Note: Descriptions are shown in the official language in which they were submitted.
10'75890
The most widely used dielectric fluids heretofore
have been highly chlorinated hydrocarbons, ~uch as the poly-
chlorinated biphenyls (PCB's). While these are functionally
satisfactory, they are highly objectionable from an environ-
mental and ecological standpoint because of their high
toxicity and extreme resistance to biodegradation. For
this reason, acceptable substitutes have been actively
sought.
Polyhalogenated diphenyl oxides are known to be
useful as dielectric fluids J either alone ~U.S.P. 2~022J634~
Britton et al, November 26, 1935) or in admixture with alkyl-
diphenyl oxides (U.S.P. 2,169,995, Coleman et al, August 22,
1939). Such ~luids are no longer acceptable, however,
because the polyhalo component is not sufficiently biodegrad-
able.
Alkylated diphenyl oxides have been recommended
for use as dielectric fluids (U.S.P. 2,170,809, Coleman et
al, August 29, 1939), but have never ound wide use ~ecause
of their poor electrical properties, especially their low
dielectric constants.
hower alkylchlorodiphenyl oxides are known and
have been suggested for use as dielectric fluids (U.S.P.
2,170,989, Coleman et al, August 29, 1939), but have not
been accepted in the industry because of high volatility,
low flash point and relatively poor electrical properties.
According to the pre~ent invention, dielectric
fluids having suitable physical, chemical, electrical and
biological properties comprise a mixture of diphenyl oxide
(DPO) compounds, at least one o~ which is an alkylhalo DPO
and at least one is a monohalo DPO. The alkylhalo DPO has
16,759A-F ~
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10758~0
1-3 alkyl groups of 2-12 carbon atoms each, the total
alkyl carbon content being 2-16, and one halogen substi-
tuent. In another embodiment, the alkylhalo DPO has 1-2
alkyl groups of 4-12 carbon atoms each, the total alkyl
carbon content being ~-16, and one halogen substituent.
The halogen in both components of the fluid is chlorine
or bromine. In one embodiment, the proportions of halo
DPO and alkylhalo DPO are between 30:70 and 70:30; i.e.,
; the mixture should contain at least 30~ by weight of each
component.
The present invention resides in a dielectric
fluid comprising a mixture of: (a) less than 30~ of at
least one monochloro- or monobromodiphenyl oxide; and
(b) more than 70% of at least one monochloro- or mono-
lS bromoalkyl diphenyl oxide having 1-3 alkyl groups, each
of which has 2-12 carbon atoms, said oxide having a -
total of 2-16 alkyl carbon atoms, the percentages of
(a) and (b) being based on the total weight of the mixture.
As indicated above, the monochloro- and mono-
bromoalkyldiphenyl oxide component in the mixture can
have 1-3 alkyl substituents. Thus, for example, in a
; specific embodiment, the dielectric fluid can comprise
a mixture of (a~ monochlorodiphenyl oxide and (b) a
mixture of monochlorobutyldiphenyl oxide, monochloro-
butyldiphenyl oxide, and monochlorotributyldiphenyl
oxide. In a more specific embodiment, in the mixture
defined above, the monochlorodiphenyl oxide is present ~ -
in an amount between 5 and 40 weight percent, the mono-
chlorobutyldiphenyl oxide is present in an amount between
30 and 80 weight percent,
16,7~9~-~ -2-
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the monochlorodibutyldiphenyl oxide i3 present in an amount
between lO and 50 ~eight percent, and the monochlorotri-
butyldiphenyl oxide is present: in an amount between 2 and
lO weight percent
The alkylation and halogenation of DP0 are well
known in the art. It is recognized in the art that these
reactions inherently produce a mixture of isomeric, homolo-
gous and/or analogous compounds wherein the number and
arrangement of the substituents vary. Such mixtures, usualiy
referred to as cogeneric mixtures, can be partially or com-
pletely resolved by fractional distillation and/or crystalli-
zation, or by other known means. For the present purpose~
however, it has been found that such separation is not
ordinarily necesqary~ provided the average values stay
within the limits set forth herein. In particular, polyhalo
components should not be present in more than very low
concentrations because of their increaqed toxicity and
resistance to biod~gradability. For most applications,
concentrations of dihalo compounds of up to about 5% can
be tolerated.
Examples l-ll
The table below shows several important properties
of some typical examples of the invention~
In the table the DP0 compounds are identified by
the substituents on the DP0 nucleus. Thus~ for instance,
Cl-C12- is monochlorododecyldiphenyl oxide. The hexyl and
butyl substituents are repres~ented by C6 a~d C4, respec-
tively. Except as indicated5 the mixtures used in ~he
examples were 50:50 by weight.
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~'75~39~
All of the above materials are readily biodegrad-
ab]e, as are the homologous mono- and dialkychloro- and
-bromo~DP0 compounds.
BxamPle 12
The toxicity to fish of the dielectric fluids
was determined by a 96 hour static water test u~ing
Fathead minnows. In these runs, the toxicity of monochloro-
diphenyl oxide, monochlorobutyldiphenyl oxide, and mixtures
thereof was determined. Table II below sets forth the
results which were obtained. Tan fish were employed in
each run. The EC50 is defined as the concentration of
the oxides in the water in milligrams per liter at which
50 percent of five of the fish remain unaffected (the
five remaining fish were either dead or demonstrated evi-
dence of toxicity).
TABLE II
Wt.% C4Cl-DP00 70 75 80 85 90 95100
Wt.% Cl-DP0100 30 25 20 15 10 5 0
EC50 Expected 5.7 6.8 8.5 11 17 34
EC50 obs2rved 1.7 7 7 7 20 27 ~T MT
~T means not toxic at the solubility in water
As can be seen from the data in Table IIg the
EC50 for the monochlorodiphenyl oxide by itself is only
1.7 mg/liter of water. The presence of the monochloro-
alkyldiphenyL oxide apparently diminishes the toxicity
of the Cl DP0 because the actual EC50 is much greater
than expected for mixtures containing up to 15 percent Cl DP0.
Other alkylhalo DP0 compounds that may be mixed
with Cl-DP0 and/or Br-DP0, in proportions of 30-70/0 for
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~'75~19~)
example, to produce dielectric fluids according to the
invention include the ethyl-, propyl-, hexyl-, octyl-,
decyl-, dihexyl-, dioctyl-, hexyl octyl-, heptyl nonyl-,
and hexyl decyl-Cl-DPO and the corresponding alkyl-Br-
-DPO compounds. In these compounds, the positions of
the substituents on the DPO uncleus is of little signifi-
cance in the present inventio:n. Likewise, the coniguration
of the alkyl groups is relatively unimportant, though those
having a high degree of branching are less readily biode-
gradable than those having straight chains.
.
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16,759A-F -6-
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