U.S. patent application number 14/172022 was filed with the patent office on 2014-08-14 for polyol ester based drive-train fluid for high stress automatic transmissions.
This patent application is currently assigned to Chemtura Corporation. The applicant listed for this patent is Chemtura Corporation. Invention is credited to David Cooper, Salvatore Rea, Robert Vinson.
Application Number | 20140228267 14/172022 |
Document ID | / |
Family ID | 51297847 |
Filed Date | 2014-08-14 |
United States Patent
Application |
20140228267 |
Kind Code |
A1 |
Rea; Salvatore ; et
al. |
August 14, 2014 |
Polyol Ester Based Drive-Train Fluid for High Stress Automatic
Transmissions
Abstract
The use of certain polyol ester (POE) based fluids has been
found to be surprisingly effective in, e.g., automotive automatic
transmissions, such as, for example, racing automotive automatic
transmissions. The use of select POE based fluids has been found to
lower operating temperatures, improve torque convertor engagement
and torque convertor lock-up due to improved efficiency,
performance and friction properties, allowing improved efficiency
in high stress applications.
Inventors: |
Rea; Salvatore; (Doylestown,
PA) ; Cooper; David; (Stockton, NJ) ; Vinson;
Robert; (Childsburg, AL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Chemtura Corporation |
Middlebury |
CT |
US |
|
|
Assignee: |
Chemtura Corporation
Middlebury
CT
|
Family ID: |
51297847 |
Appl. No.: |
14/172022 |
Filed: |
February 4, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61764748 |
Feb 14, 2013 |
|
|
|
Current U.S.
Class: |
508/485 |
Current CPC
Class: |
C10M 2215/223 20130101;
C10M 2223/063 20130101; C10M 2207/123 20130101; C10N 2030/06
20130101; C10N 2020/02 20130101; C10N 2030/02 20130101; C10M
2207/2835 20130101; C10M 2217/028 20130101; C10M 2215/064 20130101;
C10N 2040/042 20200501; C10N 2040/08 20130101; C10M 2209/084
20130101; C10M 105/38 20130101 |
Class at
Publication: |
508/485 |
International
Class: |
C10M 105/38 20060101
C10M105/38 |
Claims
1. A mechanical device comprising a fluid coupling and a hydraulic
transfer fluid, said hydraulic transfer fluid being a working fluid
comprising: i) from 80 to 99% by weight of a polyol ester
composition comprising C.sub.5-10 alkylcarboxlate esters of
pentaerythritol, di-pentaerythritol, tri-pentaerythritol and/or
higher pentaerythritol oligomers; and ii) from 1 to 20% by weight
of additives selected from dispersants; anti-wear agents;
anti-oxidants; corrosion inhibitors; friction modifiers; seal swell
agents; anti-foamants viscosity modifiers, detergents, pour point
depressants; wherein the working fluid has a kinematic viscosity at
40.degree. C. of from 4 to 64 cSt, a kinematic viscosity at
100.degree. C. of from 2 to 28 cSt, and a viscosity index of
greater than greater than 100.
2. The mechanical device according to claim 1 wherein 70 to 100% by
weight of the esters of the polyol ester composition (i) are
compounds of formula Ia and IIa ##STR00004## wherein each R is
independently selected from the group consisting of pentanoyl,
hexanoyl, heptanoly, octanoyl, nonanoyl, decanoyl and branched
isomers thereof.
3. The mechanical device according to claim 2 wherein 80 to 100 mol
% of the R groups in formula (Ia) and (IIa) are linear
alkanoyl.
4. The mechanical device according to claim 1 wherein the working
fluid has a kinematic viscosity at 40 .degree. C. of from 10 to 40
cSt, a kinematic viscosity at 100 .degree. C. of from 2 to 10 cSt
and a pour point of -25.degree. C. or lower
5. The mechanical device according to claim 3 wherein 90 to 100% of
the esters of the polyol ester composition (i) are compounds of
formula Ia and IIa in a weight ratio of compounds of formula Ia to
IIa of from 2:1 to 15:1.
6. The mechanical device according to claim 5 wherein the weight
ratio of compounds of formula Ia to IIa in the polyol ester
composition (i) is from 6:1 to 15:1.
7. The mechanical device according to claim 6 wherein the polyol
ester composition (i) of the working fluid comprises compounds of
formula Ia and IIa wherein: a) from 5 to 45 mol % of all R groups
are C.sub.5 alkanoyl; b) from 5 to 45 mol %, of all R groups are
C.sub.8 alkanoyl; c) from 5 to 45 mol %, of all R groups are
C.sub.7 alkanoyl; d) from 5 to 45 mol %, of all R groups are
C.sub.8 alkanoyl; e) from 5 to 45 mol %, of all R groups are
C.sub.9 alkanoyl; and/or f) from 5 to 45 mol %, of all R groups are
C.sub.10 alkanoyl; provided that at least 3 of a), b), c), d), e)
and f) are present in at least 5 mol %.
8. The mechanical device according to claim 7 wherein the polyol
ester composition (i) of the working fluid comprises compounds of
formula Ia and IIa wherein: from 25 to 40 mol % of all R groups are
C.sub.5 alkanoyl; from 15 to 30 mol %, of all R groups are C.sub.7
alkanoyl; from 15 to 30 mol %, of all R groups are C.sub.9
alkanoyl; and from 0 to 30 mol % of all R groups are selected from
C.sub.8, C.sub.8 and C.sub.10 alkanoyl
9. The mechanical device according to claim 8 wherein the polyol
ester composition (i) of the working fluid comprises compounds of
formula Ia and IIa wherein: from 30 to 40 mol % of all R groups are
pentanoyl, from 15 to 25 mol % of all R groups are C.sub.7
heptanoyl, from 15 to 25 mol %, of all R groups are C.sub.9
nonanoyl, and the remainder of R groups are selected from hexanoyl
and octanoyl.
10. The mechanical device according to claim 1 wherein the fluid
coupling is torque converter.
11. The mechanical device according to claim 10 which is an
automatic transmission.
12. The automatic transmission according to claim 11 which is an
automatic transmission in a racing vehicle, pickup truck, off road
vehicle, delivery truck, ATV, or monster truck.
13. The automatic transmission according to claim 12 which is an
automatic transmission in a car used in drag racing or monster
truck.
14. An improved method for operating an automatic transmission
comprising a fluid coupling and a hydraulic transfer fluid, the
improvement being selecting as the hydraulic transfer fluid a
working fluid comprising: i) from 80 to 99% by weight of a polyol
ester composition comprising C.sub.5-10 alkylcarboxlate esters of
pentaerythritol, di-pentaerythritol, tri-pentaerythritol and/or
higher pentaerythritol oligomers; and ii) from 1 to 20% by weight
of additives selected from dispersants; anti-wear agents;
anti-oxidants; corrosion inhibitors; friction modifiers; seal swell
agents; anti-foamants viscosity modifiers, detergents, pour point
depressants; wherein the working fluid has a kinematic viscosity at
40.degree. C. of from 4 to 64 cSt, a kinematic viscosity at
100.degree. C. of from 2 to 28 cSt, and a viscosity index of
greater than greater than 100.
15. The improved method according to claim 14 wherein 80 to 100% by
weight of the esters of the polyol ester composition (i) are
compounds of formula Ia and IIa ##STR00005## wherein each R is
independently selected from the group consisting of pentanoyl,
hexanoyl, heptanoly, octanoyl, nonanoyl, decanoyl and branched
isomers thereof.
16. The improved method according to claim 15 wherein 80 to 100 mol
% of the R groups in formula (Ia) and (IIa) are linear
alkanoyl.
17. The improved method according to claim 16 wherein 90 to 100% of
the esters of the polyol ester composition (i) are compounds of
formula Ia and IIa in a weight ratio of compounds of formula Ia to
IIa of from 6:1 to 15:1.
18. The improved method according to claim 17 wherein the polyol
ester composition (i) of the working fluid comprises compounds of
formula Ia and IIa wherein: a) from 5 to 45 mol% of all R groups
are C.sub.5 alkanoyl; b) from 5 to 45 mol %, of all R groups are
C.sub.6 alkanoyl; c) from 5 to 45 mol %, of all R groups are
C.sub.7 alkanoyl; d) from 5 to 45 mol %, of all R groups are
C.sub.8 alkanoyl; e) from 5 to 45 mol %, of all R groups are
C.sub.9 alkanoyl; and/or f) from 5 to 45 mol %, of all R groups are
C.sub.10 alkanoyl; provided that at least 3 of a), b), c), d), e)
and f) are present in at least 5 mol %.
19. The improved method according to claim 18 wherein the polyol
ester composition (i) of the working fluid comprises compounds of
formula Ia and IIa wherein: from 25 to 40 mol % of all R groups are
C.sub.5 alkanoyl; from 15 to 30 mol %, of all R groups are C.sub.7
alkanoyl; from 15 to 30 mol %, of all R groups are C.sub.9
alkanoyl; and from 0 to 30 mol % of all R groups are selected from
C.sub.6, C.sub.8 and C.sub.10 alkanoyl
20. The improved method according to claim 19 wherein the polyol
ester composition (i) of the working fluid comprises compounds of
formula Ia and IIa wherein: from 30 to 40 mol % of all R groups are
pentanoyl, from 15 to 25 mol % of all R groups are C.sub.7
heptanoyl, from 15 to 25 mol %, of all R groups are C.sub.9
nonanoyl, and the remainder of R groups are selected from hexanoyl
and octanoyl.
Description
[0001] This application claims benefit under 35 USC 119(e) of U.S.
provisional application No. 61/764,748, filed Feb. 14, 2013, the
disclosure of which is incorporated by reference.
[0002] This invention provides a thermally stable, high performance
working fluid and a mechanical device comprising a fluid coupling
and the working fluid, suitable for use in high stress systems such
as automotive automatic transmissions operating under conditions of
high horse power and high torque, an automatic transmission
comprising a fluid coupling and said working fluid, and a method
for improved functioning of a high stress power transfer system,
e.g., an automotive automatic transmission, by adding the working
fluid of the invention to the automotive automatic transmission
prior to operation.
[0003] Transmission fluids, especially automatic transmission
fluids, are required to serve a complex mixture of functions,
including lubrication, corrosion prevention, heat dissipation, and
hydraulic transfer fluid. For example, automatic transmissions
contain a number of mechanical parts operating at close tolerances
and require a fluid to lubricate these close-fitting parts to
reduce friction and wear and keep down temperatures. Further, many
automatic transmissions are hydraulically operated, that is they
use a fluid coupling, such as a fluid flywheel or torque converter,
to replace a manually operated clutch, requiring a hydraulic fluid
to transfer energy from the engine, through the coupling, to the
final drive mechanism.
[0004] In addition to serving as lubricant and hydraulic fluid, the
automatic transmission fluid (ATF) needs to protect and preserve
seals, resist foaming, transfer heat, prevent slippage, lower heat,
maintain correct viscosity at a range of temperatures, be stable to
high shear and thermal oxidative conditions and be compatible with
standard additive packages used in the field, while preserving
smooth shift quality.
[0005] Not surprisingly, automatic transmissions are used in a
variety of applications where they are subjected to different
degrees of stress. While many people are familiar with automatic
transmissions in passenger cars, automatic transmissions are also
used in, e.g., racing vehicles, buses, on/off highway trucks,
marine propulsion systems, industrial conveyor drives, forklifts,
winches, drilling rigs, construction equipment, and railway
locomotives. Many of these uses create extremely stressful
operational conditions for the transmission and the fluid.
[0006] For example, delivery trucks, such as postal delivery
vehicles, subject transmissions to constant stopping and starting
of heavily loaded vehicles and a preponderance of low gear use and
shifting per mile driven. This creates an environment that may lead
to failure of the transmission due to high frictional heat and
wear, and breakdown of the fluid affecting both lubricating
viscosity and hydraulic transfer properties while increasing
foaming.
[0007] Another performance challenge for an ATF can be illustrated
by the demands of auto and motorcycle racing, for example, drag
racing, where automatic transmissions using torque converters
produce high stall speeds to improve off-the-line torque and to get
into the power band of the engine more quickly. That is, the car is
stopped with the engine at a high rpm (the "stall speed") to allow
for a very quick launch when the brakes are released. This is even
more advantageous for turbocharged engines, where the turbocharger
needs to be kept spinning at high rpm by a large flow of exhaust in
order to keep the boost pressure up and eliminate the turbo lag
that occurs when the engine is idling and the throttle is suddenly
opened.
[0008] In addition, continued improvements in technology are
placing automatic transmissions in situations involving higher
horsepower, higher torque and greater temperature ranges requiring
fluids which meet continually more stringent physical
tolerances.
[0009] Lubricating oils, naturally occurring and synthetic, are
often used as base oils for ATFs. Poly-alpha-olefins are commonly
employed as the base fluid, often in combination with other
lubricants. For example, US 2010/0035778, incorporated herein by
reference, discloses a power transmission fluid comprising a blend
of at least two PAOs and a viscosity improver, in particular, a
polymethacrylate.
[0010] U.S. Pat. No. 6,713,439, incorporated herein by reference,
discloses an automatic transmission fluid composition comprising
(a) from 1 to 49 wt. % of a polyalphaolefin base stock having a
kinematic viscosity at 100 C of from 40 mm.sup.2/s to 500
mm.sup.2/s; (b) from 1 to 95 wt. % of a lubricant base stock having
a kinematic viscosity at 100 C of from 2 mm.sup.2/s to 10.sup.2/s;
(c) from 1 to 49 wt. % of a polyol ester of a C.sub.5-30 aliphatic
monocarboxylic acid and a polyol, and (d) an effective amount of a
performance additive package selected from the group consisting of
automotive gear oil additive packages, manual transmission fluid
additive packages and automatic transmission fluid additive
packages, provided that the composition has a kinematic viscosity
at 100 C of at least 4 mm.sup.2. The preferred polyol esters are
esters of trimethylol propane. The ATF additive package of U.S.
Pat. No. 6,713,439 comprises from about 1 to about 20% of the
weight of the finished fluid and typically contains ashless
dispersants; anti-wear agents; anti-oxidants; corrosion inhibitors;
friction modifiers; seal swell agents; anti-foamants and sometimes
viscosity modifiers, detergents, and pour point depressants
[0011] US 2005/0277557, incorporated herein by reference, discloses
a thermally stable, friction, wear and degradation reducing
transmission fluid for use in highly stressed power transmission
systems comprising C.sub.8/C.sub.10 esters of a specific trimethyl
polyol, a unique amide containing friction modifier, a viscosity
index (VI) improver, a corrosion inhibitor, an antioxidant,
dispersants, a lubricating oil flow improver, anti-foam agents and
anti-wear additives.
[0012] U.S. Pat. No. 7,381,691, U.S. Pat. No. 5,972,854 and U.S.
Pat. No. 6,726,855, all incorporated herein by reference, disclose
various additives that can be incorporated into various lubricant
base stocks which may be used in automatic transmission fluids.
[0013] U.S. Pat. No. 6,436,881 and U.S. Pat. No. 4,826,633, each of
which is incorporated herein by reference, disclose lubricating
base stocks containing mixtures of polyol esters, including polyol
esters of pentaerythritol and di-pentaerythritol and C.sub.5-10
carboxylic acids.
[0014] Often, attempts to improve one characteristic of an ATF will
compromise another performance feature. For example, when
formulating automatic transmission fluids for fuel economy, a
common approach is to lower the viscosity of the fluid to reduce
viscous drag. However, this approach can introduce number of
potential negative side effects such as reduced lubricating film
thickness, increased leakage losses, higher oxidation due to the
lighter base stocks, etc.
[0015] It has been found that certain select mixtures of
pentaerythritol and di-pentaerythritol esters similar to those U.S.
Pat. No. 6,436,881 and U.S. Pat. No. 4,826,633, when used as the
predominate component of a working fluid, e.g., the base oil of an
automatic transmission fluid, surprisingly provide a hydraulic
fluid/lubricant with excellent properties ideally suited for
devices operated in high stress environments that employ a fluid
coupling, such as automatic transmissions used in cars, busses,
trucks, racing vehicles, industrial and construction equipment and
the like.
SUMMARY OF THE INVENTION
[0016] The present invention provides a high performance working
fluid for automatic transmissions or other mechanical energy
transfer systems that employ a fluid coupling such as a fluid
flywheel or torque converter, said working fluid comprising from 80
to 99% by weight, based on the total weight of the fluid, of
certain neopentyl esters, in particular, esters formed from
carboxylic acids and pentaerythritol, dipentaerythritol,
tripentaerythritol and/or higher pentaerythritol oligomers, and
from 1 to 20% additives such as ashless dispersants; anti-wear
agents; anti-oxidants; corrosion inhibitors; friction modifiers;
seal swell agents; anti-foamants viscosity modifiers, detergents,
pour point depressants and the like. The fluid of the invention is
well suited for use in automatic transmissions used in demanding
environments such as those involving high horse power, high torque,
heavy loads, high heat and wide temperature ranges etc.
[0017] For example, one embodiment of the invention provides a
mechanical device comprising a fluid coupling and the working fluid
of the invention. For example the device can be a transmission or
power transfer system comprising a fluid coupling as found, e.g.,
in racing vehicles, buses, on/off road trucks, marine propulsion
systems, industrial conveyor drives, forklifts, winches, drilling
rigs, construction equipment, railway locomotives etc., as well as
passenger cars. Racing vehicles include any vehicle involved in
racing, for example, dragsters, stock cars, motorcycles, trucks,
monster trucks etc. and vehicles used in off road racing, e.g.,
trucks, SUVs, all-terrain vehicles etc. On/off road trucks include
e.g., delivery trucks, pickup trucks, etc.
[0018] The working fluid of the invention typically has a kinematic
viscosity at 40.degree. C. of from 4 to 64 cSt, for example, 5 to
48 cSt or 10 to 40 cSt, and in some embodiments 12 to 32 cSt; a
kinematic viscosity at 100.degree. C. of from 2 to 28 cSt, for
example, from 2 to 10 cSt, 2 to 8 cSt, 2 to 6 cSt and in some
embodiments 4 to 8 cSt; and a viscosity index of greater than
greater than 100, generally at least 110 or 120, and in many
embodiments at least 130 or 140. The fluid is stable at high
temperatures and fluid at low temperatures with a pour point of
-25.degree. C. or lower, in many embodiments -30.degree. C. or
lower, -40.degree. C. or lower, in some embodiments -50.degree. C.
or lower.
[0019] The working fluids of the invention maintain excellent
lubricity and hydraulic energy transfer characteristics under heavy
load, high temperature, high torque and high rpm and are compatible
with standard additives common in the field. The fluid also has
excellent anti wear activity, anti-swell activity, low volatility,
low foaming, excellent resistance to oxidation, excellent heat
transfer properties and friction characteristics that allow for
lubrication at metal surfaces where needed, but which do not
interfere with the desired slip/anti-slip features related to
proper engagement of the various components of, e.g., a torque
converter.
[0020] While the working fluids of the invention possess
characteristics associated with high performance lubricants, e.g.,
anti-wear activity, anti-swell activity, low volatility, lubricity
etc., in certain aspects, existing high performance automatic
transmission fluids, using petroleum based oils, synthetic
poly-alpha olefins and synthetic esters as base oils, actually
exhibit a higher degree of activity in standard tests used in the
evaluation of commercially viable lubricants. For example,
commercial samples of high performance lubricants used in automatic
transmissions found in racing cars and trucks, e.g., monster trucks
and drag racing cars, performed at a higher level than a fluid
according to the instant invention in Cameron Plint friction
reduction and anti-wear test, and in ASTM D-4172 4-ball wear
testing.
[0021] Despite the results from these individual tests, the fluid
of the invention surprisingly delivered superior performance, e.g.,
lower temperatures and improved torque converter performance,
compared to the commercial products when tested in the automatic
transmission itself.
DESCRIPTION OF THE INVENTION
[0022] One embodiment of the invention is a mechanical system or
device, comprising a fluid coupling and a working fluid, e.g., a
hydraulic transfer fluid, said working fluid comprising: [0023] i)
from 80 to 99% by weight of a polyol ester composition comprising
predominately C.sub.4-10 alkylcarboxlate esters of pentaerythritol,
di-pentaerythritol, tri-pentaerythritol and/or higher
pentaerythritol oligomers, for example, alkylcarboxlate esters of
pentaerythritol and di-pentaerythritol; and [0024] ii) 1 to 20% by
weight of additives; wherein the working fluid has a kinematic
viscosity at 40.degree. C. of from 4 to 64 cSt, a kinematic
viscosity at 100.degree. C. of from 2 to 28 cSt, and a viscosity
index of greater than greater than 100.
[0025] Typically, the additives of (ii) are selected from ashless
dispersants; anti-wear agents; anti-oxidants; corrosion inhibitors;
friction modifiers; seal swell agents; anti-foamants viscosity
modifiers, detergents, pour point depressants and the like, but in
some cases, small amounts, e.g. less than 15 wt %, 10 wt % or 5 wt
% of other polyol esters or other lubricating oil may be included
as an additive. Most often, other lubricating oils, e.g.,
trimethylol esters or poly-alpha-olefins are absent, or present at
levels below 2 wt %.
[0026] The additives are well known in the art, many of which are
found in the references already incorporated by reference, for
example, antioxidants can include common amine, phenolic and
phosphorus anti-oxidants, corrosion inhibitors can include
triazoles, carboxylic acids etc., anti-wear agents, viscosity
improver/pour point depressant can include various esters,
phosphonic acids amines, amides methacrylates, mercaptans, alkanes,
and pyrrolidone derivatives, and so on. Ionic liquids have found
recent use in some lubricant compositions but are not a component
in the present working fluid.
[0027] For example, the high performance working fluid comprises:
[0028] i) from 80 to 99% by weight of a polyol ester composition
comprising, or consisting essentially of, C.sub.5-10alkylcarboxlate
esters of pentaerythritol and di-pentaerythritol; and [0029] ii) 1
to 20% by weight of additives typically selected from antioxidants,
corrosion inhibitors, anti-wear agents, dispersants, VI improvers,
and pour point depressants.
[0030] In many embodiments the fluid coupling of the invention is a
fluid flywheel or torque converter as found, for example, in an
automatic transmission for cars, trucks motorcycles and the like,
where the working fluid acts in large part as a hydraulic transfer
fluid.
[0031] The working fluids of the invention are particularly
valuable as automatic transmission fluids in, e.g., automatic
transmissions under high stress conditions which require the high
performance obtainable with these fluids. Obvious examples include
transmissions in racing vehicles such as those used in drag racing,
heavy duty pickup trucks, off road vehicles, delivery trucks,
monster trucks etc.
[0032] Typically the polyol ester composition comprises a mixture
of compounds of formula I
##STR00001##
wherein each R is independently an alkyl carbonyl of from 5 to 10
carbon atoms, each R.sub.1 is independently selected and is either
a group R or a substituent of formula II:
##STR00002##
wherein R is as above.
[0033] Typically the polyol ester composition comprises a mixture
of compounds of formula Ia and IIa;
##STR00003##
[0034] wherein each R is independently an alkyl carbonyl of from 5
to 10 carbon atoms, i.e., pentanoyl, hexanoyl, heptanoly, octanoyl,
nonanoyl, decanoyl and branched isomers thereof.
[0035] The ratios of the various alkyl carbonyl groups can vary
widely, but in most embodiments, there is typically no more than
75% of any single 5, 6, 7, 8, 9 or 10 carbon alkanoyl. There also
is no requirement that the composition contain each of a 5, 6, 7,
8, 9 and 10 carbon alkanoyl, although such a composition may be
present. In some embodiments the various alkanoyl groups that are
present are found in roughly equal amounts, in other embodiments,
certain alkanoyl groups may predominate. Often, however, there are
at least 3, 4 or 5 alkanoyl groups of differing numbers of carbon
atoms present in the compounds of formulas Ia and IIa.
[0036] While R can be selected from branched and unbranched alkyl
carbonyl, in many embodiments the majority of R groups are
unbranched, i.e., linear. For example, in some embodiments 60 to
100% or 70 to 100% of the R groups are linear, and in particular
embodiments 80 to 100%, 90% to 100%, or 95 to 100% of the R groups
are linear.
[0037] Often, the majority of the esters of the working fluid are
compounds of formula Ia and IIa. For example, in some embodiments
60 to 100% or 70 to 100% of the esters of the working fluid are
compounds of formula Ia and IIa and in particular embodiments 80 to
100%, 90 to 100%, or 95 to 100% of the esters of the working fluid
are compounds of formula Ia and IIa
[0038] Compounds of formula Ia are typically the major portion of
the esters, for example, ratios of compound of formula Ia to those
of IIa often range from 1.1:1 to 15:1, for example, from 1.5:1 to
12:1, from 2:1 to 10:1. For example, the ratio of compounds of
formula Ia to IIa is typically at least 2:1, 3:1, 4:1 5:1 or 6:1,
and can be as high as 15:1, 12:1, 10:1 or 8:1.
[0039] For example, in many embodiments the working fluid
comprises: [0040] i) from 80 to 99% by weight of a mixture of
compounds of formula Ia and IIa wherein: [0041] a) from 0 to 50 mol
%, 5 to 45 mol % 5 to 40 mol %, or 10 to 40 mol % of all R groups
are C.sub.5 alkanoyl; [0042] b) from 0 to 50 mol %, 5 to 45 mol % 5
to 40 mol %, or 10 to 40 mol % of all R groups are C.sub.6
alkanoyl; [0043] c) from 0 to 50 mol %, 5 to 45 mol % 5 to 40 mol
%, or 10 to 40 mol % of all R groups are C.sub.7 alkanoyl; [0044]
d) from 0 to 50 mol %, 5 to 45 mol % 5 to 40 mol %, or 10 to 40 mol
% of all R groups are C.sub.9 alkanoyl; [0045] e) from 0 to 50 mol
%, 5 to 45 mol % 5 to 40 mol %, or 10 to 40 mol % of all R groups
are C.sub.9 alkanoyl; and/or [0046] f) from 0 to 50 mol %, 5 to 45
mol %, 5 to 40 mol %, or 10 to 40 mol % of all R groups are
C.sub.10 alkanoyl; provided that at least 3 of a), b), c), d), e)
and f) are present in at least 5 mol %, and [0047] ii) from 1 to
20% additives selected from dispersants; anti-wear agents;
anti-oxidants; corrosion inhibitors; friction modifiers; seal swell
agents; anti-foamants viscosity modifiers, detergents, pour point
depressants, such as those typically found in automatic
transmission fluids.
[0048] In a particular embodiment, the polyol ester composition (i)
of the working fluid comprises compounds of formula Ia and IIa
wherein: [0049] from 25 to 40 mol % of all R groups are C.sub.5
alkanoyl; [0050] from 15 to 30 mol %, of all R groups are C.sub.7
alkanoyl; [0051] from 15 to 30 mol %, of all R groups are C.sub.9
alkanoyl; and [0052] from 0 to 30 mol % of all R groups are
selected from C.sub.6, C.sub.8 and C.sub.10 alkanoyl.
[0053] The polyester mixtures of the invention, and processes for
preparing them, are known in the art. They are however complex and
are best described as a product by process defined in part by their
physical properties. As the polyol esters are the major part of the
present working fluids, the fluid is also best described, in part,
by physical properties such as viscosities at 40.degree. C.,
100.degree. C., viscosity index and pour point. For example, the
working fluid of the invention can be defined in part as having a
kinematic viscosity at 40 .degree. C. of from 4 to 64 cSt, a
kinematic viscosity at 100.degree. C. of from 2 to 28 cSt, a
viscosity index of greater than greater than 100 and a pour point
of -25.degree. C. or lower.
[0054] In some embodiments the viscosity index is at least 110, in
others at least 120, or at least 130, and in particular embodiments
the viscosity index is 140 or higher.
[0055] Likewise, the kinematic viscosity at 40.degree. C. in some
embodiments is from 5 to 48 cSt, in others from 10 to 40 cSt, e.g.,
from 12 to 32 cSt.
[0056] In some embodiments the kinematic viscosity at 100.degree.
C. is from 2 to 10 cSt, in other embodiments from 2 to 8 or 2 to 6
cSt, e.g. from 4 to 8.
[0057] Various embodiments also include those where the pour point
is -30.degree. C. or lower, -40.degree. C. or lower and in some
embodiments -50.degree. C. or lower.
[0058] The polyol esters of the invention are present in the
working fluid in amounts of from 80 to 99 wt %. In some embodiments
the polyol esters are present at 85 wt % or more, often 90% or
more, e.g., 95% or more. While the upper limit of polyol esters is
99 wt %, upper limits of 98%, 97% or 95% are common. Likewise, the
additives may be present in amounts of 1 to 15%, 1 to 10%, 1 to 5%,
2 to 15%, 3 to 15% or 5 to 15%. The individual amounts of each
additive are those common in the art and can range from 0.01% to 7%
by weight.
[0059] The working fluids of the invention are particularly
valuable in, e.g., automatic transmissions under high stress
conditions which require the high performance obtainable with these
fluids. Obvious examples include transmissions in racing vehicles
such as those used in drag racing, heavy duty pickup trucks, off
road vehicles, delivery trucks, monster trucks etc.
[0060] Some of the particular embodiments of the invention are to
transmissions that comprise a fluid coupling, for example, a torque
converter, and a working fluid which functions at least in part as
a hydraulic transfer fluid, e.g., an automatic transmission fluid,
comprising or consisting essentially of the working fluid described
above, in particular, said transmissions designed to operate in or
more of the following conditions: [0061] A) high stall speeds as
encountered in drag racing vehicles [0062] B) high rpm, e.g., 4,000
rpm, 5,000 rpm or 6,000 rpm or higher [0063] C) high horse power,
e.g., 300, 350, 400, 450 HP or higher [0064] D) high torque, e.g.,
400, 450, 500, 600, 700, 800 ft/lb or higher [0065] E) high loads
[0066] F) significant low gear use [0067] G) more than 30, 40 or
50% stop and go conditions, or [0068] H) high temperatures or wide
temperature ranges.
EXAMPLES
[0069] In the following examples, a working fluid according to the
invention is compared to commercial fluids useful in high stress
automatic racing transmissions which operate under conditions of
high horsepower, high rpm, high torque and high temperature.
Comparative Example A is a purchased, fully formulated, commercial
product, VALVOLINE DEXRON VI AUTOMATIC TRANSMISSION FLUID, which
uses petroleum hydrotreated paraffin distillates mineral oil as the
base oil. Comparative Example B is a purchased, fully formulated,
commercial product, AMSOIL synthetic PC series compressor oil,
which uses synthetic lubricants such as poly-alpha olefins and
polyol esters as the base oil. The compressor oil is not formulated
as an automatic transmission fluid per se, but has been used in
dragsters and monster truck transmissions due to its ability to
function under high heat conditions.
[0070] The working fluid of the invention contains, by weight, 95%
of a base oil consisting essentially of esters of pentanoyl,
hexanoyl, heptanoyl, octanoyl and nonanoyl esters of formula Ia and
IIa, in a weight ratio of about 10:1 to about 15:1 of Ia to IIa
wherein, from 30 to 40 mol % of all R groups are pentanoyl, from 15
to 25 mol %, of all R groups are C.sub.7 heptanoyl, from 15 to 25
mol %, of all R groups are C.sub.9 nonanoyl, and the remainder of R
groups being selected from hexanoyl and octanoyl; and as additives
3.4% aromatic amine anti-oxidants; 1% triazole and azeleic acid
corrosion inhibitors; 0.2% anti-wear additives comprising a mixture
of ester, chloromethyl phosphonic acid and a primary amine; and
0.2% dispersant/viscosity improver/pour point depressant comprising
a polymerized/grafted mixture of methacrylates, ester, mercaptan,
heptanes, and N-vinyl-2-pyrrolidone.
Viscosity of the test fluids:
TABLE-US-00001 KV@ 40.degree. C. KV@ 100.degree. C. VI Invention 27
cSt 5.2 cSt 125 Comp A 30 cSt 6.0 cSt 150 Comp B 34 cSt 6.3 cSt
140
Transmission performance
[0071] The working fluid of the invention described above was added
to the automatic transmission comprising a torque convertor, of a
turbo charged, non-nitro driving racing vehicle and exhibited
excellent performance relative to other fluids tested. The
converter tightened with the inventive fluid, which allowed the
turbos to spool up faster with more boost; better coupling at
launch with no foaming issues was found; and the inventive fluid
resulted in a reduction in transmission fluid operating
temperatures of approximately 30.degree. F.
Cameron Plint Friction
[0072] The friction coefficient of each fluid was measured, using
standard Cameron Plint Tribology methods, at variety of
temperatures, the conditions and data are in the tables below:
Test Conditions:
TABLE-US-00002 [0073] Ramp Hold Stage load N, kg Temp .degree. C.
Time min. Time min. Frequency Hz 1 0, 0 25-35 10 5 0 2 50, 5.1
35-50 10 5 5 3 100, 10.2 50-165 60 0 5
Friction Data:
TABLE-US-00003 [0074] Friction coefficient (--) at 102.degree. C.
132.degree. C. 162.degree. C. Invention 0.095 0.105 0.115 COMP A
0.083 0.083 0.061 COMP B 0.090 0.092 0.088
Wear
[0075] The fluids were tested for anti-wear activity according to
ASTM D-4172, four ball wear test. The fluids were also tested for
anti-wear activity using a Cameron Plint TE-77 instrument by
gradually heating a sample of the fluid on a steel plate to
150.degree. C. at which temperature the sample is held for 5 min,
while a ball with a 100 Newton load is rubbed against the plate at
a frequency of 30 Hz throughout the entire heating protocol. In
each test the wear is indicated by measuring scar formation.
TABLE-US-00004 4-Ball Scar Cameron Plint Scar Invention 0.766 mm
0.966 mm COMP A 0.579 mm 0.582 mm COMP B 0.469 mm 0.392 mm
[0076] The working fluid of the invention surprisingly outperforms
the comparison fluids when used as an automatic transmission fluid
in the transmission tested even though the comparison fluids seem
to have better friction and wear properties.
* * * * *