U.S. patent application number 10/317864 was filed with the patent office on 2003-07-17 for heavy duty diesel engine lubricating oil compositions.
Invention is credited to Arrowsmith, Stephen, Bovington, Charles H., Castle, Rebecca C., Wrench, Peter.
Application Number | 20030134758 10/317864 |
Document ID | / |
Family ID | 8182569 |
Filed Date | 2003-07-17 |
United States Patent
Application |
20030134758 |
Kind Code |
A1 |
Bovington, Charles H. ; et
al. |
July 17, 2003 |
Heavy duty diesel engine lubricating oil compositions
Abstract
The use of an effective amount of one or more compounds capable
of reducing friction coefficients under mixed lubrication or
boundary lubrication conditions in a heavy duty diesel engine
lubricating oil composition for improving the fuel economy of a
heavy duty diesel engine.
Inventors: |
Bovington, Charles H.;
(Faringdon, GB) ; Arrowsmith, Stephen; (Didcot,
GB) ; Castle, Rebecca C.; (Kidlington, GB) ;
Wrench, Peter; (Wantage, GB) |
Correspondence
Address: |
Infineum USA L.P.
Law Department
1900 East Linden Avenue
P.O. Box 710
Linden
NJ
07036-0710
US
|
Family ID: |
8182569 |
Appl. No.: |
10/317864 |
Filed: |
December 12, 2002 |
Current U.S.
Class: |
508/525 |
Current CPC
Class: |
C10M 2215/042 20130101;
C10M 2227/09 20130101; C10N 2030/06 20130101; C10N 2070/02
20200501; C10M 2219/068 20130101; C10N 2010/12 20130101; C10M
2215/082 20130101; C10N 2010/04 20130101; C10M 2219/046 20130101;
C10N 2030/56 20200501; C10M 2207/028 20130101; C10N 2040/252
20200501; C10M 2215/28 20130101; C10N 2010/02 20130101; C10M
2215/04 20130101; C10M 2223/045 20130101; C10M 2219/086 20130101;
C10M 2207/283 20130101; C10N 2060/14 20130101; C10M 2207/262
20130101; C10M 163/00 20130101; C10M 2207/289 20130101 |
Class at
Publication: |
508/525 |
International
Class: |
C10M 129/48 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 21, 2001 |
EP |
01310820.4 |
Claims
What is claimed is:
1. A method composition for improving the fuel economy of a heavy
duty diesel engine, which method comprises lubricating said engine
with a lubricating oil composition comprising an effective amount
of one or more compounds capable of reducing friction coefficients
under mixed lubrication or boundary lubrication conditions in a
heavy duty diesel engine lubricating oil composition.
2. The method of claim 1 wherein the heavy duty diesel engine is
the engine of a land-based vehicle, has a total displacement of at
least 6.5 litres and a displacement per cylinder of at least 1.0
litre per cylinder.
3. A heavy duty diesel engine lubricating oil composition
comprising an oil of lubricating viscosity, in a major amount, and
added thereto: (A) an effective amount of one or more compounds
capable of reducing friction coefficients under mixed lubrication
or boundary lubrication conditions; (B) a minor amount of a
detergent composition comprising a metal salt of an aromatic
carboxylic acid; and (C) a minor amount of a dispersant additive;
provided that the lubricating oil composition has a nitrogen
content of at least 0.06 mass %, based on the mass of the
composition.
4. The oil composition of claim 3, wherein the oil composition
satisfies at least the API CG-4 performance specification and/or
the ACEA E2-96 performance specification.
5. The oil composition of claim 3 in the form of an SAE 5W-X or SAE
0W-X lubricating oil composition, where X is any one of 20, 30, 40
and 50.
6. The oil composition of claim 4 in the form of an SAE 5W-X or SAE
0W-X lubricating oil composition, where X is any one of 20, 30, 40
and 50.
7. The oil composition of claim 3 wherein the base blend viscosity
of the composition is at least 8.2 mm.sup.2s.sup.-1 at 100.degree.
C.
8. The oil composition of claim 4 wherein the base blend viscosity
of the composition is at least 8.2 mm.sup.2s.sup.-1 at 100.degree.
C.
9. The oil composition of claim 5 wherein the base blend viscosity
of the composition is at least 8.2 mm.sup.2s.sup.-1 at 100.degree.
C.
10. The oil composition of claim 3 wherein the or at least one of
the compounds has a polar head-group and an oleophilic hydrocarbyl
chain.
11. The oil composition of claim 4 wherein the or at least one of
the compounds has a polar head-group and an oleophilic hydrocarbyl
chain.
12. The oil composition of claim 5 wherein the or at least one of
the compounds has a polar head-group and an oleophilic hydrocarbyl
chain.
13. The oil composition of claim 3 wherein the or at least one of
the compounds is a molybdenum compound.
14. The oil composition of claim 4 wherein the or at least one of
the compounds is a molybdenum compound.
15. The oil composition of claim 5 wherein the or at least one of
the compounds is a molybdenum compound.
16. A heavy duty diesel engine additive concentrate composition
comprising a diluent and one or more additives comprising: (A) one
or more compounds capable of reducing friction coefficients under
mixed lubrication or boundary lubrication conditions; (B) a
detergent composition comprising a metal salt of an aromatic
carboxylic acid; and (C) a dispersant additive; each in such a
proportion as to provide a heavy duty diesel engine lubricating oil
composition as defined in claim 3 when the oil composition contains
2 to 20 mass % of the additives.
17. A combination of a heavy duty diesel engine in a land-based
vehicle, which engine has a total displacement of at least 6.5
litres and a displacement per cylinder of at least 1.0 litre per
cylinder and a lubricating oil composition as defined in claim 3.
Description
[0001] The present invention concerns the use of one or more
compounds capable of reducing friction coefficients under mixed
lubrication or boundary lubrication conditions in heavy duty diesel
engine lubricating oil compositions. It also relates to such
lubricating oil compositions which have been found to give improved
fuel economy in operation of heavy duty diesel engines.
[0002] The heavy duty trucking market employs the diesel engine as
its preferred power source due to its excellent longevity, and
specialized lubricants have been developed to meet the more
stringent performance requirements of such heavy duty diesel
engines.
[0003] Also, several engine tests are required to demonstrate
satisfactory heavy duty performance, including the Cummins M11 test
to evaluate soot-related valve train wear, filter plugging and
sludge.
[0004] The fuel consumption of heavy duty diesel engines is of
great importance to fleet operators since fuel costs constitute up
to 30% of operating costs. Use of fuel-efficient lubricating oil
compositions would therefore help to reduce fuel consumption: even
a 1% reduction would lead to significant cost savings.
[0005] R. I Taylor states in "Heavy Duty Diesel Engine Fuel
Economy: Lubricant Sensitivities" 00FL-309, SAE 2000 Millennium
Publication "Advances in Powertrain Tribology", SAE 2000, that,
because heavy duty diesel engines operate more under hydrodynamic
conditions than passenger car engines, friction reducers will not
be effective in reducing engine friction losses in heavy duty
diesel engines. This conclusion is supported by Stauffer et al in
Lubrication Engineering, December 1984, pp.744-751; and by Kagaya
et al in SAE 811412.
[0006] It has now been found, in contrast, that friction reducers
are effective in improving the fuel economy performance of heavy
duty diesel engines. Accordingly, in a first aspect the present
invention provides the use of an effective amount of one or more
compounds capable of reducing friction coefficients under mixed
lubrication or boundary lubrication conditions in a heavy duty
diesel engine lubricating oil composition for improving the fuel
economy of a heavy duty diesel engine.
[0007] In a second aspect, the present invention provides a heavy
duty diesel engine lubricating oil composition comprising an oil of
lubricating viscosity, in a major amount, and added thereto:
[0008] (A) an effective amount of one or more compounds capable of
reducing friction coefficients under mixed lubrication or boundary
lubrication conditions;
[0009] (B) a minor amount of a detergent composition comprising a
metal salt of an aromatic carboxylic acid; and
[0010] (C) a minor amount of a dispersant additive;
[0011] provided that the lubricating oil composition has a nitrogen
content, preferably derived from the dispersant additive, of at
least 0.06 mass %, based on the mass of the composition.
[0012] In a third aspect, the present invention provides a heavy
duty diesel engine additive concentrate composition comprising a
diluent and one or more additives comprising:
[0013] (A) one or more compounds capable of reducing friction
coefficients under mixed lubrication or boundary lubrication
conditions;
[0014] (B) a detergent composition comprising a metal salt of an
aromatic carboxylic acid; and
[0015] (C) a dispersant additive;
[0016] each in such a proportion as to provide a heavy duty diesel
engine lubricating oil composition as defined in the second aspect
when the oil composition contains 2 to 20 mass % of the
additives.
[0017] In a fourth aspect, the present invention provides
combination of a heavy duty diesel engine in a land-based vehicle,
which engine has a total displacement of at least 6.5 litres and a
displacement per cylinder of at least 1.0 litre per cylinder and a
lubricating oil composition as defined in the second aspect.
[0018] In a fifth aspect, the present invention provides a method
of lubricating a heavy duty diesel engine in a land-based vehicle,
which engine has a total displacement of at least 6.5 litres and a
displacement per cylinder of at least 1.0 litre per cylinder, which
method comprises supplying to the engine a lubricating oil
composition as defined in the second aspect.
[0019] The American Petroleum Institute (API), Association des
Constructeur Europen d'Autombile (ACEA) and Japanese Standards
Organisation (JASO) specify the performance level required for
lubricating oil compositions. Also there are performance
specifications known as Global, which contains tests and
performance levels from ACEA, API and JASO specifications.
[0020] Thus, a heavy duty lubricating oil composition of the
present invention preferably satisfies at least the performance
requirements of heavy duty diesel engine lubricants, such as at
least the API CF-4 or API CG-4; preferably at least the API CH-4;
especially at least the API CI-4. In another embodiment, the
lubricating oil composition of the invention, independently of
meeting the API performance requirements, preferably satisfies at
least the ACEA E2-96; more preferably at least the ACEA E3-96;
especially at least ACEA E4-99; advantageously at least the ACEA
E5-99. In a further embodiment, the lubricating oil composition of
the invention, independently of meeting the API and ACEA
performance requirements, preferably satisfies the JASO DH-1 or
Global DHD-1.
[0021] The features of the present invention will now be discussed
in more detail.
[0022] Heavy Duty Diesel Engines
[0023] Heavy duty diesel engines according to the present invention
are used in land-based vehicles, preferably large road vehicles,
such as large trucks. The road vehicles typically have a weight
greater than 12 tonnes. The engines used in such vehicles tend to
have a total displacement of at least 6.5, preferably at least 8,
more preferably at least 10, such as at least 15, litres; engines
having a total displacement of 12 to 20 litres are preferred.
Generally, engines having a total displacement greater than 24
litres are not considered land-based vehicles. The engines
according to the present invention also have a displacement per
cylinder of at least 1.0 or at least 1.5, such as at least 1.75,
preferably at least 2, litres per cylinder. Generally, heavy duty
diesel engines in road vehicles have a displacement per cylinder of
at most 3.5, such as at most 3.0; preferably at most 2.5, litres
per cylinder. The term "heavy duty" in relation to internal
combustion engines is known in the art: see ASTM D4485 at
.sctn.3.17 where heavy duty engine operation is characterised by
average speeds, power outputs and internal temperatures that are
generally close to potential maximums; therefore, a heavy duty
diesel engine is considered to operate generally under such
conditions.
[0024] As used herein, the terms `total displacement` and
`displacement per cylinder` are known to those skilled in the art
of internal combustion engines (see "Diesel Engine Reference Book",
edited by B. Challen and R. Baranescu, second edition, 1999,
published by SAE International). Briefly, the term "displacement`
corresponds to the volume of the cylinder in the engine as
determined by the piston movement and consequently the "total
displacement" is the total volume dependent on the number of
cylinders; and the term `displacement per cylinder` is the ratio of
the total displacement to the number of cylinders in the
engine.
[0025] Lubricating Oil Composition
[0026] In each aspect of the invention, the lubricating oil
composition preferably has less than 0.13, or less than 0.1, or
less than 0.09, or less than 0.08, or less than 0.07 or less than
0.06, mass % of phosphorus based on the mass of the oil
composition; more preferably it has at most 0.05, or at most 0.04
or at most 0.03, mass %; such as in the range from 0.001 to 0.03
mass %; for example at most 0.02 or at most 0.01 mass %. In a
preferred embodiment of each aspect, the phosphorus content of the
lubricating oil composition is zero.
[0027] In each aspect of the invention, the lubricating oil
composition preferably has, independently of the amount of
phosphorus, at most 1.0, or at most 0.75, or at most 0.50, or at
most 0.45, or at most 0.4, or at most 0.35, or at most 0.3, or at
most 0.25, mass % of sulfur based on the mass of the oil
composition; especially it has at most 0.2 or at most 0.15, mass %;
such as in the range from 0.001 to 0.1 mass %. In a preferred
embodiment of each aspect, the sulfur content of the lubricating
oil composition is zero.
[0028] The amount of phosphorus and sulfur in the lubricating oil
composition is each measured according to ASTM D5185.
[0029] In an embodiment of each aspect of the invention, the amount
of phosphorus and sulfur is derived from an anti-wear additive,
such as a zinc dithiophosphate.
[0030] The lubricating oil composition of the invention can be in
the viscometric form of any one of SAE 20W-X, SAE 15W-X, SAE 10W-X,
SAE 5W-X and SAE 0W-X, where X represents any one of 20, 30, 40 and
50; the characteristics of the different viscometric grades can be
found in the SAE J300 classification. In an embodiment of each
aspect of the invention, independently of the other embodiments,
the lubricating oil composition is in the form of an SAE 5W-X or
SAE 0W-X lubricating oil composition, wherein X represents any one
of 20, 30, 40 and 50. Preferably X is 20 or 30.
[0031] It has also found that the lubricating oil compositions of
the invention can meet the wear protection needed by heavy duty
diesel engines, for example, by satisfying the requirements of the
Cummins M11 test to evaluate soot- related valve train wear. Thus,
the heavy duty diesel engine lubricating oil compositions of the
present invention, particularly low viscosity lubricating oil
compositions, such as SAE 5W-X or SAE 0W-X lubricants, where X is
as defined above, provide improved fuel economy and also improved
wear protection to the heavy duty diesel engine.
[0032] Thus, in a preferred embodiment of each aspect of the
present invention, the heavy duty diesel engine lubricating oil
composition, preferably in the form of an SAE 5W-X or SAE 0W-X oil
composition, comprises one or more compounds capable of reducing
friction coefficients under mixed lubrication or boundary
lubrication conditions, and has a base blend viscosity of at least
8.2, such as from 8.5 to 30, preferably 8.5 to 10, mm.sup.2s.sup.-1
at 100.degree. C.
[0033] As used herein, the term "base blend viscosity" refers to
the viscosity at 100.degree. C., measured according to ASTM D445,
of a composition comprising, or an admixture of, components that
exhibit Newtonian behaviour, which in the present invention are all
of the components (including the carrier oil such as the basestock)
but excluding the solid polymer or `active ingredient` of the
viscosity modifier, which is considered not to exhibit Newtonian
behaviour. Thus, the base blend viscosity can refer to the
viscosity of a composition comprising basestock oil, dispersant,
detergent, ZDDP, antioxidant, all carrier oils and diluent oils of
the components, pour depressant and any other components which
exhibit Newtonian behaviour, such as anti-foamants.
[0034] Computer modeling systems may also be employed to predict
the base blend viscosity of a lubricating oil composition based on
the viscosity of the components present therein. Alternatively, the
base blend viscosity may be measured by removing the polymer of the
viscosity modifier from the lubricating oil composition and then
measuring the viscosity of the resulting composition.
Alternatively, the base blend viscosity may be determined by
measuring the viscosity of the lubricating oil composition at a
high shear rate, which shear rate corresponds to the rate that does
not affect the viscosity of the oil composition, generally such
rates are greater than 10.sup.7 s.sup.-1.
[0035] It has been found that lubricating oil compositions having
the defined base blend viscosity parameter and one or more of the
defined compounds will provide improved fuel economy and pass at
least the ACEA E5-99 and/or the API CH-4 specification limits for
the Cummins M11 200 hour cross-head wear test.
[0036] In a preferred embodiment of each aspect of the present
invention, the oil composition has less than 2 mass % of ash,
preferably less than 1.5 mass %, especially less than 1 mass %;
such as in the range from 0 to 0.5 mass % ash, according to method
ASTM D874.
[0037] Oil of Lubricating Viscosity
[0038] The lubricating oil can be a synthetic or mineral oil of
lubricating viscosity selected from the group consisting of Group
I, II, III, IV or V basestocks and mixtures thereof.
[0039] Basestocks may be made using a variety of different
processes including but not limited to distillation, solvent
refining, hydrogen processing, oligomerization, esterification and
rerefining.
[0040] API 1509 "Engine Oil Licensing and Certification System",
Fourteenth Edition, December 1996 states that all basestocks are
divided into five general categories:
[0041] Group I basestocks contain less than 90% saturates and/or
greater than 0.03% sulfur and have a viscosity index greater than
or equal to 80 and less than 120;
[0042] Group II basestocks contain greater than or equal to 90%
saturates and less than or equal to 0.03% sulfur and have a
viscosity index greater than or equal to 80 and less than 120;
[0043] Group III basestocks contain greater than or equal to 90%
saturates and less than or equal or 0.03% sulfur and have a
viscosity index greater than or equal to 120;
[0044] Group IV basestocks contain polyalphaolefins (PAO); and
[0045] Group V basestocks contain all other basestocks not included
in Group I, II, III or IV.
[0046] Group IV basestocks, i.e. polyalphaolefins (PAO), include
hydrogenated oligomers of an alpha-olefin, the most important
methods of oligomerization being free radical processes, Ziegler
catalysis, cationic, and Friedel-Crafts catalysis.
[0047] Preferably the lubricating oil is selected from any one of
Group I to V basestocks.
[0048] Especially preferred is Group II, III, IV or V basestocks or
any two or more mixtures thereof, or mixtures of Group IV
basestocks with 5 to 80 mass % of Group I, II, III or V basestocks,
such as a fully synthetic mixture of Group IV basestocks and Group
V basestocks.
[0049] The test methods used in defining the above groups are ASTM
D2007 for saturates; ASTM D2270 for viscosity index; and one of
ASTM D2622, 4294, 4927 and 3120 for sulfur.
[0050] Compounds
[0051] Compounds capable of reducing friction coefficients under
mixed lubrication or boundary lubrication conditions, such as in
high pressure and sliding contacts, are known as friction reducers
and a skilled person would be able to identify such compounds using
tests known in the art, for example tests carried out in a high
frequency reciprocating rig. Examples of contacts where high
pressure and sliding conditions occur are in the valve train,
piston ring liners and journal bearings.
[0052] A class of friction reducers is provided by polar compounds
that are capable of being adsorbed on metal surfaces, which
compounds have a polar head- group and an oleophilic hydrocarbyl
chain. These can be broadly divided into two categories, i.e. (A)
nitrogen-containing compounds, such as amines, imides and amides,
and (B) oxygen-containing compounds, such as fatty acids and full
or partial esters thereof.
[0053] The nitrogen-compounds (A) are suitably selected from the
group consisting of (i) alkylene amines, especially the
monoalkylene diamines, the dialkylene triamines and/or the
polyalkylene polyamines, N,N'-dimethyl ethylene diamine which in
turn may carry further alkyl and/or hydroxy substituents; (ii) the
alkanolamines, especially the N-alkyl derivatives of alkanolamines,
such as ethanolamine, propanolamine, isopropanolamine and
butanolamine in which the N-alkyl groups have from 1 to 20 carbon
atoms, preferably 12 to 18 carbon atoms, the N,N-dialkanolamines,
the N-alkyleneaminoalkyl dialkanolamines, and the
di(polyalkyleneoxy) alkanolamines; (iii) the alkyl amides in which
the N-alkyl groups have from 1 to 25 carbon atoms, preferably 12 to
22 carbon atoms; and (iv) the alkanolamides, especially the mono-
and di-alkanolamides of alkyl carboxylic acids and the
(polyalkyleneoxy) alkanolamides. Specific examples of
nitrogen-containing organic friction reducers falling into the
above categories are:
[0054] (i) the monoethylene diamines, diethylene triamines, the
triethylene tetraamines and the tetraethylene pentamines, and the
N-alkyl derivatives thereof, e.g. Duomeen.RTM.T, and
N,N'-di(l-hydroxyl-1,1-dimet- hyl methyl) ethylene diamine, i.e.
Kaneda.RTM. No. 6;
[0055] (ii) N-alkyl or the appropriate N,N-dialkyl derivatives of
ethanol amines, diethanol amines, propanol amines, iso-propanol
amines, butanol amines, the N-alkyleneaminoalkyl ethanolamine in
which the alkyl group has 10 to 20 carbon atoms,
di(polyalkyleneoxy) alkanolamines in which the total number of
alkyleneoxy groups may range from 2 to 20, preferably from 5 to 15
groups, especially N-methyl ethanolamine (Kaneda.RTM. No.1),
N-hydrocarbyl diethanolamine (Kaneda.RTM. No. 2B), N, N-dibutyl
ethanolamine (Kaneda.RTM. No. 4), N-dodecyl diethanolamine
(Ethomeen.RTM.C12), N-hydrocarbyl diethanolamine
(Ethomeen.RTM.S12), N-trimethyleneaminoalkyl diethanolamine in
which the alkyl group has 12 to 18 carbon atoms (Ethoduomeen.RTM.),
the N-alkyl-di (polyalkyleneoxy) diethanolamines which respectively
have 5, 10 and 15 polyethyleneoxy groups (Tamno.RTM.-5, -10 and -15
respectively), and N,N'-dihydroxyethyl ethylenediamine
(Kaneda.RTM.No.5);
[0056] (iii) the alkyl amides in which the alkyl groups have from 1
to 30 carbon atoms, preferably from 5 to 20 carbon atoms and in
which the alkyl groups may be straight or branched chain groups,
such as Armoslip.RTM.CP-P and Armoslip.RTM.E in which the alkyl
groups have 17 and 21 carbon atoms respectively;
[0057] (iv) ethanolamides, the diethanolamides and the
(polyalkyleneoxy) ethanolamides, and the N-alkyl derivatives
thereof wherein the N-alkyl group has from 1 to 25 carbon atoms,
preferably from 5 to 20 carbon atoms and wherein in the case of the
(polyalkyleneoxy) ethanolamides said amides having from 5 to 20
polyoxyalkylene groups, such as N-acylethanol amine, e.g.
Kaneda.RTM. No. 9 (in which the alkyl group in the acyl moiety has
12 carbon atoms), diethanolamines e.g. Amizole.RTM. ISDE (in which
the alkyl group in the acyl moiety has 18 carbon atoms),
Kaneda.RTM. No.10 (in which the alkyl group in the acyl moiety has
12 carbon atoms), di(polyethyleneoxy) ethanol amide wherein the
acyl group in the acyl moiety has 17 carbon atoms and the total
number of polyethyleneoxy groups in the molecule is 5 (e.g.
Tamdo.RTM.-5).
[0058] Especially preferred examples are compounds of oleic acid
and tetraethylene pentamine, ethoxylated tallow amines and
ethoxylated tallow ether amines. Also useful are organo-metallic
compounds of hydrocarbyl amine compounds, such as disclosed in
GB-A-882,295. Amines may be used as such or in the form of an
adduct or reaction product with a boron compound such as a boric
oxide, boron halide, metaborate, boric acid or a mono-, di- or
trialkyl borate.
[0059] Examples of oxygen-containing organic friction reducers (B)
are carboxylic acids having 1 to 25 carbon atoms, such as stearic
acid and oleic acids, preferably from 12 to 17 carbon atoms; full
and partial esters thereof of di- and/or polyhydric alcohols, such
as glycerol, trimethylol propane, pentaerythritol and polyhydroxy
pyrans; and metal salts thereof, e.g. metal stearates and metal
oleates, wherein the metal is selected from transition metals (e.g.
zinc), Group 1 metals and Group 2 metals (e.g. calcium). Specific
examples of oxygen-containing organic friction reducers (B) are the
mono-, di- an tri-esters of glycerol with an alkyl carboxylic acid,
such as oleic acid; the corresponding pentaerythritol esters, such
as the oleates, especially the mono-oleates; and the monoester of
1-methylenehydroxy-2, 3, 4-trihydroxy pyran, in which the methylene
hydroxy group has been esterified with acetic acid. Esters of
carboxylic acids and anhydrides with alkanols are described in U.S.
Pat. No. 4,702,850.
[0060] Examples of other conventional friction reducers are
described by M. Belzer in the "Journal of Tribology" (1992),
Vol.114, pp. 675-682 and M. Belzer and S Jahanmir in "Lubrication
Science" (1988), Vol, pp. 3-26.
[0061] Oil-soluble additives which deposit molybdenum disulfide are
also effective friction reducers, such as oil-soluble or
oil-dispersible molybdenum compounds.
[0062] Examples of organic molybdenum compounds include molybdenum
xanthates, thioxanthates, alkoxides, carboxylates (such as,
derivatives of polyhydroxy fatty esters, e.g. MOLYVAN.RTM. 855),
dialkyldithiocarbamates, dialkyldithiophosphinates and
dialkyldithiophosphates.
[0063] The molybdenum compound may, for example, be mononuclear,
dinuclear, trinuclear or tetranuclear.
[0064] Dinuclear molybdenum compounds can be represented by the
formula Mo.sub.2O.sub.xS.sub.4-xL.sub.2, where L is a ligand such
as dialkyldithiocarbamate and dialkyldithiophosphate, and x is an
integer from 0 to 4. An example of dinuclear (or dimeric)
molybdenum dialkyldithiocarbamate is expressed by the following
formula: 1
[0065] where R.sub.1 to R.sub.4 independently denote a straight
chain, branched chain or aromatic hydrocarbyl group having 1 to 24
carbon atoms; and X.sub.1 to X.sub.4 independently denote an oxygen
atom or a sulfur atom. The four hydrocarbyl groups, R.sub.1 to
R.sub.4, may be identical or different from one another.
[0066] Another group of organo-molybdenum compounds useful in the
lubricating compositions of this invention are trinuclear (or
trimeric) molybdenum compounds, especially those of the formula
Mo.sub.3S.sub.kL.sub.nQ.sub.z and mixtures thereof wherein the L
are independently selected ligands having organo groups with a
sufficient number of carbon atoms to render the compound soluble in
the oil, n is from 1 to 4, k varies from 4 to 7, Q is selected from
the group of neutral electron donating compounds such as water,
amines, alcohols, phosphines, and ethers, and z ranges from 0 to 5
and includes non-stoichiometric values. At least 21 total carbon
atoms should be present among all the ligands' organo groups, such
as at least 25, at least 30, or at least 35 carbon atoms.
[0067] The ligands may be selected from the group consisting of
2
[0068] and mixtures thereof, wherein X, X.sub.1, X.sub.2, and Y are
selected from the group consisting of oxygen and sulfur, and
wherein R.sub.1, R.sub.2, and R are selected from hydrogen and
organo groups that may be the same or different. Preferably, the
organo groups are hydrocarbyl groups such as alkyl (e.g. in which
the carbon atom attached to the remainder of the ligand is primary
or secondary), aryl, substituted aryl and ether groups. More
preferably, each ligand has the same hydrocarbyl group.
[0069] The term "hydrocarbyl" as used herein denotes a substituent
having carbon atoms directly attached to the remainder of the
ligand and is predominantly hydrocarbyl in character. Such
substituents include the following:
[0070] 1. Hydrocarbon substituents, that is, aliphatic (for example
alkyl or alkenyl), alicyclic (for example cycloalkyl or
cycloalkenyl) substituents, aromatic-, aliphatic- and
alicyclic-substituted aromatic nuclei, as well as cyclic
substituents wherein the ring is completed through another portion
of the ligand (that is, any two indicated substituents may together
form an alicyclic group).
[0071] 2. Substituted hydrocarbon substituents, that is, those
containing non-hydrocarbon groups which do not alter the
predominantly hydrocarbyl character of the substituent. Those
skilled in the art will be aware of suitable groups (e.g., halo,
especially chloro and fluoro, amino, alkoxyl, mercapto,
alkylmercapto, nitro, nitroso, sulfoxy, etc.).
[0072] Importantly, the organo groups of the ligands have a
sufficient number of carbon atoms to render the compound soluble in
the oil. For example, the number of carbon atoms in each group will
generally range between 1 to 100, preferably from 1 to 30, and more
preferably between 4 to 20. Preferred ligands include
dialkyldithiophosphate, alkylxanthate, carboxylates,
dialkyldithiocarbamate ("dtc"), and mixtures thereof. Most
preferred are the dialkyldithiocarbamates. Those skilled in the art
will realize that formation of the compounds of the present
invention requires selection of ligands having the appropriate
charge to balance the core's charge (as discussed below).
[0073] Compounds having the formula Mo.sub.3S.sub.kL.sub.nQ.sub.z
have cationic cores surrounded by anionic ligands, wherein the
cationic cores are represented by structures such as 3
[0074] which have net charges of +4. Electrical neutrality to the
trinuclear molybdenum Mo.sub.3S.sub.k species, where k is 4 to 7,
is conferred by appropriate choice of anionic and cationic
compounds. Four monoanionic ligands, e.g. dithiocarbamate, are
preferred. Without wishing to be bound by any theory, it is
believed that two or more trinuclear cores may be bound or
interconnected by means of one or more ligands and the ligands may
be multidentate, i.e., having multiple connections to one or more
cores. It is believed that oxygen and/or selenium may be
substituted for sulfur in the core(s).
[0075] Oil-soluble trinuclear molybdenum compounds can be prepared
by reacting in the appropriate liquid(s)/solvent(s) a molybdenum
source such as (NH.sub.4).sub.2Mo.sub.3S.sub.13.n(H.sub.2O), where
n varies between 0 and 2 and includes non-stoichiometric values,
with a suitable ligand source such as a tetralkylthiuram disulfide.
Other oil-soluble trinuclear molybdenum compounds can be formed
during a reaction in the appropriate solvent(s) of a molybdenum
source such as (NH.sub.4).sub.2Mo.sub.3S.sub.1- 3.n(H.sub.2O), a
ligand source such as tetralkylthiuram disulfide,
dialkyldithiocarbamate, or dialkyldithiophosphate, and a
sulfur-abstracting agent such as cyanide ions, sulfite ions, or
substituted phosphines. Alternatively, a trinuclear
molybdenum-sulfur halide salt such as
[M'].sub.2[Mo.sub.3S.sub.7A.sub.6], where M' is a counter ion, and
A is a halogen such as Cl, Br, or I, may be reacted with a ligand
source such as a dialkyldithiocarbamate or dialkyldithiophosphate
in the appropriate liquid(s)/solvent(s) to form an oil-soluble
trinuclear molybdenum compound. The appropriate liquid/solvent may
be, for example, aqueous or organic.
[0076] The ligand chosen must have a sufficient number of carbon
atoms to render the compound soluble in the lubricating
composition.
[0077] Trinuclear molybdenum compounds for use in the compositions
of this invention can be those of the formula
Mo.sub.3S.sub.7((alkyl).sub.2dtc).s- ub.4 where the alkyl has about
8 to 18 carbon atoms and the alkyl being preferably a "coco" alkyl
chain which is a mixture of chains of varying even numbers of
carbon atoms from typically a C.sub.8 to C.sub.18 alkyl, mainly
C.sub.10, C.sub.12 and C.sub.14 alkyls derived from coconut
oil.
[0078] Other examples of molybdenum compounds include a sulfurized
molybdenum containing composition prepared by (i) reacting an
acidic molybdenum compound and a basic nitrogen compound selected
from the group consisting of succinimide, a carboxylic acid amide,
a hydrocarbyl monoamine, a phosphoramide, a thiophosphoramide, a
Mannich base, a dispersant viscosity index improver, or a mixture
thereof, in the presence of a polar promoter, to form a molybdenum
complex, and (ii) reacting the molybdenum complex with a
sulfur-containing compound, to thereby form a sulfur- and
molybdenum-containing composition.
[0079] In one embodiment of the present invention, the molybdenum
compound is preferably dinuclear or trinuclear, more preferably
trinuclear.
[0080] In another embodiment of the present invention, the
molybdenum compound, irrespective of its nuclearity, is fully
sulfurised, i.e. the core contains only sulfur as the non-metallic
element, for example Mo.sub.2S.sub.4, Mo.sub.3S.sub.4 and
Mo.sub.3S.sub.7.
[0081] In another embodiment of the present invention, the
molybdenum compound is preferably a dithiocarbamate compound, such
a dinuclear or trinuclear molybdenum dithiocarbamate; especially
effective compounds are molybdenum dialkyldithiocarbamate compounds
represented by the formula
Mo.sub.3S.sub.7((alkyl).sub.2dtc).sub.4.
[0082] Colloidal friction reducers may also be used in the present
invention, such as graphite, borate and molybdenum disulfide that
are present in the oil composition by dispersion.
[0083] The oil composition may contain a mixture of friction
reducers, such as polar compounds that are capable of being
adsorbed on a metal surface, whether organic or organo-metallic,
and molybdenum compounds.
[0084] In an embodiment, the friction reducer is an organic polar
compound having an oleophilic hydrocarbyl chain, such as glycerol
monoleate.
[0085] In another embodiment, the friction reducer is a molybdenum
compound.
[0086] The friction reducers are present in an amount sufficient to
improve the fuel economy of the engine being lubricated. The amount
is typically from 0.01 to 5.0, preferably 0.05 to 1.5, more
preferably 0.1 or 0.15 to 0.5, mass %, based on the mass of the oil
composition.
[0087] In the instance the friction reducer is a molybdenum
compound, the lubricating oil composition preferably contains 5 to
5000, more preferably 10 to 1000, especially 50 to 750, for
example, 75 to 500, ppm of molybdenum by mass, based on the mass of
the oil composition. The amount of molybdenum is measured according
to ASTM D5185.
[0088] Detergent Composition
[0089] Detergents may also be present in lubricating oil
compositions of the present invention.
[0090] A detergent is an additive that reduces formation of piston
deposits, for example high-temperature varnish and lacquer
deposits, in engines; it has acid-neutralising properties and is
capable of keeping finely divided solids in suspension. It is based
on metal "soaps", that is metal salts of organic acids, also known
as surfactants herein.
[0091] A detergent comprises a polar head, i.e. the metal salt of
the organic acid, with a long hydrophobic tail for oil solubility.
Therefore, the organic acids typically have one or more functional
groups, such as OH or COOH or SO.sub.3H; and a hydrocarbyl
substituent.
[0092] Examples of organic acids include sulphonic acids, phenols
and sulphurised derivatives thereof, and carboxylic acids.
[0093] Thus, a detergent composition comprising one or more metal
salts of organic acids may be present, for example, a mixture of
metal sulfonate and metal phenate.
[0094] It has been found that a detergent composition comprising a
metal salt of an aromatic carboxylic acid provides improved
performance.
[0095] A preferred detergent composition comprises more than 50
mole % of a metal salt of an aromatic carboxylic acid, based on the
moles of the metal salts of organic acids in the detergent
composition. Preferably the proportion of the metal salt of an
aromatic carboxylic acid is at least 60 or at least 70 mole %; more
preferably at least 80 or at least 90 mole %, based on the moles of
the metal salts of organic acids in the detergent composition.
[0096] In a most preferred embodiment, the detergent composition
comprises 100 mole % of a metal salt of an aromatic carboxylic
acid, based on the moles of the metal salts of organic acids in the
detergent composition; that is the detergent composition comprises
only aromatic carboxylic acids as the organic acids.
[0097] The aromatic moiety of the aromatic carboxylic acid can
contain heteroatoms, such as nitrogen and oxygen. Preferably, the
moiety contains only carbon atoms; more preferably the moiety
contains six or more carbon atoms; for example benzene is a
preferred moiety.
[0098] The aromatic carboxylic acid may contain one or more
aromatic moieties, such as one or more benzene rings, either fused
or connected via alkylene bridges.
[0099] The carboxylic moiety may be attached directly or indirectly
to the aromatic moiety. Preferably the carboxylic acid group is
attached directly to a carbon atom on the aromatic moiety, such as
a carbon atom on the benzene ring.
[0100] More preferably, the aromatic moiety also contains a second
functional group, such as a hydroxy group or a sulfonate group,
which can be attached directly or indirectly to a carbon atom on
the aromatic moiety.
[0101] Preferred examples of an aromatic carboxylic acids are
salicylic acids and sulphurised derivatives thereof, such as
hydrocarbyl substituted salicylic acid and derivatives thereof.
[0102] Processes for sulfurizing, for example a
hydrocarbyl-substituted salicylic acid, are similar to those used
for phenols, and are well known to those skilled in the art.
[0103] Salicylic acids are typically prepared by carboxylation, for
example, by the Kolbe-Schmitt process, of phenoxides, and in that
case, will generally be obtained, normally in a diluent, in
admixture with uncarboxylated phenol.
[0104] Preferred substituents in oil-soluble salicylic acids are
alkyl substituents. In alkyl-substituted salicylic acids, the alkyl
groups advantageously contain 5 to 100, preferably 9 to 30,
especially 14 to 20, carbon atoms. Where there is more than one
alkyl group, the average number of carbon atoms in all of the alkyl
groups is preferably at least 9 to ensure adequate
oil-solubility.
[0105] The detergent composition can comprise metal salts of
organic acids other than aromatic carboxylic acids, such as
sulfonic acids, phenols and sufurised derivatives thereof, and
carboxylic acids. Such organic acids are described in WO 97/46643,
which is incorporated herein by reference.
[0106] Each or the metal detergent in the detergent composition may
be neutral or overbased, such terms are understood by those skilled
in the art.
[0107] The detergents of the present invention may be salts of one
type of organic acid or salts of more than one type of organic
acids, for example hybrid complex detergents. Preferably, they are
salts of one type of organic acid.
[0108] A hybrid complex detergent is where the basic material
within the detergent is stabilised by more than one type of organic
acid. It will be appreciated by one skilled in the art that a
single type of organic acid may contain a mixture of organic acids
of the same type. For example, a sulfonic acid may contain a
mixture of sulfonic acids of varying molecular weights. Such an
organic acid composition is considered as one type. Thus, complex
detergents are distinguished from mixtures of two or more separate
overbased detergents, an example of such a mixture being one of an
overbased calcium salicylate detergent with an overbased calcium
phenate detergent.
[0109] The art describes examples of overbased complex detergents.
For example, International Patent Application Publication Nos.
97-46643/4/5/6 and 7 describe hybrid complexes made by neutralising
a mixture of more than one acidic organic compound with a basic
metal compound, and then overbasing the mixture. Individual basic
micelles of the detergent are thus stabilised by a plurality of
organic acid types. Examples of hybrid complex detergents include
calcium phenate-salicylate-sulfonate detergent, calcium
phenate-sulfonate detergent and calcium phenate-salicylate
detergent.
[0110] EP-A-0 750 659 describes a calcium salicylate phenate
complex made by carboxylating a calcium phenate and then
sulfurising and overbasing the mixture of calcium salicylate and
calcium phenate. Such complexes may be referred to as
"phenalates"
[0111] Preferred complex detergents are salicylate-based
detergents, for example, a calcium phenate-salicylate-sulfonate
detergent and "phenalates".
[0112] In the instance where more than one type of organic acids is
present in a single detergent, the proportion of any one type of
organic acid to another is not critical, provided the detergent
composition comprises the defined proportion of the metal salt of
an aromatic carboxylic acid.
[0113] For the avoidance of doubt, the detergent composition may
also comprise ashless detergents, i.e. non-metal containing
detergents.
[0114] Preferably the detergent composition comprises at least one
overbased metal detergent.
[0115] A preferred overbased metal detergent comprises one or more
metal salts of aromatic carboxylic acids, preferably one or more
metal salts of salicylic acids.
[0116] Group 1 and Group 2 metals are preferred as metals in the
detergents; more preferably calcium and magnesium, especially
calcium is preferred.
[0117] Detergent compositions comprising at least one calcium
salicylate-based detergent, preferably at least one overbased
calcium salicylate-based detergent, have been found to be
particularly effective in the present invention.
[0118] Applicant, therefore, considers that detergent compositions
comprising only calcium salicylate-based detergents, whether
neutral or overbased, would be advantageous.
[0119] Preferably, the detergent composition is present in the oil
composition in an amount, based on surfactant content, of at least
5, preferably at least 10, such as at least 20 or at least 30, more
preferably at least 50, most especially at most 75, millimoles of
surfactant per kilogram of the oil composition (mmol/kg). In an
embodiment, the amount of detergent composition, based on
surfactant content, in the oil composition is 10 to 15 mmol/kg.
[0120] Means for determining the amount of surfactant and the
amount of metal salt of an aromatic carboxylic acid are known to
those skilled in the art. For example, a skilled person can
calculate the amounts in the final lubricating oil composition from
information concerning the amount of raw materials (e.g. organic
acids) used to make the detergent(s) and from information
concerning the amount of detergent(s) used in the final oil
composition. Analytical methods (e.g. potentiometric titration and
chromatography) can also be used to determine the amounts of
surfactant and metal salt of an aromatic carboxylic acid.
[0121] It will be appreciated by a skilled person in the art that
the methods to determine the amount of metal salts of organic acids
(also known as surfactants), including the amount of metal salts of
aromatic carboxylic acids, are at best approximations and that
differing methods will not always give exactly the same result;
they are, however, sufficiently precise to allow the practice of
the present invention.
[0122] Dispersant Additive
[0123] Dispersant additives maintain oil-insoluble substances,
resulting from oxidation during use, in suspension in the fluid,
thus preventing sludge flocculation and precipitation or deposition
on metal parts. So-called ashless dispersants are organic materials
which form substantially no ash on combustion, in contrast to
metal-containing (and thus ash-forming) detergents. Borated
metal-free dispersants are also regarded herein as ashless
dispersants. Suitable dispersants include, for example, derivatives
of long chain hydrocarbyl-substituted carboxylic acids, in which
the hydrocarbyl group has a number average molecular weight of less
than 15,000, such as less than 5000; examples of such derivatives
being derivatives of high molecular weight hydrocarbyl-substituted
succinic acid. Such hydrocarbyl-substituted carboxylic acids may be
reacted with, for example, a nitrogen-containing compound,
advantageously a polyalkylene polyamine, or with an alcohol.
Particularly preferred dispersants are the reaction products of
polyalkylene amines with alkenyl succinic anhydrides. Examples of
specifications disclosing dispersants of the last-mentioned type
are U.S. Pat. Nos. 3,202,678, 3,154,560, 3,172,892, 3,024,195,
3,024,237, 3,219,666, 3,216,936 and BE-A-662 875.
[0124] Alternatively or in addition, dispersancy may be provided by
polymeric compounds capable of providing viscosity index improving
properties and dispersancy, such compounds are known as
multifunctional viscosity index improvers. Such polymers differ
from conventional viscosity index improvers in that they provide
performance properties, such as dispersancy and/or antioxidancy, in
addition to viscosity index improvement.
[0125] Dispersant olefin copolymers and dispersant
polymethacrylates are examples of multifunctional viscosity index
improvers. Multifunctional viscosity index improvers are prepared
by chemically attaching various functional moieties, for example
amines, alcohols and amides, onto polymers, which polymers
preferably tend to have a number average molecular weight of at
least 15,000, such in the range from 20,000 to 600,000, as
determined by gel permeation chromatography or light scattering
methods. The polymers used may be those described above with
respect to viscosity modifiers. Therefore, amine molecules may be
incorporated to impart dispersancy and/or antioxidancy
characteristics, whereas phenolic molecules may be incorporated to
improve antioxidant properties. A specific example, therefore, is
an inter-polymer of ethylene-propylene post grafted with an active
monomer such as maleic anhydride and then derivatized with, for
example, an alcohol or amine.
[0126] EP-A-24146 and EP-A-0 854 904 describe examples of
dispersants and dispersant viscosity index improvers, which are
accordingly incorporated herein.
[0127] Heavy duty diesel engine lubricating oil compositions tend
to require higher amount of dispersant than for example a passenger
car engine oil composition because more oil-insoluble substances,
such as soot, are formed in heavy duty diesel engines. Accordingly,
the amount of a dispersant additive, whether in the form of a
dispersant additive and/or a multifunctional viscosity index
improver additive, in a heavy duty diesel engine lubricating oil
composition is, based on nitrogen, preferably at least 0.06, more
preferably at least 0.09, especially at least 0.12, mass %, based
on the mass of the oil composition. The amount of nitrogen derived
from the dispersant tends not to be more than 0.2 mass %.
[0128] In every instance the oil composition has an amount of
phosphorus less than 0.09 mass %, based on the mass of the oil
composition, and the oil composition does not contain a dispersant
viscosity index improver additive, the amount of nitrogen in the
oil composition is preferably at least 0.045, more preferably 0.5,
such at least 0.055, advantageously at least 0.06, especially at
least 0.065, such as at least 0.08, for example, at least 0.1, mass
%, based on the mass of the oil composition. The amount of nitrogen
is preferably at most 0.3, such as at most 0.25 or at most 0.2,
mass %, based on the mass of the oil composition. The amount of
nitrogen is measured according to ASTM D4629. Preferably, the
amount of nitrogen is derived from a dispersant additive, such as a
polyisobutenyl succinimide. In the event a dispersant viscosity
index improver additive is present in the lubricating oil
composition, then amount of nitrogen can be lower than 0.045 mass
%, for example, from 0.001 to 0.04 mass % based on the mass of the
oil composition. In a preferred embodiment, the amount of nitrogen,
irrespective of whether the oil composition contains dispersant
viscosity index improver additive or not, is at least 0.045 mass %.
In the instance the oil composition contains a dispersant viscosity
index improver additive, the amount of the additive is preferably
0.01 to 5, preferably 0.05 to 3, especially 0.1 to 2, mass %, based
on the mass of the oil composition.
[0129] Co-Additives
[0130] Other additives may also be present in the oil composition
of the present invention.
[0131] Co-additives suitable in the present invention include
viscosity index improvers, corrosion inhibitors, other oxidation
inhibitors or antioxidants, rust inhibitors or rust prevention
agents, anti-wear agents, pour point depressants, demulsifiers, and
anti-foaming agents.
[0132] Viscosity index improvers (or viscosity modifiers) impart
high and low temperature operability to a lubricating oil and
permit it to remain shear stable at elevated temperatures and also
exhibit acceptable viscosity or fluidity at low temperatures.
Suitable compounds for use as viscosity modifiers are generally
high molecular weight hydrocarbon polymers, including polyesters,
such as polymethacrylates; poly(ethylene-co-propylene) polymers and
closely related modifications (so called olefin copolymers);
hydrogenated poly(styrene-co-butadiene or -isoprene) polymers and
modifications; and esterified poly(styrene-co-maleic anhydride)
polymers. Oil-soluble viscosity modifying polymers generally have
number average molecular weights of at least 15,000 to 1,000,000,
preferably 20,000 to 600,000, as determined by gel permeation
chromatography or light scattering methods. The disclosure in
Chapter 5 of "Chemistry & Technology of Lubricants", edited by
R. M. Mortier and S. T. Orzulik, First edition, 1992, Blackie
Academic & Professional, is incorporated herein.
[0133] Corrosion inhibitors reduce the degradation of metallic
parts contacted by the lubricating oil composition. Thiadiazoles,
for example those disclosed in U.S. Pat. Nos. 2,719,125, 2,719,126
and 3,087,932 are examples of corrosion inhibitors for lubricating
oils.
[0134] Oxidation inhibitors, or antioxidants, reduce the tendency
of mineral oils to deteriorate in service, evidence of such
deterioration being, for example, the production of varnish-like
deposits on metal surfaces and of sludge, and viscosity increase.
Suitable oxidation inhibitors include sulfurized alkyl phenols and
alkali or alkaline earth metal salts thereof; hindered phenols;
diphenylamines; phenyl-naphthylamines; and phosphosulfurized or
sulfurized hydrocarbons.
[0135] Other oxidation inhibitors or antioxidants which may be used
in lubricating oil compositions include oil-soluble copper
compounds. The copper may be blended into the oil as any suitable
oil-soluble copper compound. By oil-soluble it is meant that the
compound is oil-soluble under normal blending conditions in the oil
or additive package. The copper may, for example, be in the form of
a copper dihydrocarbyl thio- or dithio-phosphate. Alternatively,
the copper may be added as the copper salt of a synthetic or
natural carboxylic acid, for example, a C.sub.8 to C.sub.18 fatty
acid, an unsaturated acid, or a branched carboxylic acid. Also
useful are oil-soluble copper dithiocarbamates, sulfonates,
phenates, and acetylacetonates. Examples of particularly useful
copper compounds are basic, neutral or acidic copper Cu.sup.I
and/or Cu.sup.II salts derived from alkenyl succinic acids or
anhydrides.
[0136] Copper antioxidants will generally be employed in an amount
of from about 5 to 500 ppm by weight of the copper, in the final
lubricating composition.
[0137] Rust inhibitors selected from the group consisting of
nonionic polyoxyalkylene polyols and esters thereof,
polyoxyalkylene phenols, and anionic alkyl sulfonic acids may be
used.
[0138] Antiwear agents, as their name implies, reduce wear of metal
parts. Zinc dihydrocarbyl dithiophosphates (ZDDPs) are very widely
used as antiwear agents. Examples of ZDDPs for use in oil-based
compositions are those of the formula
Zn[SP(S)(OR.sup.1)(OR.sup.2)].sub.2 wherein R.sup.1 and R.sup.2
contain from 1 to 18, and preferably 2 to 12, carbon atoms.
[0139] Sulfur- and molybdenum-containing compounds are also
examples of anti-wear additives. Also suitable are ashless
phosphorus- and sulfur-containing compounds.
[0140] Pour point depressants, otherwise known as lube oil flow
improvers, lower the minimum temperature at which the fluid will
flow or can be poured. Such additives are well known. Foam control
may be provided by an antifoamant of the polysiloxane type, for
example, silicone oil or polydimethyl siloxane.
[0141] A small amount of a demulsifying component may be used. A
preferred demulsifying component is described in EP-A-0 330 522. It
is obtained by reacting an alkylene oxide with an adduct obtained
by reacting a bis-epoxide with polyhydric alcohol.
[0142] Some of the above-mentioned additives may provide a
multiplicity of effects; thus for example, a single additive may
act as a dispersant-oxidation inhibitor. This approach is well
known and need not be further elaborated herein.
[0143] Preferably an anti-wear additive, such a metal
dihydrocarbyldithiophosphate, for example, zinc
dihydrocarbyidithiophosph- ate, is present in the lubricating oil
compositions of the present invention.
[0144] When lubricating compositions contain one or more of the
above-mentioned additives, including the detergents, each additive
is typically blended into the base oil in an amount which enables
the additive to provide its desired function. Representative
effective amounts of such additives, when used in lubricants, are
as follows:
1 Mass % a.i.* Mass % a.i.* Additive (Broad) (Preferred) Viscosity
Modifier 0.01-6 0.01-4 Corrosion Inhibitor 0.01-5 0.01-1.5
Oxidation Inhibitor 0.01-5 0.01-1.5 Friction Reducer 0.01-5
0.01-1.5 Dispersant 0.1-20 0.1-8 Dispersant Viscosity Modifier
0.01-5 0.05-5 Detergent 0.01-6 0.01-3 Anti-wear Agent 0.01-6 0.01-4
Pour Point Depressant 0.01-5 0.01-1.5 Rust Inhibitor 0.001-0.5
0.01-0.2 Anti-Foaming Agent 0.001-0.3 0.001-0.15 Demulsifier
0.001-0.5 0.01-0.2 *Mass % active ingredient based on the final
lubricating oil composition.
[0145] The additives may be incorporated into a base oil in any
convenient way. Thus, each of the additive can be added directly to
the oil by dispersing or dissolving it in the oil at the desired
level of concentration. Such blending may occur at ambient
temperature or at an elevated temperature.
[0146] When a plurality of additives are employed it may be
desirable, although not essential, to prepare one or more additive
packages (also known as additive compositions or concentrates)
comprising the additives, whereby several additives, with the
exception of viscosity modifiers, multifuntional viscosity
modifiers and pour point depressants, can be added simultaneously
to the base oil to form the lubricating oil composition.
Dissolution of the additive package(s) into the lubricating oil may
be facilitated by diluent or solvents and by mixing accompanied
with mild heating, but this is not essential. The additive
package(s) will typically be formulated to contain the additive(s)
in proper amounts to provide the desired concentration in the final
formulation when the additive package(s) is/are combined with a
predetermined amount of basestock. The nitrogen content of such an
additive concentrate is generally in the range of 0.5 to 1.5,
preferably in the range of 0.7 to 1.0, mass %, based on the mass of
the additive concentrate. Thus, one or more detergents may be added
to small amounts of base oil or other compatible solvents (such as
a carrier oil or diluent oil) together with other desirable
additives to form additive packages containing active ingredients
in an amount, based on the additive package, of, for example, from
2.5 to 90 mass %, and preferably from 5 to 75 mass %, and most
preferably from 8 to 60 mass %, of additives in the appropriate
proportions with the remainder being diluent. The final
formulations may typically contain 5 to 40 mass % of the additive
package(s), the remainder being diluent.
[0147] The amount of additives in the final lubricating oil
composition is generally dependent on the type of the oil
composition, for example, a heavy duty diesel engine lubricating
oil composition has 2 to 20, preferably 5 to 18, more preferably 7
to 16, such as 8 to 14, mass % of additives based on the mass of
the oil composition.
[0148] Thus, a method of preparing the oil composition according to
the present invention can involve admixing an oil of lubricating
viscosity and one or more of the defined compounds or an additive
package that comprises one or more of the defined compounds.
[0149] It should be appreciated that interaction may take place
between any two or more of the additives, including any two or more
detergents, after they have been incorporated into the oil
composition. The interaction may take place in either the process
of mixing or any subsequent condition to which the composition is
exposed, including the use of the composition in its working
environment. Interactions may also take place when further
auxiliary additives are added to the compositions of the invention
or with components of oil. Such interaction may include interaction
which alters the chemical constitution of the additives. Thus, the
compositions of the invention include compositions in which
interaction, for example, between any of the additives, has
occurred, as well as compositions in which no interaction has
occurred, for example, between the components mixed in the oil.
[0150] In this specification:
[0151] The term "comprising" or "comprises" when used herein is
taken to specify the presence of stated features, integers, steps
or components, but does not preclude the presence or addition of
one or more other features, integers, steps, components or groups
thereof.
[0152] The term "oil-soluble" or "oil-dispersible", as used herein,
does not mean that the additives are soluble, dissolvable, miscible
or capable of being suspended in the oil in all proportions. They
do mean, however, that the additives are, for instance, soluble or
stable dispersible in the oil to an extent sufficient to exert
their intended effect in the environment in which the oil
composition is employed. Moreover, the additional incorporation of
other additives such as those described above may affect the
solubility or dispersibility of the additives.
[0153] "Major amount" means in excess of 50 mass % of the
composition.
[0154] "Minor amount" means less than 50 mass % of the composition,
both in respect of the stated additive and in respect of the total
mass % of all of the additives present in the composition, reckoned
as active ingredient of the additive or additives.
[0155] "TBN" is Total Base Number as measured by ASTM D2896.
[0156] All percentages reported are mass % on an active ingredient
basis, i.e., without regard to carrier or diluent oil, unless
otherwise stated.
[0157] The abbreviation SAE stands for Society of Automotive
Engineers, who classify lubricants by viscosity grades.
[0158] The invention is illustrated by, but in no way limited to,
the following examples.
EXAMPLES
[0159] Lubricating oil compositions were blended by known methods
so that each composition was an SAE 5W30 lubricating oil
composition. Each oil composition comprised a detergent composition
containing salicylate detergents; a zinc dihydrocarbyl
dithiophosphate; and a borated dispersant. Thus, each oil
composition was comparable to one another because they contained
identical additives with the exception of Example 1 and Example 2,
which also contained a friction reducer: Example 1 contained as a
friction reducer a glycerol monoleate in an amount of 0.3 mass %,
while Example 2 contained as a friction reducer a trinuclear
molybdenum dithiocarbamate in an amount of 450 ppm of
molybdenum.
[0160] The lubricating oil compositions (Comparative Example A,
Example 1 and Example 2) were tested for fuel economy in a total
driveline rig which comprised a Volvo FH-12 litre heavy duty diesel
engine, together with a transmission including a gearbox and an
axle.
[0161] The rig is based upon extensive use of electronic engine
management systems, which allows the connection of transmission and
to a certain degree transaxles via CAN (Controlled Area Network) as
a total driveline rig. This rig is described in "Neues
F&E-Zentrum fur Antriebsstrang-Schmierung" by Peter Ahrweiler
and Gerd Rentel, ATZ Automobiletechnische Zeitschrift, 100 (1998),
3, pages 202-209. One of the major benefits of the total driveline
rig is in the form of reduced error of measurement of heavy duty
diesel fuel economy. Removal of error sources associated with fleet
trials such as driver variation, tyre pressure variation, drive
cycle variation and aerodynamic variation is essential if accurate
fuel economy measurements are to be made. This is now possible
using the total driveline rig. Historical data has shown that fuel
economy measurements of greater than 0.29% are real at the 95%
confidence interval.
[0162] The fuel economy measurements are quoted as an improvement,
in percentage, compared to a lubricating oil composition having the
same additive components as Comparative Example A, but blended to
an SAE 15W40 grade.
[0163] Table 1 summarises the results obtained and shows that the
use of friction reducers in heavy duty diesel engine lubricating
oil compositions provides an improvement in the fuel economy of the
engine: the improvement is about double that achieved by the oil
composition not containing a friction reducer (compare Comparative
Example A with Example 1 or Example 2). Table 1 also provides
certain properties of the oil compositions.
2 TABLE 1 Comparative Example A Example 1 Example 2 SAE J300
classification 5W30 5W30 5W30 Phosphorus, % mass 0.12 0.13 0.12
(ASTM D5185) Sulfur, % mass (ASTM D5185) 0.33 0.34 0.41 Nitrogen,
mass % 0.10 0.10 0.11 Base blend 8.83 8.80 8.89 viscosity
@100.degree. C., mm.sup.2s.sup.-1 Improvement in Fuel Economy
0.69.sup.2 1.50 1.35 1 - percentage improvement in fuel economy
relative to a lubricating oil composition blended to an SAE 15W40
grade; 2 - average of two measurements
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