Note: Descriptions are shown in the official language in which they were submitted.
CA 02859413 2014-08-15
TRANSMISSION FLUID COMPOSITIONS FOR IMPROVED ENERGY EFFICIENCY
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.
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.
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 road 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 roads
wheels result in reduced energy efficiency for the vehicle, as demonstrated
for example by
poorer fuel efficiency.
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 transmission. At the
same time,
1
CA 02859413 2014-08-15
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.
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.
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.
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.
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.
2
CA 02859413 2014-08-15
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.
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 2cSt 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 4.0cSt at
100 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.
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
3
CA 02859413 2014-08-15
fluid composition with a calcium content of between 50 and 250 parts per
million by weight, per
weight of the transmission fluid composition.
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.
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.
In a first aspect therefore, the present invention provides 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 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.
4
CA 02859413 2014-08-15
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.
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.
In a second aspect, the present invention provides 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 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;
5
CA 02859413 2014-08-15
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 additives (iv);
to provide the transmission fluid composition.
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.
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.
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
6
CA 02859413 2014-08-15
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. 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.
The present invention is hereinafter described in more detail.
The transmission fluid composition consists of four essential elements (i),
(ii), (iii) and
(iv). The components are:
(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 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.
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
7
CA 02859413 2014-08-15
lubricating oil or blend of oils. Alternatively, the polyalphaolefin
compound(s) (iii) may be
mixed with one or more of the detergent additive (iv) to form a single
additive concentrate prior
to addition to the lubricating oil or blend of oils.
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.
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 mm2/s (cSt) at 100 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 mm2/s (cSt) at 100 C.
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.
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.
8
CA 02859413 2014-08-15
Typically the mineral oils will have kinematic viscosities of from 2.0 mm2/s
(cSt) to 10.0
mm2/s (cSt) at 100 C. The preferred mineral oils have kinematic viscosities of
from 2 to 8
mm2/s (cSt), and most preferred are those mineral oils with viscosities of 3
to 6 mm2/s (cSt) at
100 C.
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.
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.
The polyalphaolefins typically have viscosities in the range of 2 to 20 cSt at
100 C,
preferably 4 to 8 cSt at 100 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-l-hexenes, poly-1 -octenes and poly-1 -
decene. Included are
homopolymers, interpolymers and mixtures.
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.
9
CA 02859413 2014-08-15
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 C3-C8 fatty acid esters, and C12 oxo acid diester of tetraethylene
glycol).
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 C4 to
C12 alcohols.
Esters useful as synthetic lubricating oils also include those made from C5 to
C12
monocarboxylic acids and polyols and polyol ethers such as neopentyl glycol,
trimethylolpropane pentaerythritol, dipentaerythritol, tripentaerythritol, and
the like.
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
CA 02859413 2014-08-15
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.
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.
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.
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.
11
CA 02859413 2014-08-15
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.
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 a,13-unsaturated ester monomers such as alkyl acrylates and alkyl
methacrylates, or
from one or more olefins and one or more a,13-unsaturated ester monomers such
as alkyl
acrylates and alkyl methacrylates.
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 :
(ii)(a) random or block poly-alkylacrylates or poly-alkylmethacrylates, or
copolymers
thereof;
(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
(ii)(c) comb polymers prepared by the copolymerisation of one or more
alkylacrylate or
alkylmethacrylate monomers with one or more olefin or polyolefin monomers.
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 12-075 supplied by Evonik Rohmax USA, Inc.
12
CA 02859413 2014-08-15
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.
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.
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.
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.
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
13
CA 02859413 2014-08-15
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 I, 1511 and numbered as 2008-0102462,
and in US-A-
2010/0190671 which describes their nature and preparation.
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
"Spectrosyn EliteTM 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-mpao.aspx?ln=productsservices under the
description of
"Advanced synthetic basestock". The performance advantages of Spectrosyn
EliteTM 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.
14
CA 02859413 2014-08-15
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 C6 to
C18 alphaolefins.
Preferred polyalphaolefins (iii) are those made from a feedstock mixture of C6
and C18 linear
alphaolefins or a mixture of C6 and C12 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 Spectrosyn Elite' m 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 C of 156 mm2/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 C as measured by ASTM D5950/D97.
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.
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").
CA 02859413 2014-08-15
Such fluids are formulated with a detergent additive (iv) to meet the various
performance
requirements and/or specifications of a given application, especially
automotive application.
Within this specification, the term "detergent 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.
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. Patent 4,105,571.
Representative amounts of typical components of additive (iv) in an automotive
transmission fluid are summarized as follows:
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
16
CA 02859413 2014-08-15
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.
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.
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.
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 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
17
CA 02859413 2014-08-15
metal neutralizing agent and at least one alcohol promoter, and carbonating
the mixture at an
elevated temperature such as 60 to 200 C.
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.
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.
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.
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; 4,965,004.
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
18
CA 02859413 2014-08-15
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.
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.
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.
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.
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
19
CA 02859413 2014-08-15
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.
(see, e.g., U.S. Pat.
Nos. 3,254,025, 3,502,677 and 4,857,214).
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 H3P03 and
H3B03 (see e.g.,
U. S. 4,857,214); zinc (di-2-ethylhexyldithiophosphate).
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. 5,314,633, incorporated herein by
reference.
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.
CA 02859413 2014-08-15
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:
CH3 CH3
1 1
(CH2)x (CH2)x
1 1
0
HC CH (I)
1
CH N -(CH2CH2N)-- CH2CH2N
CH
11 H z 11
CH3 - (CH2)y -CH
0 HC- (CH2)y -CH3
where x and y are independent integers whose sum is from 1 to 30, and z is an
integer from 1 to
10.
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
/ H2 C=C )-
1
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:
21
=
CA 02859413 2014-08-15
CH3
(CH2)x
o
HC
H//H (11), where x and y are independent integer;
whose sum is from 1 to 30.
C 0
(CH2)y
CH3
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.
The isomerized alkenyl succinic anhydrides are then further reacted with
polyamines of
structure (III), where structure (III) is represented by:
H2N CH2CH2N ___________________________ CH2CH2NH2 (111),
H z
where z is an integer from 1 to 10, preferably from 1 to 3.
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.
22
CA 02859413 2014-08-15
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).
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. 3,254,025;
U.S. 3,502,677;
U.S. 4,686,054; and U.S. 4,857,214.
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.
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.
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.
The process of the present invention provides for the manufacture of a
transmission fluid
composition, the composition consisting of:
(v) a lubricating oil, or blend of lubricating oils;
(vi) a viscosity modifier additive or blend of viscosity modifier
additives;
23
CA 02859413 2014-08-15
(vii) a polyalphaolefin compound or compounds, each made by the metallocene-
catalysed
polymerisation of an alphaolefin feedstock; and
(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:
(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 additives (iv);
to provide the transmission fluid composition.
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.
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.
24
CA 02859413 2014-08-15
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.
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.
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.
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.
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.
CA 02859413 2014-08-15
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.
Also preferably, in the additive concentrate each alkaline earth metal
detergent compound
present in the concentrate is a neutral or oyerbased calcium salicylate
compound.
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:
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)
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.
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).
26
CA 02859413 2014-08-15
Table 1
Component Composition 1 Composition Composition 2
Composition
(% by weight, per weight of 1C 2C
finished composition) (comparative)
(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 C 19.84 17.73 19.23 18.69
KV 100 C 4.77 4.37 4.63 4.69
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.
The mPolyalphaolefin was Spectrosyn EliteTM 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 12-199, available as an item of commerce
from Evonik
Rohmax USA, 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.
The performance of these compositions were tested in the following two
experiments.
27
CA 02859413 2014-08-15
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 C
priot to taking any
measurement.
For each test fluid, the test head is heated until the bearing temperature
reaches
40 C. While maintaining this temperature, bearings are rotated at 10 rpm for
10mins then at
10Orpm and 500rpm 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 C and then finally to 120 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.
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.
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.
The FTP 75 provides a direct measure of fuel economy observed in vehicle
operation. A
positive percentage indicates greater fuel efficiency compared to reference.
28
CA 02859413 2014-08-15
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 2
FE-8 Torque, NM Composition 1 Composition 1C
Composition 2C
40 C, 10Orpm 26.3 27.0
27.1
40 C, 50Orpm 21.2 21.7
21.9
80 C, 10Orpm 30.2 31.2
30.9
80 C, 500rpm 23.3 24.4
24.1
120 C, 10Orpm 30.1 30.6
30.9
120 C, 50Orpm 23.1 23.9
24.2
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.
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 C the
torque results for
composition 2C are even higher than those for composition 1C, indicating that
the better results
obtained for composition 1 cannot be explained by reference to viscosity
behaviourper se.
29
CA 02859413 2014-08-15
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 A). 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 A, 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)
The fuel efficiency effect of the defined specific detergents (iv) in the
invention is
demonstrated by further comparative tests.
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 3
Component Composition 3 Composition 4 Composition
5
(% by weight, per weight of
finished composition)
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 C 19.92 19.99 19.67
KV 100 C 4.76 4.77 4.72
30
CA 02859413 2014-08-15
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.
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 reference fluid.
Composition 1 (from Example 1 above, calcium salicylate present to the treat
rate of
100ppm calcium) showed a fuel economy improvement over the total FTP 75 test
of 0.86%.
Composition 3 (higher calcium salicylate treat rate, 140ppm calcium) showed a
significantly
greater improvement of 1.47%, whilst a further increase in calcium salicylate
to a treat rate of
200ppm calcium (Composition 4) caused the fuel economy result to drop back to
0.49%. Thus an
optimum effect is seen in the region of 140ppm calcium, with response reducing
either side of
this treat rate.
A test on Composition 5 (equivalent to Composition 1, but with calcium
salicylate
replaced with calcium sulphonate to the same calcium treat of 100ppm) 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
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.
31
CA 02859413 2014-08-15
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 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.
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). The applicant therefore regards
this as illustrative
of the invention exemplified in US-A-2010/0035778.
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
fuel. Thus,
Composition 1 showed substantially better fuel economy than the invention
described in US-A-
2010/0035778.
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.
32
