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Патент USA US3026273

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United States Patent O?ice
3,026,263
Patented Mar. 20, 1962
1
2
3,026,263
elevated temperatures. It is a further object of this in
vention to improve the stability of mechanical ?uids so
that said ?uids, when utilized at high temperatures, re
?ect a minimum change in viscosity, a minimum corrod
HIGH TEMPERATURE MECHANICAL
FLUID COMPOSITIONS
Fred S. Arimoto, 'Newark, Del., assignor to 'E. I. du
Pont de Nemours and Company, Wilmington, Del., a
corporation of Delaware
No Drawing. Filed Mar. 5, 1959, Ser. No. 797,326
4 Claims. (Cl. 252-50)
This invention is directed to improved antioxidant
compositions for use in mechanical ?uids at elevated tem
peratures; and, more particularly, an N-aryl-Z-naphthyl
amine or an acridine in combination with selected poly
ing of metals, and a'minimum deposition of sludge. These
objects are achieved by treating the mechanical ?uid with
a small amount of an acridine or an N-aryl-Z-naphthyl
amine in combination with a small amount of a poly
nuclear hydrocarbon such as anthracene, chrysene, or
10 pyrcne; a synergistic effect is achieved in this combina
tion of agents. These and other objects will become ap
parent in the following description and claims.
More speci?cally, the present invention is directed to a
mechanical ?uid for use at 300° F. and above, said ?uid
nuclear aromatic hydrocarbons as a stabilizing agent. 15 containing an antioxidant composition of an N-aryl-2
Mechanical ?uids are those ?uids adaptable for use as
naphthylamine or an acridine and a polynuclear aro
lubricants, heat transfer agents, power transmission agents,
hydraulic ?uids and the like. The polynuclear aromatic
matic hydrocarbon having at least three fused rings and
whose singlet-triplet excitation energy is less than 20,
hydrocarbons are selected from the group that has at least
000 cmr-l.
three fused rings and a singlet-triplet excitation energy 20
This invention contemplates a mechanical ?uid con
less than 20,000 cm.-1 and are represented by such com~
taining one of the described and claimed novel combina
pounds as anthracene, benzanthracene, chrysene, pyrene.
tions of antioxidants in an amount within the range of
The singlet-triplet excitation energy for a number of aro
0.025% to 2.5% by weight of ?uid for each component
matic hydrocarbons is given in the Journal of the Ameri
of said combination.
can Chemical Society, vol. 77, page 1949 (1955). This 25
Mechanical ?uids suitable for use as lubricants may be
invention also deals with the stabilization of mechanical
the ester or silicone oil type represented by bis(2-ethyl
?uids against the deleterious effects of heat and oxygen
hexyl)sebacate, tetrabutyl pyromellitate, tetrakis (1H,1H,
at elevated temperatures.
wH-poly?uoroalkyl) pyromellitate (alkyl=C5 and C7),
Untreated mechanical ?uids, such as the esters and
pentaerythritol tetrapivalate, and DC-550 silicone oil.
silicone oils, that are adapted for use at 300° F. and 30 The lubricant must be adapted for use at elevated tem
above absorb oxygen at these elevated temperatures and
peratures; that is, it must have a low vapor pressure and
undergo undesirable changes. The combination of heat
and oxygen, for example, causes the ?uids to undergo an
be stable enough with the protection that the combina
tions of stabilizing agents provide to be used at tempera
increase in viscosity. In some ?uids, however, the vis
tures in the range of 500° F.
cosity may decrease which is also undesirable. These 35
The synergistic combinations of the antioxidants of this
oxidized ?uids may become corrosive to metals. This
condition limits the kinds of metal that may be used
invention are speci?c in their effectiveness as illustrated in
Table I and are particularly valuable for protecting ?uids
in contact with the ?uid and may cause failure or
of the ester and silicone oil types against the damaging
troublesome operation of such metal parts. The deposi
effects of heat and oxygen at temperatures from 300° F.
tion of sludge is another condition that arises when these 40 and above. These temperatures are commonly encount
?uids are subjected to thermal and oxidative stresses.
Numerous stabilizing agents have been applied to over
come or to suppress the changes encountered in mechani
ered in the ester type lubricants used in the bearings of
gas turbine engines and may be reached by the ester
compounds used as hydraulic ?uids. Representative com
binations of agents that exhibit signi?cant synergism are
cal ?uids at elevated temperatures. Many of the agents
have a stabilizing action at mildly elevated temperatures; 45 acridine and pyrene, anthracene and N-phenyl-Z-naphthyl
but above 300° F. and particularly around 500° F., agents
amine, and N-phenyl-Z-naphthylamine and pyrene. The
that are stabilizers at lower temperatures may lose their
preferred combination is acridine and pyrene.
effectiveness, actually promote oxidation and become pro
To illustrate the improvement of the esters and silicone
oxidants. One such agent is phenothiazine. Phenothi
oils in their resistance to oxygen absorption and to vis
50
azine is commonly used as an antioxidant in synthetic
cosity change and in the reduction of their corrosion of
lubricants designed for use at high temperatures in air
metals at elevated temperatures, the following examples
craft gas turbines. Its usefulness, however, is limited
of the marked effect of the combinations of selected sta
because at about 400° F., and at higher temperatures,
bilizing agents are given. The examples are preceded by
phenothiazine accelerates oxidation thereby promoting the
a description of the test apparatus and procedure, and
degradation of the lubricant and causing heavy amounts
part of the test results are presented in tables.
of sludge to form.
In determining the effect of heat and oxygen at elevated
It is an object of the present invention to provide novel
temperatures on mechanical ?uids, and, measuring the
stabilizing agents that are eifective, at elevated tempera
stabilizing action of antioxidants under these conditions,
tures, to retard undesirable changes a mechanical ?uid
a 20 mm. glass tube of 25 ml. capacity, rounded on the
may undergo on exposure to heat and oxygen; the changes 60 bottom and sealed at the top with a ground glass joint,
retarded include a change in viscosity, the formation and
was utilized. The glass joint bears a 5 mm. open glass
deposition of sludge and the development of corrosive
tube that extends almost to the bottom of a 20 mm. tube
action on metals. it is another object of this invention
or oxidation cell; from the glass joint also extends a side
to inhibit the oxygen absorption of mechanical ?uids at
outlet tube; this side outlet tube is connected in series
3,026,263
3
35
with a U-tube containing anhydrous calcium sulfate as a
lowing examples, substantially the same effectiveness being
achieved.
The following represent preferred combinations of the
antioxidants of the present invention:
Water-absorbent material, a U-tube containing ‘asbestos
?akes impregnated with sodium hydroxide as a carbon
dioxide absorbent material, an acetone/solid carbon di
oxide trap for condensing volatile oxidation products, a
small pump to circulate oxygen in the closed system, and
N-phenyl-Z-naphthylamine with anthracene
N-phenyl-Z-naphthylamine with pyrene
N-phenyl-Z-naphthylamine with chrysene
a rotameter to measure the rate of flow of oxygen. A gas
burette of oxygen and thermobarometer to compensate for
temperature and pressure changes are connected in series
Acridine with anthracene
Acridine With chrysene
Acridine with pyrene
with each other and as a side branch to the oxygen ab
sorption system.
To measure the oxidation of a mechanical ?uid, the
effects of heat and oxygen on the ?uid, and the stabilizing
e?ect of an agent or combination of agents, a 10 ml. or
20 m1. sample of'?uid, with and Without an added agent
to be tested, is placed in the oxidation cell and the cell
connected to the assembled apparatus through the ground
‘glass joint. The burette is ?lled with oxygen, and the sys
tem temporarily open to the air through a stop-cock is
?ushed with oxygen. After testing for leaks (by observ~ -
The novel antioxidant compositions of the present in
vention may be prepared and sold in mechanical ?uids for
use at high temperatures; these novel compositions may
also be sold as semi-re?ned products containing some sub
stantial quantities of the antioxidants. It is to be under
stood that mixtures of these antioxidants may be prepared
and that said mixtures may contain minor amounts of inert
material.
‘
Representative examples illustrating the present inven
ing if the system will maintain a pressure of 10 to 20 mm.
tion are as follows.
of mercury above that of the atmosphere for ?ve minutes
EXAMPLE 1
The effect on the rate of oxygen absorption by bis(2
ethylhexyl) .sebacate and on its viscosity increase in three
hours at 500° F. in the absenceand presence of selected
"antioxidants‘and-combinations ofantioxidants isshown in
Table I.
without change) and being sure there are none the oxy
gen pressure is equalized to that of the atmosphere. The
pump is started, and the oxygen ?ow is set at 25 mL/min.
by adjusting the stopcock on the outlet side of the pump.
A Woods metal bath at the desired temperature, say 500°
F., is raised around the oxidation cell. The oxygen
Table I
OXIDATION OF ,BIS(2-E.THYLHEXYL) SEBACATEI
[20 ml. sample at 500° F., oxygen at 25 1111./Illi11.]
Viscosity
No.
Agent Tested
Total
AmtqvPereent
Oxygen
Ave, for
Absorbed
Ave. for
Oxygen
Ab-
by'Weight
lst'hr.
3rd hr.
sot-bed
mL/rnin.
ml./1nin.
1n 3‘{1rs.
Relative Oxi-
dation Rate
Increase in
percent
measured
at ° F.
m .
1st
hr.
None ________________________________________________ _.
100
1. as
456
1
1
_ _ . . . _ __
0.5
2.05
1. 30
308
0.65
0.73
Anthracene..Chrysene ________________ _.
______ __
0.5
0.5
2. 29
3.40
1. 62
2.48
395
513
.75
1.07
.87
1.34
27
17
0.5
2. 00
1.68
369
.82
90
27
27
Pyrene ___________ __
0.5
2.86
2. 47
460
.90
1 as
1s
2s
Acridine + anthrac
0. 25+0. 25
1. 37
.71
186
.43
- Aeridine + DYreneAcridine + pwene-.-
22
210
Acridine _ . . _ . .
N-Phenybznaphthylumiue
3.17
2nd
111‘.
2s
__________ __
26
s
_.
0. 025+0.o25
0 ‘05+0. 05
2. 33
1. 00
1.59
0.71
344
188
.74
.31
Acridine + pyrene __________________ __
2. 5+2. 5
2. 21
1.45
335
.70
0. 25+0. 25
1.71
1. 33
‘262
.54
0. 25-1-0. 25
2.04
1.33
298
.64
.71
11
19
0.25+0.25
1. 69
1.30
292
. 53
.70
14
21
Anthracene + N-phenyl-fZ-napht'nylarmne.
Ohryseue + N-phenyl-2-naphthylam 1'19.
N-phlenyl-2-naphthylamine + pyrene.
burette is read every ?ve minutes for three hours. The
The combinations of acridine and anthracene (No. 7),
burette is re?lled with oxygen as necessary through a stopacridine and pyrene (particularly No. 8b) anthracene
cock. To measure the viscosity change in a ?uid under 55 and N-phenyl-Z-naphthylamine (No. 9), chrysene and N.
the test conditions, the material before and after oxida~
phenyl-Z-naphthylamine (No. .10), and N-phenyl-Z-naph
tion is permitted to ?ow through a calibrated modi?ed
thylamine and pyrene (No. 11) markedly retard the rate
Ostwald viscosimeter (ASTM procedure D445-46T). To
of oxidation of ,bis(2-ethylhexyl) sebacate and de?nitely
determine the corrosive action of an oxidized ?uid at elereduce its viscosity increase under these oxidizing condi
vated temperatures metal sheet or foil test pieces about one 60 tions. Thus these combinations of agents are distinct
inch square are immersed in the ?uid to be oxidized and
stabilizers for the ester at the elevated temperature. The
measured for Weight loss after the test.
same agents'used alone (Nos. 2, 3, 4, 5, 6) in an amount
vIn the representative examples which follow, the followequal to that of the total amount of the combination
ing alkyl and benz SLlbStitUt?d acridine compounds as 3stabilize the ester much less than when used in a proper
methylacridine, 2,7-dimethylacridine, 2,4,5,7—tetramethyl- 65 combination and may'actually promote ‘oxidation, chrys
ac'ridine, benzEalacridine, lO-methylbenz[a]acridine, 8,9-
ene, for example (No.4).
dimethylbenzta]
acridine, 8 ’ 9 ’ 12-trimethvlbenz[a]
acridine,.
. .
. 3
'
benz[c]acr1d1ne, 9-methylbenzilclacnd1ne, and 10,].1-d1-
'
methylbenz[c]acridine may be substituted for the acricline
''
PL
.
‘
EXAM
E 2
'
The combinations of anthracene and hl-phenyl-Z-naph
component to give substantially the'saine desired results 70 thylamine and of N-phenyl-Znapthylarmne and pyrene
as those achieved with acridine per se.
,
' I
'
eifectivel-y retard the oxidation. and viscosity changes of
It is also to be understood that N-aryl-Z-naphthylamine,
rtetra‘kis(1H,1H,wH-polyiluoroall<yl) pyromellitate that is
such as N1o-tOlyLZ-naphthylamine, N-2-naphthyl-2-naph-
‘ subjected'to'contact with oxygen at elevated temperatures.
thylamine and N-9~anthranyl-2-haphthylamine may be
This .poly?uoroalkyl ester has an alkyl group that is a
substituted for the N-phenyl-l-naphthylamine of the fol- 75 mixture of C5 and C7 atom chains. On'being oxidized
6
as described above at 572° F. and at 662° F. the re
oxidized with recirculated oxygen are presented in Table
IV.
sults recorded in Table II were obtained.
Table II
OXIDATION or TETRAKIS (1H, wH, kH-POLYFLUOROALKYL) PYROMELLITA'I‘E
[10 ml. ester]
A. TEMPERATURE, 572° F.
Oxygen Absorbed
Amt, per>
cent by
Agent Tested
Ave. for
Weight
Ave. for
Viscosity
Total
1st hr.,
2nd hr.,
in 3
rnL/rnin.
ml./min.
hrs.,
ml.
Change in per
cent: Measured
at °
100 ,
210
None __________________________________________________ ..
2.32
0. G3
170
-31
.tnthracene and N phenyl-2-naphthylamine-
0. 25+. 25
0. 05
. 08
9
~7
-—0
N#Pheuyl~2-naphthylan1ine and pyrene_-..
0. 25+O. 25
0.07
.04
8
—7
~28
+1
2. 70
. 50
186
70
.47
. 17
B. TEMPERATURE, 662° F.
None ___________________________________________________ -_
N-Phenyl-2-naphthylamine and pyrene- .._-
0. 25+0. 25
EXAMPLE 3
47 .ni“.
30
2.r
+——5)
Table IV
A combination of acridine and pyrene retards the increase in viscosity and the corrosion of metals in tetra-
OXIDATION OF DC-55U SILICONE 01L
[20 ml. sample at572°F., oxygen n25 mL/mirL]
butyl pyromellitate through which air is bubbled at 500“
This oxidation corrosion test is a standard procedure
F.
Viscosity
‘
(Federal Test_Method Standard No. 791, Method 5308.4)
used for qualifying lubricants under MIL-L-9236 speci.
?cation.
'
‘
Aeent’I‘ested
.
The test results are summarized in Table III.
Amount
Pelrfent
y
Weight
Oxygen
Absm'beéi, measolired
m . in
at
hours
Table III
100
OXIDATION OF TETRABUTYL PYROMELLITATE
Esterplus
Control (NO
025% Am?
added agent)
dine and
025%pyrene
_
4;)
_
‘
d
‘71251005?’ pelcem mcmdse measme at
‘I
210
40
[100 m1. sample at 500° F., air flow at 83 ml./mi11.]
_
increase
in percent
None ______________________________________ _.
97. 4
Anthracene and N-phenyl-2
Anaphthylamine ______________ _. 0.25+0.2§
21
15
cridme and pyrene ___________ __ 0.25+0~2e
29.4
5-7
3.1
15-0
4-5
21
As many apparently Widely different embodiments of
.
.
.
.
.
this Invention may be made ‘without departing from the
392
0 on
10: 0;
8.32
74
spirit and scope thereof, it is to be underestood that this
invention is not limited to the speci?c embodiments there
+21%
of except as de?ned in the appended claims.
+8.8; 50
The embodiments of the invention in which an ex
0 04
+0104
elusive property or privilege is claimed are de?ned as
o 05
+0. 04
follows:
EXAMPLE 4
Anthracene (0.25 part) and N-phenyl-Z-naphthylamine
(0.25 part) added to 100 parts of pentaerythritol tetra
pivalate so retards oxidation at 500° F. when oxygen
is bubbled through a 10 ml. sample of the ester in the
1. A high temperature mechanical ?uid selected from
the group consisting of esters and silicone oils, said fluid
containing an antioxidant composition of a component
selected from the group consisting of an N - aryl-2
naphthylamine and an acridine, in combination with a
polynuclear aromatic hydrocarbon component having at
least three fused rings said polynuclear aromatic hydro
apparatus and by the procedure described for the tests
with bis(2-ethylhexyl) sebacate summarized in Table I 60 canbon being. selected from the group consisting of
anthracene, benzanthracene, chrysene and pyrene, the
that only 8 ml. of oxygen are absorbed in three hours
singlet~triplet
excitation energy of said hydrocarbon be
whereas the untreated ester absorbs 87 ml. of oxygen in
ing less than 20,000 cmfl, each of said antioxidant com
the same time. The viscosity at 100° F. of the treated
ponents being present in an amount within the range of
ester increases from 298 centistokes before oxidation to
0.025% to 2.5% by Weight of said mechanical ?uid.
65
only 312 centipoises or 5% after the oxidation while the
2. A high temperature mechanical fluid according to
viscosity of the untreated control sample increases to 410
claim 1 wherein the antioxidant composition is a com
bination of acridine and pyrene.
centistokes or 38%.
EXAMPLE 5
3. An antioxidant composition for high temperature
The effect of acridine and pyrene in combination and 70 mechanical ?uids selected from the group consisting of
esters and silicone oils, said composition consisting of
of anthracene and N-phenyl-Z-naphthylamine used to
gether in a methyl phenyl silicone (DC-550 silicone oil)
a component selected from the group consisting of an
N-aryl-Z-naphthylamine and an acridine, together with
is marked in retarding oxidation at 572° F. and in sup~
a polynuolear aromatic hydrocarbon component having
pressing an increase in viscosity in the oil. The results
of oxidizing the silicone oil as the esterlubes have been 75 at least three fused rings, said polynuclear aromatic
"3,026,268
7
hydrocarbon vbeing selected from the group consisting of '
anthracene, benzanthnacene, ch-rysene and pyrene, vthe
singlet-triplet excitation energy of said hydrocarbon be
ing less than 20,000 cmrl' the proportion of said com
ponents being in equal parts by weight and each of said
components being present in an amount to achieve a con
centration in said mechanical fiuid within the range of
0.025% to 2.5% by Weight of said ?uid.
vReferences Cited in the ?le of this patent
UNITED’ STATES PATENTS
1,904,433
1,918,593
2,339,796
2,427,766
wherein said composition is a combination of acridine 10
and pyrene.
7 ’
FOREIGN PATENTS
,
4. An antioxidant composition according to claim
1933
1933
‘Musher ____________ __ Jan. 25, 1944
Diamond ____________ __ Sept. 23, 1947
Fischer et a1. ________ __ Apr. 18,
Dow ________________ __ July 18,
809,360
845,193
Great Britain ________ __ Feb. 25,
France _______________ __ May 8,
1959
1939
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