Note: Descriptions are shown in the official language in which they were submitted.
1073440
This invention relates to improved synthetic
phosphate ester functional fluids particularly
suitable for use as lubricants, hydraulic fluids
and the like. More particularly, the invention
relates to triaryl phosphate ester functional fluid
compositions derived from mixtures of tertiary-butyl- .
phenols and phenol which exhibit a high degree of
resistance to oxidative and thermal degradation.
Triaryl phosphates and mixed alkylphenyl/phenyl
phosphates are known and are described, for example,
in U.S. Patent 3,576,923, issued April 27, 1971 to
Randell et al. Synthetic functional fluids and
lubricants containing triaryl phosphates of various
types may be found in U.S. Patents 2,938,871 issued
May 21, 1960 to MatuszaK; 3,012,057 issued December 5, =-
1961 to Fierce et al; 3,071,549 issued January 1, 1963
to Stark; 3,468,802 issued September 23, 1969 to
Nail; 3,723,315 issued March 27, 1973 to Sullivan
and 3,780,145 issued December 18, 1973 to Malec.
The present invention is based on the discovery
that phosphorylated mixtures of tertiary-butylphenols
and phenol provide triaryl phosphate ester functional
fluids which exhibit heretofore unrecognized thermal
and oxidation stability which render such triaryl
phosphate esters particularly suitable for use in the
formulatlon of functional fluids such as lubricants,
particularly turbine lubricants, hydraulic fluids
. . .
1073440
and the like where extreme conditions such as hlgh
temperatures or extended periods of use require fluids
of unusual stability properties.
In accordance with the present invention, there
are provided functional fluid compositions comprising
95 to 99.99% by weight of a mixed tertiary-butylphenyl/
phenyl phosphate containing between about 15 to 60%,
preferably 30 to 50%, by weight mono-t-butylphenyl
radicals or mixtures thereof with di-t-butylphenyl radicals,
the di-t-butylphenyl radicals being present in an amount
between about 1 to 10% by weight based on the weight of
the mono-t-butylphenyl radicals, as the base stock, and
in admixture with the base stock, of very minor amounts,
about 0.1 to 5% by weight, of lubricant additives such
as rust inhibitors, corrosion inhibitors, anti-foam
agents, anti-wear agents, cavitation inhibitors and
similar special purpose additives.
The mixed t-butylphenyl/phenyl phosphates of the
present invention may be represented by the general
formula (R0) 3PO where R represents radicals consisting
of (a) about 15 to 60% by weight of mono-t-butylphenyl
radicals or mixtures of mono-t-butylphenyl and di-t-
butylphenyl radicals, from about 1 to 10% by weight of
such mixtures being di-t-butylphenyl radicals and (b)
about 85 to 40% by weight of phenyl radicals. Preferred
are those mixed t-butylphenyl/phenyl phosphates wherein
the R radicals consist of about 30 to 50% mono-t-butyl-
phenyl radicals or mixtures of same with di-t-butylphenyl
radicals, the mixtures containing 2% or less di-t-butyl-
phenyl radi-cals and the balance of the R radicals are
.
, .. :
1~73440
phenyl radicals. Rust and corrosion inhibitors commonly
employed are compounds such as benzothiazole, benzotri- ,
azole, triethanolamine, phenothiazine, trialkyl phosphates,
such as mixed mono- and dialkyl phosphates, N-acyl
sarcosines, the acyl radical having 10 to 18 carbon
atoms, propyl gallate, succinic acid and alkyl succinic
acids. Other additives to inhibit foaming and cavitation -
included organo-silicone compounds, dialkyl carboxylic
acid esters, such as diethyl succinate or dioctyl
sebacate, or lower alkanes such as butane, propane and
isomers thereof.
Functional fluids formulated in accordance with
the present invention which contain a mixed tertiary
butylphenyl/phenyl phosphate as the base stock with
small proportions of the specialty additives described
above are particularly suitable for high temperature
use appllcations, since they exhibit a kinematic
viscosity stability of +5% when subjected to temperatures
within the range of 175C to 220C for a period of 72
hours.
Particularly preferred embodiments are functional
fluid formulations which consist essentially of a mixed
t-butylphenyl/phenyl phosphate, the formulation containing
0.01 to 0.1% by weight of a member selected from the
group of additives consisting of benzotriazole, N-oleoyl
sarcosine, or a mixed mono- and dialkyl phosphate of the
formula RH2PO4 and R2HPO4, the alkyl being C~-Cl2 and
mixtures of these additives. These formulated compo-
sitions may also contain very small proportions, that is,
about 0.001%, of a silicone anti-foam agent, such as
. .
- ~073440
a dimethyl silicone polymer. These formulated compo- '
sitions are highly significant in that they offer the
desirable combined properties of oxidative stability
at elevated temperatures, thereby eliminating the need
for antioxidant additives, and excellent corrosion and
rust resistance, which enable functional fluids pre-
pared in accordance with the present invention to meet
the most demanding commercial specifications.
Apparently, there are no commercially avail-
able triaryl phosphate ester-based formulations which
offer the,se combined properties. The remarkable
stability of the compositions of the present invention
at high temperatures is shown by their relatively un-
, changed viscosity and acid number when compared withother available phosphate ester fluids.
A further embodiment of the present invention re- ,
sides in thermally and oxidatively stable mixed
functional fluids comprising 10 to 90% by weight of a
mixed tertiary-butylphenyl/phenyl phosphate as herein-
before described and 90 to 10% by weight of anotherfluid composition useful in formulating functional
fluids. Thus, mixtures may be prepared with other
functional fluids such as the synthetic or natural
hydrocarbon oils, halogenated aromatic hydrocarbons,
organic esters such as the alkanoic acid esters of
organic polyhydroxy compounds such as pentaerythritol,
trimethylolethane and trimethylolpropane, neopentyl
glycol esters and the like, the alkanoic acids
generally having from about 5 to 10 carbon atoms.
Also suitable for formulating such mixtures are other
--4--
- : . .... : .,
1073440
phosphate ester functional fluids such as trialkyl
phosphates, triaryl phosphates, alkyl substituted
triaryl phosphates, other mixed alkyl phenyl/phenyl
phosphates, with the foregoing phosphate esters being
exemplified by tricresyl phosphate, tritolyl phosphate,
trixylenyl phosphate, cresyl diphenyl phosphate, di-
phenyl ethylphenyl phosphate, butyl diphenyl phosphate,
dicresyl xylyl phosphate, dibutyl phenyl phosphate,
tributyl phosphate, triamyl phosphate, trioctyl
phosphate, mixed isopropylphenyl/phenyl phosphates,
such as those prepared by phosphorylating an isopropyl-
phenol/phenol mixture prepared by alkylating phenol
with 10 to 40% by weight of propylene.
Other functional fluids useful for formulating ~-
mixtures include the alkoxypolysiloxane and organo
polysiloxane fluids such as dimethylpolysiloxane,
methylphenylpolysiloxane, dimethyldiphenylpolysiloxanes,
methyl alkyl silicone fluids, siloxane esters, poly-
phenyl ethers such as bis(m-phenoxyphenyl) ether, di-
phenoxy biphenyl isomers, alkoxy aromatic ethers, poly-
glycols such as polyalkylene glycols and polyoxyalkylene
glycols, silicate esters, such as tetraalkyl, tetraaryl
and mixed alkylaryl orthosilicate esters.
Particularly useful are oxidatively stable
functional fluid compositions comprising 40 to 60% by
weight of a mixed tertiary-butylphenyl~phenyl phosphate
ester and 60 to 40% of a functional fluid selected
from the group consisting of aliphatic or aromatic
petroleum hydrocarbons of lubricating viscosity, a
silicone functional fluid, a polyol alkanoic acid
1~73440
ester .functional fluid, particularly a pentaerythrltol
ester, or other phosphate ester functional fluids as
described above.
The mixed t-butylphenyl/phenyl phosphate ester
fluids of the present invention, when formulated with
the other useful functional fluids noted above, may
require the presence of minor proportions of a co-
solvent or coupling agent to render such fluids com-
patible. Generally speaking, the phosphate esters use-
ful in preparing the compositions of the present in-
vention will generally be compatible and miscible
with aromatic petroleum hydrocarbons, alkanoic acid
ester functional fluids, other phosphate ester fluids,
polyalkylene glycol fluids and the like. For formu-
lation with other types of functional fluids such as
the silicones, siloxanes, silicate esters, aliphatic
hydrocarbons and similar fluids, the use in minor
amounts, approximately 5 to 15~ by weight of the
formulation, of couplers and co-solvents such as mono-
hydric and polyhydric alcohols, polyalkylene glycols,ethylene glycol ethers, polyphenyl ethers, trialkyl
phosphates, and the like, may be required.
The compositions of the present invention be-
cause of their excellent stability at very high tempera-
tures, are particularly suitable for use in applications
wherein high use temperatures are routinely encountered
such as in the lubrication of gas turbines, particularly
aero gas turbines, power generating gas turbines, steam
turbines and the like. Fluids formulated in accordance
with the present invention containing the mixed t-butyl-
1073440
phenyl/phenyl phosphate esters described hereln arealso especially suitable for use as hydraulic fluids,
capacitator and transformer oils as well as for heat
transfer fluids. In these applications, a high degree
of oxidative stability is of importance. Since anti-
oxidant additives are not present, filtration of such
fluids in the course of their use for the purpose of
removing impurities will not diminish their stability.
A further embodiment of the present invention re-
sides in a method of lubricating metallic surfaces
in frictional contact at elevated temperatures, that -
is, in excess of about 50C, comprising applying to
said metallic surfaces a lubricating composition con- ~
sisting essentially of an oxidatively stable phosphate -
triester, said triester being a liquid mixed t-butyl-
phenyl/phenyl phosphate containing about 15 to 60% of
mono-t-butylphenyl radicals, or mixtures of mono-t-
butylphenyl radicals and di-t-butylphenyl radicals,
the di-t-butylphenyl radicals being present in such
20 mixtures in an amount between about 1 to 10% by weight -~
based on the weight of the mono-t-butylphenyl radicals
or admixtures of said t-butylphenyl/phenyl phosphates
with another fluid useful for formulating functional
fluids as hereinbefore described. Mixed t-butylphenyl/
phenyl phosphates are particularly suitable for
lubrication at high temperatures of metals present in
the gears and bearings of a gas turbine such as
copper, magnesium,-iron, steel, aluminum, silver and
lead. Temperatures in the range of 50C to 400C are
commonplace in the operation of steam and gas turbines.
7--
: :: ; ' `. ; -
~073440
.
The compositions of the present invention are particularly
suitable for lubricating at temperatures in excess
of about 175C, because of their resistance to thermal
degradation at these high temperatures.
The tertiary-butylphenyl/phenyl phosphates described
herein also exhibit good extreme pressure and antl-wear
properties. This property, in combination with their
unusual degree of thermal stability, renders these
materials particularly suitable for use in very minor
amounts as additives for other functional fluids to
improve the lubricating properties thereof. As special
purpose additives, they may be added in amounts between
about 0.1 to 5% by weight, based on the weight of the
functional fluid. Thus, they may be employed as
additives preferably for functional fluids such as
the polyol alkanoic acid esters, the silicone fluids,
natural and synthetic hydrocarbon oils as well as other
useful functional fluids hereinbefore described. They
function as suitable anti-wear or extreme pressure
additives and offer the additional advantage of superior
resistance to thermal and oxidative deterioration. -
The mixed t-butylphenyl/phenyl phosphate esters ;
may be prepared by any suitable conventional technique,
and preferably by phosphorylation of an isobutylene-
phenol alkylation mixture prepared by alkylating phenol
with from 10 to 40% by weight of isobutylene as disclosed,
for example, in U.S. Patent 3,576,923 which results
in a complex mixture of mono- and di-t-butylphenols and
phenol. Alternatively~ appropriate mixtures of one or
more isomeric t-butylphenols and phenol may be
1073440
phosph~rylated to produce the mlxed t-butylphenyl/phenyl
phosphate ror use in accordance wlth the present
inventlon .
The followlng Examples are provided to further
lllustrate this lnvention. The proportions ln the
Examples and ln the rest of the speclflcation are
by welght and the temperatures are ~n degrees centl-
grade unless otherwlse lndicated.
EXAMPLE I
The preparation Or mlxed t-butylphenyl/phenyl
phosphate ester fluids is set forth in the following
Examples l(a) to l(f). Properties of the varlous
mixed t-butylphenyl/phenyl phosphate triesters are -
set forth in Table 1.
(a) Into a stlrred suspenslon of dried acid
activated clay catalyst~ sold as "Super Filtrol", (75 ~
g, 2.0% by wt.) in phenol (3,765 g, 40 moles) was ~ ~-
bubbled lsobutylene (664.4 g, 11.8 moles) at 80C.
Aluminum chloride (44 g, 1.0% by wt.) was added to
20 the stirred suspension and the temperature was in- -
creased to 118 when the addition of phosphorus oxy-
chloride (2,037 g, 13.0 moles) began. The addltion
required 3.0 hours as the temperature was gradually
increased to 220 where it was mainta~ned for an
additional 3.0 hours after the addition. The hydrogen
chloride which evolved was swept out of the system
with nitrogen into a scrubber.
Without filtering the catalysts, the product
was flash distilled out of the reactor. The main
fractlon (4.062 g, 81%) boiled 180 to 230 at 0.4 torr.
- -_ g_
* Trade Mark
~'
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.,
1073440
Redistlrlatlon through a 12" Goodloe column ln the
presence o~ 1.0% by wt. Or sodlum carbonate provlded
3,990 grams ( 80% ) of t-butylated phenyl/phenyl phosphates
whlch boiled at 195 to 235 at 0. 4 torr.
(b) Using a process analogous to that ln Example
l(a), phenol (4,220 g, 44.8 moles) and isobutylene
(469 g, 8.38 moles) were reacted in the presence of
~uper Filtrol. The phosphorylation was similar except
anhydrous magnesium chloride (1.0% by wt.) was used.
Distillation afrorded 4,714 grams (88%~ of t-butylated
phenyl/phenyl phosphates which boiled at 195 to 220
at 0.25 torr.
(c) Using a process analogous to that in Example
l(a), phenol (3,764 g, 40 moles) was reacted with 941 - -
grams (16. 8 moles) of isobutylene. Phosphorylation
and distillation afforded 4,856 grams (92%) of product
which boiled at 210 to 240 at 0.15 torr.
(d) Phenol (2,069 g, 22.0 moles) and isobutylene
(454 g, 8.1 moles? were reacted and phosphorylated in a
manner as described in Example l(a).
(e) To a stirred solution (70) of phenol (2,760
g, 29.6 moles) and p-t-butylphenol (1,800 g, 12.0 moles)
was added 2,195 grams (14.3 moles) of POCl3 in the
presence of MgCl2 (30 g, 0.5% by wt.). The remainder
of the preparation was carried out in an analogous
manner as described in Example l(a) to yield 5,140
grams ( 94% ) Or triester.
(f) An alkylate prepared in an analogous manner
to that described in Example l(a) was transalkylated
by heating in a sealed system at 130 for 3. 5 hours
* Trade Mark
,
1073440
in the.presence of 2.0% by wt. of Super Filtrol catalyst.
Comparative analyses before and after this treatment
are given below.
Phenols - % by weight
PhenoI ortho meta/para 2 4-di
Alkylate Or Ex. l(a) 59.80 8.84 25.21 6.07
Transalkylated
product5~.80 2.91 40.8 0.39
Phosphorylation of the transalkylated product as de-
scribed in Example l(a) produced 2,870 grams (90~)
which boiled at 190 to 240~ at 0.1 torr.
(g) Alkylate from Example l(d) was transalkylated
in a simllar manner to Example l(e). Comparative
analyses of the phenol dis'ributlon are agair set forth:
Phenols - % by weight
Phenol ortho meta/~ara 2 4-di
Alkylate of Ex. l(d) 52.80 7.09 35.50 4.47
Transalkylated -
product47.40 3.21 48.60 0.68
Phosphorylation and distillation afforded a phosphate
triester product.
E~AMPLE II
The mixed tertiary butyl substituted triaryl
phosphates prepared in Example 1 were evaluated for
oxidative stability and corrosivity according to
Federal Test Method Standard No. 791B Method 5308.6
l'Corrosiveness and Oxidation Stability of Light Oils".
Comparisons of the products of this invention with other
commercial triaryl phosphates via this procedure were
m de. The results of these evaluations are presented
in Table 2. The remarkable oxidative stability of the
mixed tertiary butyl substituted triaryl phosphates is
* Trade Mark
~.
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1073440
mani~estly apparent when comparing acid number changes
and viscosity differences with other triaryl phosphates.
The products were evaluated before and after exposure
to 175C for 72 hours.
EXAMPLE III
Evaluations of the oxidative stability of the
mixed tertiary butyl substituted triaryl phosphates
were made according to the MIL-L-23699B 3.3.10 military
specification at 204C and 218C after 72 hours, with
data for 204C reported in Table 3 and data for 218C
reported in Table 4. The viscosity stability at very
high temperatures is readily apparent.
EXAMPLE IV
The superior oxidative stability of the compounds
of this invention is not diminished by treatment with
additives known in the art to lnhibit metal corrosion, -
rusting and foaming. Results of evaluations of mixed
tertiary butyl substituted triaryl phosphates formulated
with a copper passivator (benzotriazole), rust inhibitors
- 20 (Sarkosyl O~ and Ortholeum 162~), a dimethyl silicone
anti-foam agent (Dow-Corning "Compound A"), antioxidants
and acid sumps (Kronox S~) are summarized in Tables
5 and 6. It is readily apparent from these results
that the extraordinary thermal and oxidative characteristics
of the compositions are maintained and their utility
enhanced as indicated by the ASTM D-665 rust test.
EXAMPLE V
This example demonstrates the superior oxidative
stability of mixtures of the phosphate esters of this
inventicn with alkanoic acid esters. The table below
-12-
~073440
compares the stablllty Or an unstabillzed 65%/35%
vol./vol. blend Or phosphate ester Or Example l(a)
and "Hatcol 1570~ with a similar 65%/35~ mixture o~
trlcresyl phosphate (TCP)/Hatcol 1570~ Hatcol 1570
ls a commercially available pentaerythritol alkanoic
acid (C~-CiO acids) ester. It is clearly evident that
by comparlson of the change ln viscoslty and acld
number the composition of this invention is signlficantly
more stable than the one based on TCP. The data are
set forth below. Corrosion results are also shown.
Federal Test Method Standard No. 791B~
Method 5308 ~ 6 at 175C for 72 Hours
Ex. l(a)~Eatcol TCP/~atcol 1570 r
570 (65%/35% ) (65%/35% )
~TAN* (mg/KOH/g) 6 ~ 60 11 ~ 9
% Viscosity Change29 ~ 0 54 ~ 0
(cs. at 100F)
Wt. Change (mg/cm2)
Cu -0 ~ 67 -0.18
Steel +0.01 ~0.01
Mg -0.01 -0.01
Al 0.00 0.00
Ag -o.o6 -0.0
*~TAN = Change in total acid number.
EXAMPLE VI
This example shows the enhanced oxidatlve
stability of mixtures of phosphate esters prepared
by adding the fluids of this invention to commercially
available phosphate esters. The improved oxidative
stability of the blended materials is readily apparent
in the data set forth below.
* Trade Mark
3W~6
~073440
Federal Test Method Standard
No. 791B, Method 5308.6 at
175/72 hrs.
- Composltion~ TAN*% Vlscosity Change
IPP* 26 102
TCP* 4.8 16
Ex. l(a) 0 5
Ex. l(a) (10~)/
IPP*(90%) 15.7 88
Ex. l(a) (50~)/
IPP*(50~) 2.7 14
Ex. l(a) (10%)/
TCP*(90%) 1.5 6
10 Ex. l(a) (50%)/
TCP*(50%) .5 3
Ex. l(a) (90%)/
TCP*(10%) .4 .8
*As defined in Table 2.
EXAMPLE VII
The extreme pressure and anti-wear characteristics
of the t-butylphenyl/phenyl phosphate ester fluids
of the present invention were evaluated as indicated ~
by the following 4-ball test data carried out at ~ -
80F +15F according to ASTM D-2596 (Load Wear Index
and Weld Point) and ASTM D-2266 (Wear Scar Diameter).
Sample _ASTM D-2596 ASTM D-2266
Load Wear Weld Point, Wear Scar ~ -
Index kg. Di2meter, mm.
Ex. l(a) 26.19 126 0.60
Ex. l(b) 26.03 126 0.60
Ex. l(d) 26.07 126 0.54 `~-
IPP* 24.43 126 0.5~ ~-
TCP* 24.75 126 0.57
CDP* 21.76 126 o.65
TXP* 26.27 126 0.54
*Same as Table 2.
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1073440
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