U.S. patent application number 12/896339 was filed with the patent office on 2011-01-27 for grease composition for use in constant velocity joints.
Invention is credited to Jisheng E, Bernd Falk, Lothar Gasper, Frank Reher, Stefanie Rosenkranz, Mario Witzdam.
Application Number | 20110021391 12/896339 |
Document ID | / |
Family ID | 40369369 |
Filed Date | 2011-01-27 |
United States Patent
Application |
20110021391 |
Kind Code |
A1 |
E; Jisheng ; et al. |
January 27, 2011 |
GREASE COMPOSITION FOR USE IN CONSTANT VELOCITY JOINTS
Abstract
A grease composition which has a good compatibility with boots
made of rubber or thermoplastic elastomer, and which also gives
enhanced endurance, low wear and low friction in use in constant
velocity joints is disclosed. A grease composition is suggested
comprising a) at least one base oil; b) 5% by weight to 40% by
weight of at least one calcium sulphonate soap and/or calcium
sulphonate complex soap as a thickener; and c) at least one
molybdenum containing additive.
Inventors: |
E; Jisheng; (Hennef, DE)
; Reher; Frank; (Siegburg, DE) ; Rosenkranz;
Stefanie; (Wachtberg-Oberbachem, DE) ; Falk;
Bernd; (Frankfurt Am Main, DE) ; Gasper; Lothar;
(Koeln, DE) ; Witzdam; Mario; (Hennef,
DE) |
Correspondence
Address: |
GKN Driveline/TTG
c/o Kristin L. Murphy, 39533 Woodward Avenue, suite 140
Bloomfield Hills
MI
48304
US
|
Family ID: |
40369369 |
Appl. No.: |
12/896339 |
Filed: |
October 1, 2010 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP2008/002579 |
Apr 1, 2008 |
|
|
|
12896339 |
|
|
|
|
Current U.S.
Class: |
508/165 ;
508/154; 508/363 |
Current CPC
Class: |
C10N 2010/12 20130101;
C10N 2040/046 20200501; C10M 2227/09 20130101; C10M 2219/0445
20130101; C10M 169/00 20130101; C10M 2207/282 20130101; C10N
2010/04 20130101; C10M 2223/045 20130101; C10M 2207/2825 20130101;
C10N 2020/02 20130101; C10M 2219/068 20130101; C10N 2030/76
20200501; C10M 169/06 20130101; C10M 2205/0285 20130101; C10M
2201/066 20130101; C10M 2203/1065 20130101; C10M 2203/1025
20130101; C10M 2219/0466 20130101; C10N 2050/10 20130101; C10M
2203/1006 20130101; C10M 2219/068 20130101; C10N 2010/12 20130101;
C10M 2223/045 20130101; C10N 2010/12 20130101; C10M 2227/09
20130101; C10N 2010/12 20130101; C10M 2219/068 20130101; C10N
2010/12 20130101; C10M 2223/045 20130101; C10N 2010/12 20130101;
C10M 2227/09 20130101; C10N 2010/12 20130101 |
Class at
Publication: |
508/165 ;
508/154; 508/363 |
International
Class: |
C10M 169/02 20060101
C10M169/02 |
Claims
1. A grease composition for use in constant velocity joints
comprising: a) at least one base oil; b) 5% by weight to 40% by
weight of at least one calcium sulphonate soap and calcium
sulphonate complex soap as a thickener; and c) at least one
molybdenum containing additive.
2. A grease composition according to claim 1, wherein the
composition comprises 12% by weight to 20% by weight of at least
one calcium sulphonate soap and calcium sulphonate complex
soap.
3. A grease composition according to claim 1 wherein the at least
one molybdenum containing additive is selected from a group
comprising at least one molybdenum dithiocarbamate, at least one
molybdenum dithiophosphate, MoS.sub.2, at least one S-free and
P-free organic molybdenum compound, and at least one trinuclear
molybdenum compound.
4. A grease composition according to claim 1, wherein the
molybdenum containing additive is selected from a group comprising
at least one molybdenum dithiocarbamate and at least one trinuclear
molybdenum compound.
5. A grease composition according to claim 3, wherein the
molybdenum containing additive comprises 0.2 wt.-% to 5 wt.-% of at
least one trinuclear molybdenum compound.
6. A grease composition according to claim 3, wherein the
molybdenum containing additive comprises 0.25 wt.-% to 5 wt.-% of
at least one molybdenum dithiocarbamate.
7. A grease composition according to claim 3 wherein the molybdenum
dithiocarbamate is selected from a group comprising at least one
solid molybdenum dithiocarbamate.
8. A grease composition according to claim 3, wherein the
molybdenum containing additive comprises 0.3 wt.-% to 2.0 wt.-% of
at least one trinuclear molybdenum compound and 0.5 wt.-% to 3
wt.-% of at least one molybdenum dithiocarbamate.
9. A grease composition according to claim 4, wherein the
molybdenum containing additive further comprises at least one
molybdenum dithiophosphate.
10. A grease composition according to claim 1, wherein the base oil
composition comprises at least one of poly-.alpha.-olefins,
naphthenic oils, paraffinic oils, and synthetic organic esters.
11. A grease composition according to claim 1, further comprising
at least one anti-oxidation agent, at least one corrosion
inhibitor, at least one anti-wear-agent, at least one wax, at least
one friction modifier and/or at least one extreme pressure
agent.
12. A grease composition according to claim 1, wherein the
composition comprises 65 wt.-% to 86.9 wt.-% of a base oil
composition, 16 wt.-% to 20 wt.-% of at least one calcium
sulphonate soap and/or calcium sulphonate complex soap, 0.3 wt.-%
to 2.0 wt.-% of at least one trinuclear molybdenum compound and 0.5
wt.-% to 3 wt.-% of at least one molybdenum dithiocarbamate.
13. (canceled)
14. (canceled)
Description
TECHNICAL FIELD
[0001] The present disclosure 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. Further, the present disclosure
relates to a constant velocity joint comprising the grease
composition in accordance with the present disclosure.
BACKGROUND
[0002] 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.
[0003] 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.
[0004] 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).
[0005] 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
plasticizers 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 plasticizers and can cause swelling. The
exchange of plasticizer or plasticizer 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.
[0006] 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 dialkyldithiophosphate 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.
SUMMARY
[0007] A grease composition for use in constant velocity joints is
disclosed. One embodiment of the grease composition comprises:
[0008] a) at least one base oil; [0009] b) 5% by weight to 40% by
weight of at least one calcium sulphonate soap and/or calcium
sulphonate complex soap as a thickener; and [0010] c) at least one
molybdenum containing additive.
[0011] As far as the term % by weight is used with respect to the
components being comprised from the claimed grease composition, the
term % by weight is referred to the total amount of the grease
composition throughout this specification, except where
expressively stated otherwise.
[0012] Preferably, the base oil composition used in the grease
composition in accordance with the present disclosure comprises
poly-.alpha.-olefines, napthenic oils, paraffinic oils, and/or
synthetic organic esters.
[0013] As a base oil composition according to the present
disclosure, a base oil composition as disclosed in U.S. Pat. No.
6,656,890 B1 may preferably be used, the disclosure of which is
incorporated insofar herein by reference. 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 5 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. In
one exemplary embodiment, the aliphatic alcohols have primary,
straight or branched carbon chains with 2 to 20 carbon atoms. In
one exemplary embodiment, the organic synthetic ester is selected
from a group comprising sebacic acid-bis(2-ethylhexylester)
("dioctyl sebacate" (DOS)), adipic acid-bis-(2-ethylhexylester)
("dioctyl adipate" (DOA)), and/or azelaic
acid-bis(2-ethylhexylester) ("dioctyl azelate (DOZ)).
[0014] If poly-.alpha.-olefin is present in the base oil
composition, in one exemplary embodiment poly-.alpha.-olefins are
selected having a viscosity in a range from about 2 to about 40
centistokes at 100.degree. C. The naphthenic oils selected for the
base oil composition have preferably a viscosity in a range between
about 3 to about 370 mm.sup.2/s, more preferably about 20 to about
150 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 9 to about 170 mm.sup.2/s
at 40.degree. C.
[0015] The at least one calcium sulphonate soap and/or calcium
sulphonate complex soap used as a thickener in the grease
composition in accordance with the present disclosure is, in
principle, a reaction product of aliphatic or fatty acids and/or
hydroxy aliphatic and/or fatty acids. In one exemplary arrangement,
the fatty acids or hydroxy fatty acids may be selected from a group
comprising 12 to 30, preferably 12 to 24, and most preferably 12 to
18 carbon atoms. The aliphatic and/or fatty acids may be selected
from a group comprising dodecanoic acid, palmitic acid, stearic
acid, oleic acid, ricinoleic acid and/or 12-hydroxystearic acid.
Hydroxy aliphatic and/or fatty acids may be used due to their
higher thickening properties.
[0016] The calcium sulfonate that may be used in the preparation of
the calcium sulfonate grease and/or the calcium sulfonate complex
grease is selected from the group comprising at least one calcium
sulfonate and/or at least one overbased calcium sulfonate.
Overbased calcium sulfonates may be used in accordance with the
present disclosure, especially overbased calcium sulfonates having
a metal ratio of about 6 to 35.
[0017] A calcium sulfonate soap that may be used as a thickener may
be prepared from the reaction of the aforesaid calcium sulfonate
components and aliphatic and/or fatty acids and/or hydroxy and/or
fatty acids in the presence of other agents, especially converting
agents, comprising, among others, water, alcohols, for instance
biphenol, isobutanol, n-pentanol, or mixtures thereof or mixtures
of alcohols with water, alkylene glycols, monoloweralkyl ethers of
alkylene glycols such as monomethylether of ethylene glycol, lower
aliphatic carboxylic acids, for example acetic acid and propionic
acid, ketones, aldehydes, amines, phosphorus acids, alkyl and
aromatic amines, imidazoilines, alkanolamines, boron acids,
including boric acid, tetraboric acid, metaboric acid, and esters
of such boron acids, and, also, carbon dioxide as such, or better
in combination with water. Calcium sulphonate complex soaps that
may be used as a thickener in accordance with the present invention
may be used prepared from at least one aliphatic and/or fatty acid
or hydroxyaliphatic and/or fatty acid, at least one of the calcium
sulphonate compounds mentioned above 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
a calcium sulphonate complex soap as a thickener in accordance with
the present disclosure allows the grease composition according to
the present disclosure to operate up to a temperature of about
180.degree. C., whereas simple calcium sulphonate soaps that may be
used as a thickener in accordance with the present disclosure, the
grease composition will only operate up to a temperature of about
120.degree. C. However, mixtures of all of the aforesaid soaps may
also be used.
[0018] The at least one molybdenum containing additive that is
present in the grease composition in accordance with the present
disclosure may be selected from a group comprising at least one
molybdenum dithiocarbamate, at least one molybdenum
dithiophosphate, MoS.sub.2, at least one S-free and P-free organic
molybdenum compound, and/or at least one tri-nuclear molybdenum
compound. The at least one tri-nuclear molybdenum compound is of
the following general formula
Mo.sub.3S.sub.kL.sub.nQ.sub.z (I)
wherein L is 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.
[0019] 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 by
reference in the present disclosure in its entirety. In one
embodiment, there is at least 0.25% by weight of the tri-nuclear
molybdenum compound, which significantly lowers the friction
coefficient as well as the wear when used in CVJs.
[0020] The at least one molybdenum dithiophosphate (MoDTP) and/or
molybdenum dithiocarbamate (MoDTC) is preferably present in the
grease composition according to the present disclosure in an amount
in a range between about 0.3% by weight, more preferred about 0.5%
by weight, most preferred about 1.0% by weight, to about 3.5% by
weight, most preferred about 3% by weight, in each case referred to
the total amount of the grease composition. However, also any
further molybdenum containing compound may be present in the grease
composition according to the present disclosure as component c), of
which organic molybdenum compounds are preferred. The grease
composition according to the present disclosure may contain one or
more MoDTC and/or MoDTP, and especially mixtures thereof. The MoDTP
according to the present disclosure is of the following general
formula:
##STR00001##
wherein X or Y represents S or O and each of R.sup.1 to R.sup.4
inclusive may be the same or different and each represents a
primary (straight chain) or secondary (branched chain) alkyl group
having between 6 and 30 carbon atoms.
[0021] The MoDTC according to the present disclosure is of the
following general formula:
[(R.sup.5)(R.sup.6)N--CS--S].sub.2--Mo.sub.2O.sub.mS.sub.n
(III)
wherein R.sup.5 and R.sup.6 each independently represents an alkyl
group having 1 to 24, preferably 3 to 18 carbon atoms; m ranges
from 0 to 3 and n ranges from 4 to 1, provided that m+n=4.
[0022] In one exemplary embodiment, the molybdenum containing
additive is selected from a group comprising at least one
molybdenum dithiocarbamate and at least one tri-nuclear molybdenum
compound. In one exemplary embodiment of the present disclosure the
grease composition comprises 0.2% by weight to 5.0% of at least one
tri-nuclear molybdenum compound, preferably 0.25% by weight to 3%
by weight, most preferably 0.3% by weight to 2% by weight, and much
more preferably 0.3% by weight to 1.25% by weight.
[0023] In another exemplary embodiment, of the present disclosure,
the grease composition comprises 0.25 to 5% by weight of at least
one solid or liquid molybdenum dithiocarbamate, preferably 0.5% by
weight to 3% by weight, most preferably 0.8% by weight to 2% by
weight. In another exemplary embodiment of the present disclosure,
the molybdenum dithiocarbamate is selected from a group comprising
at least one solid molybdenum dithiocarbamate.
[0024] According to a further exemplary embodiment of the present
disclosure, the grease composition further comprises at least one
anti-oxidation agent, at least one corrosion inhibitor, at least
one anti-wear agent, at least one wax, at least one friction
modifier and/or at least one extreme pressure agent.
[0025] As a friction modifier, at least one zinc compound additive,
more preferably a zinc compound additive in an amount of about 0.1%
by weight to about 3.5% by weight, preferably to about 2.5% by
weight, more preferably to about 0.5% by weight to about 2.0% by
weight, referred to the total amount of the grease composition, is
used. In one exemplary arrangement, the zinc compound additive is
selected from the group comprising at least one of zinc
dithiophosphates (ZnDTP) and/or zinc dithiocarbamates (ZnDTC), and
ZnDTPs are most preferred. The zinc dithiophosphate may be selected
from the group of zinc dialkyldithiophosphate of the following
general formula:
(R.sup.7O)(R.sup.8O)SP--S--Zn--S--PS(OR.sup.9XOR.sup.10O) (IV)
wherein each of R.sup.7 to R.sup.10 inclusive may be the same or
different and each represents a primary or secondary alkyl group of
which primary alkyl groups are most preferred having 1 to 24,
preferably 3 to 20, most preferably 3 to 5 carbon atoms. In
particular, excellent effects can be expected if the substituants
R.sup.7, R.sup.8, R.sup.9 and R.sup.10 represent a combination of
primary and secondary alkyl groups, each having 3 to 8 carbon
atoms.
[0026] In one embodiment, the zinc dithiocarbamate may be selected
from zinc dialkyldithiocarbamate of the following general
formula:
##STR00002##
wherein R.sup.11, R.sup.12, R.sup.13, and R.sup.14 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.
[0027] By adding at least one zinc compound additive to the grease
composition according to the disclosure, the friction coefficient
as well as the wear in CVJ are diminished further
significantly.
[0028] In one exemplary arrangement, the EP agent is a metal-free
polysulfide or a mixture thereof, e.g. sulphurised fatty acid
methyl ester agents, 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, preferably 0.3 to about 2% by weight,
referred to the total amount of the grease composition. The total
inactive sulphur amount of the EP agent at room temperature
preferably ranges from about 8 to about 50% by weight, preferably
to about 45% by weight. The active sulphur amount as measured in
accordance with ASTM D1662 may be about up to 1% by weight,
preferably up to about 8% by weight at 100.degree. C., and
preferably up to about 20% by weight at 140.degree. C., the weight
percent being referred to the amount of the EP agent itself. Such
EP agents exhibit excellent effects with respect to the prevention
of scuffing of contacting CVJ internal components. 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 and may lead to degradation of the CVJ boot
material.
[0029] As an anti-oxidation agent, the grease composition of the
present disclosure may comprise an amine, preferably an aromatic
amine, more preferably phenyl-.alpha.-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
disclosure 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 composition, as well as to lengthen the life of the
grease composition, thus prolonging the life of the CVJ.
[0030] 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 affecting
the performance of the CVJ, thus a corrosion inhibitor is required.
As a corrosion inhibitor, the grease composition according to the
present disclosure may comprise at least one metal or dimetal salt
selected from the group comprising 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, quaternary
ammonium salts, the calcium salts being most preferred. Calcium
salts of oxidised waxes also ensure an excellent effect. Especially
preferred is disodium sebacate as corrosion inhibitor.
[0031] Anti-wear agents according to the present disclosure 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
anti-corrosion agents according to the present disclosure
preferably calcium sulphonate salts are used, preferably an amount
between about 0.5 to about 3% by weight, referred to the total
amount of the grease composition.
[0032] As a wax compound, the grease composition of the present
disclosure may comprise any kind of waxes, preferably oiliness
waxes, known in the state of the art to be used in grease
composition or mixtures thereof, of which montan waxes, especially
ester montan waxes being a reaction product of at least one acid
montan wax with an ester, and polyolefin waxes including micronized
montan and/or polyolefin waxes, or mixtures thereof are most
preferred. Montan waxes in the sense of the present disclosure
preferably comprises esters of C.sub.22-C.sub.34-fatty acids and
probably wax alcohols having 24 to 28 carbon atoms. Esters may be
present in the montan wax in accordance with the present disclosure
in an amount in a range of about 35% by weight to about 70% by
weight. Further, free fatty acids as well as free wax alcohols as
well as montan resins may be present. Useful montan waxes are
offered for example by the company Clariant GmbH, 86005 Augsburg,
Germany, especially montan waxes offered and sold under the trade
name "Licowax". Usable polefin waxes in the sense of the present
disclosure are especially polypropylene and/or polyethylene waxes
or mixtures thereof, also including modified polyolefin waxes,
obtained especially by copolymerization of ethylene with useful
co-monomers like vinyl esters or acrylic acid. In one exemplary
embodiment, the wax has a viscosity of at least about 50 mPa*s at
100.degree. C., more preferred of at least about 100 mPa*s at
100.degree. C., and most preferred of at least about 200 mPa*s at
100.degree. C., measured in accordance with DIN 53 018. The wax
used in the grease composition may be supplied as a powder or
flakes, and is added to the grease composition with a long perod of
stirring, preferably at elevated temperatures, especially at
temperatures about 80.degree. C. to about 100.degree. C.
[0033] Traditional friction modifiers that may also be used in the
present disclosure such as fatty acid amides and fatty amine
phosphates have been used in greases and other lubricants for many
years (see, e.g., the modifiers disclosed in Klamann,
Dieter--"Lubricants", Verlag Chemie GmbH 1983, 1.sup.st edition,
chapter 9.6). Their role is to give the lubricant stable but not
necessarily low friction over a wide range of operating
conditions.
[0034] In a further embodiment of the present disclosure, the
grease composition claimed comprises 0.3 wt.-% to 2 wt.-%,
preferably to 1.25 wt.-%, of at least one trinuclear molybdenum
compound and 0.8 wt.-% to 3 wt.-%, preferably to 2 wt.-%, of at
least one molybdenum dithiocarbamate.
[0035] In a further embodiment of the present disclosure, the
grease composition claimed comprises 65 wt.-% to 86.9 wt.-% of a
base oil composition, 16 wt.-% to 20 wt.-% of at least one calcium
sulphonate soap and/or calcium sulphonate complex soap, 0.3 wt.-%
to 2 wt.-% of at least one trinuclear molybdenum compound and 0.3
wt.-% to 3 wt.-% of at least one molybdenum dithiocarbamate. Most
preferred the grease composition according to the present
disclosure comprises 16 wt.-% to 20 wt.-% of at least one calcium
sulphonate soap and/or calcium sulphonate complex soap, 0.3 wt.-%
to 0.7 wt.-% of at least a tri-nuclear molybdenum compound, 0.75
wt.-% to 1.8 wt.-% of at least one molybdenum diothiocarbamate, and
66.45 wt.-% to 86.9 wt.-% of a base oil composition. The grease
composition claimed may further comprise other agents as mentioned
above.
[0036] Further, the present disclosure refers to the use of a
grease composition in accordance with the present disclosure in
constant velocity joints, and, further, to a constant velocity
joint comprising a grease composition as claimed. The constant
velocity joint especially encompasses a boot, the boot being filled
with the grease composition in accordance with the present
disclosure, at least in part, the boot having a first attachment
region which is assigned to a joint, and a second attachment region
which is assigned to a shaft. The boot may be fixed with usual
clamp devices on the joint and/or shaft.
[0037] The disclosure will be explained in more detail in the
following examples.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] FIG. 1 is a chart illustrating results of SRV measurements
of the friction coefficient for grease examples A1-A8 listed in
Table 1.
[0039] FIG. 2 is a chart illustrating results of SRV measurements
of the welding load (wear) for grease examples A1-A8 listed in
Table 1.
[0040] FIG. 3 is a chart illustrating results of SRV measurements
of the friction coefficient for grease examples B1-B10 listed in
Table 2.
[0041] FIG. 4 is a chart illustrating results of SRV measurements
of the welding load (wear) for grease examples B1-B10 listed in
Table 2.
[0042] FIG. 5 is a chart illustrating results of SRV measurements
of the friction coefficient for grease examples C1-C6 listed in
Table 3.
[0043] FIG. 6 is a chart illustrating result of SRV measurements of
the welding load (wear) for grease examples C1-C6 listed in Table
3.
[0044] FIG. 7 is a chart illustrating results of SRV measurements
of the friction coefficient for grease examples D1-D5 listed in
Table 4.
[0045] FIG. 8 is a chart illustrating results of SRV measurements
of the welding load (wear) for grease examples D1-D5 listed in
Table 4.
DETAILED DESCRIPTION
Examples
[0046] 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 disclosure, SRV tests are carried out using an
Optimol Instruments SRV tester. Flat disc lower specimens made of
the 100Cr6 standard bearing steel from Optimol Instruments
Pruflechnik 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 the
CVJ. The test includes an upper ball specimen with a diameter of 10
mm made from 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 500 N
were applied for 60 minutes (including running-in) at 80.degree. C.
The stroke was 3.0 mm. The friction coefficients obtained were
recorded on computer. For each grease, the reported value is an
average of two data at the end of tests in two runs. 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 (WO 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 500
N.
[0047] Further, tests regarding the properties of a rubber boot and
a TPE-boot, respectively, equipped with a grease composition in
accordance with the present disclosure according to example C4
compared with two commercial grease compositions A and B were
carried out with respect to the change of a hardness (shore D) and
the percentage change of tensile, elongation, and volume before and
after a heat ageing of the boot material immersed in a grease at
125.degree. C. for 336 hours. Said values are measured in
accordance with ISO 868 (shore D), ISO 37 (tensile change and
elongation change), and ISO 2781 (volume change).
[0048] The commercial greases used in comparative examples A and B
are Axel CaSX 51646, obtained from Axel Christiernsson B. V.,
Heijningen, Netherlands, (comparative example A) and Super Grease 2
obtained from Tianjin Lubricant and Grease Co. Ltd. (Jinzhi),
Sinopec Corp., Tianjin, P. R. China (comparative example B).
[0049] The following substances are used in the examined grease
compositions in accordance to the present disclosure.
Base Oil Composition (Oil Blend)
[0050] The base oil composition used has a kinematic viscosity of
about 165 mm.sup.2/s at 40.degree. C. and about 16 mm.sup.2/s at
100.degree. C. The base oil blend may be a mixture of one or more
paraffinic oils in a range between about 10 to about 60% by weight,
preferably about 20 to 40% by weight, one or more naphthenic oils
in a range between about 30 to about 80% by weight, preferably
about 55 to about 80% by weight, and, if necessary, one or more
poly-.alpha.-olefins (PAO) in a range between about 5 to about 40%
by weight, referred to the total amount of the oil mixture. The oil
blend may further contain DOS in a range between about 2 to about
10% by weight, referred to a total amount of the oil mixture. The
concrete oil blend used in the examples is made of 73% by weight of
naphthenic oil SR130, produced by AB Nyna's Petroleum, Stockholm,
Sweden, 25% by weight of paraffine oil NS650, obtained by Kuwait
Petroleum Europoort B. V, Europoort, Netherlands, and 2% by weight
of DOS.
[0051] 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.
Calcium Sulphonate Soap
[0052] The calcium sulphonate soap used in the examples of the
present disclosure is an overbased calcium sulphonate soap obtained
from a reaction of overbased calcium sulphonate with a metal ratio
of about 6 to 35 with 12-hydroxystearic acid in the presence of a
solvent neutral oil, calcium carbonate, isopropyl alcohol and
phosphoric acid. A possible method for producing the calcium
sulphonate soap used is described in U.S. Pat. No. 5,126,062.
Tri-Molecular Molybdenum Compound (TNMoS)
[0053] The tri-molecular molybdenum compound used in the grease
compositions according to the present disclosure is a
sulphur-containing tri-nuclear molybdenum compound obtainable under
the trade name C9455B by lnfineum International Ltd., UK. Its
structure is defined in U.S. Pat. No. 6,172,013 B1.
Further Molybdenum Compounds
[0054] A molybdenum dithophosphate (MoDTP) sold under the
commercial name Sakuralube 300 (S-300) by Asahi Denka Co. Ltd.,
Japan, with the chemical formula 2-Ethylhexyl molybdenum
dithiophosphate, diluted with mineral oil, is used. Further, a
solid molybdenum dithiocarbamate (MoDTC solid) sold under the trade
name Sakuralube 600 (S-600), produced by Asahi Denka Co. Limited,
Japan, or under the trade name Molyvan A, produced by R. T.
Vanderbilt Company, Inc, USA, is used.
[0055] Further, a molybdenum dithiocarbamate sold under the trade
name Sakuralube 200 (MoDTC S-200) in the liquid state, produced by
Asahi Denka Co. Limited, Japan, is used, as well as a S-free and
P-free organic molybdenum additive sold under the trade name S-701
by Asahi Denka Co. Limited, Japan, being a molybdenum amine complex
with the general formula R.sub.2N--Mo.sub.xOyH, as well as usual
MoS.sub.2.
Further Additives
[0056] As a friction modifier a zinc compound additive, namely zinc
dithiophosphate ZnDTP, sold by lnfineum International Ltd.,
Oxfordshire, UK.sub.1 under the trade name C9425, is used, being a
zinc dialkyldithiophosphate with primary and/or secondary alkyl
groups, especially having 3 to 8 C-atoms, preferably having 4 to 5
C-atoms, diluted with mineral oil.
[0057] First, the advantages of the grease composition according to
the present disclosure were examined by measuring the friction
coefficient and the welding load of the six different greases, as
listed in Table 1:
TABLE-US-00001 TABLE 1 Grease Composition Example Example Example
Example Example Example Example Example [wt %] A1 A2 A3 A4 A5 A6 A7
A8 TNMoS -- -- -- -- 0.5 -- -- -- ZnDTP -- -- -- -- -- -- -- 0.5
MoDTP -- -- 0.5 -- -- -- -- -- MoDTC solid -- -- -- 0.5 -- -- -- --
MoDTC S-200 -- 0.5 -- -- -- -- -- -- S-710 -- -- -- -- -- 0.5 -- --
MoS.sub.2 -- -- -- -- -- -- 0.5 -- Calcium 18 18 18 18 18 18 18 18
sulphonate soap oil blend 82 81.5 81.5 81.5 81.5 81.5 81.5 81.5
[0058] The results from the SRV-measurements of the friction
coefficient as well as the welding load measurements of Examples A1
to A8 may be derived from FIG. 1. and FIG. 2. The lowest friction
coefficient, and, however, the highest wear is measured when adding
a simple MoS.sub.2, whereas a very low wear as measured with
respect to Example A3 with an increased friction coefficient
compared with Example A1 being a grease composition not in
accordance with the present disclosure only composed of the base
oil and a calcium sulphonate soap. Further, also Examples A2 and A5
show good results with respect to the wear.
[0059] In a further series of tests, the amount of the TNMoS as
well as of the MoDTC solid is amended. Ten grease compositions were
prepared in accordance with Table 2.
TABLE-US-00002 TABLE 2 Grease Example Example Composition Example
B2 = Example B4 = Example Example Example Example Example Example
[wt %] B1 A5 B3 A4 B5 B6 B7 B8 B9 B10 TNMoS 0.3 0.5 1.0 -- -- -- --
0.5 0.5 0.5 MoDTC solid -- -- -- 0.5 1 1.5 2 1 1.5 2 Calcium 18 18
18 18 18 18 18 18 18 18 sulphonate soap oil blend 81.7 81.5 81.0
81.5 81 80.5 80 80.5 80 79.5
[0060] In Examples B1 to B3 the amount of the TNMoS is amended,
wherein in Examples B4 to B7 the amount of MoDTC solid is amended.
Examples B8 to B10 refer to mixtures of 0.5 wt.-% TNMoS to
different amounts of MoDTC solid. The results from the SRV
measurements with respect to the friction coefficient as well as
the welding load may be derived from FIG. 3 and FIG. 4.
[0061] Example B3 shows the lowest friction coefficient, however,
the results for the wear are only in the midrange of the results
obtained. Further, low friction coefficients were measured with
respect to Examples 139 to 1310, of which Example 139 shows one of
the lowest wear measured. Said test results show that especially
combinations of different molybdenum containing compounds are
preferable, and that the ranges of the molybdenum compounds used
are very sensitive with respect to the friction coefficient and
wear measured.
[0062] In a third test series, the effect of addition of an amount
of 0.5 wt.-% of different molybdenum containing compounds and ZnDTP
to the amount of 1.5 wt.-% MoDTC solid is studied. The grease
compositions C1 to C6 examined are defined in Table 3.
TABLE-US-00003 TABLE 3 Grease Composition Example Example Example
Example Example Example [wt %] C1 = A1 C2 = A2 C3 C4 = B9 C5 C6
TNMoS -- -- -- 0.5 -- -- ZnDTP -- -- -- -- 0.5 -- MoDTP -- -- 0.5
-- -- -- MoDTC solid -- 1.5 1.5 1.5 1.5 1.5 MoDTC S-200 -- 0.5 --
-- -- -- MoS.sub.2 -- -- -- -- -- 0.5 Calcium sulphonate 18 18 18
18 18 18 soap oil blend 82 80 80 80 80 80
[0063] The results from the SRV measurements of the friction
coefficient as well as the measurement of the welding load may be
derived from FIGS. 5 and 6. One may easily derive that composition
C4 being a composition of 1.5 wt.-% of MoDTC solid in the solid
state and the tri-nuclear molybdenum compound in an amount of 0.5
wt.-% is most preferred, because both the friction coefficient as
well as the wear are considerably lower when compared to the
results of the other compositions.
[0064] Finally, combinations of three molybdenum compound additives
or two molybdenum compound additives together with ZnDTP are
examined in accordance with Table 4. The amount of MoDTC solid is
not varied.
TABLE-US-00004 TABLE 4 Grease Composition Example Example Example
Example Example [wt %] D1 = A1 D2 D3 D4 D5 TNMoS -- -- -- 0.5 0.5
ZnDTP -- 0.5 0.5 0.5 -- MoDTC -- 1.5 1.5 1.5 1.5 solid MoDTC -- 0.5
-- -- -- S-200 MoDTP -- -- 0.5 -- 0.5 Calcium 18 18 18 18 18
sulphonate soap Oil blend 82 79.5 79.5 79.5 79.5
[0065] As may be derived from FIGS. 7 and 8 referring to examples
D1 to D5, the lowest friction coefficient was measured with respect
to example D5, whereas the wear was very low in examples D2 and D4.
However, due to the lowest friction coefficient, grease composition
D5 being very similar to grease composition C4 appears to be
advantageous.
[0066] Finally, measurements of the properties of boots equipped
with the different greases were carried out. A grease composition
in accordance with example C4 was compared with comparative
examples A and B being commercially available grease compositions.
The results are listed in Table 5.
TABLE-US-00005 TABLE 5 Example Comparative Comparative C4 Example A
Example B compatibility with rubber Hardness change (shore D A) -9
+1 0 Tensile change (%) -4.5 -5.4 -2.3 Elongation change (%) -17.7
-17.9 -17.6 Volume change (%) +8.9 -3.0 -2.8 compatibility with TPE
Hardness change (shore D A) -6 -7 -5 Tensile change (%) -40.4 -63.9
-11.7 Elongation change (%) -16.5 -72.4 +1.3 Volume change (%)
+12.9 +10.0 +9.2
[0067] As may be derived from Table 5, especially in combination
with boots made of TPE-material preferable properties with respect
to the tensile change and elongation change were measured,
Endurance tests carried out with respect to example C4 show that
the endurance of constant velocity joints may be enhanced up to a
twofold lifetime compared to joints equipped with boots with
commercially available greases such as comparative examples A and
B.
[0068] In summary, the grease composition in accordance with the
present disclosure has an advantageous and significant influence on
the friction coefficient and the wear, leading to a good extreme
pressure performance. Especially preferred are combinations of two
or three different molybdenum containing compounds being added to
the grease composition in an amount up to 3.5 weight % in total, of
which the addition of a tri-nuclear molybdenum compound as well as
a molybdenum dithiocarbamate, preferably in the solid state, in
combination are most preferred.
* * * * *