metal salt of oxalic acid is potassium.

23. A process for the preparation of an oxidation inhibited fluid composition comprising:
(a) mixing an aromatic ether represented by the formula wherein R1, R2, and R3 independently are phenyl, biphenyl, and terphenyl and n is an integer of from zero (0) to 5, and an alkali metal precursor compound convertible under alkali metal precursor compound conversion conditions into an alkali metal salt of oxalic acid, (b) heating the aromatic ether/alkali metal precursor compound mixture from Step (a) at an elevated temperature in the presence of molecular oxygen or a molecular oxygen-containing gas and for a time sufficient to convert the alkali metal precursor compound into an alkali metal salt of oxalic acid and form a colloidal dispersion of the aromatic ether and an oxidation inhibiting amount of the alkali metal salt of oxalic acid, and (c) separating any noncolloidally dispersed solid material from the colloidal dispersion to thereby recover the oxidation inhibited fluid composition, the fluid composition being characterized by being transparent when subjected to visual inspection with white light shining through the fluid composition at a angle to the line of sight.

24. The process of Claim 23 wherein the aromatic ether is a polyphenyl ether.

25. The process of Claim 24 wherein the polyphenyl ether is a mixture of five-ring polyphenyl ethers having the nonterminal phenylene rings linked through oxygen in the meta and para positions.

26. The process of Claim 25 wherein the mixture of five-ring polyphenyl ethers comprises a composition, by weight, of 64-65% m-bis(m-phenoxyphenoxy)benzene, 30-32% m-[(m-phenoxyphenoxy)-( p-phenoxyphenoxy)]benzene, and 3-6% m-bis(p-phenoxyphenoxy)benzene.

27. The process of Claim 26 wherein the mixture of five-ring polyphenyl ethers comprises a composition, by weight, of 64% m-bis(m-phenoxyphenoxy)benzene, 32% m-[(m-phenoxyphenoxy)(p-phenoxyphenoxy)]benzene, and 4% m-bis(p-phenoxyphen-oxy)benzene.

28. The process of Claim 24 wherein the polyphenyl ether is a six-ring polyphenyl ether.

29. The process of Claim 28 wherein the six-ring polyphenyl ether is bis[m-(m-phenoxyphenoxy)phenyl] ether.

30. The process of Claim 23 wherein the aromatic ether is a phenoxybiphenyl.

31. The process of Claim 30 wherein the phenoxybiphenyl is selected from the group consisting of o-phenoxybiphenyl, p-phenoxybiphenyl, and mixtures thereof.

32. The process of Claim 23 wherein the aromatic ether is a bis(biphenylyl) ether.

33. The process of Claim 32 wherein the bis(biphenylyl) ether is selected from the group consisting of bis(o-biphenylyl) ether, bis(p-biphenylyl) ether, (o-biphenylyl)(p-biphenylyl) ether, and mixtures thereof.

34. The process of Claim 23 wherein the aromatic ether is a diphenoxybiphenyl.

35. The process of Claim 34 wherein the diphenoxybiphenyl is selected from the group consisting of 4,4'-diphenoxybiphenyl, 3,4-diphenoxybiphenyl, and mixtures thereof.

36. The process of Claim 23 wherein the aromatic ether is selected from the group consisting of phenoxyterphenyls and diphenoxyterphenyls.

37. The process of Claim 36 wherein the aromatic ether is a phenoxyterphenyl.

38. The process of Claim 37 wherein the phenoxyterphenyl is 4-phenoxy-m-terphenyl.

39. The process of Claim 36 wherein the aromatic ether is a diphenoxyterphenyl.

40. The process of Claim 39 wherein the diphenoxyterphenyl is 4,4'-diphenoxyterphenyl.

41. The process of Claim 23 wherein the alkali metal of the alkali metal precursor compound is selected from the group consisting of sodium and potassium.

42. The process of Claim 41 wherein the alkali metal of the alkali metal precursor compound is potas-sium.

43. The process of Claim 23 wherein the alkali metal precursor compound is selected from the group consisting of compounds which are insoluble, partially soluble, and soluble in the aromatic ether.

44. The process of Claim 43 wherein the alkali metal precursor compound is insoluble in the aromatic ether.

45. The process of Claim 44 wherein the insoluble alkali metal precursor compound is an alkali metal carbonate.

46. The process of Claim 45 wherein the alkali metal carbonate is selected from the group consisting of sodium and potassium carbonate.

47. The process of Claim 46 wherein the alkali metal carbonate is potassium carbonate.

48. The process of Claim 43 wherein the alkali metal precursor compound is partially soluble in the aromatic ether.

49. The process of Claim 48 wherein the partially soluble alkali metal precursor compound is an alkali metal phenate.

50. The process of Claim 49 wherein the alkali metal phenate is selected from the group consisting of sodium phenate and potassium phenate.

51. The process of Claim 50 wherein the alkali metal phenate is potassium phenate.

52. The process of Claim 43 wherein the alkali metal precursor compound is soluble in the aromatic ether.

53. The process of Claim 52 wherein the soluble alkali metal precursor compound is selected from the group consisting of an alkali metal m-phenoxyphenate, an alkali metal m-(m-phenoxyphenoxy)-phenate, and mixtures thereof.

54. The process of Claim 53 wherein the soluble alkali metal precursor compound is an alkali metal m-phenoxyphenate.

55. The process of Claim 54 wherein the alkali metal m-phenoxyphenate is selected from the group consisting of sodium m-phenoxyphenate and potassium m-phenoxyphenate.

56. The process of Claim 55 wherein the alkali metal m-phenoxyphenate is potassium m-phenoxyphenate.

57. The process of Claim 53 wherein the soluble alkali metal precursor compound is an alkali metal m-(m-phenoxyphenoxy)phenate.

58. The process of Claim 57 wherein the alkali metal m-(m-phenoxyphenoxy)phenate is selected from the group consisting of sodium m-(m-phenoxyphenoxy)phenate and potassium m-(m-phenoxyphenoxy)phenate.

59. The process of Claim 58 wherein the alkali metal m-(m-phenoxyphenoxyphenate is potassium m-(m-phenoxyphenoxy)phenate.

60. The process of Claim 23 wherein the aromatic ether/alkali metal precursor compound mixture has a concentration of from about 1 mmol to about 20 mmols of the alkali metal precursor compound per kg of aromatic ether.

61. The process of Claim 60 wherein the concentration of the alkali metal precursor compound is from about 5 mmols to about 15 mmols per kg of aromatic ether.

62. The process of Claim 61 wherein the concentration of the alkali metal precursor compound is from about 8 mmols to about 12 mmols per kg of aromatic ether.

63. The process of Claim 23 wherein the aromatic ether/alkali metal precursor compound mixture is heated at a temperature of from about 225° C to about 300° C for a period of time of from about 3 hours to about 48 hours.

64. The process of Claim 63 wherein the temperature is about 280° C.

65. The process of Claim 63 wherein the period of time is from about 12 hours to about 36 hours.