Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02606374 2007-10-09
PF2006L003 - 1 -
LUBRICATING OIL COMPOSITIONS
FIELD OF THE INVENTION
The invention is directed to lubricating oil compositions formulated with
blended viscosity index improver compositions. More specifically, the present
invention is directed to lubricating oil compositions comprising a major
amount of oil
of lubricating viscosity and a viscosity index improver composition containing
at least
two polymeric viscosity index improvers, which lubricating oil compositions
provide
simultaneously improved viscometric properties, particularly at low
temperatures, and
shear stability performance.
BACKGROUND OF THE INVENTION
Lubricating oil compositions for use in crankcase engine oils comprise a major
amount of base oil and minor amounts of additives that improve the performance
and
increase the useful life of the lubricant. Crankcase lubricating oil
compositions
conventionally contain polymeric components that are used to improve the
viscometric performance of the engine oil, i.e., to provide multigrade oils
such as
SAE 5W-30, 10W-30, 1 OW-40 and 15W-40. These viscosity performance enhancing
material, commonly referred to as viscosity index (VI) improvers, can increase
the
viscosity of a lubricating oil formulation at higher temperatures (typically
above
100 C) without increasing excessively the high shear rate viscosity at lower
temperatures (typically -10 to -35 C). These oil-soluble polymers are
generally of
higher molecular weight (>100,000 Mõ) compared to the base oil and other
components. Well known classes of polymers suitable for use as viscosity index
improvers for lubricating oil compositions include ethylene a-olefin
copolymers,
polymethacrylates, diblock copolymers having a vinyl aromatic segment and a
hydrogenated polydiene segrnent, and star copolymers and hydrogenated isoprene
linear and star polymers.
Viscosity index improvers for lubricating oil compositions advantageously
increase the viscosity of the lubricating oil composition at higher
temperatures when
used in relatively small amounts (have a high thickening efficiency (TE)),
provide
reduced lubricating oil resistance to cold engine starting (as measured by
"CCS"
performance) and be resistant to mechanical degradation and reduction in
molecular
CA 02606374 2007-10-09
= = , r
PF2006L003 - 2 -
weight in use (have a low shear stability index (SSI)). Further, as viscosity
index
improving polymers are often provided to lubricant blenders as a concentrate
in which
the viscosity index improving polymer is diluted in oil, which concentrate is
then
blended into a greater volume of oil to provide the desired lubricant product,
it is
fiirthher preferred that viscosity index improving polymers can be blended
into
concentrates in relatively large amounts, without causing the concentrate to
have an
excessively high kinematic viscosity. Some polymers are excellent in some of
the
above properties, but are deficient in one or more of the others.
Amorphous olefin copolymers (OCP) are one class of VI improver.
1o Conventionally, OCP are copolymers of ethylene and propylene monomers (EPM)
and optionally a diene monomer (EPDM). Amorphous OCP has very low, or no
crystallinity and are relatively insensitive to base stock and pour point
depressant
selection. However, amorphous OCP provide relatively poor thickening
efficiency
(TE) in oil for a given shear stability index (30-cycle SSI).
Semi-crystalline OCP show improved TE in oil for a given SSI, however, the
crystalline nature of such copolymers causes both intermolecular and
intramolecular
interactions, which leads to network formations. Formation of such networks
causes
difficulties in handling of copolymer concentrates, even at room temperature,
and
interactions between such copolymers and base stocks can lead to poor low
temperature viscometric properties, such as high MRV viscosities and scanning
Brookfield gelation index values.
Star polymers are a third class of VI improver. The arms of the star polymers
are derived from diene, and optionally, vinyl aromatic hydrocarbon monomer.
Star
polymers provide improved TE and SSI (30-cycle) relative to semi-crystalline
OCP.
However, when the number of cycles of the test used to measure SSI are
extended (a
90 cycle shear stability test (ASTM D7109) was approved in 2004), the
kinematic
viscosity (kvloo) of star polymer-containing solutions continue to decrease,
while the
kvioo of an OCP-containing solution approaches an asymptotic value (see Shear
Stability Index of Viscosity Modifiers - E ect o Polymer Architecture,
presented by
Huang et al. at the 8th Annual Fuels and Lubes Asian Conference and
Exhibition,
Singapore, 2002).
CA 02606374 2007-10-09
PF2006L003 - 3 -
It would be advantageous to be able provide lubricating oil compositions that
provide simultaneously the high overall thickening efficiency and concentrate-
handling properties of a star polymer, and the low temperature viscometric
performance and extended shear stability performance of an amorphous or semi-
crystalline OCP.
PCT Publication WO 96/17041, June 6, 1996, discloses certain blends of star-
branched styrene-isoprene polymers and ethylene a-olefin copolymers. The
publication describes the addition of an amount of the ethylene a-olefin
copolymer to
the star-branched styrene-isoprene polymer as being effective to improve the
1 o dimensional stability of the star branched polymer so that the star
branched polymer
can be formed as a stable, solid bale.
U.S. Patent No. 4,194,057, March 18, 1980, discloses viscosity index
improving compositions containing a combination of a certain class of
relatively low
molecular weight vinyl aromatic/conjugated diene diblock copolymers and
ethylene
a-olefin copolymer. The patent describes the specified class of vinyl
aromatic/conjugated diene diblock copolymer as being relatively insoluble in
oil and
that blending with ethylene a-olefin copolymer improves solubility and allows
for the
formation of polymer concentrates.
PCT Publication WO 2004/087849, October 14, 2004, discloses a viscosity
index improver composition containing a blend of a select class of high
ethylene
content ethylene a-olef n copolymer, and vinyl aromatic/diene diblock
copolymer, in
certain proportions, which are describes as providing good low temperature
performance and durability.
SUMMARY OF THE INVENTION
In accordance with a first aspect of the invention, there is provided a
lubricating oil composition comprising a major amount of oil of lubricating
viscosity,
and a viscosity index (VI) improver composition comprising a first polymer
that is an
amorphous or semi-crystalline ethylene a-olefin copolymer comprising no
greater
than 66 mass % of units derived from ethylene; and a second polymer comprising
a
star polymer, the arms of which are derived from diene, and optionally vinyl
aromatic
hydrocarbon monomer, wherein the star polymer has a Shear Stability Index
(SSI) of
from about 1% to about 35% (30 cycle).
CA 02606374 2007-10-09
PF2006L003 - 4 _
In accordance with a second aspect of the invention, there is provided a
lubricating oil composition of the first aspect in which the first polymer and
the
second polymer are present in a mass % ratio of from about 80:20 to about
20:80.
In accordance with a third aspect of the invention, there is provided a
lubricating oil composition as in the first or second aspect, further
comprising a
nitrogenous dispersant derived from a polyalkene having a number average
molecular
weight (Mõ) of greater than about 1500
In accordance with a fourth aspect of the invention, there is provided a
lubricating oil composition, as in the first, second or thirds aspects,
wherein the base
oil of the lubricating oil composition has a saturates content of at least
about 80%, and
said lubricating oil composition contains less than about 0.4 mass % of
sulfur, less
than about 0.12 mass % phosphorus and less than about 1.2 mass % of sulfated
ash.
In accordance with a fifth aspect of the invention, there is provided a VI
improver concentrate comprising diluent oil, a first polymer that is an
amorphous
ethylene a-olefin copolymer having a crystallinity of less than 1.0 %; and a
second
polymer comprising a star polymer, the arms of which are derived from diene,
and
optionally vinyl aromatic hydrocarbon monomer, wherein the star polymer has a
Shear Stability Index (SSI) of from about 1% to about 35% (30 cycle), wherein
the
total amount of polymer in the concentrate (including at least the first
polymer and the
second polymer) is at least 5 mass%, based on the total mass of the
concentrate.
Other and further objects, advantages and features of the present invention
will
be understood by reference to the following specification.
DETAILED DESCRIPTION OF THE INVENTION
Ethylene-a-olefin copolymers (OCP) useful in the practice of the invention
include amorphous OCP synthesized from ethylene monomer and at least one other
a-
olefin comonomer. The average mass % of the OCP derived from ethylene
(hereinafter "ethylene content") of OCP useful in the present invention can be
as low
as about 20 mass %, preferably no lower than about 25 mass %; more preferably
no
lower than about 30 mass %. The maximum ethylene content can be about 66
mass %. Preferably the ethylene content of the OCP is from about 25 to 55 mass
%,
more preferably from about 35 to 55 mass %.
CA 02606374 2007-10-09
f
PF2006L003 - 5 -
Ethylene content can be measured by ASTM-D3900 for ethylene-propylene
copolymers containing between 35 mass % and 85 mass % ethylene. Above 85
mass %, ASTM-D2238 can be used to obtain methyl group concentration, which is
related to percent ethylene in an unambiguous manner for ethylene-propylene
copolymers. When comonomers other than propylene are employed, no ASTM tests
covering a wide range of ethylene contents are available; however, proton and
carbon-13 nuclear magnetic resonance spectroscopy can be employed to determine
the composition of such polymers. These are absolute techniques requiring no
calibration when operated such that all nuclei of a given element contribute
equally to
the spectra. For ethylene content ranges not covered by the ASTM tests for
ethylene-
propylene copolymers, as well as for any ethylene-propylene copolymers, the
aforementioned nuclear magnetic resonance methods can also be used.
"Crystallinity" is defined as:
Crystallinity (%) = (Heat of Fusion of (co)polymer in J/g)/ 292 J/g x 100;
wherein heat of fusion is determined by DSC and 292 J/g is the heat of fusion
for
polyethylene (see SAE Paper No. 971696; "Evaluation of Polyolefin Elastomers
Produced by Constrained Geometry Chemistry as Viscosity Modifiers for Engine
Oil",
McGirk et al. (1997)).
As noted, the ethylene-a-olefin copolymers are comprised of ethylene and at
least one other a-olefin. The "other" a-olefins typically include those
containing 3 to
18 carbon atoms, e.g., propylene, butene-1, pentene-1, etc. Preferred are a-
olefins
having 3 to 6 carbon atoms, particularly for economic reasons. The most
preferred
OCP are those comprised of ethylene and propylene.
As is well known to those skilled in the art, copolymers of ethylene and
higher
alpha-olefins such as propylene can optionally include other polymerizable
monomers.
Typical of these other monomers are non-conjugated dienes such as the
following
non-limiting examples:
a. straight chain acyclic dienes such as: 1,4-hexadiene; 1,6-octadiene;
b. branched chain acyclic dienes such as: 5-methyl-1, 4-hexadiene; 3, 7-
dimethyl-1,6-octadiene; 3, 7-dimethyl-1,7-octadiene and the mixed isomers of
dihydro-mycene and dihydroocinene;
c. single ring alicyclic dienes such as: 1, 4-cyclohexadiene; 1,5-
cyclooctadiene;
and 1,5-cyclododecadiene; and
CA 02606374 2007-10-09
PF2006L003 - ( -
d. multi-ring alicyclic fused and bridged ring dienes such as:
tetrahydroindene;
methyltetrahydroindene; dicyclopentadiene; bicyclo-(2,2,1)-hepta-2, 5-diene;
alkenyl, alkylidene, cycloalkenyl and cycloalkylidene norbornenes such as 5-
methylene-2-norbornene (MNB), 5-ethylidene-2-norbornene (ENB), 5-propylene-
2-norbomene, 5-isopropylidene-2-norbomene, 5-(4-cyclopentenyl)-2-norbomene;
5-cyclohexylidene-2-norbornene.
Of the non-conjugated dienes typically used to prepare these copolymers,
dienes containing at least one of the double bonds in a strained ring are
preferred.
The most preferred diene is 5-ethylidene-2-norbornene (ENB). When present, the
amount of diene (on a weight basis) in the copolymer can be from greater than
0% to
about 20%; preferably from greater than 0% to about 15%; most preferably
greater
than 0% to about 10%. OCP VI improver useful in the practice of the present
invention is preferably ethylene-propylene copolymer containing less than 2 %
of
diene units
The molecular weight of OCP useful in accordance with the present invention
can vary over a wide range since ethylene copolymers having number-average
molecular weights (Mn) as low as about 2,000 can affect the viscosity
properties of an
oleaginous composition. The preferred minimum MA is about 10,000; the most
preferred minimum is about 20,000. The maximum M. can be as high as about
12,000,000; the preferred maximum is about 1,000,000; the most preferred
maximum
is about 750,000. An especially preferred range of number-average molecular
weight
for OCP useful in the present invention is from about 15,000 to about 500,000;
preferably from about 20,000 to about 250,000; more preferably from about
25,000 to
about 150,000. The term "number average molecular weight", as used herein,
refers
to the number average weight as measured by Gel Permeation Chromatography
("GPC") with a polystyrene standard.
Useful OCP include those prepared in bulk, suspension, solution or emulsion.
As is well known, polymerization of monomers to produce hydrocarbon polymers
may be accomplished using free-radical, cationic and anionic initiators or
polymerization catalysts, such as transition metal catalysts used for Ziegler-
Natta and
metallocene type (also referred to as "single-site") catalysts.
"Thickening Efficiency" ("TE") is representative of a polymers ability to
thicken oil per unit mass and is defined as:
CA 02606374 2007-10-09
PF2006L003 -'] -
TE = 2 ln ~orJ+polymer
c ln 2 kvo;r
wherein c is polymer concentration (grams of polymer/100 grams solution),
kvo,j + polYõ,e< is kinematic viscosity of the polymer in the reference oil,
and kv il is
kinematic viscosity of the reference oil.
"Shear Stability Index" ("SSI") measures the ability of polymers used as V.I.
improvers in crankcase lubricants to maintain thickening power during use and
is
indicative of the resistance of a polymer to degradation under service
conditions. The
higher the SSI, the less stable the polymer, i.e., the more susceptible it is
to
degradation. SSI is defined as the percentage of polymer-derived viscosity
loss and is
calculated as follows:
SSI =100 x kvh." - kva,er
kvhesn - kvo;r
wherein kvfi,,,h is the kinematic viscosity of the polymer-containing solution
before
degradation and kvaft, is the kinematic viscosity of the polymer-containing
solution
after degradation. SSI is conventionally determined using ASTM D6278-98 (known
as the Kurt-Orban (KO) or DIN bench test). The polymer under test is dissolved
in
suitable base oil (for example, solvent extracted 150 neutral) to a relative
viscosity of
9 to 15 centistokes at 100 C and the resulting fluid is pumped through the
testing
apparatus specified in the ASTM D6278-98 protocol for 30 cycles. As noted
above, a
90 cycle shear stability test (ASTM D7109) was approved in 2004.
"Viscosity Loss" measures the ability of the V.I polymer in a formulated
lubricant to maintain thickening power in use and is defined as:
Viscosity Loss (%) = kvfr.h - kvusrd/kvfrmsh X 100.
"Cold Cranking Simulator" ("CCS") is a measure of the cold-cranking
characteristics of crankcase lubricants and is conventionally determined using
a
technique described in ASTM D5293-92.
The OCP of the present invention preferably has an SSI (30 cycles) of from
about 15 to about 60 %, preferably from about 20 % to about 55%, more
preferably
from about 25% to about 50 %. The OCP of the present invention preferably has
a
TE of from about 1.5 to about 4.0, preferably from about 1.6 to about 3.3,
more
preferably from about 1.7 to about 3Ø
CA 02606374 2007-10-09
PF2006L003 - 8 -
In one preferred embodiment, the OCP VI improver of the present invention is
an amorphous ethylene-propylene copolymer or copolymer blend having an SSI (30
cycle) of about 20 to about 55 %. More preferably, such OCP VI improver is
either
produced via Ziegler-Natta catalysis and contains from about 40 mass % to
about 55
mass % of ethylene, or is produced via single site (metallocene) catalysis and
contains
from about 35 mass % to about 55 mass % of ethylene.
The star (or radial) polymers or copolymers useful in the practice of the
present invention have multiple arms derived from diene, and optionally vinyl
aromatic hydrocarbon monomer, and have a Shear Stability Index (SSI) of from
about
1% to about 35% (30 cycle). Dienes, or diolefins, contain two double bonds,
commonly located in conjugation in a 1,3 relationship. Olefins containing more
than
two double bonds, sometimes referred to as polyenes, are also considered
within the
definition of "diene" as used herein. Useful dienes include those containing
from 4 to
about 12 carbon atoms, such as 1,3-butadiene, isoprene, piperylene,
methylpentadiene,
phenylbutadiene, 3,4-dimethyl-1,3-hexadiene, 4,5-diethyl-1,3-octadiene, with
1,3-
butadiene and isoprene and mixtures thereof being preferred. Preferred
isoprene
monomers that may be used as the precursors of the copolymers of the present
invention can be incorporated into the polymer as either 1,4- or 3,4-
configuration
units, and mixtures thereof. Preferably, the majority of the isoprene is
incorporated
into the polymer as 1,4-units, such as greater than about 60 wt.%, more
preferably
greater than about 80 wt.%, such as about 80 to 100 wt.%, most preferably
greater
than about 90 wt.%., such as about 93 wt.% to 100 wt.%. Preferred butadiene
monomers that may be used as the precursors of the copolymers of the present
invention can be incorporated into the polymer as either as either 1,2- or 1,4-
configuration units. Preferably, at least about 70 wt. %, such as at least
about 75
wt. %, more preferably at least about 80 wt. %, such as at least about 85 wt.
%, most
preferably at least about 90, such as 95 to 100 wt. %, of the butadiene is
incorporated
into the polymer as 1,4- units.
Useful vinyl aromatic hydrocarbon monomers include those containing from 8
to about 16 carbon atoms such as aryl-substituted styrenes, alkoxy-substituted
styrenes, vinyl naphthalene, alkyl-substituted vinyl naphthalenes and the
like. Dienes,
or diolefins, contain two double bonds, commonly located in conjugation in a
1,3-
relationship. Olefins containing more than two double bonds, sometimes
referred to
CA 02606374 2007-10-09
PF2006L003 - 9 -
as polyenes, are also considered within the definition of "diene" as used
herein.
Useful dienes include those containing from 4 to about 12 carbon atoms, such
as 1,3-
butadiene, isoprene, piperylene, methylpentadiene, phenylbutadiene, 3,4-
dimethyl-
1,3-hexadiene, 4,5-diethyl-1,3-octadiene, with 1,3-butadiene and isoprene
being
preferred.
The arms of the star polymer may be a homopolymer of a diene, e.g.,
polyisoprene, a copolymer of two or more dienes; e.g., an isoprene-butadiene
copolymer; or a copolymer of a diene and another monomer, e.g., an isoprene-
styrene
copolymer.
The arms of the star polymer may also be a block copolymer such as one
represented by the following general formula:
Ai (B-A)y-BX
wherein:
A is a polymeric block derived predominantly vinyl aromatic hydrocarbon
monomer;
B is a polymeric block derived predominantly conjugated diene monomer;
x and z are, independently, a number equal to 0 or 1; and
y is a whole number ranging from 1 to about 15.
The arms of the star polymer may also be a tapered linear block copolymer
such as one represented by the following general formula:
A-A/B-B
wherein:
A is a polymeric block derived predominantly from vinyl aromatic hydrocarbon
monomer;
B is a polymeric block derived predominantly conjugated diolefin monomer; and
A/B is a tapered segment derived from both vinyl aromatic hydrocarbon monomer
and conjugated diolefin monomer.
As used herein in connection with polymer block composition,
"predominantly" means that the specified monomer or monomer type that is the
principle component in that polymer block is present in an amount of at least
85% by
weight of the block.
Preferably, the arms of the star polymer are formed via anionic polymerization
to form a living polymer. Anionic polymerization has been found to provide
CA 02606374 2007-10-09
PF2006L003 - 10 -
copolymers having a narrow molecular weight distribution (Mw/Mn), such as a
molecular weight distribution of less than about 1.2
As is well known, and disclosed, for example, in U.S. Patent No. 4,116,917,
living polymers may be prepared by anionic solution polymerization of a
mixture of
the conjugated diene monomers in the presence of an alkali metal or an alkali
metal
hydrocarbon, e.g., sodium naphthalene, as anionic initiator. The preferred
initiator is
lithium or a monolithium hydrocarbon. Suitable lithium hydrocarbons include
unsaturated compounds such as allyl lithium, methallyl lithium; aromatic
compounds
such as phenyllithium, the tolyllithiums, the xylyllithiums and the
naphthyllithiums,
and in particular, the alkyl lithiums such as methyllithium, ethyllithium,
propyllithium,
butyllithium, amyllithium, hexyllithium, 2-ethylhexyllithium and n-
hexadecyllithium.
Secondary-butyllithium is the preferred initiator. The initiator(s) may be
added to the
polymerization mixture in two or more stages, optionally together with
additional
monomer. The living polymers are olefinically unsaturated.
The solvents in which the living polymers are formed are inert liquid
solvents,
such as hydrocarbons e.g., aliphatic hydrocarbons such as pentane, hexane,
heptane,
octane, 2-ethylhexane, nonane, decane, cyclohexane, methylcyclohexane, or
aromatic
hydrocarbons e.g., benzene, toluene, ethylbenzene, the xylenes,
diethylbenzenes,
propylbenzenes. Cyclohexane is preferred. Mixtures of hydrocarbons e.g.,
lubricating oils, may also be used.
The temperature at which the polymerization is conducted may be varied
within a wide range, such as from about -50 C to about 150 C, preferably from
about
20 C to about 80 C. The reaction is suitably carried out in an inert
atmosphere, such
as nitrogen, and may optionally be carried out under pressure e.g., a pressure
of from
about 0.5 to about 10 bars.
The concentration of the initiator used to prepare the living polymer may also
vary within a wide range and is determined by the desired molecular weight of
the
living polymer.
To form the star polymer, the living polymers formed via the foregoing
process are reacted in an additional reaction step, with a polyalkenyl
coupling agent.
Polyalkenyl coupling agents capable of forming star polymers have been known
for a
number of years and are described, for example, in U.S. Patent No. 3,985,830.
Polyalkenyl coupling agents are conventionally compounds having at least two
non-
CA 02606374 2007-10-09
PF2006L003 - 11 -
conjugated alkenyl groups. Such groups are usually attached to the same or
different
electron-withdrawing moiety e.g. an aromatic nucleus. Such compounds have the
property that at least of the alkenyl groups are capable of independent
reaction with
different living polymers and in this respect are different from conventional
conjugated diene polymerizable monomers such as butadiene, isoprene, etc. Pure
or
technical grade polyalkenyl coupling agents may be used. Such compounds may be
aliphatic, aromatic or heterocyclic. Examples of aliphatic compounds include
the
polyvinyl and polyallyl acetylene, diacetylenes, phosphates and phosphates as
well as
dimethacrylates, e.g. ethylene dimethylacrylate. Examples of suitable
heterocyclic
compounds include divinyl pyridine and divinyl thiophene.
The preferred coupling agents are polyalkenyl aromatic compounds and most
preferred are the polyvinyl aromatic compounds. Examples of such compounds
include those aromatic compounds, e.g. benzene, toluene, xylene, anthracene,
naphthalene and durene, which are substituted with at least two alkenyl
groups,
preferably attached directly thereto. Specific examples include the polyvinyl
benzenes e.g. divinyl, trivinyl and tetravinyl benzenes; divinyl, trivinyl and
tetravinyl
ortho-, meta- and para-xylenes, divinyl naphthalene, divinyl ethyl benzene,
divinyl
biphenyl, diisobutenyl benzene, diisopropenyl benzene, and diisopropenyl
biphenyl.
The preferred aromatic compounds are those represented by the formula A-
(CH=CH2), wherein A is an optionally substituted aromatic nucleus and x is an
integer of at least 2. Divinyl benzene, in particular meta-divinyl benzene, is
the most
preferred aromatic compound. Pure or technical grade divinyl benzene
(containing
other monomers e.g. styrene and ethyl styrene) may be used. The coupling
agents
may be used in admixture with small amounts of added monomers which increase
the
size of the nucleus, e.g. styrene or alkyl styrene. In such a case, the
nucleus can be
described as a poly(dialkenyl coupling agent/monoalkenyl aromatic compound)
nucleus, e.g. a poly(divinylbenzene/monoalkenyl aromatic compound) nucleus.
The polyalkenyl coupling agent should be added to the living polymer after
the polymerization of the monomers is substantially complete, i.e. the agent
should be
added only after substantially all the monomer has been converted to the
living
polymers.
The amount of polyalkenyl coupling agent added may vary within a wide
range, but preferably, at least 0.5 mole of the coupling agent is used per
mole of
CA 02606374 2007-10-09
PF2006L003 - 12 -
unsaturated living polymer. Amounts of from about 1 to about 15 moles,
preferably
from about 1.5 to about 5 moles per mole of living polymer are preferred. The
amount, which can be added in two or more stages, is usually an amount
sufficient to
convert at least about 80 mass % to 85 mass % of the living polymer into star-
shaped
polymer.
The coupling reaction can be carried out in the same solvent as the living
polymerization reaction. The coupling reaction can be carried out at
temperatures
within a broad range, such as from 0 C to 150 C, preferably from about 20 C to
about
120 C. The reaction may be conducted in an inert atmosphere, e.g. nitrogen,
and
under pressure of from about 0.5 bar to about 10 bars.
The star polymers thus formed are characterized by a dense center or nucleus
of crosslinked poly(polyalkenyl coupling agent) and a number of arms of
substantially
linear unsaturated polymers extending outward from the nucleus. The number of
arms may vary considerably, but is typically between about 4 and 25.
The resulting star polymers can then be hydrogenated using any suitable
means. A hydrogenation catalyst may be used e.g. a copper or molybdenum
compound. Catalysts containing noble metals, or noble metal-containing
compounds,
can also be used. Preferred hydrogenation catalysts contain a non-noble metal
or a
non-noble metal-containing compound of Group VIII of the periodic Table i.e.,
iron,
cobalt, and particularly, nickel. Specific examples of preferred hydrogenation
catalysts include Raney nickel and nickel on kieselguhr. Particularly suitable
hydrogenation catalysts are those obtained by causing metal hydrocarbyl
compounds
to react with organic compounds of any one of the group VIII metals iron,
cobalt or
nickel, the latter compounds containing at least one organic compound that is
attached
to the metal atom via an oxygen atom as described, for example, in U.K. Patent
No.
1,030,306. Preference is given to hydrogenation catalysts obtained by causing
an
aluminum trialkyl (e.g. aluminum triethyl (Al(Et3)) or aluminum triisobutyl)
to react
with a nickel salt of an organic acid (e.g. nickel diisopropyl salicylate,
nickel
naphthenate, nickel 2-ethyl hexanoate, nickel di-tert-butyl benzoate, nickel
salts of
saturated monocarboxylic acids obtained by reaction of olefins having from 4
to 20
carbon atoms in the molecule with carbon monoxide and water in the presence of
acid
catalysts) or with nickel enolates or phenolates (e.g., nickel
acetonylacetonate, the
nickel salt of butylacetophenone). Suitable hydrogenation catalysts will be
well
CA 02606374 2007-10-09
PF2006L003 - 13 -
known to those skilled in the art and the foregoing list is by no means
intended to be
exhaustive.
The hydrogenation of the star polymer is suitably conducted in solution, in a
solvent which is inert during the hydrogenation reaction. Saturated
hydrocarbons and
mixtures of saturated hydrocarbons are suitable. Advantageously, the
hydrogenation
solvent is the same as the solvent in which polymerization is conducted.
Suitably, at
least 50%, preferably at least 70%, more preferably at least 90%, most
preferably at
least 95% of the original olefinic unsaturation is hydrogenated.
The hydrogenated star polymer may then be recovered in solid form from the
solvent in which it is hydrogenated by any convenient means, such as by
evaporating
the solvent. Alternatively, oil e.g. lubricating oil, may be added to the
solution, and
the solvent stripped off from the mixture so formed to provide a concentrate.
Suitable
concentrates contain from about 3 mass % to about 25 mass %, preferably from
about
5 mass % to about 15 mass % of the hydrogenated star polymer VI improver.
The star polymers useful in the practice of the present invention can have a
number average molecular weight of from about 10,000 to 700,000, preferably
from
about 30,000 to 500,000. The term "number average molecular weight", as used
herein, refers to the number average weight as measured by Gel Permeation
Chromatography ("GPC") with a polystyrene standard, subsequent to
hydrogenation.
It is important to note that, when determining the number average molecular
weight of
a star polymer using this method, the calculated number average molecular
weight
will be less than the actual molecular weight due to the three dimensional
structure of
the star polymer.
In one preferred embodiment, the star polymer of the present invention is
derived from about 75 % to about 90 % isoprene and about 10 % to about
butadiene,
and greater than 80 % of the butadiene units are incorporated 1,4-addition
product. In
another preferred embodiment, the star polymer of the present invention
comprises
amorphous butadiene units derived from about 30 to about 80 % 1,2-, and from
about
20 to about 70 % 1,4-incorporation of butadiene. In another preferred
embodiment,
the star polymer is derived from isoprene, butadiene, or a mixture thereof,
and further
contains from about 5 to about 35 % styrene units.
Optionally, one or both types of VI improvers used in the practice of the
invention can be provided with nitrogen-containing functional groups that
impart
CA 02606374 2007-10-09
PF2006L003 - 14 -
dispersant capabilities to the VI improver. One trend in the industry has been
to use
such "multifunctional" VI improvers in lubricants to replace some or all of
the
dispersant. Nitrogen-containing functional groups can be added to a polymeric
VI
improver by grafting a nitrogen- or hydroxyl- containing moiety, preferably a
nitrogen-containing moiety, onto the polymeric backbone of the VI improver
(functionalizing). Processes for the grafting of a nitrogen-containing moiety
onto a
polymer are known in the art and include, for example, contacting the polymer
and
nitrogen-containing moiety in the presence of a free radical initiator, either
neat, or in
the presence of a solvent. The free radical initiator may be generated by
shearing (as
in an extruder) or heating a free radical initiator precursor, such as
hydrogen peroxide.
The amount of nitrogen-containing grafting monomer will depend, to some
extent, on the nature of the substrate polymer and the level of dispersancy
required of
the grafted polymer. To impart dispersancy characteristics to both star and
linear
copolymers, the amount of grafted nitrogen-containing monomer is suitably
between
about 0.4 and about 2.2 wt. %, preferably from about 0.5 to about 1.8 wt. %,
most
preferably from about 0.6 to about 1.2 wt. %, based on the total weight of
grafted
polymer.
Methods for grafting nitrogen-containing monomer onto polymer backbones,
and suitable nitrogen-containing grafting monomers are known and described,
for
example, in U.S. Patent No. 5,141,996, WO 98/13443, WO 99/21902, U.S. Patent
No.
4,146,489, U.S. Patent No. 4,292,414, and U.S. Patent No. 4,506,056. (See also
J
Polymer Science, Part A: Polymer Chemistry, Vol. 26, 1189-1198 (1988); J.
Polymer
Science, Polymer Letters, Vol. 20, 481-486 (1982) and J. Polymer Science,
Polymer
Letters, Vol. 21, 23-30 (1983), all to Gaylord and Mehta and Degradation and
Cross-
linking of Ethylene-Propylene Copolymer Rubber on Reaction with Maleic
Anhydride and/or Peroxides; J. Applied Polymer Science, Vol. 33, 2549-2558
(1987)
to Gaylord, Mehta and Mehta.
Both the amorphous OCP and star polymer components of the present
invention are available individually as commercial products. Infineum V534TM
and
Infineum V501T" available from Infineum USA L.P. and Infineum UK Ltd. are
examples of commercially available amorphous OCP. Other examples of
commercially available amorphous OCP VI improvers include Lubrizol 7065TM and
Lubrizol 7075TM, available from The Lubrizol Corporation; Jilin OO10TM,
available
CA 02606374 2007-10-09
PF2006L003 - 15 -
from PetroChina Jilin Petrochemical Company; and NDR0135TM, available from Dow
Elastomers L.L.C. An example of a commercially available star polymer VI
improver
having an SSI equal to or less than 35 is Infineum SV200TM, available from
Infineum
USA L.P. and Infineum UK Ltd. Other examples of commercially available star
polymer VI improver having an SSI equal to or less than 35 include Infineum
SV250TM, and Infineum SV270TM, also available from Infineum USA L.P. and
Infineum UK Ltd.
Compositions of the present invention contain the specified OCP and star
polymers in a mass % ratio of from about 80:20 to about 20:80, preferably from
about
35:65 to about 65:35; more preferably from about 45:55 to about 55:45. The
polymer
compositions of the invention can be provided in the form of a dimensionally
stable,
compounded solid polymer blend, or as a concentrate, containing from about 3
to
about 20 mass %, preferably from about 6 to about 16 mass %, more preferably
from
about 9 to about 12 mass % of polymer, in oil. Alternatively, concentrates in
accordance with present invention may comprise from about 0.6 to about 16.0
mass %,
preferably from about 2.1 to about 10.4 mass %, more preferably from about 4.0
to
about 6.6 mass % of amorphous OCP and from about 2.1 to about 10.4 mass %,
preferably from about 4.0 to about 6.6 mass % of the star polymer.
Such concentrates may contain the polymer blend as the only additive, or may
further comprise additional additives, particularly other polymeric additives,
such as
lubricating oil flow improver ("LOFI"), also commonly referred to as pour
point
depressant ("PPD"). The LOFI or PPD is used to lower the minimum temperature
at
which the fluid will flow or can be poured and such additives are well known.
Typical of such additives are C8 to C18 dialkyl fumarate/vinyl acetate
copolymers,
polymethacrylates and styrene/maleic anhydride ester copolymers. Concentrates
of
the present invention may contain from about 0 to about 5 mass % of LOFI.
Preferably, at least about 98 mass %, more preferably at least about 99.5 mass
%, of
the concentrates of the present invention are VI improver, LOFI and diluent
oil.
Such VI improver concentrates can be prepared by dissolving the VI improver
polymer(s), and optional LOFI, in diluent oil using well known techniques.
When
dissolving a solid VI improver polymer to form a concentrate, the high
viscosity of
the polymer can cause poor diffusivity in the diluent oil. To facilitate
dissolution, it is
common to increase the surface are of the polymer by, for example,
pelletizing,
CA 02606374 2007-10-09
PF2006L003 - 16 -
chopping, grinding or pulverizing the polymer. The temperature of the diluent
oil can
also be increased by heating using, for example, steam or hot oil. When the
diluent
temperature is greatly increased (such as to above 100 C), heating should be
conducted under a blanket of inert gas (e.g., N2 or C02). The temperature of
the
polymer may also be raised using, for example, mechanical energy imparted to
the
polymer in an extruder or masticator. The polymer temperature can be raised
above
150 C; the polymer temperature is preferably raised under a blanket of inert
gas.
Dissolving of the polymer may also be aided by agitating the concentrate, such
as by
stirring or agitating (in either the reactor or in a tank), or by using a
recirculation
pump. Any two or more of the foregoing techniques can also be used in
combination.
Concentrates can also be formed by exchanging the polymerization solvent
(usually a
volatile hydrocarbon such as, for example, propane, hexane or cyclohexane)
with oil.
This exchange can be accomplished by, for example, using a distillation column
to
assure that substantially none of the polymerization solvent remains.
To provide a fully formulated lubricant, the solid copolymer or VI improver
concentrate can be dissolved in a major amount of an oil of lubricating
viscosity
together with an additive package containing other necessary or desired
lubricant
additives. Fully formulated lubricants in accordance with the present
invention may
comprise from about 0.4 to about 2.5 mass %, preferably from about 0.6 to
about 1.7
mass %, more preferably from about 0.8 to about 1.2 mass % of the polymer
composition of the present invention, in oil. Alternatively, fully formulated
lubricants
in accordance with the present invention may comprise from about 0.1 to about
2.0
mass %, preferably from about 0.2 to about 1.1 mass %, more preferably from
about
0.4 to about 0.7 mass % of OCP and from about 0.1 to about 2.0 mass %,
preferably
from about 0.2 to about 1.1 mass % of the star polymer.
Oils of lubricating viscosity that are useful in the practice of the present
invention may be selected from natural oils, synthetic oils and mixtures
thereof.
Natural oils include animal oils and vegetable oils (e.g., castor oil, lard
oil);
liquid petroleum oils and hydro-refined, solvent-treated or acid-treated
mineral oils of
the paraffinic, naphthenic and mixed paraffinic-naphthenic types. Oils of
lubricating
viscosity derived from coal or shale also serve as useful base oils.
Synthetic lubricating oils include hydrocarbon oils and halo-substituted
hydrocarbon oils such as polymerized and interpolymerized olefins (e.g.,
CA 02606374 2007-10-09
PF2006L003 - 1'7 -
polybutylenes, polypropylenes, propylene-isobutylene copolymers, chlorinated
polybutylenes, poly(1-hexenes), poly(1-octenes), poly(1-decenes));
alkylbenzenes
(e.g., dodecylbenzenes, tetradecylbenzenes, dinonylbenzenes, di(2-
ethylhexyl)benzenes); polyphenyls (e.g., biphenyls, terphenyls, alkylated
polyphenols); and alkylated diphenyl ethers and alkylated diphenyl sulfides
and
derivative, analogs and homologs thereof.
Alkylene oxide polymers and interpolymers and derivatives thereof where the
terminal hydroxyl groups have been modified by esterification, etherification,
etc.,
constitute another class of known synthetic oils. These are exemplified by
polyoxyalkylene polymers prepared by polymerization of ethylene oxide or
propylene
oxide, and the alkyl and aryl ethers of polyoxyalkylene polymers (e.g., methyl-
polyiso-propylene glycol ether having a molecular weight of 1000 or diphenyl
ether
of poly-ethylene glycol having a molecular weight of 1000 to 1500); and mono-
and
polycarboxylic esters thereof, for example, the acetic acid esters, mixed C3-
C8 fatty
acid esters and C13 Oxo acid diester of tetraethylene glycol.
Another suitable class of synthetic 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) with a
variety of
alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl
alcohol,
ethylene glycol, diethylene glycol monoether, propylene glycol). Examples of
such
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 sebacic acid with two moles of
tetraethylene
glycol and two moles of 2-ethylhexanoic acid.
Esters useful as synthetic oils also include those made from C5 to C12
monocarboxylic acids and polyols and polyol esters such as neopentyl glycol,
trimethylolpropane, pentaerythritol, dipentaerythritol and tripentaerythritol.
Silicon-based oils such as the polyalkyl-, polyaryl-, polyalkoxy- or
polyaryloxysilicone oils and silicate oils comprise another useful class of
synthetic
lubricants; such oils include tetraethyl silicate, tetraisopropyl silicate,
tetra-(2-
ethylhexyl)silicate, tetra-(4-methyl-2-ethylhexyl)silicate, tetra-(p-tert-
butyl-phenyl)
CA 02606374 2007-10-09
PF2006L003 - 18 -
silicate, hexa-(4-methyl-2-ethylhexyl)disiloxane, poly(methyl)siloxanes and
poly(methylphenyl)siloxanes. Other synthetic lubricating oils include liquid
esters of
phosphorous-containing acids (e.g., tricresyl phosphate, trioctyl phosphate,
diethyl
ester of decylphosphonic acid) and polymeric tetrahydrofurans.
The oil of lubricating viscosity useful in the practice of the present
invention
may comprise one or more of a Group I Group II, Group III, Group IV or Group V
oil
or blends of the aforementioned oils. Definitions for the oils as used herein
are the
same as those found in the American Petroleum Institute (API) publication
"Engine
Oil Licensing and Certification System", Industry Services Department,
Fourteenth
Edition, December 1996, Addendum 1, December 1998. Said publication
categorizes
oils as follows:
a) Group I oils contain less than 90 percent saturates and/or greater than
0.03
percent sulfur and have a viscosity index greater than or equal to 80 and less
than 120 using the test methods specified in Table 1.
b) Group II oils contain greater than or equal to 90 percent saturates and
less
than or equal to 0.03 percent sulfur and have a viscosity index greater than
or
equal to 80 and less than 120 using the test methods specified in Table 1.
Although not a separate Group recognized by the API, Group II oils having a
viscosity index greater than about 110 are often referred to as "Group II+"
oils.
c) Group III oils contain greater than or equal to 90 percent saturates and
less
than or equal to 0.03 percent sulfur and have a viscosity index greater than
or
equal to 120 using the test methods specified in Table 1.
d) Group IV oils are polyalphaolefins (PAO).
e) Group V oils are all other base stocks not included in Group I, II, III, or
IV.
Property Method
Saturates ASTM D2007
Viscosity Index ASTM D2270
Sulfur ASTM D4294
Preferably the volatility of the oil of lubricating viscosity, as measured by
the
Noack test (ASTM D5880), is less than or equal to about 40%, such as less than
or
equal to about 35%, preferably less than or equal to about 32%, such as less
than or
equal to about 28%, more preferably less than or equal to about 16%.
Preferably, the
viscosity index (VI) of the oil of lubricating viscosity is at least 100,
preferably at
least 110, more preferably greater than 120.
CA 02606374 2007-10-09
PF2006L003 - 19 -
In addition to the VI improver and LOFI, a fully formulated lubricant can
generally contain a number of other performance improving additives selected
from
ashless dispersants, metal-containing, or ash-forming detergents, antiwear
agents,
oxidation inhibitors or antioxidants, friction modifiers and fuel economy
agents, and
stabilizers or emulsifiers. Conventionally, when formulating a lubricant, the
VI
improver and/or VI improver and LOFI, will be provided to the formulator in
one
concentrated package, and combinations of the remaining additives will
provided in
one or more additional concentrated packages, oftentimes referred to as DI
(dispersant-inhibitor) packages.
Dispersants useful in the context of the present invention include the range
of
nitrogen-containing, ashless (metal-free) dispersants known to be effective to
reduce
formation of deposits upon use in gasoline and diesel engines, when added to
lubricating oils. The ashless, dispersants of the present invention comprise
an oil
soluble polymeric long chain backbone having functional groups capable of
associating with particles to be dispersed. Typically, such dispersants have
amine,
amine-alcohol or amide polar moieties attached to the polymer backbone, often
via a
bridging group. The ashless dispersant may be, for example, selected from oil
soluble
salts, esters, amino-esters, amides, imides and oxazolines of long chain
hydrocarbon-
substituted mono- and polycarboxylic acids or anhydrides thereof;
thiocarboxylate
derivatives of long chain hydrocarbons; long chain aliphatic hydrocarbons
having
polyamine moieties attached directly thereto; and Mannich condensation
products
formed by condensing a long chain substituted phenol with formaldehyde and
polyalkylene polyamine.
Preferred dispersant compositions for use with the VI improving copolymers
of the present invention are nitrogen-containing dispersants derived from
polyalkenyl-
substituted mono- or dicarboxylic acid, anhydride or ester, which dispersant
has a
polyalkenyl moiety with a number average molecular weight of from about 1500
to
3000, preferably from about 1800 to 2500. Further preferable, are succinimide
dispersants derived from polyalkenyl moieties with a number average molecular
weight of from about 1800 to 2500 and from about 1.2 to about 1.7, preferably
from
greater than about 1.3 to about 1.6, most preferably from greater than about
1.3 to
about 1.5 functional groups (mono- or dicarboxylic acid producing moieties)
per
CA 02606374 2007-10-09
PF2006L003 - 20 -
polyalkenyl moiety (a medium functionality dispersant). Functionality (F) can
be
determined according to the following formula:
F = (SAP x Ma)/((112,200 x A.I.) - (SAP x 98))
wherein SAP is the saponification number (i.e., the number of milligrams of
KOH
consumed in the complete neutralization of the acid groups in one gram of the
succinic-containing reaction product, as determined according to ASTM D94); Mn
is
the number average molecular weight of the starting olefin polymer; and A.I.
is the
percent active ingredient of the succinic-containing reaction product (the
remainder
being unreacted olefin polymer, succinic anhydride and diluent).
Generally, each mono- or dicarboxylic acid-producing moiety will react with a
nucleophilic group (amine, alcohol, amide or ester polar moieties) and the
number of
functional groups in the polyalkenyl-substituted carboxylic acylating agent
will
determine the number of nucleophilic groups in the finished dispersant.
A preferred dispersant composition is one comprising at least one polyalkenyl
succinimide, which is the reaction product of a polyalkenyl substituted
succinic
anhydride (e.g., PIBSA) and a polyamine (PAM) that has a coupling ratio of
from
about 0.65 to about 1.25, preferably from about 0.8 to about 1.1, most
preferably from
about 0.9 to about 1. In the context of this disclosure, "coupling ratio" may
be
defined as a ratio of succinyl groups in the PIBSA to primary amine groups in
the
polyamine reactant.
The dispersant(s) are preferably non-polymeric (e.g., are mono- or bis-
succinimides). The dispersant(s) of the present invention can be borated by
conventional means, as generally taught in U.S. Patent Nos. 3,087,936,
3,254,025 and
5,430,105. Boration of the dispersant is readily accomplished by treating an
acyl
nitrogen-containing dispersant with a boron compound such as boron oxide,
boron
halide boron acids, and esters of boron acids.
The dispersant or dispersants can be present in an amount sufficient to
contribute at least 0.08 wt. % of nitrogen, preferably from about 0.10 to
about 0.18
wt. %, more preferably from about 0.115 to about 0.16 wt. %, and most
preferably
from about 0.12 to about 0.14 wt. % of nitrogen to the lubricating oil
composition.
Additional additives that may be incorporated into the compositions of the
invention to enable particular performance requirements to be met are
detergents,
metal rust inhibitors, corrosion inhibitors, oxidation inhibitors, friction
modifiers,
CA 02606374 2007-10-09
PF2006L003 - 21 -
anti-foaming agents, anti-wear agents and pour point depressants. Some are
discussed
in further detail below.
Metal-containing or ash-forming detergents function both as detergents to
reduce or remove deposits and as acid neutralizers or rust inhibitors, thereby
reducing
wear and corrosion and extending engine life. Detergents generally comprise a
polar
head with a long hydrophobic tail, with the polar head comprising a metal salt
of an
acidic organic compound. The salts may contain a substantially stoichiometric
amount of the metal in which case they are usually described as normal or
neutral
salts, and would typically have a total base number or TBN (as can be measured
by
ASTM D2896) of from 0 to 80. A large amount of a metal base may be
incorporated
by reacting excess metal compound (e.g., an oxide or hydroxide) with an acidic
gas
(e.g., carbon dioxide). The resulting overbased detergent comprises
neutralized
detergent as the outer layer of a metal base (e.g. carbonate) micelle. Such
overbased
detergents may have a TBN of 150 or greater, and typically will have a TBN of
from
250 to 450 or more.
Dihydrocarbyl dithiophosphate metal salts are frequently used as antiwear and
antioxidant agents. The metal may be an alkali or alkaline earth metal, or
aluminum,
lead, tin, molybdenum, manganese, nickel or copper. The zinc salts are most
commonly used in lubricating oil and may be prepared in accordance with known
techniques by first forming a dihydrocarbyl dithiophosphoric acid (DDPA),
usually
by reaction of one or more alcohol or a phenol with P2S5 and then neutralizing
the
formed DDPA with a zinc compound. For example, a dithiophosphoric acid may be
made by reacting mixtures of primary and secondary alcohols. Alternatively,
multiple
dithiophosphoric acids can be prepared where the hydrocarbyl groups on one are
entirely secondary in character and the hydrocarbyl groups on the others are
entirely
primary in character. To make the zinc salt, any basic or neutral zinc
compound
could be used but the oxides, hydroxides and carbonates are most generally
employed.
Conunercial additives frequently contain an excess of zinc due to the use of
an excess
of the basic zinc compound in the neutralization reaction.
Oxidation inhibitors or antioxidants reduce the tendency of mineral oils to
deteriorate in service. Oxidative deterioration can be evidenced by sludge in
the
lubricant, varnish-like deposits on the metal surfaces, and by viscosity
growth. Such
oxidation inhibitors include hindered phenols, alkaline earth metal salts of
CA 02606374 2007-10-09
. A =
PF2006L003 - 22 -
alkylphenolthioesters having preferably C5 to C12 alkyl side chains, calcium
nonylphenol sulfide, oil soluble phenates and sulfurized phenates,
phosphosulfurized
or sulfurized hydrocarbons, phosphorous esters, metal thiocarbamates, oil
soluble
copper compounds as described in U.S. Patent No. 4,867,890, and molybdenum-
containing compounds and aromatic amines.
Known friction modifiers include oil-soluble organo-molybdenum compounds.
Such organo-molybdenum friction modifiers also provide antioxidant and
antiwear
credits to a lubricating oil composition. Examples of such oil soluble organo-
molybdenum compounds include dithiocarbamates, dithiophosphates,
dithiophosphinates, xanthates, thioxanthates, sulfides, and the like, and
mixtures thereof.
Particularly preferred are molybdenum dithiocarbamates,
dialkyldithiophosphates, alkyl
xanthates and alkylthioxanthates.
Other known friction modifying materials include glyceryl monoesters of
higher fatty acids, for example, glyceryl mono-oleate; esters of long chain
polycarboxylic acids with diols, for example, the butane diol ester of a
dimerized
unsaturated fatty acid; oxazoline compounds; and alkoxylated alkyl-substituted
mono-
amines, diamines and alkyl ether amines, for example, ethoxylated tallow amine
and
ethoxylated tallow ether amine.
Foam control can be provided by an antifoamant of the polysiloxane type, for
example, silicone oil or polydimethyl siloxane.
Some of the above-mentioned additives can provide a multiplicity of effects;
thus for example, a single additive may act as a dispersant-oxidation
inhibitor. This
approach is well known and need not be further elaborated herein.
It may also be necessary to include an additive which maintains the stability
of
the viscosity of the blend. Thus, although polar group-containing additives
achieve a
suitably low viscosity in the pre-blending stage it has been observed that
some
compositions increase in viscosity when stored for prolonged periods.
Additives
which are effective in controlling this viscosity increase include the long
chain
hydrocarbons functionalized by reaction with mono- or dicarboxylic acids or
anhydrides which are used in the preparation of the ashless dispersants as
hereinbefore disclosed.
Representative effective amounts of such additional additives, when used in
crankcase lubricants, are listed below:
CA 02606374 2007-10-09
~ = H s
PF2006L003 - 23 -
ADDITIVE Mass % (Broad) Mass % (Preferred)
Ashless Dispersant 0.1 - 20 1-8
Metal Detergents 0.1 - 15 0.2 - 9
Corrosion Inhibitor 0-5 0- 1.5
Metal Dih drocarb 1 Dithio hos hate 0.1 - 6 0.1 - 4
Antioxidant 0-5 0.01 - 2
Pour Point Depressant 0.01 - 5 0.01 - 1.5
Antifoaming Agent 0-5 0.001 - 0.15
Supplemental Antiwear Agents 0- 1.0 0- 0.5
Friction Modifier 0-5 0- 1.5
Basestock Balance Bal
ance
Fully formulated passenger car diesel engine lubricating oil (PCDO)
compositions of the present invention preferably have a sulfur content of less
than
about 0.4 mass %, such as less than about 0.35 mass %, more preferably less
than
about 0.03 mass %, such as less than about 0.15 mass %. Preferably, the Noack
volatility of the fully formulated PCDO (oil of lubricating viscosity plus all
additives)
will be no greater than 13, such as no greater than 12, preferably no greater
than 10.
Fully formulated PCDOs of the present invention preferably have no greater
than
1200 ppm of phosphorus, such as no greater than 1000 ppm of phosphorus, or no
greater than 800 ppm of phosphorus. Fully formulated PCDOs of the present
invention preferably have a sulfated ash (SASH) content of about 1.0 mass % or
less.
Fully formulated heavy duty diesel engine (HDD) lubricating oil compositions
of the present invention preferably have a sulfur content of less than about
1.0 mass %,
such as less than about 0.6 mass % more preferably less than about 0.4 mass %,
such
as less than about 0.15 mass %. Preferably, the Noack volatility of the fully
formulated HDD lubricating oil composition (oil of lubricating viscosity plus
all
additives) will be no greater than 20, such as no greater than 15, preferably
no greater
than 12. Fully formulated HDD lubricating oil compositions of the present
invention
preferably have no greater than 1600 ppm of phosphorus, such as no greater
than
1400 ppm of phosphorus, or no greater than 1200 ppm of phosphorus. Fully
formulated HDD lubricating oil compositions of the present invention
preferably have
a sulfated ash (SASH) content of about 1.0 mass % or less.
This invention will be further understood by reference to the following
examples. All weight percents expressed herein (unless otherwise indicated)
are
CA 02606374 2007-10-09
= =- -
PF2006L003 - 24 -
based on active ingredient (AI) content of the additive, and/or upon the total
weight of
any additive-package, or formulation which will be the sum of the AI weight of
each
additive plus the weight of total oil and/or diluent.
EXAMPLES
Example 1
Various polymeric VI improvers and VI improver blends were tested, in the
form of a 1 wt. % polymer solution in diluent oil, to determine shear
stability index,
or SSI (30 cycle; ASTM D6278-98); and thickening efficiency, or TE.
VII-1 is a commercially available star polymer having a number average
molecular
weight (Mn) of 360,000 and comprising at least 5 arms; each of which is
hydrogenated isoprene.
VII-2 is a commercially available star polymer having a number average
molecular
weight (Mn) of 460,000 and comprising at least 5 arms; each of which is a
styrene -
hydrogenated isoprene copolymer having a styrene content of about 4 mass %.
VII-3 is a commercially available, Ziegler-Natta catalyzed amorphous OCP
having an
ethylene-derived content of 46.2 mass % and a number average molecular weight
(Mn) of 67,700.
VII-4 is a commercially available, metallocene catalyzed amorphous OCP having
an
ethylene-derived content of 43.8 mass % and a number average molecular weight
(Mn) of 44,800.
VII-5 is a commercially available semicrystalline OCP having an ethylene-
derived
content of 65.9 mass % and a number average molecular weight (Mn) of 39,200.
VII-6 is a commercially available amorphous OCP having an ethylene-derived
content of 48.1 mass % and a number average molecular weight (Mn) of 44,000.
CA 02606374 2007-10-09
PF2006L003 - 25 -
Table 1
Component VII-type Ethylene kvloo kvloo after SSI TE
Content before 30- 30-cycle (%)
mass % cycle KO KO
VII-1 Star N/A* 9.15 9.11 0.9 1.91
VII-2 Star N/A* 11.25 10.47 11.9 2.51
VII-3 Amorphous 46.2 10.37 8.45 34.0 2.27
OCP
Zeigler-Natta
VII-4 Amorphous 43.8 10.66 8.62 34.3 2.35
OCP
Metallocene
VII-5 Semi- 65.9 9.61 8.64 19.8 2.05
crystalline
OCP
VII-6 Amorphous 48.1 11.53** 10.10 21.0 1.72
OCP
Zeigler-Natta
* not applicable
**solution containing 1.5 mass % polymer; all others solution containing 1.0
mass % polymer
The above VI improvers were used, together with a commercial detergent-
inhibitor (DI) package and lubricating oil flow improver (LOFI) to blend a
series of
15W40 grade lubricating oil compositions as follows (all amounts reported as
mass %):
Table 2
Component Example 1 Example 2 Example 3 Example 4
Com arative Com arative (Invention) Invention
DI Package 16.20 16.20 16.20 16.20
LOFI 0.20 0.20 0.20 0.20
Base Oil 83.01 83.13 83.01 83.01
VII-5 0.59 ---- ---- ----
VII-2 ---- 0.47 ---- ----
VII-1 & VII-3 ---- ---- 0.59 ----
55/45
VII-1 & VII-4 ---- ---- ---- 0.59
55/45
Total 100.00 100.00 100.00 100.00
CA 02606374 2007-10-09
PF2006L003 - 2C -
The viscometric properties of the above exemplified materials were evaluated;
the results are reported below:
Table 3
Example VII Treat kvloo kv loss after MRV @ - CCS @-
(polymer mass %) (cST) 90 cycle KO 25 C 20 C
% (cp) (cp)
Example 1 0.59 14.18 8.7 21322 7771
Example 2 0.47 14.33 17.0 23251 7262
Example 3 0.59 14.12 5.9 25508 7918
Example 4 0.59 14.22 9.0 26663 7629
The above VI improvers were used, together with a commercial detergent-
inhibitor (DI) package and lubricating oil flow improver (LOFI) to blend a
series of
15W40 grade lubricating oil compositions as follows (all amounts reported as
mass %):
Table 4
Component Example 5 Example 6 Example 7 Example 8
Com arative Com arative Com arative (Invention)
DI Package 11.80 11.80 11.80 11.80
LOFI 0.20 0.20 0.20 0.20
Base Oil 87.35 87.66 87.12 87.28
VII-2 0.65 ---- ---- ----
VII-5 ---- 0.74 ---- ----
VII-6 ---- ---- 0.88 ----
VII-1 & VII-3 ---- ---- ---- 0.72
(40/60)
Total 100.00 100.00 100.00 100.00
The viscometric properties of the above exemplified materials were evaluated;
the results are reported below:
CA 02606374 2007-10-09
. . - ~
PF2006L003 - 2'J -
Table 5
Example VII Treat kvloo kv loss after MRV @ CCS @ Max.
(polymer (cST) 90 cycle KO 25 C -20 C Gelation
mass %) % (cp) (cp) Index**
Example 5 0.65 14.05 19.7 26300 6250 4.1
Example 6 0.74 13.90 10.8 20700 6180 12.2
Example 7 0.88 13.92 9.8 26800 6870 4.7
Example 8 0.72 13.90 10.8 28100 6500 4.0
** Scanning Brookfield maximum gelation index (ASTM 5133)
As shown by the comparison of Table 3, the combination of VI improvers in
accordance with the present invention, at substantially constant kvloo,
provided low
temperature properties comparable to those provided by the semi-crystalline
OCP and
the star polymer alone, and improved shear stability relative to the star
polymer.
Simultaneously, as shown by the comparison of Table 5, the combination of VI
improvers, in accordance with the present invention, at substantially constant
kvloo,
provides improved thickening efficiency relative to amorphous OCP and vastly
reduced VIUbase stock interaction (indicated by the lower gelation index)
relative to
the semi-crystalline OCP.
The disclosures of all patents, articles and other materials described herein
are
hereby incorporated, in their entirety, into this specification by reference.
A
description of a composition comprising, consisting of, or consisting
essentially of
multiple specified components, as presented herein and in the appended claims,
should be construed to also encompass compositions made by admixing said
multiple
specified components. The principles, preferred embodiments and modes of
operation of the present invention have been described in the foregoing
specification.
What applicants submit is their invention, however, is not to be construed as
limited
to the particular embodiments disclosed, since the disclosed embodiments are
regarded as illustrative rather than limiting. Changes may be made by those
skilled in
the art without departing from the spirit of the invention.
