U.S. patent application number 11/880194 was filed with the patent office on 2008-01-31 for lubricant compositions, their preparation and use.
Invention is credited to David J. Baillargeon, Douglas E. Deckman, Andrew G. Horodysky.
Application Number | 20080026968 11/880194 |
Document ID | / |
Family ID | 38981996 |
Filed Date | 2008-01-31 |
United States Patent
Application |
20080026968 |
Kind Code |
A1 |
Deckman; Douglas E. ; et
al. |
January 31, 2008 |
Lubricant compositions, their preparation and use
Abstract
A lubricating composition that has improved air release
characteristics is based on a lubricating base oil comprising an
oil or mixture of oils derived from waxy hydrocarbons produced in
an F-T synthesis process. The composition is substantially free of
a viscoelastic fluid having a shear stress greater than 11 kPa and
a viscosity greater than 30 cSt at 100.degree. C. It is further
characterized as entraining less than 1.7% air in 2 minutes and
having an air release rate greater than 0.3%/min. when measured at
50.degree. C. by ASTM D 3427.
Inventors: |
Deckman; Douglas E.;
(Mullica Hill, NJ) ; Baillargeon; David J.;
(Cherry Hill, NJ) ; Horodysky; Andrew G.; (Cherry
Hill, NJ) |
Correspondence
Address: |
ExxonMobil Research and Engineering Company
P. O. Box 900
Annandale
NJ
08801-0900
US
|
Family ID: |
38981996 |
Appl. No.: |
11/880194 |
Filed: |
July 20, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60833871 |
Jul 28, 2006 |
|
|
|
Current U.S.
Class: |
508/459 |
Current CPC
Class: |
C10M 2205/173 20130101;
C10N 2030/40 20200501; C10M 169/04 20130101; C10N 2030/42 20200501;
C10M 2215/28 20130101; C10M 2207/262 20130101; C10N 2030/45
20200501; C10M 2229/02 20130101; C10N 2030/52 20200501; C10M
2223/045 20130101; C10N 2030/02 20130101; C10N 2040/08 20130101;
C10N 2040/25 20130101; C10M 2207/262 20130101; C10N 2010/04
20130101; C10M 2207/262 20130101; C10N 2010/04 20130101 |
Class at
Publication: |
508/459 |
International
Class: |
C10M 159/06 20060101
C10M159/06; C10M 105/32 20060101 C10M105/32 |
Claims
1. 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 additive, the method
comprising using as the base oil an effective amount of one or more
oils derived from a waxy hydrocarbon produced in an F-T
process.
2. The method of claim 1 wherein the base oil has a kinematic
viscosity in the range of 2 mm.sup.2/s to about 50 mm.sup.2/s at
100.degree. C.
3. The method of claim 2 wherein the oil has a VI in the range of
130 to 140 or more.
4. A lubricating composition comprising: a major amount of a
lubricating 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, the composition being
substantially free of viscoelastic fluids having both a shear
stress greater than 11 kPa and a viscosity greater than 30 cSt at
100.degree. C. and further characterized as entraining less than
1.7%/min. air and having an initial air release rate greater than
0.3%/min. when measured at 50.degree. C. by ASTM D 3427.
5. The composition of claim 4 wherein the base oil has a viscosity
of 2 to 50 mm.sup.2/s at 100.degree. C.
6. The composition of claim 5 wherein the base oil has a VI in the
range of 130 to 140 or more.
7. The composition of claim 6 including a plurality of
additives.
8. The composition of claim 7 wherein the additives include one or
more of alkaline earth metal detergents, ashless dispersants,
antioxidants, antiwear agents, pour point depressants and VI
improvers.
9. The composition of claim 8 wherein the composition has a TBN
less than 10, a phosphorous content less than 0.08 wt % and calcium
content less than 0.3 wt %, each based on the total weight of the
composition and a sulfated ash of 1% or less.
10. The composition of claim 8 wherein the additives comprise, on
an active ingredient basis, from 0.5 wt % to 25 wt % based on the
total weight of the composition.
11. The composition of claim 10 wherein the additives comprise from
2 wt % to 10 wt % of the composition.
12. In the lubrication of an engine with a crankcase lubricant
wherein the lubricant additionally is used to perform a hydraulic
function, the improvement comprising using as the crankcase
lubricant a lubricating composition according to claims 4 to
11.
13. A method for formulating an engine oil lubricant having an air
entrainment of less than 1.7% in 2 minutes and an air release rate
greater than 0.3%/min. when measured at 50.degree. C. by ASTM D
3427 without adding to the formulation a viscoelastic fluid having
a shear rate greater than 1 kPa and a viscosity greater than 30 cSt
at 100.degree. C., the method comprising blending a major amount of
a base oil consisting essentially of an oil or mixture of oils
derived from waxy hydrocarbons produced in an F-T process with one
or more engine oil additives.
14. The use of one or more oils derived from a waxy hydrocarbon
produced in an F-T process to improve the air release
characteristics of a lubricating composition.
15. The use according to claim 14, wherein the one or more oils
derived from a waxy hydrocarbon produced in an F-T process is used
in an amount of at least 50 wt % based on the total weight of the
lubricating composition.
16. The use according to any of claims 14 or 15, wherein the one or
more oils derived from a waxy hydrocarbon produced in an F-T
process have a kinematic viscosity in the range of 2 mm.sup.2/s to
50 mm.sup.2/s at 100.degree. C.
17. The use according to any of claims 14 to 16, wherein the one or
more oils derived from a waxy hydrocarbon produced in an F-T
process have a VI in the range of 130 to 140 or more.
18. The use according to any of claims 14 to 17, wherein the
lubricating composition has an air entrainment of less than 1.7% in
2 minutes and an air release rate greater than 0.3%/min. when
measured at 50.degree. C. by ASTM D 3427 without adding to the
formulation a viscoelastic fluid having a shear rate greater than 1
kPa and a viscosity greater than 30 cSt at 100.degree. C.
Description
[0001] This application claims priority of Provisional Application
60/833,871 filed Jul. 28, 2006.
FIELD OF THE INVENTION
[0002] The present invention relates to lubricant compositions with
good air release characteristics, their preparation and use.
BACKGROUND OF THE INVENTION
[0003] 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.
[0004] 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.
[0005] Air entrainment and foaming in lubricating compositions are
undesirable 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.
[0006] Air entrainment, however, is more problematic than foaming.
Foaming is typically depressed in lubricating compositions by the
use of antifoamant 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.
[0007] 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.
[0008] U.S. Pat. No. 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.
[0009] U.S. Pat. No. 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
[0010] 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.
[0011] 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.
[0012] 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 kPa
and a viscosity greater than 30 cSt at 100.degree. 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 50.degree. C.
by ASTM Test Method D 3427.
[0013] 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.
[0014] 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
[0015] FIGS. 1 and 2 are graphical representations showing the
improvement in air release characteristics achieved by the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0016] Throughout the specification the specific properties
referred to have been determined by the following method:
(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.
[0017] 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.
[0018] 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.
[0019] As is known to those skilled in the art, in an F-T synthesis
process, a synthesis gas comprising a mixture of H.sub.2 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.
[0020] 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
H.sub.2 to CO is typically about 2.1/1.
[0021] The synthesis gas comprising a mixture of H.sub.2 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 hydrocarbons, 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.
[0022] Slurry hydrocarbon synthesis process conditions vary
somewhat depending on the catalyst and desired products. Typical
conditions effective to form hydrocarbons comprising mostly
C.sub.5+ paraffins, (e.g., C.sub.5+-C.sub.200) and preferably
C.sub.10+ 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.degree. F., 80-600
psi and 100-40,000 V/hr/V, expressed as standard volumes of the
gaseous CO and H.sub.2 mixture (0.degree. C., 1 atm) per hour per
volume of catalyst, respectively. The term "C.sub.5+" 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.
[0023] 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 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.
[0024] 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 650.degree. F. to 750.degree. F. and preferably boils
up to an end point of at least 1050.degree. F.
[0025] 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.
[0026] The waxy feed preferably comprises the entire
650-750.degree. F.+ fraction formed by the hydrocarbon synthesis
process, having an initial cut point between 650.degree. F. and
750.degree. F. determined by the practitioner and an end point,
preferably above 1050.degree. F., determined by the catalyst and
process variables employed by the practitioner for the synthesis.
Such fractions are referred to herein as "650-750.degree. F.+
fractions".
[0027] By contrast, "650-750.degree. F.- fractions" refers to a
fraction with an unspecified initial cut point and an end point
somewhere between 650.degree. F. and 750.degree. 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.
[0028] 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 6000 kPa. The ratio of hydrogen
to the hydrocarbon feedstock (hydrogen circulation rate) typically
range from about 10 to 3500 n.l.l..sup.-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.
[0029] 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 U.S. Pat. No. 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.
[0030] 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 U.S. Pat. No. 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.
[0031] A dewaxing step, when needed, may be accomplished using
either well known solvent or catalytic dewaxing processes and
either the entire hydroisomerate or the 650-750.degree. F.+
fraction may be dewaxed, depending on the intended use of the
650-750.degree. 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 MEK/MIBK, 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.
[0032] 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.degree. F.-, which are separated from the heavier
650-750.degree. 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.degree. F.+ material into the desired
base stocks.
[0033] 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 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.degree. F., a pressure of 500-900
psig, H.sub.2 treat rate of 1500-3500 SCF/B for flow-through
reactors and LHSV of 0.1-10, preferably 0.2-2.0. 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.degree. F. to material
boiling below its initial boiling point.
[0034] The base oil suitable for use in the invention will have a
kinematic viscosity in the range of about 2 to 50 mm.sup.2/s at
100.degree. C. and preferably in the range of about 3.5 to 30
mm.sup.2/s at 100.degree. C. and a VI greater than about 130,
preferably greater than 135 and more preferably 140 or greater.
[0035] The base oil of the invention is further characterized as
having a pour point of -5.degree. C. or lower, preferably about
-10.degree. C. or lower and under some conditions advantageously
having pour points of about -25.degree. C. to about -40.degree.
C.
[0036] 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 (CH.sub.2.gtoreq.4), are such that: (a)
BI-0.5(CH.sub.2.gtoreq.4)>15; and (b)
BI+0.85(CH.sub.2.gtoreq.4)<45 as measured over said liquid
hydrocarbon composition as a whole.
[0037] The preferred base oil can be further characterized, if
necessary, as having less than 0.1 wt % aromatic hydrocarbons, less
than 20 wppm nitrogen containing compounds, less than 20 wppm
sulfur containing compounds, a pour point of less than -18.degree.
C., preferably less than -30.degree. C., a preferred BI.gtoreq.25.4
and (CH.sub.2.gtoreq.4).ltoreq.22.5. They have a nominal boiling
point of 370.degree. C..sup.+, 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.degree. C., and kinematic viscosity, as
measured at 100.degree. C. represented by the formula: DV (at
-40.degree. C.)<2900 (KV @ 100.degree. C.)-7000.
[0038] 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 C.sub.20 to about C.sub.40, a molecular weight of
about 280 to about 562, a boiling range of about 650.degree. F. to
about 1050.degree. 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.
[0039] In the above the Branching Index (BI), Branching Proximity
(CH.sub.2.gtoreq.4), and Free Carbon Index (FCI) are determined as
follows:
Branching Index
[0040] A 359.88 MHz 1H solution NMR spectrum is obtained on a
Bruker 360 MHz AMX spectrometer using 10% solutions in CDCl.sub.3.
TMS is the internal chemical shift reference. CDCl.sub.3 solvent
gives a peak located at 7.28. All spectra are obtained under
quantitative conditions using 90 degree pulse (10.9 .mu.s), a pulse
delay time of 30 s, which is at least five times the longest
hydrogen spin-lattice relaxation time (T.sub.1), and 120 scans to
ensure good signal-to-noise ratios.
[0041] H atom types are defined according to the following regions:
[0042] 9.2-6.2 ppm hydrogens on aromatic rings; [0043] 6.2-4.0 ppm
hydrogens on olefinic carbon atoms; [0044] 4.0-2.1 ppm benzylic
hydrogens at the a-position to aromatic rings; [0045] 2.1-1.4 ppm
paraffinic CH methine hydrogens; [0046] 1.4-1.05 ppm paraffinic
CH.sub.2 methylene hydrogens; [0047] 1.05-0.5 ppm paraffinic
CH.sub.3 methyl hydrogens.
[0048] The branching index (BI) 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 (CH.sub.2.gtoreq.4)
[0049] A 90.5 MHz.sup.3CMR single pulse and 135 Distortionless
Enhancement by Polarization Transfer (DEPT) NMR spectra are
obtained on a Brucker 360 MHzAMX spectrometer using 10% solutions
in CDCL.sub.3. TMS is the internal chemical shift reference.
CDCL.sub.3 solvent gives a triplet located at 77.23 ppm in the
.sup.13C spectrum. All single pulse spectra are obtained under
quantitative conditions using 45 degree pulses (6.3 .mu.s), a pulse
delay time of 60 s, which is at least five times the longest carbon
spin-lattice relaxation time (T.sub.1), to ensure complete
relaxation of the sample, 200 scans to ensure good signal-to-noise
ratios, and WALTZ-16 proton decoupling.
[0050] The C atom types CH.sub.3, CH.sub.2, and CH are identified
from the 135 DEPT .sup.13C NMR experiment. A major CH.sub.2
resonance in all .sup.13C NMR spectra at .sup.{tilde over ( )}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 .sup.13C chemical
shifts for the methyl carbon at the end of the branch or the
methylene carbon one removed from the methyl on the branch.
[0051] 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:
[0052] 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 CH.sub.2);
[0053] 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;
[0054] c. measure the area between 29.9 ppm and 29.6 ppm in the
sample; and
[0055] d. divide by the integral area per carbon from step b. to
obtain FCI.
[0056] Branching measurements can be performed using any Fourier
Transform NMR spectrometer. Preferably, the measurements are
performed using a spectrometer having a magnet of 7.0 T 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-dl were excited by 45 degrees pulses followed by a 0.8
sec 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.
[0057] 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 CH.sub.3 up and CH.sub.2 180 degrees
out of phase (down). APT is Attached Proton Test. It allows all
carbons to be seen, but if CH and CH.sub.3 are up, then
quaternaries and CH.sub.2 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 determined by C-13 NMR
using the assumption in the calculations that the entire sample is
isoparaffinic. Corrections are not made for n-paraffins or
cycloparaffins, which may be present in the oil samples in varying
amounts. The cycloparaffins content is measured using Field
Ionization Mass Spectroscopy (FIMS).
[0058] 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 %.
[0059] The base oil suitable for the composition is that described
in detail above.
[0060] 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.
[0061] 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.
[0062] 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.
[0063] 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.
[0064] 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
alkylated 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 %.
[0065] 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.
[0066] 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 preferably from about 2 wt % to about 10
wt % based on the total weight of the composition.
[0067] 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.degree. 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 composition 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.degree. 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
[0068] 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 lube oil ranges that were derived
from an F-T wax. The designation of Group I, II and III oils refers
to the categories of base oil slacks defined by the American
Petroleum Institute (API Publication 1509; www.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.
Example 1
[0069] A series of engine oils were formulated from the base oils
described above to have the same kinematic viscosity (5.2 cSt at
100.degree. 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.
[0070] The composition of the formulated oils is given in Table
1.
TABLE-US-00001 TABLE 1 Formulation, wt % Group I Group II Group III
GTL 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 GTL 24.53 6.0 cSt GTL 57.25
[0071] Each of the formulations were evaluated for air entrainment
and air release at 50.degree. C. using the test method ASTM D
3427.
[0072] FIG. 1 shows the amount of air entrained over time for each
of the base oils. The results clearly show the beneficial effect of
the GTL base oil on air entrainment.
[0073] FIG. 2 shows the air release properties of each of the
formulations. These results also show the beneficial effect of the
GTL base oil on air release.
[0074] 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.
* * * * *
References