U.S. patent application number 13/935806 was filed with the patent office on 2013-11-07 for lubricating oil with improved wear properties.
This patent application is currently assigned to CHEVRON U.S.A. INC.. The applicant listed for this patent is James BOOTH, James McGEEHAN, Trevor MILLER, Willem VAN DAM. Invention is credited to James BOOTH, James McGEEHAN, Trevor MILLER, Willem VAN DAM.
Application Number | 20130296202 13/935806 |
Document ID | / |
Family ID | 49512983 |
Filed Date | 2013-11-07 |
United States Patent
Application |
20130296202 |
Kind Code |
A1 |
VAN DAM; Willem ; et
al. |
November 7, 2013 |
LUBRICATING OIL WITH IMPROVED WEAR PROPERTIES
Abstract
Provided is a lubricating oil composition for internal
combustion engines comprising at least one hydrocarbon base stock
which is determined to exhibit a 100.degree. C. PVC/40.degree. C.
PVC ratio approaching one or greater, and one or more lubricating
additives. Also provided is a method for preparing such a
composition, which includes determining the 100.degree. C.
PVC/40.degree. C. PVC ratio of a hydrocarbon base stock oil, and
selecting a hydrocarbon base stock oil which exhibits a 100.degree.
C. PVC/40.degree. C. PVC ratio approaching one. One or more
lubricating additives are then added to the selected base stock
oil.
Inventors: |
VAN DAM; Willem; (Novato,
CA) ; McGEEHAN; James; (San Rafael, CA) ;
MILLER; Trevor; (Dublin, CA) ; BOOTH; James;
(Napa, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
VAN DAM; Willem
McGEEHAN; James
MILLER; Trevor
BOOTH; James |
Novato
San Rafael
Dublin
Napa |
CA
CA
CA
CA |
US
US
US
US |
|
|
Assignee: |
CHEVRON U.S.A. INC.
San Ramon
CA
|
Family ID: |
49512983 |
Appl. No.: |
13/935806 |
Filed: |
July 5, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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12974706 |
Dec 21, 2010 |
|
|
|
13935806 |
|
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Current U.S.
Class: |
508/110 |
Current CPC
Class: |
C10M 171/02 20130101;
C10N 2040/255 20200501; C10N 2040/252 20200501; C10M 2203/1025
20130101; C10M 2205/173 20130101; C10M 171/00 20130101; C10N
2070/00 20130101; C10M 2205/0285 20130101; C10N 2030/02 20130101;
C10N 2030/06 20130101; C10N 2040/25 20130101; C10N 2020/02
20130101 |
Class at
Publication: |
508/110 |
International
Class: |
C10M 171/02 20060101
C10M171/02 |
Claims
1. A lubricating oil composition for internal combustion engines
comprising: a) at least one hydrocarbon base stock which is
selected once it is determined to exhibit a 100.degree. C.
PVC/40.degree. C. PVC ratio approaching one or greater; and b) one
or more lubricating additives.
2. The composition of claim 1, wherein the at least one hydrocarbon
base stock is blended with a minor amount of a different base
stock.
3. The composition of claim 2, wherein the different base stock is
a Fischer-Tropsch derived base oil.
4. The composition of claim 1, wherein the at least one hydrocarbon
base stock which is selected is a Fischer-Tropsch derived base
oil.
5. The composition of claim 1, wherein the ratio is at least
0.85.
6. The composition of claim 1, wherein the ratio is at least
0.90.
7. The composition of claim 1, wherein the ratio is at least
0.95.
8. The composition of claim 3, wherein the Fischer-Tropsch derived
base oil blended with the hydrocarbon base stock exhibits a
kinematic viscosity at 100.degree. C. of at least 7
mm.sup.2/sec.
9. The composition of claim 3, wherein the Fischer-Tropsch derived
base oil blended with the hydrocarbon base stock exhibits a
kinematic viscosity at 100.degree. C. of at least 10
mm.sup.2/sec.
10. The composition of claim 1, wherein the at least one
hydrocarbon base stock exhibits a kinematic viscosity at
100.degree. C. in the range of from 3 to 12 mm.sup.2/sec.
11. The composition of claim 1, wherein the at least one
hydrocarbon base stock exhibits a kinematic viscosity at
100.degree. C. in the range of from 4 to 10 mm.sup.2/sec.
12. The composition of claim 1, wherein the composition contains no
viscosity modifier.
13. The composition of claim 1, wherein the composition contains
one or more detergents.
14. The composition of claim 1, wherein the composition contains
one or more dispersants.
15. The composition of claim 1, wherein the composition contains
one or more anti-oxidants.
16. The lubricating oil composition of claim 1, wherein the
composition further comprises one or more conventional base oils,
and wherein the conventional base oil is a maximum of 30 weight
percent based on the total weight of the lubricating oil
composition.
17. The composition of claim 1, wherein the 100.degree. C.
PVC/40.degree. C. PVC ratio is in the range of from 0.85 to 1.05
when measured at both 20N and 50N.
18. A method for lubricating an internal combustion engine and
reducing a wear comprising lubricating the internal combustion
engine with the lubricating oil composition of claim 1.
19. A method for lubricating an internal combustion engine and
reducing a wear comprising lubricating the internal combustion
engine with the lubricating oil composition of claim 3.
20. A method for preparing the lubricating oil composition of claim
1, comprising: a) determining a 100.degree. C. PVC/40.degree. C.
PVC ratio of a hydrocarbon base stock oil; b) selecting a
hydrocarbon base stock oil once it is determined to have the
100.degree. C. PVC/40.degree. C. PVC ratio approaching one; and c)
adding one or more lubricating additives.
21. The method of claim 20, further comprising blending the
hydrocarbon base stock oil of b) with a Fischer-Tropsch derived
base oil.
22. The method of claim 20, wherein the hydrocarbon base stock oil
is a Fischer-Tropsch derived base oil.
23. The method of claim 20, wherein the hydrocarbon base stock oil
has the ratio of at least 0.85.
24. The method of claim 20, wherein the hydrocarbon base stock oil
has the ratio of at least 0.90.
25. The method of claim 20, wherein the hydrocarbon base stock oil
has the ratio of at least 0.95.
26. The method of claim 20, wherein the ratio of 100.degree. C.
PVC/40.degree. C. PVC is measured at both 20N and 50N, and the
hydrocarbon base stock oil selected is one that exhibits the ratio
of 100.degree. C. PVC/40.degree. C. PVC in the range of 0.85 to
1.05 when measured at both 20N and 50N.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation-in-part of U.S.
application Ser. No. 12/974,706, filed Dec. 21, 2010, to which
application priority is claimed and which application is
incorporated by reference herein in its entirety.
TECHNICAL FIELD
[0002] The present invention relates to a lubricating oil
composition having improved wear properties, and in particular
valve train wear properties. More particularly, the present
invention employs base stocks exhibiting low temperature
sensitivity of the Pressure-Viscosity-Coefficient (PVC) to obtain
improved wear properties.
BACKGROUND
[0003] Lubricating oils for internal combustion engines contain one
or more additives in addition to at least one base lubricating oil.
Lubricating oils are used to perform the critical function of
lubricating moving parts in the internal combustion engine.
Lubricating oils perform this function by maintaining a
sufficiently high lubricating film thickness on metal surfaces in
order to maintain low friction and reduce wear of the metal parts.
Reduction in friction ultimately results in improved fuel economy
and enhanced mechanical efficiency.
[0004] Reduction in friction can be accomplished by reducing the
viscosity of the lubricating oil. While this approach works well at
higher contact speeds, it may increase wear at lower contact speeds
if a sufficiently thick lubricating oil cannot be maintained.
Conventional lubricating oils rely on friction reducing agents,
such as surface active friction modifiers, for protecting the metal
surfaces at these lower contact speeds.
[0005] Fischer-Tropsch derived base oils have been blended to make
lubricating oils. See, US 2008/0128322; US 2006/0027486; US
2006/0070914; US 2006/0076266; US 2006/0076227; US 2007/0049507; US
2006/0172898; US 2004/0235682; and U.S. Pat. Nos. 7,195,706 and
7,141,157. Some of the blends comprise two or more Fischer-Tropsch
derived base oils. Additives have also been used in the blends to
enhance certain targeted properties. Specifications throughout the
world are continually getting more stringent, making it more
difficult to meet the specification.
[0006] In evaluation, lubricants for internal combustion engines
have to deal with many contradicting requirements. Those
requirements come in the form of limits for performance parameters
measured in engine and bench tests as well as physical and chemical
requirements. Typically included in those lubricant specifications
are engine tests evaluating the lubricant's capability in
protecting the engine's valve train from wear. Wear protection is
traditionally obtained from anti-wear additives, such as ZnDTP and
other surface active materials. Another approach used to obtain
wear protection is to increase the viscosity of the lubricant by
going to higher viscosity grade lubricants, which increases the
separation between the valve train components. The industry is
constantly searching, however, for improved ways to obtain wear
protection for internal combustion engines. Improved wear
protection in a more economic and simple manner would be of great
benefit of the industry.
SUMMARY
[0007] Provided is a lubricating oil composition for internal
combustion engines which provides improved wear protection for
valve train components through the selection of a base stock having
specific temperature sensitivity characteristics. The lubricating
oil composition comprises at least one hydrocarbon base stock which
is selected due to it exhibiting a 100.degree. C. PVC/40.degree. C.
PVC ratio approaching one or greater, and one or more lubricating
additives. Also provided are methods for lubricating an internal
combustion engine with the lubricating oil composition. Also
provided is a method for preparing such a lubricating oil
composition, which includes determining the 100.degree. C.
PVC/40.degree. C. PVC ratio of a hydrocarbon base stock oil, and
selecting a hydrocarbon base stock oil which exhibits a 100.degree.
C. PVC/40.degree. C. PVC ratio approaching one. One or more
lubricating additives are then added to the selected base stock
oil.
[0008] Among other factors, the present lubricating oil composition
and method for preparing same is based on the discovery of a
relationship between temperature sensitivity of the
Pressure-Viscosity-Coefficient (PVC) of a base stock and the wear
properties exhibited by that base stock. Thus, by determining the
temperature sensitivity of the PVC of a base stock and selecting a
hydrocarbon base stock with a 100.degree. C./40.degree. C. ratio
approaching one or greater for a lubricating oil composition, the
wear properties of the lubricating oil composition are improved.
The need for additional additives is reduced and the need for
higher viscosity grade lubricants is avoided. In one embodiment,
lower viscosity hydrocarbon base stock oil can be used in the
present lubricating oil composition, while still exhibiting
excellent cam wear properties.
BRIEF DESCRIPTION OF THE FIGURE OF THE DRAWINGS
[0009] FIGURE, graphically displays the pressure viscosity
coefficient versus temperature for a number of base oils.
DETAILED DESCRIPTION
[0010] The present lubricant composition provides greatly improved
valve train wear control due to the selection of base stocks with
specific temperature sensitivity characteristics. The base stocks
of choice exhibit less temperature sensitivity of the
Pressure-Viscosity-Coefficient (PVC) than conventionally used base
stocks, thus minimizing the reduction of contact film thickness
with increasing temperature, relative to `typical` base oils. Such
base stocks have been found to exhibit higher PVC at the
temperature levels experienced in the valve train's wear contacts
of an internal combustion engine. Hydrocarbon base stocks with
higher PVC behave more solid-like under extremely high contact
pressures, greater than 0.5 GPa. By measuring the PVC of a base
stock at 100.degree. C. and 40.degree. C., the temperature
sensitivity of the PVC can be determined by the ratio of
100.degree. C. PVC/40.degree. C. PVC. As this ratio approaches
1.00, the base stock PVC is less sensitive to the temperature. Base
stocks showing this behavior have been found to provide improved
wear protection. Such base stocks can cover a broad range of
viscosity indices (VI), indicating that the characteristic of
interest is not necessarily correlated with VI or any of its
associated parameters such as the viscosity index improver (VII)
content or the lubricant's VII dosage related shear behavior.
[0011] The PVC of a base stock can be determined using a
calculation procedure as follows: [0012] Measure the
elastohydrodynamic (EHL) film thickness of the samples and the
reference oil, e.g., Squalane, at desired temperatures, i.e.,
100.degree. C. and 40.degree. C. [0013] Calculate the PVC values by
applying the following equation:
[0013] .alpha.S=.alpha.R[(hS/hR)(.eta.S/.eta.R)-0.67]1/0.53
[0014] The subscripts S and R refer to the samples and the
reference oil, respectively; .alpha. is the PVC value; h the film
thickness, and .eta. the dynamic viscosity.
[0015] The h values are measured on an EHL system, the viscosity
.eta. data can be measured or obtained by a provider of the base
stock. The parameter values .alpha. and .eta. of the reference oil,
Squalane, are available in the literature.
[0016] The EHL film thickness is measured on an EHL Ultra Thin Film
Measurement System, a computer controlled instrument for measuring
the film thickness and traction coefficient (friction coefficient)
of lubricants in the EHL lubricating regime. The instrument can
measure lubricant film thickness down to 1 nm with a precision of
+/-1 nm. Traction coefficient can be measured at any slide/roll
ratio from pure rolling up to 100%. The instrument measures these
lubricant properties in the contact formed between a steel ball and
a rotating glass or steel disk. The contact pressures and shear
rates in this contact are similar to those found in for example,
gears, rolling element bearings and cams.
[0017] Once the PVC ratio is determined, a base stock having a
ratio approaching one is selected. The 100.degree. C.
PVC/40.degree. C. PVC ratio is generally at least 0.85, e.g., in
the range of from 0.85 to 1.05. In another embodiment, the ratio is
at least 0.90, e.g., in the range of from 0.09 to 1.05; and the
ratio in another embodiment is at least 0.95, e.g., in the range of
from 0.95 to 1.05. The PVC measurements can be performed at 20N or
50N (corresponding to a Hertzian pressure of about 0.5 and 0.7 GPa,
respectively), which values have not generally been found to change
the results of the determination. Suitable additives can then be
added to the selected base stock oil to obtain the lubricating oil
composition.
[0018] The base stock can be any suitable base stock oil as long as
it exhibits a 100.degree. C. PVC/40.degree. C. PVC ratio
approaching one, e.g., at least 0.85. The base stock can be any
base stock, such as mineral oil, synthetic base oil, or
Fischer-Tropsch derived base oil (FTBO). The viscosity of the base
stock oil also can vary greatly, as long as the ratio is met, e.g.,
a kinematic viscosity at 100.degree. C. of 4 mm.sup.2/sec or higher
can be used. The selected base stock oil can be used alone, or in a
mixture with other base stock oils meeting the PVC ratio
requirement.
[0019] The selected base stock oil or oils can be used alone to
formulate the lubricating oil composition, or can be blended with
other base stocks not meeting the PVC ratio requirement. Generally,
the selected base stock, if blended, is blended with a minor
amount, i.e., less than 50 wt %, of a different base stock oil not
meeting the PVC ratio requirement. The blending component can
comprise any suitable base stock oil, with good results being
achieved with Fischer-Tropsch derived base oils. The mixing
component can exhibit any suitable viscosity as well, e.g., at
least 7 mm.sup.2/sec, or at least 10 mm.sup.2/sec. In one
embodiment, the lubricating oil composition further comprises one
or more conventional base oils. When conventional base oils are
mixed with the selected base stock oil, the amount blended will
generally be a maximum of 30 wt %, or even 10 wt %, based on the
total weight of the lubricating oil composition. Conventional base
oils in the context of this disclosure include any hydrocarbon base
stocks that exhibit a 100.degree. C. PVC/40.degree. C. PVC ratio
when measured at 20N and 50N less than 0.85. Examples of
conventional base oils include mineral oil derived base oils as
well as synthetic oils, including synthetic esters and polyalpha
olefins (PAOs).
[0020] The base stock or blend of base stocks used in the
lubricating oil composition will generally exhibit a kinematic
viscosity at 100.degree. C. in the range of from 3 to 12
mm.sup.2/sec, and more likely in the range of from 4 to 10
mm.sup.2/sec. Various additives can be added to adjust the
viscosity if desired.
[0021] In preparing the present lubricating oil composition,
therefore, one first determines the 100.degree. C. PVC/40.degree.
C. PVC ratio of a hydrocarbon base stock. Then a hydrocarbon base
stock is selected which has been determined to have a 100.degree.
C. PVC/40.degree. C. PVC ratio approaching one, e.g., at least
0.85. This can be mixed with other such base stock oils, or blended
with a minor amount, i.e., less than 50 wt %, of base stock oil,
conventional, FTBO, etc., which does not meet the PVC ratio.
Suitable lubricating additives can be added to prepare the final
lubricating oil composition.
[0022] Fischer-Tropsch derived base oils are well known. In Fischer
Tropsch chemistry, syngas is converted to liquid hydrocarbons by
contact with a Fischer Tropsch catalyst under reactive conditions.
Typically, methane and optionally heavier hydrocarbons (ethane and
heavier) can be sent through a conventional syngas generator to
provide synthesis gas. Generally, synthesis gas contains hydrogen
and carbon monoxide, and may include minor amounts of carbon
dioxide and/or water. The presence of sulfur, nitrogen, halogen,
selenium, phosphorus and arsenic contaminants in the syngas is
undesirable. For this reason and depending on the quality of the
syngas, it can be useful to remove sulfur and other contaminants
from the feed before performing the Fischer-Tropsch chemistry.
Processes for removing these contaminants are well known to those
of skill in the art.
[0023] In the Fischer-Tropsch process, contacting a synthesis gas
comprising a mixture of H.sub.2 and CO with a Fischer-Tropsch
catalyst under suitable temperature and pressure reactive
conditions forms liquid and gaseous hydrocarbons. Examples of
conditions for performing Fischer-Tropsch reactions are well known
to those of skill in the art.
[0024] The fractions of the Fischer-Tropsch synthesis process may
range from C.sub.1 to C.sub.200+ with a majority in the C.sub.5 to
C.sub.100+ range. The reaction can be conducted in a variety of
reactor types, such as fixed bed reactors containing one or more
catalyst beds, slurry reactors, fluidized bed reactors, or a
combination of different type reactors. Such reaction processes and
reactors are well known and documented in the literature.
[0025] The slurry Fischer-Tropsch process, which is one embodiment
used in the practice of the invention, utilizes improved heat (and
mass) transfer characteristics for the strongly exothermic
synthesis reaction and is able to produce relatively high molecular
weight, paraffinic hydrocarbons when using a cobalt catalyst. In
one embodiment, the Fischer-Tropsch process used to produce the
base stock is taught in European Patent Application No. 9400600.7
(Publication No. EP 060 9079 B1).
[0026] In general, Fischer Tropsch catalysts contain a Group VII
transition metal on a metal oxide support. The catalysts may also
contain a noble metal promoter(s) and/or crystalline molecular
sieves. Suitable Fischer-Tropsch catalysts comprise one or more of
Fe, Ni, Co, Ru and Re. In one embodiment the Fischer-Tropsch
catalyst comprises cobalt. In one embodiment, the Fischer-Tropsch
catalyst comprises effective amounts of cobalt and one or more of
Re, Ru, Pt, Fe, Ni, Th, Zr, Hf, U, Mg and La on a suitable
inorganic support material. In one embodiment, the Fischer-Tropsch
catalyst comprises one or more refractory metal oxides. Useful
catalysts and their preparation are known and illustrated in U.S.
Pat. No. 4,568,663, which is intended to be illustrative but not
limiting the selection of the catalyst.
[0027] One example of a Fischer-Tropsch process is taught in
European Patent Application No. 9400600.7 (Publication No. EP 060
9079 B1). Examples of processes producing waxes of higher carbon
number distribution are taught in PCT International Application
PCT/EP98/08545 (Publication No. WO9934917 A1).
[0028] The fractions from Fischer-Tropsch reactions generally
include a light reaction fraction and a waxy reaction fraction,
which typically contain predominantly paraffins. It is the waxy
reaction fraction (i.e., the wax fraction) that can be used as a
feedstock to the process for providing the Fischer-Tropsch derived
lubricating base oil used in the blended lubricants and blended
finished lubricants of the present invention.
[0029] Isomerized Fischer-Tropsch distillate fractions can be
prepared from the waxy fractions of the Fischer-Tropsch syncrude by
a process including hydroisomerization. In one embodiment, the
Fischer-Tropsch lubricant base oils are made by a process as
described in U.S. Pat. No. 7,083,713, herein incorporated by
reference in its entirety.
[0030] Hydroisomerization is intended to improve the cold flow
properties of the lubricating base oil by the selective addition of
branching into the molecular structure. Hydroisomerization ideally
will achieve high conversion levels of the Fischer-Tropsch wax to
non-waxy iso-paraffins while at the same time minimizing the
conversion by cracking.
[0031] Hydroisomerization catalysts useful in the present invention
can comprise a shape selective intermediate pore size molecular
sieve and optionally a catalytically active metal hydrogenation
component on a refractory oxide support. In one embodiment, shape
selective intermediate pore size molecular sieves used for
hydroisomerization are based upon aluminum phosphates, such as
SAPO. SM-3 is an example of a shape selective intermediate pore
size SAPO, which has a crystalline structure falling within that of
the SAPO-11 molecular sieves. The preparation of SM-3 and its
characteristics are described in U.S. Pat. Nos. 4,943,424 and
5,158,665. Other shape selective intermediate pore size molecular
sieves used for hydroisomerization are zeolites, and SSZ-32 and
ZSM-23 are examples.
[0032] Other examples of intermediate pore size molecular sieves,
which can be useful in the present process, are described in U.S.
Pat. Nos. 5,135,638; 5,282,958 and 8,449,761, the contents of which
are hereby incorporated by reference in their entirety.
[0033] Hydroisomerization catalysts useful in the present invention
comprise a catalytically active hydrogenation metal. The presence
of a catalytically active hydrogenation metal leads to improvement
in base stock qualities, including VI and oxidation stability.
Examples of catalytically active hydrogenation metals include
chromium, molybdenum, nickel, vanadium, cobalt, tungsten, zinc,
platinum, and palladium. In one embodiment, the catalytically
active hydrogenation metals comprise platinum, palladium, or a
combination thereof.
[0034] The refractory oxide support may be selected from those
oxide supports, which are used for catalysts, including silica,
alumina, silica-alumina, magnesia, titania and combinations
thereof.
[0035] Examples of suitable conditions for performing
hydroisomerization are described in U.S. Pat. Nos. 5,282,958 and
5,135,638, the contents of which are incorporated by reference in
their entirety.
[0036] Hydrogen is present in the reaction zone during the
hydroisomerization process. Hydrogen may be separated from the
fraction and recycled to the reaction zone.
[0037] A waxy feed to the hydroisomerization process may be
hydrotreated prior to hydroisomerization dewaxing. Hydrotreating
refers to a catalytic process, usually carried out in the presence
of free hydrogen, which is used to remove various metal
contaminants, such as arsenic, aluminum, and cobalt; heteroatoms,
such as sulfur and nitrogen; oxygenates; or aromatics from the feed
stock.
[0038] Catalysts used in carrying out hydrotreating operations are
well known in the art, for example, U.S. Pat. Nos. 4,347,121 and
4,810,357, the contents of which are hereby incorporated by
reference in their entirety. Other suitable catalysts are
described, for example, in U.S. Pat. Nos. 4,157,294 and 3,904,513.
The non-noble hydrogenation metals, such as nickel-molybdenum, are
usually present in the final catalyst composition as oxides.
[0039] Typical hydrotreating conditions vary over a wide range.
[0040] Hydrofinishing is a hydrotreating process that may be used
as a step following hydroisomerization to provide a Fischer-Tropsch
lubricating base oil. Hydrofinishing is intended to improve
oxidation stability, ultraviolet UV light stability, and appearance
of the Fischer-Tropsch lubricating base oil fraction by removing
traces of aromatics, olefins, color bodies, and solvents. A general
description of hydrofinishing may be found in U.S. Pat. Nos.
3,852,207 and 4,673,487.
[0041] The conditions for hydrofinishing will be tailored to
achieve an isomerized Fischer-Tropsch derived distillate fraction
comprising weight percent aromatics less than 0.30.
[0042] Suitable hydrofinishing catalysts include noble metals from
the nickel family (Group 10), such as platinum or palladium or an
alumina or siliceous matrix, and unsulfided Group 10 and Group 6,
such as nickel-molybdenum or nickel-tin on an alumina or silica
matrix. The group numbers are those described in the International
Union of Pure and Applied Chemistry (IUPAC) Periodic Table of the
Elements, version dated 22 Jun. 2007. U.S. Pat. No. 3,852,207
describes a suitable noble metal catalyst and mild conditions.
Other suitable catalysts are described in U.S. Pat. Nos. 4,157,294
and 3,904,513.
[0043] Clay treating to remove impurities is an alternative final
process step to provide an isomerized Fischer-Tropsch derived
distillate fraction.
[0044] The separation of Fischer-Tropsch derived fractions and
petroleum derived fractions into various fractions having
characteristic boiling ranges in generally accomplished by either
atmospheric or vacuum distillation or by a combination of
atmospheric and vacuum distillation. Fractionating the lubricating
base oil into different boiling range cuts enables the lubricating
base oil manufacturing plant to produce more than one grade, or
viscosity, or lubricating base oil.
[0045] The process to make an isomerized Fischer-Tropsch derived
distillate fraction may also include a solvent dewaxing step
following the hydroisomerization process. Solvent dewaxing
optionally may be used to remove small amounts of remaining waxy
molecules from the lubricating base oil after hydroisomerization
dewaxing. Solvent dewaxing is done by dissolving the lubricating
base oil in a solvent, such as methyl ethyl ketone, methyl
iso-butyl ketone, or toluene, and precipitating the wax molecules.
Solvent dewaxing is described in U.S. Pat. Nos. 4,477,333;
3,773,650; 3,775,288 and 7,018,525.
[0046] Conventional synthetic oils include hydrocarbon synthetic
oils and synthetic esters. Useful synthetic hydrocarbon oils
include liquid polymers of alpha-olefins having the proper
viscosity. Especially useful are the hydrogenated liquid oligomers
of C.sub.6 to C.sub.12 alpha-olefins such as 1-decene trimer.
Similarly, alkyl benzenes of proper viscosity, such as didodecyl
benzene, may be used. Useful synthetic esters include the esters of
mono-carboxylic acids and polycarboxylic acids as well as
mono-hydroxy alkanols and polyols. Typical examples are didodecyl
adipate, pentaerthritol tetracapoate, di-2-ethylhexyl adipate,
di-laurylsebacate and the like. Complex esters prepared from
mixtures of mono- and di-carboxylic acid and mono- and di-hydroxy
alkanols can also be used.
[0047] Below are listed the American Petroleum Institute's (API)
base oil categories, Groups I-V. In one embodiment, the hydrocarbon
base oil that is selected is a base oil in API Base Oil Groups
II-V. Any suitable base stock oil can be used as the selected base
stock long as the PVC ratio requirement is met.
TABLE-US-00001 API Base Oil Categories Base Oil Sulfur Saturates
Viscosity Category (%) (%) Index Group I >0.03 and/or <90 80
to 120 Group II <0.03 and >90 80 to 120 Group III <0.03
and >90 >120 Group IV PAO synthetic lubricants Group V All
other base oils not included in Group I, II, III, IV
[0048] If desired, any of the conventional lubricating additives
can be added to fine tune the characteristics and properties of the
final lubricating oil composition. Below is described a number of
such exemplary lubricating additives.
Dispersants
[0049] The lubricating oil composition of the present invention can
contain dispersants. Dispersants suspend insoluble species in the
lubricating oil composition and keep equipment surfaces clean. In
one embodiment, the dispersant can be ashless. In one embodiment,
the ashless dispersants are nitrogen-containing dispersants formed
by reacting alkenyl succinic acid anhydride with an amine. Examples
of such dispersants are alkenyl succinimides and succinamides.
These dispersants can be further modified by reaction with, for
example, boron or ethylene carbonate. Ester-based ashless
dispersants derived from long chain hydrocarbon-substituted
carboxylic acids and hydroxy compounds may also be employed. In one
embodiment, ashless dispersants are those derived from
polyisobutenyl succinic anhydride. A large number of dispersants
are commercially available.
Anti-Wear Agents
[0050] Traditional wear inhibitors may be employed in the
lubricating oil compositions of this invention. As their name
implies, these agents reduce wear of moving metallic parts.
Examples of such anti-wear agents include, but are not limited to
phosphates, phosphites, carbamates, esters, sulfur containing
compounds, and molybdenum complexes. The lubricating oil
composition of this invention may comprise one or more anti-wear
agents, such as metal di-thio di-phosphates and metal
di-thiocarbamates or mixtures thereof. In one embodiment, the
anti-wear agent for use in this invention comprises zinc di-thio
di-phosphate.
Anti-Oxidants
[0051] In one embodiment, the lubricating oil composition comprises
one or more anti-oxidants. Anti-oxidants are used in lubricating
oils for inhibition of decomposition processes that occur naturally
in lubricating oils as they age or oxidize in the presence of air.
These oxidation processes may cause formation of gums, lacquers and
sludge resulting in an increase in acidity and viscosity. Examples
of useful anti-oxidants are hindered phenol oxidation inhibitors,
such as 4,4'-methylene-bis(2,6-di-tert-butylphenol),
4,4'-bis(2,6-di-tert-butylphenol),
4,4'-bis(2-methyl-6-tert-butylphenol),
2,2'-methylene-bis(4-methyl-6-tert-butylphenol),
4,4'-butylidene-bis(3-methyl-6-tert-butylphenol),
4,4'-isopropylidene-bis(2,6-di-tert-butylphenol),
2,2'-methylene-bis(4-methyl-6-nonylphenol),
2,2'-isobutylidene-bis(4,6-dimethylphenol),
2,2'-5-methylene-bis(4-methyl-6-cyclohexylphenol),
2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol,
2,4-dimethyl-6-tert-butyl-phenol,
2,6-di-tert-1-dimethylamino-p-cresol,
2,6-di-tert-4-(N,N'-di-methylaminomethylphenol),
4,4'-thiobis(2-methyl-6-tert-butylphenol),
2,2'-thiobis(4-methyl-6-tert-butylphenol),
bis(3-methyl-4-hydroxy-5-tert-10-butylbenzyl)-sulfide, and
bis(3,5-di-tert-butyl-4-hydroxybenzyl). Examples of alkylated and
non-alkylated aromatic amines are alkylated diphenylamine,
phenyl-alpha-naphthylamine, and alkylated-alpha-naphthylamine.
Other classes of anti-oxidants are esters of thiodicarboxylic
acids, salts of di-thiophosphoric acids, alkyl or aryl phosphates
and molybdenum compounds, such as amine-molybdenum complex compound
and molybdenum di-thiocarbamates may also be used as anti-oxidants,
provided the molybdenum compounds do not include tri-nuclear
molybdenum. However, their addition will contribute to the
phosphorus, sulfur and sulfated ash content of the lubricating
oil.
Low, Medium and High Overbased Metal Detergents
[0052] The lubricating oil composition can contain one or more
detergents. Detergents are metal salts of organic acids. Detergents
neutralize oxidation-derived acids and help suspend polar oxidation
products in the lubricating oil composition. Examples of the low
and medium overbased metal detergents employed in the lubricating
oil composition of the present invention are low, medium or high
overbased sulfonates, salicylates, phenates or Mannich condensation
products of alkylphenols, aldehydes and amines These detergents may
be alkali metal detergents or alkaline earth metal detergents. In
one embodiment, they are alkaline earth metal detergents and they
can be calcium detergents. The total base number (TBN) of these
detergents is from greater than 1 to about 500, or more. These
detergents are well known in the art and are commercially
available.
Other Additives
[0053] The lubricating oil composition of the present invention may
also contain, in addition to the additives discussed above, other
additives used to impart desirable properties to the lubricating
oil composition of the present invention. Thus, the lubricating oil
may contain one or more of additives, such as viscosity index
improvers, pour point depressants, demulsifiers, extreme pressure
agents and foam inhibitors. These additional additives are
described in more detail below.
Viscosity Index Improvers
[0054] Viscosity index improvers are added to lubricating oil to
regulate viscosity changes due to the change in temperature. Some
commercially available examples of viscosity index improvers are
olefin copolymers, such as ethylene-propylene copolymers,
styrene-isoprene copolymers, hydrated styrene-isoprene copolymers,
polybutene, polyisobutylene, polymethacrylates, vinylpyrrolidone
and methacrylate copolymers and dispersant type viscosity index
improvers.
Extreme Pressure Agents
[0055] Extreme pressure agents that may be used in the lubricating
oil composition of the present invention include alkaline earth
metal borated extreme pressure agents and alkali metal borated
extreme pressure agents. Extreme pressure agents containing
molybdenum may also be employed in the lubricating oil composition
of the present invention, provided the molybdenum compounds do not
include tri-nuclear molybdenum. Sulfurized olefins, zinc
dialky-1-dithiophosphate (primary alkyl, secondary alkyl, and aryl
type), di-phenyl sulfide, methyl tri-chlorostearate, chlorinated
naphthalene, fluoroalkylpolysiloxane, lead naphthenate, neutralized
or partially neutralized phosphates, di-thiophosphates, and
sulfur-free phosphates. In one embodiment, the extreme pressure
agents are those that will not contribute to the phosphorous
content of the lubricating oil.
Pour Point Depressants
[0056] Pour point depressants are additives that optimize the low
temperatures fluidity of the lubricating oil. Examples are various
copolymers.
Rust Inhibitors
[0057] Rust inhibitors include nonionic polyoxyethylene surface
active agents, such as polyoxyethylene lauryl ether,
polyoxyethylene higher alcohol ether, polyoxyethylene nonyl phenyl
ether, polyoxyethylene octyl phenyl ether, polyoxyethylene octyl
stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene
sorbitol monostearate, polyoxyethylene sorbitol mono-oleate, and
polyethylene glycol mono-oleate. Other compounds that may also be
employed as rust inhibitors include stearic acid and other fatty
acids, di-carboxylic acids, metal soaps, fatty acid amine salts,
metal salts of heavy sulfonic acid, partial carboxylic acid ester
of polyhydric alcohol, and phosphoric ester. In one embodiment, the
inhibitors are those that do not contribute to the phosphorus or
sulfur content of the lubricating oil. Some of the above listed
rust inhibitors may have friction modifying properties. However,
these could be added in quantities sufficient for rust inhibition,
but not high enough to provide their friction modifying
property.
Corrosion Inhibitors
[0058] Corrosion inhibitors are included in lubricating oils to
protect vulnerable metal surfaces. Such corrosion inhibitors are
generally used in very small amounts in the range of from about
0.02 weight percent to about 1.0 weight percent. Examples of
corrosion inhibitors that may be used are sulfurized olefin
corrosion inhibitor and the co-sulfurized alkenyl ester/alpha
olefin corrosion inhibitor.
Metal Deactivators
[0059] Metal deactivators that may be employed in the lubricating
oil composition of the present invention include but are not
limited to di-salicylidene propylenediamine, triazole derivatives,
mercaptobenzothiazoles, thiodiazole derivatives, and
mercaptobenzimidazoles.
Demulsifiers
[0060] An addition product of alkylphenol and ethylene oxide,
polyoxyethylene alkyl ether, and polyoxyethylene sorbitan ester may
be employed in the lubricating oil composition of the present
invention as demulsifiers.
Foam Inhibitors
[0061] Useful foam inhibitors for the present invention are alkyl
methacrylate polymers, dimethyl silicone polymers and polysiloxane
type foam inhibitors.
[0062] For best overall results in terms of affording the
properties desired in a conventional lubricating oil composition
for lubricating diesel engines, gasoline engines and natural gas
engines, the lubricating oil may contain a compatible combination
of additives of each of the above classes of additives in effective
amounts.
[0063] The various additive materials or classes of materials
herein described are well known materials and can be readily
purchased commercially or prepared by known procedures or obvious
modification thereof.
Example 1
[0064] A number of base oils were evaluated for their pressure
viscosity coefficient at 40.degree. C. and 100.degree. C., at 20N
and 50N pressure. The results are shown in the Table below:
TABLE-US-00002 100.degree. C./ 100.degree. C./ 40.degree. C. PVC
40.degree. C. PVC KVis @ KVis @ Ratio @ Ratio @ Description
40.degree. C. 100.degree. C. VI 20N 50N Chevron 20.60 4.138 101
0.64 0.72 100R Chevron 41.34 6.415 105 0.79 0.76 220R Chevron
107.70 12.180 103 0.87 0.91 600R Chevron 18.70 4.147 126 0.84 0.82
UCBO 4R Chevron 23.77 4.686 115 0.77 0.76 UCBO 5R Chevron 41.62
7.149 134 0.71 0.67 UCBO 7R PAO Synfluid 5.21 1.726 N/A 0.77 0.67 2
cSt PAO Synfluid 16.66 3.819 122 0.74 0.70 4 cSt PAO Synfluid 30.66
5.878 139 0.76 0.72 6 cSt PAO Synfluid 46.55 7.771 136 0.97 0.82 8
cSt Priolube 3970 19.41 4.362 137 0.77 0.75 Ester Esterex A51 27.00
5.300 133 0.70 0.68 Ester FTBO-XXL 8.02 2.409 125 0.84 0.84 FTBO-XL
9.23 2.653 128 0.68 0.68 FTBO-L 19.66 4.500 148 0.80 0.79 FTBO-M1
41.93 7.953 165 0.93 0.77 FTBO-M2 42.33 7.895 160 0.89 0.85 FTBO-M3
42.35 7.932 162 0.81 0.79 FTBO-M4 51.64 9.170 161 0.95 0.83 FTBO-H
106.40 16.010 161 1.03 1.02 FTBO-H2 108.40 16.240 161 1.00 1.01
Chevron UCBO 4R and UCBO 7R are API Group III base oils from
Chevron Corporation.
[0065] The FIGURE of the Drawing graphically depicts the
pressure-viscosity-coefficient for the FTBO base oils in the Table.
Only a few of them have a 100.degree. C. PVC/40.degree. C. PVC
ratio approaching 1.
Example 2
[0066] The following runs were made to demonstrate the superior
wear characteristics of the lubricating oils of the present
invention. Five separate comparative lubricating oils were made
using an SAE 15W-40 formulation with an additive package, using
Group II base stocks. The lubricating oil composition of the
present invention used a Fischer-Tropsch derived base oil, also
known as Gas-to-Liquid base oil (FTBO or GTL), and was blended with
another FTBO (FTBO 14). The actual viscosity of the base stocks was
different depending on the viscosity grade of the lubricating oil
composition. The FTBO used for the lubricating oil composition of
the present invention (FTBO 7) had a Kinematic Viscosity at
100.degree. C. of 7 mm.sup.2/sec.
[0067] The PVC ratio for each of the lubricating base stocks used
was determined as follows:
[0068] Pressure-Viscosity-Coefficient (PVC) Calculation Procedures:
[0069] Measure the EHL film thickness of the samples and the
reference oil,
[0070] Squalane, at desired temperatures, i.e., 100.degree. C. and
40.degree. C. [0071] Calculate the PVC values by applying the
following equation:
[0071] .alpha.S=.alpha.R[(hS/hR)(.eta.S/.eta.R)-0.67]1/0.53
[0072] The subscripts S and R refer to the samples and the
reference oil, respectively; .alpha. is the PVC value; h the film
thickness, and .eta. the dynamic viscosity.
[0073] The h values are measured on an EHL system, the viscosity
.eta. data can be measured or obtained by a provider of the base
stock. The parameter values .alpha. and .eta. of the reference oil,
Squalane, are available in the literature.
[0074] The EHL film thickness was measured on an EHL Ultra Thin
Film Measurement System, a computer controlled instrument for
measuring the film thickness and traction coefficient (friction
coefficient) of lubricants in the EHL lubricating regime.
[0075] The FTBO 7 had a 100.degree. C. PVC/40.degree. C. PVC ratio
of about 0.88, while the base stock with which it was blended, FTBO
14, had a 100.degree. C. PVC/40.degree. C. PVC ratio of about 0.97.
In the comparative lubricating oil compositions, the Motiva Star 5
and Motiva Star 8 had a 100.degree. C. PVC/40.degree. C. PVC ratio
of less than 0.80, as did the ExxonMobil EHC.TM. 110 and ExxonMobil
EHC.TM. 60 base stocks.
[0076] The following results were obtained by running the
lubricating oil compositions with the same additive package, but
differing base stocks through the Daimler OM611 test, which
evaluates engine crankcase lubricants with respect to wear under
severe operating conditions.
TABLE-US-00003 Comparatives Example SAE Viscosity Grade 15W-40
15W-40 15W-40 15W-40 15W-40 10W-40 Inlet Camshaft wear [.mu.m] 78
117 60 132 131 38 Outlet Camshaft wear [.mu.m] 166 174 139 183 188
58 Base oil % Motiva Star 5 19 21 -- -- -- -- Motiva Star 8 81 79
-- -- -- -- ExxonMobil EHC .TM. 110 -- -- 29 36 36 -- ExxonMobil
EHC .TM. 60 -- -- 71 64 64 -- Chevron FTBO 7 -- -- -- -- -- 68
Chevron FTBO 14 -- -- -- -- -- 32 Viscosity modifier 6 7 6.7 6.1
6.5 0.95
[0077] The results show that the lubricating oil composition
comprising the hydrocarbon base stock having a 100.degree. C.
PVC/40.degree. C. PVC ratio approaching one or greater exhibited
camshaft wear that was excellent, as it was 37.9/57.6 .mu.m
(inlet/outlet valve), far lower than any of the other 5 runs.
Example 3
[0078] The following results were obtained by running lubricating
oils with the same additive package, but differing base stocks
through the Cummins Interact System B (ISB) valve-train wear test
(ASTM D7484). The PVC ratio for each hydrocarbon base stock was
determined in Example 1, and is the same as noted in Example 1.
TABLE-US-00004 Comparative Example A Example B Viscosity Grade
15W-40 10W-40 5W-30 Camshaft wear [.mu.m] 49 15 37 Tappet weight
loss [mg] 91 36 47 Base oil % Motiva Star 5 21 -- -- Motiva Star 8
79 -- -- Chevron FTBO 7 -- 69 100 Chevron FTBO 14 -- 31 --
Viscosity modifier 7 1.65 0.8
[0079] The overall performance demonstrated in the Daimler OM 611
Engine Test and in the Cummins ISB Engine Test (ASTM D7484) clearly
demonstrated the improved wear performance of the present
lubricating oil compositions. In both tests/examples, the
comparatives were blended to a higher viscosity grade than the
lubricating oil composition of the present invention, yet the lower
viscosity grade lubricating oil composition of the present
invention provided improved wear benefits. In all cases, the
comparative and the present lubricating oil compositions differed
only in the base stock selection, with no differences in their
surface active additives.
[0080] The determination and selection of a base stock oil having a
100.degree. C. PVC/40.degree. C. PVC ratio approaching one provided
for superior wear properties, even at lower viscosity grades.
Example 4
[0081] The PVC @ 40.degree. C. and 100.degree. C., at 20N pressure,
was evaluated for three Group II base stocks. The results are in
the Table below. The ratio of 100.degree. C. PVC/40.degree. C. PVC
did not approach 1, and was far less than 0.85. These base stocks,
which are the same as those disclosed in US Patent Publication No.
20100162981, would not be appropriate for the present lubricating
oil composition.
TABLE-US-00005 100/40 PVC PVC@40.degree. C. PVC@100.degree. C.
Ratio @ 20N ExxonMobil 20.85 12.38 0.59 Jurong 150N - 5.32 cSt
kv100 ExxonMobil 26.72 16.05 0.60 Jurong 500N - 10.45 cSt kv100
ExxonMobil 19.77 12.92 0.65 Jurong 50% 150N & 50% 500N - 7.32
cSt kv100
[0082] Various modifications and alterations of this invention will
become apparent to those skilled in the art without departing from
the scope and spirit of the invention. Other objects and advantages
will become apparent to those skilled in the art from a review of
the preceeding description.
* * * * *