U.S. patent application number 12/419609 was filed with the patent office on 2009-10-01 for grease composition for use in constant velocity joints comprising at least one tri-nuclear molybdenum compound.
Invention is credited to Jisheng E, Frank Reher, Stefanie Rosenkranz.
Application Number | 20090247435 12/419609 |
Document ID | / |
Family ID | 37726859 |
Filed Date | 2009-10-01 |
United States Patent
Application |
20090247435 |
Kind Code |
A1 |
E; Jisheng ; et al. |
October 1, 2009 |
GREASE COMPOSITION FOR USE IN CONSTANT VELOCITY JOINTS COMPRISING
AT LEAST ONE TRI-NUCLEAR MOLYBDENUM COMPOUND
Abstract
To solve the problem to provide for a new grease composition
giving low wear and low friction primarily to constant velocity
joints, a grease composition is suggested comprising a) a base oil
composition; and b) 0.25% by weight to 5% by weight of at least one
tri-nuclear molybdenum corn pound of the formula
Mo.sub.3SkL.sub.nQ.sub.z wherein L are independently selected
ligands having organo groups with a sufficient number of carbon
atoms to render the compound soluble or dispersible in the oil, n
is from 1 to 4, k varies from 4 though 7, Q is selected from the
group of neutral electron donating compounds such as amines,
alcohols, phosphines, and ethers, and z ranges from 0 to 5 and
includes non-stoichiometric values.
Inventors: |
E; Jisheng; (Hennef, DE)
; Reher; Frank; (Siegburg, DE) ; Rosenkranz;
Stefanie; (Wachtberg, DE) |
Correspondence
Address: |
GKN Driveline/TTG
c/o Kristin L. Murphy, 39533 Woodward Avenue, suite 140
Bloomfield Hills
MI
48304
US
|
Family ID: |
37726859 |
Appl. No.: |
12/419609 |
Filed: |
April 7, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP2006/009716 |
Oct 7, 2006 |
|
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|
12419609 |
|
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Current U.S.
Class: |
508/166 ;
508/172; 508/362; 508/370; 508/379; 508/382 |
Current CPC
Class: |
C10N 2030/76 20200501;
C10M 2205/0206 20130101; C10N 2010/12 20130101; C10M 2223/045
20130101; C10M 2215/1026 20130101; C10N 2010/02 20130101; C10N
2050/10 20130101; C10N 2040/046 20200501; C10M 2207/2805 20130101;
C10N 2010/04 20130101; C10M 2203/1065 20130101; C10M 159/18
20130101; C10M 169/06 20130101; C10M 2203/1025 20130101; C10M
2207/106 20130101; C10M 2227/09 20130101; C10N 2030/06 20130101;
C10M 2219/068 20130101 |
Class at
Publication: |
508/166 ;
508/382; 508/379; 508/362; 508/370; 508/172 |
International
Class: |
C10M 125/22 20060101
C10M125/22; C10M 139/06 20060101 C10M139/06; C10M 137/10 20060101
C10M137/10; C10M 125/10 20060101 C10M125/10 |
Claims
1. A grease composition for use in constant velocity joints
comprising a) a base oil composition; and b) 0.25% by weight to 5%
by weight of at least one tri-nuclear molybdenum compound of the
formula Mo.sub.3S.sub.kL.sub.nQ.sub.z, wherein L are independently
selected ligands having organo groups with a sufficient number of
carbon atoms to render the compound soluble or dispersible in the
oil, n is from 1 to 4, k varies from 4 though 7, Q is selected from
the group of neutral electron donating compounds consisting of
amines, alcohols, phosphines, and ethers, and z ranges from 0 to 5
and includes non-stoichiometric values.
2. A grease composition according to claim 1, further comprising at
least one zinc compound additive.
3. A grease composition according to claim 2, comprising at least
one zinc compound additive in an amount of between 0.1% by weight
to 2.5% by weight, referred to the total amount of the
composition.
4. A grease composition according to claim 3 where the zinc
compound is at least one selected from the group consisting of zinc
dithiophosphates, zinc dithiocarbamates, zinc oxide, and zinc
sulfide.
5. A grease composition according to claim 1, further comprising a
thickener selected from the group consisting of lithium soaps,
calcium soaps, lithium-complex soaps, calcium-complex soaps,
urea-derivative type thickener, and mixtures thereof.
6. A grease composition according to claim 1, characterised in that
the base oil composition comprises at least one of
poly-[alpha]-olefins, naphthenic oils, paraffinic oils, and
synthetic organic esters.
7. A grease composition according to claim 1, further comprising an
additive package selected from the group of agents consisting of
anti-oxidation agents, corrosion inhibitors, anti-wear agents,
friction modifiers, and/or extreme pressure agents, and mixtures
thereof.
8. A grease composition according to claim 1, comprising 55% by
weight to 97.5% by weight of the base oil composition, 0.3% by
weight to 3% by weight of at least one tri-nuclear molybdenum
compound, 0.1% by weight to 1.5% by weight of at least one zinc
compound additive, and between 2% and 25% by weight of at least one
thickener in each case referred to the total amount of the grease
composition.
9. A grease composition according to claim 1, characterised in that
the sliding friction coefficient of the grease composition is not
more than 0.1.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of International
Application No. PCT/EP2006/009716 filed Oct. 7, 2006 which is
hereby incorporated by reference in its entirety.
FIELD
[0002] The present invention relates to a lubricating grease which
is intended primarily for use in constant velocity universal
joints, especially ball joints or tripod joints, which are used in
the drivelines of motor vehicles.
BACKGROUND
[0003] The motions of components within constant velocity joints
(CVJ) are complex with a combination of rolling, sliding and
spinning. When the joints are under torque, the components are
loaded together which can not only cause wear on the contact
surfaces of the components, but also rolling contact fatigue and
significant frictional forces between the surfaces. The wear can
result in failure of the joints and the frictional forces can give
rise to noise, vibration and harshness (NVH) in the driveline. NVH
is normally "measured" by determining the axial forces generated in
plunging type CVJ. Ideally the greases used in constant velocity
joints need not only to reduce wear, but also have to have a low
coefficient of friction to reduce the frictional forces and to
reduce or prevent NVH.
[0004] Constant velocity joints also have sealing boots of
elastomeric material which are usually of bellows shape, one end
being connected to the outer part of the CVJ and the other end to
the interconnecting or output shaft of the CVJ. The boot retains
the grease in the joint and keeps out dirt and water.
[0005] Not only must the grease reduce wear and friction and
prevent the premature initiation of rolling contact fatigue in a
CVJ, it must also be compatible with the elastomeric material of
which the boot is made. Otherwise there is a degradation of the
boot material which causes premature failure of the boot, allowing
the escape of the grease and ultimately failure of the CVJ. The two
main types of material used for CVJ boots are polychloroprene
rubber (CR) and thermoplastic elastomer (TPE), especially
ether-ester block co-polymer thermoplastic elastomer (TPC-ET).
[0006] Typical CVJ greases have base oils which are blends of
naphthenic (saturated rings) and paraffinic (straight and branched
saturated chains) mineral oils. Synthetic oils may also be added.
It is known that said base oils have a large influence on the
deterioration (swelling or shrinking) of both boots made of CR and
TPC-ET. Both mineral and synthetic base oils extract the
plasticisers and other oil soluble protective agents from the boot
materials. Paraffinic mineral oils and poly-.alpha.-olefin (PAO)
synthetic base oils diffuse very little into especially boots made
of rubber material causing shrinkage, but on the other hand
naphthenic mineral oils and synthetic esters diffuse into boot
materials and act as plasticisers and can cause swelling. The
exchange of plasticiser or plasticiser compositions for the
naphthenic mineral oil can significantly reduce the boot
performance, especially at low temperatures, and may cause the boot
to fail by cold cracking, ultimately resulting in failure of the
CVJ. If significant swelling or softening occurs, the maximum high
speed capability of the boot is reduced due to the poor stability
at speed and/or excessive radial expansion.
[0007] In order to solve the aforesaid problems, U.S. Pat. No.
6,656,890 B1 suggests a special base oil combination comprising 10
to 35% by weight of one or more poly-.alpha.-olefins, 3 to 15% by
weight of one or more synthetic organic esters, 20 to 30% by weight
of one or more naphthenic oils, the remainder of the combination
being one or more paraffinic oils, and, further, a lithium soap
thickener, and a sulphur-free friction modifier, that may be a
organo-molybdenum complex, and molybdenum dithiophosphate, and a
zinc dialkyldithio-phosphate and further additives such as
corrosion inhibitors, anti-oxidants, extreme pressure additives,
and tackiness agents. However, the friction coefficient and the
wear of grease compositions according to U.S. Pat. No. 6,656,890 B1
as measured in SRV (abbreviation for the German words Schwingungen,
Reibung, Verschlei.beta.) tests needs to be improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1a is a graph of friction coefficient data for a grease
embodiment of the present invention and several greases with
commercial organic molybdenum containing additives;
[0009] FIG. 1b is a graph of wear data for a grease embodiment of
the present invention and several greases with commercial organic
molybdenum containing additives;
[0010] FIG. 2a is a graph of friction coefficient data for several
grease composition embodiments of the present invention and several
grease compositions with differing levels of tri-nuclear molybdenum
compounds containing sulfur (TNMoS);
[0011] FIG. 2b graph of wear data for several grease composition
embodiments of the present invention and several grease
compositions with differing levels of tri-nuclear molybdenum
compounds containing sulfur (TNMoS);
[0012] FIG. 3a is a graph of friction coefficient data for several
grease composition embodiments of the present invention with
varying levels of a zinc compound additive;
[0013] FIG. 3b is a graph of wear data for several grease
embodiments of the present invention with varying levels of a zinc
compound additive;
[0014] FIG. 4a is a graph of friction coefficient data for several
different grease composition embodiments of the present invention
with zinc compound additives and varying levels of an extreme
pressure agent and varying levels of an additional sulfur
containing compound;
[0015] FIG. 4b is a graph of wear data for several different grease
composition embodiments of the present invention with zinc compound
additives and varying levels of an extreme pressure agent and
varying levels of an additional sulfur containing compound;
[0016] FIG. 5a is a graph of friction coefficient data for grease
composition embodiments of the present invention and grease
compositions lacking tri-nuclear molybdenum compounds containing
sulfur (TNMoS) with varying amounts of thickeners; and
[0017] FIG. 5b is graph of wear data for grease composition
embodiments of the present invention and grease compositions
lacking tri-nuclear molybdenum compounds containing sulfur (TNMoS)
with varying amounts of thickeners.
DETAILED DESCRIPTION
[0018] Thus, it is the object of the present invention to provide
for a grease composition, primarily for use in constant velocity
joints, which has a good compatibility with boots made of rubber or
thermoplastic elastomer, and which also gives low wear and low
friction in use in CVJ.
[0019] Said object of the present invention is solved by a grease
composition for use in constant velocity joints comprising
[0020] a) a base oil composition; and
[0021] b) 0.25% by weight to 5% by weight, preferably 0.3% by
weight to 3% by weight, referred to the total amount of the grease
composition, of at least one tri-nuclear molybdenum compound of the
formula
M.sub.O3S.sub.kL.sub.nQ.sub.z,
[0022] wherein L are independently selected ligands having organo
groups with a sufficient number of carbon atoms to render the
compound soluble or dispersible in the oil, n is from 1 to 4, k
varies from 4 though 7, Q is selected from the group of neutral
electron donating compounds such as amines, alcohols, phosphines,
and ethers, and z ranges from 0 to 5 and includes
non-stoichiometric values.
[0023] The number of carbon atoms present in the tri-nuclear
molybdenum compound among all the ligands, organo groups is at
least 21 carbon atoms, preferably at least 25, more preferably at
least 30, and most preferably at least 35. Tri-nuclear molybdenum
compounds usable in the present invention are disclosed in U.S.
Pat. No. 6,172,013 B1, the disclosure of which is incorporated in
the present invention insofar by reference. The inventors of the
present invention have found that the presence of at least 0.25% by
weight of the tri-nuclear molybdenum compound according to claim 1
would significantly lower the friction coefficient as well as the
wear of CVJ in use. Surprisingly, the presence of 0.2% by weight or
less of the tri-nuclear molybdenum compound would not lead to a
much lowered friction coefficient nor to a lower wear when used in
CVJs.
[0024] As a base oil composition according to the present
invention, a base oil composition as disclosed in U.S. Pat. No.
6,656,890 B1, the disclosure of which is incorporated insofar
herein by reference, may preferably be used. However, any further
kind of base oil composition, especially a blend of mineral oils, a
blend of synthetic oils or a blend of a mixture of mineral and
synthetic oils may be used. The base oil composition should
preferably have a kinematic viscosity of between about 32 and about
250 mm.sup.2/s at 40.degree. C. and between about and about 25
mm.sup.2/s at 100.degree. C. The mineral oils preferably are
selected from the group comprising at least one naphthenic oil
and/or at least one paraffinic oil. The synthetic oils usable in
the present invention are selected from a group comprising at least
one poly-.alpha.-olefin (PAO) and/or at least one synthetic organic
ester. The organic synthetic ester is preferably a di-carboxylic
acid derivative having subgroups based on aliphatic alcohols.
Preferably, the aliphatic alcohols have primary, straight or
branched carbon chains with 2 to 20 carbon atoms. Preferably, the
organic synthetic ester is selected from a group comprising sebacic
acid-bis(2-ethylhexylester) ("dioctyl sebacate" (DOS)), adipaic
acid-bis-(2-30 ethylhexylester) ("dioctyl adipate" (DOA)), and/or
azelaic acid-bis(2-ethylhexylester) ("dioctyl azelate (DOZ)).
[0025] If poly-.alpha.-olefin is present in the base oil
composition, preferably poly-.alpha.-olefins are selected having a
viscosity in a range from about 2 to about 40 centistokes at
100.degree. C. Naphthenic oils selected for the base oil
compositions have preferably a viscosity in a range between 20 to
180 mm.sup.2/s at 40.degree. C., whereas if paraffinic oils were
present in the base oil composition, preferably the paraffinic oils
have a viscosity in a range between about 25 to about 400
mm.sup.2/s at 40.degree. C.
[0026] In a further embodiment of the present invention, the grease
composition further comprises at least one zinc compound additive,
more preferably a zinc compound additive in an amount of about 0.1%
by weight to about 1.5% by weight. Most preferred the zinc compound
additive is selected from the group comprising at least one of zinc
dithiophosphates (ZnDTP) and/or zinc dithiocarbamates (ZnDTC), ZnO
and/or ZnS. The zinc dithiophosphate is preferably selected from
the group of zinc dialkyldithiophosphate of the following general
formula:
(R.sup.1O)(R.sup.2O)SP--S--Zn--S--PS(OR.sup.3)(OR.sup.4)
wherein each of R.sup.1 to R.sup.4 inclusive may be the same or
different and each represents a primary or secondary alkyl group
having 1 to 24, preferably 3 to 20, most preferably 3 to 5 carbon
atoms. In particular, excellent effects can be expected if the
substituents R.sup.1, R.sup.2, R.sup.3 and R.sup.4 represent a
combination of primary and secondary alkyl groups, each having 3 to
8 carbon atoms.
[0027] The zinc dithiocarbamate may be preferably selected from
zinc dialkyldithiocarbamate of the following general formula:
##STR00001##
wherein R.sup.5, R.sup.6, R.sup.7, and R.sup.8 may be same or
different and each represents an alkyl group having 1 to 24 carbon
atoms or an aryl group having 6 to 30 carbon atoms.
[0028] By adding at least one zinc compound additive to the grease
composition according to the invention, the friction coefficient as
well as the wear in CVJ are diminished further significantly.
[0029] According to another embodiment of the invention, the grease
composition further comprises a thickener selected from the group
comprising lithium soaps, calcium soaps, lithium complex soaps,
calcium complex soaps, and/or urea-derivative type thickener. The
urea-derivative type thickener is not restricted to specific ones
and maybe, for instance, also a diurea compound and/or a polyurea
compound.
[0030] In the sense of the present invention, a lithium soap or a
calcium soap is a reaction product of at least one fatty acid with
lithium hydroxide or calcium hydroxide. Preferably, the thickener
may be a simple lithium or calcium soap formed from stearic acid,
12-hydroxy stearic acid, hydrogenated castor oil or from other
similar fatty acids or mixtures thereof or methylesters of such
acids. Alternatively, a lithium and/or calcium complex soap may be
used formed for example from a mixture of long-chained fatty acids
together with a complexing agent, for example a borate of one or
more dicarboxylic acids or a mixture of short and/or medium chained
carboxylic acids. The use of complex lithium and/or calcium soaps
allows the grease composition according to the present invention to
operate up to a temperature of about 180.degree. C., whereas with
simple lithium and/or calcium soaps, the grease composition will
only operate up to a temperature of about 120.degree. C. However,
mixtures of all of the aforesaid thickeners may also be used.
[0031] According to a further embodiment of the present invention,
the grease composition further comprises an additive package
selected from the group of agents comprising antioxidation agents,
corrosion inhibitors, anti-wear agents, friction modifiers, and/or
extreme pressure agents (EP agents).
[0032] The EP agent is preferably a metal-free, sulphurised fatty
acid methyl ester agent with a viscosity of about 25 mm.sup.2/s at
40.degree. C. being present preferably in an amount between about
0.1 to about 3% by weight, referred to the total amount of the
grease composition. The total sulphur amount of the EP agent
preferably ranges from about 8 to about 10% by weight and the
active sulphur amount is about 1% by weight. Such EP agents exhibit
excellent effects with respect to the prevention of seizure of CVJ.
If the sulphur content exceeds the upper limit defined above, it
may promote the initiation of rolling contact fatigue and wear of
the contacting metal components.
[0033] As an anti-oxidation agent, the grease composition of the
present invention may comprise an amine, preferably an aromatic
amine, more preferably phenyl-a-naphthylamine or diphenylamine or
derivatives thereof. The anti-oxidation agent is used to prevent
deterioration of the grease composition associated with oxidation.
The grease composition according to the present invention may range
between about 0.1 to about 2% by weight, referred to the total
amount to the grease composition, of an anti-oxidant agent in order
to inhibit the oxidation degradation of the base oil, as well as to
lengthen the life of the grease composition, thus prolonging the
life of the CVJ.
[0034] Typically, the last operation before the assembly of CVJ is
a wash to remove machining debris, and it is therefore necessary
for the grease to absorb any traces of remaining water and to
prevent the water from causing corrosion and adversely effecting
the performance of the CVJ, it is therefore necessary to add a
corrosion inhibitor. As a corrosion inhibitor, the grease
composition according to the present invention may comprise at
least one metal salt selected from the group consisting of metal
salts of oxidised waxes, metal salts of petroleum sulphonates,
especially prepared by sulphonating aromatic hydrocarbon components
present in fractions of lubricating oils, and/or metal salts of
alkyl aromatic sulphonates, such as dinonylnaphthalene sulphonic
acids, alkylbenzene sulphonic acids, or overbased alkylbenzene
sulphonic acids. Examples of the metal salts include sodium salts,
potassium salts, calcium salts, magnesium salts, zinc salts, and
quaternary ammonium salts, the calcium salts being most preferred.
Calcium salts of oxidised waxes also ensure an excellent
effect.
[0035] Anti-wear agents according to the present invention prevent
a metal-to-metal contact by adding film-forming compounds to
protect the surface either by physical absorption or chemical
reaction. ZnDTP-compounds may also be used as anti-wear agents. As
anticorrosion agents according to the present invention preferably
calciumsulfonate salts are used, preferably an amount between about
0.5 to about 3% by weight, referred to the total amount of the
grease composition.
[0036] Traditional friction modifiers such as fatty acid amides and
fatty amine phosphates have been used in greases and other
lubricants for many years (see, e.g., Klamann, Dieter
--"Lubricants", Verlag Chemie GmbH 1983, 1st edition, chapter 9.6).
Their role is to give the lubricant stable but not necessarily low
friction over a wide range of operating conditions.
[0037] In a further preferred embodiment of the present invention,
a grease composition comprises about 55% by weight to about 97.5%
by weight of the base oil composition, especially with a kinematic
viscosity of between about 32 and about 250 mm.sup.2/s at
40.degree. C. and between about 5 and about 25 mm.sup.2/s at
100.degree. C., about 0.3% by weight to about 3% by weight of at
least one tri-nuclear molybdenum compound, about 0.1% by weight to
about 1.5% by weight of at least one zinc compound additive and
about 2% by weight to about 25% by weight of at least one
thickener, in each case referred to the total amount of the grease
composition. Preferably, an urea thickener may be present in a
range between about 5 to about 20% by weight, a lithium soap
thickener between 2 to 15% by weight and a calcium complex soap
thickener between about a to about 25% by weight.
[0038] Further, the grease composition according to the present
invention has a sliding friction coefficient of not more that 0.1,
as measured with a SRV test.
BEST MODE FOR CARRYING OUT THE INVENTION
[0039] In order to determine the effect of the lowering of the
friction coefficient as well as the wear by the grease composition
according to the invention, SRV tests are carried out using an
Optimol Instruments SRV tester. Flat disc lower specimen made of
the 100Cr6 standard bearing steel from Optimol Instruments
Pruftechnik GmbH, Westendstrasse 125, Munich, properly cleaned
using a solvent are prepared and contacted with the grease
composition to be examined. The SRV test is an industry standard
test and is especially relevant for the testing of greases for
CVJs. The test consists of an upper ball specimen with a diameter
of 10 mm made from a 100Cr6 bearing steel reciprocating under load
on the flat disc lower specimen indicated above. In tests for
mimicking tripod joints a frequency of 40 Hz with an applied load
of 200 N were applied for 60 minutes (including running-in) at
80.degree. c. The stroke was 1.5 mm and 3.0 mm, respectively. The
friction coefficients obtained were recorded on computer. For each
grease, the reported value is an average of four data at the end of
tests in four runs (two runs at 1.5 mm stroke and two runs with 3.0
mm stroke). Wear is measured using a profilometer and a digital
planimeter. By using the profilometer, a profile of the cross
section in the middle of the worn surfaces can be obtained. The
area (S) of this cross section can be measured by using the digital
planimeter. The wear quantity is assessed by V=SI, where V is the
volume of the wear and I is the stroke. The wear rate (W.sub.r) is
obtained from W.sub.r=V/L [.mu.m.sup.3/m], where L is the total
sliding distance in the tests. For the running-in, it is started
with an applied load of 50 N for 1 minute under the above-specified
conditions. Afterwards, the applied load is increased for 30
seconds by 50 N up to 200 N.
[0040] The following substances are used in the examined grease
compositions:
Base Oil Composition
[0041] The base oil compositions used have a kinematic viscosity of
between about 32 and about 250 mm.sup.2/s at 40.degree. C. and
between about 5 and about 25 mm.sup.2/s at about 40.degree. C. Two
base oil blends are used in this invention. The base oil blend A is
a mixture of one or more naphthenic oils in a range between about
10 to about 60% by weight, one or more paraffinic oils in a range
between about 30 to about 80% by weight and one or more
polyalpha-olefins (PAO) in a range between about 5 to about 40% by
weight, referred to the total amount of the oil mixture. Oil blend
A does not contain an organic synthetic ester, whereas oil blend B
contains DOS in a range between about 2 to about 10% by weight
referred to a total amount of the oil mixture.
[0042] The naphthenic oils are selected with a range of viscosity
between about 20 to about 180 mm.sup.2/s at 40.degree. C.,
paraffinic oils between about 25 to about 400 mm.sup.2/s at
40.degree. C., and PAO between about 6 and about 40 mm.sup.2/s at
100.degree. C.
Tri-Molecular Molybdenum Compound (TNMoS)
[0043] The tri-molecular molybdenum compound used in the grease
compositions according to the present invention is a
sulphur-containing tri-nuclear molybenium compound obtainable under
the trade name C9455B by Infineum International Ltd., USA. Its
structure is defined in U.S. Pat. No. 6,172,013 B1.
Further Molybdenum Compounds for Comparative Examples
[0044] For comparative examples, a molybdenum dithiophosphate
(MoDTP) sold under the commercial name RC3580 by Rhein Chemie
Rheinau GmbH, Germany, with the chemical formula 2-Ethylhexyl
molybdenum dithiophosphate, diluted with mineral oil, is used.
Further, a molybdenum dithiocarbamate (MODTC) sold under the trade
name Adeka Sakuralube 600 (S-600) in the solid state and Sakuralube
515 (S-515) in the liquid state, produced by Asahi Denka Co.
Limited, Japan, is used. Further organo molybdenum complexes of
organic amides (Organo Mo amide), sold under the trade name Molyvan
855 by R. T. Vanderbilt, USA, as well as one organo molybdenum
complex of an amine (Organo Mo amine) sold under the trade name
Salkuralube 700 (S-700), produced by Asahi Denka Co. Limited,
Japan, are used.
Zinc Compound Additive
[0045] As zinc compound additives, ZnDTP, sold by Infineum
International Ltd., UK, under the trade name Paranox-15 or sold by
Rhein Chemie, Germany, under the trade name RC3038 are used, being
a zinc diallyldithiophosphate with primary and secondary alkyl
groups, preferably diluted with mineral oil, is used. Further,
ZnDTC sold under the trade name Vanlube AZ by R.T. Vanderbilt, USA,
as well as ZnO and ZnS are used as zinc compound additives.
Thickener
[0046] As a lithium soap (Li soap), a reaction product of a fatty
acid, such as stearic or 12-hydroxystearic with lithium hydroxide
monohydrate is used. Further, a calcium complex soap (Calcium
complex soap) being a reaction product of calcium hydroxide with
two carboxylic acids, one with a short carbon chain length of 2 to
5 carbon atoms and one with a long carbon chain length of 16 to 20
carbon atoms, in which the short to long chain ratio is between 1:2
and 1:5 is used.
Additives
[0047] As an anti-oxidant agent (Anti-oxidant), a diphenylamine
with butyl and/or octyl-groups is used, supplied by Ciba Specialty
Chemicals, Switzerland under the trade name L-57 (Irganox L57). As
an EP agent, a sulphurised organic compound (fatty acid
methylester) sold under the trade name DeoAdd MD10 by DOG Deutsche
Oelfabrik, Gesellschaft fur chemische Erzeugnisse mbH und Co,
Hamburg, Germany ("EP additive" in the examples), is used. Another
example of an EP agent is a grease with calcium sulphonate
thickeners, as produced by Brugarolas S.A., Spain, under the trade
name Ca--S Grease (Ca--S grease).
[0048] As a corrosion inhibitor, a calcium salt of
dinonylnaphthalene sulfonate, distributed for example by King
Industries Co. Ltd., Norwalk, Conn., U.S.A. under the trade name
NaSul 729 30 (Ca-sulphonate) is used.
[0049] First, the advantages of the grease composition according to
the invention were examined by comparing the friction coefficient
and wear of the same with other commercial organic molybdenum
containing additives (example A). Six different grease compositions
were produced, as listed in the following Table 1:
TABLE-US-00001 TABLE 1 Grease Composition Example Example Example
Example Example Example [wt %] A1 A2 A3 A4 A5 A6 TNMoS 1.0 MoDTP
1.0 MoDTC (solid) 1.0 Organo Mo amide 2.0 Organo Mo amine 1.0 1.0
ZnDTP 1.0 1.0 1.0 1.0 1.0 1.0 Anti-oxidant 0.25 0.25 0.25 0.25 0.25
0.25 oil blend A 81.75 81.75 81.75 80.75 81.75 82.75 Calcium
complex 16.0 16.0 16.0 16.0 16.0 16.0 soap
[0050] The results from the SRV-measurement of the friction
coefficient and the wear of examples A1 to A6 may be derived from
FIG. 1. Only example A.sup.1 is a grease composition in accordance
with the present invention, whereas examples A2 to A6 contain other
commercial organic molybdenum-containing additives (A2 to A5) or no
molybdenum containing additive (A6). The friction coefficient for
example A1 is clearly decreased when compared to the friction
coefficient of the comparative examples, and is below 0.09.
Further, the wear measured of example A1 is the lowest wear in the
test series among examples A1 to A6, and is about 165
.mu.m.sup.3/m.
[0051] In a further series of tests, further grease compositions in
accordance with the present invention were prepared containing
different concentrations of the tri-nuclear molybdenum compound
containing sulphur (TNMoS), as listed in Table 2.
TABLE-US-00002 TABLE 2 Grease Composition Example Example Example
Example Example Example Example Example [wt %] B1 = A6 B2 B3 B4 =
A1 B5 B6 B7 B8 TNMoS 0.0 0.1 0.2 0.3 0.5 1.0 2.0 3.0 ZnDTP 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 Anti-oxidant 0.25 0.25 0.25 0.25 0.25 0.25
0.25 0.25 oil blend A 82.75 82.65 82.55 82.45 82.25 81.75 80.75
79.75 Calcium 16.0 16.0 16.0 16.0 16.0 16.0 16.0 16.0 complex
soap
[0052] The results from SRV tests with respect to the friction
coefficient and wear will be seen from FIG. 2.
[0053] As may be taken from FIG. 2a, surprisingly, the friction
coefficient of grease compositions B1 to B3 is clearly about 0.1.
Said grease compositions B1 to B3 are not in accordance with the
present invention. One may easily see from FIG. 2a that
concentrations of the sulphur containing tri-nuclear molybdenum
compound of 0.2% by weight or less do not lower the friction
coefficient significantly, whereas the grease composition B4 in
accordance with the present invention shows a friction coefficient
being lowered of at least about 25% when compared to examples B1 to
B3. Thus, in accordance with the present invention only amounts of
the sulphur containing tri-nuclear molybdenum compound of about
0.25% by weight, referred to the total amount of the grease
composition, lead to an advantageously lowered friction coefficient
and lower values for the wear, as will be seen from FIG. 2b.
[0054] In a third test series, the effect of the addition of a zinc
compound additive to the grease composition according to the
present invention was examined by preparing grease compositions in
accordance with Table 3.
TABLE-US-00003 TABLE 3 Grease Composition Example Example Example
Example Example Example [wt %] C1 C2 C3 = B7 C4 C5 C6 TNMoS 2.0 2.0
2.0 2.0 2.0 2.0 ZnDTP 0.5 1.0 ZnDTC 1.0 ZnO 0.20 ZnS 0.20
Anti-oxidant 0.25 0.25 0.25 0.25 0.25 0.25 oil blend A 81.75 81.25
80.75 80.75 81.55 81.55 Calcium complex 16.0 16.0 16.0 16.0 16.0
16.0 soap
[0055] The results from the SRV tests carried out with respect to
examples C1 to C6 are shown in FIG. 3.
[0056] As will be seen when comparing example C1 having no zinc
compound additive with examples C2 to C6, one will see that
especially the wear is significantly lowered (not measurable) when
adding a zinc compound additive to the grease composition according
to the present invention. Further, also the friction coefficients
are lowered and do not exceed the value of 0.08. Especially
preferred is the addition of ZnDTP (C2 and C3) or the addition of
ZnS (C6).
[0057] Further, the effect of adding an EP agent to the grease
composition according to the present invention is demonstrated by
preparing different grease compositions in accordance with Table
4.
TABLE-US-00004 TABLE 4 Grease Composition Example Example Example
Example Example Example Example Example [wt %] D1 D2 D3 D4 D5 D6 D7
D8 TNMoS 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 ZnDTP 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 EP additive 0.1 0.3 0.5 Ca- 2.5 2.0 1.0 sulphonate
Ca--S grease 3.0 Anti-oxidant 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 oil
blend B 91.7 91.6 91.4 91.2 89.2 89.7 90.7 88.7 Li soap 6.0 6.0 6.0
6.0 6.0 6.0 6.0 6.0
[0058] The results of the friction coefficient and wear
measurements will be seen from FIG. 4.
[0059] The friction coefficient is lowered by the addition of the
EP agents, especially by the addition of about 0.4% by weight or
less of the EP agent "EP additive", being a sulphurised organic
compound sold under the trade name DeoAdd M010. Further, the
friction coefficient is also lowered by adding the further
sulphur-containing compounds Ca-sulphonate 1 and 2 (examples D6 to
D8). Also, the wear is lowered especially in the examples D3, D7
and D8. From example D4 one may derive that the addition of 0.5% by
weight EP additive as an EP agent does not lead to a decrease in
the value for the friction coefficient, but also gives higher
values with respect to the wear measured. Thus, the addition of
0.5% by weight or more of EP additive as an EP agent shall be
avoided.
[0060] Finally, the effects of using different thickeners in the
grease composition in accordance with the present invention is
demonstrated by preparing different grease compositions in
accordance with Table 5.
TABLE-US-00005 TABLE 5 Grease composition Example Example Example
Example [wt %] E1 = A1 E2 = A6 E3 = D1 E4 TNMoS 1.0 1.0 ZnDTP 1.0
1.0 1.0 1.0 Anti-oxidant 0.25 0.25 0.3 0.3 oil Blend A 81.75 80.75
oil Blend B 91.7 92.7 Calcium complex 16.0 16.0 soap Li soap 6 6
Urea thickener
[0061] The results of the SRV tests of the friction coefficient and
the wear will be seen from FIG. 5.
[0062] One may easily derive from the friction coefficient
measurements shown in FIG. 5 the advantageous influence of adding a
tri-nuclear molybdenum sulphur-containing compound to a grease
composition in accordance with the present invention according to
examples E1 and E3, when compared to the comparative examples E2
and E4. Further, the addition of a lithium-soap thickener leads to
a decrease of the friction coefficient compared to a grease
composition containing a calcium complex soap.
[0063] In summary, therefore, the grease composition according to
the present invention has an advantageous significant influence on
the friction coefficient and wear, leading to lower wear and lower
friction in CVJ, and prevents the premature initiation of rolling
contact fatigue in the joint.
* * * * *