FIELD OF THE INVENTION
[0001] 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
[0002] 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, 10W-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 M
n) 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
α-olefin copolymers, polymethacrylates, diblock copolymers having a vinyl aromatic
segment and a hydrogenated polydiene segment, and star copolymers and hydrogenated
isoprene linear and star polymers.
[0003] 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 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 further 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.
[0004] Amorphous olefin copolymers (OCP) are one class of VI improver. 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).
[0005] 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.
[0007] 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.
[0008] PCT Publication WO 96/17041, June 6, 1996, discloses certain blends of star-branched styrene-isoprene polymers and ethylene
α-olefin copolymers. The publication describes the addition of an amount of the ethylene
α-olefin copolymer to the star-branched styrene-isoprene polymer as being effective
to improve the dimensional stability of the star branched polymer so that the star
branched polymer can be formed as a stable, solid bale.
[0009] 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 α-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 α-olefin copolymer improves solubility and allows for
the formation of polymer concentrates.
[0010] 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 α-olefin 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
[0011] 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 α-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).
[0012] 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.
[0013] 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 (M
n) of greater than about 1500
[0014] 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.
[0015] 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
α-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.
[0016] 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
[0017] Ethylene-α-olefin copolymers (OCP) useful in the practice of the invention include
amorphous OCP synthesized from ethylene monomer and at least one other α-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 %.
[0018] 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.
[0020] As noted, the ethylene-α-olefin copolymers are comprised of ethylene and at least
one other α-olefin. The "other" α-olefins typically include those containing 3 to
18 carbon atoms, e.g., propylene, butene-1, pentene-1, etc. Preferred are α-olefins
having 3 to 6 carbon atoms, particularly for economic reasons. The most preferred
OCP are those comprised of ethylene and propylene.
[0021] 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
- 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-norbornene, 5-isopropylidene-2-norbornene, 5-(4-cyclopentenyl)-2-norbornene;
5-cyclohexylidene-2-norbornene.
[0022] 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
[0023] 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
(M
n) as low as about 2,000 can affect the viscosity properties of an oleaginous composition.
The preferred minimum M
n is about 10,000; the most preferred minimum is about 20,000. The maximum M
n 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.
[0024] 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.
[0025] "Thickening Efficiency" ("TE") is representative of a polymers ability to thicken
oil per unit mass and is defined as:

wherein c is polymer concentration (grams of polymer/100 grams solution), kν
oil + polymer is kinematic viscosity of the polymer in the reference oil, and kν
oil is kinematic viscosity of the reference oil.
[0026] "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:

wherein kν
fresh is the kinematic viscosity of the polymer-containing solution before degradation
and kν
after 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.
[0027] "Viscosity Loss" measures the ability of the V.I polymer in a formulated lubricant
to maintain thickening power in use and is defined as:

[0028] "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.
[0029] 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 3.0.
[0030] 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.
[0031] 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.
[0032] 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 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.
[0033] 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.
[0034] The arms of the star polymer may also be a block copolymer such as one represented
by the following general formula:
A
z-(B-A)
y-B
x
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.
[0035] 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.
[0036] 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.
[0037] Preferably, the arms of the star polymer are formed via anionic polymerization to
form a living polymer. Anionic polymerization has been found to provide copolymers
having a narrow molecular weight distribution (Mw/Mn), such as a molecular weight
distribution of less than about 1.2
[0038] 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.
[0039] 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.
[0040] 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.
[0041] 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.
[0042] 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-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.
[0043] 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=CH
2)
x 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.
[0044] 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.
[0045] 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 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.
[0046] 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.
[0047] 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.
[0048] 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(Et
3)) 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 known to those skilled in the art and the foregoing list is by no means
intended to be exhaustive.
[0049] 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.
[0050] 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.
[0051] 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.
[0052] 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.
[0053] 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 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.
[0054] 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.
[0055] 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 Crosslinking 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.
[0056] Both the amorphous OCP and star polymer components of the present invention are available
individually as commercial products. Infineum V534™ and Infineum V501™ 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
7065™ and Lubrizol 7075™, available from The Lubrizol Corporation; Jilin 0010™, available
from PetroChina Jilin Petrochemical Company; and NDR0135™, 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 SV200™, 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 SV250™, and Infineum SV270™,
also available from Infineum USA L.P. and Infineum UK Ltd.
[0057] 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.
[0058] 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
C
8 to C
18 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.
[0059] 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, 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., N
2 or CO
2). 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.
[0060] 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.
[0061] 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.
[0062] 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.
[0063] Synthetic lubricating oils include hydrocarbon oils and halo-substituted hydrocarbon
oils such as polymerized and interpolymerized olefins (e.g., 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.
[0064] 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 C
3-C
8 fatty acid esters and C
13 Oxo acid diester of tetraethylene glycol.
[0065] 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.
[0066] Esters useful as synthetic oils also include those made from C
5 to C
12 monocarboxylic acids and polyols and polyol esters such as neopentyl glycol, trimethylolpropane,
pentaerythritol, dipentaerythritol and tripentaerythritol.
[0067] 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) 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.
[0068] 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 |
Test Method |
Saturates |
ASTM D2007 |
Viscosity Index |
ASTM D2270 |
Sulfur |
ASTM D4294 |
[0069] 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.
[0070] 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.
[0071] 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.
[0072] 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 polyalkenyl moiety (a medium functionality
dispersant). Functionality (F) can be determined according to the following formula:

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); M
n 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).
[0073] 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.
[0074] 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.
[0075] 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.
[0076] 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.
[0077] 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, anti-foaming
agents, anti-wear agents and pour point depressants. Some are discussed in further
detail below.
[0078] 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.
[0079] 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 P
2S
5 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. Commercial
additives frequently contain an excess of zinc due to the use of an excess of the
basic zinc compound in the neutralization reaction.
[0080] 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 alkylphenolthioesters having
preferably C
5 to C
12 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.
[0081] 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.
[0082] 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 monoamines, diamines and alkyl
ether amines, for example, ethoxylated tallow amine and ethoxylated tallow ether amine.
[0083] Foam control can be provided by an antifoamant of the polysiloxane type, for example,
silicone oil or polydimethyl siloxane.
[0084] 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.
[0085] 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.
[0086] Representative effective amounts of such additional additives, when used in crankcase
lubricants, are listed below:
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 Dihydrocarbyl Dithiophosphate |
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 |
Balance |
[0087] 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.
[0088] 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.
[0089] This invention will be further understood by reference to the following examples.
All weight percents expressed herein (unless otherwise indicated) are 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
[0090] 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.
Table 1
Component |
VII-type |
Ethylene Content (mass %) |
kv100 before 30-cycle KO |
kv100 after 30-cycle KO |
SSI (%) |
TE |
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 OCP Zeigler-Natta |
46.2 |
10.37 |
8.45 |
34.0 |
2.27 |
VII-4 |
Amorphous OCP Metallocene |
43.8 |
10.66 |
8.62 |
34.3 |
2.35 |
VII-5 |
Semi-crystalline OCP |
65.9 |
9.61 |
8.64 |
19.8 |
2.05 |
VII-6 |
Amorphous OCP Zeigler-Natta |
48.1 |
11.53** |
10.10 |
21.0 |
1.72 |
* not applicable
**solution containing 1.5 mass % polymer; all others solution containing 1.0 mass
% polymer |
[0091] 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 (Comparative) |
Example 2 (Comparative) |
Example 3 (Invention) |
Example 4 (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 (55/45) |
---- |
---- |
0.59 |
---- |
VII-1 & VII-4 (55/45) |
---- |
---- |
---- |
0.59 |
Total |
100.00 |
100.00 |
100.00 |
100.00 |
[0092] The viscometric properties of the above exemplified materials were evaluated; the
results are reported below:
Table 3
Example |
VII Treat (polymer mass %) |
kv100 (cST) |
kv loss after 90 cycle KO (%) |
MRV @ -25°C (cp) |
CCS @ -20°C (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 |
[0093] 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 (Comparative) |
Example 6 (Comparative) |
Example 7 (Comparative) |
Example 8 (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 (40/60) |
---- |
---- |
---- |
0.72 |
Total |
100.00 |
100.00 |
100.00 |
100.00 |
[0094] The viscometric properties of the above exemplified materials were evaluated; the
results are reported below:
Table 5
Example |
VII Treat (polymer mass %) |
kv100 (cST) |
kv loss after 90 cycle KO (%) |
MRV @ -25°C (cp) |
CCS @ -20°C (cp) |
Max. Gelation 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) |
[0095] As shown by the comparison of Table 3, the combination of VI improvers in accordance
with the present invention, at substantially constant kv
100, 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
kv
100, provides improved thickening efficiency relative to amorphous OCP and vastly reduced
VII/base stock interaction (indicated by the lower gelation index) relative to the
semi-crystalline OCP.
[0096] 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.
1. A lubricating oil composition comprising a major amount of oil of lubricating viscosity,
and a viscosity index (VI) improver composition comprising a first polymer comprising
an amorphous ethylene - α olefin copolymer or ethylene - α olefin -diene terpolymer
having a crystallinity of not greater 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 1% to 35% (30 cycle).
2. A lubricating oil composition as claimed in claim 1, wherein the first polymer and
the second polymer are present in a mass % ratio of from 80:20 to 20:80.
3. A lubricating oil composition, as claimed in claim 1 or 2, wherein said first polymer
is an ethylene-propylene copolymer having less than 2% of units derived from diene.
4. A lubricating oil composition, as claimed in claim 3, wherein said ethylene-propylene
copolymer is an amorphous copolymer having a shear stability index (SSI) of from 20%
to 50%.
5. A lubricating oil composition, as claimed in claim 3 or 4, wherein said ethylene-propylene
copolymer is polymerized via Ziegler-Natta catalysis and contains from 40 mass % to
55 mass % ethylene.
6. A lubricating oil composition, as claimed in claim 3 or 4, wherein said ethylene-propylene
copolymer is polymerized via single site (metallocene) catalysis and contain from
35 mass % to 50 mass % ethylene.
7. A lubricating oil composition, as claimed in claim 1 or 2, wherein said second polymer
is a hydrogenated polymer derived from a polyolefinic linking agent coupled to arms
comprising diene units and optionally vinyl aromatic units.
8. A lubricating oil composition, as claimed in claim 7, wherein said diene units comprise
butadiene, isoprene, or a mixture thereof.
9. A lubricating oil composition, as claimed in claim 8, wherein said second polymer
comprises from 75 to 90 mass% of units derived from isoprene, and from 10 to 25 mass
% of units derived from butadiene, wherein greater than 80 mass % of the butadiene
derived units are incorporated as 1, 4 addition product.
10. A lubricating oil composition, as claimed in claim 8, wherein said second polymer
comprises butadiene wherein from 30 to 80 mass % of the butadiene units are incorporated
as 1,2-addition product and from 20 to 70 mass % of the butadiene units are incorporated
as 1,4-addition product.
11. A lubricating oil composition, as claimed in claim 8, wherein said second polymer
further comprises from 0 to 35 mass % of units derived from styrene.
12. A lubricating oil composition, as claimed in claim 1 or 2, wherein said first polymer
is an ethylene-propylene amorphous copolymer having an SSI of from 20% to 50%; and
said second polymer comprises from 75 to 90 mass% of units derived from isoprene,
and from 10 to 25 mass % of units derived from butadiene; greater than 80 mass % of
the butadiene derived units are incorporated as 1, 4 addition product; and said second
polymer has an SSI of from 1% to 15%.
13. A lubricating oil composition as claimed in any one of the preceding claims, further
comprising a nitrogenous dispersant derived from a polyalkene having a number average
molecular weight (Mn) of greater than 1500.
14. A viscosity index (VI) improver concentrate comprising diluent oil; a first polymer
that is an amorphous ethylene α-olefin copolymer having a crystallinity of not greater
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 1% to 35% (30 cycle), wherein
the total amount of polymer in the concentrate, including at least said first polymer
and said second polymer is at least 5 mass%, based on the total mass of the concentrate.
15. A VI improver concentrate, as claimed in claim 14, wherein the first polymer and the
second polymer are present in a mass % ratio of from 80:20 to 20:80.
16. A VI improver concentrate, as claimed in claim 14 or 15, wherein said first polymer
is an ethylene-propylene copolymer having less than 2% of units derived from diene.
17. A VI improver concentrate, as claimed in claim 16, wherein said ethylene-propylene
copolymer is an amorphous copolymer having a shear stability index (SSI) of from 20%
to 50%.
18. A VI improver concentrate, as claimed in claim 16 or 17, wherein said ethylene-propylene
copolymer is polymerized via Ziegler-Natta catalysis and contains from 40 mass % to
55 mass % ethylene.
19. A VI improver concentrate, as claimed in claim 16 or 17, wherein said ethylene-propylene
copolymer is polymerized via single site (metallocene) catalysis and contain from
35 mass % to 55 mass % ethylene.
20. A VI improver concentrate, as claimed in any one of claims 15 to 19, wherein said
second polymer is a hydrogenated polymer derived from a polyolefinic linking agent
coupled to arms comprising diene units and optionally vinyl aromatic units.
21. A VI improver concentrate, as claimed in claim 20, wherein said diene units comprise
butadiene, isoprene, or a mixture thereof.
22. A VI improver concentrate, as claimed in claim 20, wherein said second polymer comprises
from 75 to 90 mass% of units derived from isoprene, and from 10 to 25 mass % of units
derived from butadiene, wherein greater than 80 mass % of the butadiene derived units
are incorporated as 1, 4-addition product.
23. A VI improver concentrate, as claimed in claim 20, wherein said second polymer comprises
butadiene units wherein from 30 to 80 mass % of the butadiene units are incorporated
as 1,2-addition product and from 20 to 70 mass % of the butadiene units are incorporated
as 1,4-addition product.
24. A VI improver concentrate, as claimed in claim 21, wherein said second polymer further
comprises from 5 to 35 mass % of units derived from styrene.
25. A VI improver concentrate, as claimed in claim 15, wherein said first polymer is an
ethylene-propylene amorphous copolymer having an SSI of from 35% to 50%; and said
second polymer comprises from 75 to 90 mass% of units derived from isoprene, and from
10 to 25 mass % of units derived from butadiene; greater than 80 mass % of the butadiene
derived units are incorporated as 1, 4 addition product; and said second polymer has
an SSI of from 1% to 15%.