Note: Descriptions are shown in the official language in which they were submitted.
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ENGINE CRANKCASE LUBRICANT COMPOSITIONS
WITH AIR RELEASE CHARACTERISTICS,
THEIR PREPARATION AND USE
FIELD OF THE INVENTION
[001j The present invention relates to lubricant compositions with good air
release characteristics, their preparation and use.
BACKGROUND OF THE INVENTION
[0021 Lubricating oils, including hydraulic oils and crankcase oils, often are
used in environments in which the oil is subject to mechanical agitation in
the
presence of air. As a consequence, the air becomes entrained in the oil and
also
forms a foam.
[003) Foam appears on the surface of an oil as air bubbles greater than 1 mm
in diameter. Air entrainment refers to the dispersion within the oil of air
bubbles
less than 1 mm in diameter.
=
10041 Air entrainment and foaming in lubricating compositions are undesir-
able phenomena. For example, air entrainment reduces the bulk modules of the
fluid resulting in spongy operation and poor control of a hydraulic system's
response. It can result in reduced viscosity of a lubricating composition.
Both air
entrainment and foaming can contribute to fluid deterioration due to enhanced
oil oxidation.
[0051 Air entrainment, however, is more problematic than foaming. Foaming
is typically depressed in lubricating compositions by the use of antifoornant
additives. These additives expedite the breakup of a foam, but they do not
inhibit
air entrainment. Indeed, some antifoamants, such as silicone oils typically
used
in diesel and automotive crankcase oils, are known to retard air release.
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[006] Air release and air entrainment are referred to herein as the air
release
characteristics of a lubricating composition and are determined in accordance
with the method of ASTM D 3427.
[007] US Patent 6,090,758 discloses that foaming in a lubricant comprising a
slack wax isomerate is effectively reduced by use of an antifoamant exhibiting
a
spreading coefficient of about 2 mN/m without increasing the air release time.
While the specified antifoamant does not degrade the air release time, further
improvements in enhancing air release characteristics are desirable. Indeed,
many modern gasoline and diesel engines are designed to use the crankcase oil
to function as a hydraulic fluid to operate fuel injectors, valvetrain
controls and
the like. For these functions, low air entrainment and rapid air release are
indicative of high performance lubricants.
[0081 US Patent 6,713,438 discloses a lubricating oil composition that
exhibits improved air release characteristics. The composition comprises a
basestock, typically a polyalphaolefin (PAO), and two polymers of different
molecular weight. One of the polymers is a viscoelastic fluid having a shear
stress greater than 11 kPa such as a high VI PAO, and the other preferably is
a
block copolymer. Synthetic basestocks are relatively expensive, and it would
be
desirable to provide lubricants having good air release characteristics
without
their use.
SUMMARY OF THE INVENTION
[009] Is has now been found that the air release characteristics in
lubricating
compositions can be enhanced by formulating the lubricating composition with a
base oil derived from a waxy hydrocarbon produced in a Fischer-Tropsch (F-T)
synthesis process.
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[010] Thus, one aspect of the invention comprises a method for improving the
air release characteristics of a lubricating composition comprising a major
amount of a lubricating base oil and a minor amount of at least one lubricant
additive, the method comprising using as the base oil an effective amount of
one
or more oils derived from a waxy hydrocarbon produced in a F-T synthesis
process.
[011] Another aspect of the invention is a lubricating composition comprising
a major amount of a lubricating base oil comprising an oil or mixture of oils
derived from a waxy hydrocarbon produced in an F-T synthesis process and a
minor amount of at lease one lubricant additive, the composition being
substantially free of a viscoelastic fluid having both a shear stress greater
than 11
1cPa and a viscosity greater than 30 cSt at 100 C; further characterized as
entraining less than 1.7% air in 2 min. and an air release rate greater than
0.3%/min. when measured at 500C by ASTM Test Method D 3427.
[0121 In another aspect, lubricating oils formulated according to the
invention
are particularly useful as crankcase lubricants in engines wherein the
lubricant
provides a lubricating and hydraulic function.
[013] The foregoing summary and the following detailed description are
exemplary of the various aspects and embodiments of the claimed invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[014] Figures 1 and 2 are graphical representations showing the improvement
in air release characteristics achieved by the invention.
DETAILED DESCRIPTION OF THE INVENTION
[015] Throughout the specification the specific properties referred to have
been determined by the following method:
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(1) Air release characteristics -- ASTM D 3428
(2) TBN or total base number -- ASTM D2896
(3) Kinematic viscosity -- ASTM D 445
(4) Viscosity index -- ASTM D 2270
(5) Shear stress -- As per SAE Paper No. 872043.
[016] For convenience, the invention will be described by reference to engine
oils especially internal combustion engine oils; however, it should be
appreciated that in some aspects the invention is also applicable to other
types of
lubricants, such as hydraulic fluids, industrial oils and the like.
[017] A key advantage of the present invention is that it provides a method to
control the air release characteristics of a lubricating composition by
formulating
the composition with a base oil derived from a waxy hydrocarbon produced in
an F-T synthesis process.
[018] As is known to those skilled in the art, in an F-T synthesis process, a
synthesis gas comprising a mixture of H2 and CO is catalytically converted
into
hydrocarbons and preferably liquid hydrocarbons. The mole ratio of the
hydrogen to the carbon monoxide may broadly range from about 0.5 to 4, but
which is more typically within the range of from about 0.7 to 2.75 and
preferably
from about 0.7 to 2.5.
[019] As is well known, F-T synthesis processes include processes in which
the catalyst is in the form of a fixed bed, a fluidized bed or as a slurry of
catalyst
particles in a hydrocarbon slurry liquid. The stoichiometric mole ratio for an
F-T
synthesis reaction is 2.0, but there are many reasons for using other than a
stoichiometric ratio as those skilled in the art know. In cobalt slurry
hydrocarbon
synthesis process the feed mole ratio of the 112 to CO is typically about
2.1/1.
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10201 The synthesis gas comprising a mixture of H2 and CO is bubbled up
into the bottom of the slurry and reacts in the presence of the particulate F-
T
synthesis catalyst in the slurry liquid at conditions effective to form hydro-
carbons, a portion of which are liquid at the reaction conditions and which
comprise the hydrocarbon slurry liquid. The synthesized hydrocarbon liquid is
separated from the catalyst particles as filtrate by means such as filtration,
although other separation means such as centrifugation can be used. Some of
the
synthesized hydrocarbons pass out the top of the hydrocarbon synthesis reactor
as vapor, along with unreacted synthesis gas and other gaseous reaction
products. Some of these overhead hydrocarbon vapors are typically condensed to
liquid and combined with the hydrocarbon liquid filtrate. Thus, the initial
boiling
point of the filtrate may vary depending on whether or not some of the
condensed hydrocarbon vapors have been combined with it.
[021] Slurry hydrocarbon synthesis process conditions vary somewhat
depending on the catalyst and desired products. Typical conditions effective
to
form hydrocarbons comprising mostly C5+ paraffins, (e.g., C5+-C200) and
preferably C10+ paraffins, in a slurry hydrocarbon synthesis process employing
a catalyst comprising a supported cobalt component include, for example,
temperatures, pressures and hourly gas space velocities in the range of from
about 320-850 F, 80-600 psi and 100-40,000 WhrN, expressed as standard
volumes of the gaseous CO and H2 mixture (0 C, 1 atm) per hour per volume of
catalyst, respectively. The term "C5+" is used herein to refer to hydrocarbons
with a carbon number of greater than 4, but does not imply that material with
carbon number 5 has to be present.
[022] Similarly other ranges quoted for carbon number do not imply that
hydrocarbons having the limit values of the carbon number range have to be
present, or that every carbon number in the quoted range is present. It is
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preferred that the hydrocarbon synthesis reaction be conducted under
conditions
in which limited or no water gas shift reaction occurs and more preferably
with
no water gas shift reaction occurring during the hydrocarbon synthesis. It is
also
preferred to conduct the reaction under conditions to achieve an alpha of at
least
0.85, preferably at least 0.9 and more preferably at least 0.92, so as to
synthesize
more of the more desirable higher molecular weight hydrocarbons. This has been
achieved in a slurry process using a catalyst containing a catalytic cobalt
component. Those skilled in the art know that by alpha is meant the Schultz-
Flory kinetic alpha. While suitable F-T reaction types of catalyst comprise,
for
example, one or more Group VIII catalytic metals such as Fe, Ni, Co, Ru and
Re, it is preferred that the catalyst comprise a cobalt catalytic component.
In one
embodiment the catalyst comprises catalytically effective amounts of Co and
one
or more of Re, Ru, Fe, Ni, Th, Zr, Hf, U, Mg and La on a suitable inorganic
support material, preferably one which comprises one or more refractory metal
oxides. Preferred supports for Co containing catalysts comprise titania.
Particularly useful catalysts and their preparation are known and
illustrative, but
nonlimiting examples may be found, for example, in U.S. Pat. Nos. 4,568,663;
4,663,305; 4,542,122; 4,621,072 and 5,545,674.
10231 The waxy hydrocarbon produced in the F-T synthesis process, i.e., the
F-T wax, preferably has an initial boiling point in the range of from 6500F to
7500F and preferably boils up to an end point of at least 10500F.
0241 When a boiling range is quoted herein it defines the lower and/or upper
distillation temperature used to separate the fraction. Unless specifically
stated
(for example, by specifying that the fraction boils continuously or
constitutes the
entire range) the specification of a boiling range does not require any
material at
the specified limit has to be present, rather it excludes material boiling
outside
that range.
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[025] The waxy feed preferably comprises the entire 650-750 F+ fraction
formed by the hydrocarbon synthesis process, having an initial cut point
between
650 F and 750 F determined by the practitioner and an end point, preferably
above 1050 F, determined by the catalyst and process variables employed by the
practitioner for the synthesis. Such fractions are referred to herein as "650-
750 F+ fractions".
10261 By contrast, "650-750 F- fractions" refers to a fraction with an
unspecified initial cut point and an end point somewhere between 650 F and
750 F. Waxy feeds may be processed as the entire fraction or as subsets of the
entire fraction prepared by distillation or other separation techniques. The
waxy
feed also typically comprises more than 90%, generally more than 95% and
preferably more than 98 wt% paraffinic hydrocarbons, most of which are normal
paraffins. It has negligible amounts of sulfur and nitrogen compounds (e.g.,
less
than 1 wppm of each), with less than 2,000 wppm, preferably less than 1,000
wppm and more preferably less than 500 wppm of oxygen, in the form of
oxygenates. Waxy feeds having these properties and useful in the process of
the
invention have been made using a slurry F-T process with a catalyst having a
catalytic cobalt component, as previously indicated.
[027] The process of making the lubricating base oil from the F-T wax may
be characterized as a hydrodewaxing process. This process may be operated in
the presence of hydrogen, and hydrogen partial pressures range from about 600
to 60001cPa. The ratio of hydrogen to the hydrocarbon feedstock (hydrogen
circulation rate) typically range from about 10 to 3500 n.1.1.-1 (56 to 19,660
SCF/bbl) and the space velocity of the feedstock typically ranges from about
0.1
to 20 LHSV, preferably 0.1 to 10 LHSV.
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[0281 Hydrodewaxing catalysts useful in the conversion of the n-paraffin
waxy feedstocks disclosed herein to form the isoparaffinic hydrocarbon base
oil
are zeolite catalysts, such as ZSM-5, ZSM-11, ZSM-23, ZSM-35, ZSM-12,
ZSM-38, ZSM-48, offretite, ferrierite, zeolite beta, zeolite theta, and
zeolite
alpha, as disclosed in USP 4,906,350. These catalysts are used in combination
with Group VIII metals, in particular palladium or platinum. The Group VIII
metals may be incorporated into the zeolite catalysts by conventional
techniques,
such as ion exchange.
[0291 In one embodiment, conversion of the waxy feedstock may be
conducted over a combination of Pt/zeolite beta and Pt/ZSM-23 catalysts in the
presence of hydrogen. In another embodiment, the process of producing the
lubricant oil base stocks comprises hydroisomerization and dewaxing over a
single catalyst, such as Pt/ZSM-35. In yet another embodiment, the waxy feed
can be fed over Group VIII metal loaded ZSM-48, preferably Group VIII noble
metal loaded ZSM-48, more preferably Pt/ZSM-48 in either one stage or two
stages. In any case, useful hydrocarbon base oil products may be obtained.
Catalyst ZSM-48 is described in USP 5,075,269. The use of the Group VIII
metal loaded ZSM-48 family of catalysts, preferably platinum on ZSM-48, in the
hydroisomerization of the waxy feedstock eliminates the need for any
subsequent, separate dewaxing step, and is preferred.
[030] A dewaxing step, when needed, may be accomplished using either well
known solvent or catalytic dewaxing processes and either the entire hydro-
isomerate or the 650-750 F+ fraction may be dewaxed, depending on the
intended use of the 650-750 F- material present, if it has not been separated
from
the higher boiling material prior to the dewaxing. In solvent dewaxing, the
hydroisomerate may be contacted with chilled solvents such as acetone, methyl
ethyl ketone (MEK), methyl isobutyl ketone (MIBK), mixtures of MEIC/MIBK,
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or mixtures of MEK/toluene and the like, and further chilled to precipitate
out
the higher pour point material as a waxy solid which is then separated from
the
solvent-containing lube oil fraction which is the raffinate. The raffinate is
typically further chilled in scraped surface chillers to remove more wax
solids.
[031] Low molecular weight hydrocarbons, such as propane, are also used for
dewaxing, in which the hydroisomerate is mixed with liquid propane, a least a
portion of which is flashed off to chill down the hydroisomerate to
precipitate
out the wax. The wax is separated from the raffinate by filtration, membrane
separation or centrifugation. The solvent is then stripped out of the
raffinate,
which is then fractionated to produce the preferred base stocks useful in the
present invention. Also well known is catalytic dewaxing, in which the
hydroisomerate is reacted with hydrogen in the presence of a suitable dewaxing
catalyst at conditions effective to lower the pour point of the
hydroisomerate.
Catalytic dewaxing also converts a portion of the hydroisomerate to lower
boiling materials, in the boiling range, for example, 650-750 F-, which are
separated from the heavier 650-750 F+ base stock fraction and the base stock
fraction fractionated into two or more base stocks. Separation of the lower
boiling material may be accomplished either prior to or during fractionation
of
the 650-750 F+ material into the desired base stocks.
[0321 Any dewaxing catalyst which will reduce the pour point of the
hydroisomerate and preferably those which provide a large yield of lube oil
base
stock from the hydroisomerate may be used. These include shape selective
molecular sieves which, when combined with at least one catalytic metal
component, have been demonstrated as useful for dewaxing petroleum oil
fractions and include, for example, ferrierite, mordenite, ZSM-5, ZSM-11,
ZSM-23, ZSM-35, ZSM-22 also known as theta one or TON, and the
silicoaluminophosphates known as SAPO's. A dewaxing catalyst which has
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been found to be unexpectedly particularly effective comprises a noble metal,
preferably Pt, composited with H-mordenite. The dewaxing may be
accomplished with the catalyst in a fixed, fluid or slurry bed. Typical
dewaxing
conditions include a temperature in the range of from about 400-600 F, a
pressure of 500-900 psig, H2 treat rate of 1500-3500 SCF/B for flow-through
reactors and LHSV of 0.1-10, preferably 0.2-2Ø The dewaxing is typically
conducted to convert no more than 40 wt% and preferably no more than 30 wt%
of the hydroisomerate having an initial boiling point in the range of 650-750
F
to material boiling below its initial boiling point.
[0331 The base oil suitable for use in the invention will have a kinematic
viscosity in the range of about 2 to 50 nun2/s at 1000C and preferably in the
range of about 3.5 to 30 mm2/s at 1000C and a VI greater than about 130,
preferably greater than 135 and more preferably 140 or greater.
[034j The base oil of the invention is further characterized as having a pour
point of -50C or lower, preferably about -100C or lower and under some
conditions advantageously having pour points of about -250C to about -400C.
[0351 A preferred base oil is one comprising paraffinic hydrocarbon
components in which the extent of branching, as measured by the percentage of
methyl hydrogens (BI), and the proximity of branching, as measured by the
percentage of recurring methylene carbons which are four or more carbons
removed from an end group or branch (CH2 > 4), are such that: (a) BI-0.5(CH2
> 4) >15; and (b) BI-F0.85(CH2 2:4) <45 as measured over said liquid
hydrocarbon composition as a whole.
[0361 The preferred base oil can be further characterized, if necessary, as
having less than 0.1 wt% aromatic hydrocarbons, less than 20 wppm nitrogen
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containing compounds, less than 20 wppm sulfur containing compounds, a pour
point of less than -18 C, preferably less than -30 C, a preferred BI > 25.4
and
(CH2 >4) < 22.5. They have a nominal boiling point of 370 C, on average they
average fewer than 10 hexyl or longer branches per 100 carbon atoms and on
average have more than 16 methyl branches per 100 carbon atoms. They also
can be characterized by a combination of dynamic viscosity, as measured by
CCS at -40 C, and kinematic viscosity, as measured at 100 C represented by the
formula: DV (at -40 C) <2900 (KV @ 100 C) - 7000.
[037] The preferred base oil is also characterized as comprising a mixture of
branched paraffins characterized in that the lubricant base oil contains at
least
90% of a mixture of branched paraffins, wherein said branched paraffins are
paraffins having a carbon chain length of about C20 to about C40, a molecular
weight of about 280 to about 562, a boiling range of about 650 F to about
1050 F, and wherein said branched paraffins contain up to four alkyl branches
and wherein the free carbon index of said branched paraffins is at least about
3.
10381 In the above the Branching Index (BI), Branching Proximity (CH2 > 4),
and Free Carbon Index (FCI) are determined as follows:
Branching Index
TM
[0391 A 359.88 MHz 1 H solution NMR spectrum is obtained on a Bruker
360 MHz MAX spectrometer using 10% solutions in CDCI3. TMS is the
internal chemical shift reference. CDC13 solvent gives a peak located at 7.28.
All
spectra are obtained under quantitative conditions using 90 degree pulse (10.9
lis), a pulse delay time of 30 s, which is at least five times the longest
hydrogen
spin-lattice relaxation time (T1), and 120 scans to ensure good signal-to-
noise
ratios.
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10401 H atom types are defined according to the following regions:
9.2-6.2 ppm hydrogens on aromatic rings;
6.2-4.0 ppm hydrogens on olefinic carbon atoms;
4.0-2.1 ppm benzylic hydrogens at the a-position to aromatic rings;
2.1-1.4 ppm paraffinic CH methine hydrogens;
1.4-1.05 ppm paraffinic CH2 methylene hydrogens;
1.05-0.5 ppm paraffinic CH3 methyl hydrogens.
(041J The branching index (BD is calculated as the ratio in percent of non-
benzylic methyl hydrogens in the range of 0.5 to 1.05 ppm, to the total non-
benzylic aliphatic hydrogens in the range of 0.5 to 2.1 ppm.
Branching Proximity (CH2 > 4)
10421 A 90.5 MHz3CMR single pulse and 135 Distortionless Enhancement
by Polarization Transfer (DEPT) NMR spectra are obtained on a Brucker 360
MHzAMX spectrometer using 10% solutions in CDCL3. TMS is the internal
chemical shift reference. CDCL3 solvent gives a triplet located at 77.23 ppm
in
the 13C spectrum. All single pulse spectra are obtained under quantitative
conditions using 45 degree pulses (6.3 ps), a pulse delay time of 60 s, which
is at
least five times the longest carbon spin-lattice relaxation time (T1), to
ensure
complete relaxation of the sample, 200 scans to ensure good signal-to-noise
ratios, and WALTZ-16 proton decoupling.
[043] The C atom types CH3, CH2, and CH are identified from the 135
DEPT 13C NMR experiment. A major CH2 resonance in all 13C NMR spectra
at -29.8 ppm is due to equivalent recurring methylene carbons which are four
or
more removed from an end group or branch (CH2 > 4). The types of branches
are determined based primarily on the 13C chemical shifts for the methyl
carbon
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at the end of the branch or the methylene carbon one removed from the methyl
on the branch.
[0441 Free Carbon Index (FCI). The FCI is expressed in units of carbons, and
is a measure of the number of carbons in an isoparaffin that are located at
least 5
carbons from a terminal carbon and 4 carbons way from a side chain. Counting
the terminal methyl or branch carbon as "one" the carbons in the FCI are the
fifth
or greater carbons from either a straight chain terminal methyl or from a
branch
methane carbon. These carbons appear between 29.9 ppm and 29.6 ppm in the
carbon-13 spectrum. They are measured as follows:
a. calculate the average carbon number of the molecules in the sample
which is accomplished with sufficient accuracy for lubricating oil materials
by
simply dividing the molecular weight of the sample oil by 14 (the formula
weight of CH2);
b. divide the total carbon-13 integral area (chart divisions or area
counts) by the average carbon number from step a. to obtain the integral area
per
carbon in the sample;
c. measure the area between 29.9 ppm and 29.6 ppm in the sample; and
d. divide by the integral area per carbon from step b. to obtain FCI.
[0451 Branching measurements can be performed using any Fourier
Transform NMR spectrometer. Preferably, the measurements are performed
using a spectrometer having a magnet of 7.0T or greater. In all cases, after
verification by Mass Spectrometry, UV or an NMR survey that aromatic carbons
were absent, the spectral width was limited to the saturated carbon region,
about
0-80 ppm vs. TMS (tetramethylsilane). Solutions of 15-25 percent by weight in
chloroform-di were excited by 45 degrees pulses followed by a 0.8 sec
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acquisition time. In order to minimize non-uniform intensity data, the proton
decoupler was gated off during a 10 sec delay prior to the excitation pulse
and
on during acquisition. Total experiment times ranged from 11-80 minutes. The
DEPT and APT sequences were carried out according to literature descriptions
with minor deviations described in the Varian or Bruker operating manuals.
[046] DEPT is Distortionless Enhancement by Polarization Transfer. DEPT
does not show quaternaries. The DEPT 45 sequence gives a signal for all
carbons bonded to protons. DEPT 90 shows CH carbons only. DEPT 135 shows
CH and CH3 up and CH2 180 degrees out of phase (down). APT is Attached
Proton Test. It allows all carbons to be seen, but if CH and CH3 are up, then
quaternaries and CH2 are down. The sequences are useful in that every branch
methyl should have a corresponding CH. And the methyls are clearly identified
by chemical shift and phase. The branching properties of each sample are deter-
mined by C-13 NMR using the assumption in the calculations that the entire
sample is isoparaffinic. Corrections are not made for n-paraffins or cyclo-
paraffins, which may be present in the oil samples in varying amounts. The
cycloparaffins content is measured using Field Ionization Mass Spectroscopy
(FIMS).
[0471 A particularly preferred lubricating composition of the invention
comprises a major amount of a base oil comprising an oil or mixture of oils
derived from waxy hydrocarbons produced in an F-T process and a minor
amount of at least one lubricant additive. By major amount is meant greater
than
50 wt%, preferably between 65 wt% to 80 wt% and conveniently between 75
wt% to 90 wt%.
[048] The base oil suitable for the composition is that described in detail
above.
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[049] In one aspect, the suitable base oil may comprise a blend of an
effective
amount of an oil or mixture of oils derived from waxy hydrocarbons produced in
an F-T process with conventional lubricating oils. By effective amount is
meant
that the ratio of the F-T derived oil to the conventional oil is sufficient to
provide
an improvement in the air release characteristics of the mixture over that of
the
conventional oil alone.
10501 Among suitable lubricant additives are alkaline earth metal detergents,
such as metal salicylates, phenates and sulfonates. The preferred alkaline
earth
metal detergents for the composition of the invention are calcium, magnesium
and barium salicylates and preferably calcium salicylates. As commonly used in
the art, the term "salicylate" refers to salts of hydrocarbyl-substituted
salicylic
acid. Typically, the salicylate will be a mono- or di-substituted salicylic
acid
having from about 8 to about 30 or more carbon atoms in the hydrocarbyl
substituent. The detergent may be neutral, overbased, or a mixture thereof.
Borated detergents may also be used. In a particularly preferred embodiment,
the metal salicylate detergent is a calcium salicylate and present in 0.5 wt%
to
about 4 wt% based on the total weight of the lubricating composition.
[051] Another component of the composition of the invention may be a
dispersant or mixture of dispersants. Suitable dispersants include succinimide
depressants, ester dispersants, ester-amide dispersants, Mannich dispersants,
polyether dispersants, and the like. Preferably, the dispersant is a
succinimide
dispersant, especially a polybutenyl succinimide. The molecular weight of the
polybutenyl group may range from about 800 to about 4,000 or more and
preferably from about 1300 to about 2500. The dispersant may be head capped
or borated or both.
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10521 Another component of the composition may be an antiwear agent.
Commonly used crankcase antiwear agents include zinc dialkyldithiophosphates
(ZDDP), sulfurized olefins, polysulfides of thiophosphorous acids or amine
salts
thereof and the phosphorous acid esters, esters of glycerol and the like. In
the
ZDDP the alkyl groups typically will have from 3 to about 18 carbon atoms with
3 to 10 carbon atoms being preferred. The ZDDP is typically used in amounts of
from about 0.4 to 1.4 wt% of the total lubricating composition, although for a
preferred lubricating composition having less than about 0.08% phosphorous,
the amount of ZDDP used will be in the range of about 0.01 wt% to about 0.1
wt% of the total lubricating composition.
10531 Another class of suitable additives for the composition of the invention
includes antioxidants such as aminic and phenolic antioxidants exemplified by
secondary aromatic amines and hindered phenols. Typical phenolic antioxidants
include derivatives of dihydroxy aryl compounds in which the hydroxyl groups
are in the o- or p- position to each other and which contain alkyl
substituents and
bis-phenolic antioxidants. Typical aminic antioxidants include allcylated
aromatic amines especially those in which the alkyl group contains no more
than
14 carbon atoms. Mixtures of phenolic and aminic antioxidants also may be
used. Such additives may be used in an amount of about 0.01 to 5 wt%, and
preferably about 0.1 wt% to about 2 wt%.
10541 Other additives often used in lubrication compositions include VI
improvers such as linear or radial styrene-isoprene VI improvers olefin
copolymers, polymethacrylates and the like, metal deactivators such as
benzotriazole, thiadiozoles and their derivatives, and pour point depressants
such
as alkylnaphthalenes, polymethacrylates, fumarates and the like.
10551 The composition will typically comprise various lubricant additives in
amounts, on an active ingredient basis, from about 0.5 wt% to about 25 wt% and
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preferably from about 2 wt% to about 10 wt% based on the total weight of the
composition.
[056] The composition of the invention is substantially free of viscoelastic
fluids having both a shear stress greater than 11 kPa and a viscosity greater
than
30 cSt at 100 C. Any amount of such material that does not affect the air
release
characteristics of the composition may be present; however, it is preferred
that
the composition of the invention be totally free of such materials. The
composi-
tion of the invention is further characterized as entraining less than 1.7%
air, and
preferably less than 1.6% air, in 2 minutes and having an air release rate
greater
than 0.3%/min., preferably greater than 0.35%/min. when measured at 50 C by
ASTM D 3427. In another aspect of the invention, the lubricating composition
typically has_a TBN less than 10, a phosphorous content less than 0.08% and a
sulfur content less than 0.3% based on the total composition, and a sulfated
ash
of 1% or less.
EXAMPLES
[057] In the examples, the Group I and Group II base oils were solvent
extracted and dewaxed paraffinic hydrocarbon distillates derived from
petroleum
crude oil. The Group III base oil was an isomerate of an oil containing about
40% of slack wax. The GTL base oils were oils boiling in the tube oil ranges
that were derived from an F-T wax. The designation of Group 1,11 and III oils
refers to the categories of base oil slacks defined by the American Petroleum
Institute (API Publication 1509; wwvv.API.org). The additive package used in
the example contained a polybutenyl-succinimide dispersant, a calcium
salicylate detergent, a silicone defoamant, an ashless antioxidant, a ZDDP
antiwear agent and VI improving components.
CA 02658817 2009-01-23
WO 2008/013754 PCT/US2007/016494
- 18 -
Example 1
[058] A series of engine oils were formulated from the base oils described
above to have the same kinematic viscosity (5.2 cSt at 100 C). Each of the
oils
contained the same additive package also described above. The formulated oils
had a TBN of less than 10, a phosphorous content of less than 0.08 wt%,
calcium
less than 0.3 wt% and less than about 1.0 wt% sulfated ash.
[059] The composition of the formulated oils is given in Table I.
Table 1
Formulation, wt% Group I Group II Group III Gil
Additive Package 18.22 18.22 18.22 18.22
150 N Group I 81.78
4.5 cSt Group II 40.89
6.0 cSt Group II 40.89
5.2 cSt Group III 81.78
3.6 cSt Gil 24.53
6.0 cSt GTL 57.25
10601 Each of the formulations were evaluated for air entrainment and air
=
release at 500C using the test method ASTM D 3427.
10611 Figure 1 shows the amount of air entrained over time for each of the
base oils. The results clearly show the beneficial effect of the Gil base oil
on
air entrainment.
10621 Figure 2 shows the air release properties of each of the formulations.
These results also show the beneficial effect of the Gil base oil on air
release.
10631 The results clearly show the unexpected improvement in both the air
entrainment and air release rates obtained by the base oil derived from an F-T
wax even when compared with one derived from a slack wax.
