Note: Descriptions are shown in the official language in which they were submitted.
WO91/13~5 ~ CT/E~1/~07
2077.~ ., 5
LUBRICATI~G GREASE COMPOSITIO~
This invention relates to a lubricating grease
composition and, more especially, to grease compositions
thickened wit~ lithium soap.
Lithium soap greases are well known and are used in the
lubrication of many automotive and industrial applications,
for example ~earings, gears and couplings. Whilst lithium
soap greases, and particularly lithium soap complex greases,
are often favoured for higher temperature applications, the
greases have the disadvantage that they have a limited
lifetime at temperatures exceeding about 120C as the oil
tends to separate ("bleed") from the grease, and thus
fre~uent reapplication of the grease is required.
The present invention provides a lithium complex grease
with prolonged lifetime at high temperatures. More
specifically the invention provides a lu~ricating grease
composition comprising a major proportion of a lubricating
base oil, a thickening amount of a lithium soap complex and
an effective amount of an organic metal compound wherein the
metal is selected from molybdenum, tungsten, vanadium,
niobium and tantalum.
The grease according to the invention has the advantage
that it has a significantly improved lifetime at high
temperatures, the improvement being particularly evident at
temperatures between about 120 and 160C. The grease has a
lowe~ tendency to bleed oil compared with other lithium
soap-containing greases. Thus by e~ploying the grease, the
number of reapplications necessary to maintain satisfactory
lubrication of the mechanical part to which the grease is
applied can be considerably reduced. In some instances,
where the mechanical part is enclosed in a sealed container,
the grease can provi~e ~lifetime" lubrication, i.e. it need
not be renewed for t~e lifetime of the mechanical part.
WO91/1395; PCT/E~l/~07
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Examples of such applicati~ns include automotiveantifriction bearings and sliding bearings.
The amount of lithium soap complex present in the
grease is preferably from 2 to 30 wt %, preferably 5 to 20
wt % based on the total ~eight of the composition. It is
preferred that the lithium complex soap comprises a lithium
soap of a C12 to C24 hydroxy fatty acid and at least one
other lithium compound. This other lithium compound is
advantageously either a lithium soap of a C2 to C12
aliphatic dicarboxylic acid or a lithium salt of boric acid,
or a mixture of both.
More preferably the lithium soap of the hydroxy fatty
acid is a C16 to C20 hydroxy fatty acid. A particularly
preferred hydroxy fatty acid is hydroxystearic acid, for
example 9-hydroxy-, 10-hydroxy-, or 12-hydroxysteari~ acid,
more preferably the latter. Ricinoleic acid, which is an
unsaturated form of 12-hydroxystearic acid having a double
bond in the 9-10 position, can also be used. Other suitable
hydroxy fatty acids include 12-hydroxybehenic acid and
lO-hydroxypalmitic acid.
Where the other lithium-containing compound is an
aliphatic dicarboxylic acid, the proportion of dicarboxylic
acid to hydroxy fatty acid employed is generally a weight
ratio of between 0.05 and l, usually between 0.1 and 0.8,
parts dicarboxylic acid per part hydroxy fatty acid. The
dicarboxylic acid is preferably a C4 to Cl2, more preferably
C6 to Clo, aliphatic dicarboxylic acid. Examples of
suitable acids include oxalic, malonic, succinic, qlutaric,
adipic, suberic, pimelic, azelaic, dodecanedioic and sebacic
acids. Azelaic and sebacic acids are especially preferred.
WO91/1~955 PCT/E~1/00407
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Where the other lithium-containing compound is the
lithium salt of boric acid, t~e proportion of ~ydroxy fatty
acid to boric acid employed is generally a weight ratio of
between 3 and l00 parts, usually between S and 80 parts,
hydroxy fatty acid per part boric acid.
The lithium soap complex may also include a second
hydroxycarboxylic acid. This generally has 3 to 14 carbon
atoms and an -OH group not more than 6 carbon at atoms away
from the carboxyl group. This acid can be either an
aliphatic acid such as lactic acid, 6-hydroxydecanoic acid,
3-hydroxybutanoic acid, l-hydroxycaproic acid,
4-hydroxybutanoic acid, 6-hydroxy-alpha-hydroxystearic acid,
etc. or an aromatic acid such as parahydroxy-benzoic acid,
salicylic acid, 2-hydroxy-4-hexylbenzoic acid,
metahydrorybenzoic acid, 2,5-dihydroxybenzoic acid (gentisic
acid); 2,6-dihydroxybenzoic acid (gamma resorcyclic acid);
4-hydroxy-4-methoxybenzoic acid, etc. or a hydroxyaromatic
aliphatic acid such as orthohydroxyphenyl,
metahydroryphenyl, or parahydroxyphenyl acetic acid. A
cycloaliphatic hydroxy acid such as hydroxycyclopentyl
carboxylic acid or hydroxynaphthenic acid could also be
used. Particularly useful hydroxy acids are lactic acid,
salicylic acid, and parahydroxybenzoic acid.
Alternatively a lower alkyl ester, usually, a C1 to C4
alkyl ester of the above second hydroxycarboxylic acid can
be used instead of the free acid. This is especially
benericial when boric acid is employed as the ester aids
dispersion of the insoluble salt. As example of a preferred
ester is nethyl salicylate. When a second hydroxycarboxylic
acid is employed in the grease composition, the proportion
is generally a weight ratio of 0.1 to 10 parts, usually 0.5
to S parts, second ~ydroxycar~oxylic acid per part of the
acid co~ponent of the said other lithium-containing
compound, for example boric acid.
WO 91/13955 PCl/EP91/00407
.,.
The metal of the organic metal compound is preferably
molybdenuz. The organic component of this compound is
preferably a thiocarbamate or xanthate. Thus preferred
organic metal compounds are molybdenum thiocarbamate and
molybdenu~ xanthate compounds. Molybdenum
dialXyldithiocarbamate and molybdenum oxysulphide
dialkyldithiocarbamate.
The preferred amount of the organic metal compound
present in the grease composition is from 0.1 to 10 wt ~,
more preferably 0.5 to 5 wt %, based on the total weight of
the composition. ~he organic metal compound acts as an
antiwear agent and prolongs the high temperature lifetime of
the grease.
In a preferred embodiment, the grease according to the
invention also contains an antioxidant, which is generally
present in an amount from 0.1 to 5 wt %, preferably 0.5 to 3
wt %, based on the total weight of the composition. The
antioxidant employed is preferably an amine based
antioxidant compound, an example being alXyldiphenylamine.
The lubricating base oil employed in the grease
composition can be any of the conventionally used
lubricating oils and is preferably a mineral oil or a blend
of mineral and synthetic oils. In general these lubricating
oils have a viscosity in the range of 35 to 300 SUS at
210F, and a viscosity index in the range of 30 to 170,
preferably 30 to 140. Mineral lubricating oil base stocks
used in preparing the greases can be any conventionally
refined base stocks derived from paraffinic, naphthenic and
mixed base crudes. Synthetic lubricating oils that can be
used include esters of dibasic acids, such as a
di-2-ethylhexyl sebacate, esters of glycols such as C13 oxo
WO 91t13955 PCI/EP91/00407
- S - 2~77,-i''''.~'
acid diester or tetraethylene glycol, or complex esters such
as one formed from l mole of sebacic acid and 2 moles of
tetraethylene glycol and 2 moles of 2-ethylhexanoic acid.
Other synthetic oils that can be used include synthetic
hydrocarbons such as alkyl benzenes, e.g. alkylate bottoms
from the alXylation of benzene with tetrapropylene, or the
polymers and copolymers of alpha olefins; silicone oils,
e.g. ethyl phenyl polysiloxanes, methyl polysiloxanes, etc.;
polyglycol oils, e.g. those obtained by condensing butyl
alcohol ~ith propylene oxide; carbonate esters, e.g. the
product of reacting Cg oxo alcohol with ethylcarbonate to
form a half es~er followed by reaction of the latter with
tetraethylene glycol, etc. Other suitable synthetic oils
include the polyphenyl ethers, e.g. those having from about
3 to 7 ether linkages and about 4 to 8 phenyl groups (see US
Patent 3,424,678, column 3).
The grease according to the invention also has the
advantage that the usual benefits associated with lit~ium
complex greases may be retained, together with the
additional benefit of prolonged lifetime at high
temperatures. Usual benefits associated with lithium soap
greases include good water resistance, high dropping point,
and good mechanical and chemical stability. The grease
according to the invention can also be employed in low
temperature, as well as high temperature, applications.
The in~ention will ~ow be illustrated by the following
Examples. All the greases of these Examples were made to a
consistency of N~GI grade 2, i.e. all the greases have a
60-stroke vork penetration at 25C of 265-295, as determined
by ASTM ~ethod D21~ or D2665.
W09l/13955 PCT/E~1/~07
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6 -
; '
Examples 1-4
Examples 1-3 demonstrate grease composition according
to the invention based on lithium complexes comprising a
lithium soap of a hydroxy fatty acid and a lithium soap of
an aliphatic discarboxylic acid. Example 4 is comparative,
using the same lithium soap complex.
The test results of Examples 1-4 are given collectively
in Table 1.
Exam~le 1
A lithium complex grease was formulated with the
following components:
Commonent Wt %
Paraffinic base oil 80.5%
(V40-l5omm2/s~ VI_g5)1
Lithium hydroxide monohydrate 2.5
12-Hydroxystearic acid 11.0
Azelaic acid 2.0
Molybdenum oxysulphide
dialkyldithiocarbamate2 2.S
Alkydiphenylamine3 1.5
(1) V40 ~ viscosity at 40C, VI = Viscosity Index
~2) Supplied as Sakuralube 600 from Asahi Denka
Rogyo KK.
(3) Supplied as Irganox L57 from Ciby-Geigy Limited.
WO91/13955 PCT/E~l/0~07
2Q77,;'~
- 7
The base oil and lit~ium soap complex components were
formulated as described in Example 1 of GB Patent 1,384,904.
The molybdenum oxysulphide dialkyldithiocarbamate (MDDC) and
the alkyldiphenylamine additives were then added to the
grease, and the grease was milled using a conventional
grease mill.
The lifetime of the grease at high temperature ~as
measured according to the standard test DIN 51821 T2
A/1500/6000. In this test a set of five bearings is run
under specified conditions of temperature, load and spee~.
When the required driving momentum becomes too high due to
lubricant starvation, the alternator shuts down
automatically. Five lubricant lifetimes are thereby
obtained and the following data is calculated:
Flo which represents the time after which the first ten
percent of the bearings are starved of lubricant; an~
Fso which represents the time after which fifty percen, of
the bearings are starved of lubricant.
A grease ~hich has an Fso value of at least 100 hours at a
given temperature is regarded as a lifetime lubricant at
that temperature.
The results of the test are given in Table 1 below.
~x~mple 2
A grease composition was formulated as in Example 1
except that ~DDC employed was supplied as Molyvan A from
Vanderbilt Company Inc.
The grease was tested as described in Example 1 and the
results are given in Table 1 below.
WO 91/1395~ j PCT/E~1/~07
~ 8
ExamDle 3
A grease composition was formulated as in Example 1
except that the alkyldiphenylamine was omitted and the
amount of ~DDC increased to 3 wt %. The balance was made up
by increasing the amount of base oil to 81.5 wt %.
The grease was tested as described in Example 1 and the
results are given in Table 1 below.
Exam~le 4
The greases of Examples 1-3 were compared with a
conventional lithium complex soap grease. This grease
contained the same base oil and lithium complex as the above
Examples, but contained no molybdenum compound nor
alkyldiph~nylamine.
This comparative grease was tested as described in
Example 1 and the results are given in Table 1 below.
Table 1
Grease Composition Lifetime Flo/Fso (hrs)
Example No. 140C 150C 1600C
390/410
2 84/111
3 125/166
4 66/72
(Co~par~tive)
WO91/13955 PCT/E~1/~7
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2!J77;?,~
The results show that grease compositions according to
the invention have significantly longer lifetime than
zomparative greases using t~e same base oil and lithium
complex. For example, at 140C Grease l has a lifetime over
five times as great as comparative Grease 4.
Exam~les 5 & 6
These two examples demonstrate a qrease according to
the invention based on a lithium complex comprising a
lithium soap of a hydroxy fatty acid and the lithium salt of
boric acid, and compare this grease with a conventional
grease containing the same lithium soap complex. The
results are given collectively in Table 2.
ExamDle 5
A grease composition was formulated with the following
components:
ComDonent Wt
Paraffinic base oil 78.3
(v4o_llOmm2/s~ VI_95)1
Lithium hydroxide monohydrate3,5
l2 - Hydroxystearic acid ll.0
Boric acid 0.9
Methylsalicylate 2.3
MDDC2 2.5
Alkydiphenylamine3 l.5
WO91/13955 PCT/EW1/~07
(l) V40 = viscosity at 40C, VI = Viscosity Index
(2) Supplied as Sakuralube 600 from Asahi Denka
Kogyo KR.
(3) Supplied as Irganox L57 from Ciby-Geigy Limited.
The base oil and lithium soap complex components were
formulated as described in Example 2 of US Patent 3,758,497.
The MDDC and alkyldiphenylamine additives were then added,
and the grease was milled using a conventional grease mill.
The grease was tested as described in Example l and the
results are given in Table 2 below.
Exammle 6
A conventional lithium complex grease containing the
same lithium soap complex as the grease of Example 5, but
omitting the MDDC and alkyldiphenylamine was tested as
described in Example l, for comparative purposes. The
results are given in Table 2 below.
Table 2
Grease Composition Lifetime Flo/Fso (hrs) at 160C
Example No.
62/143
6 65/86
(Co:parative)
WO 91/13955 PCI`/EP91/00407
These results show that, although the Flo lifetime at
160C are comparable at approximately 60 hours, the Fso
lifetime of Grease 5, a grease according to the invention,
is 1.7 ti~es greater than the Fso lifetime of comparative
Grease 6.
ExamDle 7
A grease composition was formulated as in Example 2
except that the paraffinic base oil was replaced with a base
oil blend of 28.5 wt %, based on the total grease
composition, of a poly-alpha-olefin (V40_48mm2/s, Vloo -
7.9mm2/s) and 52 wt ~, based on the total grease
composition, of a paraffinic oil base (V4o-llomm2/s~ V10O_
12mm 2/s). The blended base oil yielded the following
viscosities:
V40_80 mm2/s, V10o-lo.3mm2/s~ VI_lll.
The grease was tested as described in Example 1 at
160C. The Flo result was 101 hours and the Fso result was
134 hours. Thus this grease also demonstrated long lifetime
at high temperature.
