U.S. patent application number 11/880209 was filed with the patent office on 2008-01-31 for lubricant compositions having improved rates of air release.
Invention is credited to David J. Baillargeon, Douglas E. Deckman, Andrew G. Horodysky.
Application Number | 20080026971 11/880209 |
Document ID | / |
Family ID | 38871601 |
Filed Date | 2008-01-31 |
United States Patent
Application |
20080026971 |
Kind Code |
A1 |
Deckman; Douglas E. ; et
al. |
January 31, 2008 |
Lubricant compositions having improved rates of air release
Abstract
The air release rate of lubricating compositions is
significantly enhanced when the composition is formulated with
alkyl salicylate detergents, especially calcium or magnesium alkyl
salicylate detergents. Compositions having the improved air release
rates are 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.
Inventors: |
Deckman; Douglas E.;
(Mullica Hill, NJ) ; Horodysky; Andrew G.; (Cherry
Hill, NJ) ; Baillargeon; David J.; (Cherry Hill,
NJ) |
Correspondence
Address: |
ExxonMobil Research and Engineering Company
P. O. Box 900
Annandale
NJ
08801-0900
US
|
Family ID: |
38871601 |
Appl. No.: |
11/880209 |
Filed: |
July 20, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60833872 |
Jul 28, 2006 |
|
|
|
Current U.S.
Class: |
508/525 |
Current CPC
Class: |
C10M 2203/1006 20130101;
C10N 2030/45 20200501; C10M 159/22 20130101; C10N 2030/40 20200501;
C10M 2207/262 20130101; C10M 2223/045 20130101; C10M 2215/28
20130101; C10N 2030/52 20200501; C10N 2030/04 20130101; C10N
2030/42 20200501; C10M 2205/0206 20130101; C10M 2207/262 20130101;
C10M 2207/262 20130101; C10M 2207/262 20130101; C10N 2010/04
20130101; C10M 2223/045 20130101; C10N 2010/04 20130101; C10M
2207/262 20130101; C10N 2010/04 20130101; C10M 2223/045 20130101;
C10N 2010/04 20130101 |
Class at
Publication: |
508/525 |
International
Class: |
C10M 129/10 20060101
C10M129/10 |
Claims
1. A method for improving the air release rate of a lubricating
composition comprising a major amount of a lubricating base oil and
one or more detergents, the method comprising using as the one or
more detergents an alkyl salicylate detergent.
2. The method of claim 1 wherein the one or more alkyl salicylate
detergents are used in an amount sufficient to provide the
composition with a TBN in the range of about 4 to about 8.
3. The method of claim 2 wherein the alkyl salicylate detergent is
an alkaline earth metal alkyl salicylate.
4. The method of claim 3 wherein the alkaline earth metal is
calcium.
5. The method of claim 3 wherein the alkaline earth metal is
magnesium.
6. The method of claim 2 wherein the alkyl salicylate detergent is
an ashless nitrogen-containing detergent.
7. A lubricating composition comprising: (a) a major amount of an
oil of lubricating viscosity, (b) one or more salicylate detergents
in an amount sufficient to provide the composition with a TBN in
the range of about 4 to about 8, and (c) a minor amount of one or
more lubricant additives, the composition having less than about
0.8 wt % sulfated ash and being substantially free of a
viscoelastic fluid, said fluid having both a shear stress greater
than 11 kPa and a kinematic viscosity greater than 30 cSt at
100.degree. C.
8. The composition of claim 7 wherein the salicylate detergent is
an alkali or alkaline earth metal salt of an alkyl salicylic acid
having one or more alkyl groups of at least 8 carbon atoms.
9. The composition of claim 8 wherein the salicylate detergent is a
calcium salicylate.
10. The composition of claim 9 wherein the composition has a TBN of
from 5 to 7.
11. The composition of claim 10 wherein the calcium salicylate
detergent comprises a mixture of calcium salicylates, one having a
TBN greater than 200, a second having a TBN of about 100 to 200 and
a third having a TBN of less than 100.
12. The composition of claim 7 wherein the salicylate detergent is
an ashless salicylate detergent.
13. The composition of claims 8 and 12 wherein the composition has
a sulfur content less than about 0.25 wt % based on the total
weight of the composition.
14. A lubricating composition comprising: (a) greater than 50 wt %
of a base oil of lubricating viscosity comprising one or more oils
selected from Group II, Group III (including GTL), Group IV and
Group V base stocks; and (b) one or more detergents selected from
sulfur-free alkyl salicylate detergents in an amount to provide the
oil of lubricating viscosity with a TBN of from about 4 to about 8;
(c) one or more lubricant performance enhancing additives, the
composition having less than 0.8 wt % sulfated ash and being free
of a viscoelastic fluid having both a shear stress greater than 11
kPa and a kinematic viscosity greater than 30 cSt at 100.degree.
C.
15. The composition of claim 14 wherein the detergent is a calcium
alkyl salicylate detergent.
16. 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 the composition of any one of claims 7 to 15.
17. The use of one or more alkyl salicylate detergents to improve
the air release rate of a lubricating composition.
18. The use according to claim 17, wherein the lubricating
composition comprises at least 50 wt % of an oil of lubricating
viscosity, based on the total weight of the lubricating
composition.
19. The use according to any of claims 17 or 18, wherein the
lubricating composition comprises 1 wt % to 6 wt % alkyl salicylate
detergent, based on the total weight of the lubricating
composition.
20. The use according to any of claims 17 to 19, wherein the alkyl
salicylate detergent is an alkaline earth metal salicylate
detergent, preferably a calcium or magnesium salicylate
detergent.
21. The use according to any of claims 17 to 20, wherein the alkyl
salicylate detergent is an ashless nitrogen-containing detergent.
Description
[0001] This application claims priority of Provisional Application
60/833,872 filed Jul. 28, 2006.
FIELD OF THE INVENTION
[0002] The invention relates to lubricant compositions exhibiting
good rates of air release. More particularly, the invention relates
to lubricant compositions having low ash, sulfur and phosphorous
content and good rates of air release.
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 generally 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 modulus 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. The
rate of air release and amount of air entrainment of lubricating
compositions may be determined by the test method of ASTM D 3427.
Indeed, the rate of air release referred to herein has been
determined by that method.
[0007] 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.
[0008] Many modern gasoline and diesel engines are designed to use
the crankcase oil to function as a hydraulic fluid to operate fuel
injectors, valve train controls and the like. For these functions,
low air entrainment and rapid air release are indicative of high
performance lubricants. Indeed, it is anticipated that the rate of
air release from engine lubricants will become more critical in the
future to the proper operation of internal combustion engines as
engine designs evolve and become ever more complex.
[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.
[0010] US Patent Publication No. US 2006/0116302 describes a
detergent additive for lubricating oil compositions that comprises
at least two of low, high and medium TBN (total base number)
detergents, preferably calcium salicylate detergents. No reference
is made to the air release properties of lubricants formulated with
the mixed detergents. Indeed, the claimed benefits of the mixed
detergents related to piston cleanliness, film forming tendency and
frictional properties.
[0011] Various government and manufacturer's requirements have
created a need for lubricants that contain reduced amounts of ash,
sulfur and phosphorous. Reduced amounts of sulfur and phosphorous
in an oil are known, for example, to have a beneficial effect on
emission control catalysts in combustion engine systems.
[0012] One objective of the present invention is to provide a low
ash, sulfur and phosphorous lubricating composition that exhibits
good air release rates. Other objectives of the invention will
become apparent from the description which follows.
SUMMARY OF THE INVENTION
[0013] It has now been discovered that the rate of air release of
lubricating oil compositions can be enhanced by formulating the
composition with one or more salicylate detergents.
[0014] Thus, one aspect of the invention comprises a method for
improving the rate of air release of a lubricating composition
comprising a major amount of an oil of lubricating viscosity and a
minor amount of a detergent or mixture of detergents, the method
comprising using as the detergent or mixture of detergents one or
more salicylate detergents.
[0015] Another aspect of the invention is a lubricating composition
comprising:
[0016] (a) a major amount of an oil of lubricating viscosity,
[0017] (b) one or more salicylate detergents in an amount
sufficient to provide the lubricating composition with a TBN in the
range of about 4 to about 8, and
[0018] (c) a minor amount of one or more lubricant additives, the
composition having less than about 0.8 wt % sulfated ash content
and substantially free of a viscoelastic fluid having both a shear
stress greater than 11 kPa and a kinematic viscosity greater than
about 30 cSt at 100.degree. C.
[0019] In another aspect, lubricating oil compositions formulated
according to the invention are particularly useful as crankcase
lubricants in engines wherein the lubricant provides a lubricating
and a hydraulic function.
[0020] The foregoing summary and the following detailed description
are exemplary of the various aspects and embodiments of the claimed
invention.
BRIEF DESCRIPTION OF THE DRAWING
[0021] The accompanying sole FIGURE is a bar graph illustrating the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0022] Throughout the specification, the specific properties
referred to have been determined by the following methods:
[0023] (1) Air release rate--ASTM D 3427
[0024] (2) TBN or total base number--ASTM D 2896
[0025] (3) Kinematic viscosity at 40.degree. C. and 100.degree.
C.--ASTM D 445
[0026] (4) Viscosity index--ASTM D 2270
[0027] (5) Sulfated ash--ASTM D 874
[0028] (6) Sulfur--ASTM D 6443
[0029] (7) Phosphorous--ASTM D 4951
[0030] (8) Shear stress--measured as per SAE Paper No. 872043
[0031] For convenience, the invention will be described by
reference to engine oils such as gas, gasoline and diesel fueled
internal combustion engine oils; however, it should be appreciated
that the invention is applicable to other oils where the air
release rate is an important property. Examples of such oils
include gear oil, industrial fluids, automatic transmission fluids
and the like.
[0032] A key advantage of the present invention is that it provides
a method to enhance the air release rate of a lubricating
composition by formulating the lubricating composition with one or
more salicylate detergents.
[0033] Lubricating compositions to which the invention is
applicable are especially those comprising one or more oils of
lubricating viscosity selected from Group II, III, IV and V base
stocks. The base stock groups are defined in the American Petroleum
Institute Publication "Engine Oil Licensing and Certification
System," Fourteenth Edition, December 1966, Addendum 1, December
1998.
[0034] The base stock typically will have a viscosity of about 3 to
12, preferably 4 to 10, and more preferably 4.5 to 8 mm.sup.2/s
(cSt) at 100.degree. C.
[0035] Group II base stocks generally have a viscosity index (VI)
of between about 80 and 120 and contain 0.03 wt % sulfur or less
and 90 wt % or more saturates. Group III base stocks generally have
a VI greater than about 120, 0.03 wt % or less sulfur and 90 wt %
or more saturates. Group IV base stocks are polyalphaolefins (PAO).
Group V base stocks are all other base stocks not included in
Groups I, II, III or IV, such as esters and alkyl aromatics. A
particularly suitable Group III base stock is a gas-to-liquid (GTL)
base stock such as a base stock derived from a waxy hydrocarbon
produced in a Fischer-Tropsch (F-T) process.
[0036] 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. 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.
[0037] 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. 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.
[0038] 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. Slurry hydrocarbon synthesis process conditions vary somewhat
depending on the catalyst and desired products.
[0039] 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. 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.
[0040] 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. 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.
[0041] 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". 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.
[0042] 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.1.1..sup.-1 (56 to 19,660 SCF/bb1)
and the space velocity of the feedstock typically ranges from about
0.1 to 20 LHSV, preferably 0.1 to 10 LHSV.
[0043] 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-1 1, 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.
[0044] 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.
[0045] 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. 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.
[0046] 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.
[0047] The GTL base stock 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.
[0048] The GTL base stock 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.
A preferred GTL base stock 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.
[0049] The preferred GTL base stock 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 -3020 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.+, 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.
[0050] The preferred GTL base stock 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.
[0051] 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
[0052] A 359.88 MHz 1 H 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 ps), 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.
[0053] H atom types are defined according to the following
regions:
[0054] 9.2-6.2 ppm hydrogens on aromatic rings;
[0055] 6.2-4.0 ppm hydrogens on olefinic carbon atoms;
[0056] 4.0-2.1 ppm benzylic hydrogens at the a-position to aromatic
rings;
[0057] 2.1-1.4 ppm paraffinic CH methine hydrogens;
[0058] 1.4-1.05 ppm paraffinic CH.sub.2 methylene hydrogens;
[0059] 1.05-0.5 ppm paraffinic CH.sub.3 methyl hydrogens.
[0060] 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)
[0061] 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.
[0062] 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..about.29.8 ppm is
due to equivalent recurring methylene carbons which are four or
more removed from an end group or branch (CH.sub.2>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.
[0063] 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:
[0064] 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);
[0065] 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;
[0066] c. measure the area between 29.9 ppm and 29.6 ppm in the
sample; and
[0067] d. divide by the integral area per carbon from step b. to
obtain FCI.
[0068] 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-d1 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.
[0069] 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-1 3 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).
[0070] Suitable polyalphaolefins (PAOs) for use in compositions of
the invention comprise relatively low molecular weight hydrogenated
polymers or oligomers of alphaolefins such as C.sub.2 to C.sub.32
alphaolefins with C.sub.8 to C.sub.16 alphaolefins being
preferred.
[0071] The PAO base stocks are conveniently made by the
polymerization of alphaolefins in the presence of a polymerization
catalyst such as the Friedel-Crafts catalysts. Examples of PAO
synthesis can be found in U.S. Pat. No. 3,742,082; U.S. Pat. No.
3,769,363; U.S. Pat. No. 4,413,156; U.S. Pat. No. 4,434,408; U.S.
Pat. No. 4,910,355; and U.S. Pat. No. 4,956,122 to mention a
few.
[0072] A lubricating composition of the invention comprises a major
amount of an oil of lubricating viscosity and especially one or
more oils selected from Group II, Group III (including GTL), Group
IV and Group V base stocks. By major amount is meant greater than
50 wt %, conveniently between 75 wt % to 90 wt % and preferably
between 65 wt % to 80 wt %, based on the total weight of the
lubricating composition. When a mixture of oils is used, preferably
the mixture will comprise Group III and Group IV base stocks.
[0073] According to the present invention, the air release rate of
a lubricating composition comprising a major amount of an oil of
lubricating viscosity and a minor amount of a detergent can be
improved by using as the detergent one or more salicylate
detergents. Suitable salicylate detergents include sulfur-free
salicylate detergents, such as alkali and alkaline earth metal
salts of alkyl salicylic acid and ashless salicylate detergents
such as amides and esters of alkyl salicylic acid. Typically, the
alkylsalicylic acid will have one or more alkyl groups of at least
8 carbon atoms in the alkyl groups with 10 to 20 carbon atoms often
being preferred. In the case of ashless salicylate detergents, the
alkyl groups of the amide will have from about 2 to about 50 carbon
atoms and preferably 8 to 20 carbon atoms. The esters of alkyl
salicylic acid will be formed from alcohols having about 4 to about
20 carbon atoms and preferably 6 to 12 carbon atoms. These
detergents may be neutral or overbased or mixtures thereof. Borated
salicylate detergents may also be used.
[0074] In the invention, it is preferred that the salicylate
detergent constitutes the sole detergent in the composition.
Preferably, the detergent is an alkaline earth metal salicylate and
mixtures of calcium and magnesium salicylate or mixtures of calcium
and magnesium salicylates, especially a calcium and magnesium
salicylate.
[0075] In one embodiment of the invention, three salicylate
detergents are used, each with a different total base number (TBN).
One detergent will have a TBN greater than 200; a second will have
a TBN of about 100 to 200; and a third, a TBN of less than about
100. For example, in an especially preferred embodiment, the
detergent comprises three calcium salicylate detergents, one with a
270 TBN, another with a 170 TBN and yet another with a 70 TBN. On
an active ingredient basis, the composition according to this
preferred embodiment would comprise each of the detergents in an
amount of about 0.1 wt % to about 2 wt %, based on the total weight
of the lubricating composition.
[0076] In the compositions of the invention, the salicylate
detergent(s) will typically be used in an amount sufficient to
provide the composition with a TBN in the range of about 4 to 8 and
preferably about 5 to 7. Conveniently, on an active ingredient
basis, the composition will comprise about 1 wt % to about 6 wt %
and preferably 1 wt % to 3 wt % salicylate detergent(s) based on
the total weight of the composition.
[0077] The instant invention can be used with additional lubricant
components in effective amounts typically used in lubricant
compositions such as alkyl-aromatic lubricant oils, and performance
additives such as, for example but not limited to, oxidation
inhibitors, corrosion and rust inhibitors, metal deactivators,
antiwear agents, extreme pressure additives, pour point
depressants, wax modifiers, viscosity modifiers, lubricating
agents, defoamants, demulsifiers and others.
[0078] Examples of suitable antioxidants include aminic
antioxidants and phenolic antioxidants. Typical aminic antioxidants
include alkylated aromatic amines, especially those in which the
alkyl group contains no more than 14 carbon atoms. 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. Mixtures of phenolic and
aminic antioxidants also may be used. Such additives may be used in
an amount of about 0.02 to 5 wt %, and preferably about 0.1 wt % to
about 2 wt % based on the total weight of the composition.
[0079] Rust inhibitors selected from the group consisting of
nonionic polyoxyalkylene polyols and esters thereof,
polyoxyalkylene phenols, and aminic alkyl sulfonic acids may be
used. Corrosion inhibitors that may be used include benzotriazoles,
tolyltriazoles and their derivatives.
[0080] Suitable dispersants include succinimide dispersants, ester
dispersants, ester-amide 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 4000 or more and preferably from
about 1300 to about 2500. The dispersant may be head capped or
borated or both.
[0081] A commonly used class of antiwear additives is zinc
dialkyldithio-phosphates in which the alkyl groups typically have
from 3 to about 18 carbon atoms with 3 to 10 carbon atoms being
preferred. Suitable antifoam additives include silicone oils or
polysiloxane oils usually used in amounts of from 0.0001 to 0.01 wt
% active ingredient. Pour point depressants are well known
lubricant additives. Typical examples are dialkylfumarates,
polyalkylmethacrylates, and the like. The number and types of
friction modifiers are voluminous. In general, they include metal
salts of fatty acids, glycerol esters and alkoxylated fatty amines
to mention a few.
[0082] Another additive often used in crankcase lubricants is a VI
improver such as linear or radial styrene-isoprene VI improvers,
olefin copolymers, polymethacrylates, and the like. In general, on
an active ingredient basis, the various lubricant additives will
comprise 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 except where otherwise specified herein. The
composition of the invention is substantially free of added
viscoelastic fluids that have both a shear stress greater than 11
kPa and a kinematic viscosity greater than 30 cSt at 100.degree. C.
Any amount of such material that does not affect the air release
rate of the composition may be present; however, it is preferred
that the composition be totally free of such material.
EXAMPLES
[0083] A series of multigrade, internal combustion, engine oils
were prepared according to the formulations show in Table 1, in
which PAO 6 is a polyalphaolefin basestock with a KV at 100.degree.
C. of 5.8 cSt. Different detergents were used in quantities
providing engine oils with a TBN of 7. Each of the blends contained
the same polybutenylsuccinimide dispersant zinc
dialkyldithiophosphate antiwear additive, ashless antioxidant,
silicone defoamant, friction modifier and VI improving compounds in
the same amounts (i.e., 15.47 wt % of the total composition).
Additionally, a reference blend without detergent, but containing
all other additives in the same amounts was prepared. All of the
blends were tested for air release rate according to ASTM D 3427.
The results are shown graphically in the accompanying figure. As
can be seen, salicylate detergents provide a significant
performance benefit by quickly releasing entrained air.
TABLE-US-00001 TABLE 1 Common Additives 15.47 15.47 15.47 15.47
15.47 PAO 6 Basestock 84.53 81.03 81.71 82.17 82.81 P5090
Salicylate detergent 0 3.5 0 0 0 Calcium Phenate 0 0 2.82 0 0 Ca
sulfonate 0 0 0 2.36 0 Mg sulfonate 0 0 0 0 1.72
[0084] All US patents, applications and non-patent references cited
in this application are hereby incorporated in their entirety by
reference.
* * * * *