U.S. patent application number 13/967537 was filed with the patent office on 2015-02-19 for transmission fluid compositions for improved energy efficiency.
This patent application is currently assigned to INFINEUM INTERNATIONAL LIMITED. The applicant listed for this patent is Infineum International Limited. Invention is credited to Hahn Soo Kim, Joseph R. Noles, Jr., Raymond F. Watts.
Application Number | 20150051129 13/967537 |
Document ID | / |
Family ID | 51178704 |
Filed Date | 2015-02-19 |
United States Patent
Application |
20150051129 |
Kind Code |
A1 |
Kim; Hahn Soo ; et
al. |
February 19, 2015 |
Transmission Fluid Compositions for Improved Energy Efficiency
Abstract
Transmission fluid compositions are provided having improved
power transmission properties through the presence therein of
certain defined additives, which increase the energy efficiency of
the transmission during operation. The invention further provides a
process for the manufacture of such transmission fluid
compositions, a method of improving the energy efficiency of a
transmission, and an additive concentrate for a transmission
fluid.
Inventors: |
Kim; Hahn Soo; (Bedminster,
NJ) ; Noles, Jr.; Joseph R.; (Belle Mead, NJ)
; Watts; Raymond F.; (Long Valley, NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Infineum International Limited |
Abingdon |
|
GB |
|
|
Assignee: |
INFINEUM INTERNATIONAL
LIMITED
Abingdon
GB
|
Family ID: |
51178704 |
Appl. No.: |
13/967537 |
Filed: |
August 15, 2013 |
Current U.S.
Class: |
508/391 ;
508/460 |
Current CPC
Class: |
C10M 2219/046 20130101;
C10M 2207/124 20130101; C10M 2207/262 20130101; C10M 165/00
20130101; C10N 2040/04 20130101; C10M 135/10 20130101; C10M
2205/0285 20130101; C10M 2205/028 20130101; C10N 2030/54 20200501;
C10M 2219/044 20130101; C10M 2219/044 20130101; C10N 2010/04
20130101; C10M 2219/046 20130101; C10N 2010/04 20130101; C10M
2207/124 20130101; C10N 2010/04 20130101; C10M 2207/262 20130101;
C10N 2010/04 20130101; C10M 2205/028 20130101; C10N 2070/00
20130101; C10M 2219/044 20130101; C10N 2010/04 20130101; C10M
2219/046 20130101; C10N 2010/04 20130101; C10M 2207/124 20130101;
C10N 2010/04 20130101; C10M 2207/262 20130101; C10N 2010/04
20130101; C10M 2205/028 20130101; C10N 2070/00 20130101 |
Class at
Publication: |
508/391 ;
508/460 |
International
Class: |
C10M 135/10 20060101
C10M135/10 |
Claims
1. A transmission fluid composition consisting of: (i) a
lubricating oil, or blend of lubricating oils; (ii) a viscosity
modifier additive or blend of viscosity modifier additives; (iii) a
polyalphaolefin compound or compounds; and (iv) one or more
detergent/inhibitor additives, at least one of which comprises one
or more alkaline earth metal detergent compounds, wherein the or
each polyalphaolefin compound (iii) is made by the
metallocene-catalysed polymerisation of an alphaolefin feedstock,
and wherein the total amount of the polyalphaolefin compound(s)
(iii) in the transmission fluid composition does not exceed 4
percent by weight of the composition; and wherein at least one
alkaline earth metal detergent compound is an alkaline earth metal
salicylate or sulphonate compound.
2. The transmission fluid composition of claim 2, wherein the total
amount of the polyalphaolefin compound or compounds (iii) in the
composition is in the range of 2 to 3 percent by weight of the
composition.
3. The transmission fluid of claim 1, wherein each alkaline earth
metal detergent compound present in the transmission fluid
composition is a neutral or overbased calcium salicylate
compound.
4. The transmission fluid composition of claim 1, wherein each
alkaline earth metal detergent compound present in the transmission
fluid composition is a neutral or overbased calcium salicylate
compound, and wherein the total amount of the calcium salicylate
compound(s) present is such as to provide the transmission fluid
composition with a calcium content of between 50 and 250 parts per
million by weight, per weight of the transmission fluid
composition.
5. The transmission fluid composition of claim 1, wherein the
composition is an automotive transmission fluid.
6. The transmission fluid composition of claim 1, wherein at least
one detergent/inhibitor additive (iv) also comprises one or more
dispersant, oxidation inhibitor and/or friction modifier
compounds.
7. The transmission fluid of claim 2, wherein each alkaline earth
metal detergent compound present in the transmission fluid
composition is a neutral or overbased calcium salicylate
compound.
8. The transmission fluid composition of claim 2, wherein each
alkaline earth metal detergent compound present in the transmission
fluid composition is a neutral or overbased calcium salicylate
compound, and wherein the total amount of the calcium salicylate
compound(s) present is such as to provide the transmission fluid
composition with a calcium content of between 50 and 250 parts per
million by weight, per weight of the transmission fluid
composition.
9. The transmission fluid composition of claim 2, wherein the
composition is an automotive transmission fluid.
10. The transmission fluid composition of claim 2 wherein at least
one detergent/inhibitor additive (iv) also comprises one or more
dispersant, oxidation inhibitor and/or friction modifier
compounds.
11. A process for the manufacture of a transmission fluid
composition, the composition consisting of: (i) a lubricating oil,
or blend of lubricating oils; (ii) a viscosity modifier additive or
blend of viscosity modifier additives; (iii) a polyalphaolefin
compound or compounds, each made by the metallocene-catalysed
polymerisation of an alphaolefin feedstock; and (iv) one or more
detergent/inhibitor additives, at least one of which comprises one
or more alkaline earth metal detergent compounds wherein at least
one alkaline earth metal detergent compound is an alkaline earth
metal salicylate or sulphonate compound; the process comprising the
following steps: a) obtaining (by manufacture or otherwise) a
lubricating oil or blend of lubricating oils containing no
polyalphaolefin compound(s) made by the metallocene-catalysed
polymerisation of an alphaolefin feedstock; and b) mixing with this
lubricating oil or blend of lubricating oils the following: (b)(1)
the viscosity modifier additive or blend of viscosity modifier
additives (ii), (b)(2) the polyalphaolefin compound(s) (iii) in a
total amount not exceeding 4 percent by weight of the transmission
fluid composition, and (b)(3) one or more detergent/inhibitor
additives (iv); to provide the transmission fluid composition.
12. The process of claim 11, wherein the total amount of the
polyalphaolefin compound or compounds (iii) mixed with the
lubricating oil or blend of lubricating oils is in the range of 2
to 3 percent by weight of the transmission fluid composition.
13. The process of claim 11, wherein each alkaline earth metal
detergent compound mixed with the transmission fluid composition is
a neutral or overbased calcium salicylate compound.
14. The process of claim 11, each alkaline earth metal detergent
compound mixed with the transmission fluid composition is a neutral
or overbased calcium salicylate compound, and wherein the total
amount of calcium salicylate compound(s) mixed with the lubricating
oil or blend of lubricating is such as to provide the transmission
fluid composition with a calcium content of between 50 and 250
parts per million by weight, per weight of the transmission fluid
composition.
15. The process of claim 11, wherein the transition fluid
composition is an automotive transmission fluid.
16. The process of claim 11, wherein the additions in step b)
improve the efficiency of power transmission provided by the
composition when in use as an automotive transmission fluid, as
demonstrated by an increase in the fuel efficiency of the vehicle
during operation.
17. The process of claim 12, wherein the polyalphaolefin
compound(s) (iii) are mixed with one or more of the
detergent/inhibitor additives (iv) to form a single additive
concentrate prior to addition to the lubricating oil or blend of
oils.
18. The process of claim 12, wherein each alkaline earth metal
detergent compound mixed with the transmission fluid composition is
a neutral or overbased calcium salicylate compound.
19. The process of claim 12, each alkaline earth metal detergent
compound mixed with the transmission fluid composition is a neutral
or overbased calcium salicylate compound, and wherein the total
amount of calcium salicylate compound(s) mixed with the lubricating
oil or blend of lubricating is such as to provide the transmission
fluid composition with a calcium content of between 50 and 250
parts per million by weight, per weight of the transmission fluid
composition.
20. The process of claim 12, wherein the transition fluid
composition is an automotive transmission fluid.
21. The process of claim 12, wherein the additions in step b)
improve the efficiency of power transmission provided by the
composition when in use as an automotive transmission fluid, as
demonstrated by an increase in the fuel efficiency of the vehicle
during operation.
22. The process of claim 12, wherein the polyalphaolefin
compound(s) (iii) are mixed with one or more of the
detergent/inhibitor additives (iv) to form a single additive
concentrate prior to addition to the lubricating oil or blend of
oils.
23. A method of improving the energy efficiency of a transmission,
comprising the use therein of the transmission fluid composition
defined in claim 1.
24. The method of claim 23, wherein the transmission is a
transmission for an automotive vehicle, and the improvement in
energy efficiency is an increase in fuel economy of the vehicle
during operation.
25. A method of improving the energy efficiency of a transmission,
comprising the use therein of the transmission fluid composition
obtained by the process of claim 11.
26. The method of claim 25, wherein the transmission is a
transmission for an automotive vehicle, and the improvement in
energy efficiency is an increase in fuel economy of the vehicle
during operation.
27. An additive concentrate for a transmission fluid, the
concentrate consisting of a suitable carrier liquid, (ii) a
viscosity modifier or blend of viscosity modifiers, and (iii) a
polyalphaolefin compound or mixture of polyalphaolefin compounds
made by the metallocene-catalysed polymerisation of an alphaolefin
feedstock, and (iv) one or more detergent/inhibitor additives, at
least one of which comprises one or more alkaline earth metal
detergent compounds wherein at least one alkaline earth metal
detergent compound is an alkaline earth metal salicylate or
sulphonate compound.
28. The additive composition of claim 27 wherein the total amount
of polyalphaolefin compound(s) (iii) present in the concentrate is
such that, after addition of the concentrate at its specified treat
rate to the transmission fluid, said compounds (iii) constitute no
more than 4 percent by weight of the resulting transmission fluid
composition.
29. The additive concentrate of claim 27, wherein each alkaline
earth metal detergent compound present in the concentrate is a
neutral or overbased calcium salicylate compound.
30. The additive concentrate of claim 27, wherein the total amount
of the polyalphaolefin compound or compounds (iii) in the
concentrate is such that, after addition of the concentrate at its
specified treat rate to the transmission fluid, said compounds
(iii) constitute 2 to 3 percent by weight of the resulting
transmission fluid composition.
31. The additive concentrate of claim 28, wherein each alkaline
earth metal detergent compound present in the concentrate is a
neutral or overbased calcium salicylate compound.
32. The additive concentrate of claim 28, wherein the total amount
of the polyalphaolefin compound or compounds (iii) in the
concentrate is such that, after addition of the concentrate at its
specified treat rate to the transmission fluid, said compounds
(iii) constitute 2 to 3 percent by weight of the resulting
transmission fluid composition.
Description
[0001] The present invention provides transmission fluid
compositions having improved power transmission properties through
the presence therein of certain defined additives. In particular,
the invention provides transmission fluid compositions for
automotive vehicles, the use of which demonstrably increase the
fuel efficiency of the vehicle during operation. The invention
further provides a process for the manufacture of such transmission
fluid compositions, a method of improving the energy efficiency of
a transmission, and an additive concentrate for a transmission
fluid, and other aspects as hereinafter described.
[0002] Political, regulatory and consumer pressures abound to
increase the energy efficiency of the modern world. Machines for
many applications rely on co-operation between moving parts to
transmit power from drive units to driven units, and the efficiency
of this power transmission contributes to the overall energy
efficiency of the machine. The pursuit of ever more
energy-efficient machines has become a constant goal in many
industry sectors.
[0003] In the automotive sector, power transmission occurs
primarily through the drive-train components of the vehicle. The
crankshaft of the engine is typically coupled to the transmission
through some form of clutch, with power transmission occurring
across the clutch to drive the transmission and ultimately the
wheels. Further clutches may be present within the transmission
depending upon the design of the vehicle and its transmission type.
An essential characteristic of such clutches is their ability to
efficiently transmit power across the contact between the clutch
plates. Any losses in power transmission between the engine and
wheels results in reduced energy efficiency for the vehicle, as
demonstrated for example by poorer fuel efficiency.
[0004] Improving the energy efficiency of transmissions via the
transmission fluid presents challenges different to improving the
energy efficiency of an engine. In general terms, energy losses
occur in moving engine parts due to friction. A common goal in the
lubrication of engines is therefore to reduce friction and, in so
doing, reduce attendant energy losses. In contrast, transmissions
function by transmitting power across moving surfaces via high
friction. Therefore, creating an environment of low friction
between these surfaces would lead to a loss of energy transfer
between the surfaces and attendant loss in power transmitted by the
transmission. At the same time, however, wear must be controlled.
Thus, the formulation of effective transmission fluids having a
beneficial balance of clutch friction, wear, fatigue prevention and
energy efficiency is a complex task, and not one that readily lends
itself to routine analysis.
[0005] There remains in the art a need for improved transmission
fluids which, in use, lead to increased energy efficiency of the
attendant power transmitting device. In particular, there remains a
need in the art for automotive transmission fluids which lead to
increased fuel efficiency for the vehicle during operation.
[0006] An approach to this problem described in the art concerns
the modification of transmission fluid viscosity through the use of
viscosity modifiers. By altering the viscometric properties of the
fluid, i.e. lowering the fluid viscosity, some benefits in fuel
efficiency have been seen in given cases. However, this effect has
been attributed to the physical impact of altered bulk liquid
viscometrics, and has been associated with a number of
disadvantages such as durability of mechanical parts and
reliability of operation.
[0007] The present invention concerns transmission fluid
compositions having improved power transmission properties through
the presence therein of certain defined additives. In particular,
the invention provides transmission fluids for automotive vehicles,
the use of which demonstrably increase the fuel efficiency of the
vehicle during operation.
[0008] In particular, the present invention has determined that a
class of polyalphaolefin polymer made by a particular form of
polymerisation reaction has utility as a performance-enhancing
additive for transmission fluids, when present in conjunction with
one or more viscosity modifiers and specific detergent compounds,
wherein the combination functions to improve the power transmission
properties of the fluid. This combination of additives enables the
transmission to operate with greater energy efficiency, as
demonstrated for example by an increase in the fuel efficiency of
the vehicle during operation. The polyalphaolefin shows
advantageous performance as an additive for this purpose when used
in an amount that does not exceed 4 percent by weight of the total
transmission fluid composition, and optimal performance when used
in an amount in the range of 1 to 3 percent by weight of the total
transmission fluid composition.
[0009] As the examples hereafter demonstrate, the energy efficiency
benefit arising from the combination of polyalphaolefin, viscosity
modifier and specific detergent compound is manifest even under
conditions in which the main viscometric properties of the fluids
under comparison (kinematic viscosity and viscosity index) have
been controlled to remain essentially constant. Thus, the
fundamental effect of the additive combination is seen to operate
independent of fluid viscosity per se. The improvement in energy
efficiency attributable to the combination of additives essential
to the invention is thus attributed to a mechanism different from
simply lowering the fluid viscosity by the approach known in the
art.
[0010] US-A-2010/0035778 provides a composition for a power
transmitting fluid that has inter alia improved fuel economy which
preferably comprises an additive and a base stock having a
polyalphaolefin blend. The additive preferably includes inter alia
a viscosity index improver. This teaching reports the use of a
basestock that includes a polyalphaolefin (PAO) or PAO blend that
has an unconventional viscosity profile, and recites a fluid
composition having from about 8% to about 90% by weight of the PAO
blend. The worked example of the composition contains 77.4% by
weight of the PAO blend, being comprised of PAO 2 cSt and PAO 6 cSt
in proportions of 9.4% and 68.0% by weight respectively, along with
a viscosity modifier and detergent additive. This teaching reports
that any number of PAOs may be employed so long as the PAO blend is
selected such that the base viscosity of the fluid is greater than
or equal to 4.0 cSt at 100.degree. C. This teaching fails to
conceptually recognise the benefit arising from use of a specific
polyalphaolefin at additive treat levels within the transmission
fluid, and again focusses on altered bulk viscometrics as the means
by which fluid performance is enhanced.
[0011] In addition, the present invention has found that the
additional presence of at least one detergent additive which
comprises one or more alkaline earth metal detergent compounds,
wherein at least one alkaline earth metal detergent compound is an
alkaline earth metal salicylate or sulphonate compound, optimises
the improvement in energy efficiency achieved through use of the
resulting transmission fluid composition, and in particular
optimises the fuel efficiency of the vehicle. Preferably, each
alkaline earth metal detergent compound present in the transmission
fluid composition is a neutral or overbased calcium salicylate
compound, and more preferably the total amount of these calcium
salicylate compound(s) is such as to provide the transmission fluid
composition with a calcium content of between 50 and 250 parts per
million by weight, per weight of the transmission fluid
composition.
[0012] US-A-2010/0035778, referred to above, also fails to foresee
that these specific detergent compounds enhance fuel efficiency
when used in conjunction with the specific polyalphaolefin and the
viscosity modifier, as demonstrated in the examples below.
[0013] In addition, as a preferred optimisation, the present
invention has found that the nature of the viscosity modifier used
in combination with the defined polyalphaolefin influences the
optimal degree of improvement in energy efficiency achieved through
use of the resulting transition fluid composition, and in
particular the degree of improvement in fuel efficiency of the
vehicle. As described hereinafter, different viscosity modifiers
demonstrate differential improvements in combination with the
polyalphaolefin when compared in formulated oils having equivalent
viscometric properties. This further improvement in efficiency is
therefore attributable to the nature of the viscosity modifier per
se rather than to differential viscosity modification effects.
[0014] In a first aspect therefore, the present invention provides
a transmission fluid composition consisting of:
[0015] a lubricating oil, or blend of lubricating oils; [0016] (ii)
a viscosity modifier additive or blend of viscosity modifier
additives; [0017] (iii) a polyalphaolefin compound or compounds;
and [0018] (iv) one or more detergent/inhibitor additives, at least
one of which comprises one or more alkaline earth metal detergent
compounds, wherein the or each polyalphaolefin compound (iii) is
made by the metallocene-catalysed polymerisation of an alphaolefin
feedstock, and wherein the total amount of the polyalphaolefin
compound(s) (iii) in the transmission fluid composition does not
exceed 4 percent by weight of the composition; and wherein at least
one alkaline earth metal detergent compound is an alkaline earth
metal salicylate or sulphonate compound.
[0019] The, or each, polyalphaolefin compound (iii) is made by a
polymerisation reaction in which the corresponding alphaolefin
feedstock is polymerised through the action of a metallocene
catalyst. Such polyalphaolefins are known per se, and are sometimes
referred to in the polymer art as "mPAO". They possess a structure
different from polyalphaolefins derived from other catalytic
processes. In particular, the action of the metallocene catalyst is
such as to cause the formation of a polymer product having a narrow
molecular weight distribution, and a structure that embodies a high
proportion of head-to-tail monomer unit additions, i.e. can be
regarded as an essentially ideal polymer. The literature for such
materials also reports a more ordered pattern of hydrocarbon side
chains with fewer short side chains than other processes. The
result is a polymer with a more "perfect" structure and different
properties.
[0020] The present invention has determined that such
polyalphaolefins show a particular benefit when used as
performance-enhancing additives in transmission fluid compositions.
As illustrated in the examples which follow, the additive benefit
from such polyalphaolefins is seen at a treat rate of not more than
4 percent by weight of the total transmission fluid composition,
preferably between 1 and 3 percent by weight, and optimally between
2 and 3 percent by weight. Such treat rates correspond to typical
additive treat rates in such fluids, and are not to be confused
with the use of synthetic polymers as lubricating oils per se
(sometimes called "basestocks") or as basestock blending
components, which involve the incorporation of larger relative
quantities of polymer for constituting the bulk volume of base
lubricating oil.
[0021] In a second aspect, the present invention provides a process
for the manufacture of a transmission fluid composition, the
composition consisting of: [0022] (i) a lubricating oil, or blend
of lubricating oils; [0023] (ii) a viscosity modifier additive or
blend of viscosity modifier additives; [0024] (iii) a
polyalphaolefin compound or compounds, each made by the
metallocene-catalysed polymerisation of an alphaolefin feedstock;
and [0025] (iv) one or more detergent/inhibitor additives, at least
one of which comprises one or more alkaline earth metal detergent
compounds wherein at least one alkaline earth metal detergent
compound is an alkaline earth metal salicylate or sulphonate
compound; the process comprising the following steps: a) obtaining
(by manufacture or otherwise) a lubricating oil or blend of
lubricating oils containing no polyalphaolefin compound(s) made by
the metallocene-catalysed polymerisation of an alphaolefin
feedstock; and b) mixing with this lubricating oil or blend of
lubricating oils the following: [0026] (b)(1) the viscosity
modifier additive or blend of viscosity modifier additives (ii),
[0027] (b)(2) the polyalphaolefin compound(s) (iii) in a total
amount not exceeding 4 percent by weight of the transmission fluid
composition, and [0028] (b)(3) one or more detergent/inhibitor
additives (iv); to provide the transmission fluid composition.
[0029] In particular, the process of the present invention is
employed to manufacture an automotive transmission fluid, and in
particular wherein the additions in step b) improve the efficiency
of power transmission provided by the resulting composition when
used in the vehicle, as demonstrated by an increase in the fuel
efficiency of the vehicle during operation.
[0030] In a third aspect, the present invention provides a method
of improving the energy efficiency of a transmission, comprising
the use therein of the transmission fluid composition defined in
the first aspect or of the transmission fluid composition obtained
by the process of the second aspect. In this aspect of the
invention, the transmission is preferably a transmission for an
automotive vehicle, and the improvement in energy efficiency is
preferably an increase in fuel economy of the vehicle during
operation.
[0031] In a fourth aspect, the invention provides an additive
concentrate for a transmission fluid, the concentrate consisting of
a suitable carrier liquid, (ii) a viscosity modifier or blend of
viscosity modifiers, and (iii) a polyalphaolefin compound or
mixture of polyalphaolefin compounds made by the
metallocene-catalysed polymerisation of an alphaolefin feedstock,
and (iv) one or more detergent/inhibitor additives, at least one of
which comprises one or more alkaline earth metal detergent
compounds wherein at least one alkaline earth metal detergent
compound is an alkaline earth metal salicylate or sulphonate
compound. Preferably the total amount of polyalphaolefin
compound(s) (iii) present in the concentrate is such that, after
addition of the concentrate at its specified treat rate to the
transmission fluid, said compounds (iii) constitute no more than 4
percent by weight of the resulting transmission fluid
composition.
[0032] The present invention is hereinafter described in more
detail.
[0033] The transmission fluid composition consists of four
essential elements (i), (ii), (iii) and (iv). The components are:
[0034] (i) a lubricating oil, or blend of lubricating oils; [0035]
(ii) a viscosity modifier additive or blend of viscosity modifier
additives; [0036] (iii) a polyalphaolefin compound or compounds
made by the metallocene-catalysed polymerisation of an alphaolefin
feedstock; and [0037] (iv) one or more detergent/inhibitor
additives, at least one of which comprises one or more alkaline
earth metal detergent compounds, wherein at least one alkaline
earth metal detergent compound is an alkaline earth metal
salicylate or sulphonate compound.
[0038] It is essential that the total amount of the polyalphaolefin
compound(s) (iii) in the transmission fluid composition does not
exceed 4 percent by weight of the composition, regardless of the
means of incorporation. Thus, in principle, it is possible in the
practice of this invention that some, or all, of the small amount
of polyalphaolefin(s) (iii) in the composition of the first aspect
may be introduced to the composition via incorporation in the
lubricating oil or oil blend (i). However, it is preferred that the
lubricating oil or oil blend component (i) per se contains no such
polyalphaolefins (iii), and that these essential compounds (iii)
are instead incorporated into the composition by direct addition as
a discrete additive in the process of manufacture of the
composition, or are mixed with the viscosity modifier additive or
blend of viscosity modifier additives (ii) to form a single
additive concentrate prior to their addition to the lubricating oil
or blend of oils. Alternatively, the polyalphaolefin compound(s)
(iii) may be mixed with one or more of the detergent/inhibitor
additive (iv) to form a single additive concentrate prior to
addition to the lubricating oil or blend of oils.
[0039] The most additive benefit from such polyalphaolefins (iii)
when used in accordance with the invention is seen at a treat rate
of below 4 percent by weight of the total transmission fluid
composition, more preferably between 1 and 3 percent by weight, and
optimally between 2 and 3 percent by weight of the total
transmission fluid composition.
[0040] The lubricating oil or oil blend (i) constitutes the bulk of
the fluid composition. Oils useful in this invention as the
lubricating oil, or for constituting the oil blend, are derived
from natural lubricating oils, synthetic lubricating oils, and
mixtures thereof. In general, both the natural and synthetic
lubricating oil will each have a kinematic viscosity ranging from
about 1 to about 100 mm.sup.2/s (cSt) at 100.degree. C. depending
on the specification or quality of transmission fluid sought,
although typical applications will require each oil to have a
viscosity ranging from about 2 to about 8 mm.sup.2/s (cSt) at
100.degree. C.
[0041] Natural lubricating oils include animal oils, vegetable oils
(e.g., castor oil and lard oil), petroleum oils, mineral oils, and
oils derived from coal or shale. The preferred natural lubricating
oil is mineral oil.
[0042] Suitable mineral oils include all common mineral oil
basestocks. This includes oils that are naphthenic or paraffinic in
chemical structure. Oils that are refined by conventional
methodology using acid, alkali, and clay or other agents such as
aluminum chloride, or they may be extracted oils produced, for
example, by solvent extraction with solvents such as phenol, sulfur
dioxide, furfural, dichlordiethyl ether, etc. They may be
hydrotreated or hydrofined, dewaxed by chilling or catalytic
dewaxing processes, or hydrocracked. The mineral oil may be
produced from natural crude sources or be composed of isomerized
wax materials or residues of other refining processes.
[0043] Typically the mineral oils will have kinematic viscosities
of from 2.0 mm.sup.2/s (cSt) to 10.0 mm.sup.2/s (cSt) at
100.degree. C. The preferred mineral oils have kinematic
viscosities of from 2 to 8 mm.sup.2/s (cSt), and most preferred are
those mineral oils with viscosities of 3 to 6 mm.sup.2/s (cSt) at
100.degree. C.
[0044] Synthetic lubricating oils include hydrocarbon oils and
halo-substituted hydrocarbon oils such as oligomerized,
polymerized, and interpolymerized olefins [e.g., polybutylenes,
polypropylenes, propylene, isobutylene copolymers, chlorinated
polylactenes, poly(1-hexenes), poly(1-octenes), poly-(1-decenes),
etc., and mixtures thereof]; alkylbenzenes (e.g., dodecyl-benzenes,
tetradecylbenzenes, dinonyl-benzenes, di(2-ethylhexyl)benzene,
etc.); polyphenyls (e.g., biphenyls, terphenyls, alkylated
polyphenyls, etc.); and alkylated diphenyl ethers, alkylated
diphenyl sulfides, as well as their derivatives, analogs, and
homologs thereof, and the like.
[0045] The preferred oils from this class of synthetic oils are
Group IV basestocks, i.e. polyalphaolefins (PAO), including
hydrogenated oligomers of an alpha-olefin, particularly oligomers
of 1-decene, especially those produced by free radical processes,
Ziegler catalysis, or cationic, Friedel-Crafts catalysis.
[0046] The polyalphaolefins typically have viscosities in the range
of 2 to 20 cSt at 100.degree. C., preferably 4 to 8 cSt at
100.degree. C. They may, for example, be oligomers of branched or
straight chain alpha-olefins having from 2 to 16 carbon atoms,
specific examples being polypropenes, polyisobutenes,
poly-1-butenes, poly-1-hexenes, poly-1-octenes and poly-1-decene.
Included are homopolymers, interpolymers and mixtures.
[0047] As explained earlier however, in the context of the present
invention, should the lubricating oil or lubricating oil blend (i)
be additionally constituted from any polyalphaolefin (iii), i.e.
mPAO made by the metallocene-catalysed polymerisation of an
alphaolefin feedstock; it is important that such polyalphaolefins
(iii) do not collectively contribute more than 4% by weight of the
total transmission fluid composition. Preferably, any and all
polyalphaolefin(s) constituting the lubricating oil or lubricating
oil blend (i) are not made by the metallocene-catalysed
polymerisation of an alphaolefin feedstock.
[0048] Synthetic lubricating oils also include alkylene oxide
polymers, interpolymers, copolymers, and derivatives thereof where
the terminal hydroxyl groups have been modified by esterification,
etherification, etc. This class of synthetic oils is exemplified
by: polyoxyalkylene polymers prepared by polymerization of ethylene
oxide or propylene oxide; the alkyl and aryl ethers of these
polyoxyalkylene polymers (e.g., methyl-polyisopropylene glycol
ether having an average molecular weight of 1000, diphenyl ether of
polypropylene glycol having a molecular weight of 1000-1500); and
mono- and poly-carboxylic esters thereof (e.g., the acetic acid
esters, mixed C.sub.3-C.sub.8 fatty acid esters, and C.sub.12 oxo
acid diester of tetraethylene glycol).
[0049] Another suitable class of synthetic lubricating oils
comprises the esters of dicarboxylic acids (e.g., phthalic acid,
succinic acid, alkyl succinic acids and alkenyl succinic acids,
maleic acid, azelaic acid, suberic acid, sebasic acid, fumaric
acid, adipic acid, linoleic acid dimer, malonic acid, alkylmalonic
acids, alkenyl malonic acids, etc.) with a variety of alcohols
(e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl
alcohol, ethylene glycol, diethylene glycol monoethers, propylene
glycol, etc.). Specific examples of these esters include dibutyl
adipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl
sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl
phthalate, didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl
diester of linoleic acid dimer, and the complex ester formed by
reacting one mole of sebasic acid with two moles of tetraethylene
glycol and two moles of 2-ethyl-hexanoic acid, and the like. A
preferred type of oil from this class of synthetic oils is adipates
of C.sub.4 to C.sub.12 alcohols.
[0050] Esters useful as synthetic lubricating oils also include
those made from C.sub.5 to C.sub.12 monocarboxylic acids and
polyols and polyol ethers such as neopentyl glycol,
trimethylolpropane pentaerythritol, dipentaerythritol,
tripentaerythritol, and the like.
[0051] The lubricating oils may be derived from refined, rerefined
oils, or mixtures thereof. Unrefined oils are obtained directly
from a natural source or synthetic source (e.g., coal, shale, or
tar sands bitumen) without further purification or treatment.
Examples of unrefined oils include a shale oil obtained directly
from a retorting operation, a petroleum oil obtained directly from
distillation, or an ester oil obtained directly from an
esterification process, each of which is then used without further
treatment. Refined oils are similar to the unrefined oils except
that refined oils have been treated in one or more purification
steps to improve one or more properties. Suitable purification
techniques include distillation, hydrotreating, dewaxing, solvent
extraction, acid or base extraction, filtration, and percolation,
all of which are known to those skilled in the art. Rerefined oils
are obtained by treating used oils in processes similar to those
used to obtain the refined oils. These rerefined oils are also
known as reclaimed or reprocessed oils and are often additionally
processed by techniques for removal of spent additives and oil
breakdown products.
[0052] Another class of suitable lubricating oils are those
basestocks produced from oligomerization of natural gas feed stocks
or isomerization of waxes. These basestocks can be referred to in
any number of ways but commonly they are known as Gas-to-Liquid
(GTL) or Fischer-Tropsch base stocks.
[0053] The lubricating oil (i) may be a blend of one or more of the
above described oils, and a blend of natural and synthetic
lubricating oils (i.e., partially synthetic) is expressly
contemplated under this invention.
[0054] The viscosity modifier or blend of viscosity modifiers (ii)
may be a single compound or a blend of compounds capable of
modifying the viscosity of lubricating oil when added thereto, so
as to make its viscosity profile more advantageous for lubricant
function. Typically, lubricating oils experience a range of
operating temperatures within the device being lubricated and, as
viscosity is a temperature-dependent characteristic, must therefore
maintain an appropriate viscosity throughout the range of operating
temperatures, such that the oil neither becomes too viscous
(`thick`) at lower temperatures to cause viscous drag in the
device, nor too thin to provide adequate lubrication at higher
temperatures. Viscosity modifiers typically have the property of
increasing the viscosity of the oil at higher temperatures, so
offsetting the natural thinning of the lubricant base-stock, whilst
having lesser (or no) thickening effect at lower temperatures, so
as to not contribute substantially to viscous drag. In addition,
preferred viscosity modifiers show a greater resistance to loss of
activity over time, when exposed to the shear forces and other
degrading effects that a lubricant experiences during the rigours
of operation.
[0055] The viscosity modifier or blend of viscosity modifiers
suitable for use as component (ii) of the invention is thus, in its
broadest aspect, any viscosity modifier capable of reducing the
temperature-dependent variation in viscosity inherent in the
lubricating oil (or blend of lubricating oils). However, in the
practice of the invention, we have found that certain classes of
viscosity modifier are especially suitable in combination with
components (i), (iii) and (iv) to provide transmission fluid
compositions with the advantages of the present invention.
[0056] Thus, the viscosity modifier or blend of viscosity modifiers
(ii) is preferably a polymer or blend of polymers derived from one
or more olefin or unsaturated ester monomers; and more preferably a
polymer or blend of polymers derived from one or more olefin
monomers, or from one or more .alpha., .beta.-unsaturated ester
monomers such as alkyl acrylates and alkyl methacrylates, or from
one or more olefins and one or more .alpha., .beta.-unsaturated
ester monomers such as alkyl acrylates and alkyl methacrylates.
[0057] Most preferably, the viscosity modifier or blend of
viscosity modifiers (ii) is a polymer or blend of polymers selected
from one or more of the following groups:
[0058] (ii)(a) random or block poly-alkylacrylates or
poly-alkylmethacrylates, or copolymers thereof;
[0059] (ii)(b) star polymers comprising a polyvalent core of
polyalkylacrylate or polyalkylmethacrylate from which a plurality
or arms depend, the arms being polymer chains containing
alkylacrylate or alkylmethacrylate ester monomer units; and
[0060] (ii)(c) comb polymers prepared by the copolymerisation of
one or more alkylacrylate or alkylmethacrylate monomers with one or
more olefin or polyolefin monomers.
[0061] Materials in group (ii)(a) are prepared by the
polymerisation of one or more alkylacrylate or alkylmethacrylate
monomers, wherein the alkyl groups preferably contain from 1 to 20,
more preferably 1 to 10 carbon atoms, using techniques known in the
art, such as radical polymerisation. Such materials are known in
the art and are commercially available, an example being
VISCOPLEX.RTM. 12-075 supplied by Evonik Rohmax USA, Inc.
[0062] Materials in the group (ii)(b) are prepared by the stepwise
polymerisation of a core portion from one or more alkylacrylate or
alkylmethacrylate monomers, wherein the alkyl groups preferably
contain from 1 to 30, more preferably 1 to 20 carbon atoms,
followed by further polymerisation with such monomers to form the
pendant arms. Suitable processes include atom transfer radical
polymerisation (ATRP) and reversible addition-fragmentation chain
transfer (RAFT) polymerisation. Alternatively the arms can be
separately formed and attached to the core via reaction at the
linking groups. Such materials are known in the art.
[0063] Materials in the group (ii)(c) are most conveniently
prepared by radical polymerisation. The term "comb" is known in the
polymer art, and refers to the comb-like architecture of the
polymer which possesses a series of side-chains depending from the
main backbone chain, these side-chains being formed either from the
alkyl substituents of the alkyl acrylate or methacrylate monomer
units, or from the residues of the olefin monomers, or both.
[0064] Preferably, where the comb polymer (ii)(c) is prepared from
one or more alkylacrylate or alkylmethacrylate monomers, it is
formed by the polymerisation of one or more alkylacrylate or
alkylmethacrylate monomers wherein the alkyl chains contain between
4 and 20 carbon atoms, preferably by radical polymerisation.
[0065] Preferably, where the comb polymer (ii)(c) is prepared from
one or more olefin or polyolefin monomers, it is formed by the
polymerisation of one or more olefin monomers containing between 4
and 20, such as 4 to 12, carbon atoms. Alternatively, it may be
prepared from one or more polyolefin macromonomers providing alkyl
or alkenyl groups of considerable size, which form the side-chains
of the resulting comb polymer structure.
[0066] More preferably, the comb polymer (ii)(c) is prepared by the
copolymerisation of one or more alkylacrylate or alkylmethacrylate
monomers with one or more olefin or polyolefin monomers. In such
polymers, the backbone is formed by the co-polymerising
(meth)acrylate and olefin or polyolefin monomer units, with the
alkyl ester groups of the (meth)acrylate units and the residues of
the olefin or polyolefin depending from the resulting backbone to
form the comb structure. In such structures, the alkyl groups of
the alkylacrylate or alkylmethacrylate monomers preferably contain
between 4 and 20, such as 8 to 18, carbon atoms; whilst the
co-monomer is preferably an olefin or polyolefin providing a longer
dependant chain to the resulting copolymer, such as a long chain
alpha-olefin or a polyolefin macromonomer such as poly(isobutylene)
or hydrogenated poly(butadiene). Further olefinically-unsaturated
comonomers may be used in the preparation, for example styrene or
a, 13 unsaturated esters. When present in the lubricating oil, such
polymers are capable of significant expansion when energy is
applied (such as occurs when the oil heats up during operation),
and this thermal expansion behaviour enables them to entrain more
oil within a fluid network of extended comb structures, and so
oppose the thinning in oil viscosity that otherwise typically
occurs with increasing temperature. Such materials are described,
for example, in the SAE paper entitled "A New Generation of High
Performance Viscosity Modifiers Based on Comb Polymers" by Stoehr,
Eisenberg and Mueller, published in SAE Int. J Fuels Lubr., Volume
1, Issue 1, 1511 and numbered as 2008-0102462, and in
US-A-2010/0190671 which describes their nature and preparation.
[0067] The polyalphaolefin compound or compounds (iii) are those by
the metallocene-catalysed polymerisation of an alphaolefin
feedstock. Such "mPAO" materials are known in the art per se and
are described, for example, in US-A-2007/145924 along with their
method of manufacture via metallocene catalysis. In this reference
they are described as a lubricant base-stock component and used
primarily to make high viscosity basestock blends. They are for
example available to the skilled person as items of commerce under
the name "SpectraSyn Elite.TM." from ExxonMobil Chemical Company
and its regional sales affiliates, and further disclosed in the art
at the date of filing at the following web address:
http://www.exxonmobilchemical.com/Chem-English/brands/spectrasyn-elite-mp-
ao.aspx?ln=productsservices under the description of "Advanced
synthetic basestock". The performance advantages of SpectraSyn
Elite.TM. as a lubricant basestock are described in that reference
as shear stability, viscosity index for high and low temperature
performance, and increased flow in cold environments. The reference
also explains that the use of metallocene catalysis in the
manufacture of the mPAO results in a particular molecular structure
in the polymer product.
[0068] In the present invention, the polyalphaolefin compound(s)
(iii) are used in additive quantities in the transmission fluid
composition in combination with a viscosity modifier additive or
blend of viscosity modifier additives (ii) and specific detergent
additives(s) (iv) to improve the energy efficiency of a
transmission utilising said fluid. Metallocene-made
polyalphaolefins (iii) having characteristics particularly suitable
for the practice of this invention can be produced from a feedstock
containing one or more, preferably two or more, linear C.sub.6 to
C.sub.18 alphaolefins. Preferred polyalphaolefins (iii) are those
made from a feedstock mixture of C.sub.6 and C.sub.18 linear
alphaolefins or a mixture of C.sub.6 and C.sub.12 alphaolefins. The
feedstock is typically contacted with an activated metallocene
catalyst under polymerisation conditions known in the art, to give
the compounds (iii). In the preferred embodiment of the invention,
and the examples which follow hereafter, the invention employs
SpectraSyn Elite.TM. 150 as the polyalphaolefin (iii). This
material is available as an item of commerce through the above
source according to a published specification, and has a typical
kinematic viscosity at 100.degree. C. of 156 mm.sup.2/s as measured
by ASTM D445, and a typical viscosity index of 206 as measured by
ASTM D2270, together with a pour point of minus 33.degree. C. as
measured by ASTM D5950/D97.
[0069] In addition to the essential metallocene-derived
polyalphaolefin (iii) in the requisite amount, the compositions of
the invention may, via additive (iv), additionally contain other
polyalphaolefins.
[0070] The present invention concerns transmission fluid
compositions having improved power transmission properties.
Examples of other, less preferred types of power transmitting
fluids included within the scope of this invention are gear oils,
hydraulic fluids, tractor fluids, universal tractor fluids and the
like. In particular, the invention provides transmission fluids for
automotive vehicles, the use of which demonstrably increase the
fuel efficiency of the vehicle during operation. Thus, the
transmission fluid composition of the invention is preferably an
automotive transmission fluid, such as an automatic transmission
fluid (hereinafter referred to as "ATF"), continuously variable
transmission fluid ("CVTFs"), or double clutch transmission fluid
("DCTFs").
[0071] Such fluids are formulated with detergent/inhibitor
additive(s) (iv) to meet the various performance requirements
and/or specifications of a given application, especially automotive
application. Within this specification, the term
"detergent/inhibitor additive" is used to denote an additive
comprising one or more detergent compounds, and optionally other
compounds (`components`) which function as performance-enhancing
additives for transmission fluids. In the art, such detergent
additives are sometimes generally known as detergent packages or
detergent-inhibitor packages and may contain a variety of other
components and a mutually-compatible solvent or dispersion
medium.
[0072] These other components include additional detergents,
dispersants, antiwear agents, corrosion inhibitors, extreme
pressure additives, and the like. They are typically disclosed in,
for example, "Lubricant Additives" by C. V. Smallheer and R.
Kennedy Smith, 1967, pp. 1-11 and U.S. Pat. No. 4,105,571.
[0073] Representative amounts of typical components of
detergent/inhibitor additive(s) (iv) in an automotive transmission
fluid are summarized as follows:
TABLE-US-00001 Additive (Broad) Wt. % (Preferred) Wt. % Dispersants
0.10-10 2-5 Antiwear Agents 0.005-5 0.5-3 Friction modifiers 0.05-5
0.5-3.0 Corrosion Inhibitor 0.01-3 0.02-1 Antifoaming Agents
0.001-5 0.001-0.5 Pour Point Depressants 0.01-2 0.01-1.5 Seal
Swellants 0.1-8 0.5-5 Diluent Balance Balance
[0074] It is essential that at least one additive (iv) comprises
one or more alkaline earth metal detergent compounds wherein at
least one alkaline earth metal detergent compound is an alkaline
earth metal salicylate or sulphonate compound, leading to
improvement of the energy efficiency of the resulting fluid, as
hereinbefore described.
[0075] The essential detergents that are generally employed in the
invention are exemplified by oil-soluble neutral or overbased salts
of alkaline earth metals with one or more hydrocarbyl-substituted
sulfonic acids or salicylic acids. The preferred salts of such
acids from the cost-effectiveness, toxicological, and environmental
standpoints are the salts of calcium and magnesium. The preferred
salts useful with this invention are either neutral or overbased
salicylate salts of calcium or magnesium.
[0076] Oil-soluble neutral metal-containing detergents are those
detergents that contain stoichiometrically equivalent amounts of
metal in relation to the amount of acidic moieties present in the
detergent. Thus, in general the neutral detergents will have a low
basicity when compared to their overbased counterparts.
[0077] The term "overbased" in connection with metallic detergents
is used to designate metal salts wherein the metal is present in
stoichiometrically larger amounts than the organic radical. The
commonly employed methods for preparing the over-based salts
involve heating a mineral oil solution of an acid with a
stoichiometric excess of a metal neutralizing agent such as the
metal oxide, hydroxide, carbonate, bicarbonate, of sulfide at a
temperature of about 50.degree. C., and filtering the resultant
product. The use of a "promoter" in the neutralization step to aid
the incorporation of a large excess of metal likewise is known.
Examples of compounds useful as the promoter include phenolic
substances such as phenol, naphthol, alkyl phenol, thiophenol,
sulfurized alkylphenol, and condensation products of formaldehyde
with a phenolic substance; alcohols such as methanol, 2-propanol,
octanol, Cellosolve alcohol, Carbitol alcohol, ethylene glycol,
stearyl alcohol, and cyclohexyl alcohol; and amines such as
aniline, phenylene diamine, phenothiazine,
phenyl-beta-naphthylamine, and dodecylamine. A particularly
effective method for preparing the basic salts comprises mixing an
acid with an excess of a basic alkaline earth metal neutralizing
agent and at least one alcohol promoter, and carbonating the
mixture at an elevated temperature such as 60 to 200.degree. C.
[0078] Examples of suitable metal-containing detergents are neutral
and overbased salts of calcium sulfonates and magnesium sulfonates
wherein each sulfonic acid moiety is attached to an aromatic
nucleus which in turn usually contains one or more aliphatic
substituents to impart hydrocarbon solubility, and calcium
salicylates and magnesium salicylates wherein the aromatic moiety
is usually substituted by one or more aliphatic substituents to
impart hydrocarbon solubility. Mixtures of neutral or over-based
salts of two or more different alkaline earth metals can be used.
Likewise, neutral and/or overbased salts of mixtures of two or more
different acids (e.g. one or more overbased calcium salicylates
with one or more overbased calcium sulfonates) can also be
used.
[0079] As is well known, overbased metal detergents are generally
regarded as containing overbasing quantities of inorganic bases,
probably in the form of micro dispersions or colloidal suspensions.
Thus the term "oil soluble" as applied to metallic detergents is
intended to include metal detergents wherein inorganic bases are
present that are not necessarily completely or truly oil-soluble in
the strict sense of the term, inasmuch as such detergents when
mixed into base oils behave much the same way as if they were fully
and totally dissolved in the oil.
[0080] Methods for the production of these oil-soluble neutral and
overbased alkaline earth metal-containing detergents are well known
to those skilled in the art, and extensively reported in the patent
literature.
[0081] The metallic detergents utilized in this invention can, if
desired, be oil-soluble boronated neutral and/or overbased alkali
of alkaline earth metal-containing detergents. Methods for
preparing boronated metallic detergents are described in, for
example, U.S. Pat. Nos. 3,480,548; 3,679,584; 3,829,381; 3,909,691;
4,965,003; and 4,965,004.
[0082] Preferred metallic detergents for use with this invention
are calcium sulfonates and/or magnesium sulfonates, and calcium
and/or magnesium salicylates. Preferably at least one such alkaline
earth metal detergent compound is a calcium salicylate or calcium
sulphonate compound. Preferably, the total amount of the alkaline
earth metal detergent compound(s) present in the transmission fluid
composition is such as to provide the transmission fluid
composition with a an alkaline earth metal content of between 50
and 250 parts per million by weight, per weight of the transmission
fluid composition.
[0083] More preferably, each alkaline earth metal detergent
compound present in the transmission fluid composition is a neutral
or overbased calcium salicylate compound. Salicylate compounds have
been found to be particularly advantageous in combination with the
additives (ii) and (iii) described herein and contribute to the
fuel efficiency advantage of the present invention.
[0084] Most preferably each alkaline earth metal detergent compound
present in the transmission fluid composition is a neutral or
overbased calcium salicylate compound, and wherein the total amount
of the calcium salicylate compound(s) present is such as to provide
the transmission fluid composition with a calcium content of
between 50 and 250 parts per million by weight, per weight of the
transmission fluid composition, this amount having been found to
provide optimal efficiency gains.
[0085] Dispersants, specifically those characterised as ashless
dispersants, are also useful in this invention as components of
additive (iv). Suitable dispersants include long chain (i.e.
greater than forty carbon atoms) substituted hydrocarbyl
succinimides and hydrocarbyl succinamides, mixed ester/amides of
long chain (i.e. greater than forty carbon atoms)
hydrocarbyl-substituted succinic acid, hydroxyesters of such
hydrocarbyl-substituted succinic acid, and Mannich condensation
products of long chain (i.e. greater than forty carbon atoms)
hydrocarbyl-substituted phenols, formaldehyde and polyamines.
Mixtures of such dispersants can also be used.
[0086] The preferred dispersants are the long chain alkenyl
succinimides. These include acyclic hydrocarbyl substituted
succinimides formed with various amines or amine derivatives such
as are widely disclosed in the patent literature. Use of alkenyl
succinimides which have been treated with an inorganic acid of
phosphorus (or an anhydride thereof) and a boronating agent are
also suitable for use in the compositions of this invention as they
are much more compatible with elastomeric seals made from such
substances as fluoro-elastomers and silicon-containing elastomers.
Polyisobutenyl succinimides formed from polyisobutenyl succinic
anhydride and an alkylene polyamine such as triethylene tetramine
or tetraethylene pentamine wherein the polyisobutenyl substituent
is derived from polyisobutene having a number average molecular
weight in the range of 500 to 5000 (preferably 800 to 2500) are
particularly suitable. Dispersants may be post-treated with many
reagents known to those skilled in the art. (e.g., U.S. Pat. Nos.
3,254,025; 3,502,677; and 4,857,214).
[0087] Anti-wear additives useful in this invention as components
in additive (iv) are typically oil-soluble phosphorus-containing
compounds that, in the context of this invention, may vary widely
and are not limited by chemical type. The only limitation is that
the material be oil soluble so as to permit the dispersion and
transport of phosphorus-containing compound within the lubricating
oil system to its site of action. Examples of suitable phosphorus
compounds are: phosphites and thiophosphites (mono-alkyl, di-alkyl,
tri-alkyl and partially hydrolyzed analogs thereof); phosphates and
thiophosphates; amines treated with inorganic phosphorus such as
phosphorous acid, phosphoric acid or their thio analogs; zinc
dithiodiphosphates; amine phosphates. Examples of particularly
suitable phosphorus compounds include:
mono-n-butyl-hydrogen-acid-phosphite; di-n-butyl-hydrogen
phosphite; triphenyl phosphite; triphenyl thiophosphite;
tri-n-butylphosphate; dimethyl octadecenyl phosphonate, 900MW
polyisobutenyl succinic anhydride (PIBSA) polyamine dispersant post
treated with H.sub.3PO.sub.3 and H.sub.3BO.sub.3 (see, e.g., U.S.
Pat. No. 4,857,214); zinc (di-2-ethylhexyldithiophosphate).
[0088] The preferred oil soluble phosphorus compounds are the
esters of phosphoric and phosphorous acid. These materials would
include the di-alkyl, tri-alkyl and tri-aryl phosphites and
phosphates. A preferred oil soluble phosphorus compound is the
mixed thioalkyl phosphite esters, for example as produced in U.S.
Pat. No. 5,314,633, incorporated herein by reference.
[0089] The phosphorus compounds of the invention can be used in the
oil in any effective amount. However, a typical effective
concentration of such compounds would be that delivering from about
5 to about 5000 ppm phosphorus into the oil. A preferred
concentration range is from about 10 to about 1000 ppm of
phosphorus in the finished oil and the most preferred concentration
range is from about 50 to about 500 ppm.
[0090] Preferred friction modifiers useful as components in
additive (iv) comprise a reaction product of an isomerized alkenyl
substituted succinic anhydride and a polyamine characterized by
structure (I), where structure (I) is:
##STR00001##
where x and y are independent integers whose sum is from 1 to 30,
and z is an integer from 1 to 10.
[0091] The starting components for forming the structure (I)
compounds are isomerized alkenyl succinic anhydrides which are
prepared from maleic anhydride and internal olefins i.e., olefins
which are not terminally unsaturated and therefore do not contain
the
##STR00002##
moiety. These internal olefins can be introduced into the reaction
mixture as such, or they can be produced in situ by exposing
alpha-olefins to isomerization catalysts at high temperatures. A
process for producing such materials is described in U.S.
3,382,172. The isomerized alkenyl substituted succinic anhydrides
have the structure shown as structure (II), where structure (II) is
represented by:
##STR00003##
where x and y are each independently integers, the sum of which is
from 1 to 30.
[0092] The preferred succinic anhydrides are produced from
isomerization of linear alpha-olefins with an acidic catalyst
followed by reaction with maleic anhydride. The preferred
alpha-olefins are 1-octene, 1-decene, 1-dodecene, 1-tetradecene,
1-hexadecene, 1-octadecene, 1-eicosane, or mixtures of these
materials. The products described can also be produced from
internal olefins of the same carbon numbers, 8 to 20. The preferred
materials for this invention are those made from 1-tetradecene
(x+y=9), 1-hexadecene (x+y=11) and 1-octadecene (x+y=13), or
mixtures thereof.
[0093] The isomerized alkenyl succinic anhydrides are then further
reacted with polyamines of structure (III), where structure (III)
is represented by:
##STR00004##
where z is an integer from 1 to 10, preferably from 1 to 3.
[0094] These are common polyethylene amines. When z=1 the material
is diethylene triamine, when z=2 the material is triethylene
tetramine, when z=3 the material is tetraethylene pentamine, for
products where z>3 the products are commonly referred to as
`polyamine` or PAM. The preferred products of this invention employ
diethylene triamine, triethylene tetramine, tetraethylene pentamine
or mixtures thereof.
[0095] The isomerized alkenyl succinic anhydrides (II) are
typically reacted with the amines in a 2:1 molar ratio so that both
primary amines are converted to succinimides. Sometimes a slight
excess of isomerized alkenyl succinic anhydride (II) is used to
insure that all primary amines have reacted. The products of the
reaction are shown as structure (I).
[0096] The di-succinimides of structure (I) may be further
post-treated by any number of techniques known in the art. These
techniques would include, but not be limited to: boration,
maleation, acid treating with inorganic acids such as phosphoric,
phosphorous, and sulfuric. Descriptions of these processes can be
found in, for example, U.S. Pat. Nos. 3,254,025; 3,502,677;
4,686,054; and 4,857,214.
[0097] Other useful derivatives of these preferred friction
modifiers are where the isomerized alkenyl groups of structures (I)
and (II) have been hydrogenated to form their saturated alkyl
analogs. These saturated versions of structures (I) and (II) may
likewise be post-treated as previously described.
[0098] While any effective amount of the compounds of structure (I)
and its derivatives may be used in additive (iv) of this invention,
typically these effective amounts will range from 0.5 to 10,
preferably from 2 to 7, most preferably from 3 to 6 weight percent
of the finished fluid.
[0099] The various chosen components of additive (iv) of this
invention may be combined in the form of a concentrate. Typically
the active ingredient (a.i.) level of the concentrate will range
from 20 to 90%, preferably from 25 to 80%, most preferably from 35
to 75 weight percent of the concentrate. The balance of the
concentrate is a diluent typically comprised of a diluent or
solvent.
[0100] The process of the present invention provides for the
manufacture of a transmission fluid composition, the composition
consisting of: [0101] (v) a lubricating oil, or blend of
lubricating oils; [0102] (vi) a viscosity modifier additive or
blend of viscosity modifier additives; [0103] (vii) a
polyalphaolefin compound or compounds, each made by the
metallocene-catalysed polymerisation of an alphaolefin feedstock;
and [0104] (viii) one or more detergent additives, at least one of
which comprises one or more alkaline earth metal detergent
compounds wherein at least one alkaline earth metal detergent
compound is an alkaline earth metal salicylate or sulphonate
compound; the process comprising the following steps: a) obtaining
(by manufacture or otherwise) a lubricating oil or blend of
lubricating oils containing no polyalphaolefin compound(s) made by
the metallocene-catalysed polymerisation of an alphaolefin
feedstock; and b) mixing with this lubricating oil or blend of
lubricating oils the following: [0105] (b)(1) the viscosity
modifier additive or blend of viscosity modifier additives (ii),
[0106] (b)(2) the polyalphaolefin compound(s) (iii) in a total
amount not exceeding 4 percent by weight of the transmission fluid
composition, and [0107] (b)(3) one or more detergent additives
(iv); to provide the transmission fluid composition.
[0108] Preferably, the resulting composition is an automotive
transmission fluid, and more preferably the additions in step b)
improve the efficiency of power transmission provided by the
composition when in use as an automotive transmission fluid, as
demonstrated by an increase in the fuel efficiency of the vehicle
during operation.
[0109] In the process, the polyalphaolefin compound(s) (iii) are
preferably mixed with one or more of the detergent additives (iv)
to form a single additive concentrate prior to addition to the
lubricating oil or blend of oils.
[0110] Preferably, in the process, the total amount of the
polyalphaolefin compound or compounds (iii) mixed with the
lubricating oil or blend of lubricating oils is in the range of 2
to 3 percent by weight of the transmission fluid composition.
[0111] Also preferably in the process, each alkaline earth metal
detergent compound mixed with the transmission fluid composition is
a neutral or overbased calcium salicylate compound. More
preferably, when each alkaline earth metal detergent compound mixed
with the transmission fluid composition is a neutral or overbased
calcium salicylate compound, the total amount of calcium salicylate
compound(s) mixed with the lubricating oil or blend of lubricating
is such as to provide the transmission fluid composition with a
calcium content of between 50 and 250 parts per million by weight,
per weight of the transmission fluid composition.
[0112] The invention further provides a method of improving the
energy efficiency of a transmission, comprising the use therein of
the transmission fluid composition defined in the first aspect, or
of the transmission fluid composition obtained by the process of
the second aspect.
[0113] Preferably, in this method, the transmission is a
transmission for an automotive vehicle, and the improvement in
energy efficiency is an increase in fuel economy of the vehicle
during operation.
[0114] The invention further provides an additive concentrate for a
transmission fluid, the concentrate consisting of a suitable
carrier liquid, (ii) a viscosity modifier or blend of viscosity
modifiers, and (iii) a polyalphaolefin compound or mixture of
polyalphaolefin compounds made by the metallocene-catalysed
polymerisation of an alphaolefin feedstock, and (iv) one or more
detergent additives, at least one of which comprises one or more
alkaline earth metal detergent compounds wherein at least one
alkaline earth metal detergent compound is an alkaline earth metal
salicylate or sulphonate compound; wherein the total amount of
polyalphaolefin compound(s) (iii) present in the concentrate is
such that, after addition of the concentrate at its specified treat
rate to the transmission fluid, said compounds (iii) constitute no
more than 4 percent by weight of the resulting transmission fluid
composition.
[0115] Preferably, in the additive concentrate, the total amount of
the polyalphaolefin compound or compounds (iii) in the composition
is in the range of 2 to 3 percent by weight of the composition.
[0116] Also preferably, in the additive concentrate each alkaline
earth metal detergent compound present in the concentrate is a
neutral or overbased calcium salicylate compound.
[0117] In the process, method and concentrate aspects of the
invention, the other preferments for each of the components (i),
(ii), (iii) and (iv) are as stated previously in relation to the
composition of the first aspect.
EXAMPLES
[0118] The following examples are given as specific illustrations
of the claimed invention. It should be understood, however, that
the invention is not limited to the specific details set forth in
the examples. All parts and percentages are by weight per weight of
the resulting transmission fluid composition, unless otherwise
specified.
Worked Example 1
Benefit of Additive Treat Levels of the Polyalphaolefin (iii)
[0119] The essentiality of the defined metallocene-derived
polyalphaolefin in the invention is demonstrated by back-to-back
tests conducted on transmission fluids with and without this
material present.
[0120] Four automotive transmission fluids were prepared according
to the process aspect of the invention, by blending together the
components shown in Table 1. In each case the components (i), (ii),
(iv) were the same, and the fluids differ chemically only in the
presence or absence of the polyalphaolefin (iii).
TABLE-US-00002 TABLE 1 Component Composition Composition (% by
weight, per weight of 1C 2C finished composition) Composition 1
(comparative) Composition 2 (comparative) Base lubricating oil 83.7
86.3 83.3 85.1 Viscosity modifier 3.0 3.0 2.0 4.2 Pour point
depressant 0.3 0.2 0.2 0.2 mPolyalphaolefin 2.5 -- 4.0 -- Detergent
additive: Overbased calcium 0.08 0.08 0.08 0.08 salicylate
Overbased calcium -- -- -- -- sulphonate Other components 10.42
10.42 10.42 10.42 KV 40.degree. C. 19.84 17.73 19.23 18.69 KV
100.degree. C. 4.77 4.37 4.63 4.69
[0121] In these compositions, the base lubricating oil, viscosity
modifier, pour point depressant and detergent additive were the
same in each case, and the blends differed only in the relative
proportions of these constituents and, in the case of Compositions
1C and 2C, in the absence of the mPAO.
[0122] The mPolyalphaolefin was SpectraSyn Elite.TM. 150, an item
of commerce from Exxonmobil Chemical Company. The detergent
additive contained overbased calcium salicylate and additionally
contained other components being dispersant, anti-wear, and other
minor active components typical of a detergent additive package,
combined with a small amount of base oil and diluent. These other
components of the detergent additive were the same in each case.
The viscosity modifier was VISCOPLEX.RTM. 12-199, available as an
item of commerce from Evonik Rohmax US-A, Inc. and falling within
the class (ii)(c) described earlier in relation to suitable
viscosity modifiers. The pour point depressant was a typical
commercially available material and the same in each case.
[0123] The performance of these compositions was tested in the
following two experiments.
[0124] A bench-test experiment called the "FE-8" test measures the
torque required to rotate a radial thrust roller bearing assembly
lubricated by the transmission fluid in question. The efficiency of
the formulations was tested by measuring torque to rotate the
cylindrical roller bearings at various conditions using an FE-8
radial thrust roller bearing tester. The bearings used are 15
roller FAG/INA 81212 bearings. The bearings were installed in the
test rig and then pre-loaded to 60 kN. The bearings are run-in for
20 hours at 500 rpm at 100.degree. C. prior to taking any
measurement.
[0125] For each test fluid, the test head is heated until the
bearing temperature reaches 40.degree. C. While maintaining this
temperature, bearings are rotated at 10 rpm for 10 mins then at 100
rpm and 500 rpm for 5 mins each. The reported torque at each
condition is calculated by averaging the torque reading during the
last 1 minute of the condition. Temperature is then increased to
80.degree. C. and then finally to 120.degree. C. and torque is
measured with the same procedure at the three speeds. After this,
the rig is cooled down to room temperature and the whole process is
repeated. Final test results are the average of two repeats at each
temperature and speed.
[0126] The FE-8 test thus compares the energy requirements needed
to achieve defined bearing rotation with different fluids.
Achieving the defined rotations with lower applied torque indicates
greater energy efficiency within the mechanical system.
[0127] A vehicle test experiment was conducted according to the
standard US Federal Test Procedure 75 ("FTP 75"). A
commercially-available SUV with six speed automatic transmission
was repeatedly run on a vehicle dynamometer according to the
operating cycle specified in FTP 75, and in each case the
improvement in fuel economy observed for the transmission fluid
employed in the test is reported (as % improvement) over a
reference fluid.
[0128] The FTP 75 provides a direct measure of fuel economy
observed in vehicle operation. A positive percentage indicates
greater fuel efficiency compared to reference.
[0129] In an FE-8 test, fluid compositions 1, 1C and 2C were
compared for energy efficiency. The results are shown in Table 2
below.
TABLE-US-00003 TABLE 2 Composition FE-8 Torque, NM Composition 1
Composition 1C 2C 40.degree. C., 100 rpm 26.3 27.0 27.1 40.degree.
C., 500 rpm 21.2 21.7 21.9 80.degree. C., 100 rpm 30.2 31.2 30.9
80.degree. C., 500 rpm 23.3 24.4 24.1 120.degree. C., 100 rpm 30.1
30.6 30.9 120.degree. C., 500 rpm 23.1 23.9 24.2
[0130] As can be seen, Composition 1 consistently required lower
applied torque to achieve rotations of 100 and 500 rpm in the FE-8
test, indicating improved energy efficiency for composition 1 (with
polyalphaolefin (iii) at 2.5%) as compared to compositions 1C (and
2C) (no polyalphaolefin (iii)). In this screener test, the presence
of polyalphaolefin (iii) shows an overall benefit for energy
efficiency.
[0131] In particular, the compared samples were blended to have
similar kinematic viscosity behaviour, thus eliminating the
possibility of viscosity differences accounting for the differences
in measured torque. Comparing the results for compositions 1C and
2C further demonstrates that the small residual differences in the
KV values of these samples do not account for the differences in
torque seen between composition 1 and composition 1C, which must
therefore be attributable to the effect of polyalphaolefin (iii).
For example, composition 2C had a KV 100 of 4.69, almost identical
to that of composition 1 (4.77), yet at 120.degree. C. the torque
results for composition 2C are even higher than those for
composition 1 C, indicating that the better results obtained for
composition 1 cannot be explained by reference to viscosity
behaviour per se.
[0132] In FTP 75 vehicle tests, composition 1 (polyalphaolefin
(iii) at 2.5%) was compared to the test reference fluid (contains
no polyalphaolefin (iii)) and to composition 2 ((polyalphaolefin
(iii) at the higher treat rate of 4%). The percentage improvement
in fuel economy over the whole test was 0.86% for composition 1,
compared to only 0.42% for composition 2. Thus the fuel efficiency
benefit of polyalphaolefin (iii) in the composition showed an
optimum at the treat rate of 2.5%, and at a higher treat rate of 4%
the fuel efficiency benefit had dropped off considerably,
confirming the benefit seen is one attributable to additive-level
proportions of polyalphaolefin (iii).
Worked Example 2
Benefit of the Specific Detergents (iv)
[0133] The fuel efficiency effect of the defined specific
detergents (iv) in the invention is demonstrated by further
comparative tests.
[0134] Three further automotive transmission fluids were prepared
according to the process aspect of the invention, by blending
together the components shown in Table 3. These fluids were tested
alongside composition 1 from Table 1 in the FTP 75 vehicle test to
compare the detergent effects on fuel efficiency in the
formulations of the invention.
TABLE-US-00004 TABLE 3 Component (% by weight, per weight of
finished composition) Composition 3 Composition 4 Composition 5
Base lubricating oil 83.8 83.8 83.8 Viscosity modifier 3.0 3.0 3.0
Pour point depressant 0.2 0.2 0.2 mPolyalphaolefin 2.5 2.5 2.5
Detergent additive: Overbased calcium 0.11 0.16 -- salicylate
Overbased calcium -- -- 0.09 sulphonate Other components 10.39
10.34 10.41 KV 40.degree. C. 19.92 19.99 19.67 KV 100.degree. C.
4.76 4.77 4.72 Note: in these formulations, the amount of diluent
in the detergent additive was adjusted to compensate for the
variation in salicylate or sulphonate level, this change being
reflected in the slight variation in the amount of `other
components` recorded in the table.
[0135] The vehicle test experiment was again conducted according to
the standard US Federal Test Procedure 75 ("FTP 75"), using the
same commercially-available SUV with six speed automatic
transmission on a vehicle dynamometer. In each case the improvement
in fuel economy observed for the transmission fluid employed in the
test is again reported (as % improvement) over the reference
fluid.
[0136] Composition 1 (from Example 1 above, calcium salicylate
present to the treat rate of 100 ppm calcium) showed a fuel economy
improvement over the total FTP 75 test of 0.86%. Composition 3
(higher calcium salicylate treat rate, 140 ppm calcium) showed a
significantly greater improvement of 1.47%, whilst a further
increase in calcium salicylate to a treat rate of 200 ppm calcium
(Composition 4) caused the fuel economy result to drop back to
0.49%. Thus an optimum effect is seen in the region of 140 ppm
calcium, with response reducing either side of this treat rate.
[0137] A test on Composition 5 (equivalent to Composition 1, but
with calcium salicylate replaced with calcium sulphonate to the
same calcium treat of 100 ppm) showed a lower FTP 75 fuel economy
benefit of 0.42%, as compared to 0.86% for Composition 1. Thus,
both sulphonate and salicylate examples achieved valuable fuel
economy benefits over the reference fluid, but the salicylate
example showed greater benefits at equivalent treat rate,
confirming the performance advantage for salicylate over
sulphonate.
Worked Example 3
Comparison with Existing Base-Stock Approach in the Art
[0138] The ability of the present invention to achieve fuel
efficiency improvements through additive-level quantities of the
specific polyalphaolefin (iii), detergent additive (iv) and
viscosity modifier (ii) was compared to the prior art PAO basestock
approach described in US-A-2010/0035778 referred to above.
[0139] US-A-2010/0035778 (to GM Global Technology Operations Inc.)
exemplifies a composition comprising 9.4% (by weight, per total
weight of fluid) of a first polyalphaolefin (PAO 2cSt) and 68.0% of
a second polyalphaolefin (PAO 6cSt), together with proprietary
additives comprising the additive package Hitec.RTM. 3491 plus
viscosity index improver and ester to a total of 22.6% by weight of
the composition. The reference claims a fuel economy benefit for
such compositions.
[0140] The performance of Composition 1 of the present invention
was compared to a commercially-obtained GM automatic transmission
fluid (GM ATF 212-B), having a reported PAO composition the same as
that of the example from US-A-2010/0035778, and likewise a total
additive content of 22.6% (Hitec 3941A). This composition is
therefore regarded as illustrative of the invention exemplified in
US-A-2010/0035778.
[0141] The performance of Composition 1 in the FTP 75 test has been
noted as 0.86% fuel economy improvement over the whole test. In
contrast, the GM ATF 212-B sample gave a result in the same test of
0.12% improvement in fuel economy over the same reference fluid.
Thus, Composition 1 showed substantially better fuel economy than
the invention described in US-A-2010/0035778.
[0142] US-A-2010/0035778 teaches a solution for fuel economy that
requires the blend of two PAOs of differing viscosities as the
basestock for the transmission fluid. As shown by the above
results, a greater improvement in fuel economy is surprisingly
obtained from the composition of the present invention, through the
use of only a small (additive) quantity of the specific mPAO (iii)
in combination with the other essential components.
* * * * *
References