U.S. patent application number 15/841537 was filed with the patent office on 2018-06-28 for aircraft turbine oil base stock and method of making.
The applicant listed for this patent is ExxonMobil Research and Engineering Company. Invention is credited to Susan C. Ardito, Michael R. Douglass, Beth A. Fitch, Douglas E. Johnson.
Application Number | 20180179463 15/841537 |
Document ID | / |
Family ID | 60888753 |
Filed Date | 2018-06-28 |
United States Patent
Application |
20180179463 |
Kind Code |
A1 |
Douglass; Michael R. ; et
al. |
June 28, 2018 |
AIRCRAFT TURBINE OIL BASE STOCK AND METHOD OF MAKING
Abstract
Provided is a polyol ester base stock composition with reduced
odor and volatility. The polyol ester back stock composition does
not include C5 acid. More particularly, the polyol ester base stock
includes the reaction product of: (a) a polyol represented by the
formula R(OH).sub.n wherein R is an aliphatic or a cyclo-aliphatic
hydrocarbyl group and n is at least 2, and (b) a mixture of
monocarboxylic acids comprising at least one linear acid selected
from the group consisting of between C6 to C10 acids and at least
one branched C6 acid, wherein the amount of C6 to C10 acids is at
least 55 wt. % and the amount of the at least one branched C6 acid
is 45 wt. % or less, based upon the total amount of said mixture of
monocarboxylic acids. The polyol ester base stock is particularly
suited for aviation turbine oils.
Inventors: |
Douglass; Michael R.;
(Cherry Hill, NJ) ; Fitch; Beth A.; (Houston,
TX) ; Ardito; Susan C.; (Ocean, NJ) ; Johnson;
Douglas E.; (Tucson, AZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ExxonMobil Research and Engineering Company |
Annandale |
NJ |
US |
|
|
Family ID: |
60888753 |
Appl. No.: |
15/841537 |
Filed: |
December 14, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62437829 |
Dec 22, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10M 2203/1025 20130101;
C10N 2030/12 20130101; C10N 2020/02 20130101; C10M 105/38 20130101;
C10N 2030/74 20200501; C10M 2205/0285 20130101; C10M 2209/1033
20130101; C10M 2207/2835 20130101; C10N 2070/00 20130101; C10M
169/042 20130101; C10N 2030/10 20130101; C10M 2211/0445 20130101;
C10M 2229/025 20130101; C07C 69/33 20130101; C10M 169/04 20130101;
C10N 2030/02 20130101; C10N 2040/13 20130101; C10M 2207/2825
20130101; C10N 2020/069 20200501; C10M 2223/0405 20130101; C10M
2207/2835 20130101; C10M 2207/2835 20130101 |
International
Class: |
C10M 105/38 20060101
C10M105/38; C10M 169/04 20060101 C10M169/04 |
Claims
1. A polyol ester base stock comprising the reaction product of:
(a) a polyol represented by the formula R(OH).sub.n wherein R is an
aliphatic or a cyclo-aliphatic hydrocarbyl group and n is at least
2, and (b) a mixture of monocarboxylic acids comprising at least
one linear acid selected from the group consisting of between C6 to
C10 acids and optionally at least one branched C6 acid, wherein the
amount of C6 to C10 acids is at least 55 wt. % and the amount of
the optional at least one branched C6 acid is 45 wt. % or less,
based upon the total amount of said mixture of monocarboxylic
acids, and wherein the mixture of monocarboxylic acids is
substantially free of C5 acid.
2. The base stock of claim 1, wherein the hydrocarbyl group of the
polyol includes from 2 to 20 carbon atoms.
3. The base stock of claim 1, wherein the hydrocarbyl group
includes a substituent selected from the group consisting of
chlorine, nitrogen, oxygen and combinations thereof.
4. The base stock of claim 1, wherein the polyol is selected from
the group consisting of 2-ethyl-1,3-hexanediol,
2-propyl-3,3-heptanediol, 2-butyl-1,3-butanediol,
2,4-dimethyl-1,3-butanediol, neopentyl glycol, 2,2-dimethylol
butane, trimethylol ethane, trimethylol propane, trimethylol
butane, mono-pentaerythritol, technical grade pentaerythritol,
di-pentaerythritol, tri-pentaerythritol, ethylene glycol, propylene
glycol, polyalkylene glycols and combinations thereof.
5. The base stock of claim 4, wherein the polyalkylene glycol is
selected from the group consisting of polyethylene glycols,
polypropylene glycols, polybutylene glycols and combinations
thereof.
6. The base stock of claim 1, wherein the polyol comprises at least
di-pentaerythritol.
7. The base stock of claim 1, wherein said at least one C6 to C10
linear acid is selected from the group consisting of hexanoic acid,
heptanoic acid, caprylic acid, pelargonic acid and capric acid.
8. The base stock of claim 1, wherein said at least one C6 branched
acid is selected from the group consisting of: 2-methylpentanoic,
4-methylpentoic acid, and combinations thereof.
9. The base stock of claim 1, wherein said polyol comprises
technical pentaerythritol in an amount between about 50 to 100
weight %, based on the total polyol, and di-pentaerythritol in an
amount between about 0 to 50 weight %, based on the total
polyol.
10. The base stock of claim 1 including a linear C6 acid ranging
from 20 to 70 wt. % of the total amount of said mixture of
monocarboxylic acids.
11. The base stock of claim 1 including a linear C7 acid ranging
from 16 to 40 wt. % of the total amount of said mixture of
monocarboxylic acids.
12. The base stock of claim 1 including a linear C8-C10 acid
ranging from 14 to 25 wt. % of the total amount of said mixture of
monocarboxylic acids.
13. The base stock of claim 1, wherein the base stock has a
viscosity of at least 4 cSt at 100 degree C., a viscosity of less
than 11,000 cSt at -40 degree C., a viscosity index of at least
120, and a pour point of at least as low as -54 degree C.
14. An aircraft turbine oil comprising from 70 to 95 wt % of a
polyol ester base stock and from 1 to 15 wt. % of a lubricant
additive package, wherein the polyol ester base stock comprises the
reaction product of: (a) a polyol represented by the formula
R(OH).sub.n wherein R is an aliphatic or a cyclo-aliphatic
hydrocarbyl group and n is at least 2, and (b) a mixture of
monocarboxylic acids comprising at least one linear acid selected
from the group consisting of between C6 to C10 acids and at least
one branched C6 acid, wherein the amount of C6 to C10 acids is at
least 55 wt. % and the amount of the at least one branched C6 acid
is 45 wt. % or less, based upon the total amount of said mixture of
monocarboxylic acids, and wherein the mixture of monocarboxylic
acids is substantially free of C5 acid.
15. The turbine oil of claim 14, wherein the lubricant additive
package comprises at least one additive selected from the group
consisting of viscosity index improvers, corrosion inhibitors,
antioxidants, dispersants, anti-emulsifying agents, color
stabilizers, detergents and rust inhibitors, and pour point
depressants.
16. The turbine oil of claim 14, wherein turbine oil comprises a
blend of the polyol ester base stock and at least one additional
base stock selected from the group consisting of: mineral oils,
highly refined mineral oils, poly alpha olefins, polyalkylene
glycols, phosphate ester, silicone oils, diesters and polyol
ester.
17. The turbine oil of claim 14, wherein the turbine oil has an
evaporative weight loss at 204.degree. C. for 6.5 hours per ASTM
D972 of less than 3.2 wt. %.
18. The turbine oil of claim 14, wherein the turbine oil has a
TGA-simulated Noack volatility of less than 3.1 wt. %.
19. The turbine oil of claim 14, wherein the turbine oil has a
GC-simulated distillation at 10% weight loss temperature of greater
than 800 deg. F.
20. The turbine oil of claim 14, wherein the turbine oil has a
reduced odor during use in an aircraft turbine relative to a
comparable aircraft turbine oil including a C5 acid in the mixture
of monocarboxylic acids.
21. The turbine oil of claim 14, wherein the turbine oil meets
military specification MIL-L-23699G with a viscosity at 210 degree
F. (99 degree C.) of at least 5.0 cSt and at -40 degree C. of no
more than 13,000 cSt, and a pour point of less than at least -65
degree F. (-54 degree C.).
22. A method of making a polyol base stock comprising: esterifying
reaction mixture of a polyol represented by the formula R(OH).sub.n
wherein R is an aliphatic or a cyclo-aliphatic hydrocarbyl group
and n is at least 2 and an excess mixture of monocarboxylic acids
comprising at least one linear acid selected from the group
consisting of between C6 to C10 acids and optionally at least one
branched C6 acid, wherein the amount of C6 to C10 acids is at least
55 wt. % and the amount of the optional at least one branched C6
acid is 45 wt. % or less, based upon the total amount of said
mixture of monocarboxylic acids, and wherein the mixture of
monocarboxylic acids is substantially free of C5 acid, wherein the
esterification occurs with or without a sulfonic acid, phosphorus
acid, sulfonic acid, para-toluene sulfuric acid or titanium,
zirconium or tin-based catalyst, at a temperature in the range
between about 140 to 250 degree C. and a pressure in the range
between about 30 mm Hg to 760 mm Hg.
23. The method of claim 22 further comprising the step of adding an
adsorbent to said reaction mixture following esterification.
24. The method of claim 23, wherein said adsorbent is at least one
material selected from the group consisting of alumina, silica gel,
activated carbon, zeolites, clay and filter aid.
25. The method of claim 22 further comprising the steps of: adding
water and base to simultaneously neutralize the residual organic
and mineral acids and/or hydrolyze said catalyst; removing of said
water used in the hydrolysis step by heat and vacuum in a flash
step; filtering of solids from said ester mixture containing the
bulk of the excess acids used in the esterification reaction;
removing excess acids by steam stripping or any other distillation
method; and removing any residual solids from the stripped ester in
a final filtration.
26. The method of claim 22 wherein said at least one C6 to C10
linear acid is selected from the group consisting of: hexanoic
acid, heptanoic acid, caprylic acid, pelargonic acid and capric
acid.
27. The method of claim 22 wherein said at least one C6 branched
acid is selected from the group consisting of: 2-methylpentanoic,
4-methylpentoic acid, and combinations thereof.
28. The method of claim 22, wherein said polyol comprises technical
pentaerythritol in an amount between about 50 to 100 weight %,
based on the total polyol, and di-pentaerythritol in an amount
between about 0 to 50 weight %, based on the total polyol.
29. A method of reducing volatility and odor of an aircraft turbine
oil comprising: providing to an aircraft turbine an aircraft
turbine oil comprising from 70 to 95 wt % of a polyol ester base
stock and from 1 to 15 wt. % of a lubricant additive package,
wherein the polyol ester base stock comprises the reaction product
of: a) a polyol represented by the formula R(OH).sub.n wherein R is
an aliphatic or a cyclo-aliphatic hydrocarbyl group and n is at
least 2, and b) a mixture of monocarboxylic acids comprising at
least one linear acid selected from the group consisting of between
C6 to C10 acids and optionally at least one branched C6 acid,
wherein the amount of C6 to C10 acids is at least 55 wt. % and the
amount of the optional at least one branched C6 acid is 45 wt. % or
less, based upon the total amount of said mixture of monocarboxylic
acids, and wherein the mixture of monocarboxylic acids is
substantially free of C5 acid, wherein the turbine oil has an
evaporative weight loss at 204.degree. C. for 6.5 hours per ASTM
D972 of less than 3.2 wt. %, a TGA-simulated Noack volatility of
less than 3.1 wt. % and a GC-simulated distillation at 10% weight
loss temperature of greater than 800 deg. F., and reduced odor
during use in an aircraft turbine relative to a comparable aircraft
turbine oil including a C5 acid in the reaction mixture.
30. The method of claim 29 wherein the lubricant additive package
comprises at least one additive selected from the group consisting
of viscosity index improvers, corrosion inhibitors, antioxidants,
dispersants, anti-emulsifying agents, color stabilizers, detergents
and rust inhibitors, and pour point depressants.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application Ser. No. 62/437,829 filed Dec. 22, 2016, which is
herein incorporated by reference in its entirety.
FIELD
[0002] The present disclosure relates to the field of aircraft
turbine oils. It more particularly relates to aircraft turbine oil
base stocks and formulations including synthetic polyol ester base
to stocks. Still more particularly, the present disclosure relates
to aircraft turbine oil base stocks and formulations including
synthetic polyol ester base stocks that yield lower odor and
reduced volatility.
BACKGROUND
[0003] Lubricants in commercial use today are prepared from a
variety of natural and synthetic base stocks admixed with various
additive packages and solvents depending upon their intended
application. The base stocks typically include mineral oils, highly
refined mineral oils, poly alpha olefins (PAO), polyalkylene
glycols (PAG), phosphate esters, silicone esters, diesters and
polyol esters.
[0004] In end uses where higher stability is desired or required,
polyol esters have been commonly used due to their high thermal and
oxidative stability. One of the most demanding lubricant
applications in terms of thermal and oxidative requirements is oils
for aircraft turbines. In aircraft turbines, where operating
temperatures and exposure to oxygen are both high, it has been the
industry's practice to use polyol esters.
[0005] Generally, polyol esters used in forming aircraft turbine
oils typically include a mixture of monopentaerythritol and
dipentaerythritol esters. Still others have blended
trimethylolpropane esters and dipentaerythritol esters,
trimethylolpropane esters and monopentaerythritol/dipentaerythritol
esters, or a mixture of trimethylolpropane esters and
monopentaerythritol esters. More particularly, typical jet oil
ester basestocks include a mixture of C5-C10 carboxylic acids,
reacted with a polyol ester such as pentaerythritol or trimethylol
propane. C5 acids can typically be more than half of the acid
stream used to make jet oil ester base stocks. When these base
stocks hydrolyze in service, pentanoic acids are the most volatile
and also have an objectionable odor.
[0006] Every lubricant has a characteristic odor which is imparted
to it by the compositional changes which occur when used in an
engine. In particular, if there is any decomposition of the ester
component, it is expected that free carboxylic acid will be
generated. In general, hydrolysis of synthetic ester base stocks
containing significant amounts of lower molecular weight acid give
rise to decomposition products of greater odor intensity than those
containing lesser amounts of lower molecular weight acids. By lower
molecular weight acids is meant pentanoic acids and, to a lesser
extent, hexanoic acids which have five or six carbon atoms,
respectively. Further, both straight-chain and branched-chain acids
are included in this definition. This is true whether the lower
molecular weight acids are combined with trimethylolpropane,
monopentaerythritol or dipentaerythritol.
[0007] A need exists for a synthetic ester lubricant base stock for
aircraft turbine oils which provide for formulated oils having
viscosity and pour point characteristics capable of meeting the to
military specifications for aircraft turbine oils, while minimizing
the amount of pentanoic and hexanoic acids contained therein in
order to improve odor, thermal stability and oxidative stability. A
need also exists for the low odor and improved stability synthetic
ester lubricant base stock to be combined with a standard lubricant
additive package to provide an aircraft engine oil that meets
military specification MIL-L-23699G and AS5780, with a viscosity at
210 degree F. (99 degree C.) of at least 5.0 cSt and at -40 degree
C. of no more than 13,000 cSt, and a pour point of less than at
least -65 degree F. (-54 degree C.).
SUMMARY
[0008] According to the present disclosure, an advantageous polyol
ester lubricant base stock comprises the reaction product of: (a) a
polyol represented by the formula R(OH).sub.n wherein R is an
aliphatic or a cyclo-aliphatic hydrocarbyl group and n is at least
2, and (b) a mixture of monocarboxylic acids comprising at least
one linear acid selected from the group consisting of between C6 to
C10 acids and optionally at least one branched C6 acid, wherein the
amount of C6 to C10 acids is at least 55 wt. % and the amount of
the optional at least one branched C6 acid is 45 wt. % or less,
based upon the total amount of said mixture of monocarboxylic
acids, and wherein the mixture of monocarboxylic acids is
substantially free of C5 acid.
[0009] A further aspect of the present disclosure relates to an
advantageous aircraft turbine oil comprising from 70 to 95 wt % of
a polyol ester base stock and from 1 to 15 wt. % of a lubricant
additive package, wherein the polyol ester base stock comprises the
reaction product of: (a) a polyol represented by the formula
R(OH).sub.n wherein R is an aliphatic or a cyclo-aliphatic
hydrocarbyl group and n is at least 2, and (b) a mixture of
monocarboxylic acids comprising at least one linear acid selected
from the group consisting of between C6 to C10 acids and at least
one branched C6 acid, wherein the amount of C6 to C10 acids is at
least 55 wt. % and the amount of the at least one branched C6 acid
is 45 wt. % or less, based upon the total amount of said mixture of
monocarboxylic acids, and wherein the mixture of monocarboxylic
acids is substantially free of C5 acid.
[0010] Another aspect of the present disclosure relates to an
advantageous method of making a polyol ester lubricant base stock
comprising esterifying reaction mixture of a polyol represented by
the formula R(OH).sub.n wherein R is an aliphatic or a
cyclo-aliphatic hydrocarbyl group and n is at least 2 and an excess
mixture of monocarboxylic acids comprising at least one linear acid
selected from the group consisting of between C6 to C10 acids and
optionally at least one branched C6 acid, wherein the amount of C6
to C10 acids is at least 55 wt. % and the amount of the optional at
least one branched C6 acid is 45 wt. % or less, based upon the
total amount of said mixture of monocarboxylic acids, and wherein
the mixture of monocarboxylic acids is substantially free of C5
acid, wherein the esterification occurs with or without a sulfonic
acid, phosphorus acid, sulfonic acid, para-toluene sulfuric acid or
titanium, zirconium or tin-based catalyst, at a temperature in the
range between about 140 to 250 degree C. and a pressure in the
range between about 30 mm Hg to 760 mm Hg.
[0011] Still yet another aspect of the present disclosure relates
to an advantageous of method of reducing volatility and odor of an
aircraft turbine oil in actual used conditions comprising providing
to an aircraft turbine an aircraft turbine oil comprising from 70
to 95 wt % of a polyol ester base stock and from 1 to 15 wt. % of a
lubricant additive package, wherein the polyol ester base stock
comprises the reaction product of: (a) a polyol represented by the
formula R(OH).sub.n wherein R is an aliphatic or a cyclo-aliphatic
hydrocarbyl group and n is at least 2, and (b) a mixture of
monocarboxylic acids comprising at least one linear acid selected
from the group consisting of between C6 to C10 acids and optionally
at least one branched C6 acid, wherein the amount of C6 to C10
acids is at least 55 wt. % and the amount of the optional at least
one branched C6 acid is 45 wt. % or less, based upon the total
amount of said mixture of monocarboxylic acids, and wherein the
mixture of monocarboxylic acids is substantially free of C5 acid,
wherein the turbine oil has an evaporative weight loss at
204.degree. C. for 6.5 hours per ASTM D972 of less than 3.2 wt. %,
a TGA-simulated Noack volatility of less than 3.1 wt. % and a
GC-simulated distillation at 10% weight loss temperature of greater
than 800 deg. F., and reduced odor during use in an aircraft
turbine relative to a comparable aircraft turbine oil including a
C5 acid in the reaction mixture.
[0012] These and other features and attributes of the disclosed
polyol ester lubricant base stock for aircraft turbine oils of the
present disclosure and their advantageous applications and/or uses
and methods of making will be apparent from the detailed
description which follows, particularly when read in conjunction
with the figures appended hereto.
DETAILED DESCRIPTION
[0013] All numerical values within the detailed description and the
claims herein are modified by "about" or "approximately" the
indicated value, and take into account experimental error and
variations that would be expected by a person having ordinary skill
in the art.
[0014] Prior art jet engine polyol ester base stocks are made with
a significant amount of n- and iso-pentanoic acid (C5 acid is about
35-45 wt % of the total acids). When these prior art jet engine
polyol ester base stocks are formulated into commercial jet engine
lubricants, the C5 acids result in a very unpleasant odor, which
can be detected at even at parts per billion (ppb) levels. These C5
acids can be released in-service when the esters are hydrolyzed or
broken down by thermal or oxidative mechanisms. Hexanoic acid (C6)
can also be detected at low levels, but its odor is far less
offensive than C5 acid.
[0015] The Applicants have discovered that polyol ester base stocks
that do not include C5 acid in esterfying the polyol results in a
polyol ester base stock with surprisingly improved volatility and
odor relative to a comparable polyol ester base stock that does
include a significant amount of C5 acid. A significant amount of C5
acid means at least 5 wt. %, or at least 10 wt. %, or at least 15
wt. %, or at least 20 wt. %, or at least 25 wt. %, or at least 30
wt. %, or at least 35 wt. %, or at least 40 wt. % of the total
amount of the mixture of monocarboxylic acids.
[0016] More particularly, the present disclosure provides novel jet
engine polyol ester base stocks that provide decreased volatility
and odor relative to prior art jet engine polyol ester base stocks.
The novel neopentyl polyol esters base stocks of the instant
disclosure are made using C6-C10 carboxylic acids and are
substantially free of C5 acids. A polyol ester base stock that is
"substantially free of C5 acids" means that the base stock includes
less than 1 wt. %, or less than 0.5 wt. %, or less than 0.2 wt. %,
or less than 0.1 wt. %, or less than 500 ppm, or less than 200 ppm,
or less than 100 ppm. The Applicants have discovered jet engine
polyol ester base stock compositions that are substantially free of
C5 acids, but that still yield the balance of properties to meet
the military and civil standards for jet turbine oils.
[0017] The novel neopentyl polyol esters base stocks of the instant
disclosure when used in jet engine turbine oils provide less
odiferous breakdown products due to hydrolysis, thermal or
oxidative breakdown in aviation service. These novel neopentyl
polyol esters base stocks may also find application in other areas
where odor can be a concern, such as in compressor oils or thermal
oils.
[0018] In one form of the present disclosure, the inventive polyol
ester base stock includes the reaction product of:
(a) a polyol represented by the formula R(OH).sub.n wherein R is an
aliphatic or a cyclo-aliphatic hydrocarbyl group and n is at least
2, and (b) a mixture of monocarboxylic acids comprising at least
one linear acid selected from the group consisting of between C6 to
C10 acids and optionally at least one branched C6 acid, wherein the
amount of C6 to C10 acids is at least 55 wt. % and the amount of
the optional at least one branched C6 acid is 45 wt. % or less,
based upon the total amount of said mixture of monocarboxylic
acids, and wherein the mixture of monocarboxylic acids is
substantially free of C5 acid.
[0019] In one advantageous form, the polyol may include technical
pentaerythritol in an amount between about 50 to 100 weight %, or
between 60 to 90 weight %, or between 70 to 80 weight %, based on
the total polyol, and di-pentaerythritol in an amount between about
0 to 50 weight %, or between 10 to 40 weight %, or between 20 to 30
weight %, based on the total polyol.
[0020] The C6 to C10 linear acids may include, but are not limited
to, hexanoic acid, heptanoic acid, caprylic acid, pelargonic acid,
capric acid and combinations thereof. The C6 branched acids may
include, but are not limited to, 2-methyl pentanoic acid,
4-methylpentoic acid, and combinations thereof.
[0021] The at least one linear C6 to C10 acid may alternatively
constitute at least 60 wt. %, or at least 65 wt. %, or at least 70
wt. %, or at least 75 wt. %, or at least 80 wt. %, or at least 85
wt. %, or at least 90 wt. %, or at least 95 wt. %, or 100 wt. %,
based upon the total amount of said mixture of monocarboxylic
acids.
[0022] The at least one branched C6 acid may alternatively
constitute 40 wt. % or less, 35 wt. % or less, 30 wt. % or less, 25
wt. % or less, 20 wt. % or less, 15 wt. % or less, 10 wt. % or
less, 5 wt. % or less, or 0 wt. %, based upon the total amount of
said mixture of monocarboxylic acids. In one preferred form, the at
least one branched C6 acid constitutes 0 wt. %, based upon the
total amount of said mixture of monocarboxylic acids.
[0023] In another form, the mixture of monocarboxylic acids may
include linear C6 acid ranging from 20 to 70 wt. %, or 30 to 60 wt.
%, or 40 to 50 wt. % of the total amount of said mixture of
monocarboxylic acids.
[0024] In yet another form, the mixture of monocarboxylic acids may
include linear C7 acid ranging from 16 to 40 wt. %, or 20 to 35 wt.
%, or 25 to 30 wt. % of the total amount of said mixture of
monocarboxylic acids.
[0025] In still yet another form, the mixture of monocarboxylic
acids may include C8 to C10 acids ranging from 14 to 25 wt. %, or
16 to 23 wt. %, or 18 to 21 wt. % of the total amount of said
mixture of monocarboxylic acids.
[0026] Also provided are inventive aircraft turbine oils including
the inventive polyol ester base stocks described above. In
particular, the inventive aircraft turbine oil includes from 85 to
99 wt %, or 88 to 96 wt %, or 90 to 94 wt % of a polyol ester base
stock and from 1 to 15 wt. %, or 3 to 12 wt. %, or 4 to 10 wt. % or
5 to 8% of a lubricant additive package, wherein the polyol ester
base stock comprises the reaction product of:
a) a polyol represented by the formula R(OH).sub.n wherein R is an
aliphatic or a cyclo-aliphatic hydrocarbyl group and n is at least
2, and b) a mixture of monocarboxylic acids comprising at least one
linear acid selected from the group consisting of between C6 to C10
acids and optionally at least one branched C6 acid, wherein the
amount of C6 to C10 acids is at least 55 wt. % and the amount of
the optional at least one branched C6 acid is 45 wt. % or less,
based upon the total amount of said mixture of monocarboxylic
acids, and wherein the mixture of monocarboxylic acids is
substantially free of C5 acid.
[0027] Also provided are methods of making the inventive polyol
base stocks described above. In particular, the method of making a
polyol base stock includes: esterifying reaction mixture of a
polyol represented by the formula R(OH).sub.n wherein R is an
aliphatic or a cyclo-aliphatic hydrocarbyl group and n is at least
2 and an excess mixture of monocarboxylic acids comprising at least
one linear acid selected from the group consisting of between C6 to
C10 acids and optionally at least one branched C6 acid, wherein the
amount of C6 to C10 acids is at least 55 wt. % and the amount of
the optional at least one branched C6 acid is 45 wt. % or less,
based upon the total amount of said mixture of monocarboxylic
acids, and wherein the mixture of monocarboxylic acids is
substantially free of C5 acid, wherein the esterification occurs
with or without a sulfonic acid, phosphorus acid, sulfonic acid,
para-toluene sulfuric acid or titanium, zirconium or tin-based
catalyst, at a temperature in the range between about 140 to 250
degree C. and a pressure in the range between about 30 mm Hg to 760
mm Hg.
[0028] The method of making the polyol base stocks of the instant
disclosure may also include the step of adding an adsorbent to the
reaction mixture following esterification step. Non-limiting
exemplary adsorbents include alumina, silica gel, activated carbon,
zeolites, clay and filter aid.
[0029] The method of making the polyol base stocks of the instant
disclosure may also include the steps of adding water and base to
simultaneously neutralize the residual organic and mineral acids
and/or hydrolyze said catalyst; removing of the water used in the
hydrolysis step by heat and vacuum in a flash step; filtering of
solids from the ester mixture containing the bulk of the excess
acids used in the esterification reaction; removing excess acids by
steam stripping or any other distillation method; and removing any
residual solids from the stripped ester in a final filtration.
[0030] Also provided are methods of reducing volatility and odor of
an aircraft turbine oil that includes providing to an aircraft
turbine an aircraft turbine oil including from 70 to 95 wt % of a
polyol ester base stock and from 1 to 15 wt. % of a lubricant
additive package, wherein the polyol ester base stock comprises the
reaction product of:
a) a polyol represented by the formula R(OH).sub.n wherein R is an
aliphatic or a cyclo-aliphatic hydrocarbyl group and n is at least
2, and b) a mixture of monocarboxylic acids comprising at least one
linear acid selected from the group consisting of between C6 to C10
acids and optionally at least one branched C6 acid, wherein the
amount of C6 to C10 acids is at least 55 wt. % and the amount of
the optional at least one branched C6 acid is 45 wt. % or less,
based upon the total amount of said mixture of monocarboxylic
acids, and wherein the mixture of monocarboxylic acids is
substantially free of C5 acid.
[0031] The inventive turbine oils have an evaporative weight loss
at 204.degree. C. for 6.5 hours per ASTM D972 of less than 3.2 wt.
%, or less than 3.0 wt. %, or less than 2.8 wt. %, or less than 2.6
wt. %, or less than 2.4 wt. %, or less than 2.2 wt. %, or less than
2.0 wt. %. The inventive turbine oils also have a TGA-simulated
Noack volatility of less than 3.1 wt. %, or less than 3.0 wt. %, or
less than 2.8 wt. %, or less than 2.6 wt. %, or less than 2.4 wt.
%, or less than 2.2 wt. %, or less than 2.0 wt. %.
[0032] The inventive turbine oils have a GC-simulated distillation
at 10% weight loss temperature of greater than 800 deg. F., or
greater than 810 deg. F., or greater than 820 deg. F., or greater
than 840 deg. F., or greater than 840 deg. F. The inventive turbine
oils also have a GC-simulated distillation at 50% weight loss
temperature of greater than 880 deg. F., or greater than 890 deg.
F., or greater than 900 deg. F., or greater than 910 deg. F., or
greater than 915 deg. F. The inventive turbine oils also have a
GC-simulated distillation at 90% weight loss temperature of greater
than 1000 deg. F., or greater than 1100 deg. F., or greater than
1020 deg. F., or greater than 1030 deg. F., or greater than 1040
deg. F., or greater than 1050 deg. F., or greater than 1060 deg.
F.
[0033] The inventive turbine oils have a reduced odor during use in
an aircraft turbine relative to a comparable aircraft turbine oil
including a C5 acid in the reaction mixture. The reduction in order
is at least 10% lower, or at least 20% lower, or at least 30%
lower, or at least 40% lower, or at least 50% lower than a
comparable aircraft turbine oil including a C5 acid in the reaction
mixture.
Polyol Ester Base Stock
[0034] Turbine oils, e.g. gas turbine oils, aviation turbine oils
and jet engine turbine oils, employ synthetic esters and especially
polyol esters as base oils.
[0035] The synthetic ester which can be used as the base oil is
formed by the esterification of an aliphatic monohydric or
polyhydric alcohol with linear or branched carboxylic acids.
[0036] The synthetic esters employed as base oils for the turbine
oil have kinematic viscosities at 100.degree. C. in the range of 2
to 12 mm.sup.2/s, preferably 3 to 8 mm.sup.2/s, more preferably 4
to 6 mm.sup.2/s, and even more preferably 5 mm.sup.2/s.
[0037] Monohydric alcohols suitable for making ester base stocks
include methyl, butyl, isooctyl, didecyl and octadecyl alcohols.
"Oxo" alcohols prepared by the reaction of olefins with carbon
monoxide and hydrogen are suitable. Neo-alcohols, i.e., alcohols
having no hydrogens on the beta carbon atom, are preferred.
Examples of such alcohols are 2,2,4-trimethyl-pentanol and
2,2-dimethyl propanol.
[0038] The polyhydric alcohols which can be reacted with the linear
acid are, by way of example, polyols represented by the general
formula:
R(OH).sub.n
wherein R is any aliphatic or cyclo-aliphatic hydrocarbyl group
(preferably an alkyl) and n is at least 2. The hydrocarbyl group
may contain from about 2 to about 20 or more carbon atoms, and the
hydrocarbyl group may also contain substituents such as chlorine,
nitrogen and/or oxygen atoms. The polyhydroxyl compounds generally
may contain one or more oxyalkylene groups and, thus, the
polyhydroxyl compounds include compounds such as polyetherpolyols.
The number of carbon atoms (i.e., carbon number, wherein the term
"carbon number" as used throughout this application refers to the
total number of carbon atoms in either the acid or alcohol as the
case may be) and number of hydroxyl groups contained in the
polyhydroxyl compound used to form the carboxylic esters may vary
over a wide range.
[0039] The following alcohols are particularly useful as polyols:
2-ethyl-1,3-hexanediol, 2-propyl-3,3-heptanediol,
2-butyl-1,3-butanediol, 2,4-dimethyl-1,3-butanediol, neopentyl
glycol, 2,2-dimethylol butane, trimethylol ethane, trimethylol
propane, trimethylol butane, mono-pentaerythritol, technical grade
pentaerythritol, di-pentaerythritol, tri-pentaerythritol, ethylene
glycol, propylene glycol and polyalkylene glycols (e.g.,
polyethylene glycols, polypropylene glycols, polybutylene glycols,
etc., and blends thereof such as polymerized mixture of ethylene
glycol and propylene glycol). Mixtures of such alcohols may also be
used.
[0040] The carboxylic acid reactant used to produce the synthetic
polyol ester base oil is selected from aliphatic monocarboxylic
acids or a mixture of aliphatic monocarboxylic acids and aliphatic
dicarboxylic acids. The carboxylic acids contain from 6 to 20
carbon atoms, or 6 to 10 carbon atoms and include the straight and
branched chain aliphatic acids. The aliphatic chain may include
aryl substituents. Mixtures of acids may also be used.
[0041] The carboxylic acid used is a branched or linear C.sub.6 to
C.sub.20, or C.sub.6 to C.sub.10 carboxylic acid.
[0042] The branched acid is preferably a mono-carboxylic acid which
has a carbon number in the range between about C.sub.6 to C.sub.20,
more preferably about C.sub.6 to C.sub.10 wherein methyl or ethyl
branches are preferred. The mono-carboxylic acid is preferably at
least one acid selected from the group consisting of:
2,2-dimethylpropionic acid (neopentanoic acid), neoheptanoic acid,
neooctanoic acid, neononanoic acid, isohexanoic acid, neodecanoic
acid, 2-ethylhexanoic acid (2EH), 3,5,5-trimethylhexanoic acid
(TMH), isoheptanoic acid, isooctanoic acid, isononanoic acid and
isodecanoic acid. One especially preferred branched acid is
3,5,5-trimethylhexanoic acid. The term "neo" as used herein refers
to a trialkyl acetic acid, i.e. an acid which is triply substituted
at the alpha carbon with alkyl groups. These alkyl groups are equal
to or greater than CH.sub.3, as shown in the general structure set
forth herebelow:
##STR00001##
wherein R.sub.1, R.sub.2 and R.sub.3 are greater than or equal to
CH.sub.3 and not equal to hydrogen.
[0043] 3,5,5-trimethylhexanoic acid has the structure set forth
herebelow:
##STR00002##
[0044] The mono-carboxylic linear acids are any linear saturated
alkyl carboxylic acid having a carbon number in the range between
about C.sub.6 to C.sub.20, preferably C.sub.6 to C.sub.10.
[0045] Some examples of linear acids include sebacic, azelaic,
suberic, succinic, adipic, oxalic, malonic, glutaric,
pentadecanedicarboxylic, diglycolic, thiodiglycolic, acetic,
propionic, lauric, palmitic, pimelic, n-hexanoic, n-heptanoic,
n-octanoic, n-nonanoic, and n-decanoic acids and mixtures
thereof.
[0046] Examples of suitable ester base oils are ethyl palmitate,
ethyl laurate, butyl stearate, di-(2-ethylhexyl) sebacate,
di(2-ethylhexyl) azealate, ethyl glycol dilaurate,
di-(2-ethylhexyl) phthalate, di-(1,3-methylbutyl) adipate,
di-(1-ethylpropyl) azelate, diisopropyloxylate, dicyclohexyl
sebacate, glycerol tri-n-heptoate, di(undecyl) azelate, and
tetraethylene glycol di-(2-ethyl caproate), and mixtures
thereof.
[0047] If it is desired to form a complex alcohol ester or complex
acid ester, then the synthetic ester can also include a polybasic
acid selected from the group consisting of: any C.sub.2 to C.sub.12
polybasic acids, e.g. adipic, azelaic, sebacic and dodecanedioic
acids.
[0048] Other preferred polyol ester base oils are those ones
prepared from technical pentaerythritol and a mixture of linear and
branched C.sub.6 to C.sub.20 carboxylic acids, or C.sub.6 to
C.sub.12 carboxylic acids. Technical pentaerythritol is a mixture
which includes about 85 to 92% monopentaerythritol and 8 to 15%
dipentaerythritol. A typical commercial technical pentaerythritol
contains about 88% monopentaerythritol having the formula:
##STR00003##
and about 12% of dipentaerythritol having the formula:
##STR00004##
The technical pentaerythritol may also contain some tri- and
tetrapentaerythritol that is normally formed as by-products during
the manufacture of technical pentaerythritol.
[0049] The preparation of esters from alcohols and carboxylic acids
can be accomplished using conventional methods and techniques known
and familiar to those skilled in the art. In general, the
monohydric alcohol or polyhydric alcohol, e.g. technical
pentaerythritol, is heated with the desired carboxylic acid or
mixture of acids either neat or in the presence of a solvent such
as an aromatic hydrocarbon and optionally in the presence of
catalyst such as, e.g. titanium, zirconium and tin catalysts such
as titanium, zirconium or tin alcoholates, carboxylates and
chelates, HCl, HF, HBr, H.sub.2SO.sub.4, BF.sub.3, etc., see for
example U.S. Pat. No. 3,038,859 and U.S. Pat. No. 3,121,109, herein
incorporated by reference in their entirety.
[0050] Generally, a slight excess of acid is employed to force the
reaction to completion to produce a fully esterified product. Water
is removed during the reaction and any excess acid is then stripped
from the reaction mixture. The esters of technical pentaerythritol
may be used without further purification or may be further purified
using conventional techniques such as distillation or other methods
known to those of skill in the art.
[0051] Other polyol esters useful as turbine oil base oils are
those made by synthesizing the polyol esters from a polyol and a
branched or linear carboxylic acid in such a way that it has a
substantial amount of unreacted hydroxyl groups; that is, the
product is not fully esterified. The presence of the unreacted
hydroxyl group in the ester is believed to allow this "high"
hydroxyl ester to exhibit increased thermal/oxidation stability, as
measured by high pressure differential scanning calorimetry
(HPDSC). It is believed the presence of the unreacted hydroxyl
group provides a pathway capable of scavenging alkoxide and alkyl
peroxide radicals formed in the turbine oil during use, such
scavenging thereby reducing the rate at which oxidation degradation
can occur.
[0052] The high hydroxyl polyester is the reaction product of a
linear or branched alcohol and at least one branched and/or linear
carboxylic acid, the resulting synthetic ester having a hydroxyl
number between 5 to 180 depending on the acid and polyol used (e.g.
1 to 25% unconverted hydroxyl groups, based on the total amount of
hydroxyl groups in the branched or linear alcohol), preferably
between about 5 to 100 (e.g. 1 to 15% unconverted hydroxyl groups),
more preferably between 10 to 80 (e.g. 2 to 10% unconverted
hydroxyl groups).
[0053] Hydroxyl number measures the free hydroxyl groups by
determining the amount of acetic anhydride that the sample will
react with under certain conditions. Anhydride is introduced in
excess with the sample. Once the reaction is complete, the
remaining anhydride is determined by titration with a base
solution. The hydroxyl number is reported as milligrams of KOH/gram
of sample. A standard method for measuring hydroxyl number is
detailed by the American Oil Chemist's Society as A.O.C.S. Cd.
13-60. For highly converted esters, e.g. 99% or more conversion to
ester (almost no unreacted hydroxyl groups), the hydroxyl number is
generally less than or equal to 5.
[0054] In the case of both the fully esterified ester and the ester
containing free hydroxyl groups, the alcohols and acids employed
can be the same, the only difference in the products being, as
previously indicated, that in one instance the product is fully
esterified and in the other the product has free hydroxyl
groups.
[0055] Mixtures of fully esterified synthetic esters and of
synthetic esters containing free hydroxyl groups can also be
used.
[0056] Esters suitable for use as base stocks for turbine oils are
esters of monocarboxylic acids having six to twelve carbons and
polyalcohols such as pentaerythritol, dipentaerythritol and
trimethylolpropane. Examples of these esters are pentaerythrityl
tetrabutyrate, pentaerythrityl tetravalerate, pentaerythrityl
tetracaproate, pentaerythrityl dibutyratedicaproate,
pentaerythrityl butyratecaproate divalerate, pentaerythrityl
butyrate trivalerate, pentaerythrityl butyrate tricaproate,
pentaerythrityl tributyratecaproate, mixed C.sub.6- to
C.sub.10-saturated fatty acid esters of pentaerythritol,
dipentaerythrityl hexavalerate, dipentaerythrityl hexacaproate,
dipentaerythrityl hexaheptoate, dipentaerythrityl hexacaprylate,
dipentaerythrityl tributyrate tricaproate, dipentaerythrityl
trivalerate trinonylate, dipentaerythrityl mixed hexaesters of
C.sub.6 to C.sub.10 fatty acids and trimethylolpropane heptylate.
Pentaerythrityl esters of mixtures of C.sub.6 to C.sub.12 acids are
excellent base oils.
[0057] If desired the synthetic esters, e.g. fully esterified
and/or esters containing free hydroxyl groups, can be further used
with other base stocks such as mineral oil, highly refined mineral
oil, polyalpha olefins, polyalkylene glycols, phosphate esters,
silicone oils, other polyol esters, as well as hydrocarbon oils
made by hydrodewaxing/hydroisomerizing waxy feeds such as
hydrodewaxed/hydroisomerized slack wax or Fischer-Tropsch synthesis
waxes.
[0058] It is preferred, however, that the synthetic ester be it a
fully esterified material or an ester containing free hydroxyl
groups either be used individually or only in the mixture of two or
more esters.
Lubricant Additives
[0059] The lubricant compositions of the present invention may also
comprise other conventional lubricant additives. Thus, a fully
formulated turbine oil may contain one or more of the following
classes of additives: antioxidants, antiwear agents, extreme
pressure additives, antifoamants, detergents, hydrolytic
stabilizers, metal deactivators, other rust inhibitors, etc. Total
amounts of such other additives can be in the range 1 to 15 wt %,
or 3 to 12 wt. %, or 4 to 10 wt. %, or 5 to 8 wt. %.
[0060] Lubricating oil additives are described generally in
"Lubricants and Related Products" by Dieter Klamann, Verlag Chemie,
Deerfield, Fla., 1984, and also in "Lubricant Additives" by C. V.
Smalheer and R. Kennedy Smith, 1967, pp. 1-11, the contents of
which are incorporated herein by reference. Lubricating oil
additives are also described in U.S. Pat. Nos. 6,043,199,
5,856,280, and 5,698,502, the contents of which are incorporated
herein by reference.
[0061] The synthetic polyol ester base stock disclosed herein may
also contain one or more of the following classes of additives:
antioxidants, antiwear agents, extreme pressure additives,
antifoamants, detergents, hydrolytic stabilizers and metal
deactivators.
[0062] Antioxidants, which can be used, include aryl amines, e.g.
phenylnaphthylamines and dialkyl diphenylamines, mixtures thereof
and reaction products thereof which are described in U.S. Pat. No.
6,426,324 the contents of which are incorporated herein by
reference; hindered phenols, phenothiazines, and their derivatives.
The antioxidants are typically used in an amount in the range 1 to
5 wt % of the lubricant composition.
[0063] Antiwear/extreme pressure additives include hydrocarbyl
phosphate esters, particularly trihydrocarbyl phosphate esters in
which the hydrocarbyl radical is an aryl or alkaryl radical or
mixture thereof. Particular antiwear/extreme pressure additives
include tricresyl phosphate, triaryl phosphate and mixtures
thereof. Other or additional antiwear/extreme pressure additives
may also be used. The antiwear/extreme pressure additives are
typically used in an amount in the range 0 to 4 wt. %, preferably 1
to 3 wt % of the lubricant composition.
[0064] Corrosion inhibitors may also be included into the turbine
oil. Exemplary corrosion inhibitors include the various triazoles.
For example, tolyltriazol, 1,2,4 benzene triazole, 1,2,3 benzene
triazole, carboxy benzotriazole, alkylated benzotriazole. The
corrosion inhibitor additive can be used in an amount in the range
0.02 to 0.5 wt %, preferably 0.05 to 0.25 wt % of the lubricant
composition. Other rust inhibitors common to the industry include
the various hydrocarbyl amine phosphates and/or amine
phosphates.
[0065] Other additives can also be employed including hydrolytic
stabilizers pour point depressants, anti foaming agents, viscosity
and viscosity index improver, etc.
[0066] Foam control can be provided by many compounds including an
antifoamant of the polysiloxane type, e.g., silicone oil or
polydimethyl siloxane.
[0067] Another additive that can be used is an anti-deposition and
oxidative additive. A typical anti-deposition and oxidation
additive is a sulfur containing carboxylic acid (SCCA) as described
in U.S. Pat. No. 5,856,280, herein incorporated by reference in its
entirety. The SCCA derivative is used in an amount in the range 100
to 2000 ppm, preferably 200 to 1000 ppm, most preferably 300 to 600
ppm.
[0068] The lubricant composition according to the present
disclosure preferably comprises about 85, 86, 87, 88, 89, 90, 91,
92, 93, 94, 95, 96, 97, 98, 99.9 wt % by weight of the mixed polyol
ester composition of the present invention and about 0.1, 0.5, 1.0,
1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5,
8.0, 8.5, 9.0, 9.5, 10.0, 10.5, 11.0, 11.5, 12.0, 12.5, 13.0, 13.5,
14.0, 14.5 to 15 wt %, preferably 2 to 10 wt %, most preferably 3
to 8 wt % by weight of a lubricant additive package.
[0069] The individual additives may be incorporated into the
present lubricant composition in any convenient way. Thus, each of
the components can be added directly to the base stock by
dispersing or dissolving it in the base stock at the desired level
of concentration. Such blending may occur at ambient temperature or
at an elevated temperature. Preferably, all the additives are
blended into a concentrate or additive package, which is
subsequently blended into base stock to make finished lubricant.
Use of such concentrates in this manner is conventional. The
concentrate will typically be formulated to contain the additive(s)
in proper amounts to provide the desired concentration in the final
formulation when the concentrate is combined with a predetermined
amount of base lubricant. The pre-mix is cooled to at least 85
degree C. and the additional components are added.
[0070] To a partially formulated polyol ester base stock of the
present disclosure, with additives that include antioxidants,
corrosion inhibitors and hydrolytic stabilizers, may be optionally
added a minor portion of
3-(di-isobutoxy-thiophosphonylsulfanyl)-2-methyl-propionic acid
(DITMPA), TCP and yellow metal passivator such that the DITMPA
generally comprises from about 0.01 to about 0.40 weight percent,
and the yellow metal passivator comprises from about 0.01 to about
0.40 weight percent, of the fully formulated lubricating oil
composition.
[0071] The structure of the DITMPA additive is as shown below.
[0072] 3-(di-isobutoxy-thiophosphonylsulfanyl)-2-methyl-propionic
acid (DITMPA).
##STR00005##
[0073] More particularly, the DITMPA may include from about 0.02 to
about 0.20 weight percent of the fully formulated lubricating oil
composition, for example from about 0.03 to about 0.10 weight
percent of the fully formulated lubricating oil composition. The
DITMPA may be mixed or blended with the polyol ester base stock by
any convenient and known means. If desirable, concentrates may be
prepared for subsequent dilution with additional polyol ester base
prior to deployment.
[0074] The yellow metal passivator can be selected from the general
class of such additives which includes, but is not limited to,
benzotriazole, quinizarin and tolutriazole also known as methyl
benzotriazole. For example, the yellow metal passivator can be
tolutriazole and comprises from about 0.05 to about 0.1 weight
percent of the fully formulated lubricating oil composition. With
the addition of DITMPA, the weight percent of other load carrying
additives such as TCP can be reduced while still retaining enhanced
load-carrying capacity and enhanced copper passivation.
[0075] The aircraft engine oils of the present disclosure meet or
exceed the requirements set out by the United States Navy in
MIL-L-23699G and AS5780 for standard performance category or high
performance category 5 cSt turbo oils.
Test Methods
[0076] Evaporative weight loss at 204.degree. C. for 6.5 hours was
measured per ASTM D972.
[0077] TGA-simulated Noack volatility was measured according to
modified ASTM D6375.
[0078] GC-simulated distillation was measured according to ASTM
D7169.
[0079] The Oxidation & Corrosion Test was measured according to
FTM5308, as per specifications MIL-PRF-23699G and AS5780.
[0080] The following are examples of the present disclosure and are
not to be construed as limiting.
EXAMPLES
[0081] Polyol ester base stocks for jet engine oils were formulated
with C6-C10 carboxylic acids (see Table 1 below). The C5 acid for
the inventive base stocks was replaced with n-hexanoic acid (n-C6)
or 2-methylpentanoic acid (i-C6). The ratios of the remaining acids
were adjusted so that the total carbon number was similar to the
carbon number in the comparative examples. The comparative and
inventive oils tested were as follows:
1. Comparative Example 1: Mixed ester, including n-C5 and iso-C5
acids. 2. Comparative Example 2: Mixed ester, including n-C5 and
iso-C5 acids. 3. Comparative Example 3: Mixed ester, including n-C5
and iso-C5 acids. 4. Inventive Example 1: Mixed ester produced
using iso-C6 acid, lower C8/C10 acid level than Comparative Example
1. 5. Inventive Example 2: Mixed ester produced using n-C6 acid,
otherwise has similar composition as Comparative Example 1. 6.
Inventive Example 3: Mixed ester produced using n-C6 acids, higher
level of C8/C10 acid than Comparative Example 1. Inventive Examples
1, 2 and 3 had monopentaerythritol, dipentaerythritol, and
tripentaerythritol (monoPE, diPE, triPE) at the same ratio as
Comparative Example 1. 7. Inventive Example 4: Mixed ester produced
using n-C6 acids, less dipentaerythritol than the comparative
examples. 8. Inventive Example 5--Mixed ester produced using high
amounts of C6 acid; same monopentaerythritol, dipentaerythritol,
and tripentaerythritol at the same ratio as Comparative Example 1.
9. Inventive Example 6--Mixed ester produced using low amount of C6
acid; same monopentaerythritol, dipentaerythritol, and
tripentaerythritol at the same ratio as Comparative Example 1. 10.
Inventive Example 7--Mixed ester produced using a relatively higher
amount of iso-C6 acid and relatively lower amount of n-C6 acid. 11.
Inventive Example 8--Mixed ester produced using a similar amounts
of iso-C6 acid and n-C6 acid.
[0082] The acid content and properties of each of the above
designated comparative examples and inventive examples are shown in
Tables 1 and 2 below.
TABLE-US-00001 TABLE 1 Ester Composition and Base Stock Properties
Wt % of total acids* Comparative Comparative Comparative Exam-
Exam- Exam- Exam- Exam- Exam- Exam- Exam- Example 1 Example 2
Example 3 ple 1 ple 2 ple 3 ple 4 ple 5 ple 6 ple 7 ple 8 C5/iC5 38
46 42 0 0 0 0 0 0 0 0 iC6 0 0 0 45.1 0 0 0 0 0 35.0 24.5 nC6 0 0 0
0 45.1 52.8 46.9 70.0 20.0 14.0 24.5 C7-C10 62 54 58 54.9 54.9 47.2
53.1 30.0 80.0 51.0 51.0 techPE/diPE ratio 12 All techPE 1.9
tech/mono 12 12 12 all techPE 12 12 13 13 100.degree. C. KV 5.02
4.76 4.63 5.06 4.99 5.06 4.97 4.83 5.26 5.07 4.97 40.degree. C. KV
24.6 23.5 22.8 25.4 23.9 24.2 23.7 22.8 25.5 25.0 24.1 VI 135 124
120 130 140 141 140 137 143 134 135 Pour Pt. -66 -- -- -63 -66 -57
-54 -69 -54 -63 -66 -40.degree. C. 8432 6011 5563 10198 8739 6867
6601 5334 7236 -- -- Visc. .degree. C. RPVOT, min 122 -- -- 98 112
102 102 -- 102 -- -- *Intentionally added. Small amounts may come
in with other raw materials.
[0083] It was surprising and unexpected that the viscosities (-40,
40, and 100 C) and pour points of each inventive example was very
similar to the comparative examples even though C5 acid was
excluded from the inventive examples. Some of the inventive
examples had improved low temperature kV (-40.degree. C.)
viscosities (Examples 2, 3, 4, 5, 6) relative to the comparative
examples. The Viscosity Indices, the pour points, and the measured
RPVOT values for the comparative and inventive examples were all
typical.
[0084] Replacing the C6 acid with C5 acid showed no harm in jet oil
formulation testing. Each ester was formulated using a standard oil
antioxidant/antiwear/metal passsivator system. For the formulated
oils using the comparative and inventive base stocks shown in Table
1, typical standard jet oil lubricant additives were used. This
includes monomeric amine antioxidants, antiwear additives, metal
passivators, and defoamants in a total combined level of 4-6 weight
percent.
[0085] The fully formulated oils had similar viscometric
properties, at 40.degree. C. and 100.degree. C. and also at lower
temperatures. Each oil was also tested in the Oxidation &
Corrosion Test at 204.degree. C. for 72 hours. The metal corrosion
was low in all cases, and the changes in viscosity and acid number
were similar to those for the comparative examples.
TABLE-US-00002 TABLE 2 Formulated Properties aad Test Results
Comparative Comparative Comparative Exam- Exam- Exam- Exam- Exam-
Exam- Exam- Exam- Example 1 Example 2 Example 3 ple 1 ple 2 ple 3
ple 4 ple 5 ple 6 ple 7 ple 8 40.degree. C. kV 25.4 23.5 22.9 26.0
25.0 26.2 24.8 24.0 26.7 26.3 25.5 (cSt) 100.degree. kV 4.97 4.76
4.63 4.95 4.99 5.17 4.98 4.84 5.25 5.08 5.00 (cSt) 0.degree. C. kV
178 157 152 192 170 181 169 161 185 -- -- (cSt) -20.degree. C. kV
980 819 801 1136 909 974 892 855 1000 -- -- (cSt) -40.degree. C. kV
9669 7617 7375 12660 8506 9298 8175 8121 9248 -- -- (cSt) TAN (mg
0.07 0.05 0.13 0.09 0.10 0.11 0.09 0.12 0.07 0.07 0.10 KOH/g)
204.degree. C. O&C Test, 72 hrs 40.degree. C. 22.0% 17.9% 19.0%
22.9% 19.3% 18.6% 17.4% 19.9% 19.9% 23.7% 23.5% Viscosity Increase
(%) TAN increase 2.32 1.67 1.87 3.28 1.52 1.50 1.79 1.68 1.59 2.08
2.16 (mg KOH/g) .DELTA.Aluminum -0.01 -0.02 0.00 -0.01 0.00 0.01
-0.01 0.01 0.01 0.02 0.02 (mg/cm.sup.2) .DELTA.Silver -0.02 -0.02
-0.01 -0.02 -0.01 0.00 -0.02 0.00 0.00 0.01 0.01 (mg/cm.sup.2)
.DELTA.Copper -0.08 -0.05 -0.01 -0.09 -0.07 -0.05 -0.07 -0.12 -0.05
-0.08 -0.17 (mg/cm.sup.2) .DELTA.Steel 0.00 0.00 0.01 0.00 0.01
0.01 0.01 0.01 0.02 0.02 0.03 (mg/cm.sup.2) .DELTA.Magnesium 0.00
-0.01 0.00 -0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.03 (mg/cm.sup.2)
Sludge (mg/ 1.6 6.2 2.9 3.9 6.7 14.2 4.7 5.8 5.9 5.9 6.2 100
mL)
[0086] Volatility-related properties of the fully formulated oils
are shown in Table 3. It was also surprising and unexpected that
the inventive examples exhibited lower volatility than the
comparative examples using the Evaporation Loss (D972) test, the
TGA-simulated Noack test, and the GC method for a Simulated
Distillation. In all three tests, for the fully formulated fresh
oils, Inventive Example 1 was similar in performance to the
comparative examples, showing that an ester with no C5 acid is not
necessarily less volatile than an ester including C5 acid.
[0087] For Inventive Examples 2-8 evaporation loss was lower,
showing reduced volatility. TGA-simulated Noack was also lower,
showing reduced volatility. The simulated distillation 10% to loss,
50% loss, and 90% loss points were higher for the inventive
examples versus the comparative examples, again showing reduced
volatility. Comparative Examples 1 and 2 and Inventive Example 1,
7, and 8 were produced with some branched acid, and show that
Inventive Example 1, 7 and 8 have similar to significantly lower
evaporative weight loss than Comparative Examples 1 and 2.
Comparative Example 3 and Inventive Examples 2-6 were produced with
all linear acids, and show that Inventive Examples 2-6 have
significantly lower evaporative weight loss than Comparative
Example 3.
TABLE-US-00003 TABLE 3 Formulated Oil Properties and Reduced
Volatility Comparative Comparative Comparative Exam- Exam- Exam-
Exam- Exam- Exam- Exam- Exam- Example 1 Example 2 Example 3 ple 1
ple 2 ple 3 ple 4 ple 5 ple 6 ple 7 ple 8 Evaporation Loss, D972
3.59 2.81 3.63 3.07 2.28 2.17 1.69 2.25 1.83 2.44 1.94 Simulated
Noack, % 3.66 3.16 3.93 3.03 2.26 2.14 2.55 2.54 1.83 2.88 2.78
SimDis, 10% off, .degree. F. 805 810 806 804 845 840 810 821 849
896 894 SimDis, 50% off, .degree. F. 877 885 876 886 895 906 903
883 918 1052 1051 SimDis, 90% off, .degree. F. 1007 994 947 1005
1034 1052 1040 1024 1062 896 894
[0088] In addition, the volatility of the inventive compositions
was tested on the oils after the 72 hour Oxidation & Corrosion
Test at 204.degree. C., see Table 4. The evaporation rates for the
comparative example after oxidation are around 3 minutes. The
inventive examples are similar or lower than 3 minutes in all
cases, showing that the inventive jet oils maintain a lower
volatility versus the comparative examples, even after being
oxidized. Similarly, the simulated Noack is over 4 minutes for the
comparative examples, whereas for the 8 inventive examples, the
simulated Noack is about 4 minutes, or less than 4 minutes, or even
less than 3 minutes. This also indicates that the inventive jet
oils maintain a lower volatility versus the comparative examples,
even after being oxidized. The same trend is seen in the Simulated
Distillation, where for the inventive examples, the 10%, 50%, and
90% off loss points are similar to or higher than than the same
points in the comparative examples.
TABLE-US-00004 TABLE 4 Post-Oxidation & Corrosion Test, Oil
Properties and Reduced Volatility Comparative Comparative
Comparative Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Example
1 Example 2 Example 3 ple 1 ple 2 ple 3 ple 4 ple 5 ple 6 ple 7 ple
8 Evaporation Loss, D972 3.18 2.54 3.01 2.59 1.77 1.71 1.6 2.07
1.65 1.97 2.12 Simulated Noack, % 4.12 4.05 4.41 3.92 3.08 2.54
2.55 3.31 2.18 3.47 3.59 SimDis, 10% off, .degree. F. 788 795 809
806 852 855 850 849 866 838 827 SimDis, 50% off, .degree. F. 882
892 881 888 901 908 909 889 923 896 894 SimDis, 90% off, .degree.
F. 1027 1032 1006 1026 1053 1063 1054 1044 1072 1052 1051
PCT/EP Clauses:
[0089] 1. A polyol ester base stock comprising the reaction product
of:
[0090] (a) a polyol represented by the formula R(OH).sub.n wherein
R is an aliphatic or a cyclo-aliphatic hydrocarbyl group and n is
at least 2, and
[0091] (b) a mixture of monocarboxylic acids comprising at least
one linear acid selected from the group consisting of between C6 to
C10 acids and optionally at least one branched C6 acid, wherein the
amount of C6 to C10 acids is at least 55 wt. % and the amount of
the optional at least one branched C6 acid is 45 wt. % or less,
based upon the total amount of said mixture of monocarboxylic
acids, and wherein the mixture of monocarboxylic acids is
substantially free of C5 acid.
[0092] 2. The base stock of clause 1, wherein the hydrocarbyl group
of the polyol includes from 2 to 20 carbon atoms.
[0093] 3. The base stock of clause 2, wherein the hydrocarbyl group
includes a substituent selected from the group consisting of
chlorine, nitrogen, oxygen and combinations thereof.
[0094] 4. The base stock of clauses 1-3, wherein the polyol is
selected from the group consisting of 2-ethyl-1,3-hexanediol,
2-propyl-3,3-heptanediol, 2-butyl-1,3-butanediol,
2,4-dimethyl-1,3-butanediol, neopentyl glycol, 2,2-dimethylol
butane, trimethylol ethane, trimethylol propane, trimethylol
butane, mono-pentaerythritol, technical grade pentaerythritol,
di-pentaerythritol, tri-pentaerythritol, ethylene glycol, propylene
glycol, polyalkylene glycols and combinations thereof.
[0095] 5. The base stock of clause 4, wherein the polyalkylene
glycol is selected from the group consisting of polyethylene
glycols, polypropylene glycols, polybutylene glycols and
combinations thereof.
[0096] 6. The base stock of clauses 1-5, wherein said at least one
C6 to C10 linear acid is selected from the group consisting of
hexanoic acid, heptanoic acid, caprylic acid, pelargonic acid and
capric acid.
[0097] 7. The base stock of clauses 1-6, wherein said at least one
C6 branched acid is selected from the group consisting of:
2-methylpentanoic, 4-methylpentoic acid, and combinations
thereof.
[0098] 8. The base stock of clauses 1-7, wherein said polyol
comprises technical pentaerythritol in an amount between about 50
to 100 weight %, based on the total polyol, and di-pentaerythritol
in an amount between about 0 to 50 weight %, based on the total
polyol.
[0099] 9. The base stock of clauses 1-8 including a linear C6 acid
ranging from 20 to 70 wt. % of the total amount of said mixture of
monocarboxylic acids.
[0100] 10. The base stock of clauses 1-9 including a linear C7 acid
ranging from 16 to 40 wt. % of the total amount of said mixture of
monocarboxylic acids.
[0101] 11. The base stock of clauses 1-10 including a linear C8-C10
acid ranging from 14 to 25 wt. % of the total amount of said
mixture of monocarboxylic acids.
[0102] 12. The base stock of clauses 1-11, wherein the base stock
has a viscosity of at least 4 cSt at 100 degree C., a viscosity of
less than 11,000 cSt at -40 degree C., a viscosity index of at
least 120, and a pour point of at least as low as -54 degree C.
[0103] 13. An aircraft turbine oil including the polyol ester base
stock of clause 1, wherein the oil comprises from 70 to 95 wt % of
a polyol ester base stock and from 1 to 15 wt. % of a lubricant
additive package.
[0104] 14. The turbine oil of clause 13, wherein the lubricant
additive package comprises at least one additive selected from the
group consisting of viscosity index improvers, corrosion
inhibitors, antioxidants, dispersants, anti-emulsifying agents,
color stabilizers, detergents and rust inhibitors, and pour point
depressants.
[0105] 15. The turbine oil of clauses 13-14, wherein turbine oil
comprises a blend of the polyol ester base stock and at least one
additional base stock selected from the group consisting of:
mineral oils, highly refined mineral oils, poly alpha olefins,
polyalkylene glycols, phosphate ester, silicone oils, diesters and
polyol ester.
[0106] 16. The turbine oil of clauses 13-15, wherein the turbine
oil has an evaporative weight loss at 204.degree. C. for 6.5 hours
per ASTM D972 of less than 3.2 wt. %.
[0107] 17. The turbine oil of clauses 13-16, wherein the turbine
oil has a TGA-simulated Noack volatility of less than 3.1 wt.
%.
[0108] 18. The turbine oil of clauses 13-17, wherein the turbine
oil has a GC-simulated distillation at 10% weight loss temperature
of greater than 800 deg. F.
[0109] 19. The turbine oil of clauses 13-18, wherein the turbine
oil has a reduced odor during use in an aircraft turbine relative
to a comparable aircraft turbine oil including a C5 acid in the
mixture of monocarboxylic acids.
[0110] 20. The turbine oil of clauses 13-19, wherein the turbine
oil meets military specification MIL-L-23699G with a viscosity at
210 degree F. (99 degree C.) of at least 5.0 cSt and at -40 degree
C. of no more than 13,000 cSt, and a pour point of less than at
least -65 degree F. (-54 degree C.).
[0111] 21. A method of making a polyol base stock comprising:
esterifying reaction mixture of a polyol represented by the formula
R(OH).sub.n wherein R is an aliphatic or a cyclo-aliphatic
hydrocarbyl group and n is at least 2 and an excess mixture of
monocarboxylic acids comprising at least one linear acid selected
from the group consisting of between C6 to C10 acids and optionally
at least one branched C6 acid, wherein the amount of C6 to C10
acids is at least 55 wt. % and the amount of the optional at least
one branched C6 acid is 45 wt. % or less, based upon the total
amount of said mixture of monocarboxylic acids, and wherein the
mixture of monocarboxylic acids is substantially free of C5 acid,
wherein the esterification occurs with or without a sulfonic acid,
phosphorus acid, sulfonic acid, para-toluene sulfuric acid or
titanium, zirconium or tin-based catalyst, at a temperature in the
range between about 140 to 250 degree C. and a pressure in the
range between about 30 mm Hg to 760 mm Hg.
[0112] Applicants have attempted to disclose all embodiments and
applications of the disclosed subject matter that could be
reasonably foreseen. However, there may be unforeseeable,
insubstantial modifications that remain as equivalents. While the
present invention has been described in conjunction with specific,
exemplary embodiments thereof, it is evident that many alterations,
modifications, and variations will be apparent to those skilled in
the art in light of the foregoing description without departing
from the spirit or scope of the present disclosure. Accordingly,
the present disclosure is intended to embrace all such alterations,
modifications, and variations of the above detailed
description.
[0113] All patents, test procedures, and other documents cited
herein, including priority documents, are fully incorporated by
reference to the extent such disclosure is not inconsistent with
this invention and for all jurisdictions in which such
incorporation is permitted.
[0114] When numerical lower limits and numerical upper limits are
listed herein, ranges from any lower limit to any upper limit are
contemplated.
* * * * *